Lower and alignment weight changes?
 

Going to do some suspension work on my '79 SC, including shocks, torsion bars, bushings, then lowering, alignment and corner balance. Currently I have the stock bumpers, but my future plans include replacing them with fiberglass. If I have the alignment and balance done with the stock bumpers, will the change to lighter fiberglass pieces later on require another alignment etc. due to the weight change? Can I do a simple (I assume minor) ride height adjustment later without requiring the complete re-alignment?

I removed all the stock exhaust, heat exchangers etc. and installed Bilstein HD fronts and Sport rears. The ride height increased by about an inch, so consequently I am concerned about the weight of bumpers having an effect on ride height.

Unfortunately, no, you need to re-corner balance due to the fact you will off set the corners by loosing weight, then align it. Sowwy.

Being aluminium the bumpers don't actually weigh that much.

The doors however are where there is a lot of weight. If you could loose some there instead...

Have you held a bumper blade? Although they are aluminum, they are certainly heavy. Replacing them with fiberglass and using a lighter form of bumper shock drops a good 70lbs from the car.

Removing the bumper shock mounts removes another 30+ lb.

As far as corner balancing goes, if the reduction in weight, front and rear separately, is close; your corner balance numbers won't be too far off. But your car will sit much higher which will also change your alignment. Lowering it back down will mess up your alignment and your corner balance.

+1 a re-alignment would be in order. DRACO A5OG is spot on. I've also included a DIY if you need a guide.

http://www.pelicanparts.com/techarticles/101_Projects_Porsche_911/60-Alignment/60-Alignment.htm

-Dmitry

I've had both my bumpers off at one time for repainting etc, and were surprised at how light they are. Mind you, my car is ROW and doesn't have the heavy US shock mounts and extra big rubber pads on the back. The doors however are crazy heavy, and mine don't even have the side protection bars that I believe US cars have.

Heh, I have the same dilemma. I need to do some suspension work, but I'm waffling about what to do with my tail/decklid/bumper, which means I'm waiting on the suspension work while I waffle about the body...

You can either wait until the body is sorted, or commit to doing ride height/alignment twice. I understand it's much easier the second time around.

I guess I thought if the height and alignment were set with the bumpers, then when I swapped to fiberglass and the ride height went up a bit, changing the alignment settings, I could simply lower it back down to the same height of the correct alignment settings. Then it would be the same for alignment (camber, toe, etc.) but perhaps a bit off corner balance.