I was playing with the spec boxsters front wheels today. I have 3 full sets of rims and tires for the thing. 2 sets for Track and 1 set for AX. All are stock rims (these things are CHEAP). Fronts are 17x7 and the rears are 17x8.5's.

I have 245/45/17's on front and 275/40/17's rear. No rubbing. These are Kumho Victoracers. I'm using these to dial in the suspension since they wear pretty well. I have a set of Hoosier R6's on the way to try out as well in 245/40/17's and 275/4017's. I want to try a little less sidewall on the front since the 245's are pinched a little on the rims (looks exactly the same as a 205/50/15 on a 2.0 Fuch).

For kicks I put on some rear wheels that have used 255/40/17's. Since they are not as tall as the 245/45's they fit in the wheel well better. And they are about 3/4's of an inch wider in contact patch and over 1 inch wider on the shoulder when you roll it over. And with the 8.5 inch rim, the sidewalls are straight up, not pinched in.

Since the 255's fit pretty well (I may need a 5mm spacer to clear the spring collar under load, don't know yet) but they only come in the Victoracer sizes and not in V710's or Hoosiers, would the corresponding gain in footprint offset the compound improvements that the V710's or Hoosiers provide? Or should I try mounting a set of 245's on the 8.5 rims and play with that?

My thoughts are that the compounds make a bigger difference than 3/4 of an inch, but on the other hand, if I want to stay budget I could get 2 more rear wheels and just go with 2 sets of rims with Victoracers for track and AX.

What do you guys think?

Here's some interesting reading from Michelin's engineers regarding the Pilot Sport Cups and sidewall flex and pressures:

Michelin Tire Engineering Presentation

Thanks,

Bill P.

Bill,
Consider running 255s on the 8.5s all around...just like a 2.0L teener.
That way you can rotate tires to different corners, for tire wear.
I have always felt that could be a nice combo for a Boxster.

Or would run the 255s front and 275s rear. My preference would be the wider tire/wheel combo on the front considering the weight of the car.

So many choices

Hi Dan,

I know. So many choices. I'll probably use my datalogger to figure out where I gain or lose using the different tires. The 255's up front look BEEFY! But the Hoosiers are generally 1 to 2 seconds faster on 914's at Thill, so I'm wondering if the same would be true for the Boxster, because even though it's got over 200HP at the crank, it's still a momentum car.

Victoracers are mucho cheaper though. But next year the tire fund isn't a problem. But we've got to do well to keep things going with the sponsor.

Bill P.

Hi Grant,

Everyone I've talked to says that the Hoosiers and Kumho V710's are a cut above the rest. I'm not sure where the RA-1's fall, but they may be on par with Victoracers or a tad below. They seem to be a harder compound than the stickiest of the Dot-R's.

I do hear that the RA-1's last a long time, probably because of the harder compound.

Bill P.

I found out from a Michelin rep that BFG is working on a DOT race tire.....

I've wondered if BFG was going to get into the Dot-R war. Any preliminary release date for the tire?

Bill P.

Hi Grant,

What do the folks running RA-1's say about performance in comparison to Victoracers? I'm trying to gauge performance.

Thanks,

Bill P.

Bill,
Jeff Reitmeir and Jim Lane had them on their 924 hot rod for the 2005 season...their feedback on the RA1s was...and I quote. "They are JUNK" Good in the rain, and junk on a dry track.

take that for what it is worth..

RA1 isnt an AX tire ( does require some heat), but it is a little softer/stickier than Victoracer. I wouldnt call the RA1 junk for a cheap track tire. I prefered them over Victoracers I ran.

I also have been reading good things about Nitto NT-01. Doesnt sound like a Hoosier or Kuhmo slick competitor, but certainly right in there with Victoracers and the RA1. They are under $200 per tire for Boxster sizes. General consenus is that Victoracer, RA1, NTO1 are a second or two a lap off Hoosier DOT R rubber based on track drivers I have spoken with over the past year. For AX the Kuhmo 710 and Hooseir AX tires rule for DOT rubber.

I have a question for you since you have driven both DOT R and full on race tires. Given surface at Alameda what kind of an advantage do you think race slicks have over DOT R tires in AX? I'm seriously considering upgrading to race slicks next year.

I personally have not used RA1s but had considered them for a long lasting track tire.
you can still get them in 205x50x15 for $120...that is a good bang for the buck...

Hi Bill,

I think the 255 F+R would work great for the Boxster 2.5 car. The higher HP engines in the Boxster would probably work better with the 275.

GoodYear showed a DotR that looked like a 2 year old Hoosier at a NHRA Drag Racing event early last year. I spoke about it on the site, but dont know what happened to it.

I like the idea of running the same size F+R.


B

Do you think the width is a gain over the compound? The 255 size only comes in the Victoracers or RA-1's, not in the Hoosier R6's.

Bill P.

My vote is for qualifying tires, i.e., half price.

245.45.18's slicks are available in (equivalent) 250 or 430 compounds.

275's are also available, but don't think they would fit.

If you want 17's you can get (various) DOT's, but not slicks.

Ummm.....

I wonder what Lucille would feel like with 245 slicks all around on an AutoX course.

Or how about Sears?

Yup, I'm looking at the slicks, but it would force a huge investment in rims (~$4K for 2 sets) and the biggest thing I found is that since I have a 1997 tub, the car will need to be re-inforced at the rear suspension points to accomodate 18 inch rims (supposedly). This one may not be that big of a deal because I fully expect to see some issues on the tub once we start tracking it regularly. The weakest links always start breaking....

For cost containment I'm thinking of staying away from slicks to keep me from pouring more money into the endless sink hole of racing. I can't challenge for TTOD in AX with a Spec Boxster and I can't be the fastest on the track with a 2.5L motor...so I'm leaning towards leaving it Boxster Spec and encouraging more people to join me in a spec class.

Bill P.

I personally beleive compound is more beneficial than width on a low powered car.

I spoke with Tony Heyer last night. He has a customer (and himself) interested in building two more Spec cars for NorCal.



B

I have heard about the chassis difference several times, but I have yet to have anyone actually show me the difference between the two.

Remember:

Michael Lansky ran his Boxster race car HARD for years on slicks with PCA club racing. He didnt have an issue with the chassis (and I kept up with him/it) Once you tie the cage into the tub.. I think the potential issues go away.


B

CCW made Lansky's 18 inch rims. They already have the offsets on file for a stock bodied Boxster running 18 inch Radial slicks. $2K a set. Payback on a set versus tire cost of New Hoosiers versus used Radial slicks is about 2 years. That's for one set of rims.

Decisions.....

Bill P.

Just a minute while I fit this marketing hat on my head.

Wonder if a sponsor would want to invest that $4K in rims for the slicks?

Spec. Boxer finishing in the top 5 in one of California's hottest AutoX venues says something to potential customers.

Want me to do an ROI on that?

(Actually their break even (figuring 40% margin) is $10K in parts sales; or parts for 1 spec. boxer "conversion."

I want to learn how to go after the BIG sponsors.

What does it take?


B

Those guys in the "Legends" racecars do 1:56's at Sears on BFG street rubber.


KT

back on topic,

for my .02, i'd go with the narrower and stickier compound. less weight, no spacers needed (again, less weight)... you can dial in the handling issues other ways.

I'm leaning towards running the Hoosier A6's for AX and the R6's for the track. If I buy 2 more rear wheels, that gives me 2 sets of 8.5 inch rims that I can then spread the 245/40's in the front over and not have the "pinching". I then order a set of CCW's in 18" sizes and play with 18" radial slicks for the track. In this way I only have to spend another $2200 in rims, $2400 in tires (1 set of R6's, 1 set of A6's, 1 set of used Dunlop/Michelin 18" radial slicks) and I can begin tire testing!.....

What an absolutely crazy sport!....

I do believe the tire compounds offer so much more over another 1/2 inch to 1 inch of tread on harder compounds.

And of course phase II of Lucille involves either a TPC supercharger on the 2.5 or a 3.4 996 motor swap.

And then phase III would have the f/g mods to get the weight out of the car and address the aerodynamics of such a car.

And then phase IV involves selling Lucille to start the Cayman S track car project. No sense denying it, that will happen in the future when the prices for a used one come down.....

ssshhhh....don't tell Doris yet....

I'm a dead man....

Bill P.

I wont let that happen.. even if I have to call TPC/Michael Levitas and cancel the order myself!!

I worked on the first 2.5 car TPC built a kit for (SSI owner owns it) It was featured in Panorama way back..

The kit sucks.

The TPC kit for the 993 sucks (ask TonyC)

Mike Levitas doesnt have to make money with TPC. His wife is loaded


B

B,

What size radial slicks fits the 996/Boxster's? And what wheel width and offset for the 18 inch rims?

Doing my homework.

Bill P.

Spectators. Lots of spectators.

OK.

Michelin SuperCup sizes (measured in Centimeters)

Front : 24/64/18 S7A compound
Rear : 27/68/18 S8A compound

The front is typically ran on a 10.5x18 wheel. I dont have the rear info currently or the offsets. The fronts fit 986+996 with *some* rubbing of plastic depending on ride height.

More info soon.

Word has it.. getting the Supercup tires is pretty hard. Most of the "club racers" are buying Yokohama on the west coast. Good support and good supply.

I'll try to get pricing/sizing for Yoko and Pirelli. None of them use the same compound numbering scheme.... pain in the ass..


B