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Set ride height within pss9 permissible range?

 
Old 09-25-2011, 12:33 AM
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plymouthcolt
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Default Set ride height within pss9 permissible range?

My ride height is currently set too low for the street. I find I am always hitting the bump stops. I need to raise the car and also set the correct range for the pss9. Apparently setting the pss9 too low will evenutally lead to damaged shocks.

I read the post from PBenz (Paul) and I think I have a good idea of setting the height. Where I'm confused is setting that height within the allowable range of the pss9 shocks.

For the fronts
permissible adjustment range
maximum permissible axle load 760 kg ( 1672 lb) 120 – 140 mm* = 20 mm range
* measurement:
top edge of spring seat down to the center of top mounting screw of axle bracket

The rears
permissible adjustment range
maximum permissible axle load 1150 kg ( 2530 lb) 195 - 210 mm* = 15 mm range
* measurement:
top edge of spring seat down to the center of bottom mount

What I'm looking for is input and corrections before I start the job so I don't wind up with a car that crabwalks down the road.

I would like to set the height to RoW sport using the Porsche recommended measuring points: (thank you to PBenz Paul)

RoW Sport
Front: 144 +/- 10
Max left-to-right difference: 5

Rear: 127 +/- 10
Max left-to-right difference: 5

Max front to rear difference: 10

-So lets say I want to set front height to 144mm measuring from the bolt to ground. I'll take a measurement and it happens to show-for example 134mm.

-Now I measure the front shock from "top edge of spring seat down to the center of top mounting screw of axle bracket ". I marked in red what I think are the proper measuring points-but I'm not sure. Am I correct?

-Whatever reading I get I'll turn the collars and keep measuring until I increase it by 10mm. As long as my permissible is between 120 – 140 mm I'm good? Yes?

Any feedback is very much appreciated.

Last edited by plymouthcolt; 04-21-2013 at 11:26 AM.
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Old 09-27-2011, 05:25 AM
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Macca
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Hi Howard. You have put some effort into this post and you deserve an answer.

Im hoping by asking this question I can get you a bump.

Can you tell me what your current measurements from those points you have pictured are that are causing the issues? I ask as I have just installed PSS10 and Im evaluating my settings....?

Thanks in advance.
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Old 09-28-2011, 12:13 PM
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when I was trying to get my pss10's to the correct ride height I called the bilstein tech support line. I was told the permissible range on the instruction page didn't matter, the product is made for full use of the threads, all the way up or all the way down.
they didn't mention damaging the shocks at lower settings.
maybe give them a call and get a different answer...
howard, how did you know you were hitting bump stops on the shocks?
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Old 09-28-2011, 08:09 PM
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Originally Posted by k722070 View Post
when I was trying to get my pss10's to the correct ride height I called the bilstein tech support line. I was told the permissible range on the instruction page didn't matter, the product is made for full use of the threads, all the way up or all the way down.
they didn't mention damaging the shocks at lower settings.
maybe give them a call and get a different answer...
howard, how did you know you were hitting bump stops on the shocks?
When I encountered uneven pavement (road meets bridge), or drive over a sunken manhole, it felt like I was driving on flat front tires. The shock that transmitted to the chassis was so strong I have stopped driving the car until I am able to raise it. I was always scanning the road for imperfections and gritting my teeth waiting for the impending thud.
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Old 09-28-2011, 08:18 PM
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What was your ride height?

I haven't heard of anyone having a shock bottom out even with a ride height in the mid-RS range.
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Old 09-28-2011, 08:24 PM
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Originally Posted by Macca View Post
Hi Howard. You have put some effort into this post and you deserve an answer.

Im hoping by asking this question I can get you a bump.

Can you tell me what your current measurements from those points you have pictured are that are causing the issues? I ask as I have just installed PSS10 and Im evaluating my settings....?

Thanks in advance.
It was too dark for me to measure the rear height, but I measured the front from the top of the bolt head to the ground and it is 103mm.
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Old 09-28-2011, 10:39 PM
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103 is very very low.

when I first installed the pss10's I set the collars to the lowest setting per instructions(as above, 120 and 195) and it came out pretty good. I can't remember the exact ride height, but it was a good starting place. I want to say it came out to just above rs ride height(124mm front) because I had to switch to rs rear drop links to get to the correct rs ride height.

I had also asked tech support about a correlation between moving collars and ride height, they said too many variables to give an answer.
but 5mm of collar change seems to be pretty close to 5mm of ride height change as far as my experiments have gone.
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Old 09-28-2011, 11:06 PM
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Originally Posted by plymouthcolt View Post
It was too dark for me to measure the rear height, but I measured the front from the top of the bolt head to the ground and it is 103mm.
Yikes!! That's a 1/2" below the lowest limits of RS (124mm +/- 10mm) and very dangerously low. I'd imagine that there are a whole lot more problems going on than just hitting the bump stops.

Going to 144 may be a little too extreme the other way, though, especially if you like the handling and appearance of a nicely lowered 993. Consider RS +10 range and you won't get into any trouble with rear drop links, bump steer or alignment issues.
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Old 09-29-2011, 12:47 AM
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Thank you everyone for your replies (especially jimbo3 and k722070). I plan on doing the adjustment this weekend and will report in on my results.

One other questions was in regards to: Max front to rear difference: 10

Since RS height is F124 and R107, how does this 10mm difference come into play?
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Old 09-29-2011, 09:41 AM
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Originally Posted by plymouthcolt View Post
One other questions was in regards to: Max front to rear difference: 10

Since RS height is F124 and R107, how does this 10mm difference come into play?
Porsche took under consideration several points, of which the fact that their rear suspensions were not adjustable, M030 or not, but slightly.
So the rear height with new suspension would not fall exactly @ 127mm or whatever figure.
So the Front Rear 10mm is the delta not to be over-passed. (or -3mm to +37mm tangibly or 17mm being zero tolerance)
i.e for M030 ROW
if Front is 144mm
and Rear is 127mm ,
you should not exceed higher than 154mm Front if Rear is 117mm. max positive tolerance vs max neg tolerance
Take the figures as medians.
I had 122mm @ the back with new M030 so I adjusted to 139 @ Front
so my delta was zero when I did the geo
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Old 09-29-2011, 10:17 AM
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Originally Posted by plymouthcolt View Post
Thank you everyone for your replies (especially jimbo3 and k722070). I plan on doing the adjustment this weekend and will report in on my results.

One other questions was in regards to: Max front to rear difference: 10

Since RS height is F124 and R107, how does this 10mm difference come into play?
If the front is, say, 120mm (which is RS -4mm), the rear should be 103mm (which is also RS -4mm) +/- 10mm. This is to keep the proper "rake", to avoid a nose up or down situation.

Actually, you'd want it much closer than that. I would try to end up within 2 to 4 mm, front to back. Try to get left-to-right and front-to-rear as close as possible to your target height before taking it in for a corner balance and alignment. For example, if your target height is RS +5, get both sides of the front to 129 plus or minus 1 or 2 mm side to side, and get both sides of the rear to 112, plus or minus 1 or 2 mm side to side.

I think you'll find that most here like to have their car somewhere between RS +5 and RS +15, depending on road conditions.

I've typed a lot of words to basically say that you can't have your front end at, say, RS -5 and the back end at higher than RS +5 or lower than RS -15. Both ends should be evenly raised or lowered.

Side note- Yes, "RS +15" is actually ROW Sport -5. Didn't want to confuse the issue with flipping back and forth between the terms "RS" and "ROW Sport".

Last edited by jimbo3; 09-29-2011 at 10:33 AM.
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Old 09-29-2011, 10:44 AM
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Originally Posted by jimbo3 View Post

I've typed a lot of words to basically say that you can't have your front end at, say, RS -5 and the back end at higher than RS +5 or lower than RS -15. Both ends should be evenly raised or lowered.
to debate
I do not agree, if my ride height at rear is RS -10 neg , I can rise my front @ RS +10 pos, and still be in tolerance.
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Old 09-29-2011, 11:14 AM
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geolab-wouldn't that mess up the much discussed 1 degree down rake?

jimbo3-I had assumed getting a corner balance would include setting the correct ride height? couldn't you just tell the shop doing the corner balance to set the ride height to X and leave it in their hands?
there seems to be only one shop out here able to do a corner balance and they've been booked all season.

howard-when trying to set the ride height as exact as jimbo3 writes, keep in mind the slope of your garage floor and that the suspension will settle some. I have to adjust, drive some miles to a flat spot, measure, adjust, measure, let the suspension settle, measure, and on and on before I take it in for an alignment.
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Old 09-29-2011, 01:02 PM
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Originally Posted by k722070 View Post
geolab-wouldn't that mess up the much discussed 1 degree down rake?
2272mm between wheels with a -1* degree slope, the sine of this angle would be 40mm in the front wheel center. This is why max negative tolerance rear vs. maximum positive tolerance front is limited to 40mm (-3mm to +37mm) in extremes. So that rake would be equal to zero in extremes or less than zero (at stand-still).
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Old 09-29-2011, 03:43 PM
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Originally Posted by k722070 View Post
couldn't you just tell the shop doing the corner balance to set the ride height to X and leave it in their hands?

.
Yes, you certainly could. I chose to take that the step of setting the initial ride height with specific directions to only adjust for corner balance. That gave me a chance to look at the ride height to see if I liked it, plus I didn't want to show up to a surprise after the work was done.
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