How to determine tire pressure for fat bike tires?- Mtbr.com
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  1. #1
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    Tire pressure for a fat guy

    Quick question I see that the tire pressure for the fat tire bikes are much lower than traditional size mountain bike tires. Do these tires still get hard like nearly rock hard? I ask because I am very heavy and need to make sure the tires can hold me. Thanks in advance?

  2. #2
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    With the right tire and rim combo, you'll likely be able to find something that will be accommodate your weight, and still provide the benefits of lower pressure. Riding rock hard tires won't be necessary, or even recommended.
    Jason
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  3. #3
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    Not able to get anything high end. Considering a cheap bike directs fat bike. Unless that's a bad idea

  4. #4
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    How big of a guy are ya? I push 260 right now and for daily commuting run about 18 psi and when riding trail or soft conditions anywhere down to sub 6 psi. As a bigger guy your not going to want to go much lower than that regardless of what you hear around here. Also, going more than 20 psi is just silly on a fb. If you're using a floor pump you might just lose a few pounds for how much work it'll take you to get to 20. I think Surly tires rate out max 35 psi and the vee rubbers at 25 or 30. Those pressures in a fb are like 65 in a regular MTB tire. The tires will hold you just fine. You might not be a good candidate for carbon though...

  5. #5
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    I am at the high end of the 300's about 385 (varies) on my 26" wheel bile I was able to run 60ish and be good

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    You'll be fine!

  7. #7
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    Basically, you just want a little bulge in the tires. You are probably looking for 20lbs or there abouts to start.

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    Thanks for the replies

  9. #9
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    I weigh in around 250. My bike has 100mm rims with 4.8" tires. I run 9 psi in the rear and 8 in the front in most conditions.
    The bigger the tire and rim, the less pressure you'll need. You won't need as much as you think.
    I like turtles

  10. #10
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    I would recommend a fatbike at your weight.I'm 330# riding these wonderful machines.On the snow 8psi is great with the stock snow shoe tires.First bike in years that was comfortable to ride because of the low pressure tires.Just can't get the smile off my face and the wife is pissed I'm having fun while loosing weight.

  11. #11
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    i weigh 315 & run about 15lbs. You'll be fine on a fatbike.
    2014 TREK FUEL EX8 29er
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    I am a 260lb Clydesdale On my Farley I run about 8psi in snow and around 12psi on concrete and am happy with that
    '11 Specialized Crux Pink SS
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  13. #13
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    Lets do some math.
    Tire contact patch size is basically weight(lb)/pressure(lb per square inch)
    So at 20psi and 400 (bike+rider) your total contact patch is about 20 in^2.
    Since about 65% or you weight is on the rear tire you would need about 13 in^2 on the rear tire with is slightly bigger than 3"x4". Since the tires are 4"-5" wide they are not even spreading out across their full width. So basically you would see a little squat with the rim still better than 3" off the road.
    Since the tires are usually rated to 30 psi there is plenty of margin.
    And I am going to recommend that you try pressures much lower than 20psi unless you are only riding on the roads. The ride comfort, handling and traction will increase if you find a nice "squatty' pressure to run at.

    Craig

  14. #14
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    I like my tires between the consistency of squeaky cheese and dood boobs. Rock hard is too firm.
    Bars and psi is a lot of science and I prefer to cop a feel of my tires before a ride.
    ptarmigan hardcore

  15. #15
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    If you're going bikes direct I would highly recommend one of the steel ones at your weight, but then be prepared to buy a new rear hub, or set some money aside for it. The reason I say that is a friend of mine who is in the upper 200's got one and the freehub went out pretty quick. The bikes direct bikes are fine, but realize the individual (often overlooked) components usually are low end. But otherwise he beats the heck out of that bike and it takes it.

  16. #16
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    I really appreciate all the help

  17. #17
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    My 300 lb buddy regularly runs 5 psi on his fat boy in softer snow. Did blow through a lot of hubs til he switched to I9s

  18. #18
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    How to determine tire pressure for fat bike tires?-image.jpgTire Squash:

    As I ride my fatbike in nearly 100% sand and found it a tough go in some types of sand I decided to play around with the air pressure. I'm currently running 4 psi in the back and 3.5 psi in the front. This gives the back a bit more squash and I was interested in just what that means and the consequence of it.

    I did a static loaded test to get a sense of the foot print. My H-Billies are 4.2, they squash with my 198 pounds and 31 pounds of bike (at the current air pressure above) to 4" wide (outside knobs) and 9" long (to the end of each taper of the squashed tire). What does this all mean?

    After fiddling around with a weight bias of 60% back 40% front and studying the squash print I concluded that I'm at a total of 60 square inches and almost equally split front to back. The rear loading works out to ~4.5 pounds per square inch and the front is ~ 3.0 pounds per square inch. What does that mean? I can ride on almost any winter dune area and soft sand area pretty easily (easy is a relative term). This is ground that would be difficult for nearly any another tire to roll over without digging in and giving enormous resistance. It only takes an inch or two of sinking into the ground before you'll notice. When I was at 8 psi air pressure back and 6 psi air pressure front, it was real work to pedal the softer sand areas.

    The beach does have one area at low tide that is very hard and smooth and a 3/4 ton truck will barely compress the sand and same true for a fat tire. There I could run at 10 psi quite handily but the minute I turn up the beach and enter the softer areas, the more difficult it becomes. The penalty one pays for switching to a paved trail is enormous, like trying to drive a tractor with low ground pressure tires, great at low speeds on farm roads, but once you hit the highway, it just takes more energy and bounces the crap out of you.

    The physical energy needed to pedal through soft sand is pretty enormous but I find that I can ascend the 15% dune slopes quite handily if I pick a traverse line and keep the weight back. The squashed tire has excellent traction. When I crest a dune and go down it the bike takes right off down the slope, pretty amazing.

    I eventually settled on 5.25 rear and 3.5 front as I'm probably more biased to the rear in terms of weight distribution. That's still pretty low ground pressure and there aren't many places I can't ride though I'm speed limited to about 8 mph on hard sand and 12 mph on a paved trail. On really soft sand (a slog walking)...about 4.5-5 mph. On dry sand I'm traction limited on slopes approaching 15% and I've found it difficult to ride dry sand side slopes above 10%.

    My take is that fat bikes are unique terrain bikes; Principally snow, sand, soft turf, plowed/disced/harrowed fields (depending on soils), playa lakes, salt pans, and etc. I've used ag equipment (Google Rolligon and study THAT LGP stuff!) that had lower pressure, but then I couldn't carry it out when I got stuck). An MIA1 Abrahams tank is rated at about 15 psi ground pressure (but then again, they've got 1000 horsepower).

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  19. #19
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    Whoa. You took it too far.
    ...Be careful what you're looking at because it might be looking back...

  20. #20
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    Quote Originally Posted by duggus View Post
    Whoa. You took it too far.
    Wait till I borrow the wife's scales to measure the F:R weight distribution! 👹

  21. #21
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    Quote Originally Posted by motorider View Post
    I am at the high end of the 300's about 385 (varies) on my 26" wheel bile I was able to run 60ish and be good
    I think the only problem you will have with any fatbike is the rear hub. When you're heavy you'll have to gear down a lot on hills, which combined with the huge wheel you'll be generating amazing amounts of torque.

    I was 315 at one time, and I literally tore a Hope hub in half when cranking up a steep hill in my lowest gear, and that's an even bigger risk with a fat bike because of the traction.

    If you end up trashing the hubs in a short amount of time, look at DT Swiss - they are known for being bomb-proof at a very reasonable price. Industry 9 are also bomb-proof, but they are high-end, blingy, and IMO you should only get those if you think cycling is for you in the long term.

  22. #22
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    tire pressure

    Hello,

    I'm new to fat tire biking, just bought a trek farley 6 and have plans to enter a race next weekend (for fun ; It will be mostly on XC ski trails and should be well groomed, there will also be some single track. Given the forecast for the upper midwest next weekend it could be a little interesting.

    I've done a little research regarding tire pressure, any suggestions? From what I can tell I should run maybe 7-10 psi? I'm 5'8" and about 160 lbs.


    The race is in upper michigan; Hopefully the night time temps will drop below freezing in the days prior to the race; Otherwise all bets are off


    Thanks in Advance!

  23. #23
    bigger than you.
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    for snow, 7 or lower, for dirt, a little higher. Ultimately, any recommendations anyone might give you will be highly subjective. You will need to play with pressures to determine what works best for you.

  24. #24
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    Just ask them what they would recommend when you get there, thems good peeps up there and they will know the conditions better than anyone aye.

  25. #25
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    I'm new too, but based on my limited experience I'd be looking at somewhere around 5 or 6 psi for the conditions you describe. Maybe even a little lower...

  26. #26
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    Thanks for the quick replies!

  27. #27
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    I'm 160# suited up for beach riding. I've been finding out how just a small pressure variation in the front tire (I'm running Halo Nanuks) affects flotation and steering in soft sand. Anything over 6 lbs in the front and it has too round a profile and doesn't float or steer as well as it does at less than 5.5 lbs. Right on 5 lbs is where I like my F with the Nanuk...just about right for all-round beach riding here. It was flattening even better at 4.5 lbs, but I thought the sidewalls were wrinkling too much at below 4 lbs.

    I like my R Nanuk at about 6.5- 6.75 lbs, since there's more weight on it. At 6.5 lbs, it bulges out and flattens to similar profile of the F tire at 5 lbs.
    These lower pressures allow the tire to bulge and flatten out, which helps steering and flotation in soft sand or pea gravel.

    I like 'em each inflated about a pound or so higher for my packed sandy/loamy trails in the woods, to firm 'em up a bit. The front steers better with a rounder profile on the trails than it does on the beach. I like to have 'em at just above sidewall wrinkling pressures on the trails. YMMV

  28. #28
    All fat, all the time.
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    Get there early and go squeeze the other riders tires

  29. #29
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    How to determine tire pressure for fat bike tires?

    Sure, there are lots of threads about fat bike tire pressure. I have read some of them and still have questions. Tire pressure questions come up from time to time, so I am not the only one who needs some answers. Tire pressure seems to be one of the most important factors in fat bikes because as little as a pound or two can make a big difference in traction and ride quality. And here is no sticky thread for that!

    Question: How to determine what pressure to put in their fat bike tires?

    There are a lot of variables in the tire pressure equation. This thread could address these variables and break down the mystery of fat bike tire pressure!

    Some of the variables in the tire pressure equation are:
    • Make and model of tire. Example: Surly Nate have different characteristics than Surly Endomorph
    • Size of tire. Example: A 3.8 versus a 4.0, or 4.7
    • Size of rim. Example: A 100 mm rim vs a 68 mm rim gives a different contact patch, and different pressure can be used.
    • Tubes or Tubeless. Example: I understand tubeless tires can go lower without worry of pinch flat.
    • Terrain: What tire pressure are best for pavement, dirt, packed snow trail, fluffy snow, or sand? More or less pressure in what situations and WHY?
    • Tread pattern: Side knobs or chevron, or blocks in the center.
    • Threads Per Inch (TPI): More threads in the tire means less rubber 27 TPI, vs 60 TPI, vs 120 TPI. Would you put more or less pressure in based on TPI?
    • Outside temperature: More or less tire pressure when it is several degrees below zero.
    • Rider weight: Different pressure for the big guys vs the skinny guys. How much and when?


    I kept track of my tire pressure for each of my fat bike rides this season. But the problem is every ride had different snow conditions, and outside temperature. It was really hard for me to determine the tire pressure for each ride. My tires and rims stayed the same so I guess that is fewer variables for me to figure.

    Please add variables if any are missing. Ideally someone could write one post to share their knowledge and experience on one set of variables. That way someone who is interested in getting a wider rim could skip to that post to see how it would change the pressure. But I know this forum will do what ever they want. Someone droppe a lot of science on contact patch in another pressure thread that would be good to have all the tire pressure details in one place.

    If this thread gets enough information, it would be a great thread to stick it to the top of the forum.

  30. #30
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    The simple answer is: if you are bouncing all over the place or sinking into whatever you are riding on let air out. If you are having rim strikes or super wrinkles in the sidewalls put air in. Beyond this if the thread generates tons of responses and data sets of information is that really going to help when you are out riding and the temperature or surface changes? Just ride and you will get a feel for close enough.
    Latitude 61

  31. #31
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    I fully agree. You have a laid out a very thought provoking equation for which to fully maximize the efficiency of perhaps the most important variable when it comes to the incredibly serious prospect of riding your bike. I think your quandaries require a little more thought however because after a few simple calculations, I feel there must be more variables (simple physics dictates this) factoring into this essential calculation. Whatever you do, do not ride your bike until all these factors have been fully run through your preferred modeling program. Perhaps the most important variable to ponder....

    - feather density.....of the duster to dust your bike off while it sits around collecting dust while you overanal-ize the variables of tire pressure while your bike collects dust. Determining the rate of dust build up will directly influence the density and gauge of the feathers needed to best dust off your bike once all modeling programs have run to completetion. You may not see the correlation now, but given enough time, the weight of dust on your tires will (or could, depending upon a whole other set of variables some of which your methodical mind has identified) adversely effect tire pressure.

    Good luck in your endeavors!! I'm sure once someone with more experience chimes in adds to the variable list, inserts science graphs correlating p-values with r-values integrated with MANOVAs cross referenced with a regression of chi-squares these nachos are da' bomb.

  32. #32
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    Ask 10 Fat cyclists about air pressure and you'll get 27 different answers.

  33. #33
    All fat, all the time.
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    Yep.... I had the same question when I first got my Fatbike.
    Squeeze your with fingers, Ride, adjust as needed, remember for next time.
    Enjoy.

  34. #34
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    Finger test seems to work fine. After three or so rides I always hit about the right pressure. Also, I suck. So I know that if I had perfect pressure one of my much more skilled friends would still kick my butt if they had 2x the pressure needed.

  35. #35
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    Simply put?

    All the variables you list, make it effectively impossible to have "the answer".

    So, I'd fall back on the info provided by the others above, and boil it down to this.

    Toss a bit of pressure in before the ride, so as to start at what seems to be your normal higher end for the current seasons riding, then, when in doubt, let it out.

    Basically, if you're running more than ~10/12 psi, you either should be on a road bike, or a skinny MTB....
    This is a Pugs not some carbon wannabee pretzel wagon!!

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  36. #36
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    Squeeze-n-ride!

  37. #37
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    Squeeze and ride for me too.

    I rarely ever use my digital gauge anymore. I just go by feel, and the trail conditions.

    Every ride is different.
    Hightower
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  38. #38
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    I play around with my pressures on various surfaces, and then when it seems right for the surface on which I am rolling, I will check it with my gage, so that I will have a number in my head. And I do squeeze my tires so that I can get a feel for the various pressures.

    I agree that it is easier to start out with the pressures at the higher end, and then let some air out in gradual increments until everything feels right.

  39. #39
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    I also just do a little squeeze to make sure I wont smash a rim. Then I bring a frame pump with me. Sure it takes a lot of pumping and probably looks like I am pleasuring myself to bypassers trying to air up that fat tire, but I can usually get it where I want in the first mile easy. Its always different based on the location and trail surface condition, so a gauge and set number is meaningless to me.

  40. #40
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    Quote Originally Posted by Bruzer View Post
    I kept track of my tire pressure for each of my fat bike rides this season. But the problem is every ride had different snow conditions, and outside temperature. It was really hard for me to determine the tire pressure for each ride.
    Determining the pressure is easy, stick a gauge on it. Making an educated estimate of what you should start out at is the difficult part and the angle of this thread.

    Hopefully in your list of pressures you noted amount and condition of snow, temperatures, sun exposure and trail pack conditions. You can geek out over this all you want but in practice it is still an estimate.

    Briefly for my last ride:
    25-35deg sunny, 10" fresh wet snow, unconsolidated/loose over hardpack base. 4psi

    Did it work good? Hell no! but I was out of the house riding (hiking) for almost 2 hrs.

    Quote Originally Posted by MendonCycleSmith View Post
    Simply put?

    All the variables you list, make it effectively impossible to have "the answer".
    Surely a mathematician could put together an equation for us that would take 60min to solve. Or you could set of with 10psi for a few minutes to see how it's going. Not good? Why not try 8? *pssst*.....*psst*....*pst* Another 5 minutes, how's that going?
    Seat of the pants engineering!

  41. #41
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    Quote Originally Posted by MendonCycleSmith View Post
    Simply put?

    All the variables you list, make it effectively impossible to have "the answer".

    So, I'd fall back on the info provided by the others above, and boil it down to this.

    Toss a bit of pressure in before the ride, so as to start at what seems to be your normal higher end for the current seasons riding, then, when in doubt, let it out.

    Basically, if you're running more than ~10/12 psi, you either should be on a road bike, or a skinny MTB....
    Not quite. Might be a fun semester project for a college student in a statistics course that requires a semester project. :-) Could probably get enough data points to come up with a regression equation which would be THE ANSWER (that everyone would promptly ignore).

  42. #42
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    Bah! You guys are a bunch of cynics. I figured there would be a few people willing to wax poetic about their favorite tire pressure calculation method for different variables (conditions). This squeeze method seems pretty subjective and not related to the variables.

    I had specific problems predicting what was a good pressure for the snow rides that I went on this year. I tried the same pressure in different snow conditons and one was awesome another was a horrible ride.

    I think a lot of us have these questions and wanted to try to lay them out for discussion.

  43. #43
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    Quote Originally Posted by Bruzer View Post
    Bah! You guys are a bunch of cynics. I figured there would be a few people willing to wax poetic about their favorite tire pressure calculation method for different variables (conditions). This squeeze method seems pretty subjective and not related to the variables.
    We have rolled this though the coals at everything from 1 to 20psi. Bottom line, there is no sure fire way all the variables can align for every person, snow and component combination.

    We could not quantify it when there was one bike, one tire and one rim choice. There is no way to do it now.

    I'm an engineer and like my data as much as the next bike dork. I've got a pressure gauge and used it often the first few months. After that you learn the feel of the tire/bike/snow and how they are interacting. Now I only throw the gauge on the tire after a ride for S&G if it looks/feels way out of bounds.

    Let me be clear, sometimes there is no right answer and the ride sucks. You attempt to make the best of it but it still sucks. Your bike is the same but you try it again tomorrow anyway because the conditions have changed.

  44. #44
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    Quote Originally Posted by bme107 View Post
    We have rolled this though the coals at everything from 1 to 20psi. Bottom line, there is no sure fire way all the variables can align for every person, snow and component combination.

    We could not quantify it when there was one bike, one tire and one rim choice. There is no way to do it now.
    Let me be clear, sometimes there is no right answer and the ride sucks. You attempt to make the best of it but it still sucks. Your bike is the same but you try it again tomorrow anyway because the conditions have changed.


    yup, couldn't agree more.

  45. #45
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    Quote Originally Posted by Bruzer View Post
    ...I had specific problems predicting what was a good pressure for the snow rides that I went on this year. I tried the same pressure in different snow conditons and one was awesome another was a horrible ride...
    "Snow" is an infinitely variable medium. Snow conditions can change in a matter of minutes due to temperature, sun, shade, wind, etc. Run your tires at 5 to 10 psi (squeezable) and if your traction is lacking, let air out. If you're getting rim strikes on rocks or dragging on firm terrain, put air in.

    End of my input to this thread.

  46. #46
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    Quote Originally Posted by Bruzer View Post
    Bah! You guys are a bunch of cynics.
    I had specific problems predicting what was a good pressure for the snow rides that I went on this year. I tried the same pressure in different snow conditons and one was awesome another was a horrible ride.
    There may be cynics amongst us, but these aren't cynical responses, (well, mostly).

    Just tried and true methodology.

    Air up a touch, and let it out as needed, and bring a pump.

    Trying to predict pressure before riding, is tantamount to predicting the effect the sun, wind, temps, other trail users, etc, had on the entire trail in a given day. This is a variable beyond measurement due to shade, leeward sections, snowmobile versus snowshoer versus booted walker with a pack of hyper spastic dogs, etc, no calculation is going to get you "there", any, or even most of the time.

    A pump, and a slightly too firm tire is the way of the fat biker, no bones about it.
    This is a Pugs not some carbon wannabee pretzel wagon!!

    - FrostyStruthers



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  47. #47
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    Quote Originally Posted by Bruzer View Post
    Bah! You guys are a bunch of cynics. I figured there would be a few people willing to wax poetic about their favorite tire pressure calculation method for different variables (conditions). This squeeze method seems pretty subjective and not related to the variables.
    For riding on anything non-snow, I have a pretty consistent method: "As low as possible without the self steer effect being annoying", and then a little firmer on the rear tire. For the "all rounder" tires I've used (larry, hudu, hodag), that seems to get me the best all around trail performance. With Nates or something with more bite, this method might not work so well

  48. #48
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    IMHO, nothing is more true than "feeling" the ride. It's the best feedback you'll ever get to suit your personal preference and style. Keep a pressure gauge for reference.

    There's just too much variables involve in the field. My tires, for instance, I use Bud front and rear. One is 1500g the other is 1580, one is looser on the same rim. Another owner has 1625g.

    Go ride.
    d butt u kicked today, could b d same butt you'll kiss tomorrow.....

  49. #49
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    Tire durometer is one aspect most people don't consider. I realized it back when Surly released it's last version on the Endomorph. My 2007 Wildfire came with some mighty thin rubber/high durometer tires. I later purchased a 120tpi with softer thicker rubber and noticed the difference in traction, therefore not requiring less air pressure to gain more traction. I still have those old Endomorphs, I studded them with screws. The center knobs are still on them, they never wore off much. They are pretty fast on snow and ice, but illegal to use in races.

  50. #50
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    42f with some clouds. Went with 6 1/4 psi rear and 6 3/4 psi front.Tubed. I'm running Lou/Lou on the ICT and just went out on some hard pack trails. Traction was good on flats not so great going up a steep little hill. Doable 2 days ago with firmer trails.
    The trails were a little soft but ok. I feel as though I could drop another 1-2 psi and climb the little hill no problem. I'll report back later.

  51. #51
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    Stupid air pressure question

    So, these low air pressures on these here fat bikes...

    My floor pump doesn't really read well until maybe 13 or 14 psi, and elven then it's a guesstimate until 20 or so... I have a pretty nice Serfas floor pump, but it's designed for "normal" pressures... like 20 up through 120 for the mountain and road-ish bike.

    Are you guys pumping up and then using a crazy sensitive gauge to see where you're really at? Or are you guessing when you say things like "I run 9.234 psi out back and 7.4 up front."

    Or do you just do the 'squish test' and adjust as you feel it's needed (this is me).

    ...just trying to adapt to fatbike ownership
    Thanks
    You have no excuse for driving to work
    (unless you don't have studded tires)
    (no excuse for that either)

  52. #52
    bigger than you.
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    I either use a low-pressure gauge or a seat-of-the-pants gauge...

  53. #53
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    You titled this thread correctly

    It's basically a monthly question so if you search you will find a boat load of info. Lots of low PSI gauges everywhere. Menards, Walmart, Home Depot, etc etc.

  54. #54
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    I normally start at 8 up front and 10 in the back. floor pump it high and use a low pressure gauge (0-20 psi, about $4 on amazon) to get it where I want, and adjust it on the trail. With snow, I'd ride out 5 minutes. If I wanted to adjust pressure higher, I'd ride back to my car. Otherwise, I'd just lower it as I rode. Every ride is different.

  55. #55
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    Quote Originally Posted by watts888 View Post
    I normally start at 8 up front and 10 in the back. floor pump it high and use a low pressure gauge (0-20 psi, about $4 on amazon) to get it where I want, and adjust it on the trail. With snow, I'd ride out 5 minutes. If I wanted to adjust pressure higher, I'd ride back to my car. Otherwise, I'd just lower it as I rode. Every ride is different.

    yup. what he said.

  56. #56
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    Quote Originally Posted by duggus View Post
    You titled this thread correctly

    It's basically a WEEKLY question so if you search you will find a boat load of info.
    fixed.

    For example, 3 days ago:

    http://forums.mtbr.com/fat-bikes/how...es-957031.html
    Mike
    Toronto, Canada
    2017 Trek Farley 9.6
    2017 Diamondback Haanjo Trail Carbon
    2016 Scott Solace 10 Disc

  57. #57
    All fat, all the time.
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    Stupid air pressure = 15psi.
    OK air pressure = 9 psi.
    Amazing air pressure (trust me) = 9.259872 psi

    Carry on

  58. #58
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  59. #59

  60. #60
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    Most farm stores stock a 0-20psi gauge. Mine was 3 bucks and has a line every half pound. Wouldn't work well for Presta, though.

  61. #61
    Bedwards Of The West
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    See the problem is, just asking the question and putting up with being ridiculed for it while getting great answers and resources is so much easier than actually searching. That took me, what, like 10 seconds? Come back later, skip the reminders that I'm an idiot, and bam...There's my answer.

    Sorry guys, my searches weren't turning up those threads...even from 3 days ago.

    ...and now I know. Ride on. I will set to 9.259872 and adjust from there.
    You have no excuse for driving to work
    (unless you don't have studded tires)
    (no excuse for that either)

  62. #62
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    yes

  63. #63
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    another air pressure question

  64. #64
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    Squish... ahhh... ride. Don't over think this. Do get a good trail pump and plan on using it. There's no magical tire pressure, only what works for specific, and often ever changing, conditions. For instance, on a two hour ride yesterday, I adjusted tire pressure four times as the "trail" went from traffic packed, to sugar snow, to soft drifts, to concrete crust in 12 miles. Maintaining an efficient tire pressure was a bit of a challenge at minus 20F since stopping meant getting cold. Also attaching a pump at those temps risks breaking off the presta threaded doohickie since metals start getting a little brittle. Happened once, and it sucks.

    My personal system for choosing proper tire pressure:
    1. Consider the condition of the trail you plan to ride the last time you rode it.
    2. Consider weather events since the last ride, estimate additional traffic from other users since ride, and factor in current air temperature. 3. Say a little prayer and set tire pressure to proper squish factor (PSF). I always air on the side of too much pressure (PSF + 2), since it's easier to let air out than pump it in.
    4. Ride to the trail head. 100 yards into ride let air out to match actual conditions (usually PSF - 2 ). Err on the soft side if from experience you know that the trail typically gets softer up ahead, or on the hard side if you expect the trail to firm up.
    5. Ride until forward progress stops or you are off the bike more than on. Drop pressure to PSF -3 to -6. Basically whatever it takes to move forward without riding on the rim.
    6. Should you be fortunate enough to have the trail firm up, ride until you feel your bulging, creased tires holding you back, and air up accordingly to PSF or above.

    As a rough guide, PSF feels something like a breast with a silicone implant. PSF - 6 feels like my 58 year old flabby arse. PSF + 6 feels like my man parts when I get in a great ride on snow without having to stop and adjust tire pressure.

    There, I think that covers it.
    Last edited by veloborealis; 03-14-2015 at 08:29 AM.
    Veni vidi velo!

  65. #65
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    "It's only when you stand over it, you know, when you physically stand over the bike, that then you say 'hey, I don't have much stand over height', you know"-T. Ellsworth

    You're turning black metallic.

  66. #66
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    What PSI for the weekend?

    Have a race, if that helps.
    "It's only when you stand over it, you know, when you physically stand over the bike, that then you say 'hey, I don't have much stand over height', you know"-T. Ellsworth

    You're turning black metallic.

  67. #67
    Not the fake Jay Leno
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    Helium is where it's at.

    I use Helium at 1 psi. You've heard about float, you ain't tried nothin until you've tried something with an atomic mass of 4!

  68. #68
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    Need mohr info. Humidity, elevation, temperature, average estimated speed, rider weight, cloudy or sunlight, wind speed and direction....and a few more I forget....

  69. #69
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    Quote Originally Posted by Jayem View Post
    Have a race, if that helps.
    I never go less than 35 for a race. Even higher if I'm on my 65mm carbon wheels.

  70. #70
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    Quote Originally Posted by ADKMTNBIKER View Post
    another air pressure question

    But this one has scientific data in the answer!!
    I like turtles

  71. #71
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    Depends on what type of cable ferrules you're running.

  72. #72
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    Monday through Friday, I run 9 psi rear, 8 psi front.

    Saturday and Sunday, I like to get a little crazy. (Not really sure where to go with this. I couldn't resist the weekend question.)
    I like turtles

  73. #73
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    What phase is the moon and what's your astrological sign?

  74. #74
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    Quote Originally Posted by Chinman View Post
    I use Helium at 1 psi. You've heard about float, you ain't tried nothin until you've tried something with an atomic mass of 4!
    Pfffft! All the cool kids are running hydrogen. Twice as nice as helium. Just stay away from open flames. That Hindenburg thing was a fluke. .....

  75. #75
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    Quote Originally Posted by not2shabby View Post
    That Hindenburg thing was a fluke. .....
    That happened in my neighborhood. My eyebrows are still singed from it, and I wasn't even born yet!

  76. #76
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    Quote Originally Posted by SmooveP View Post
    That happened in my neighborhood. My eyebrows are still singed from it, and I wasn't even born yet!
    It was pilot error. I read the report.

  77. #77
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    Quote Originally Posted by not2shabby View Post
    Need mohr info. Humidity, elevation, temperature, average estimated speed, rider weight, cloudy or sunlight, wind speed and direction....and a few more I forget....
    For riding on snow, or snow on ice, and variations, you can end up varying the pressure to maximize the grip or minimize the drag, depending on the temp of the snow and how sticky (humid) it is. So most of those do come in play for winter riding, or you can look at the end result: snow temp & how sticky for you with your tires. If you want optimum, you will be adjusting for, or even during, every ride. And on steeper terrain, some use a lower pressure for ascents and a somewhat higher pressure for decents.

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