Good luck. Limited testing showed my Shaved 195/235 r1r set up to be quite a bit slower than my bfg rival set up. This is on a sealed asphalt lot. I need to spend more time with pressures and shock settings to dial the r1rs in. And of course concrete will change everything.
Y'know, I've found the same thing - I don't know why I keep trying to make the R1Rs work; I like their FEEL much better, but my ZIIs seem faster.
But maybe shaved & 15" front? Dunno.
It _seems_ to me that Rivals are better on everything but grippy concrete - Lincoln - anecdotal and NOT scientific, but seems like Rivals kinda sucked in Lincoln.
Pat's 3rd in RTR last year really got my attention, though. Pat is not a hack (dammit, I so want to abuse Mr.W right now, but can't....), the car is...good, but certainly not optimized, and 3rd?
OK. THAT'S why I'm chasing the R1R.
That, and last season, comedy of errors, at one point, I had my spring preload WAY too high. Stupid high. Mis-measured a couple of things, put a metric feces-ton of preload on the springs.
Car was loose, but OK on a grippy, coarse lot (asphalt, but fairly Lincoln-like). Not fast, but balance was in the "not awful" ballpark.
Next weekend, I threw ZIIs on it and brought it to a sealed asphalt lot.
UNDRIVABLE. Absolutely absurdly loose. No other changes.
Two things come to mind:
1. R1Rs are soft, and the tires were full tread, fairly new. Compliance in the tire let it hang on just-enough to not spin EVERYWHERE?
2. The R1R has more grip than ZII.
I don't know. Combination of the two, I suspect - the R1R has fairly deep, squishy tread, but the difference was _astounding_. ZERO rear grip. None. Not a smidge. As SOON as the car started to load, it went sideways. Broken-loose - not "maybe less rear shock" but "maybe a tie rod end is broken."
I put a fair bit of odd wear in the R1Rs with the preload high, too - it was doing some funky stuff. I don't think I've driven the R1Rs on the car since I sorted out the spring preload.
Dunno. My favorite, so far, are the ZIIs, but I do think the R1R is worth figuring out.