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larchie
Joined: 19 Jun 2003
Posts: 297
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 Posted: Mon Apr 14, 2014 5:03 am Post subject: 924 Attitude Adjustment |
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At a garage sale, I ran across some 20-year old Excellence magazines and was surprised to read that the attitude of the rear of the chassis of the 924 was altered on delivery (presumably, on delivery to the US):
| Jim Pasha wrote: | One thing that will make the brakes wear and work better is to adjust a 924 to a level attitude. The cars were delivered with the rear bumper raised for meeting federal bumper height requirements. This upsets the weight balance under dynamic loading, braking in this instance, and causes more weight transfer to the front wheels than is optional. On the 1978 and later cars with the 36mm adjustment nut, it is a one hour job to lower the rear and set the ride height. I would do this either with or just prior to an alignment session. To adjust the early 924, 1976-77, requires the torsion bars be removed and the trailing blades reset. The Porsche technical specification has the blade angle in the list of information. This applies to all 924/944 models so affected, irrespective of brakes and rear suspension.
(Jim Pasha, "924 Brakes, Struts and More," Excellence (November, 1995) 107) |
Before re-setting the ride height, I wonder if those members who race can comment about difference in aerodynamic drag between the two different ride heights. Presumably, there would be less aerodynamic drag with the re-adjustment Pasha recommends.
Having had very little experience with suspension, I have two questions:
(1) The aerodynamic issue: For those 924s without spoilers, would lowering the rear of the car as Pasha suggests decrease the downforce and so reduce traction?
(2) The safety issue: would the US federal bumper requirement apply to all cars on the road today or just to cars sold by dealers? That is, would the angle change make a significance difference by increasing the probability of a bumper-overide rear-end collusion? |
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kcoyle
Joined: 15 Jan 2011
Posts: 712
Location: Long Island, NY
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| Posted: Mon Apr 14, 2014 6:38 am Post subject: |
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No clue on either but I was just thinking how much the "rake" makes me nuts to look at. I know it's only about an inch but still.....
_________________
1982 931- Stock with MBC at 8psi
Relax, all right? My old man is a television repairman, he's got this ultimate set of tools. I can fix it. |
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jason c
Joined: 13 Jan 2014
Posts: 1018
Location: Nwi
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| Posted: Mon Apr 14, 2014 7:34 am Post subject: |
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| I doubt any change in down force would be noticeable. The rear spoiler was meant to reduce lift not create down force, adding it would help straight line stability more than the ride height change will effect. It would be a better handling car overall with the rear lower. The bumper override issue depends on how much you're going to lower it. In today's SUV packed world, I doubt it would make much difference. The bumpers are meant for a low speed impact any more and you're looking at a total loss bumper override or not. The ride height regulation was made for safety reasons (bumper override), I doubt that all the vehicles built today meet the old requirements. |
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