Quote:
Originally Posted by PrimeBMW
I typically get about eight days out of a R7 and could probably get close to that with the A7. The limiting factor is the correct camber and it's different for each tire.
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Agreed. The R7/A7 twins use different compounds *BUT* neither is really a true radial tire in the sense of radial design. Both use a bias body ply carcass angle on the order of 45 degrees - at least they did last time I dissected one. This is sometimes referred to as a 'semi-bias' carcass design. For this reason the R7/A7 twins love more camber and operate at larger slip angles. Think; easy to drift and slide but with the added sidewall stiffness that bias ply design inherently brings. Sure it's old tech, but if your set up can dial in enough negative camber (and caster) you'll reap the rewards of fast and easy to drive with these two solutions. Keep in mind that adding as much caster as possible is desirable up to a certain point because the suspension and tire will gain camber when turning.
Now steel-belted, semi-bias ply tire wear life (worse) is a totally different topic partially because of the larger slip angle operating regime than seen with ninety degree radial carcass designs. In the old days when bias tires were king, even the F1 champs slid and drifted around while still going quickly (see image below).
In a relatively low downforce car (no ground effects), if the car isn't almost on the verge of being partially out of control all the time, then lap time is being left on the table by the driver (regardless of bias ply or radial solutions). One way to tell (for relatively low downforce cars) which drivers are going slow (other than the stopwatch) is if the tires are not "talking" in every corner then that driver is driving the tires below the limit and not on the peak of available grip (on the limit).
If the tires are screaming at you then that's too far over the limit, but being able to hear them "talk to you" - even with a helmet on - is one way to know for sure you're not leaving lap time on the table. Example: 1/10th of a second lost in every corner on a 13 corner track (say Road ATL) is 1.3 seconds lost per lap. Multiply that by 30 laps and you get 39 secs!
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