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Autocross beginner: Slick tires? Any problems?

5
6
Exp. Type
Autocross
Exp. Level
Under 3 Years
Germany
Hi!

I've bought a 2007 Mustang GT a month ago. It already came with some suspension upgrades: 1" Ford lowering springs with matching dampers, adj. panhard bar, BMR upper control arm.

In the last two weeks i visited two autocross events and it was surprisingly good. The car felt good, it was fun to drive and the times were quite fast, too.

There were just two problems:
1) The car had a tendency to understeer
2) I think it was too much for the 245-40-18 street tires

I`ve read, that the S197 will work very good with wide tires. In almost every class in germany slicks are allowed. So i was thinking to get some cheap used wheels (maybe the 9.5" from the GT500?) with some used slick tires to try it? Will i run into other problems such as oil pressure problems? Is the suspension too soft for those sticky tires?

Due to the understeering: Would a thicker rear sway bar work or should i buy some coilovers to get a real improvement? At first i wanted a ST XA suspension which i could get it cheap. But after the autocross sessions i thought, that the stock suspension is not that bad for the beginning.

What do you think about my plans?

Thank you very much!
Bye,
Daniel
 

Mad Hatter

Gotta go Faster
4,018
2,513
Santiago, Chile
245-40-18!!!! Ye gads.... I would say the bare "marginal" minimum would be 275/35-18 or 275/40-18, but a square 295/30-18 or 315/30-18 setup is muuuch better bet.

If you have the ford P springs with matching shocks you can go to 295+ with no problems, including slicks. You might need a larger front roll bar though with the fatter tires. Its funny but with the right mods the car, you can race against all kinds of nice German cars (Amg c63, all the caymans, e90 M3 etc etc). A brake upgrade would help as well, the 14" 4pt Brembos would be great for autocross.

Ok, well. the Cayman GT4 needs a longer list of modes... but still very doable.
 

Dave_W

Cones - not just for ice cream
418
404
Exp. Type
Autocross
Exp. Level
20+ Years
Connecticut
If you keep at it, you'll eventually want 18x11 wheels with 315-wide tires. If you are okay cutting & flaring fenders, you could even go up to 12-13" wide wheels and 335-345 tires. But finding some cheap 9.5" wide wheels in 18 or 19" diameter is a good middle ground as you develop your skills, and can be used as "street" wheels when you get the wider "race" wheels & tires later on.

For autocross, if it's anything like here in the U.S., the runs are typically 50-90 seconds, so you need a tire that has good grip at nearly ambient temperature. Most true racing slicks designed for track use require higher temperatures to "come in" and get sticky. The go-to tire here for the classes that allow tires with any treadwear rating, as long as they comply with US DOT (Department of Transportation) standards so they are technically street-legal, is the Hoosier A7. For full-race (not street-legal) slicks, you want as soft a compound as you can get; typically a "qualifying" tire.

Do you have camber plates installed? If not, definitely get some. The increased front grip from more negative camber may cure your understeer, and it will also help your tires last longer by not grinding the oustide shoulders down to the cords on hard turns.

My Dad started autocrossing (called gymkhana back then) when he was stationed in Germany in the early 60's. They used empty 55-gallon oil drums instead of plastic cones. Cars were made from thicker steel back then.
 
1,148
933
Exp. Type
HPDE
Exp. Level
5-10 Years
Philly Metro Area
The GT500 wheels are heavy and may be expensive compared to aftermarket wheels. I don't know what you have available in Germany or what can be shipped to you. If you're in the US military with an APO address then its probably not a problem. Apex 18x10 wheels are probably the best value but if they are expensive then the American Muscle 18x10 AMR wheels would work in an autocross setting. LMR SVE Drift wheels are probably a little stronger but they only come in 19" sizes (there may be some used 18" ones)

If you want to maintain the same effective gear ratio, then consider the Falken RT615K+, Falken TR660, or Hankook RS-4 in 295/40-18. If not, then the sizes mentioned above will work too. Depending on your camber settings, you may be able to get away without any spacers up front or perhaps just 3mm spacers. At least for the RT615K+. The Hankooks are a smidge wider. 305's and above you will need 20-25mm spacers and longer wheel studs.

Also agree with the 4-pot Brembo upgrade. I would also recommend the rear 13.8 GT500 rotor upgrade with the relocation brackets offered on eBay. "ncmustangparts" sells them but I don't see any listed under his name at the moment. There are others than offer them on eBay but I cannot speak to their quality.
 
5
6
Exp. Type
Autocross
Exp. Level
Under 3 Years
Germany
Hi!

Thank you very much for your responses and knowledge!

Camber plates... Yes. I could feel with my hand, that the outer side of the tire was warmer than the inner side of the tire. o_O
I could get the ST XA for 1250 Euros, with camber plates maybe +200 Euros extra. Buying seperate camber plates would be more expensive. :rolleyes:
But camber plates alone could solve exactly my problem... 🤔

Coz: I have no APO address. Shipping cost for wheels would be too much and maybe the wheels will not be street legal here and the market here should be big enough to get used wheels in the wanted dimensions. I just have to wait. And i have to wait until march, because then is the next autocross event. :)
Thank you for the recommendations about the tires. To stay street legal i have to match the effective gear ratio but for the autocross event there are no rules for the tires.

The car came equipped with the S550 14" 4 pistons disk brakes (not brembo). Is the upgrade to brembo really worth it? Thanks for the hint for the rear rotor upgrade!

And there are really no problems with the engine with oil pressure in hard braking / cornering? Or other problems?

Nice fact with the Caymans and M3s. :) I have to try that!

The competitors here drive mostly with old and light cars like a Opel Kadett C, Ascona and VW Golf 1. The heaviest car was a E36 compact. Newer cars were in the stock class, but i am not allowed to drive there, because the Mustang never sold here by Ford and therefor there is no number of the car certificate.

Thank you very much for the good informations!

Bye!
Daniel
 

Mad Hatter

Gotta go Faster
4,018
2,513
Santiago, Chile
The car came equipped with the S550 14" 4 pistons disk brakes (not brembo). Is the upgrade to brembo really worth it? Thanks for the hint for the rear rotor upgrade!
Those would be fine as long as you are using the calipers and not the disks with the vents on the out side. Those tend to overheat very quickly! Would agree strongly with the camber plates... they are worth the money as you can kill a set of tires in a day without them.

Have fun!
 

Bill Pemberton

0ld Ford Automotive Racing Terror
5,763
4,303
Exp. Type
W2W Racing
Exp. Level
20+ Years
Blair, Nebraska
Tire wise when you say slicks are you talking about pure race rubber , or are you considering other options like a DOT Hoosier A7 or R7 ( A7 is the hot ticket for auto crossing). The notes on wider wheels are quite correct to help with some of your concerns though you will need to upgrade to ARP studs, and wheel spacers up front. If it is a wide open field in Deutchland then an A7 Hoosier would be the ticket. Many of the pure race slicks actually would take longer to warm up than the Hoosier. If you want a 200 TWR tire I would suggest the RT660 Falken as Coz mentioned as one choice, though I would have to politely disagree against the RT 615K or the RS-4 as they are older generation tires and the RS-4 is great for track time, but is not a contender for autocrossing.

Hot tickets at the Solo Nationals are the Yokohama A052, BFG Rival S 1.5, the Falken RT660 for 200 Treadwear and if you go all out the Hoosier A7 is the " Gold Standard " for DOT Comp. rubber.

Keep us posted and where do you run the auto crosses in Germany?
 
1,148
933
Exp. Type
HPDE
Exp. Level
5-10 Years
Philly Metro Area
I would have to politely disagree against the RT 615K or the RS-4
You're right Bill and the only reason I mentioned them is because I mistakenly thought his stock tire diameter was 27" and those tires are about the only ones made in 295/40-18. I was probably thinking about the diameter for a 245/45-18 instead of a 40 aspect ratio. Therefore the 295s are not even relevant. My apologies.

And don't be so damn polite!! It makes me feel even worse. Probably part of your diabolical plan! 😉
 
5
6
Exp. Type
Autocross
Exp. Level
Under 3 Years
Germany
Hi!

The Yokohama A052 is available here in germany. The others, especially the hoosiers are really hard to get here and would not be street legal here. I don't know exactly if i will go to full slicks or street legal tires. The "real" classes from the main motorsport association allow full slicks in every class. But there are "clubsport" classes with not many rules for people racing only now and then and in those only street legal tires are allowed. But i don't know if they would be that interesting, because the distance is limited to 1000 meters (0.6 miles) and only a few cars will start there. But it would be nice to drive to the event without the need to change the tires there. Maybe for the beginning something like the A052 would be good enough and simple to handle for the event...

Keep us posted and where do you run the auto crosses in Germany?

Of course I would like to keep you updated. :)

I live near to Düsseldorf and the dutch border. There are many events here. Funny that i have not noticed the whole autocross scene in the last 20 years. Just driven some trackdays at the Nürburgring and Zolder in belgium a long time ago. It's a shame because autocross is very easy to participate, fun to drive and not that dangerous. But it's never too late. :)

Thanks and bye!
Daniel
 
Before making mods, carefully check out the classing rules for events you’ll be running. You said no tire restrictions, but with other changes, make sure you’re making good decisions for your personal situation, with regard both to your budget and the car’s capabilities.

That said, those 245 tires are killing you. Not nearly enough rubber. Going with sticky rubber, 305 or 315 square, will alone make you MUCH faster. Get some good negative camber dialed in....even better. You might want to stop right there and just run a season and learn to drive. You’ll gain more from lots of seat time at this point then you will from expensive mods.
 
5
6
Exp. Type
Autocross
Exp. Level
Under 3 Years
Germany
Thank you very much! For 305 tires i would need something like 11.5" wheels. Those would be quite hard to get for me and it would be not that easy to fit those under the car?! 🙁
 

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