# Under Pressure



## Cyclist33 (1 Mar 2015)

hi

just curious to know what sort of psi goes in your tyres? ive just returned to having a mtb and im just running on what the shop bloke put into the tyres, but curious what the current paradigmatic range of pressures looks like.

thanks

stu


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## Turbo Rider (1 Mar 2015)

Check the sides of your tires. My road bike tires vary between 80PSI and 115PSI and I keep them at 110PSI to allow for post inflation pssssssssst...also because I prefer the solid feel to the spongy feel, but that's a personal thing


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## T.M.H.N.E.T (1 Mar 2015)

Turbo Rider said:


> Check the sides of your tires. My road bike tires vary between 80PSI and 115PSI and I keep them at 110PSI to allow for post inflation pssssssssst...also because I prefer the solid feel to the spongy feel, but that's a personal thing


Maximum pressures on sidewalls have little to do with actual pressures used. I run around 18 FR and 22-25 R on a FS and HT, both 650B


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## Cyclist33 (1 Mar 2015)

yeah i mean i used to run my old ht at higher pressures eg 50 odd psi just wondering if this is awful practice or is it entirely up to me? also is it lower pressure at the front like you would on a road bike?

ta


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## Turbo Rider (1 Mar 2015)

T.M.H.N.E.T said:


> Maximum pressures on sidewalls have little to do with actual pressures used. I run around *18 FR and 22-25 R on a FS and HT, both 650B*



I don't know what those bits you said mean  All I know is they expressed a range so I went for it. Have I made a booboo?


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## T.M.H.N.E.T (1 Mar 2015)

Where are you riding it? That dictates pressure more than anything


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## Cyclist33 (1 Mar 2015)

T.M.H.N.E.T said:


> Where are you riding it? That dictates pressure more than anything



oh just light trail at the mo.


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## T.M.H.N.E.T (1 Mar 2015)

Turbo Rider said:


> I don't know what those bits you said mean  All I know is they expressed a range so I went for it. Have I made a booboo?


Not really.

FR - Front 
R - Rear 
650B or 27.5inch is one of 3 tyre sizes in MTBing. 26inch 27.5inch and 29inch
HT - Hard tail
FS - Full suspension



Cyclist33 said:


> oh just light trail at the mo.


If you're not launching it into rock gardens or anything running 30-35 if not slightly higher wouldn't be absurd.


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## Turbo Rider (1 Mar 2015)

T.M.H.N.E.T said:


> Not really.
> 
> FR - Front
> R - Rear
> ...



A, phew - learned something new as well - cheers for that


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## Racing roadkill (1 Mar 2015)

60 odd psi (4 to 5 bar) in the Cross trail pneumatics, 110 psi (7 or 8 bar) in the Roady pneumatics.


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## Pale Rider (1 Mar 2015)

I'm a biggish lad, so 55-60psi in the back of the new Cannondale MTB and about 10psi less in the front.

The shop sent it out lower than that, but I detected some squirm from the back on hard surfaces.


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## Slioch (1 Mar 2015)

I've got two sets of wheels/tyres for my MTB which I swap about depending on what I'm doing.

90% of the time I'm on road and/or gentle tracks, and I've got a non-knobbly (smooth rolling) set of tyres which I run at 60psi

I've then got a set of full knobblies which I use for serious offroad stuff/trail riding/snow etc. I generally run these between 30 - 50 psi depending on conditions.


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## razer17 (1 Mar 2015)

I run mine at 40psi, but I'll probably do some experimenting when I get a new bike to see what the best pressure is.

I run my road tyres as close to the max psi as possible, about 120 I think, since I'm a heavier rider.


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## Cubist (1 Mar 2015)

25 fr 30 rear on both bikes, HT and FS. HT is 26x2.25, FS is 26x2.4. Both bikes have tubeless Nobby Nic Snakeskins. I'm 16 stone plus.


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## Cubist (1 Mar 2015)

Pale Rider said:


> I'm a biggish lad, so 55-60psi in the back of the new Cannondale MTB and about 10psi less in the front.
> 
> The shop sent it out lower than that, but I detected some squirm from the back on hard surfaces.


You'll be skipping about on hard surfaces, and losing grip on hardpack stuff...... you may detect a bit of squirm, but the tyres won't be working with your suspension at those sort of pressures. Unless you're permanently on tarmac fully loaded, try dropping a few psi at a time and see how much your grip improves. The tyre knobs need to be able to conform to the trail, and much more than 40 psi won't let them do that.


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## Pale Rider (1 Mar 2015)

Cubist said:


> You'll be skipping about on hard surfaces, and losing grip on hardpack stuff...... you may detect a bit of squirm, but the tyres won't be working with your suspension at those sort of pressures. Unless you're permanently on tarmac fully loaded, try dropping a few psi at a time and see how much your grip improves. The tyre knobs need to be able to conform to the trail, and much more than 40 psi won't let them do that.



Thanks for that, I did wonder if I'd been a bit over-enthusiastic with the track pump.


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## mrbikerboy73 (1 Mar 2015)

I run 25-30 Front and 30-35 rear on a full-sus MTB. I only weigh 10.5 stone so anything more and there's not a lot of grip TBH.


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## Justinslow (1 Mar 2015)

There must be a compromise between rolling resistance and grip depending on the surface being ridden, therefore adjust pressure accordingly!


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## I like Skol (1 Mar 2015)

Turbo Rider said:


> Check the sides of your tires. My road bike tires vary between 80PSI and 115PSI and I keep them at 110PSI to allow for post inflation pssssssssst...also because I prefer the solid feel to the spongy feel, but that's a personal thing


As has already been pointed out MTB Vs road bike pressures are two very different beasts.



Cubist said:


> 25 fr 30 rear on both bikes, .........


Jeez, at those pressures I would be stopping with pinch punctures several times a ride! I run about 40Psi Fr and 45Psi Rr on my hardtail (14.5st & 26x2.1") and still get the occasional snakebite when hammering down rocky stuff (Like the Hayfield side of Jacobs Ladder recently ). I have wondered about tubeless as for me I think 5-10 Psi less is optimal for comfort, grip and handling but if I run lower pressures wouldn't I be damaging rims even though might not be getting flats?


Cubist said:


> You'll be skipping about on hard surfaces, and losing grip on hardpack stuff...... you may detect a bit of squirm, but the tyres won't be working with......... much more than 40 psi won't let them do that.


I don't suffer too much, as you know


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## Cyclist33 (2 Mar 2015)

Thanks for all responses, yes if I could clarify it was only MTB pressures I was enquiring about, hence why I posted in the MTB forum..!

Stu


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## Cubist (2 Mar 2015)

I like Skol said:


> As has already been pointed out MTB Vs road bike pressures are two very different beasts.
> 
> 
> Jeez, at those pressures I would be stopping with pinch punctures several times a ride! I run about 40Psi Fr and 45Psi Rr on my hardtail (14.5st & 26x2.1") and still get the occasional snakebite when hammering down rocky stuff (Like the Hayfield side of Jacobs Ladder recently ). I have wondered about tubeless as for me I think 5-10 Psi less is optimal for comfort, grip and handling but if I run lower pressures wouldn't I be damaging rims even though might not be getting flats?
> ...


Those are on 2.1s though. A wider higher volume tyre run tubeless will make a huge difference to grip and prevent you dinging your rim. (ooer etc.) Even with a 2.1 it'll take a pretty catastrophic hit to smack the ri.


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## Crackle (2 Mar 2015)

I used to ride my old 26" Velociraptors (2.1) at 40 because anything below 35 felt like I was riding with a puncture but they were really square profile tyres, absolutely awful on the road but great off.

The 29er Nobby Nics (2.25) I have on this bike run well for me at 25 to 30 psi. Over 30 psi and the the wtyres start to skit alarmingly on a hard gravely surface. I've run them as low as 20 but as yet I didn't feel any benefit from that but certainly no hindrance either. Much better tyres on the road too than the old Velociraptors.


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## Jody (3 Mar 2015)

mrbikerboy73 said:


> I run 25-30 Front and 30-35 rear on a full-sus MTB. I only weigh 10.5 stone so anything more and there's not a lot of grip TBH.



This ^ plus a bit of additional weight round the mid rift. Tubed wheels would be 30+ and for canal paths etc would be 45-50


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## GrumpyGregry (3 Mar 2015)

Pale Rider said:


> I'm a biggish lad, so 55-60psi in the back of the new Cannondale MTB and about 10psi less in the front.
> 
> The shop sent it out lower than that, but I detected some squirm from the back on hard surfaces.


about 10psi less than this works for me.


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## bridgy (3 Mar 2015)

This MTB tyre pressure calculator might be useful - http://mtb.ubiqyou.com/


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## Motozulu (3 Mar 2015)

Blimey - I'm a bit of a fat git at over 14 stone and I run (tubeless) 29 rear and 27 front, grip is spot on at that and not too draggy for me.


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## Jody (3 Mar 2015)

bridgy said:


> This MTB tyre pressure calculator might be useful - http://mtb.ubiqyou.com/



Good link! Reckons I should be running 29F and 31r. Tend to run the rear about 5PSI higher so the rear lets go first.


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