Tire time

[theunz]

When I bought my Falken Azenis RT615’s I thought they would age out before they wore out, I was wrong! They wore out right around the 5 year period that I consider them aged out. They did give me excellent service for the approximately 3,000 miles I put on them. Now to be fair, they were wearing pretty good with some spirited driving and a once a year track event (LGGPR). But then….
about a year ago I decided to start autocrossing! On top of that the area we use is concrete and large enough to get some speed up.
Things I learned.
Autocross is hard on tires.
Understeer is very hard on tires.
Understeering all the way through long fast sweepers is extremely hard on tires.
Tires are expensive.
Backing off a little when understeering will save your tires, and probably improve your lap times.
Oh yeah, autocross is great fun despite the destruction of tires.

Here’s some pictures of the old Falken’s and the new Falken 660’s.
Can’t wait to destroy ‘em

[jr02518]

Congratulations on your new set of tires. I am on my second set of 660's, they do need some miles on them to scrub off the mold release and they do reward you with longer life if you heat cycle them before you use them at an event. They are a very nice 200tw tire that will reward you with lots of grip,

I have flipped the tires on the rims to take advantage to both shoulders on the tires. The lack of camber and fast lap times come at a cost. What tire pressure have you run in the past?

On a side note, I found that they will flat spot if you leave the car not driven for a number of months. They go round again after a few miles, but you will feel it.

Yes, not the roadster but having a car that relies on momentum is lots of fun to drive. Enjoy!

David

[rwmann]

What tire size in the roadster application?

[Cyclewrks]

Negative camber/ positive caster are your friends for autocross. Normally I will run -2.5 camber and around +4-5 caster autocrossing and about -2/ +3-4 on track days. These settings will eat the inside shoulders of the tires on the street, if I am going to do a bunch of street driving I will dial everything back to _1.5/ +2.5.

[theunz]

David, I have been running 28 or 29psi. Usually I run 1lb less in the fronts, this keeps the rear loose enough to predictably rotate in tight turns. I did have Tire Rack heat cycle the 660’s when I bought them and will definitely keep a closer eye on them and rotate more often. Also I will be installing new tie rods and a new center link along with the Apex engineered quick steering arms over the winter. That will leave only the steering and idler boxes that aren’t new. Thanks for the advice.

rwmann, the tires are 195/60/14 and fit with no fender interference, but they do just slightly rub the 23mm front sway bar at full lock.

Cyclewrks, thanks for the alignment info. Since my roadster spends about half its time on the street and half at track or autocross events, having the car aligned every month is cost prohibitive. Any advice for a decent compromise?

[Cyclewrks]

I have all my shim setups labeled for position and it is fairly quick to jack the car up and add the ones needed for a particular setting. Winter project will be machining one-piece plates for each setting so I can just loosen the two bolts, pull out one plate and swap for another rather than dealing with a lot of different shims. spend a little time on the alignment rack and determine what size shim gives a .25 change (unfortunately it isn't the same from car to car, heck it's not even the same side to side on the same car!) and then it is easy to make changes at an event.

[jr02518]

Mike,

There are so many variables when you start to dive into auto cross events. The track surface, tarmac or concrete, course length and design. I am always asked why I do it? Being in a corner its lots more fun than driving to a corner. That and driving at the limit on the street is a phase I have survived.

I have driven cars to this point that have a LSD and some variation of a independent rear suspension. It has been years learning the keys of trailing throttle oversteer with next to no horsepower. Now I will have an open diff., solid rear end and again no horsepower.

If I could ask, what are the specs on your rims and wheel studs/lug nuts?

Thanks.

David

[rwmann]

Thanks, @theunz. I am working Bridgestone RE71 195/55R14 fronts and 205/60R14 rears, with advancing tire age staring me in the face.

[SLOroadster]

The I have nothing good to say about autoXing on Falken 615s. They were crap when they were new, like driving on ice when they were old. When I went to my first set of R compounds the car went from a tail happy end swapping monster to a competitive car that was 12 seconds faster per run. The only time the Falkens were even sort of okay was in the rain (I still had to run a 2nd gear course in 3rd gear to keep it pointed the right direction.)

Sadly the Falkens are the only 14 inch street tire out there now. Hence the reason I went to 15 inch street wheels. That said, the car doesn't handle as well on 15s, and does look goofy. Sadly 14 inch R compounds are hard to find now as well. (I run 225/50/15s, 205s will work, but the car wants a bigger footprint.)

As for camber, caster, toe settings, its the toe that eats tires, not really the camber. I run nearly 3 degrees camber on my BMW M3 street car and get 30K miles out of a set of Dunlop Direzzas or Hankooks. I have zero toe however. For a roadster, I'd guess -2 degrees camber, all the caster you can get, and zero toe would be a good setup. I have -1.8 degrees camber and chew the outsides of the tires up. They wear LONG before the insides do. Clearly more camber is needed. I've run this same setup for both autoX and track use. It handles great for both now, but as I said, I eat the outsides of the front tires. I think I'll push it to -2 degrees and see how the wear is.

Will

[Pjackb]

you may enjoy this read
https://grassrootsmotorsports.com/artic ... and-track/

[theunz]

David,

Since your asking about the specs including lug nuts and studs, and not size and offset I’m going to assume you’re questioning their strength for the rigors of autocross. The wheels are EMPI 2 piece pressure cast aluminum and were built for 60’s and early 70’s Datsun’s. Specifically the roadsters, early Z’s, and I believe 510’s. Bob Bondurant thought enough of them that he used them on his school Datsun’s. The lugs are aftermarket Dorman’s (IIRC) and completely fill the lug nuts I bought from Summit Racing. While I realize that 50 year old wheels are not the best option I feel that they are safer than some of the cheap import wheels seen on much higher powered cars.