NEHA

I'm about to finally ditch the winter studded snows and put on my summer tires this weekend. Picked up some Evo 8 Enkei wheels recently and looking to run them as daily driver set with Bridgestone RE-01Rs, size is 245/40R17. . Question is, I have two brand new, sticker tires, and two 50%+ worn tires. Am I going to wear out my front-to-rear viscous coupling by running new tires in the front and 50% worn tires in the rear? Will the slight difference in circumference be enough to damage it badly, either short term or long term?

Any btdt experience with awd Mitsus (or Subies) given such a situation is much appreciated.

Also, at a hillclimb, what tires would you run? RE-01Rs or RA-1s? RE-01Rs would be my choice for autox for sure, because they work better at lower temps, but Okemo, Ascutney, and Burke should both be long enough to get RA-1s up to temp on a heavier car like a GVR4, yes?

I wouldnt run them if they are more than 1/8" different in overall diameter on a surface where they will have traction all the time(highway driving).. they would probably be fine for an autocross, as long as your sliding around breaking traction, letting the diff relax..

Good advice. I'll mount them up and run them only at the Storyland autox next week. After that and perhaps SLMP a month later, the fronts will likely be much closer to the rears in terms of tread depth.

custom tire shaving...you should advertise that..

The stock car guys call it ''STAGGER" - the circumfrence of the tire is measured with a flexible tapemeasure, string, or a special caliper.
tires should always be matched in pairs, particularly when locked or locking differentials are used. In an AWD situation, I would mount the larger pair on the rear, as the rear wheels take the longer path.
just as a car may be steered with side-to side stagger, handling in a locked AWD car may be adjusted by front-rear tire stagger or gear bias, like this early 70's Hite supermodified

http://www.retrorockets.org/1/imagelib/star069.jpg

Jim, sorry I haven't been on here in a few days. I've been working literally around the clock.

Having just run a hillclimb on both R comps and street tread in one day I can say that a really good street tire can be a contender. It seems like a lot of mornings are wet lately. I think that if I had a choice I'd use a street tire on those wet mornings. For dry however I would go with the R compound, ideally an autocross compound but even a normal track tire. The toyos are good but hopefully yours aren't too old since those are discontinued.

I hear great things about the new BFG and the new Direzza Star Spec tires.

Regarding the offset I'd go with Joey's advice. I tried to run different ODs at a time trial last year because I had no choice. The car hated me for it. John had a good suggestion also. You might have some success in staggering them front/back-left right. The front diff is open so it won't affect the front side to side.

I have a good selection of used tires for sale, both street tires and R comps if you ever need anything.

A

The word according to Rat:
(Charles)"Rat"" Lane was Bill Hite's favorite supermodified driver. According to Rat, Bill (the master designer of these creations) would figure the tire circumference and final drive gearing to slightly "lead" or pull the car thru the corner. This usually resulted in a slight push at the limit, and cornering speeds so high that Rat generally had to sandbag in qualifying.

Bear in mind, FWIW, that these Hite cars had no differentials anywhere, and they had to be individually set up for different corner radii.