Discussion in 'Fiesta ST Autocross' started by Mister_Mino, Jan 6, 2015.
Oh I am not doubting that, Scroggs is a great driver as well.
The drivers on Bridgestone finished higher in the PAX than I expected. Making my decision easier.
Question re: results from San Diego (or anywhere else). How is it that very early season events can best be used to evaluate tire performance? My question arises due to the problem of comparing apples with apples, as it were. If (a) there are contingencies at play, and (b) there's a hot early-season rumor that Bridgestone has made a great tire, might it not be the case that (c) many of the better drivers are running Bridgestones, thus making any tire v. tire comparison difficult? JLWSN's comment that drivers on Bridgestones finished higher than expected might be an attempt at taking such into account, but Lord knows, that can be difficult to do. I would of course love to see a randomized, double-blind, controlled trial of the matter, but that's not gonna happen, so, the question remains--how does one best use the information available? Sounds to me like it could still be very much a crap-shoot.
True Jim, but most drivers want to be on the fastest tire more than they want contingency...they want to be first. Many of these drivers test and tune mutiple brands at the test and tune. Members of this forum saying they were faster on "grippy but abrasive concrete" catches my attention, but mutiple national champions and/or mid-pack drivers have the results I have already witnessed really influences me. Driver confidence, car setup, weather conditions, and course design will always change results. Greg Reno won on Kumho XS because were the only tire in the right size that could handle the heat a stock Mini Cooper gives them. I believe I can win or lose on the Hankooks, Dunlops, Rival, or 71Rs, so size, heat tolerance, and OPR affinity are most important to me.
Thanks for the reply--I suspected there was probably more info out there than what I knew of (and you've just confirmed that for me). And I hope I didn't seem to be disparaging your or anyone else's thoughts/conclusions, etc. It's just that being of a scientific bent, I'm a born skeptic, and always looking for objective data, weaknesses in what we know (or think we know), how we come to know what we think we know, etc. For instance, how did Greg Reno come to the conclusion that the Kumho XS tires were the only ones that could handle the heat? As far as I can tell, Greg could win running circus balloons as tires!
Greg tested the Rivals and ZII but found they started to lose grip as he got more comfortable on the course, which was opposite of his experience on the XSs. The Mini, with less than 1 degree of negative camber and hubs which seem to be impossible to cool, heats tires much more than most autocross cars.
Thanks, JLWSN. It's nice to hear some of the backstory, I guess one would call it. I don't know Greg well, but I certainly can vouch for him being able to drive that Mini. Interesting that the heat capacity of the Kumho tires was so different, or at least that they reacted differently to what seemed the same thermal stress.
Well, you can imagine the adhesive characteristics of polymers or any molecule will have plenty of variance, depending on structure and properties. All designs have their optimal temperature ranges.
I'd expect, though, that tire manufacturers producing performance tires are looking at similar specifications for desired characteristics, including heat tolerance, etc. There are trade-offs, no doubt, in various characteristics, but the same final endpoint is the aim, I'd guess. If major tire manufacturers are good at what they do, and I think they are, I'd expect that their final products, with the aim of top performance in the same/similar circumstances, to be fairly close in character. That seems not to be the case, though, based on what I'm learning now. There may be too many variables weighted differently by different companies to give everyone the same results. Anyway, I'm glad to be learning a bit from the goings-on here and elsewhere. I just hope no one judges Dunlops' best efforts based on my driving!
Confirmed: the 215/45/17 Bridgestones do fit on the stock rims. Some rubbing on the top of the fender liner if the suspension is fully compressed -- the course we were on had a transition from infield to banked oval, and the loaded tire made non-serious contact with the top of the liner.
The sidewalls don't feel quite as stiff as the Dunlops (which are 40s rather than 45s) but the grip was marginally better, and this was a pretty low-grip site. I imagine the difference between the two would get bigger as more grip were available. The tires pick up marbles like a V710 but oddly did not seem to launch better than the Dunlop, not because of grip but because of sidewall twist. On the Dunlop (24.4 tall) I shifted to third twice; on the RE71s (24.7) I just hit the rev limiter for a second or two.
Fastest run on RE71 was 44.7XX in sunny 65 degree temps; best run on the Dunlops was a 44.9XX in much cooler temps.
I took 10 runs on the Bridgestones and drove home (240 miles) on them -- they still look new.
I did pax within a few hundredths of multi-jacketed Ron Bauer's DP Miata and ahead of Mitch Lewis in a DS '15 WRX on Star Specs. That's rare.
Edit: Josh Salvage is trying the 245/40s!
Des, will you be at NWR/SCCA #1 at Bremerton? I'll have my Konis on by then so that should be a good time to do some tire comparison as I'm on ZIIs still.
Hey, Alan, yep, already registered. I won't go if it rains but so far forecast looks good.
We're six deep so far at Crow's as well, and I'm pretty sure the Mark Allen will be there in Rob Luis' Mini too. Having a couple of national champions in the mix ought to help clear up any confusion about competitiveness ...
FWIW in HS at Crows, Rob is registered for the Pro. I suspect we might see Mark last second for the Pro (and running Sunday only). I'll be very surprised if Mark is in for the Tour, not sure about Rob.
Deana Kelley is going to codrive my car in HS (open) at the Pro
Should be a fun couple of weekends coming up soon! Get your entries in now if you haven't already!
Saw a guy run Rivals and Bridgestones back to back on a very well setup RX8 over the weekend. First run on the Stones was 2 seconds quicker then his fastest run on the Rivals...his second and third runs were progressively slower, but still the slowest was 1 second faster than the rival. Pretty interesting test.
Got the 215/45R16 Rival S yesterday, mounted them on the (same) 16x7 Sparcos. Updated pics, left to right are 225/45R16 Z2SS, 205/50R16 RE71R, 215/45R16 Rival S
Rival S is JUST a tiny bit narrower than the RE71R and Z2SS (which as shown in previous picture in this thread are essentially identical in width)
Also shorter for the Rival S, but that isn't surprising
Working on scrubbing the RE71Rs on the street today and tomorrow, then Rival S on Fri/Sat. Will run both tires at a PCA event on Sunday (Marina = concrete, both a morning and afternoon session).
(Picture of the car on RE71Rs at my work this morning)
I will say the Rival S is VERY soft to the fingernail test
Des : Also talked to Rob Luis last night (he saw the Rival S picture I posted yesterday on Facebook and had a "How in the #@$@$ did you get those tires?" phone call ) : the Mini is out for the Crows Tour, but both Rob Luis and Alan Jung will be driving it for the Crows Pro.
My 215/45R16 Rival S on a 16x7 Sparco rim is slightly wider than my 215/45R17 RE71R on the stock rim. I would say it's maybe a couple Millimeters at most though.
Which tires are you running on Sunday Trevor? I'll be curious as to how our cars compare there as I am still on the Z2SS.
I plan to run the Z2SS as well.
I am saving the Rival S for Pro's, the RE71R will be backup at a Pro in the event the Rival S is not getting it done. I plan to run the RE71R at the Champ/Match Tours due to the cash vs tire contingency. I am still strongly also considering the Kuhmo V720 since the contingency is $600 per event in product credit for both Pros and Tours. That will be dependent on me either selling the Z2SS or using them up at local events though. Also dependent on how well the Rival S is doing and if I have won any tires by that time.
Yeah, I am curious if the Kuhmo is even going to make it in time.
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