Suspension Question Wheel base difference from front to back on each side

[CBA]

Suspension question regarding wheel base / measurement from hub (front wheel) to hub (back wheel). My car was in a minor fender bender and the shop had to remove the right side suspension to do some repairs.

Shop did a nice job on the repairs and have verified the body is straight on key measures on the frame / bottom. I was there to visually inspect it the measurements of the body and it is in with 1/2 mm on 8 points of measurement. They corner balanced the car and did an alignment. The car tracks straight (hands off the wheel also) and drives wonderful.

After getting the car home and looking at it, it appeared the right front wheel sat a bit farther back in the wheel well than the left. I was able to measure the car hub to hub on each side of the car and based on doing these measurements it seems that the right side(where the damage was) is 1/2" to 3/4" shorter than the left side. In talking to the the shop they said bring it back and they will dive in. They also mentioned it's hard to have the front wheels perfectly straight and 1 degree off of the steering wheel not being centered can make a difference in my measurements. I'm running -1.5 degrees of camber and the car is set up for canyons and the track. I'm assuming that my rear trailing arms are not bent either. Front A(control) arms look fine and they did send the right front strut out and verified it was straight also. There is more info I could provide and the shop is working on it but ultimately I'm thinking when they put the suspension back something happened there.

My question is on the front suspension how much "play" or adjustment when bolting it up is there? Porsche tolerances are pretty tight but could there be a 1/4" or 1/2" that if the suspension is loosened up and moved around could eliminate my wheel base concerns?

Any help from people who know would be great. I know enough to be dangerous but not enough to know and the reason I'm asking the question.

Thank you!

[Evan Fullerton]

There isn’t much play at all in the front suspension. The front suspension crossmember has 0 play, and the front control arms are pushed up against that and tightened down at the front.

Caster can have a large effect on wheel position though and I have seen a few bent front control arms.

[CBA]

Thanks Evan…. Kinda of what I was thinking but just trying to keep sane as I was hopefully the was a little wiggle room. Control arms look fine up on the lift. Time for more measurements from the shop.

[dannobee]

Did they give you a printout of the alignment? If so, see what it shows for "set back." Also check the "thrust angle."

Measuring hub to hub wheelbase isn't very accurate, as the steering wheel has to be practically perfectly straight with toe equal on both sides and held there while measuring for the measurement to be meaningful. Scrub radius will show you that the wheel actually moves forward and backward when turning.

[CBA]

Originally Posted by dannobee

Did they give you a printout of the alignment? If so, see what it shows for "set back." Also check the "thrust angle."

Measuring hub to hub wheelbase isn't very accurate, as the steering wheel has to be practically perfectly straight with toe equal on both sides and held there while measuring for the measurement to be meaningful. Scrub radius will show you that the wheel actually moves forward and backward when turning.

Thank you. He is working on it today as we speak. Honestly I think they skipped the details and did not document it & went ahead and corner balanced it.

[dannobee]

Depending on which alignment machine the shop has, it's almost impossible to complete the alignment without printing out the results. The machine follows a prescribed work flow and the last step is printing out the results, with before and after readings.

Now, if they're not using a "real" alignment machine, all bets are off.

[Evan Fullerton]

Race teams primarily only use the string alignment method because you can’t haul the big fancy alignment machine out to the race track.

If the caster and camber are the same side to side and the strut tops are roughly in the same spot, you have a very square tub and suspension. If the caster is the same but the strut tops are in different spots in the strut towers, something is a little off.

I’ve raced cars with all manner of things bent and if the toe front and rear is right, it’s really hard to tell the difference from behind the wheel between a known bent car and one that isn’t.

[CBA]

Originally Posted by Evan Fullerton

Race teams primarily only use the string alignment method because you can’t haul the big fancy alignment machine out to the race track.

If the caster and camber are the same side to side and the strut tops are roughly in the same spot, you have a very square tub and suspension. If the caster is the same but the strut tops are in different spots in the strut towers, something is a little off.

I’ve raced cars with all manner of things bent and if the toe front and rear is right, it’s really hard to tell the difference from behind the wheel between a known bent car and one that isn’t.

Agreed with what your saying 100%. Thanks for your input it’s much appreciated. They do prefer to us string alignment for their work. The car handles great and at this point if the wheel base is off on both sides it’s more of “I know it’s off and it will bug me”. It’s a steel legal car which is used at the track and mountains”. Also the shop when they had car was apart and put it back together probably should have caught it if it’s really off. I’m assuming since they didn’t get back to me today something is off and they are trying to figure out what to do. I think it was a honest oversight and they should of have had better checks and balances when they reassembled it. They are a reputable shop that does service a lot of race cars too and high end cars.