Rolling resistance ratings and tire wear
 

I’m curious if there are any opinions/experience here concerning how tire wear effects rolling resistance?
As my tires develop flat areas over time, I can’t help but think that it must have at least some level of increased resistance?
Although they may still be safe to ride perhaps they become “performance compromised”?

We all become 'performance compromised' over time. Some(things) more than others. :twitchy:

As the casing gets thinner, it's more likely to be more supple and roll better, rather than worse.

Assuming not a "fixed" gear bike...
Rim brakes ?

Barry

Check out the bicyclerollingresistance.com series on GP5000S for a good demonstration of rolling resistance as tires wear.

Am curious about the flat areas? I take it you are not skidding the rear tire so is it due to unequal material on your tires wearing faster? What brand and type of tires? Very perplexing since I have ridden for decades on all sorts of rubber and never seen this.

Also: on my gravel bike, I run tires with little knobs. As they wear down on the center, they get faster -- at least, that is my subjective impression.

I assume that he's talking about the squaring off of the rear tire profile.

if I recall correctly - rolling resistance increases as the tire wears - but at a certain (later) point the resistance will begin to decrease (but not to the level of a new tire)

I have been idly curious about that, since a person running their tire pressure higher to try to get lower rolling resistance will get more squaring off of the tread. How does that affect the rolling resistance versus a tire that has worn down more evenly thanks to lower pressures...

I believe he's talking about the wide flattish center strip that tires, especially rear tires, wear to just from rolling, not the skid patches from braking.

Correct on both

Correct

Correct

Bet you are right, but what threw me in his description was the phrase “flat areas”. All my tires wear uniformity and not in ‘areas’. Semantics.

This is correct. Less tread rubber to deflect means lower hysteresis losses. It sometimes amazes me how people tend to draw the exact opposite conclusion of what the data show, and what logic dictates.

https://cimg9.ibsrv.net/gimg/bikefor...dc04e0969.jpeg
https://cimg0.ibsrv.net/gimg/bikefor...562aa712f.jpeg

Before I had this truly crap cheap Wanda king tires. But the walls are so thin it actually had much lower rolling resistance than my current Gravelking plus tires!! I can cruise a couple mph faster on it but flats so frequently I had to let it go. The walls felt like paper, crazy thin, while the gravelking plus felt like thick leader hide.

Interesting. So a tire is generally at its slowest about 2/3rds of the way through it's lifetime. And for whatever reason, wider tires are impacted to larger degree than narrower tires (not significant at maybe a 1w difference, but curious).

Tests by Al Morrison and Tom Anhalt show that brand new out-of-the-box tires have slightly higher Crr than a tire that's been run for 40 or 50 km, but that over time Crr slightly increases. The casing doesn't usually get thinner: the tread compound does. The bottom line is that when racing, we often "break-in" new tires for 40 or 50 km. Some of the lowest Crr racing tires are pretty fragile with very thin treads, so if you use them too much you'll flat during a race and the rolling resistance goes way way up.

The Vittoria Corsa's I had showed a very weird wear pattern. They didn't wear the outside longitudinal line tread but the tread thickness of the tire grew quite thin before the tread started wearing. For a long while I thought that the tread wasn't going to wear and then suddenly it wore down very rapidly.

I wonder if the initial higher RR has to do with the tire taking a slightly different shape when inflated on a rim than it had in the mold, and then break-in is the casing having loosened up a bit to assume the correct shape. The tread theoretically ought to become more flexible as it gets thinner, but it must depend on whether it gets harder first... my takeaway is that you are probably best served with the thinnest tread you can get away with, especially if you take a lot of calendar time to wear tires out (like I do.)

If you actually are 2 mph faster on your old tires then your current ones are the very definition of a crap tire. Of course it is much more likely that there is no where near this kind of difference in tire performance. We get all kinds of "my tires feel faster" anecdotes but people somehow never manage to put a stopwatch on their rides and provide actual data.

The initial increase in CRR for new tires could well be that once the tire is out in the real world, there is additional stiffening of the tread rubber due to oxidation.

So where's the data?

The data present here supports the opposite of your assertion.

That’s not what your mother said last night, Trebeck!