Breaking in new tires
I have heard that brand new tires have higher rolling resistance and you need to break them in for a certain number of miles. Is this true? How many miles? I have a race this weekend and upon inspecting my rear tire it is in clear need of replacement. But I might risk it and go with the old tire if a brand new tire is really not recommended. Thoughts?
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Seems like all the Crr tests I've seen list mileage on the tires tested and its usually around 500mi. So in our world thats what 3-4 weeks?I don't imagine that the difference between new and broken in is THAT much, but you could get new ones and do a session on the trainer to speed up the process a little maybe. That said I'd rather risk 30 seconds of rolling resistance loss than 10 min flat change or a DNF.
First I've heard of that. Another urban/cycling myth? I just toss on a new tire and ride it, don't really think about CRR of new vs old. For me old vs new is more about puncture resistance, squaring of the rear tire, etc.
Btw, what is "squaring of the rear tire"?
The only time I've heard about "breaking in tires" is in the motorcycle world: brand new rubber is a slicker than worn rubber, so you have to be a little careful pulling out of the shop parking lot and not gassing it in the turn = rear will squirt out on you. Ask me how I know.
Other than that, any tire will be "scrubbed in" as soon as you've ridden down the block and turned a right and left corner? And intuitively, it seems that the CRR of a tire would be lowest when it's new and less scrubbed in? But...no idea, actually.
"Squaring off:" the rear tire will wear more quickly than the front, due to more weight on the rear tire and it's also the drive wheel. And since 95% of your riding is done with the bike upright and not leaned over, the center of tire will wear our more quickly than the sides. You'll see this as a slightly square profile of the tire vs a nice, rounded shape. To me, this just means that the rubber in the center of the tire is thinner than the rubber on the sides/turning edge = more likely to flat = time to replace.
As Rich also points out as well, an older tyre is more prone to getting a flat.
The rolling resistance tests I have seen usually do the test after 100 - 200 miles, so I assume that is when the testers believe the crr is at its minimum.
I put on a new tyre a couple of weeks before my A race with the latex tube — I figure with all the $s I am spending on my A race, what is another $60-70? I then use that tyre for my B races and training. I use a Hed 3 front that I only use for racing and don't change it as often because it doesn't wear as quickly.
Vitoria has introduced a TT/Triathlon slick so I assume they figure that a tyre with tread deforms slightly more thereby raising the rolling resistance. If this is true, then a newer tyre will have a lower rolling resistance because it has fewer cuts etc.