MTB tyre pressures

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MTB tyre pressures

Postby chriscole » Fri Mar 07, 2014 9:36 pm

Hi folks,

Acquiring a MTB for the first time in over a decade, and it appears the object of my affections come off the shelf with tubes & clincher tyres. Whilst I ponder the merits of seeing the light and moving to tubeless, what are people's feelings about the lowest sensible tyre pressure (in a 2" / 2.25" width MTB tyre on a 650B wheel) to avoid fun things like rolling the tyre off the wheel when cornering, etc? :-)

Cheers,
Chris
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by BNA » Fri Mar 07, 2014 9:39 pm

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Re: MTB tyre pressures

Postby HappyHumber » Fri Mar 07, 2014 9:39 pm

Go with the range marked on the tyre to start with. Some sidewalls behave differently in cornering.

Experimentation is really your only answer. We can only really smother you with opinions here. ;)
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Re: MTB tyre pressures

Postby trailgumby » Fri Mar 07, 2014 10:01 pm

Will depend on what you weigh, the bag size, sidewall stiffness, terrain, how hard you corner and whether or not you are using tubes or tubeless. Tubeless I run 25psi front, 28-30 on the rear at 83kg kitted up on 29x2.25 Racing Ralph tubeless ready.

It's a bit trial and error. Keep going down until you can feel tyres starting to move around too much or you start getting pinchflats on the back. Front bears less weight and is your control tyre so less pressure is normal.

With tubes I'd be looking at 35-40 psi in the rear.

Hope this helps.

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Re: MTB tyre pressures

Postby clint66 » Sat Mar 08, 2014 1:50 am

go tubeless you wont regret it.
I run 20psi in the front and 28ish on the rear. Im in Perth though, so we have a bit of pea gravel to contend with. much more grip with the lower pressure and no pinch flats or any other issues. you still need to pump up the tyres every week or so. but you get that with a tube anyway.
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Re: MTB tyre pressures

Postby dmwill » Sat Mar 08, 2014 12:17 pm

What everyone else said, experiment. Take a small pump with a gauge with you on the trails even.

I always take note of my bike setup before I go riding - tyre spec and pressure, suspension setup (pressure/rebound etc). Really helps to determine what works best.
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Re: MTB tyre pressures

Postby singlespeedscott » Sat Mar 08, 2014 3:05 pm

On the trails around Brissie I run 25psi in the front and 35 in the back. That's on a 29er with tubes. I'll never go tubeless. Not worth the hassle for how little I ride on the dirt these days.
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Re: MTB tyre pressures

Postby Duck! » Mon Mar 10, 2014 8:27 pm

With tubes, generally run at the lowest recommended by the manufacturer at least as a starting point. If you're pretty light rider, in both bodyweight and riding style, then you could quite safely run up to 5 psi below the recommended minimum. Before going tubeless, I used to run Maxxis Crossmark 26 x 2.1" at 30 psi, where the recommended minimum is 35. The only flat I had was caused by hitting a bit of barbed wire while scrambling under a gate. I weigh about 65kg in full kit including hydration pack. I ran the same tyres (standard folding bead) tubeless at 26 front & 28 rear, and now run the full tubeless versions at 24. I can go lower, but they start to feel a bit squirmy.
I had a thought, but it got run over as it crossed my mind.
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Re: MTB tyre pressures

Postby chriscole » Tue Mar 11, 2014 8:19 pm

LBS currently building up a Giant XTC Advanced 2 650B hardtail for me. Comes with some Racing Ralphs on it and a (presumably) heavy wheelset which is tube + clincher.

Will see how it goes at various pressures & riding conditions (I weigh 80kg with gear on).

Unsure about moving to tubeless as the "self-sealing" goodness sounds like it might be outweighed by the "glueing one's tyre to one's rim" badness. Also biased as I'm used to road-ish bikes with simple tubes and clincher tyres.
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Re: MTB tyre pressures

Postby Duck! » Wed Mar 12, 2014 8:14 am

No gluing with tubeless - you're getting confused with tubulars. It's just a clincher really, just with no tube.
I had a thought, but it got run over as it crossed my mind.
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Re: MTB tyre pressures

Postby clint66 » Wed Mar 12, 2014 12:59 pm

check out the videos on the Stans site. these were what sold me on it.

http://www.notubes.com/help/index.aspx
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Re: MTB tyre pressures

Postby barefoot » Wed Mar 12, 2014 2:56 pm

clint66 wrote:go tubeless you wont regret it.
I run 20psi in the front and 28ish on the rear. Im in Perth though, so we have a bit of pea gravel to contend with. much more grip with the lower pressure and no pinch flats or any other issues. you still need to pump up the tyres every week or so. but you get that with a tube anyway.


Yeah, that's about what I run too.

With tubes. Under ~85kg of me.

Haven't had a flat in years. Have been tormenting the puncture fairies with this fact for years and they still haven't smote me for it.

I hit the front up to nearly 30psi a few weeks ago. It was awful. Nasty squirrelly feeling like the front was about to wash out on every corner.

I don't know how anybody can ride a MTB with 40psi in the tyres...

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Re: MTB tyre pressures

Postby m@ » Wed Mar 12, 2014 3:35 pm

chriscole wrote:LBS currently building up a Giant XTC Advanced 2 650B hardtail for me. Comes with some Racing Ralphs on it and a (presumably) heavy wheelset which is tube + clincher.

If the RRs are the UST/"Tubeless ready" model, all you'll need to do is swap the rim tape for Bontrager tubeless strips and valves, pour in some Stan's sealant and throw them on a compressor to seal 'em up. About six months to a year later, you might need to use a spoke tool to remove the valve core for cleaning (a 2 minute job), or unseat one side of the tyre to remove the dried-up gribbly bits and pour in some fresh sealant.

Time saved over fixing punctures = lots. Fun had by running stupidly low pressures = lots more! :mrgreen:
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Re: MTB tyre pressures

Postby trailgumby » Wed Mar 12, 2014 4:27 pm

Check the sealant and top up every 3 months. TLR tyres require sealant to stay liquid or they will leak. Full UST you can get by without any sealant if you dont care about getting punctures.

OEM tyres are usually TLR or simple folding bead. They aren't known for their robust sidewalls.

Some guys won't stop to offer help with punctures if they see you have RaRa's. I'm not sure how that psychology is supposed to work myself, but it does show I suppose the level of irritation among riders in my area with the weakness of the sidewall on this tyre.

The SnakeSkin version is supposed to be much better. I'll be going that way next purchase after pretty much destroying the sidewall after dried sealant let me down last ride.

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Re: MTB tyre pressures

Postby Duck! » Wed Mar 12, 2014 6:39 pm

m@ wrote:
chriscole wrote:LBS currently building up a Giant XTC Advanced 2 650B hardtail for me. Comes with some Racing Ralphs on it and a (presumably) heavy wheelset which is tube + clincher.

If the RRs are the UST/"Tubeless ready" model, all you'll need to do is swap the rim tape for Bontrager tubeless strips and valves, pour in some Stan's sealant and throw them on a compressor to seal 'em up. About six months to a year later, you might need to use a spoke tool to remove the valve core for cleaning (a 2 minute job), or unseat one side of the tyre to remove the dried-up gribbly bits and pour in some fresh sealant.

Time saved over fixing punctures = lots. Fun had by running stupidly low pressures = lots more! :mrgreen:

UST & "Tubeless Ready" (TLR) are very different tyres. TLR RaRas (which will be the stock tyres) are a waste of time - the super thin sidewalls are about as airtight as a flyscreen and take weeks to seal enough to stop the sealant spraying out through them. Those things are the embodiment of the horror stories you hear from people fearful of converting to tubeless, but the good news is they are the exception and definitely not the rule.There are many, many far less troublesome tyres available (ironically including other variants of RaRas, providing they're suited to your kind of dirt).
I had a thought, but it got run over as it crossed my mind.
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Re: MTB tyre pressures

Postby chriscole » Wed Mar 12, 2014 7:49 pm

Thanks for the input guys.

I think you've effectively convinced me to stick with tubes and normal tyres for the time being. :-)
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Re: MTB tyre pressures

Postby magilla0_2 » Wed Mar 12, 2014 9:58 pm

Tubeless , with a sealant are the only way to go and use tyres designed for tubeless use , three years of some pretty serious mountain biking and the only puncture has been caused by a severe slash in the side wall.
In my 26" and 29er with 2.1 tyres, I ran 28 lb front and rear, and now on a 650b with 2.5 tyres I am running 23-25 lb and I tip the scales somewhere between 90-95kg
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Re: MTB tyre pressures

Postby m@ » Thu Mar 13, 2014 9:11 am

chriscole wrote:Thanks for the input guys.

I think you've effectively convinced me to stick with tubes and normal tyres for the time being. :-)


Nice going guys! :roll: :wink:

Now, I thought the stock RRs on my Anthem were labelled UST, but apparently not - possibly I was bamboozled by Schwalbe's EVO label.

Either way though, I believe the EVO model has SnakeSkin sidewalls... I rode them quite a bit before going tubeless and they did have some pinholes but still sealed up almost instantly and didn't lose any pressure after the first 24 hours.

I've since ridden them to death and replaced with Nobby Nic/RR EVOs, which were installed tubeless from new with no noticeable loss of pressure at all. So if the OP has EVO/SnakeSkin tyres - which are supplied as stock on some Giants - from my experience he has little to lose by going tubeless.
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Re: MTB tyre pressures

Postby Bentnose » Sat Mar 22, 2014 3:20 pm

I just put a new tubeless Snakeskin RR on the front and found no fluid oozing out of the sidewalls meaning they sealed up a lot faster than the standard RR's, the sidewall is noticeably thicker on the snakeskin version. I run 28-30psi on the front and 32-34psi on the back, any lower and I find the tyres move around too much and I bottom the rim out on pointy bits.
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Re: MTB tyre pressures

Postby trailgumby » Sat Mar 22, 2014 5:33 pm

What do you weigh, out of interest? I can't run rhe front that high - too skatey.

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Re: MTB tyre pressures

Postby Bentnose » Sun Mar 23, 2014 7:03 am

With a full camelback and all the gear, it would be 77kg. Some of the discrepancies may be innacuracies of pressure gauges, I always go by a standalone Zefel presta pressure gauge I have, my Silca track pump is a little hard to read accurately and it looks like it reads lower than my Zefel gauge, so about 35psi on the Silca seems to be 40psi on the Zefel gauge. Which one is correct, I don't know, everybodies gauges would be a little different which could cause confusion on a topic like this.
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Re: MTB tyre pressures

Postby magilla0_2 » Sun Mar 23, 2014 7:16 am

Man I wish I was 77 kegs, you will get away with 28 psi tops
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Re: MTB tyre pressures

Postby trailgumby » Sun Mar 23, 2014 12:28 pm

I have one of those BBB digital gauges which shows pressures in PSI to one decimal place. I leave it in my Camelbak, since i want to have it with me out on the trail just in case, and it only weighs a few grams - outstanding value for under $30.

My track pump, a Topeak Joe Blow something or other, seems to be close enough to it.

So long as your gauge is consistent, the absolute number you arrive at by trial and error doesn't matter.... but, you might just have to take it with you to each event you do, as it won't compare to what others have.
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Re: MTB tyre pressures

Postby Bentnose » Sun Mar 23, 2014 3:42 pm

trailgumby wrote:I have one of those BBB digital gauges which shows pressures in PSI to one decimal place. I leave it in my Camelbak, since i want to have it with me out on the trail just in case, and it only weighs a few grams - outstanding value for under $30.

My track pump, a Topeak Joe Blow something or other, seems to be close enough to it.

So long as your gauge is consistent, the absolute number you arrive at by trial and error doesn't matter.... but, you might just have to take it with you to each event you do, as it won't compare to what others have.


I take it with me to every event, I find tyre pressures to be quite critical on a MTB for maximum performance, particularily with tubeless when you can run them so low, too high and you have no grip, too low and you can damage your rims and they feel too squishy. If I went back to tubes it would feel like no grip all of the time.
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Re: MTB tyre pressures

Postby singlespeedscott » Sun Mar 23, 2014 6:12 pm

Bentnose wrote:
trailgumby wrote:I have one of those BBB digital gauges which shows pressures in PSI to one decimal place. I leave it in my Camelbak, since i want to have it with me out on the trail just in case, and it only weighs a few grams - outstanding value for under $30.

My track pump, a Topeak Joe Blow something or other, seems to be close enough to it.

So long as your gauge is consistent, the absolute number you arrive at by trial and error doesn't matter.... but, you might just have to take it with you to each event you do, as it won't compare to what others have.


I take it with me to every event, I find tyre pressures to be quite critical on a MTB for maximum performance, particularily with tubeless when you can run them so low, too high and you have no grip, too low and you can damage your rims and they feel too squishy. If I went back to tubes it would feel like no grip all of the time.

I run tubes I have plenty of grip. The tiny amount of friction between the tyre and a 1/4mm thick inner tube has very little effect on tyre grip.
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Re: MTB tyre pressures

Postby trailgumby » Sun Mar 23, 2014 6:26 pm

singlespeedscott wrote:I run tubes I have plenty of grip. The tiny amount of friction between the tyre and a 1/4mm thick inner tube has very little effect on tyre grip.

True. But then friction isn't really the issue. It's the ability of the casing or casing/tube combo to conform to the track.

The extra rubber in the shape of the butyl rubber tube contributes little to supporting the casing, but reduces the ability of the tread to conform to the trail surface. A possible exception would be latex tubes.

That's my theory anyway, and I believe it would be the consensus view.

The primary advantage to tubeless is the ability to run lower pressures without pinchflatting, expanding the contact patch. The lower limit is when the tyre starts squirming around too much and burping becomes a risk.
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