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Join Date: Nov 2007
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86' 911 Rear suspension? angle readings?

Yup yet another 911 rear suspension set up question.
Here is the he brain burner question I have. After setting up the the spring plates at the same angle (using a very accurate angle gauge and door sills dead nuts level) i get the same reading on both sides of 3X degrees. however the ride height is different on the two sides from the wheel well.
25" driver
25-1/2 pass
Is it an unreasonable expectation to have the spring plates at the same angle yet get different angle readings? Yes the small ride height adjustment available on both plates has been left alone and set neutral. these are new bars so I'm wondering if sometimes they have slightly different torsional resistance from one to the next or the stock shocks play a role.
Lastly you can physically see the difference in angle by the plates relation to the cover bolt. the pass side which rides high is set at a shallower angle then the driver side and yet still rides higher? seems strange to me. I would think they should be the same or if anything the driver side would be set higher to compensate for the driver.

Thanks: Ian S

Old 04-29-2015, 03:56 PM
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Can you clarify something for me Ian?

Is this correct?
When you set up the spring plates at the same angle the car was up in the air wheels off

Later you put the wheels on and drop the car to the ground and wonder why the ride height differs from one side to the other

If that is the case then one easy explanation (there are a number) is that the car's weight is not evenly distributed and one side is compressing the suspension more than the other

It doesn't sound like you have a problem to me. You just need to adjust the suspension accordingly and might like to consider getting the car corner-weighted.

If my understanding of you issue is way out then apologies as I have clearly not understood your post...

Best of luck, Neil
Old 04-29-2015, 04:16 PM
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Cars are also handbuilt and old. This may cause variation. If you get the car corner ballanced they will adjust the height too.
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Old 04-29-2015, 04:26 PM
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The wheelwells are, more often than not, uneven. People often use them as a reference for ride height, but that is not the correct thing to do.

Though I'm not sure I entirely understand what you are trying to say, uneven front suspension could be causing one side of the rear to load up more than the other. Have the corner weights measured when you do your alignment, and you'll quickly see what the problem is.
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Old 04-29-2015, 04:57 PM
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Thanks for the responses guys! I do have everything removed from the plates when adjusting.
I then then reassemble, set the car on the ground, short drive and check height. In an attempt to clarify I guess it just seemed strange that I would have such a variation side to side on spring plate position / angle to achieve an equal ride height. I would think the spring plates would be in the same positions. I never considered different wheel arch heights. Car is on a level concrete pad in my shop. I also considered something maladjusted in the front subtracting / adding load to the rear, however I have never touched the front susp. all factory original. Euro car wpozzzz.
Old 04-29-2015, 05:54 PM
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Balance, then the geometry is even, side to side

As others have posted, the front affects the rear heights, angles, and vice versa.

Our cars are built my men, (and perhaps women), so there is some variance in the body panels and using them for a final reference may not be as accurate as measuring the height from a flat-level surface to the suspension pivot points, which is where we need to be to make the car suspension have the same kinetic movement side to side.
Additionally, we need the weight on each front wheel equal and the rear very close to the same, side to side.

Then the car will behave the same in right and left hand turns and will be able to generate the maximum braking force - This is not a small thing if you are trying to put together a competitive car, (or, trying to make it as good as you can make it).

Getting the car as good as you can make it is a mechanical and intellectual exercise.

Putting it on the track and being fluid with the transitions and line is probably one of the greatest challenges for a car guy.

After you have done the front and rear, it takes a set of scales to get the corner weights right, the ride height equal front and rear, and someone who cares to get the alignment numbers set right.

Be a good idea to talk to some of your friends to get their recommendations for alignment specs and heights. That would not be me, I am still working on getting the parts right.

Good luck and have fun,
chris

Old 04-29-2015, 06:58 PM
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