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MTB tyre pressure

Posted: Sun Jan 13, 2008 5:46 pm
by DavidRen
I am a total newbie to MTB and whilst i haven't had a flat yet, I would like to get some tips on recommended tyre pressure for trails / rocks.

Are there any recommended pressures at all ? My tyres have a 40-65 psi (2.8 - 4.5 bar) rating.

Any help would be appreciated !

Posted: Sun Jan 13, 2008 5:50 pm
by snailman
it also depends on the weight of you and your bike combined any idea what that would be?

Posted: Sun Jan 13, 2008 5:52 pm
by toolonglegs
35 -40 psi...You will get flats more from not being smooth over the rough stuff than tyre pressures as a newbie.

Posted: Sun Jan 13, 2008 6:31 pm
by Hawkeye
Depends on your combined bike+rider weight, plus the terrain, plus the bike. I'm about 85-87kg fully laden and the dual-suspended bike another 13kg. I run my WTB Velociraptors around Manly Dam at about 40psi. Traction is good enough and I've yet to pinch flat. I could go lower to about 35psi but wouldn't like to be too much less around the dam,

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Posted: Sun Jan 13, 2008 9:08 pm
by Kalgrm
As others have said, it depends on the way you ride, your weight, the track conditions and your tyre widths. Most beginners put too much pressure in their tyres: an error aided by tyre makers who are scared of having their pants sued off them (45psi is too high for nearly everybody under nearly all off-road conditions).

Since I can't advise you precisely, I'll give you my details and you can extrapolate:

My bike and I weigh in at around 95kg with water, tools and clothes. I'm riding a FS bike (Specialized Epic) for cross country riding. My tyres are 2.1" wide. The tracks I ride vary from very rocky to pea gravel to hard-packed dirt. I use tubes.

At Lysterfield (smooth groomed hard-pack with a few rocks and some tame log-overs) I was running 30psi in the rear and 28 in the front. At home in the west, it's pea gravel and sharpish rocks, so I run 32psi on the rear and 30psi on the front. One particular track has some DH stuff (sharp rocks, terrible lines) on it, so I need to run 36psi R and 34psi F.

Tubeless tyres obviously can't pinch flat, so you can run lower pressure with them.

The principle is to use the lowest pressure you can without pinch flatting. Start with your tyres at say 35psi and lower them a little bit at a time on a ride until you think you will pinch flat (or actually do such), then put 3 to 5 psi back in. From there, you can work your pressures to suit your track conditions.

Cheers,
Graeme

Posted: Sun Jan 13, 2008 11:14 pm
by Hawkeye
Thanks for sharing your experience. I might run mine a little lower, then, if you seem to be getting away with pressures like that.

A thought, though: do you reckon a hardtail would be a little more likely to pinchflat on the rear, without the rear suspension to cushion the jolt at the upper limit of drops you'd take on such a bike - especially with a less experienced rider on board (and I'd include myself there)?

Posted: Mon Jan 14, 2008 3:22 am
by snailman
what kind of pressure have u been running lately j.r?

Posted: Mon Jan 14, 2008 7:49 am
by Kalgrm
J.R.,

I was running about 2 psi more on my HT, but I never really tried to go much lower than that. I'd say 2 - 5 psi more in tyres on a HT (esp. the rear) might be a wise thing, but if you use the "5 psi over pinch flat pressure" technique, you'll be able to set it for your own style of riding (including the HT consideration).

Cheers,
Graeme