Rear Wheel Contacts Splash Shield and more

[Boss4Me]

During an April open track event at Gingerman, the RT rear wheel contacted splash shield and W/H inner panel.

The body is centered over the axle with adjustable PHB. I had 3mm spacers on with Apex 19x11 EC-7 w/285 RE71-RS. Also the FP Pro Cal tune was installed for the first event, it definitely improved throttle response and the car felt like it had more torque.

My theory is the soft springs and shortened bump stops allowed the body to roll far enough to create contact.

I have started the purchase of higher rate springs with H&R RSS kit. Also 8mm spacers will go on behind the rear wheels. Hopefully the pieces show up for June events.

Any thoughts? Thanks.

 

[Dave_W]

I had that happen many years ago with stock Boss suspension, on borrowed 18x11 Vorshlag wheels with Hoosier 315s. Trying to fill out cars for a class in ProSolo class so my buddy could win a tire if/when he won the class. Guy I borrowed wheels from didn't tell me that the front wheels needed extended studs - I found out the morning of the event while trying to fit them. Driving in a ProSolo with 285 RE71s on front and 315 Hoosier A7s on the back is, um, interesting.

 

[EF1]

If I remember correctly James was running 305 wide tires on his Apex 19 x 11 wheels without rear spacers and didn't have any rubbing. Are you sure the axle is centered? Also, which springs and shocks are you running?

 

[Boss4Me]

If I remember correctly James was running 305 wide tires on his Apex 19 x 11 wheels without rear spacers and didn't have any rubbing. Are you sure the axle is centered? Also, which springs and shocks are you running?

The springs are Eibach Sportline on OE probably original shocks.

Sportlines lower RH and levels front to rear but are pretty soft for track. Frt 180# Rr 100-220 progressive.

Turn 6 at G’man is pretty slow left turn. Twice that day the left front lifted on corner exit which probably too much body roll on soft springs to keep the wheelhouse away from the inside of the wheel. I also have the bump stops cut low due to lower RH minimizing the gap from bumper to frame rail.

I have taken time to get the body square over the axle as part of the string alignment for toe.

 

[EF1]

The springs are Eibach Sportline on OE probably original shocks.

Sportlines lower RH and levels front to rear but are pretty soft for track. Frt 180# Rr 100-220 progressive.

Turn 6 at G’man is pretty slow left turn. Twice that day the left front lifted on corner exit which probably too much body roll on soft springs to keep the wheelhouse away from the inside of the wheel. I also have the bump stops cut low due to lower RH minimizing the gap from bumper to frame rail.

I have taken time to get the body square over the axle as part of the string alignment for toe.

Those spring rates do seem pretty soft. James was running Bilstein kit from Vorshlag with Eibach Pros. I run 285 wide tires with Apex 19 x 10 wheels with Steeda Comp linear rate springs. They have less offset than the 19 x 11 wheels, but I have plenty of clearance.

 

[KazarS197]

I see you have the Kenny Brown sway bar delete kit. I was looking at your build profile photo - how much drop 1 or 1 1/2? I wonder if it's a combination of both along with the shorter bump stops and soft springs that's causing the rub. The first pic is your rear on what looks like a strait. The second is me on 305s with no rubbing on 18s or 19s. I'm at 1 inch drop. You might sit a bit lower.

 

[stevbd]

I doubt it’s the springs. I used to run variable rate FRPP P springs with 305/30/19, no spacers, and no rubbing. Dumb question but the liner is secure and tight against the body of the car, correct? Did you make any adjustments on the rear LCA’s? The axle and wheels are centered front to rear?

 

[Boss4Me]

I see you have the Kenny Brown sway bar delete kit. I was looking at your build profile photo - how much drop 1 or 1 1/2? I wonder if it's a combination of both along with the shorter bump stops and soft springs that's causing the rub. The first pic is your rear on what looks like a strait. The second is me on 305s with no rubbing on 18s or 19s. I'm at 1 inch drop. You might sit a bit lower.View attachment 95466
View attachment 95467

The rear is low and maybe too much with soft springs. With the Eibach’s, the rear RH is 1/4” higher than the front. That is about where I had the Boss set with RH adjustable H&R RSS kit and KB rear grip kit, no sway. Spring rates for the H&R kit are 630#F/515#R. On the Boss I had smaller 18x10 Apex with 275 Nitto 100tw without any rub.

After experiencing the H&R spring rates on the Boss compared to these soft springs, I wanted to go softer than 630#/515#. Although the set up is not directly comparable between the two cars, I do think the softer springs give a more stable feeling on corner exit.

 

[Boss4Me]

I doubt it’s the springs. I used to run variable rate FRPP P springs with 305/30/19, no spacers, and no rubbing. Dumb question but the liner is secure and tight against the body of the car, correct? Did you make any adjustments on the rear LCA’s? The axle and wheels are centered front to rear?

I installed the KB upper link and lower LCA’s as shipped without adjustment as they suggest. I did a string alignment twice, once after I paid a local shop to measure and set toe and again after the I installed the front LCA’s. I did not measure the length axle to axle.

Regarding the shields, I tie strapped the LT side as it had light contact on an earlier track day (pic of left). No tie strap before the contact on the RT. The picture may not be clear but the wheelhouse metal was contacted which is difficult to see through the openings in the shield.