Currently weighing 125 kg, I got myself a BMC Alpenchallenge One to finally start exercising and lose weight. The bike is equipped with Continental Contact Speed tyres (700x35c). Maximum pressure is 85 PSI. Do you think I can and should inflate the tyres to this pressure? Or do I need to fear that the tyre takes damage due to my weight? I am a little bit concerned that the high pressure and weight might damage the tyre when it gets a little bumpier.

Also just had a flat tyre finding a small but pointy stone in it (riding at approx 60 PSI before). Could this have been avoided by higher pressure?

I think I am overall a little bit paranoid in terms of my bike. The system limit is a 120 KG and I am currently at 135-140 (bike + me). Anxious, thatI damage the bike or will have an accident…

3 Answers 3


It’s totally fine to use the maximum tyre pressure.

The only thing I’d worry about with high tyre pressures is if your rims are too narrow for the tyres you are using. Rim sidewalls can break when used with too wide tyres at higher pressure. It’s especially problematic if you have rim brakes and are wearing away the sidewall over time. But it looks like the Alpenchallenge has disc brakes and relatively wide rims, so no problem there.

I don’t think your puncture had anything to do with pressure. You could change to more puncture resistant tyres if it happens more often.

If you have punctures on opposing sides (called “snakebites”) and without any sharp object involvement it can be because of too low tyre pressure which causes you to “bottom out” and pinch the tube between tyre and rim (that’s why they are called pinch flats).

Your weight is indeed on the higher end for a “normal” bike. The thing which is most likely to break are spokes on the rear wheel. This is relatively harmless. A 32 spoke wheel won’t collapse with one or two broken spokes. But you should check your wheels regularly and look if they are still true (less than ±1mm side-to-side wobble of the rims). Try to go over bumps carefully. Lift your backside from the saddle and use your legs as shock absorbers.

The brakes could overheat on longer descents if you let them drag.

Edit: In my experience this tyre pressure calculator gives pretty good results: https://info.silca.cc/silca-professional-pressure-calculator For your 140kg system weight and 35mm tyre width it recommends a little over 4bar (60PSI), which is surprisingly low and I definitely wouldn’t go lower.

  • Michael, thanks for your long and detailed answer! The bike has disc brakes indeed. Regarding the tyre/rim combination: I hope that the manufacturer chose the right combination here. What do you exactly mean with my wheels being true and the side wobble? Just wiggling on the rear wheel and see if it moves too much? Regarding the pressure, I will go 10% below max just to be sure..
    – JZ9294
    Commented Jan 24, 2022 at 19:31
  • 2
    @JZ9294 You're fine at max. Tires are tested for double their rated max pressure, and I'd assume that rims are tested to the same level too (to match).
    – MaplePanda
    Commented Jan 24, 2022 at 20:31
  • 4
    True wheels are round wheels with straight edges. If you spin the wheel and it wobbles laterally as it goes round, it isn't 'true'. This can cause poorer breaking performance, a wobbly ride and increased risk of breaking the wheel. The spokes pull the rim towards the hub, and this uniform tension is what makes a wheel true and strong. Overloading or shocking the wheel can cause the spokes to break or weaken, and these breakages compromise the integrity of the wheel. Commented Jan 24, 2022 at 21:44
  • @JZ9294: Regarding true-ness/wobble: Lift the bike up, spin the wheels, look at the rim walls if there is side-to-side or up-and-down movement. If a spoke is loose or damaged the remaining spokes will pull to the other side and the wheel will be out of true. With rim brakes this was easy to check because the brake pads gave a good visual reference point and if the wheel was severely out of true they’d start rubbing at the worst points.
    – Michael
    Commented Jan 25, 2022 at 6:29
  • I'm a heavier rider, and I've noticed my 'spoke death' rate does notably increase when I'm running on high tyre pressures. Not individually an issue, but have had a couple of 'cascade' failures (multiple spokes going in close succession).
    – Sobrique
    Commented Jan 25, 2022 at 10:31

As a general rule, issues due to the total mass of the rider and equipment on the bike relating to tire pressure will be due to having the pressure too low, not too high. In such cases, you can end up with what is usually known either as a pinch flat or ‘snakebite’, resulting from pressure from the rims effectively puncturing the tire. This is why most bike tires usually have a minimum pressure rating in addition to a max.

In general, tire pressure should almost exclusively reflect the type of surfaces you are riding on, within the ratings for the tires (high pressures for solid and mostly smooth surfaces, low for loose or rough surfaces).

In terms of actual risk of damage due to overloading, the primary risk is increased stress on the spokes (especially on the back wheel, as that’s where most of the weight is on almost any bike), or possible long-term fatigue of joints on the (though the spokes will fail long before that becomes an issue). The biggest thing you can do to mitigate that (other than losing weight) is to be careful going over bumps. Stand out of the seat when doing so and use your legs as shock-absorbers (this will also, once you get used to it, probably be more comfortable than sitting in the saddle as well). Higher tire pressures can make this worse due to less cushioning, so you might consider running a bit below what you might otherwise run.

The other two major things to consider due to weight are increased break wear (more weight means more momentum, which in turn translates to more energy that you need to dump to bring the bike to a stop), and an increased risk of the wheels going out of true (due to increased horizontal loads while turning). Both are things that regular inspection and regular preventative maintenance can easily take care of though.

On the note of punctures, tire pressure usually does not matter much here. Lower pressures are less likely to result in less pointy objects embedding in the tire itself, but the practical impact of this is essentially nil.

If you are worried about the possibility of flats, there are a couple of options:

  • Carry some spare tubes and the tools you need to replace a tube on the side of the road.
  • Consider tire liners. Some bike accessory brands make plastic or fabric liners you can put inside your tires that will help protect against punctures. They’re generally decent at this and reasonably cheap, though they will add more weight to your wheels, can be finicky to install, and also marginally increase the risk of a pinch flat (because there is less space inside the tire for the tube).
  • Look into more puncture resistant tires. Continental Contact Speed tires are supposed to be pretty well reinforced, but you can find better. Just keep in mind that something very sharp and pointy like a nail or tack can still punch through in many cases, it will just take it longer to do so.
  • Look into ‘self-sealing’ tubes. These are a kind of halfway point between traditional tires and tubeless tires, consisting of an tube with tubeless sealant inside. The nice ones can be refilled just like a tubeless tire, the cheap ones can't but are much less expensive, either way you would need to replace tubes every couple of years.
  • Consider something like Tannus Armour. Just like self-sealing tubes are a kind of halfway point between traditional tires and tubeless, this is a halfway point between traditional tires and airless tires. The feel of the ride on these is distinctly different from a normal tube, but they will protect you from almost anything, and if a tube does rupture you can safely ride on a flat provided you don’t go too fast.
  • Consider just getting airless tires. These replace both the tube and the tire in most cases, and completely eliminate any risk of a flat. The downsides are that they wear out faster than regular tires or tubes, they are often a pain to install, and you lose the control of handling from tweaking tire pressure.

For hard paved surfaces. The more weight the more air pressure you should use, up to the printed limit. Lighter riders should generally reduce pressure below the rated max so they get the same deflection and ride characteristics. Changing the external weight on a wheel has little to no measurable effect on the air pressure. For soft surfaces a heavier rider should generally attempt to use a wider tire rather than higher pressure if practical. Even my old tractor calls for higher tire pressures when operated in a higher weight configuration, to reduce various damage caused by excess sidewall deflection.

(In highway speed tires there is also concern for heat build up from the material deflecting, mainly sidewall flex, sometimes called internal friction. In high speed uses many truck and tire manufacturers publish a chart with minimum pressures, which increase with weight and speed. Boeing and airbus jets use about 15bar/220psi with 16 tons on each tire.)

Assuming a given tire size, lower pressure means more deflection for a smoother ride, but more deflection is more internal friction. However higher pressure requires a thicker tire material which increases the internal friction for a given amount of deflection.

Contact area is determined by actual air pressure and weight on the wheel. Wider tires at a given pressure have the same contact area with the pavement as narrow tires, but the wide tires deflect less to achieve that contact area so they tend to have less rolling energy loss. (Wide tires have more aerodynamic loss, the dominant energy loss shifts from deflection to aerodynamic approximately 10-14mph, 16-22kph depending on design specifics.)

Heat makes a large difference in pressure, I have had tires pop while taking a break and laying the bicycle in the noon sun. (The tire bead stretched enough to come off of the rim in a small section and expose the tube, the tube is what actually popped. Those were very old style straight wall rims and I had set the tire at the maximum rated pressure for those rims during the cold morning.)

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