Im starting to autocross but do not have a trailer yet so Im looking at getting a pair of either 295 or 305 30 19 probably michelin ps2 to put on my stock srt rim to drive to the track race on and drive home. Im curious to see if anybody is running this size on a stock rim with no problems? I understand I may need a small spacer, hopefully not.
So my real question is, anybody running 305 30 19 on the stock rim? any rubbing under acceleration?

 

WHY??????????????????

If your autocrossing you want both ends to turn and oversized rears are not the ticket, I have 18 245 on both ends so I can rotate and save the tires from one sided wear. Big tires is for straight tracks. I went to the wavetrack to get more looseness in the back and to be able to drift the back since the front dont know how to turn.

Weekend Woody

 

You probably have a decent tire and a cent track, I used the stock 255 last weekend and spun the whole time, and I cant go to a smaller stickier tire cause I need to drive 120 miles there and back. I was up there with another srt6 who ran 295 30 19 and 235 45 18 and finished 8th overall so i figured id try what seems to work

 

Well, he might have finished 3 or better had he ran a different tire. Run what works for you, not the other guy. Woody has thousands of laps in his XF and can be of good help if you listen...no side wall isn't something I would want to run if autocrossing...nothing less than 35 for me...good luck either way, we are trying to help...There are several autocrosser's on here...some solo... I would love that 305 for drag racing...

 

I understand, and was not trying to be rude in any way, if so sorry about how it was stated.

 

Autocrossing eats up the outer edge fast. I have same size and can drift and turn corners that my 275's could not do. Doc got me onto walmarts 10$ tire change and I use them to flip tires round to use the OTHER edge after the first edge is showing weas effects. Woody

BTW the wavetec will reduce the spinning too.

 

I run the Hoosier 295/30/19 rears and Kumho 235/35/18s fronts with stock brakes, stock allignment and stock shocks. With a simple blip of the throttle the 295 will rotate the rear and 4 wheel drift if that is what you want, but it also allows you to put the power down and drive hard out of the corner when you can take advantage of a straight away.
The 235 and 245 clear in the front and give you the rubber needed not to understeer as long as you do not cook the entry. This set up has allowed me to win the SCCA BS class in several states at different event locations over the past few years and this is with less then 10 events run on the SRT-6. If I were to become serious I would run this tire setup with an autocross alignment and better pads.
Depending on governing rules (SCCA, NASA, Club) the wavetec and other locking rear aids may not be permitted. SCCA Stock classes do not permit this mod and NASA moves your class if you run over size tires. Look into your governing rules as a step in class may also require $3-8K in additional mods to stay competitive.

 

I agree with all you stated here...but, I just wouldn't mention the wavetrac if you do add it...it's not a part that is exposed, and truthfully, not a real advantage in autocross, solo, etc... The advantage comes in for drag racing more so... Vettes, Camaros, Mustangs, etc already had lsd rearends, so I don't see fuss over this conversion anyway...

 

Beofre getting into a Crossfire, I was active in the Mini Cooper S Community. The Mini is a great autocrosser, but at the limits had a bad understeer. To fix those cars, just about anyone who raced autocross or road raced, installed a stiffer rear sway bar which made a big difference. The road racers stayed with the stock 17" wheel while the autocorssers all went with the lightest 16 inch wheels they could find. No one went up in tire size as keeping the unsprung weight down was the prioity. With the understeer of the Crossfire, has anyone been expirimenting with a larger rear sway bar? BTW, most of those racers were also using my brake kit that I was selling back then.

 

Since we will be under there next week, I might take a look at the rear end to see if there is a way to stiffen it. Never really had any reason too as I don't round track all that much. But there might be a way to do it. I will be looking at the strut mounts...as well. We might have some access to old sway bars from other makes...but, usually not a good idea to cut and weld on sway bars...they need to be one piece... Maybe a solid brace like used on the engine bay would work....but, they has to be some give in there, or it will snap at the mounts... Something to play with I quess...

 

I wouldn't mess with the original sway bar unless you can find a way to shorten up the side of the sway bar where it mounts. I believe H&R or someone makes a sway bar for our cars or the SLK which will work. I don't think you can cure understeer with a larger rear contact patch. Understeer is somethng just about all cars have designed into them for saftey. I think Woody got it right buy going bigger in the front and smaller in the rear from stock. A stiifer rear sway bar might be an even better way to go.

 

Doc, the Wavetrac is supposed to be the cat's meow for autocross and solo. I can't get hard on the gas because I spin the inside wheel. You have to be pushing real hard for that to happen but when it does it really slows you down. But I, and others, will have have hard data soon.

Les

 

Les, since this is the first car I have owned without lsd, I really don't think it's a huge difference in performance. It will make a difference in your handling on the sharp switch backs, hairpins, for sure, but that is just bringing you up to par with all those that already have it standard.

 

If you are the type of person who is going to race within the rules, don't forget the rule book when you make your choices. SCCA Stock Class rules permit changes to the front sway bar but not the rear, not even modification of attachment points. NASA permits changes to the sway bars but no rear tire above 255 if you want to stay in class. A limited slip diff would be very benifical in BS and other cars in class have LSD, but since the crossfire did not have a LSD offered from the factory it cannot be added without cheating. SCCA Stock requires use of the same rim size, width and offset as stock, if not I would be running the smallest, lightest and widest rims I could fit on the car. Although drifting is fun, it is seldom the fastest way around the course. I have raced against more then one heavily modified SRT-6 running 245's on all 4 corners and have beat them by several seconds on sub 60 second autocross tracks.

 

There are cheaters in racing? Who would of heard of such a thing? LOL.....

 

My best day at the autocross track ever was racing a 1995 F - Stock Camaro in Hawaii. There were several regular cars in class Mustangs, Firebird, GNX and such. I had been running second all year against a police officer who everyone new was significantly modified outside the rules. He also owned a performance shop for F bodied Camaro/Firebirds and would dump another 3-5 grand in his car when ever anyone got close to his times, the guys at his shop would always let us know. The day I beat him with my within the rules car was a great day indeed, I like beating cheater most of all.

 

LOL Doc, You don't want to know what I was thinking. I guess anyone who ever raced NHRA in the '70's should be banned from all forms of racing

 

Don't know if it's my upbringing or 30 years of military service, but it's just not for me. Don't get me wrong, if there are gaps in the rules then I will play within them. But if the rule specifically calls out no LSD addition then I will not add a LSD. Autocross is stricktly a gentalmens sport, the only prizes are bragging rights, respect, friendship and personal honor.