Tyre Pressures

sc999cs

I've come from the dark side where tyres are pumped upto 120 PSI and look like razor blades. I'm trying to get my head around tyre pressures for mountain biking. How hard should your tyres befor different conditions?

For example, dry hard ground should you have high or low pressure? Same question for other surfaces like lose dirt, mud etc. Not after specific pressures - just general guide lines.

supersonic

Depends on the tyre, and volume (width). And your preference! Experiment with the ranges that the manufacturer provide. Though these are often high to be on the safe side.

*AL*

Depends on tyre size, wheel size, tyre type, rider weight, bike configuration, ground conditions...........

sc999cs

So it is all personal preference then? That'll make it easier. I'll try dropping my pressures because I'm running them at the maximum (as I do my road tyres) and see if that makes a difference (don't grip too well at the moment).

supersonic

Just don't go as low as they roll of the rim, I'd say 25psi is a safe minimum for an average weight rider/tyre size.

Dartster

*AL* wrote:

Depends on tyre size, wheel size, tyre type, rider weight, bike configuration, ground conditions...........

lol f**k me, how exactly do you calculate the correct tyre pressure from all those variables? Thats gotta be some sort of a formula :? :roll:

People always tend to give that sort of answer in an attempt to look clever........So, like u said, your not looking for an exact answer and are new to mtb tyre pressures, so as a guideline, i tend to run between 35-40 psi.

Closer to 35 in the wet, closer to 40 in the dry. And normally a few psi more in the rear than the front. Simples

Thats just what i personally go by. Its not as complicated as alot of people like to make out.

The softer it is, the more grip you have but also the more chance of a pinch puncture when you hit those roots or rocks.

Hope that helps as a rough guideline!

jon1993

there is no real formula - you work in on this basis
more pressure - less rolling resistance and less grip + less comfort
less pressure - more rolling resistance and more grip + more comfort
this works up untill the point where you start nipping up your tyres and moveing on the rim so when there too low you will get lines on your side walls. its completely unique to the surface what you can get away with basically

cooldad

Max pressures will be terrible.
I generally run mine slightly lower than recommended minimum.

*AL*

Dartster wrote:

*AL* wrote:

Depends on tyre size, wheel size, tyre type, rider weight, bike configuration, ground conditions...........

lol f**k me, how exactly do you calculate the correct tyre pressure from all those variables? Thats gotta be some sort of a formula :? :roll:

You don't 'calculate' the 'correct' tyre pressure (which the OP didn't even ask for incidentally), you adjust the pressures from a base point (ideally the manufacturers recommended settings) until you find something that works for you.

Dartster wrote:

People always tend to give that sort of answer in an attempt to look clever.......

On the contrary, I'm merely pointing out that there's no hard or fast rule when it comes to tyre pressures, and what works for one won't necessarily work for someone else.

Dirtydog11

Dartster wrote:

*AL* wrote:

Depends on tyre size, wheel size, tyre type, rider weight, bike configuration, ground conditions...........

Closer to 35 in the wet, closer to 40 in the dry. And normally a few psi more in the rear than the front. Simples

Thats just what i personally go by. Its not as complicated as alot of people like to make out.

So your advice is to run all your tyres at 35-40 psi irrespective of rim/tyre width/construction it just depends on whether it's dry or wet? :?

I agree it's not rocket science but that's oversimplifying things, tyre construction alone has a huge influence on pressures.

No one is trying to look clever, it's a fact that you wouldn't run the same pressure in a pair of Maxxis Minion 2.3 dual/single ply as you would in a pair a 2.3 Speed King supersonics, nowhere near!

ThePriory1978

As mentioned earlier i also generally run my pressures slightly lower than the recommended minimum and always with slightly more pressure in the back than front.

My current tyres state 35psi min and i run them at 34psi back. 32psi front. Its a hardtail and i'm 11stone.

I'm always being told i can run them at a lot less psi but for peace of mind from pinch flats i choose to run them at what i do. I'd probably drop another psi or two if i had more travel runing softer and rear-sus.

Daz555

If in doubt start at 35psi and see how you get on. I started there and have moved closer to 30 on the front. To be honest though I do not check every ride and have on occasion gone out for a ride with a smidge less than 25 at both ends and not noticed any ill-effect.

1mancity2

I run mine 36psi front and 38/40 rear I find this gives me plenty of grip and enough air in them to stop pinch flats (most of the time)

Just experiment with them and you will get a feel for what is right and what's not.

John Moore

If you run tubless you can run even lower pressures.

I run most of mine around 25psi

But my fat bike (3.7" tyres) run at only 9psi down to 7psi on soft sand

Dartster

Dirtydog11 wrote:

Dartster wrote:

*AL* wrote:

Depends on tyre size, wheel size, tyre type, rider weight, bike configuration, ground conditions...........

Closer to 35 in the wet, closer to 40 in the dry. And normally a few psi more in the rear than the front. Simples

Thats just what i personally go by. Its not as complicated as alot of people like to make out.

So your advice is to run all your tyres at 35-40 psi irrespective of rim/tyre width/construction it just depends on whether it's dry or wet? :?

I agree it's not rocket science but that's oversimplifying things, tyre construction alone has a huge influence on pressures.

No one is trying to look clever, it's a fact that you wouldn't run the same pressure in a pair of Maxxis Minion 2.3 dual/single ply as you would in a pair a 2.3 Speed King supersonics, nowhere near!

Nope.

I didn't really give any advice as such....what he asked for was a GUIDELINE to tyre pressures, basically somewhere to get started.....which is what i did, i gave him a GUIDELINE of what i use....as stated in the post.

He was coming from Road tyre pressures so he wanted to know roughly what he should be putting in his mtb tyres....and as proven by two of the posts above this one (3 including mine) 35-40 is a good general, average pressure to start at.

Sometimes this is all people need mate, having the reply "it all depends on tyre rim, width, bike, what you had for breakfast, how many rocks there are on the trail" isn't very helpful is it....because if we are honest, pressures don't vary THAT much on your general mountain bike.....be it a hard tail or a full susser. It only really changes dramatically when you stick DH specific tyres or tubeless tyres on there.

supersonic

They vary significantly - I've seen XC bikes with 20-60psi! It depends a lot on the tyre (some max ratings can be quite low), the rim (as certain pressures may roll off if the rim is too narrow, and again may have a pressure rating). Add in conditions and your preferences and you can see the range is large.

Experimentation is key, paying close attention to max limits. (and low, if want to avoid pinch flats)

Dartster

that would be very unique to be riding with 50-60 psi on a mountain bike though....thats pretty rock hard.

You pop in to a Bike store and see which bikes run that sort of pressure.....it won't be your average mountain bike.

I knew i shouldn't have bothered posting as it would result in the typical "lets get finicky and think of every extreme" forum response.......

...but i thought i would just tell him what pressures i use, so he could use that as a guidleline.

supersonic

Forums are for discussing things - I have not said you are wrong!

I see plenty of XC riders with 50psi plus in, is not uncommon (for better or worse). Especially in narrower tyres.

mattv

The wider the tyre is, the lower the pressure you can run down to. I generally run hardpack tyre about 2.0 wide, at 30 round the woods, 35 on towpaths, 45 on road.

ric7481

14 stone rider - spesh xc pro - mavic crossrides, kenda small block 8's in 2.1 - run around the 50 psi mark..............works for me......quite comfortable and enough grip - mainly south downs, dusty hard pack, loose gravel, chalk and flints....for the winter will be moving back to conti mountain kings, 2.2 -approx 45psi

Thinking about dropping to 1.9 kenda's next year ?

Daz555

ric7481 wrote:

14 stone rider - spesh xc pro - mavic crossrides, kenda small block 8's in 2.1 - run around the 50 psi mark..............works for me......quite comfortable and enough grip - mainly south downs, dusty hard pack, loose gravel, chalk and flints....for the winter will be moving back to conti mountain kings, 2.2 -approx 45psi

Thinking about dropping to 1.9 kenda's next year ?

50psi. Blimey I reckon my fillings would come loose - even on my full susser.

bozzy752

I think Dartster has a point here, sometimes people need an "actual" figure to put in their tyre whether it be a "ballpark" one. I know as has been stressed in many of the posts there is so many variables to consider but that doesn't help when NO figure has been mentioned as you can't inflate your tyres to "variables psi" .

But it's good to discuss keep up the good work !

nicklouse

bozzy752 wrote:

I think Dartster has a point here, sometimes people need an "actual" figure to put in their tyre whether it be a "ballpark" one. I know as has been stressed in many of the posts there is so many variables to consider but that doesn't help when NO figure has been mentioned as you can't inflate your tyres to "variables psi" .

But it's good to discuss keep up the good work !

But it is not possible. As there are too many variables.
Tyre size.
Rider weight.
Tyre type.
The terrain.

Etc. see the FAQ on this it is all covered.

And for he record I have different pressures in the tyres of all ( well maybe he same in two) my bikes.

Have fun playing.

cat_with_no_tail

nicklouse wrote:

bozzy752 wrote:

I think Dartster has a point here, sometimes people need an "actual" figure to put in their tyre whether it be a "ballpark" one. I know as has been stressed in many of the posts there is so many variables to consider but that doesn't help when NO figure has been mentioned as you can't inflate your tyres to "variables psi" .

But it's good to discuss keep up the good work !

But it is not possible. As there are too many variables.
Tyre size.
Rider weight.
Tyre type.
The terrain.

Etc. see the FAQ on this it is all covered.

And for he record I have different pressures in the tyres of all ( well maybe he same in two) my bikes.

Have fun playing.

Exactly this.

Also, even if you were able to cover off all of the physical variables, there is still the human factor.

I could be the OPs identical twin, riding the exact same bike on the same ground at the same time with the same tyres and same riding style / skill. And STILL have a different pressure because I just prefer the different feel / grip levels etc.

Rushmore

I run 2.25 Nobby Nicks.

13 1/2 stone

about 45psi on the back and around 30 on the front..

Ghostt

It's interesting to see a lot of people running their tyres at low pressures, as I've always stuck towards the higher end of the recommended pressures. But hey, it's all down to preference and what feels good for you, so play around with them. At the moment, I run Panaracer Fire XC Pro, 2.1", 45psi rear and 40psi front, so pretty much in the middle of the recommended (30-50psi). I'm 10 stone and they're on a hardtail, good balance of grip and speed.

cooldad

I am about 14st and run around 30psi front, 35 rear, so what CWNT said a few posts up.

Mojo_666

15.5 stone and I run 25psi front and back on 2.4 nic/Albert I have run at 20 on cwmcarn DH for a full day too.

That is measured using a topeak digital gauge not the ones on pumps.

I find higher pressures really skittish

benpinnick

I too run 30 fr, 35 rr. Mainly because I am too lazy to change it, and it works.

andymc06

I was running 35 psi front and rear on 2.35 Maxxis High Rollers before winter. I decided to drop to 32 psi on the front to see what effect it had. I found it offered a noticeable improvement in grip without any noticeable difference in rolling resistance. Small pressure differences can alter performance significantly so , as stated above, experiment and see what works for you.

concorde

I have never checked mine and to be honest I never plan to either. The back one looks pumped up enough and so does the front one, that's how I've always done it :-)