Who's using 40 series tires for track and AutoX?

[skullandbones]

I'm curious to see if there is a trend to go to a smaller sidewall for more stability in general for perfomance. I recently bought some 275/40/17s and plan on using them for track day and AX if the opportunity is there. I may not like the low profile of these for the regular street tires. It looks pretty skinny. However, I was very impressed with the rock solid side wall. It must have some positive effects during the lateral forces on the roadster. I would like to get your opinions and feedback from your experiences with these or similar tire profiles. I have a 95 Co*** diff with 9x17 Co***R wheels. My last tire was a 275/50/17. It seemed to fill the fender gap better and I will probably go back to that or slightly larger side wall for the street tire. It's getting tight in there as configured. I might be able to squeeze some larger tires if I change rims that have all the added width in the back spacing. I will have to move my LCAs and shock mounts too (planned on doing that anyway).

Thanks for looking,

WEK.:cool::cool::cool:

[Jeff Kleiner]

255/40-17 fronts and 315/35-17 rears here. Ten plus years ago before the Mk3 was introduced with frame and body revisions to allow 315s the 275/40-17 was the "big" tire.

Jeff

[CraigS]

275/40 in front and 315/35 in back for many years now. The A6s and previous V710s are all run at 18-20 lbs for autocross so yes the sidewalls are stiff. I run the street Sumis at 20-22 so even those are pretty stiff and they are pretty much the bottom of the barrel performance wise.

[Mike N]

Same sizes as Jeff and Craig. Had V710's then A6's and now have NT-01's. The 17" lower aspect ratio tires are a lot stiffer and more responsive than the classic looking 15" set ups.

[edwardb]

Similar as others. 245/40 front and 315/35 rear on my Mk3. 255/40 front and 315/35 rear on my Mk4. Both are 9 and 10.5 inch rims. No complaints.

[skullandbones]

So I guess I'm behind the times. I will for sure be assigning these to track day/AX duties then. I thought the side walls were extremely stiff but when I saw the guy wrestling with the tire when installing it, I was completely convinced.

I never considered 275s on the front! It's crowded up there on the passenger side with the cold air duct so I will have to stay much smaller. Do you guys use a rack limiter of some kind?

I appreciate the historical perspective on this also. One more thing: how is this affecting how you do ride height? You effectively lower the car by this method but what about any other changes you need to do to make these work better. Mine is at about 5 1/2 inches in the rear so I see at least a 1 inch lowering but not sure about the front.

WEK.

[Mike N]

This is what 275 NT-01's look like on the front of my MkI. I think they fit very well. If you crank the wheel hard they will rub the F panel but you would only do that at very low speeds (parking) so it doesn't hurt anything.

33403

[edwardb]

I never considered 275s on the front! It's crowded up there on the passenger side with the cold air duct so I will have to stay much smaller. Do you guys use a rack limiter of some kind?

I have rack limiters on both my builds with 245s and 255s. Either will rub the F panel at hard over without. I can certainly imagine 275's doing the same. Easy enough to install. Just pull back the boot and snap them on. Is only a factor when parking as Mike suggested.


One more thing: how is this affecting how you do ride height? You effectively lower the car by this method but what about any other changes you need to do to make these work better. Mine is at about 5 1/2 inches in the rear so I see at least a 1 inch lowering but not sure about the front. WEK.

That's a little high. I run mine about 4-1/2 inches in the back back and 4 inches in the front. You shouldn't have any trouble if using a lower profile tire. Just adjust accordingly.

[Jeff Kleiner]

I have not known anyone to run a 275/50-17 before and after looking at the specs I see that they are tall, real tall at about 27.8 inches! Switching to the 275/40-17 will bring your ride height down at least an inch with no other adjustments; a Kumho XS in that size is 25.6" tall. I rub the splash panels in front at about 90% of full lock but it's a non issue---the only time it happens is when I'm doing a parallel park type maneuver to fit 4 cars in the garage, never during normal driving or even regular nose-in parking. Ride height wise I run 3 3/4" front and 4 1/4" rear.

What tires did you go with on the 275/40s?

Cheers,
Jeff

[skullandbones]

The 275/40/17s are Kumho Ecsta 4X. BTW: those Nitto 275/50s really fit well under the fender (no rubbing) but I do have my shocks pretty much maxed out height wise. I will be able to move the adjustment a little down if the tire size doesn't do it by itself. My ride height should be OK the way it is but I will lower it if needed. That will require moving the lateral links a notch down on the watts link. It never ceases to amaze me how moving a small adjustment here will cause the other components to require similar changes.

WEK.

[CraigS]

275/40 are a little tight. They will rub the f panel but no problem at parking speeds. You may need to crank in a little extra negative camber or play w/ ride height. I run 2.75 camber since I autocross a lot but the tires still last 3-4 years which is maybe 12-15,000 miles so I don't worry about extra inside wear. I have also had the tires flipped on the wheels to help even the wear some but that was a used pair I got from a friend.