155/80-13 tires (looking for LRR options)

[Daox]

I'd definitely go with the LRRs. According to a tirerack article, 2/3rds of the rolling resistance of a tire is from the tread and plies (http://ecomodder.com/forum/showthrea...res-14133.html) where 1/3rd is from the sidewall and bead area. Going with a LRR vs conventional tire IMO is quite important and worth the small aero penalty for a slightly wider tire.

[Crazyrabbit]

I don't know if they are LRR but I found that Ohtsu Negotiator NS80 155/80-13 tires are rated at 51 psi like the Sumitomos are. The UTQA rating is 280AB. The sidewall states: "The Max Pressure Rating Applies to USA and Canada only." I thought that was a bit odd. So if I drive into Mexico, can I pump them up to 60PSI? Anybody know why they say that? I bought a pair, but have not tried them yet, has anybody else tried them? What do you think of them?

[mnmarcus]

Originally Posted by Crazyrabbit

I don't know if they are LRR but I found that Ohtsu Negotiator NS80 155/80-13 tires are rated at 51 psi like the Sumitomos are. The UTQA rating is 280AB. The sidewall states: "The Max Pressure Rating Applies to USA and Canada only." I thought that was a bit odd. So if I drive into Mexico, can I pump them up to 60PSI? Anybody know why they say that? I bought a pair, but have not tried them yet, has anybody else tried them? What do you think of them?

I ride mountain and road bikes and spent a few years as a bike/ski technician and once bought a pair of road tires that had a high psi, thinking they'd be LRR. They were also cheap. They were not that LRR, and the ride was harsh...

[arcosine]

Why not 135/80R15 or 135R15? Course, you'd have to change rims.

http://store.cokertire.com/135r15-fi...wall-tire.html

[CapriRacer]

Originally Posted by arcosine

Why not 135/80R15 or 135R15? Course, you'd have to change rims.

http://store.cokertire.com/135r15-fi...wall-tire.html

There are 2 problems with that:

1) That's the wrong direction for RR improvements. Bigger tires = better RR

2) Coker only sells replica tires - which are by definition, not LRR

[roflwaffle]

Maybe a larger tire = better RR, maybe not. I don't think anyone here has posted any data indicating that's the case in general. Maybe for specific manufacturers there are anecdotal examples, but as a whole I don't think anyone has comprehensive data indicating that's the case.

[arcosine]

A 135/80R15 is .75 inches bigger diameter than 155/80R13.

[CapriRacer]

Originally Posted by roflwaffle

Maybe a larger tire = better RR, maybe not. I don't think anyone here has posted any data indicating that's the case in general. Maybe for specific manufacturers there are anecdotal examples, but as a whole I don't think anyone has comprehensive data indicating that's the case.

Barry's Tire Tech

This is an analysis of some data submitted to the California Energy Commission. Among the data is a study of tire size. Needless to say, that there are a lot of factors, but if we isolate tire size: Bigger = better - and by bigger, the data seems to point to every parameter in the numbers used to delinate a "size" - wider or taller or larger in rim diameter.

But there is such a huge difference between tires (meaning make and model), your point is well taken.

[arcosine]

This tire is rated for 44 psi - Nankang CX668 155/80R13

Nankang - Tires

400AA I think the A heat rating is important, I could be since the tire heats up less than a B rated tire, it should have less rolling resistance. But maybe the 165/80R13 would be even better.

[arcosine]

From Sheldon Brown: All About Bicycle Tires and Tubes

Width and Pressure

Tire width and pressure are inextricably linked. It is a serious mistake to consider one independently of the other. Generally, wider tires call for lower pressures, narrower tires call for higher pressures.

Consider, for example, a tire one inch across, at a pressure of 100 PSI (pounds per square inch). Air is pushing down against the bottom half of the tire cross-section with a force of 100 pounds per inch of length. Each sidewall of the tire bears half that load, and so inch of length of tire sidewall will be under a tension of 50 pounds. Now let's consider a tire twice as wide, two inches across, at the same 100 PSI. Each inch of sidewall will be under a tension of 100 pounds. So, a wider a tire would ride harder, and need stronger fabric, if inflated to the same pressure,

The part of the tire that is actually touching the ground at any moment is called the "contact patch." Generally, the area of the contact patch will be directly proportional to the weight load on the tire, and inversely proportional to the inflation pressure. For instance, if the rear tire of a bike is supporting a load of 100 lbs, and the tire is inflated to 100 PSI (pounds per square inch) the contact area of the tire will be roughly one square inch. If the pressure is reduced to 50 PSI, the tire will squish out until the contact patch has become 2 square inches (or until the rim bottoms out against the tire.)

A common debate among cyclists centers on the issue of whether a wider tire has more or less rolling resistance at the same pressure. The constant pressure is proposed because it appears more scientific to eliminate this as a variable, but this is not realistic in practice. The short answer to this question is that, yes, a wider tire of similar construction will have lower rolling resistance than a narrower one at the same pressure. This fact is, however, of no practical value. If you are comparing two tires of similar construction, with the same load, and the same pressure, either the wider tire is overinflated, or the narrower tire is underinflated!

A tire is supposed to deflect a bit under load. This deflection the whole purpose of pneumatic tires. When you sit on your bike, your tires should visibly bulge out at least a bit under your weight. If they don't, they're overinflated.