Quote:
Originally Posted by Jawnathin
Doesn't get much closer than 0.001 I suppose. Interesting as I thought it would be favorable to the 245 than most other courses. I wonder what this means for a course that I thought was more favorable to a 235. Maybe 235/40 has a bigger gearing advantage than I thought?
|
I don't think it's that any size has a big gearing advantage - more like the actual time over distance differences are small when you on the limiter with one tire vs another and those small differences are offset by the improved accelerations elsewhere.
Quote:
Originally Posted by Jawnathin
You are right, I did slow down a bit once I got into the slalom and may technically have not needed a shift into 3rd, but I figure the car was more settled down @ 5500rpm in 3rd vs 7200~ rpm in 2nd while in a high speed slalom. Also upon the exit of the slalom I'm already in the right gear in the acceleration zone, rather than spending time shifting when I got there.
|
It is definitely difficult to slalom at max g's when you are right up against the limiter and I understand wanting to be in 3rd before the highest speed pull. I actually thought the 225/45-16 was going to show better since it would pull 3rd harder, but that's not what the calcs showed. I also wasn't trying to show 'should've stayed in 2nd' - just how big the differences would be.
Quote:
Originally Posted by Jawnathin
You touched it a bit with analyzing what happened if I left it in 2nd, but I'm under the impression this data only represent FT zones. So with that in mind, how does your analysis account for the times I'm above 59mph and into 3rd, but not FT? I was 65mph at the exit of the slalom entering that turn around. There was a few moments of partial throttle/lift before it drops below 59mph. I would have liked to save the time on the shifts, but I'd hate to be giving up 6mph at any point on the course.
|
It is a bit hard to see in the plot, but note the '2nd gear limit speed' line. You just touch it at the start - reflected in the calcs with the 'on limit' time. You just touch it briefly (0.2) just after the shift to 3rd (neglected in calcs). You go over through FT zone 2 (20.3-22.9) - in the calcs. You go over briefly at the end of FT zone 3 - in the calcs. And you go over at the end - again in the calcs. However, looking more closely at the data following FT zone 2 (23.0-23.6), there is some data with part throttle and mixed longitudinal accelerations - hard to tell if it is 'coasting' or braking. This wasn't included in the calcs. It is 64.3 mph over 16m, which would be 0.043 sec slower at the 59.7 limit - enough to wipe out the -0.026 advantage of the FT-only 'stay in 2nd' calcs. Championships have certainly been won or lost by less than 0.017, but overall I still say I'm not going to be too worried about the gearing effects in tire choice. And this may all be moot - if the current RE-71R hype holds up (not to mention the upcoming Rival S), I think the 235/40 ZII (with no contingency) will be really unpopular and almost everyone will be on 245/40-17's anyway
