BDR front strut with built in camber issue

fortpittclassic · #1 (**permalink**) 03-16-2023, 07:05 AM

Hello,
We recently received a customers Backdraft Cobra for service. He wanted tires replaced and an alignment. The car ran really low for some reason, so we did a chassis setup to bring the rake back into place. This allowed us to perform a sublet alignment.

The specs came back and showed me camber issues. The left front was .75neg and the front right was 3.0neg. I combed over the car relentlessly and finally came to the realization that the struts have "build in camber" (not adjustable) and the left was different than the right.

Is this a normal occurance? Is there a street strut and a racing strut? I've searched and havent come up with a good answer. I've talked to Iconic about parts, but they havent returned my email for a week now. So, I'm hoping I can find some help here.
Thanks!

cobragene · #2 (**permalink**) 03-17-2023, 09:25 AM

Don’t know what front suspension you have but I have a Mustang II with strut rods connected to outside of lower control arm back to the frame,I search high and low for an adjustable strut rod, they make one for older Mustangs but not M II. So I had turn buckles installed in the middle of my strut rod to make caster adjustments. Hope that helps good luck

fortpittclassic · #3 (**permalink**) 03-17-2023, 09:27 AM

I've run into that issue before and did the same thing. Unfortunately, this is M3 BMW and I believe the strut bodies are proprietary to the kit.

cobragene · #4 (**permalink**) 03-17-2023, 09:29 AM

Don’t know what front suspension you have but I have a Mustang II with strut rods connected to outside of lower control arm back to the frame,I search high and low for an adjustable strut rod, they make one for older Mustangs but not M II. So I had turn buckles installed in the middle of my strut rod to make caster adjustments. Hope that helps good luck. PS I just noticed you said camber not caster. Sorry

strictlypersonl · #5 (**permalink**) 03-17-2023, 06:21 PM

If the angle of the strut relative to the axle centerline is consistent from side to side, the only fix is to modify the upper strut mount (or the lca inner pivot) somehow. 2 degrees change requires about 3/4" shift at the top or bottom.
*How is the strut connected to the upright? Any slots for adjustment?

FlyingGumby · #6 (**permalink**) 03-18-2023, 02:05 PM

Backdraft’s come with BMW e36 suspension except the newer builds. Adjust front camber by raising/lowering the spring collars. Will obviously change wheel gaps and balance. Can also dial in with shims or camber plates. Several threads on the topic.

Good luck.

fortpittclassic · #7 (**permalink**) 03-20-2023, 05:18 AM

I think thats what someone did, turn the coilover to alter the chassis to correct for camber. Bad! I had left front 46t from zero preload and right side 3 turns.

I've determined that my left and right front struts are different with different build-in camber based on the angle of the lower mount to the strut body. I'd rather fix this before moving to camber plates since there's a little bit of motion ratio that would be effected left to right.

Unfortantely, I cant upload photos at this moment... I've got a good comparison left to right showing the difference

FlyingGumby · #8 (**permalink**) 03-21-2023, 10:49 AM

Rereading your original post... sounds like adjustments were made to raise the car and add some rake. That would definitely throw things off. Adjusting for visual wheel gaps impacts things too. These cars are not always square.

The difference in spring collar heights will impact camber that much. Lower the left side to get more negative camber. Raise the right to decrease negative camber. May get close to spec with just those adjustments. Raising and lower the rear has a similar effect.

My car is aligned and corner balanced. Set front camber to -1.9 by adjusting the collars and adding some e36 shims. Rear is -1.4 using adjustable camber arms. Car tracks straight and handles great.

Be careful when adjusting rear toe. Rear trailing arm bracket to frame bolt torque is only ~18 ft-lbs. Mine were likely over torqued and snapped. Here's a thread on that fix... Backdraft - broken bolt on rear trailing arm bracket

fortpittclassic · #9 (**permalink**) 03-21-2023, 11:01 AM

If its possible, I would like to compare measurements to other cars. The tipoff to our car that something was wrong was this. Wheels off for ease of measuring, straight edge plumb above rotor to centerline, measure inward to body of strut. My car is .5" different between sides. This tells me that static camber built into the strut is different.

You should never ever seek a camber angle goal by adjusting coilover spring heights. My poor customers car was so long in the front, its been chewing the chin of the body up significantly. Altering side to side coilover heights and not zeroing the sway bar will cause other problems as well. This is just from experience. I'm confident our coilover adjustment, so doing that static measurement on the top of the rotor to the strut was my final clue something was wrong. I appreciate the replies!

fortpittclassic · #10 (**permalink**) 03-21-2023, 11:05 AM

Quote:

Originally Posted by strictlypersonl

If the angle of the strut relative to the axle centerline is consistent from side to side, the only fix is to modify the upper strut mount (or the lca inner pivot) somehow. 2 degrees change requires about 3/4" shift at the top or bottom.
*How is the strut connected to the upright? Any slots for adjustment?

Right, however my measurements were not the same. This is why I'd like to find out if other cars measure differently or not.