I'm looking to renew one of the tyre on my MTB as it's on a dying stage. I see some tyres those have 40 PSI tyre pressure level and some have 60 PSI. They are both 26x2.00 so it can't be about width. Why would one manufacturer suggest much lower tyre pressure than the other? Does that show they have bad quality tyres?
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Does it say if it's maximum or recommended pressure? Generally low pressure is good for off-road riding so high maximum pressure doesn't do much good and high recommended pressure implies that they aren't really for off-road riding.– ojsNov 20, 2021 at 9:22
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They recomment 40 PSI for all sizes of bicycle tyres; 16", 20", 26" and 28". I understand it is a superficial thing. It is sad for me that a manufacturer from my own country doesn't take their job seriously. They can never achieve anything with this mentality.– EnderNov 20, 2021 at 10:22
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What kind of riding do you do? It's an MTB, but are you riding on mountains or paved roads ?– Criggie ♦Nov 20, 2021 at 10:46
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Very likely those tubes are designed for different types of riding. Tubes designed for MTB usage tend to be closer to the 20-40 PSI range, hybrids tend to be closer to 40-60 PSI range, and ones designed for road usage tend to be in higher ranges (and track tires have eye-poppingly high ratings). The rating though is (usually) just a matter of what the tubes are tested for unless it’s a very high pressure tube.– Austin HemmelgarnNov 20, 2021 at 23:04
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1@Ender Yes - I would expect that road riding would be easier with higher pressures (to a point) Off road riding requires a larger contact patch/area. Don't go so hard that the tyre is a rock, need to find the happy medium. But none of this is related to quality. Consider joining Bicycles Chat– Criggie ♦Nov 21, 2021 at 10:01
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2 Answers
No, the relationship you suggest is not the case. The opposite is almost true, but not in all cases.
The use cases where a 2" or 50mm wide tire should be ridden at 60 psi exist but are relatively uncommon. An example of such an application would be a cargo e-bike, tandem, or other very heavily loaded bike, or the disciplines that involve extreme drops. But in a lot of other cases where someone fills a 2" tire to that kind of pressure just to ride around casually, they're making the ride unnecessarily harsh and bumpy for no benefit.
Limits to pressure suggest a lightweight and supple casing, which is desirable as long as it's balanced well with durability for the application. High pressure limits suggest a very strong or even overbuilt casing, which again has applications where it's desirable, but not usually in performance-oriented riding other than the gravity disciplines.
So, in other words, there are some good 26x2.0 tires that say max 60 or 65, such as a trekking/cargo/touring/tandem/commute/ebike tire where the emphasis is on toughness and therefore the casing can handle that pressure whether it's useful or not. But meanwhile, many bad or mediocre tires have high nominal max pressure ratings simply because they're cheap and heavy.
The other thing about the relationship between quality, strength, and nominal max pressure is manufacturers have choices to make about how conservative to be in the number they make up. When casings do bulge or warp from pressure it's usually not all at once, but happens over time and is a result of load, pressure, rim width, environmental conditions, what kind of minor damage they're picking up, etc. The question then arises of whether they turn to rigorous testing, the lawyers, or the dartboard to actually come up with the number. All are possible but since we're talking about the bike business, it's probably usually lawyers and dartboard competing for first place and testing third, in order of likelihood or share of influence. But that said, lighter tires are more apt to show a max pressure that is closer to a real hard limit and possibly even pushing it, because light bike parts do their thing by flying closer to the sun.
answered Nov 20, 2021 at 9:34
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2Just commenting for interest’s sake: I wonder if track tires are the edge case where quality might be correlated with max pressure. We know that on smooth tracks, higher pressure = lower RR without worrying about impedance losses (from going over non-smooth surfaces). We know that track racers run what everyone else would consider absurd pressures. Nov 20, 2021 at 16:28
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Nathan's Answer might be true, but not for the reasons stated. To whom is it not obvious that there is a definitive relationship between pressure and quality ? The specs in Question clearly show that the manufacturers boast different expectations for their products. All other things being equal, the pressure of 40- or 60 PSI pressure should be the deciding factor, but are all other things equal? I'm guessing that as with any tyred vehicle, less pressure will be better sometimes, more pressure in other circumstances. Nov 20, 2021 at 22:07
Don't take the pressure specifications on tyres as anything more than an “idiot guide”: if you pump it to that value then you can be pretty sure it will neither spontaneously explode nor have unduly high risk of pinch flats – but that's about it. In most cases, the numbers will be far from ideal for whatever kind of riding you intend to do with it.
Typical pressures that make sense for MTB riding are between 1.5 and 2 bar / 20-30 psi. It's totally possible to go outside of that range, but you should only do it if you have a good reason for it. I variously run pressures between 1 bar and 4 bar in the same MTB tyres. For example, in mud and snow very low pressure makes sense.
This applies somewhat orthogonally of inherent tyre quality / reliability. With different tyres there may be different reasons for choosing particular pressure values. For example, light XC-oriented tyres are easily damaged. If you use them in gnarlier terrain than they were designed for, or with a heavily loaded bike, pumping to higher-than-ideal pressures helps somewhat protecting them from pinch flats. For downhill tyres this wouldn't be as much of a concern, on the other hand those have the problem of very high rolling resistance on tarmac or hard-pack, which can also be somewhat ameliorated by high pressure. In both cases, you sacrifice grip and riding comfort, but it may be worth it. And at least if using inner tubes, you can usually expect that a good-quality tyre will also cope with a lot more pressure than the manufacturer voiches for.
