AutoX Issues

[Mr_Boom]

I think a few other MS3 owners on here currently or previously have done some AutoX racing, and so I was wondering what kind of suspension mods have been done and what type of results some AutoX drivers have seen.

Just completed my 2nd AutoX today, which happened to be on a pretty bumpy parking lot (1st race was on a smooth asphalt lake), and had some issues with the rear end bottoming out on my tires (currently running 245/40R18 R1's on 8x18 wheels) and cutting some grooves on the outside edge. I had a small issue with this problem at the last autocross, but nothing like this with the bumps in the lot. Already rolled the fenders some, but the stock springs in the rear are so soft it looks like more of a suspension issue anyways (already run DSP, so most mods are fair game).

So a few questions...
- Has anyone else experienced this same problem?
- If so, what did you do to fix it (springs / bumpstops / etc.)
- What type of suspension mods have you added for AutoX racing, or what would you suggest? (I'm looking into the Cobb Springs w/ Sway Bars).

Thanks for the input.

 

[Snyeed]

I would look into getting some Coilovers and upgrading the Swaybars, What tires are you running? Tires play a huge roll in autocross.

I had Cobb springs but they blew my shocks out over time, I then upgraded to BC coilovers and couldn't be happier. I should have just got coilovers in the beginning.

 

[xelderx]

If you had trouble with tire clearence at Knights Stadium you are going to hate Carowinds. I'm not sure springs are going to solve the issue. Even though aftermarket springs are usually stiffer, they will also lower you car which will cause more interference. A stiffer rear swaybar is probably a good place to start. Even if it doesn't solve the rubbing issue it will help the handling. With the size tire/rim setup you are running it's going to take a pretty big investment in either suspension or body work (or both) to get it to work properly.

Wait a sec...you are running this tire?

 

[Mr_Boom]

If you had trouble with tire clearence at Knights Stadium you are going to hate Carowinds. I'm not sure springs are going to solve the issue. Even though aftermarket springs are usually stiffer, they will also lower you car which will cause more interference. A stiffer rear swaybar is probably a good place to start. Even if it doesn't solve the rubbing issue it will help the handling. With the size tire/rim setup you are running it's going to take a pretty big investment in either suspension or body work (or both) to get it to work properly.

Wait a sec...you are running this tire?

Yeah I'm running on BFG R1's...long story short I work for Michelin and instead of blowing $1100 on a new set (and blowing all my incentive money for 5 years) I bought some used tires (~60% tread left) from a friend for $250 (+$400 for some cheap 8 x 18 rims). Only issue is they were 245/40R18 instead of the 225/40R18 size that I would probably buy. Thought I could make them fit...but I'm starting to find out otherwise.

 

[xelderx]

It's a tough call. There are a lot of options, but none of them are simple or cheap. With stiff enough springs and some camber in the back you could probably get them to fit. It really depends on what direction you want to go with the car. If it was my car and I was very serious about continuing to autoX a lot I would sell the whole 18" wheel/tire setup for now and concentrate on building the suspension. That way when you do go back to aggressive tires you aren't destroying them after 4 events. That actually applies for just about any tire. You drive a heavy, high HP FWD car. You are going to need some front camber and a lot of roll stiffness. Think springrates and rollbar rates more than twice what you have now. Run street tires until you get that done and then if you want R-comps again go with no more than a 17" rim.

If you aren't that serious about racing then save yourself a ton of cash and run in the TIR classes. You can do all the DSP mods, but not have the DSP tire budget.

 

[lutexas]

I have the Koni sports + eibach pro kit in 18x8.5 235/45/18 and cut rear fenders.

I have only participated once in an autocros but I didn't any problems with this setup.

 

[chodaboy1980]

I have autocrossed my car at about 10 events or so. I have stock shocks and springs for now, but I have the Cobb front and rear sway bars. They are both set on the softer of the 2 settings. I used to just have the rear bar. It made the car a bit too tailhappy in the wet. With both bars it feels great. Eventually I plan on getting the mazdaspeed coilovers.

I recently rolled the rear fenders, though I never had that much of a rubbing issue. For wheels and tires, I have 18x8 Rota torques (20lbs each) with a +48 offset. I am running the Dunlop Starspecs in a 235/40/18. They stick like crazy once they have a run or 2 in them. I run about 42lbs in the front and about 32lbs in the rear. It slaloms awesome with these settings. Instant response and the rear rotates just enough.

Some of the other mods that I have are Cobb SRI, Cobb shifter counter weight (best $35 I ever spent, no more gear popout under heavy braking FTW), trz poly rear mm, twm shifter bushings, redline MT-90 gear oil, and turbo xs race pipe.

 

[Mr_Boom]

Thanks for all the info. So far I've competed in 3 autocross events, won Novice at my 2nd event by a good bit so I went ahead and made the move up to DSP to take my ass whippin' for a while. Performance Mods so far include Cobb SRI, TRZ Poly Rear MM, & Straight pipe exhaust. Just ordered my Cobb Rear sway bar and planning on saving up for the front bar next.

Looked up my wheel specs for AutoX and they are just some cheap alloy wheels I found on eBay. Wheels are 8 x 18 with +40 offset. Could this offset be causing part of the problem?

Noticed some minor rubbing at the first two events (rolled my fenders just a little bit after these two) but this got a lot worse at the 3rd event due to a non-flat parking lot. Current plan is to...

1. Do a complete fender roll (first time I only moved it up a cm or so out of the way)
2. See if the 245/40/R18 tires can be mounted up on the stock 7 x 18 wheels I have in the garage (I know it seems unlikely, but have a few friends who are running 275's on 7 in. wheels in a Honda S2000.)
3. Order a couple of 225/40R18 R1's to run on the rear (have no rubbing issues with the front) with the OE wheels.

Here's a video of the Knights autoX
http://www.facebook.com/video/video.php?v=652365661948&ref=mf

Thanks again for the help and I'll let you know how everything turns out.

 

[xelderx]

You can mount those 245s on the 7" rims, but it sounds like you can do a lot more with you fenders. Street Prepared is a fun rule set to race under.

 

[Mr_Boom]

Update:

Well I ran the autocross this past weekend in Florence, SC with the 245/40R18 tires mounted on the stock rims. After rolling the fenders last week I had no problems with any rubbing while I was running, so I think this problem may finally be solved. It's nice to finally be able to focus on driving instead of having to worry about tearing the car up.

Now, the next issue I need to work on is with the transmission popping out of 2nd gear when I brake hard going into some corners. This happened a few times on Sunday, and it gets pretty annoying when you go back to the gas and nothing happens. Had one of my better runs ruined by this when I couldn't get the car back in gear and just had to coast across the finish line. I know Cobb makes some upgrades to the shifter, so I'm going to check into those and see if this will fix the issue.

 

[xelderx]

It is probably a motor mount issue more than a problem with the shifter. I would try replacing at least the front and rear mount to stabilize the motor/trans.