• Advertisement

Chassis setup

Race/Repair Questions

Chassis setup

Postby HalM3 » Sat Jul 30, 2011 7:30 pm

Our BMW M3 sedan picked up the inside rear tires on the majority of the corner exits at Marina during the Zone7 weekend. What changes would you make to keep the inside tire planted?
We autocross and track our cars for you!
User avatar
HalM3
 
Posts: 246
Joined: Wed Jun 22, 2011 11:32 pm
Location: Vallejo, CA

Advertisement

Re: Chassis setup

Postby krote6 » Sat Jul 30, 2011 7:46 pm

more front bar or less rear bar Hal... what is corner exit like? understeer or over steer? do you have a limited slip?
User avatar
krote6
 
Posts: 2913
Joined: Mon Mar 29, 2010 7:25 pm

Re: Chassis setup

Postby HalM3 » Sat Jul 30, 2011 8:18 pm

Corner exit had very slight oversteer with our stock 25% lock up LSD. You can hear the inside excessive tire slipping in the videos from my runs on Saturday. On Sunday, the RS3 street tires were fine with the exact suspension settings. Rear 24mm bar is already full soft but we can stiffen the front 30mm bar two more settings. Just don't want any more corner entry understeer.
We autocross and track our cars for you!
User avatar
HalM3
 
Posts: 246
Joined: Wed Jun 22, 2011 11:32 pm
Location: Vallejo, CA

Re: Chassis setup

Postby krote6 » Sat Jul 30, 2011 9:31 pm

its always a compromise isnt it Hal..


can you add about 25 pound stiffer front springs?
User avatar
krote6
 
Posts: 2913
Joined: Mon Mar 29, 2010 7:25 pm

Re: Chassis setup

Postby HalM3 » Sat Jul 30, 2011 10:56 pm

I have a set of 600lb but went with the 550lb to reduce the understeer. I can stiffen the front bar, reduce rear rebound 1/2 turn for quicker shock travel. Stiffen rear compression.
We autocross and track our cars for you!
User avatar
HalM3
 
Posts: 246
Joined: Wed Jun 22, 2011 11:32 pm
Location: Vallejo, CA

Re: Chassis setup

Postby krote6 » Sun Jul 31, 2011 12:09 am

umm looks like the best first try would be the rear shocks .. slightly more compression slightly less rebound ..
User avatar
krote6
 
Posts: 2913
Joined: Mon Mar 29, 2010 7:25 pm

Re: Chassis setup

Postby grant » Tue Aug 02, 2011 10:57 pm

More front bar is best bet since you have adjustable front. Back off the rear bar and use compression settings on your shocks to add stiffness in rear. What kind of alignment are you running in the rear? If you have too much negative camber you may want to back off a bit so tires so light tire sits a little flatter. What do you run for tire pressures on your streets?
2010 Cayman S - Elsa
2015 Boxster S - Pearl
User avatar
grant
 
Posts: 5957
Joined: Wed Jun 30, 2010 5:04 am

Re: Chassis setup

Postby HalM3 » Thu Aug 04, 2011 5:46 pm

Our rear is toed in 1/8" and camber is set at -2.2. If I can't soften the rear bar I can stiffen the front bar one more position. Tire pressure: We run 39/37lb lbs hot in the street tires. We had 35psi all the way around on the r-comps but the track we run 40psi hot. I'm taken Olivia to the shop today to switch pads for Thunderhill and will check bars and the diff as well. We should see about 60lbs before the lifted tire moves (other tire on the ground and transmission in neutral), if it's far less then I get a 40% lock up rebuild...
We autocross and track our cars for you!
User avatar
HalM3
 
Posts: 246
Joined: Wed Jun 22, 2011 11:32 pm
Location: Vallejo, CA

Re: Chassis setup

Postby grant » Mon Aug 08, 2011 6:27 am

Running much toe out in front? I'd run at least an 1/8 of toe out. I run 1/4 on the Z. Tires: Hoosiers I run 34 front and about 32 rear
2010 Cayman S - Elsa
2015 Boxster S - Pearl
User avatar
grant
 
Posts: 5957
Joined: Wed Jun 30, 2010 5:04 am

Re: Chassis setup

Postby HalM3 » Mon Aug 22, 2011 9:53 pm

Diff was worn out, less than 10%. Having a 40% lock up diff built for the next event. Tow in front is 0 since we track her so often. Will try the lower tire pressurs hot. Comment: The Hankook V214 with C51 are a pretty good track tire but not as good as the BFG R1 were...
We autocross and track our cars for you!
User avatar
HalM3
 
Posts: 246
Joined: Wed Jun 22, 2011 11:32 pm
Location: Vallejo, CA

Next

Return to Questions/Repairs

Who is online

Users browsing this forum: No registered users and 1 guest

  • Advertisement
cron