Height Adjustment Issue - Advice? (long)
07-23-2006, 02:20 PM
#1
Rennlist Member
Thread Starter
Height Adjustment Issue - Advice? (long)
Having recently installed a set of Bilstein HD/H&R coil overs, I am getting a surprisingly low response to front height adjustment inputs.
The rears were set and left at 197mm from the top of the drop link bracket to the center of the shock mount eye - this gave a rear height of 120mm, or 25 1/8" to the inner rolled fender edge: this has not been further adjusted.
The front was installed at 96.5mm measured from the lower edge of the bottom locknut to the top edge of the mount bracket ring ( or 7 threads showing - old style) ..... this gave ~25" (+/- 1/16") side to side - and is where the confusion lies.
I attempted to raise the fronts 1/4" above the rear fender heights. It is widely stated that there is a 2:1 height increase for adjuster input: as the shock thread pitch is 1.5mm/turn, two turns should give 6mm ( ~1/4") increase - right?? The result of two turns was hardly noticeable after the car was driven and resettled.
OK - I continued this game: a total of 6 turns has been made, bringing the ring to locknut distance to 105.5mm - an adjustment of +9mm. By the books, this should have raised the front 2X, or 18mm ( 0.7"), which is far more than desired .....but, I haven't got even 1/10" increase, so am
I've done this many times on 928's with predictable results - so what is wrong here? The Bilsteins are the older version with the short threads - and at the moment, there are 13 threads showing below the locknut . The only bizarre idea that could explain this is that the weight of the car was resting on the shock bump stop: if this were the case, there would be little response to adjustment until the spring fully bore the chassis weight. Is that possible? - reading on the installation of M030 springs on these shocks, it seems that the adjusters cannot be set low enough - this is almost the reverse, for it appears that I may not have set these high enough. Before I turn in more adjustment, I may need a sanity check.
If you have H&R springs in, does any of this sound familiar?
The rears were set and left at 197mm from the top of the drop link bracket to the center of the shock mount eye - this gave a rear height of 120mm, or 25 1/8" to the inner rolled fender edge: this has not been further adjusted.
The front was installed at 96.5mm measured from the lower edge of the bottom locknut to the top edge of the mount bracket ring ( or 7 threads showing - old style) ..... this gave ~25" (+/- 1/16") side to side - and is where the confusion lies.
I attempted to raise the fronts 1/4" above the rear fender heights. It is widely stated that there is a 2:1 height increase for adjuster input: as the shock thread pitch is 1.5mm/turn, two turns should give 6mm ( ~1/4") increase - right?? The result of two turns was hardly noticeable after the car was driven and resettled.
OK - I continued this game: a total of 6 turns has been made, bringing the ring to locknut distance to 105.5mm - an adjustment of +9mm. By the books, this should have raised the front 2X, or 18mm ( 0.7"), which is far more than desired .....but, I haven't got even 1/10" increase, so am
I've done this many times on 928's with predictable results - so what is wrong here? The Bilsteins are the older version with the short threads - and at the moment, there are 13 threads showing below the locknut . The only bizarre idea that could explain this is that the weight of the car was resting on the shock bump stop: if this were the case, there would be little response to adjustment until the spring fully bore the chassis weight. Is that possible? - reading on the installation of M030 springs on these shocks, it seems that the adjusters cannot be set low enough - this is almost the reverse, for it appears that I may not have set these high enough. Before I turn in more adjustment, I may need a sanity check.
If you have H&R springs in, does any of this sound familiar?
07-23-2006, 03:24 PM
#2
The rears are a 2:1 ratio while the fronts are nearly 1:1. On mine (same set-up as your's), the front perch is nearly to the top of the shock threads to achieve a front ride height of 135mm. The rear is set at 115mm, or 5mm below your's, so I would think you'd want a front ride height on your's of ~140mm, which would probably be at the absolute max height on the front shock threads.
07-23-2006, 07:47 PM
#3
Rennlist Member
Thread Starter
Jimbo,
Thanks for the input
: As I did not achieve even a 1:1 return for the adjustment made, it does appear that the spring is not yet adequately compressed to fully bear the chassis weight. This suggests that the shock bump stop is active vs passive in this role .... so I will further crank up the adjusters until there is at least a 1:1 response - and I get my +1/4" over the rear height ( 120mm rear to 140mm front)
With the H&R's, there's certainly no worry about the shock not being threaded low enough - but it does imply that setting too low may be an issue in that the shock piston may not have sufficient travel on compression.
Thanks for the input
: As I did not achieve even a 1:1 return for the adjustment made, it does appear that the spring is not yet adequately compressed to fully bear the chassis weight. This suggests that the shock bump stop is active vs passive in this role .... so I will further crank up the adjusters until there is at least a 1:1 response - and I get my +1/4" over the rear height ( 120mm rear to 140mm front)With the H&R's, there's certainly no worry about the shock not being threaded low enough - but it does imply that setting too low may be an issue in that the shock piston may not have sufficient travel on compression.
07-23-2006, 07:56 PM
#4
Seared
Rennlist Member
Rennlist Member
Garth,
Not sure if this helps, but the picture shows the final resting point of my front shock collars following alignment and height tweaking - I have M030 & Bilstein HD.
My rear fender height is right at 25.5" when sighting to the inner lip of the fender, and the front openings are just under .25" higher.
All of my coils have play when the suspension is unweighted. In the rear, I fastened the tops of the coils to the spring mounts, as I felt it important that the coils stay properly seated in the rubber mounts.
Andreas
Not sure if this helps, but the picture shows the final resting point of my front shock collars following alignment and height tweaking - I have M030 & Bilstein HD.
My rear fender height is right at 25.5" when sighting to the inner lip of the fender, and the front openings are just under .25" higher.
All of my coils have play when the suspension is unweighted. In the rear, I fastened the tops of the coils to the spring mounts, as I felt it important that the coils stay properly seated in the rubber mounts.
Andreas
07-23-2006, 08:18 PM
#5
Rennlist Member
Thread Starter
Andreas,
That makes for an interesting comparison between the ROW M030 and H&R springs on the same shocks.
In the rear, the H&R remain in firm contact with both spring perches, even prior to installation - this is apparently not the case with the ROW springs.
Conversely, in the front, you have achieved ~ 25 3/4" height with 93.5mm adjuster spacing on the shock .... and I have a mere 25" with a spacing of 105.5mm measured as per your pic.
I will further adjust upwards - to the top of the threads if necessary ( as Jimbo suggests). to achieve the desired rake (+1/4" over the rears)
Overall, it appears that the H&R's are designed to be lower than the ROW M030's.
That makes for an interesting comparison between the ROW M030 and H&R springs on the same shocks.
In the rear, the H&R remain in firm contact with both spring perches, even prior to installation - this is apparently not the case with the ROW springs.
Conversely, in the front, you have achieved ~ 25 3/4" height with 93.5mm adjuster spacing on the shock .... and I have a mere 25" with a spacing of 105.5mm measured as per your pic.
I will further adjust upwards - to the top of the threads if necessary ( as Jimbo suggests). to achieve the desired rake (+1/4" over the rears)
Overall, it appears that the H&R's are designed to be lower than the ROW M030's.
07-24-2006, 08:44 AM
#7
The H&R's are substantially shorter than the M030, by 1.25" or so. I did not need to wire the spring to the perch as there was slight compression before installing the assembled shock/spring into the car.