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Tire pressure for all around XC riding?

458K views 583 replies 276 participants last post by  Travolta 
#1 ·
I was curious to know what tire pressure is the best for all around xc use?
I had IRC Mythos on my K2 and ran them very high because someone told me that I would get pinch flats left and right if I didn't.
I now have Kenda Nevegals on my Cannondale Rush and was curious where people tend to have their pressure set. I normally ride pretty rocky/root filled technical terrain, with a little mud thrown in once in a while and some nice long downhills.
Any suggestions would be great. Thanks
 
#127 ·
trailville said:
60psi, Wow.
I don't even run 60psi in my 700x35 cross tires on my touring bike.
Why not? You'll roll a lot faster.
Dad worked in the tire business for 50 years. I've gone out on a ride and wondered what was going on, since it is such a drag. Are my breaks rubbing? Check and see that tires had leaked to 40psi. Not sure why some would think a tire with more pressure doesn't roll faster, with less resistance. I can very easily feel (not perceived) a huge difference in rolling resistance, with high pressure.

Chris.
 
#128 ·
happydog500 said:
Why not? You'll roll a lot faster.
Dad worked in the tire business for 50 years. I've gone out on a ride and wondered what was going on, since it is such a drag. Are my breaks rubbing? Check and see that tires had leaked to 40psi. Not sure why some would think a tire with more pressure doesn't roll faster, with less resistance. I can very easily feel (not perceived) a huge difference in rolling resistance, with high pressure.
I believe there was some kind of a study recently that showed that rolling resistance relative to tire pressure changed once you left the flat smooth surfaces behind. But even without that, I simply prefer traction, control, and comfort over rolling resistance. I'd rather clear a technical section or make a really tough techy climb than roll fast on the easy sections. Everyone has their own preferences.
 
#130 · (Edited)
happydog500 said:
Why not? You'll roll a lot faster.
Dad worked in the tire business for 50 years. I've gone out on a ride and wondered what was going on, since it is such a drag. Are my breaks rubbing? Check and see that tires had leaked to 40psi. Not sure why some would think a tire with more pressure doesn't roll faster, with less resistance. I can very easily feel (not perceived) a huge difference in rolling resistance, with high pressure.

Chris.
Here's some info for you to give you confidence to try a larger volume fast rolling tire at low pressure. Many have switched over and like it. Like plenty before you,it pays to read all of a thread not just the last posts.

http://www.schwalbe.co.uk/pdf/techinfo.pdf pages 14 to 16
 

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#159 ·
Outstanding paper. For the lazy, here is a quick summary:
Schwalbe said:
Off-road rolling resistance decreases significantly with increased tyre width. For instance on grass the wide mountain bike tyres required 15.41 W less rolling resistance power than their narrower equivalents.
Schwalbe said:
Off-road a reduction of tyre pressure reduces rolling resistance. In a meadow for instance going back from 4.0 to 1.5 bar (57 to 21 psi) can save remarkable 18 Watts of power.
Schwalbe said:
FIRMLY inflated narrow tyres are history. 'Fat' and less air speed things up!
On the road it's the opposite.

As for me, as low as the tire does not squirm. I can't get myself to slam the wheels into rocks to see how low you can go without a flat.
 
#132 ·
Don't know your weight but 60PSI may be right for a skinny 2.1 tire under a 300 pound rider.

You'll be amazed at what you can clean on a slow technical climb by using a fat (2.5) front tire at low pressure. It works even better on technical descents. A real confidence builder. Most people are amazed at the difference a fat low pressure front tire makes.

However, if most of your riding is smooth hardpack, then all that big tires do is slow you down.
 
#135 ·
This is something that came up the other day when my buddy just bought his first Full Suspension bike (Trek Fuel EX5). We are here in the Tampa Area and I asked the Trek Rep to check the tire pressure out the door and adjust it for one of the locations we hit (Alafia State Park). He said he runs them at 40psi. I thought that was awfully high since I run my Stumpy FSR 29 at about 28 front and back, he thought that was awfully low. I weigh in about 240lbs and I feel pretty fast on the trail at that pressure although I may try a higher pressure just for the comparison. I havent gotten a flat since I moved the pressure above 25.
 
#136 ·
60 front/ 70 rear....

trailville said:
60psi, Wow.
I don't even run 60psi in my 700x35 cross tires on my touring bike.
on the pump track, 2.1 small block 8's, 165lb rider, hardtail.

trailville: saw your comment about this being a xc thread - when did this become strictly a xc thread?? xc can cover a broad range of riding on a broad range of terrain. that's what's been good about this thread, there's a lot of specific info here that may be helpful for what certain riders are looking for.

sometimes higher pressure works very, very well.
 
#137 ·
1 rather major thing to remember here people :-


PRESSURE GUAGES DON'T WORK!!!

The 60 is likely really 40's area, and the 22's are likely 30's area.


Try a few marvel at how your mates give a totally different reading to your own.


Some tires, you need higher pressure to keep the knobs out to get traction, RK2.2's are like this, run them to soft and they become full on slicks and yes they'll role faster but there slicks nothing more.
 
#138 ·
mr.niles said:
trailville: saw your comment about this being a xc thread - when did this become strictly a xc thread??
When the OP posted it as "Tire pressure for all around XC riding" . But it's not like this would be the first thread to run a little off the initial topic.
 
#139 ·
yes, a good gage is necessary....

Turveyd said:
1 rather major thing to remember here people :-

PRESSURE GUAGES DON'T WORK!!!

The 60 is likely really 40's area, and the 22's are likely 30's area.

Try a few marvel at how your mates give a totally different reading to your own.
.........
never trust the gage on your pump - it is almost surely wrong. use it as a guideline to overinflate your tires before using a proper gage to bleed down to your target pressures. get an accurate gage from mcmaster-carr or a motorcycle shop, etc. the only problem with these gages is no chuck for presta valves. to get accurate pressures while using a good gage, i've had to convert all my tires to shrader. i don't recommend using those little brass presta-to-shrader converters.

my buddies like to use my gage when we ride together, because we all trust it.
 
#140 · (Edited)
Tire Bicycle tire Wheel Bicycle wheel rim Spoke
How much sag should your high volume tire show under rider weight when using lower tire pressure? This seems pretty soft what I have here in these tires and shows some tire sag with my 155 lbs. When squeezing the tire is feels pretty soft. Running Forte Lunar light tubes. I don't have a decent tire guage.
 
#141 ·
As others have said, get a tire gauge. Visual "sag" of the tires doesn't give you very much information IMHO as there is so much variability in sidewall stiffness amongst different tires. You need to experiment with tire pressures in different conditions to find out what works best for you.
 
#142 ·
ancient rascal said:
View attachment 615687 How much sag should your high volume tire show under rider weight when using lower tire pressure? This seems pretty soft what I have here in these tires and shows some tire sag with my 155 lbs. When squeezing the tire is feels pretty soft. Running Forte Lunar light tubes. I don't have a decent tire guage.
Good question. From your picture, one cannot definitely identify substantial sag. You tire really feels pretty soft?
I tried the same with my bikes. The first has Mythos XC II and the second Fat Albert tires. To investigate the sag, I took pictures when sitting on my bike (i.e. sag) and when the bike unloaded (i.e. no sag). You can clearly see that there is sag under rider weight (165 lbs).
Note that the tire pressures were carefully adjusted by a mountainbike tire pressure specialist. He knows how to account for the individual aspects of the tires, the bike and its rider.
 

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#143 ·
Prolly need to use a few methods to get it close. Hand squeeze. tire gauge. And just a thought. A sag gauge. Have a weight set up to enforce a sag on said wheel on a rigid floor. Have a means to measure the inside part of the rim to the floor measuring sag. Once you find your ideal tire pressure you can get back to it with the sag factor. Example floor to inside top of rim aprox 3 inches or whatever it is. Horseshoe type gauge over bottom of rim. Bet it gets it pretty close. :skep: It's OK to let me have it on this.....I can take it ! :D
 
#145 ·
I'm 190 pounds plus gear and I'm riding conti Xking 2.2 FR/RR on flow rims. Running 18psi (according to my pump) front and 23psi rear lately and am very happy. Not many large sharp edges to worry about in my local trails. I'd up the pressure a bit if riding rougher trails at speed but only as much as is necessary. The traction and control of "softer" tires is awsome! Really helps keep the bike planted.
 
#146 ·
I am runing Botrager XDX, tubeless. Run 18 front 20 rear, and it's ok for grip and bump absorbtion, no rim contact, but if you end up jack knifing the front you will pop the tire of the rim, or loose air presure.
25 front and 30 rear doesn't soak up the bumps as good (you feel more of the terrain) but the tire stays put :)
 
#147 ·
I've posted last year in this thread and was running 2.1 Nevs. Had a ton of flats last year. Running tubes.

This year I switched tires and am running a 1.95 Nev (150g lighter than 2.1) front and my Karma rear (under 400g which is around 280g lighter than the rear Nev 2.1 it replaced).
Pressure for several XC races has been 27 psi front and 29 psi rear with no flats(tubed) (knock on wood!!!)
Traction has been better than I anticipated with a couple of wet races and our local race at Camp Fortune is extremely gnarly, rocky and rough :)
Doing an Ultimate XC race on 19th of June, 100 kms of crazy single track and 10,000 - 12,000 feet of climbing from what I read on this tire combo so will be a good test :)

Cheers,
Paul
 
#149 ·
So a quick report on the UltimateXC 100km race.
Managed to finish in 10 hr and 40 mins with one flat and one slight mechanical.
I was running the 1.95 Nev F @ 27 psi and 2.0 Karma R @ 29 psi.
Where I flatted several other riders flatted. It was a rough fast downhill section.
99 % f the trails were dry or mildly moist. It consisted of soft loamy forest floor to rooty to gravel to Canadian shield solid rock. Were a couple short sections of maybe 50 feet of swamp black mud, bit clayish.
I had super traction except the clay part and a few fast downhills with smallish type gravel.
There were a lot of STEEP sections and the tires had more traction than I had power left haha.
Two gravel climbs of 1 hr each of relentless no stop UP, no plateaus, of 8-25% section of 1600 ft and 1900 ft with 1-2 inch gravel. Was pretty loose stuff but still was gripping well with minimal slippage. Some of the downhill sections after those climbs were insane! ! ! Switchback after switchback hard on the both brakes feathering front brake to not go over bars ! !
In retrospect I am super happy with these tires in any type of dry conditions and non clay type mud. OK on wet roots from other rides.
So for me on my 4" FS GT @ 28ish lbs and me around 135 lbs the 27-29 psi worked really well. I rode just about every type of dry conditions... Sand, tall grass, Loamy forest, rooty forest, big/small gravel, rock, dirt .....
Was a section at finish as we zig zagged downhill through the village on pavement and cobblestones that I was just ripping through and the tires felt super solid with no feeling of the tire wanting to roll on the rim. I felt like I was rolling on the road bike !
Cheers,
Paul
 
#151 ·
Ive kept mine at about 28 front and about 26 back....that seems to work fairly well for me right now. I run tubes and still no issues...but I have tried a gamut of pressures and noticed the higher pressures (at least for me and my trails) tended to slow me down...alot, and backing them off gave me more speed and maneuverability....so my recommendation is to try some variations out for yourself and see what you like
 
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