Tyre pressures

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tbuckland4
Posts: 16
Joined: 11 Aug 2020, 4:09pm

Tyre pressures

Post by tbuckland4 »

Hi everyone

This question has probably been asked 100 times, but what pressures do people run on their MTB tyres?

I came back to cycling after a long break just a couple of years ago and have only been riding off road since February so I’m still learning.

I’m riding a Cannondale Trail 4 hard tail with 29” WTB tyres with tubes. The tyres recommend between 35 and 65 psi. I initially opted for around 45-50 psi on each which was a pretty firm ride.

I’ve read of people running fairly low pressures in their tyres - below 20 psi - although they may be using tubeless tyres.

I imagine it would be more comfortable to reduce the pressures but I obviously don’t want the wheels to bottom out if I hit something. I’m mostly riding gravel trails and some forest paths.
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squeaker
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Location: Sussex

Re: Tyre pressures

Post by squeaker »

WTB NineLine tyres come in 2" and 2.25" widths - I'd run 40-45psi on the rear, 35-40psi front with the 2" tyre. (Yes, tubeless can be run softer as no pinch punctures ;) ) Usual advice seems to be reduce pressure until you start getting pinch punctures, then go up a bit 'till they stop occurring...
"42"
DevonDamo
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Joined: 24 May 2011, 1:42am

Re: Tyre pressures

Post by DevonDamo »

tbuckland4 wrote: 28 Aug 2021, 8:37amThis question has probably been asked 100 times, but what pressures do people run on their MTB tyres?
The answer to that question entirely depends on what you intend to do with the bike. For riding very fast on difficult terrain - especially fast, loose, flat turns - the received wisdom is to use the very low pressures you mention. People often go tubeless and/or install those foam inserts to allow them to run their pressures as low as possible without pinch-puncturing their tubes or damaging their rims.

However, not everyone agrees with the above approach. The most popular mountain biking YouTuber is Sam Pilgrim and he famously runs his tyres at around 60psi with tubes and is still right up there with the best when it comes to cornering fast on poor surfaces. His reasons for doing this are that he does a lot of extremely big jumps onto hard surfaces so he needs a lot of pressure to protect his wheels/tubes, plus he doesn't like the way tyres squirm at low pressure. You'll also find it's possible to 'create' traction round corners by pumping your weight down on the tyres as you apex the turn and this is how people like Sam Pilgrim do their miraculously fast turns on the least-grippy surfaces imaginable.

So the choice on which pressure you go for is a case of who you listen to. For what it's worth, my experience has been that (contrary to what YouTube told me) setting an exact tyre pressure really hasn't been the important factor in cornering: it pales into insignificance when it comes to getting the technique right. By learning how to get the bike leaned right over with the side-knobbles effectively engaged with my body weight driving them down into the ground and my weight distributed appropriately between front and back wheels for the situation, I've massively increased my ability to corner on loose surfaces. I really don't pay much attention to my tyre pressures but I think I have something like 30 in the back and 25 in the front.

(Obviously, if you were riding on the road, then you'd want them as hard as you can get away with, and preferably slicks - but I see from your post history that that's not the case.)

Edit: I've just clicked that your main concern is comfort. Therefore the explanation of pressure-choices above is not that relevant to you, other than explaining why there is so much concern out there about keeping tyre pressures low. That advice is basically aimed at people doing dynamic stuff on their bikes which is usually standing up with the saddle dropped out of the way and all the body weight going through their feet. If you're riding around trails sat down, but finding it a bit uncomfortable, then perhaps first get a bit of advice on saddle choice and adjustment for comfort and also check whether you can fit a fatter back tyre. Then it's just a matter of lowering the pressure until you find the sweet spot between being too firm/uncomfortable and being too soft/squirmy/slow. If you find this sweet spot is so low that it's risking pinch-punctures, you could try those foam inserts or converting to tubeless is very straightforward provided your rims will take it. I doubt you'd want to go that low for riding round gravel and forest paths though - the 30psi that I use in my back tyre should be more than squashy enough for comfortably riding whilst seated and I've never had any puncture problems despite smashing it over rocks and roots.
tbuckland4
Posts: 16
Joined: 11 Aug 2020, 4:09pm

Re: Tyre pressures

Post by tbuckland4 »

Thanks both for your advice!

I’ll reduce the pressures in both and see how I get on. As I said I’m still pretty green when it comes to off road (and cycling in general if I’m honest) so I’m sure there’ll be some trial and error but it’s good to have a base line to work from.
DevonDamo
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Joined: 24 May 2011, 1:42am

Re: Tyre pressures

Post by DevonDamo »

tbuckland4 wrote: 29 Aug 2021, 9:23pm Thanks both for your advice!

I’ll reduce the pressures in both and see how I get on. As I said I’m still pretty green when it comes to off road (and cycling in general if I’m honest) so I’m sure there’ll be some trial and error but it’s good to have a base line to work from.
Another thought, which I ought to have suggested above. Having your tyres soft enough for seated comfort will mean you're faced with higher rolling resistance which isn't necessary if you're cruising around forest tracks and gravel. How about getting into the habit of standing up and using your legs as shock absorbers when you're doing the high speed bumpy stuff which is likely to rattle your fillings out? (A dropper post makes this easier, but you can still get your bum off the seat without one.) Bumpy stuff isn't usually a problem when you're climbing at slower speeds, so you'd still be able to remain seated whilst pedalling. That way, you'd be able to leave your pressures higher which will make for less effort and better handling generally. Aim to be positioned so all your weight is going through your feet, with your pedals at 3 and 9 o'clock and a negligible amount of pressure through your bars for steering. I know I'm teaching granny to suck eggs here, but it's what I needed to hear a couple of years ago, when I first started going off road and wasn't aware there was this whole set of techniques which could transform the ride and handling.
offroader
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Joined: 18 Dec 2018, 4:47pm

Re: Tyre pressures

Post by offroader »

With absolutely no disrespect to other posters on this thread.....

Treat any advice bandied about by anyone, most definitely including my rambling, with a giant pinch of salt. Added to at least half a bucket of salt

For example I see numbers quoted above but I see no mention of your weight which obviously has a significant role to play
Plus there's no magic pressure in my experience.

In my racing skeleton days I would ride Henry Coe state park at least 10psi harder than Nisene Marks forest because it's rocky and remote and a seriously damaged tyre would have been a major problem. Same rider, same bike, same tyres, different result.
These days, 20 years later and 12kg more cuddley I'd choose different pressures again were I still living there. Same rider, same bike, different tyres, different result.
I still change tyre pressure now if I'm venturing into the Purbecks or into the New Forest as again they're very different days out

The only thing that's ever been consistent is my formula to guesstimate a starting pressure (psi) :- rider weight (kg) / tire width(inches). From there adjust by feel on your usual routes
dodgy
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Joined: 31 Dec 2010, 5:53pm

Re: Tyre pressures

Post by dodgy »

When cycling on road to an off road route do people generally ride in at higher tyre pressures, then let some air out for the trail section and then pump up again for the return? Or is that too much faff?
DevonDamo
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Joined: 24 May 2011, 1:42am

Re: Tyre pressures

Post by DevonDamo »

dodgy wrote: 31 Aug 2021, 12:49pmWhen cycling on road to an off road route do people generally ride in at higher tyre pressures, then let some air out for the trail section and then pump up again for the return? Or is that too much faff?
Too much faff for me, but I've got 2 mountain bikes which I only ever use for actual trail riding and other more suitable bikes for on-road use. I do ride my mountain bikes on the road a bit to get to the trails, but as explained above, I don't have my tyres at the very low pressures that some use on trails, and I can live with them for 10 miles or so on the road. I know of one guy who did claim he'd change his tyre pressures between road use and trail use, but he's a lazy git and I bet he's never actually bothered in practice.
tenbikes
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Joined: 11 Jan 2009, 6:41pm

Re: Tyre pressures

Post by tenbikes »

I tend not to fiddle with tyre pressures much in summer, but in winter on my fat bike in snow I alter pressures quite a bit. 6psi for the ride to the trail head, 3-4 psi if hard and icy, and sub 3 psi when I get higher into the soft stuff. The difference between 3psi and 2.5 psi is astonishing! And yes, I use a low pressure gauge which is, I hope, consistent!

In summer I will alter pressure for the day/location as required. Pressures depend on tyre volume, which in my case varies between 26x1 and 29x3, and 26x4 and 26x4.8 / 5

Tyres are a mix of tube and tubeless.
mumbojumbo
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Joined: 1 Aug 2018, 8:18pm

Re: Tyre pressures

Post by mumbojumbo »

The ideal pressure is determined by terrain and so must be varied from place to place, rather like the time taken to cook a piece of meat-slow for trotters and quick for kidney and liver.
tenbikes
Posts: 463
Joined: 11 Jan 2009, 6:41pm

Re: Tyre pressures

Post by tenbikes »

Could you give me a vegan equivalent please so that I can fully grasp your point :) :D
DevonDamo
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Joined: 24 May 2011, 1:42am

Re: Tyre pressures

Post by DevonDamo »

mumbojumbo wrote: 4 Sep 2021, 10:45am The ideal pressure is determined by terrain and so must be varied from place to place, rather like the time taken to cook a piece of meat-slow for trotters and quick for kidney and liver.
I'm not having that. If you cook liver quickly, it's going to by chewy, and you'll probably lose your front tyre on the first flat corner and end up with a frying pan's worth of hot fat all over you.
mumbojumbo
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Joined: 1 Aug 2018, 8:18pm

Re: Tyre pressures

Post by mumbojumbo »

I expect you imagine I eat ox liver-in fact I prefer pigs' which has been steeped in Balsamic,sliced and cooked in a hot wok.
peetee
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Re: Tyre pressures

Post by peetee »

Only you can answer that. As mentioned previously, weight, terrain, comfort, speed, traction and the capability of the tyre all have a bearing.
It’s a case of trial and error.
The older I get the more I’m inclined to act my shoe size, not my age.
CinnabarMoth
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Joined: 5 Nov 2021, 7:46am

Re: Tyre pressures

Post by CinnabarMoth »

tbuckland4 wrote: 29 Aug 2021, 9:23pm Thanks both for your advice!

I’ll reduce the pressures in both and see how I get on. As I said I’m still pretty green when it comes to off road (and cycling in general if I’m honest) so I’m sure there’ll be some trial and error but it’s good to have a base line to work from.
I use my mtb much the same way I use walking boots and running shoes, another way of exploring country trails at my sedate pace.
The chalk tracks where I live can shake the bike up pretty bad , I find 40psi on 2.35'' tyres softens things quite nicely and are not too soft for the road sections connecting bridleways and byeways.
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