Quote:
Originally Posted by bhong
FYI, Tire Rack now has OEM sizes for the RE-71RS. Was going to try 255/275 but now thinking of sticking with stock sizes. Anyone have experience with 245/265 setup?
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I just went with a new set of them in stock sizes as I simply wanted to try them out on my autox/track wheels. Given the recent TR wheel width vs performance data from TR, I decided what the heck, let's go back to stock sizing. They replaced a set of 255/35-19, 275/35-19 RE-71R. These are mounted on OZ Racing wheels with stock widths and offsets.
It's all subjective of course, so my reply on the one size up or not is really not meaningful especially since the RS is a good bit different responding/feeling tire versus the R. It would be an interesting test to instrument and evaluate that simple one size up change on stock wheel widths like TR did in their wheel width test. As a general rule, for decades I've always preferred the night taught response you get from a wheel width approaching or at the maximum wheel width range shown for a size by the TRA. It's likely one of the reasons BMW chose these sizes for the 9"/10" wheels too (sharpness of response, feedback, etc).
On to the RE-71RS review...My 2019 M2C is 100% stock. It's the only BMW I've owned in over 45+ years of BMW ownership that I've not at least modified the suspension on. I bought it new in Sept 2018 with an early M2C allocation, and it has 20k miles on it now. It's a little beast on fast autox courses.
Right off I noticed the RS is quieter on typical street driving than the RE-71R. The R had very loud "sizzle" (engineering term for when a tread void area traps air and compresses it in the contact patch) going over pavement marking stripes and other pavement features. That's gone on the RS for the most part. I feel like they are a bit more comfortable than the R also, a bit more compliant in typical street driving which is a bonus for those wanting to daily drive it.
I entered the BMWCCA MiX event here locally again this year, and we had a triple course autocross at the Performance Center yesterday, so it was a great place to try them out. Three courses, 7 total runs on each course, 6 of them for timed competition. The net was they performed superbly, and I exploited them as best I could to capture 2nd place out of 30 on each course (at least I was consistent!).
The pros have all been covered above, and I agree with them. It was ~85F here yesterday, and they were ready to go immediately. I kept them at 34psi hot and didn't experiment further with pressures. Unlike a "regular" autocross, here you are essentially hot lapping almost since as soon as you come off course, you circle around into the creeping staging line with the 9 other cars in your group, so there was very little time between runs. That part threw off my normal mental review/rehearsal I do between runs at a normal autox where you have a lot of time between runs. On course #1 (which is an interesting combination of asphalt on the track, a transition to the cement skidpad for a while, then back onto the asphalt track), the turnaround for staging in the parking lot had a huge deep puddle that I used every time, nice and slowly...
Versus the RE-71R, the RS feels less "sharp". Others have commented about it too, and I experienced what they meant. It's got huge grip of course, but your "feeling" of that isn't a precise as the R as you approach the peak and go over the top. If you've ever driven on the BFG Rival, it's that type of feeling. The Rival feels better leading up to the limit however, and the Rival is more forgiving around the limit. The RS isn't bad per se, but in one higher speed sweeper I once over did the trail braking on turn-in and abruptly lost the front grip - lesson learned though, never did that again the rest of the day.
For those with experience in the response between the PSS and the PS4S, it's a similar thing here with the R to the RS -- more ultimate grip with the successor tire but less sharpness in response (slightly less slope on the force vs slip angle chart).
For the most part the rest of the day I always got my fastest run when I felt I had left a tad on the table, and the RS punished me if I tried to "find more" on the next run. So in retrospect that was a great thing to feel, to store that feeling and settle into it with the tire as I was likely able to stay on the left side of that force/slip angle response near the peak limit a lot on course, and the RS gave me enough feedback to enable that.