hi,

i'll be looking to replace my pirelli pzero c dry with another competition tire. I'm currently leaning toward the Michellin pilot sport cups but would like to hear advice on a couple points:

currently i'm running 245's in the front and 285's in the rear. going to a michellin would require me to go down to a 225 in the front (and consequently in order to avoid the car pushing downsizing to a 265 in the rear).

1. would anyone care to comment on whether to stick with the pirelli's with the larger sizes or go to the smaller sized michellins.

2. i think i've ruled out the khumos simply because they seem to be lower performance with a lot lower longetivity. is this true?

3. lastly, i'm really optimizing for autox. all the tire tests i've seen are on the track. would anyone comment on tire test results on autox? my gut tells me that track results would differ from autox ?

thanks in advance for all your help...

cheers,
boris

 

Boris: I like your thinking. I'd like to hear some feedback about autox applications as well. There seem to be plenty of comparisons involving the Cup tire for track (which I do as well), but little on autox. I've read that the Cup tires take longer to heat up on the track, so I'm not sure they'll even beat the Kumhos at autox where tires don't get a chance to heat up much. My guess is that the Hoosier autox compound still rules because they have a soft, sticky compound, and heat up very quickly, but I don't know what the best DOT autox tire for driving on to the event would be now.

Regarding sizing, I agree that 225f/285r would likely contribute to push. I've read that the Cup tires are a little narrower than most of the alternatives of the same size. 245 mm should be 245 mm regardless of brand, but I noticed that the my Kumhos were a little wider than the same sized BFG R-1s I had, so there is some variation within the same size across brands. All that means that you might be losing a little more than the indicated 20 mm (.8") by downsizing. Maybe Michelin will add more sizes soon, as the Cups seem to be getting very popular for track applications.

I want more info on autox applications before I switch from Kumhos. It's ok for me to lose a little quickness at the track because I'm not racing, but I don't want to lose a couple of tenths at autox. The Kumhos have held up fairly well for me. I have 3 DEs, about 8 autoxes, plus driving to and from events on my current set and they have a little left. I realize that some don't get that much from a set, so maybe I'm going too slow.

 

Boris,
you probably should do a search because I'm sure there is AT LEAST 3 posts regarding the Cup tires between here and either the Racing/Driver Ed and Wheels/Tires forums.

As for 2, yes the Kuhmos appear to wear out quicker than the cups, having driven on both.

And for 3, you would have to consider that for AutoX, you don't get the same heat up as lapping on a race track. I would think maybe the Cups are not the best tire for AutoX, other than they have long lasting characteristics? Just my opinion. It really can take a couple fast laps to get them hot. I wouldn't think from AutoX to Autox (differing setups that you can get) that you would get a scenario that would be consistant for warming the tires sufficiently, especially if only given 2-3 timed runs at the end of the day to try win your class?

Cheers,
Dylan.

 

Boris,
I ran Kumho Ecstas last year (225 & 275). They stuck well but, with the stock cab suspension, resulted in massive understeer probably due to the sizes used.

I have 205 & 255 MPSC's for this year as my wife and I will be doing DE's too. The Ecsta's started to get greasy after about 6 fun runs in quick succession, so I knew they were not what I wanted for DE. We'll see how the MSPC's do at the autocross Saturday at Candlestick (you coming? I'm looking forward to battleing you this year!). FWIW, I chose the 205/255 sizes because I use the stock 17" cup rims.

 

Tom,

Yes I'm coming Saturday (wouldn't miss it). FYI... i'm running the 18" technology wheels, and with my 245 and 285 setup the car doesn't push. i'm really happy with that part of it. i do feel that the pzero c dry's take some time to heat up, so i'm loosing some time. but once heated they are AWESOME! I'm really disappointed that Kumho or MSPC don't make that set of tire sizes...

cheers,
boris

 

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by Jim Michaels:
<strong>My guess is that the Hoosier autox compound still rules because they have a soft, sticky compound, and heat up very quickly</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">I'm inclined to agree. There's a C2 driver in our PCA Region who normally finishes in the top 5 (out of 40+) using Hoosier auto-x compounds. This coupe appears to have a fairly stock suspension setup, so I'd say the tires and driver are probably the real difference.

In terms of sizes, I think all of us 993/964 autocrossers would benefit from using 225's at all four corners. Every 993/964/RSA guy I've talked to says his car ploughs. Aside from Mr. Michael's detached sway bar trick, I think four 225's is another remedy for that interminable understeer.

As for max size, Bob Tunnel, SCCA Nat'l Champ, advises against the use of tires greater than 245. His M3 <a href="http://www.tunnellracing.com/M3toESP.html" target="_blank">setup</a> specs provide some interesting perspective. Obviously, this is not a 911 but some of the information is applicable.

Any other ideas?

 

Joey: As I recall, Bob recommends 235s at each end for the late E36 M3. OE sizes are 225f and 245r. 225s at each end of a 993 would certainly cure push, but I think I'll stick to disconnecting the front sway bar.

 

Yes Jim, I read in the recent European Car how BMW went to larger rear tires in the later E36's to reduce oversteer (sound familiar?). I also saw on SpeedTV the effects sway bars have during high-speed events, something you've mentioned on occasionn. Kyle Petty was piloting a Porsche 996 in some GT event and, with a detached front sway bar, set up for a kink--not a real sharp corner--and realized his car was a little loose. As you can imagine, that front end took hold like a pit bull and sent him on a nice 360 off the track.

I thought it might be worth mentioning that optimal autocross setups are probably not the best for the track ... unless you like to drive rally style. <img border="0" title="" alt="[Wink]" src="wink.gif" />