whitecat

So lets say I have a tire that is rated at 35 PSI. It is an 47-559 tire, or a 44 mm wide tire on a 26" rim. Since I am heavy, almost 280 lbs, 35 PSI doesn't quite cut it for me, tire is almost on the ground. I have pumped it up to 45 or 50 PSI and it is about right to carry me. So my question is - is this over-inflation dangerous? The tire is currently pumped up 30% more then rated pressure, so I am concerned what could be the consequences? What is the danger of over-inflation besides getting the tire blow off the rim?

This one seems seated quite well, was hard to put on and it looks unlikely to blow off the rim. I have ridden it at 45 PSI in 100°F weather today and it held up fine. So the big q is - is it safe to do so in the long run? I'm using it as a front tire, so it is imperative that it is safe to do so.

https://www.savatech.eu/pdf/bici_slo-ang.pdf
It is listed under classical tires - 47-559 with tread pattern V13.

What is confusing is that under MTB tires there is listed an 47-559 tire with a tread pattern B42 that is rated for up to 65 PSI. Tire seems identical to this one I bought, so I cant make out why are they rated for different PSI. Anyone can explain?

echotraveler

most tires i know hold a lot more than those....i would consider buying better grade tires that can hold at least 80 psi. it may hold off, but you can never be confident about it.

cheers,

Arturo

whitecat

Yes, well that is the point - these look and feel like a really good grade of tire, nice good fat sidewalls, good tread, quality production, and they hold tarmac like glue. All in all I would be very much satisfied if not for that weird low pressure? I tend to ride at 40 to 50 PSI on 44mm tires, so I do not really need more pressure. But that is the problem, confidence.

Commodus

Well, a 35 psi limit seems awfully low. I'm certainly no tire expert, but I haven't seen ratings like that for a while. The tires I'm running on my mtb right now have an upper limit of 80 psi. Also, manufacturer's ratings are purposely set with a wide safety margin to protect themselves from possible litigation. So...I'm tempted to say it's fine. Also, over-inflated tubes rarely cause tires to unseat, in my experience, and generally fail at the valve-stem first. The exception is when you're using a slightly too-large tube and a slightly too small tire...I have seen that before.

Anyways. It seems a bit ********, frankly, to risk it. The possible damage is considerable, however unlikely. Tires are cheap. Buy ones that work for you.

Kojak

I agree. I took a quick look at the inflation ranges of our tires in approx. that size. Almost all of them can be inflated up to 70psi. Is it possible that you are looking at the lower inflation range number?

You're theory is good in that you would definitely want more than 35 psi in your tires given your size. Running them that low is inviting a snakebite flat.

whitecat

Kojak - no, that is the max rec. pressure. You can open a pdf file with a list of these tires, link is in my first post. It is correctly listed as 35 PSI max. Maybe you could say something more what do you think is it dangerous to ride like this? You have exp with tires and I would like to hear your opinion.

And just to add, rolled into work today, tire at 45 PSI, rolls ok, cushions road bumps ok, and seems to be holding ok. I'm less paranoid now, but not completely confident yet

RT

I roll with Forte Gothams (700x32) on one of my commuters, but they are also made for the 26" wheel. It is a solid tire, only $12.99 per, and while it is heavy, it is H-bomb-proof. I am 180, used to be 230, and max PSI is 90. I would get a tire that tolerates more pressure.

imi

Why not send this question to the manufacturers?

Is the max/min pressure embossed on the tyre? Just thinking it could be a misprint?

whitecat

Well it makes sense, doesn't it. While this tire seems ok for now, I am not at ease thinking about it all the time - will it blow or not. I think I will bin it or sell it to someone lighter who can use it at it's rated pressure. It should be sufficient pressure for someone that is 150 to 180 lbs, to use as a front tire. $15 is not a good reason to risk my head riding this tire.

About Forte tires; I'm from Europe and it is pretty hard to find that brand online here. Otherwise they seems sturdy enough and a nice tire for the price.

imi; tires do have embossed max. rated pressure on the sidewall, it reads 35PSI. It's a shame really, because everything else about this tire seems ok. If you look at the link in my first post, you can find a pdf file with tire models and ratings; it is not a misprint. I think this tire was meant for cruisers and such similar laid back bicycles, where it is not the norm to ride it fast or hard enough for the pressure to matter much.

I cant seem to find a good sturdy tire that will last me more then a few months without sidewall cracking or tire bulging or something similar. Maybe I will try Michelin Country Rock next. I've heard good things about them, and I need a good fast rolling tire with good grip in the wet and dry - for asphalt - and still to have it last at least a year. I average 2500 to 3000 miles a year on this bike, so the tire should be able to do at least that much. Anybody tried those Michelin's?

AEO

80psi for a 47mm tire? are you crazy?

Here is the schwalbe inflation chart:
https://www.schwalbetires.com/tech_in...ation_pressure
50psi for 47mm should be okay.
those Sava tires probably have lower recommended pressures, because they're designed for off road use.

The specific mode of failure for overinflation is that the rim will split open, explosively, especially with wider tires on narrow rims. A tire will almost never fail first.

HappyStuffing

This happened to me before. I used to have a pump with no gauge and my general test of when the tire was inflated enough was basically to pump it up until rock hard. To be fair, i'm talking about my 700x26 road tire.

Anyway, i ended up causing it to bubble and it would ride all bumpy. Not to mention hitting the fender ever revolution and making annoying sounds from rubbing.

thdave

My LBS told me that tires are rated to half the pressure they can truly hold and still be safe. Keep the pressure below 70 and, according to my LBS, you'll be safe.

Seattle Forrest

I always run my tires over inflated. I think the limit printed on mine is 80 psi, but I run the back at 120 and the front at 110. I've been doing this for months.

Kojak

This is from Sheldon Brown's website. I often defer to him, as my opinion could be interpreted as biased, while Mr. Brown (RIP sir) is largely recognized as a speaker of the truth regarding all things cycling.

Pressure Recommendations

Most tires have a "maximum" pressure, or a recommended pressure range marked on the side of the tire. These pressure ratings are established by the tire manufacturers after consultation with the legal and marketing departments.

The legal department wants the number kept conservatively low, in case the tire gets mounted on a defective or otherwise loose fitting rim. They commonly shoot for half of the real blow-off pressure.
The marketing department wants the number high, because many tire purchasers make the (unreliable) assumption that the higher the pressure rating, the better the quality of the tire.
Newbies often take these arbitrary ratings as if they had some scientific basis. While you'll rarely get in trouble with this approach, you will usually not be getting the best possible performance with this rote approach.
Savvy cyclists experiment with different pressures, and often even vary the pressure for different surface conditions.
Optimal pressure for any given tire will depend on the load it is being asked to support. Thus, a heavier rider needs a higher pressure than a lighter rider, for identical tires.
Since most bicycles have substantially more weight on the rear wheel than on the front, the rear tire should almost always be inflated to a higher pressure than the front, typically by about 10%.
Rough surfaces generally call for a reduction in pressure to improve ride comfort and traction, but there is a risk of pinch flats if you go too far.
Rider skill also enters into this: more experienced cyclists learn to "get light" for a fraction of a second while going over rough patches; newbies tend to sit harder on the saddle, increasing the risk of pinch flats.

The entire article can be found @:

https://www.sheldonbrown.com/tires.html#pressure


As for problems that over-inflation may cause, the one that I would be most worried about is the tire blowing/rolling off the rim, especially if this is a front tire.

For those of you who have never visited his website, I highly recommend it, but only if you have some time. You will get sucked in.

whitecat

I am aware of Sheldon Brown's website and his recommendations. In all reality, probably the tire would hold 50PSI, but is simply does not give me confidence to descend at 30+ mph on a busy road while keeping up with the traffic. If the tire exploded in such circumstances, it would be hard to get out of that alive, and I have decided I am not willing to risk it.

I have been looking at Schwalbe CX Comp semi slick as a front tire replacement. My priorities are dry and wet grip, low rolling resistance and satisfactory resistance to flats. Would that tire fit the bill? And it is 50-559 size.

whitecat

Anyone? I have a choice between that Schwalbe CX Comp tire, and Michelin Country Rock. Which one is better suited for my urban riding? Top of the list is wet and dry grip, then longevity, and last is at least some puncture protection. Ideas, experiences anyone?

Kimmitt 

A tire that's rated for 35 PSI is implicitly a low-quality tire. So . . . yeah.

gerv 

50 psi tire exploding at 30mph...? If you are doing serious descending, get a good quality tire and put the pressure at the recommended top level. Otherwise use your brakes.

imi

Here ya go:
https://www.conti-tyres.co.uk/conticy...+country.shtml

and you can order them here:
https://www.wiggle.co.uk/p/cycle/7/Co...re/5300002816/

whitecat

I never buy Continental since majority of their tires imported into my country are third-grade tires, awful low quality, reports of them failing all the time are common. It is believed they are rejects that are not fit for sale, but they think they can sell them here at half the price. If I wanted to buy Continental, I would have to go with some online retailer from UK or Italy, and that adds customs costs, delays with shipping etc - not worth the hassle for just a tire.

I asked for comparison between Country Rock and CX Comp, since that is what I had available here at the moment. Since no one said anything on those two tires, I went and bought Michelin Country Rock, so we will see how it will hold up. It seems it is hard to get a good answer here lately, more precisely an answer to the question asked This tire got good reviews on the net so that's why I bought it, we will see is it any good.