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Old 08-30-06, 05:33 AM   #1
FarHorizon
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Weight to tire-width ratio?

Anyone know of a chart showing recommended weights for specific tire-widths? Just curious... Thanks!
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Old 08-30-06, 05:44 AM   #2
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Depends on how rugged you want or need the tire to be.
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Old 08-30-06, 07:44 AM   #3
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Typically, "tire pressure" is a function of a tire's load-bearing capacity. In other words, if the maximum inflation pressure of a tire supports someone's big fat azssss, then the tire width doesn't matter.......

If you have to "over inflate" to make a tire ridable, then it is overloaded.
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Old 08-30-06, 02:03 PM   #4
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Quote:
Originally Posted by FarHorizon
Anyone know of a chart showing recommended weights for specific tire-widths? Just curious... Thanks!
Don't know of one, but I can think of one problem. Different manufacturers and different grades of rubber will be vastly different for one particular size. I am thinking of say a Continental tyre that in general are a very light tyre. Then going to the other extreme a Swalbe.
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Old 08-30-06, 08:49 PM   #5
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Good info & thanks for the feedback. The consensus seems to validate my preconceptions:

1. As total weight increases (bike+rider+load), tire width should generally increase also.
2. As total weight increases, tire pressure must increase if the tire width remains constant.
3. If the frame permits, tire width increases are preferable to tire pressure increases.
4. In extreme cases, both tire width and tire pressure may need to be increased.
5. Variations in tires (make and model) may affect the above general rules.
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Old 08-31-06, 02:01 AM   #6
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Not so fast, there, pardner...

1. As total weight increases (bike+rider+load), tire width should generally increase also.

I use 700x23 tires on my racing Trek as well as on my steel tandem (with 320 pounds of crew weight), and it works great. So you don't need wider tires for more weight. On my fixed-gear rain bike, I run a 700x20 on the front just because I can't run anything wider and not have it hit the front fender.

2. As total weight increases, tire pressure must increase if the tire width remains constant.

Nope. I run 115-120 psi on the 700x23's on the single Trek and the exact same pressure on the 700x23's on the tandem. I don't notice any lack of firmness on the tandem. On the track, I run 130 to 180 pounds on 21mm diameter tubulars.

3. If the frame permits, tire width increases are preferable to tire pressure increases.

Depends on what you're after. I run 23's because they resist pinch flats better than 20's but are still a responsive tire that lets me feel the road. 25's and 28's would feel "fat" and I'd feel like I was being slowed down. However, 28's are a more comfortable tire. Performance or comfort?

4. In extreme cases, both tire width and tire pressure may need to be increased.

No, in general, you put less pressure in fatter tires. Typically, a 700x23 gets 115-120 pounds, while a 700x35 might get 85 pounds, and a 26x1.5 may get 55-70 pounds.

5. Variations in tires (make and model) may affect the above general rules.

While tires may vary between manufacturers, the general rules for tire pressure as a function of tire width tend to remain. The main difference would have to do with expected operating pressures. For example, a 700x23 Serfas Seca is labelled to take 125 pounds. If I did that to a 700x23 WTB Camino, I would expect a ripped/deformed casing in just over 2000 km, so I'd keep it closer to 115.

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Old 08-31-06, 05:36 AM   #7
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Quote:
Originally Posted by lhbernhardt
...I use 700x23 tires on my racing Trek as well as on my steel tandem (with 320 pounds of crew weight), and it works great. So you don't need wider tires for more weight...
Yes, you can do that, but in general, I think the consensus among cyclists (and what I've read in books and magazines) is closer to my statement that in general, tire size should increase with more weight.

Quote:
Originally Posted by lhbernhardt
...Nope. I run 115-120 psi on the 700x23's on the single Trek and the exact same pressure on the 700x23's on the tandem...
Yes, you can do that too, but again, I think that the pressure you run on your single Trek is what you choose to use - not the minimum that you could safely run, while on the tandem, you NEED that high a pressure.

Quote:
Originally Posted by lhbernhardt
...If the frame permits, tire width increases are preferable to tire pressure increases - Depends on what you're after. I run 23's because they resist pinch flats better than 20's but are still a responsive tire that lets me feel the road. 25's and 28's would feel "fat" and I'd feel like I was being slowed down. However, 28's are a more comfortable tire. Performance or comfort?
Agreed. However, if I'm a loaded tourist, I'd expect fewer pinch flats with the wider tire. Heck, even if I were a commuter, I'd think that the wider tire would be preferable. If "responsive" is your primary criterion, though, as it is for racers, then narrower and higher pressure are always the best choice.

Quote:
Originally Posted by lhbernhardt
...In extreme cases, both tire width and tire pressure may need to be increased - No, in general, you put less pressure in fatter tires.
True, but if I'm riding solo with 60 psig in a 26mm tire and I want to radically increase the total load safely, a 32mm with 85 psig may be needed. Of course, should you choose responsiveness as your primary criterion, then you can use 23mm with very high pressure (as you choose to).

Quote:
Originally Posted by lhbernhardt
...Variations in tires (make and model) may affect the above general rules - While tires may vary between manufacturers, the general rules for tire pressure as a function of tire width tend to remain...
Yes, they do, but the tire profile may make a difference in the size and pressure that are desired for a specific goal.
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Old 08-31-06, 07:14 PM   #8
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Schwalbe has load capability for their tires included in their specs. I don't know of any others that supply that info.
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