tyre pressure

thomassainsbury

Hi all

I am a triathlete so used to road bikes. I have just purchased my first MTB, a spec rockhopper pro 2013 29er. Nothing special but will do me. I have no idea on what psi to take the tyres to for off road. any advice, minimums and maximums etc. When should I increase and/or decrease psi.

Thanks in advance

buddy_club

The tires should have maximum/minimum pressure rating written on the sides, have a quick look. Rocks and roots etc will be gripped better with lower pressure, but lower pressure has more rolling resistance, i run mine at about 35-40psi and it is fine for very wet conditions. Try a few different pressures where you ride and see which one you find is better.

cooldad

I run mine around 25psi front and 30psi rear, and I'm quite heavy.

gt-arrowhead

Its a personal preference thing. Some people (like me) like to run them a bit higher as they roll faster. Some people like to run them softer for more grip.

I prefer a softer rear than the front in the muddy stuff to stop wheel spinning.

nicklouse

Read the info in the FAQs.

Asking other people what they run is not very useful as there are so many variables.
Weight, tyres size, tubes,riding style.trail conditions.

thomassainsbury

Thanks all for your advice. Really helpful, road bikes are a bit more black and white than MTB it seems. Although still a preference thing.

Will try 25 and see how it feels. I really am new to MTB so need to start somewhere.

peter413

As has been said it depends on so many things. I run 30 psi front, 40 psi rear with the same tyres as a friend who runs sub 25 psi. There is quite a weight difference between us and we have different riding styles which explains why though. Different tyres even affect what pressure your run. I run that 30/40 with most of my tyres except the Crossmark's on my XC bike which are at 35/45 just because they behave slightly differently to the stiffer tyres on my other bikes.

Just an FYI, higher pressures don't roll better because the tyre can't deform around obstacles so is just bounced around the place so not only do you have less grip with too high pressures, your tyres are actually slowing you down on the straights as well.

buddy_club

What I'm saying is that for road riding/gravelly footpaths a tyre with more pressure will have less rolling resistance, especially as I have to do about 5miles in the road to get to decent trails.

The Rookie

peter413 wrote:

Just an FYI, higher pressures don't roll better because the tyre can't deform around obstacles so is just bounced around the place so not only do you have less grip with too high pressures, your tyres are actually slowing you down on the straights as well.

Slight over simplifiaction though, 6psi will roll slower than 12, but there is an optimum somewhere (that depends very much on tyre and surface) and then rolling resistance starts to increase with pressure. There was some work done by an Employee at Schwalbe on this but the results are poorly presented and don't really help, after all a smooth gravel fireroad is much like tarmac and so higher pressures will improve rolling resistance pretty much however hard you pump them up (within stated limits)

peter413

buddy_club wrote:

What I'm saying is that for road riding/gravelly footpaths a tyre with more pressure will have less rolling resistance, especially as I have to do about 5miles in the road to get to decent trails.

We're talking about off road riding though. The OP has already said he knows about road riding.

It was a little bit of an over simplification, yes. There is obviously a limit with how low to go but this usually becomes obvious because the tyre starts squirming all over the place and puncturing all the time. I'd have to disagree about the gravel paths thing though. IME slightly higher pressure than normal can roll faster but there is still a point it starts to get bounced around which slows you down. You're better off setting up the bike for the harder/rougher trails anyway IMHO.