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Rear subframe alignment
http://gt4dc.co.uk/forum/viewtopic.php?f=2&t=5828
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Author:  Sirius [ Fri Jul 27, 2012 7:37 pm ]
Post subject:  Rear subframe alignment

Question for Gary really, but if anyone else has input please feel free.

I'm putting the rear subframe back in the car in the next few days, I know the alignment is important, how did you measure to establish the centre line?

Author:  two_OH_five [ Fri Jul 27, 2012 9:22 pm ]
Post subject: 

with a tape measure

I measured from outside edges of the rear arm back mounting flange to find the centre of the rear beam and mark (correlate by eye and or by measurement on the diff mount too)
Use the chassis rails to put that mark in the middle of the car. IIRC you can also use the upper subframe bushes on the chassis rails to locate the rear too

For the front I measured off the inner trailing arm mount flange to each of the actual "turrets" where the front bolts go. Quite possibly double checked this off the trailing edges of the sideskirts for sanity too

Finally a diagonal measure off the rear trailing arm mounts on the chassis to the rear suspension arm mounts as you would when laying out a building plot

In actuality getting it 100% square isn't critical as the final string/4 wheel alignment will ensure a 0 thrust angle which is what really matters.
It's a good idea to try and get at least the rear close though as it will monkey with the rear camber unless you fit adjustable rear top mounts

As you re-assemble check other visual clues like propshaft in tunnel etc
Finally when rebuilt check the camber both sides with the toe adjusters set the same each side. If it's wildly out the subframe probably isn't centered

Author:  Sirius [ Sat Jul 28, 2012 1:25 am ]
Post subject: 

Thanks Steve,

That's really helpful :)

Author:  DeeCee [ Sat Jul 28, 2012 7:55 am ]
Post subject: 

I used a piece of string from centre firewall to centre plint to align my prop shaft and rear subframe.

As Steve said, it is near impossible to get it perfectly square, so you just have to do the best you can and get a wheel alignment later.

Author:  two_OH_five [ Sat Jul 28, 2012 10:51 pm ]
Post subject: 

Other things from today's session

There's a drain in the subframewhich looks plumb center

The rear "turrets" do mount in a kind of cup on the chassis rails

And off topic, the reason the 205 has a spongy brake pedal is flex in the brake booster

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