MTB Specific: What Tyre Pressures

[traaidmark]

FWIW the stock Nobby Nics on the trance are the lowest quality casing, and will be likely to squirm. 

 

At above 100kg I'd seriously advise something with a stronger sidewall, like Schwalbe's Super Gravity casing (Rock Razor would be a good choice) or Spaz's Grid casing (Slaughter 2.35 is a good option) or Maxxis's Double Down casing. It will seriously reduce the amount of roll & squirm you suffer from, and will be more hardy as well. 

 

Onza's FRC casing is also the best to go for.

 

They will all be heavier than the lightweight options you're most likely used to, but don't be afraid. You're 100 plus KG - an extra 150g on a tyre will NOT make a diffference to you. 

Ah mate thanks. I figured they were good tires, so even though I really do want to go tubeless (previous bike was tubeless), I thought I might as well ride these tires out first. Now, it might just be worth the upgrade sooner.

 

Yeah, weight does not matter that much to me. I'm always going to be slow on the ups, not matter how lightweight the gear. 

 

Thanks for the direction, this makes a LOT of sense.

[dasilvarsa]

Hey guys, I came here to ask a question about exactly this, and luckily saw this thread before posting.

 

I weigh roughly 108kg (2m tall), and I'm having such a *** time with my tires. I recently got the giant trance, and it comes with pretty bulky tires (way more bulky than I'm used to).

 

I pump them to 2bar generally (anything lower on tar and it's like riding on a spunge), and it rides fairly well like that. Until I get to a steeper climb...

 

When climbing the rear wheel rides like it's flat. Makes noise, slurrps around. Feels like it moves around when I shift my weight.

 

Thing is, took it out to meerendal yesterday for the first time, and kept to 2bar, and it rode VERY nicely on the dirt. Singletracks were awesome, but I felt a bit iffy in corners and berms, feeling like it might slide out on me. Climbing up stairway to heaven I had the same climbing issue where tire felt / looked flat. 

 

Question is:

 

Am I just being scaredy-cat in corners, and I can safely increase the bars on the rear?

 

I run: Schwalbe Nobby nics 2.25 650B Tubed (still need to do tubeless)

 

The tubes pump up very thick outside of the tire, and always feel soft if that helps at all.

Try to increase the rear tyre pressure to 2.3 or 2.4 (2.6 recommended) (2 bar is too low for 108Kg) on any tyre tubes or tubeless. I'm 90 kg and I like 2.1 @ the back.

When climbing your weight is shifting to the back needing more air pressure.

650b needs a little more pressure when compared to 29 inch.

http://mtb.ubiqyou.com

 

FRONT tyre pressure

35psi (31÷40)

2.4bar (2.13÷2.75)

REAR tyre pressure

38psi (34÷42)

2.6bar (2.34÷2.89)

Edited December 16, 2017 by dasilvarsa

[steven l]

as a stating point to set pressure

 

your weight in pounds divide by 7

front wheel  minus 1 in psi

rear wheel plus 1 in psi

example

100 kg = 220 pounds

220/7=31.42psi

then plus 1 for rear and minus 1 for front .

 

the softer the conditions the softer the pressure

[s14phoenix]

as a stating point to set pressure

 

your weight in pounds divide by 7

front wheel  minus 1 in psi

rear wheel plus 1 in psi

example

100 kg = 220 pounds

220/7=31.42psi

then plus 1 for rear and minus 1 for front .

 

the softer the conditions the softer the pressure

 

Seems soft... but close - rear seems quite soft front seems ok.

[Headshot]

How long is a piece of string...

[LOCO4360]

It all depends on whether tubes or tubeless. With tubes go a bit higher maybe around 2bar but tubeless I run 1.7 rear and 1.5 front for better grip and when at the jump or pump track take it up slightly. You'll never have great grip with super high pressures.

[cadenceblur]

indeed, at 100kg I am running 1.6bar up front and 1.9 at the back.

Wider rims 

Haven't had any issues.

Pressures confirmed with digital guage.

[Wimmas]

I am going crazy regarding tyre pressure. I used to cycle a couple of years ago and started again recently. I got a 29er with the standard 2.2 Maxxis Ikons (Non TR / EXO etc). Did not have a pump with a pressure gauge, just used instinct with pushing down on the tyre with my thumb like in the old days. My logic tells me I need to at least be able to push the tyre in slightly with my thumb, then it's not too hard.

 

Last weekend went riding at Hennops. Front tyre sidewall tore about 1.5 - 2cm from a sharp rock. I initially thought my pressure was too high. Ordered a new Maxxis Ikon TR EXO (Better than the standard tyres) and a floor pump with a pressure gauge. Cleaned the rim and installed the new tyre with some Stan's sealant. Started out by pumping to 2 bar. 

 

When I felt the tyre by hand, it felt very hard vs what I rode last weekend when I tore my sidewall. Got me thinking now that maybe the tyre was not pumped too hard, I just maybe had bad luck. Or could it be the brand new pump has an incorrect pressure gauge? (Seems highly unlikely).

 

I weigh around 83 - 84kg. 

 

Guess what I am asking, when you feel the tyre by hand, should it feel hard or should you easily be able to push it in slightly?

[Dicky DQ]

I am going crazy regarding tyre pressure. I used to cycle a couple of years ago and started again recently. I got a 29er with the standard 2.2 Maxxis Ikons (Non TR / EXO etc). Did not have a pump with a pressure gauge, just used instinct with pushing down on the tyre with my thumb like in the old days. My logic tells me I need to at least be able to push the tyre in slightly with my thumb, then it's not too hard.

 

Last weekend went riding at Hennops. Front tyre sidewall tore about 1.5 - 2cm from a sharp rock. I initially thought my pressure was too high. Ordered a new Maxxis Ikon TR EXO (Better than the standard tyres) and a floor pump with a pressure gauge. Cleaned the rim and installed the new tyre with some Stan's sealant. Started out by pumping to 2 bar.

 

When I felt the tyre by hand, it felt very hard vs what I rode last weekend when I tore my sidewall. Got me thinking now that maybe the tyre was not pumped too hard, I just maybe had bad luck. Or could it be the brand new pump has an incorrect pressure gauge? (Seems highly unlikely).

 

I weigh around 83 - 84kg.

 

Guess what I am asking, when you feel the tyre by hand, should it feel hard or should you easily be able to push it in slightly?

Well I am now 205 to 106 kg running Zippering tyres and have dropped pressure for riding tech single-track to 1.3 bar front and 1.5 bar back. Yes if you ride rocky climbs seated and heavy I bump through a bit. But just need to think and right lighter.

 

The winn is so much better going down you cannot compare.

 

Riding ztr crest normal width rim and 2.2 tyre

[Captain Fastbastard Mayhem]

I am going crazy regarding tyre pressure. I used to cycle a couple of years ago and started again recently. I got a 29er with the standard 2.2 Maxxis Ikons (Non TR / EXO etc). Did not have a pump with a pressure gauge, just used instinct with pushing down on the tyre with my thumb like in the old days. My logic tells me I need to at least be able to push the tyre in slightly with my thumb, then it's not too hard.

 

Last weekend went riding at Hennops. Front tyre sidewall tore about 1.5 - 2cm from a sharp rock. I initially thought my pressure was too high. Ordered a new Maxxis Ikon TR EXO (Better than the standard tyres) and a floor pump with a pressure gauge. Cleaned the rim and installed the new tyre with some Stan's sealant. Started out by pumping to 2 bar.

 

When I felt the tyre by hand, it felt very hard vs what I rode last weekend when I tore my sidewall. Got me thinking now that maybe the tyre was not pumped too hard, I just maybe had bad luck. Or could it be the brand new pump has an incorrect pressure gauge? (Seems highly unlikely).

 

I weigh around 83 - 84kg.

 

Guess what I am asking, when you feel the tyre by hand, should it feel hard or should you easily be able to push it in slightly?

Yes, 31psi (2 bar) is too high. And those standard Maxxis sidewalls are like paper. So thin.

 

Get it to around 25psi and play from there. What I generally do is get to 25psi, and if you're not dinging your rims on every rock / root or rolling & squirming the tyre under load, reduce the pressure a bit. A couple of rim-strikes on BIG hits isn't a problem. As you reduce the pressure and play a bit you'll find a sweet spot for grip, sidewall stiffness and roll. Where that is will be determined by a combination of things, like sidewall strength, sidewall casing, tyre width, rim width, riding style and the trails you ride. 

 

The "thumb test" is a reasonable starting point, but doesn't allow for different levels of hand-strength, which can vary hugely. 

Edited January 12, 2019 by Captain Fatbastard Mayhem

[Wimmas]

Thanks for the advice!

 

I also think it's a personal thing and trial and error, as well as other factors.

 

Played around with the bike yesterday here in my complex and went to Hennops again today. Ended up riding on the following pressure:

 

Rear - 1.5 bar Maxxis Ikon 2.2 (Standard tyre)

Front - 1.3 bar Maxxis Ikon 2.2 TR EXO 

 

Grip was great, rims did not touch a rock / root once and neither did tyre feel like it was going to come off the rim. Think this is my sweet spot.

 

Those pressures might be way out due to the unreliability of these pumps we use, but as long as my pump gives me those pressures on the respective tyres I am happy.

[LOCO4360]

It's really a rider specific thing but what really helps with a guide is an app called TyreWiz you can download off the Google appstore for free. Take your weight, weight of the bike and Tyre width and size and gives you an indication. Im running 27.5 2.30 DHF/Aggressor at 1.5/1.6 bar and it's perfect

[Craig Armstrong]

Jirrre I don't know how you guys have any grip on such high pressures. I run my tires at 1.1 bar. Any more than that and I feel like I'm on ice skates.

Mind you, I only started running so low when I went onto wide rims. Don't know what the science is behind it, but the wider the tire, the harder the tires feel at the same pressure.

I know wider tires allow lower pressures due to having more support against the tire rolling sideways, but even aside from that, the tires just feel harder on wider tires.

This may all be in my head though, but it's just my experience

[RocknRolla]

Wider rims equal lower pressure. Think it has to do with volume, but I'm not sure about the sciency stuff..

 

I do however run slightly higher pressure on rocky terrain due to fear of pinch-flat and rim strikes. But it took me some getting used to the idea of lower pressure on wider rims when inflating.

Hardest I go now will be 1.5 at the rear, maybe 1.8 if it's dirt road ride over a longer distance. 

[Captain Fastbastard Mayhem]

Jirrre I don't know how you guys have any grip on such high pressures. I run my tires at 1.1 bar. Any more than that and I feel like I'm on ice skates.

Mind you, I only started running so low when I went onto wide rims. Don't know what the science is behind it, but the wider the tire, the harder the tires feel at the same pressure.

I know wider tires allow lower pressures due to having more support against the tire rolling sideways, but even aside from that, the tires just feel harder on wider tires.

This may all be in my head though, but it's just my experience

Simply put, it's a higher volume unit due to a wider base. Wider base also supports the sidewalls better (to a point) and gives the tyre a bit more lateral rigidity. 

[DieselnDust]

Jirrre I don't know how you guys have any grip on such high pressures. I run my tires at 1.1 bar. Any more than that and I feel like I'm on ice skates.

Mind you, I only started running so low when I went onto wide rims. Don't know what the science is behind it, but the wider the tire, the harder the tires feel at the same pressure.

I know wider tires allow lower pressures due to having more support against the tire rolling sideways, but even aside from that, the tires just feel harder on wider tires.

This may all be in my head though, but it's just my experience.

 

P=F/A

 

F= P.A

 

Where

P = Pressure

F= Force

A= area

 

So a wider tyre has more surface area with the same pressure hence you feel more resisting force i.e. the tyre feels harder.

 

 

Wider isn't always better as it reduces the change in diameter of the tyre as you lean the bike over. What it does offer is more support when running low pressures and this offsets the change in diameter problem and results in a more controllable feeling bike (to a point and dependant on the choice of components involved)