PSS-9, Corner weight OR Ride height?
07-01-2002, 10:31 AM
#1
Instructor
Thread Starter
Join Date: Jun 2001
Location: UK
Posts: 234
Likes: 0
Received 0 Likes
on
0 Posts
PSS-9, Corner weight OR Ride height?
I expect to purchase the Bilstein PSS-9 suspension kit for my '95 Carrera soon, and have read most of the archive posts and advice on the subject of fitting and set-up.
However, I'm unsure on whether to set the system up using the ride height method OR by corner weighting. As I understand you cannot do both, but that they are in fact closely related.
I intend to use RS alignment settings and initially set it to RS ride heights. I'll then drive a few miles to let everything settle/bed down before finalizing the set-up.
I believe that race car teams swear by corner weighting as the ONLY way to set-up the suspension, but I've read that our cars (all 911's) are very sensitive to ride height! Are the people that write this about 911's really refering to corner weighting but using the ride height terminology for the "lay-man"?
I've also been told that if you use corner weighting you can end up with the car not looking quite right as you can get varying tyre (tire) to wheel arch clearances on either side.
If I do it by setting the ride height I'll have the car corner balanced anyway, so presumably I'm getting some way to proper corner weighting anyway.
Any thoughts or experience would be apprieciated.
However, I'm unsure on whether to set the system up using the ride height method OR by corner weighting. As I understand you cannot do both, but that they are in fact closely related.
I intend to use RS alignment settings and initially set it to RS ride heights. I'll then drive a few miles to let everything settle/bed down before finalizing the set-up.
I believe that race car teams swear by corner weighting as the ONLY way to set-up the suspension, but I've read that our cars (all 911's) are very sensitive to ride height! Are the people that write this about 911's really refering to corner weighting but using the ride height terminology for the "lay-man"?
I've also been told that if you use corner weighting you can end up with the car not looking quite right as you can get varying tyre (tire) to wheel arch clearances on either side.
If I do it by setting the ride height I'll have the car corner balanced anyway, so presumably I'm getting some way to proper corner weighting anyway.
Any thoughts or experience would be apprieciated.
07-01-2002, 12:16 PM
#2
Depends on what you want, a car that looks right or a car that drives right. If you want looks, go for corner height. It you want a car that drives right, go for corner weight.
My recommendation? Have the car corner balanced.
My recommendation? Have the car corner balanced.
07-01-2002, 02:19 PM
#3
Addict
Rennlist Lifetime Member
Rennlist Lifetime Member
Mark,
Perhaps I'm wrong but you may be able to get both objectives or at least very close. As you can see from my post after I had my car done (<a href="http://forums.rennlist.com/forums/ultimatebb.php?ubb=get_topic&f=3&t=002211" target="_blank">Rick's PSS9 after-install posting</a>) my corner weighting is very close to being even. I've also measured and from side to side, I have less than 1/4" difference which one could easily write off to slight tire pressure differences. It's obviously very close.
Best of luck to you.
Rick.
Here's a more recent picture after putting on an RS Aerokit & 18" RS Wheels:
Perhaps I'm wrong but you may be able to get both objectives or at least very close. As you can see from my post after I had my car done (<a href="http://forums.rennlist.com/forums/ultimatebb.php?ubb=get_topic&f=3&t=002211" target="_blank">Rick's PSS9 after-install posting</a>) my corner weighting is very close to being even. I've also measured and from side to side, I have less than 1/4" difference which one could easily write off to slight tire pressure differences. It's obviously very close.
Best of luck to you.
Rick.
Here's a more recent picture after putting on an RS Aerokit & 18" RS Wheels:
07-01-2002, 03:47 PM
#4
RL Technical Advisor
Hi Mark:
To get the best handling from your planned PSS-9 upgrade, you should have the car corner-weighted at the correct ride height and rake.
In short, you must do both. Competent and experienced personnel will have no trouble setting the corner-weights and diagonals at the ride height you wish as well as ensuring that the car is 1 deg nose-down.
This is SOP for these cars equipped with coil-overs regardless whether its a street car or race car.
After that, a good alignment will finish the job.
To get the best handling from your planned PSS-9 upgrade, you should have the car corner-weighted at the correct ride height and rake.
In short, you must do both. Competent and experienced personnel will have no trouble setting the corner-weights and diagonals at the ride height you wish as well as ensuring that the car is 1 deg nose-down.
This is SOP for these cars equipped with coil-overs regardless whether its a street car or race car.
After that, a good alignment will finish the job.
07-01-2002, 03:58 PM
#5
Addict
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Mark,
Listen to Steve. My mechanic and I did my corner balance and alignment and we weren't able to get the correct amount of rake in the car because I was running too large of rubber up front. We did some testing and used a smaller tire and lowered the car 20+mm and the car was much better and faster. Front end grip was the same due to the better weight distribution but other aspects of the handling improved. I underestimated the importance of the degree of rake.
If I am not mistaken my ride height side to side is very close (within a few mm). Measuring from the fender to the ground is not the correct way to measure ride height either.
Greg
Listen to Steve. My mechanic and I did my corner balance and alignment and we weren't able to get the correct amount of rake in the car because I was running too large of rubber up front. We did some testing and used a smaller tire and lowered the car 20+mm and the car was much better and faster. Front end grip was the same due to the better weight distribution but other aspects of the handling improved. I underestimated the importance of the degree of rake.
If I am not mistaken my ride height side to side is very close (within a few mm). Measuring from the fender to the ground is not the correct way to measure ride height either.
Greg
07-01-2002, 05:21 PM
#6
Pro
Join Date: Jan 2002
Location: Manhattan Beach, CA
Posts: 653
Likes: 0
Received 0 Likes
on
0 Posts
A question for the experts regarding rake...After having the PSS-9's installed, ride height and cornerbalancing by the mechanic and alignment shop, the rake ended being about 1/3rd of an inch lower in the front. Note that we did measure using the fenders. Is this much rake concidered to be the norm or "acceptable"?
The car handles increadibly both on and off of the track, but I have little to compare to as it had shocks with 50k miles on them prior to the PSS-9's.
The car handles increadibly both on and off of the track, but I have little to compare to as it had shocks with 50k miles on them prior to the PSS-9's.
Trending Topics
07-02-2002, 11:54 AM
#8
Addict
Lifetime Rennlist
Member
Lifetime Rennlist
Member
[quote]Originally posted by George A:
<strong>Ok guys,
How do you measure rake?
George</strong><hr></blockquote>
George,
We used a Dunlop Camber gauge. It measures horizontal (camber) and vertical (rake).
We did the alignment the old fashion way (no laser alignment racks). A real alignment rack may measure the rake.
Greg
<strong>Ok guys,
How do you measure rake?
George</strong><hr></blockquote>
George,
We used a Dunlop Camber gauge. It measures horizontal (camber) and vertical (rake).
We did the alignment the old fashion way (no laser alignment racks). A real alignment rack may measure the rake.
Greg
07-02-2002, 01:39 PM
#9
Instructor
Join Date: Jun 2001
Location: South Carolina
Posts: 144
Likes: 0
Received 0 Likes
on
0 Posts
Greg, wouldn't the rake that the Camber Gauge gives you be the wheel caster and not the rear to front rake of the car.
Does anyone know how much difference you need in the Shop Manual heights (front to rear) to get a 1 degree rake?
Does anyone know how much difference you need in the Shop Manual heights (front to rear) to get a 1 degree rake?
07-02-2002, 01:48 PM
#10
RL Technical Advisor
[quote]Originally posted by David '96 993:
<strong>A question for the experts regarding rake...After having the PSS-9's installed, ride height and cornerbalancing by the mechanic and alignment shop, the rake ended being about 1/3rd of an inch lower in the front. Note that we did measure using the fenders. Is this much rake concidered to be the norm or "acceptable"?
</strong><hr></blockquote>
Hi David:
I measure the car's rake on the alignment rack by placing a protractor in the door sills and reading that number. As long as you are on a perfectly level surface or know exactly how far off level your surface is, that works just fine. Shoot for 1 to 1.5 degrees nose-down.
Some folks measure the ride height at the suspension pickups and then do the math, but I've done this both ways and found my method easier and more repeatable (accurate) for me.
<strong>A question for the experts regarding rake...After having the PSS-9's installed, ride height and cornerbalancing by the mechanic and alignment shop, the rake ended being about 1/3rd of an inch lower in the front. Note that we did measure using the fenders. Is this much rake concidered to be the norm or "acceptable"?
</strong><hr></blockquote>
Hi David:
I measure the car's rake on the alignment rack by placing a protractor in the door sills and reading that number. As long as you are on a perfectly level surface or know exactly how far off level your surface is, that works just fine. Shoot for 1 to 1.5 degrees nose-down.
Some folks measure the ride height at the suspension pickups and then do the math, but I've done this both ways and found my method easier and more repeatable (accurate) for me.
07-02-2002, 02:04 PM
#11
Addict
Lifetime Rennlist
Member
Lifetime Rennlist
Member
[quote]Originally posted by Buck:
<strong>Greg, wouldn't the rake that the Camber Gauge gives you be the wheel caster and not the rear to front rake of the car.
Does anyone know how much difference you need in the Shop Manual heights (front to rear) to get a 1 degree rake?</strong><hr></blockquote>
My fault I didn't explain it well. We used the Camber guage on the door sill and measure the amount of rake. Just like what Steve said.
This guage my mechanic has is unlike the camber gauge that you see for sale through smart racing products. It has a flat face and can measure horizonatal or vertical.
Does that make more sense now?
Greg
<strong>Greg, wouldn't the rake that the Camber Gauge gives you be the wheel caster and not the rear to front rake of the car.
Does anyone know how much difference you need in the Shop Manual heights (front to rear) to get a 1 degree rake?</strong><hr></blockquote>
My fault I didn't explain it well. We used the Camber guage on the door sill and measure the amount of rake. Just like what Steve said.
This guage my mechanic has is unlike the camber gauge that you see for sale through smart racing products. It has a flat face and can measure horizonatal or vertical.
Does that make more sense now?
Greg
07-04-2002, 08:30 AM
#12
Instructor
Thread Starter
Join Date: Jun 2001
Location: UK
Posts: 234
Likes: 0
Received 0 Likes
on
0 Posts
Thanks chaps terrific advice as usual. (I've been away for a few days so only just read it all).
Steve/Greg, at the risk of going over old ground can you point me to definative or at least target corner weights to aim for.
I've got all the alignment info from p-car.com (thanks Robin) but no corner weights.
The car is a "vanilla" '95 Carrera (2) non varioram with AC and electric sunroof & seats to weigh it down!
Steve/Greg, at the risk of going over old ground can you point me to definative or at least target corner weights to aim for.
I've got all the alignment info from p-car.com (thanks Robin) but no corner weights.
The car is a "vanilla" '95 Carrera (2) non varioram with AC and electric sunroof & seats to weigh it down!
07-04-2002, 07:18 PM
#13
RL Technical Advisor
Hi Mark:
Since corner weighting is always done with your body in the driver's seat, I'd need your weight to knwo what the target weights should be.
Since corner weighting is always done with your body in the driver's seat, I'd need your weight to knwo what the target weights should be.
07-05-2002, 06:12 AM
#14
Instructor
Thread Starter
Join Date: Jun 2001
Location: UK
Posts: 234
Likes: 0
Received 0 Likes
on
0 Posts
Steve,
I'm 170lbs butt naked! Lets allow 10lbs for clothing helmet etc.
Assume a full fuel tank but spare/tools etc removed for this excercise as this is what I would normally do for a DE day or track day as we refer to them.
Forgot to mention it's a LHD car despite me being in the UK.
I understand that the LHD cars have a more favourable L/R weight distribution?
I'm 170lbs butt naked! Lets allow 10lbs for clothing helmet etc.
Assume a full fuel tank but spare/tools etc removed for this excercise as this is what I would normally do for a DE day or track day as we refer to them.
Forgot to mention it's a LHD car despite me being in the UK.
I understand that the LHD cars have a more favourable L/R weight distribution?
07-05-2002, 10:15 AM
#15
Mark,
I posted a response on the ukegham meet thread, too.
yes, I'm interested in a combined/group buy.
FYI the price from Gert comes out as cheap as ( or even less) than that from ECP.
Also, the dunlop guage that Greg mentioned is the same one I bought recently
See what Gert can do for two kits.
I'm in France next Wednesday, so could possibly meet him & pick them up if necessary (assuming he has some, and I can get them in the back of my car !)
Cheers,
John.
I posted a response on the ukegham meet thread, too.
yes, I'm interested in a combined/group buy.
FYI the price from Gert comes out as cheap as ( or even less) than that from ECP.
Also, the dunlop guage that Greg mentioned is the same one I bought recently
See what Gert can do for two kits.
I'm in France next Wednesday, so could possibly meet him & pick them up if necessary (assuming he has some, and I can get them in the back of my car !)
Cheers,
John.
