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I'm 5'10" 95kgs. I use an MTB for city commute (I know I should've gone with a hybrid instead).

The tires recommend a max pressure of 50 PSI. I'm wondering if setting the rear tire at 50 PSI could result in a blowout considering my weight.

How much pressure do you recommend for the front and back tires?

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    For commuting, assuming mainly paved you probably want to go slightly higher pressure than riding off road. Your really the only one that can tell for sure but would think 35-40 psi should be plenty
    – Hursey
    Sep 16, 2022 at 10:30
  • Are the tires knobby or slicks? If you're commuting on paved surfaces, you really want slicks. Sep 16, 2022 at 12:55
  • Thanks Andrew. My tires are semi-knobby
    – pb_ng
    Sep 16, 2022 at 15:27
  • @Hursey - slightly higher than off road - I ride off road at about 18-20psi. 50 is too high for a modern MTB tire (e.g. 2x2.3). 50 psi was considered right on road for 26/1.75 in the day, but people have realized that low rolling resistance comes for things other than increased tire pressure.
    – mattnz
    Sep 16, 2022 at 20:34

4 Answers 4

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Blowout isn't affected by your weight. Blowouts happen when you put too much pressure into the tire. It generally happens during inflation, it's far more rare to have a pressure blowout during riding the bike, although on long mountain descents it's possible that rim brakes heat the rim enough to cause a heat blowout.

Weight on a tire doesn't increase its pressure markedly, contrary to what you might believe.

So if you want to have 50 PSI tires when loaded, then you should inflate to 50 PSI when unloaded. Unloaded pressure is a very good approximation for loaded pressure.

So the question is then, is 50 PSI good for 60mm tires? I don't have any bike with 60mm tires. I only have 120mm fatbike tires (7 PSI) and 28mm road bike tires (100 PSI). My weight is 110 kg, slightly more than yours.

One way of thinking about tire pressure is to inflate to a pressure inversely proportional to tire width1. So if 28mm road bike tires are inflated to 100 PSI, then 60mm tires should be inflated to 47 PSI, or about 50 PSI. However, this applies only if you ride the bike in similar conditions with dissimilar tire width.

The 28mm road bike tires inflated to 100 PSI are intended for riding on pavement. They are hard -- really hard, every bump on the road is felt. 60mm tires inflated to 50 PSI would feel about the same. Inflating 60mm tires to 50 PSI would only make sense if they are slick tires with no tread pattern and are only used on pavement.

The nice thing about wide tires is that (1) you don't necessarily need to follow the "tire pressure is inversely proportional to tire width" rule because you can get away with really low pressures with no risk of pinch flats, and (2) the low pressures allow usage on soft ground and snow.

If you use your MTB as a MTB or as a snow bike, then no, don't inflate to 50 PSI. If you use it as a road bike, then perhaps you could (although you could consider lower pressures too then), but you'll want to use only slick tires in that case, not treaded MTB tires.

Why my fatbike has ridiculously low (7 PSI) pressures, then? It's because I can ride it easily over any kind of snow then. The 7 PSI very much deviates from the "pressure inversely proportional to tire width" rule, but it's not used in same conditions as road bikes are.


(1): Why inversely proportional to width and not inversely proportional to width squared which might make more sense unit-wise: actually it's inversely proportional to width and inversely proportional to tire diameter, and tire diameter is usually constant so that can be forgotten. Of course if you compare Brompton pressures to road bike pressures, you'll find Brompton uses surprisingly large pressures for a given tire width, but that's due to the small tire diameter.

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How wide are your tyres? 50 PSI (3.4bar) is a lot for tyres which are probably wider than 55mm. There is a point where increasing pressure doesn’t lower rolling resistance but instead increases it.

This calculator calculates optimum pressure for lowest losses and even for 55mm tyres and 110kg total weight on worn pavement it only says 1.65 bar (24PSI): https://silcavelo.eu/pages/sppc-form

Edit: I should add that – obviously – comfort suffers massively if you ride high pressures, especially on rough surfaces. You basically lose all the benefits of having wide tyres in the first place. For comfort it can make sense to go below the pressure recommended by the calculator above. For off-road usage it’s normal to go as low as possible.

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  • The tires are 26" x 2.35" (59.69mm) Thanks
    – pb_ng
    Sep 16, 2022 at 12:27
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    That calculator optimizes for minimum rolling resistance. I have a feeling that in some contexts, more casual cyclists may want to go lower than recommended. For me on gravel, I feel like my recommended pressure (~40 PSI at about 140lb) is a few PSI too high in terms of comfort.
    – Weiwen Ng
    Sep 16, 2022 at 12:38
  • Yes, dropping pressure a bit often results in a small percent decrease in rolling resistance at a massive increase on comfort which translates to perception of more speed.
    – mattnz
    Sep 16, 2022 at 20:39
  • That calculator does not optimize for minimum resistance. I am perfectly aware of that for me 3.5 bar gives much less resistance than they recommend 1.5.
    – nightrider
    Sep 17, 2022 at 9:34
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    @nightrider: How did you measure/compare? On what surface? I recommend reading this blog article: silcavelo.eu/blogs/silca/… It clearly shows that there is a point where increasing the pressure further doesn’t lead to a reduced rolling resistance but rather increases it, probably because the whole bike+rider starts to vibrate which requires more energy than deforming only the tyre. On rough ground this happens at surprisingly low pressures.
    – Michael
    Sep 17, 2022 at 9:48
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This is 3.45 bar. Look for the maximum rating that is often printed on the tire.

On my rear 27.5 x 2.40 tire it is printed "4 bar max", on another that is different it stands "3.5 bar max" so why not. It shakes a little more but there is less rolling resistance.

I asked myself questions here if claims that low pressure results less or even comparable rolling resistance are based on any measurement data. This have not been measured for MTB or, if measured, have not been published.

Try various pressures up till that the tire is rated for and then use what you liked the most. If it feels as the better ride, it is. Who else should decide this for you? This question is getting religious.

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When I first got back into riding, I found that running MTB tyres as high as I could get away with was a key to "fast" riding. It was almost like buying performance, or losing 5 kg straight off.

For me pressures were 55-60 psi, and speeds felt fast. I also chose "all-terrain" tread where the center strip is smooth and there are only small knobs on the outside. This allows for straight-ahead vertical riding to be essentially on slicks to minimise roar.

Can your tyres take it? Best thing to do is inflate the tyre to 60 PSI and then park it overnight. If its happy with that, then riding at 50 PSI should be fine.

Of course you have a spare tube and required tools/pump if it does puncture while riding, right ?

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