29er vs. 26er tire pressures for technical trails (more?)- Mtbr.com
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  1. #1
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    29er vs. 26er tire pressures for technical trails (more?)

    I am a little confused and need some help! My friend and I began mountain biking mid-summer. Myself on a 29er HT and her on a 26er HT. Been having a blast (used to bike years ago, its amazing how some stuff comes back quick) but have some questions about optimum tire pressures for our respective bikes when on techy trails with lots of rocks, roots, slippery off camber ledges etc. We ride in Northeast PA, prefer Moon Lake and Lackawanna State Park.

    Usually we have been riding with 40lbs front and rear (I think that got started when we had done some rails to trails in MD) This past weekend, I took both bikes to 35 lbs and noticed an improvement. Near the end of the day, we decided to try 30lbs and that was a huge improvement in grip and performance. Rider weights are me at 230lbs and her at 100 lbs. We plan on hitting the trails this weekend at 30lbs but now I am wondering how far we could take this.

    How much lower could we go and what are the key differences between the 29er and 26er tires? Right now, I am running RaceKings and she has an OEM Specialized 2.0s (moto type tread). I am assuming that she (being far lighter) could go with a lighter tire pressure but what would be the lower limits? I know this is long but it is confusing to me, especially with the differences in rider weights and also the 29er vs. 26er tire size.Thanks!

  2. #2
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    Quote Originally Posted by nepanite
    I am a little confused and need some help! My friend and I began mountain biking mid-summer. Myself on a 29er HT and her on a 26er HT. Been having a blast (used to bike years ago, its amazing how some stuff comes back quick) but have some questions about optimum tire pressures for our respective bikes when on techy trails with lots of rocks, roots, slippery off camber ledges etc. We ride in Northeast PA, prefer Moon Lake and Lackawanna State Park.

    Usually we have been riding with 40lbs front and rear (I think that got started when we had done some rails to trails in MD) This past weekend, I took both bikes to 35 lbs and noticed an improvement. Near the end of the day, we decided to try 30lbs and that was a huge improvement in grip and performance. Rider weights are me at 230lbs and her at 100 lbs. We plan on hitting the trails this weekend at 30lbs but now I am wondering how far we could take this.

    How much lower could we go and what are the key differences between the 29er and 26er tires? Right now, I am running RaceKings and she has an OEM Specialized 2.0s (moto type tread). I am assuming that she (being far lighter) could go with a lighter tire pressure but what would be the lower limits? I know this is long but it is confusing to me, especially with the differences in rider weights and also the 29er vs. 26er tire size.Thanks!
    If the pressure is too high, you will get a rough ride and be bouncing all over the trail. That saps energy and is not a lot of fun. So you have or are discovering the process of finding a more ideal tire pressure. The numbers can be different for each rider, width of rim, specific tire, using tubes, not using tubes, 29"er, 26"er, etc... .

    If you are using tubes, then your lower limits will bring up the reality of pinch flats in your tubes if you go too low. Where that number is all depends. I found and still find I can run lower psi's in my 29"er tires than my 26"ers. But I've also switched to tubeless which allows me even lower pressures in the low to mid 20's. One also can run into tire squirm if you start to get too low in the air pressure. That's not really any fun or productive, so if you feel that your tires are "squirming" while on the bike and riding - you've taken the pressure a bit too low and need to add a bit more in for a stable tire.

    At your weight and if using tubes, you already found that 30 feels good. That's probably getting very close to the low end for your weight - unless you are running super wide rims which might allow you to drop down a bit more. If tubeless, you could go a bit lower into the high 20's - or even lower on the wider rims. Your gal at 100 lbs and on a 26"er is probably safe to test out a bit lower than 30, but I would do it one psi at a time. Again, watch for tire squirm and pinch flats as your guide. Many of us find we may run 2 or so psi more in the rear tire than on the front.

    If traction is good and the ride is supple, you've probably found the ideal psi for that tire on those rims in those conditions. If you find yourself with tire squirm - air up a bit. If you find yourself bouncing around, skidding while braking, breaking loose in traction on climbs all the time - let some air out. 32 psi may be perfect for one rider with a specific tire/rim combo when you factor in their weight and trail conditions. Another rider may find 23 psi to be perfect using the same equipment. That's why it is hard to say "this is the psi you should be running".

    But your experimenting is the way to go to dial it in.

    BB

  3. #3
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    You will quickly find that there is no optimal tire pressure. You can also mess around with front and rear pressures. I have found that 30 psi rear and 27 front is great for me. Anything less in the rear and I get a bit of squirm out of the rear, anything more and I give up traction. Riding a rigid and tubeless, 27psi in the front works well for me. I'm around 190 with all my gear but am also running tubeless so your mileage may vary.

    Try out a few different pressures, then start messing with the front and rear. If you start to get pinch flats, or tire squirm, then you will know it is to low. If you don't know exactly what tire squirm is, then you haven't hit the lowest pressure yet. Just make sure you carry a pump (and tubes) with you when your testing out new tire pressures. Particularly if you intend on visiting the lower end of the spectrum.

    Your girl can probably go with much less pressure then you. I haven't noticed a tremendous difference between 29er and 26er tire pressures to answer that question. Both need to be tested under different conditions to fine to what works for you.

  4. #4
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    for a different perspective, i run higher pressures. 40 psi is my normal pressure for bigger tires in the summer. often, i'll run the back tire, and tires under 2.3" in general at 45+ psi. i'm right around 200 lbs.

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    Just my opinion, but at 230lbs, if I were you, I would stay around 30-35psi range and not much lower. Her at 100lbs can get away with 25-30psi, but I would stay at 30psi. Personally, I weigh 190 and run F/R of 32/35 occaisionally up to 38/40 for certain terrain.

    As others have said, experiment and go from there. A lot has to do with the way you ride and bash into rocks/roots.

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    Although your pump will give you a similar reading other pumps could be out by +/-5 psi easy which makes pressure setup psi's kinda useless sadly.

    Modern tyres go Squirmy at low pressures or while leaning over the sidewalls just collapse for that about to crash sinking feeling, rather than pinch flats ( I've only had 1 on mates bike with really low psi and 2.1 tyres I'm 90lb's heavier than him )

    More needed in the rear to keep it rolling faster for sure though.

  7. #7
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    While there may not be a magic number at least I have an idea with my new 29er Been awhile since I hit the dirt so this is a useful thread to get some range to play with...

  8. #8
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    Quote Originally Posted by sean salach
    for a different perspective, i run higher pressures. 40 psi is my normal pressure for bigger tires in the summer. often, i'll run the back tire, and tires under 2.3" in general at 45+ psi. i'm right around 200 lbs.
    That's the way most of my friends run their tubes around here too. I road mine lower for a while, but dislike bottoming out my tires on my rims/am cheap (I don't want to dent my rims!), so I've started running them higher. I used to find a big difference in performance but now as long as there's a little give in them, it doesn't seem to make a big difference. Maybe I've become a smoother rider? I guess stranger things have happened. I can notice when my tire hits a big rock the difference in PSI, but I don't find my traction changes much with a fuller tube.

    I agree with another poster, it's all relative, as most gauges are probably quite off.

  9. #9
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    I used to run mine soft and actually feel the rim knocks but never a pinch or a dented rim so all fine, these days hard only anything else and it just squirms around.

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    So, the WTB stouts will have to wait a while...

    Just want to say thanks for the replies. If the weather holds out, we will continue the experiment this weekend. Interesting points about the pressure gauges possibly being off. I can actually at least verify between the pump's gauge and another handheld pocket gauge. Last Sunday, the majority of the ride was at 35 lbs F & R for both of us and then later we rode at 30lbs for about 2 miles. I will try the 30 lbs (per the pump) and see how it goes. If we do decide to go lower, I will be sure to go for about 1 pound each time as someone suggested.

    The good thing is, we will be able to have a baseline of sorts since there is one trail section that we always like to start with as a warm-up. I am surprised by some of the posts with the higher psi #s though, I can remember bouncing off of roots and logs at 40 psi let alone anything higher!! My WTB Stouts have arrived but I think I will hold off on mounting them for now! I couldn't stand the RaceKings (front and rear) before (labeled as 2.2 but I swear they look like a 1.9, even the GF refers to my bike as having "skinny tires" ) but after the last ride I really need to give them another chance!

  11. #11
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    Can you get 29" race kings ??

    Got a 69er, just put a Race King 2.2 Steel on the rear and I liked it, road bike resistance off road I normally ride proper knobbily 2.5's aswell so bonus.

    I've got a 29" stout on the front, top tyre best 29" tyre currently available, Stout Front, Race King rear for less Rolling resistance is working well here.

  12. #12
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    You heavy guys need the extra air I guess. I'm running in the low twenties (with tubes) on my rigid El Mar. I was running 18 pounds but pinch flatted and could feel a lot of squirm. On the flip side, I found that anything higher than ~24 psi is just too harsh. I'm only 180 lbs on a fat day so this works for me. If I had front suspension I'd go up 5 PSI, no doubt about it.

    Drew
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  13. #13
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    Anyone else doing a Stout (Front) with Race King (Rear)?

    Quote Originally Posted by Turveyd
    Can you get 29" race kings ??

    Got a 69er, just put a Race King 2.2 Steel on the rear and I liked it, road bike resistance off road I normally ride proper knobbily 2.5's aswell so bonus.

    I've got a 29" stout on the front, top tyre best 29" tyre currently available, Stout Front, Race King rear for less Rolling resistance is working well here.
    Yep, but to be sure we are on the same page - its a Continental Race King 29er Front and Rear (came OEM on a Cannondale 29er). Listed as 2.2 but actually more like a 1.9 - seriously.
    Oddly enough, I just bought two WTB Stout 29er tires from Performance (on sale at 17.99 at checkout!) but had intended to put them front and rear. Just assumed it would be off balance sort of with the Stout up front and then the Race King in the rear. If so, that would work pretty good. I had intended to get a Mountain King one day for the front as an experiment but saw the deal at Performance and couldn't resist. What tire pressures are you running in the Stout?
    Thanks,

  14. #14
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    Measuring trend side to side as 2.0" really I think, best I can guess with a measure on my wrench I'll add

    But there really tall, supple casing so take hits comfortably enough and role like there slicks which I like on the rear.

    A Stout on the rear will be hard work and will wear out really quickly.

    I run the Stout fairly hard for mud or the knobs flatten but rocks I run 5psi I'd say lower for extra cushion.

    Only got 1hour on the Race King put it on today, proper ride thursday night.

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    would like to hear how the Stout and Race King in the rear works out for the ride!

    I'll be keeping the Race Kings on for now but will be looking to hear more about that combo. When you say that you ride it "hard in mud" - I'm assuming you mean higher air pressure? if so, how much more or less than normal?
    Yeah, eyeing up the Stout I did say to myself that it might be like having an anchor in the back!

  16. #16
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    Quote Originally Posted by nepanite
    I am a little confused and need some help! My friend and I began mountain biking mid-summer. Myself on a 29er HT and her on a 26er HT. Been having a blast (used to bike years ago, its amazing how some stuff comes back quick) but have some questions about optimum tire pressures for our respective bikes when on techy trails with lots of rocks, roots, slippery off camber ledges etc. We ride in Northeast PA, prefer Moon Lake and Lackawanna State Park.

    Usually we have been riding with 40lbs front and rear (I think that got started when we had done some rails to trails in MD) This past weekend, I took both bikes to 35 lbs and noticed an improvement. Near the end of the day, we decided to try 30lbs and that was a huge improvement in grip and performance. Rider weights are me at 230lbs and her at 100 lbs. We plan on hitting the trails this weekend at 30lbs but now I am wondering how far we could take this.

    How much lower could we go and what are the key differences between the 29er and 26er tires? Right now, I am running RaceKings and she has an OEM Specialized 2.0s (moto type tread). I am assuming that she (being far lighter) could go with a lighter tire pressure but what would be the lower limits? I know this is long but it is confusing to me, especially with the differences in rider weights and also the 29er vs. 26er tire size.Thanks!
    For you 30psi is probably lower limit. For your female friend she would be much happier with considerably lower presure. My wife is 110lb she run 20psi (uses tubeless tires to do this).

  17. #17
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    any recommended tire gauge for accuracy and ease of use??

    Currently using an old Joe Blow floor pump with built in gauge and have a simple nashbar pocket gauge but have never compared them to see if they come up with the same psi for any given tire. Any gauges or pumps to recommend? Is there anyway to avoid the loss of air that happens as one pulls the pump off of the presta valve? Drives me nuts for both tires and also on the lefty fork for that matter. Thanks,

  18. #18
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    a good amount of that percieved loss of air is actually the air that's in the hose. there is some pressure loss during removal, but on a 29" mtb tire, i would think it's very minimal.

  19. #19
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    Tire pressures will be dependant on your terrain, riding style and weight. Of course the volume of tire as well.

    I'm 160# and on my HT, I generally run as low a pressure until I can feel the tire pinch on the rim. Then I add about 5psi.

    So in the dry summer when the trails are faster and I'm hitting things harder, I'll generally run a little more pressure like 35psi. But during the winter when the trails are softer and slower, I can go down to 25psi. I can run as low as 20psi on higher volume tires to get maximum grip on wet roots and rocks.

    At 100#, you may be able to go 3-5 psi less. At 230, I would think you'd need to run 5-10psi higher.

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