Personally, I wouldn't go off the numbers on the damper adjusters, I would go off the number of clicks as being the "range of adjustment", where full hard is the valve when closed. Tertius mentioned this in his posting above. Am I right to presume that the left and right dampers have the same number of "clicks" between full hard to full soft?
kW v3 coilovers
- Thread starter veilside85
- Start date
pHilli0 said:
Mine have done it a couple of times on country roads and they are 11/16 rebound, and 10/12 bump (front), 9/12 (rear). It sounds a lot worse that it is because the top of the strut is right behind your seat. For me, there is no kickback from the corner that "pops", and the cause is small, sharp bumps in the road, not heavy compression of the whole rear axle (e.g. due to hitting a dip in the road at speed, Nurburgring-stylee). I'm not sure that this kind of thing can be avoided, even if you crank up the bump, and I don't think any damage is being done.
So I'm inclined to leave things be, because the ride is great and I love that feeling of the car loading up in the corners, which you only get (at sensible speeds) with softer settings.
MrPT said:
Thanks for that advice. I have once again tweaked the rear and I believe I have improved things. I have turned up the bump 4 clicks and reduced the rebound by 2. The rear now feels better along country lanes. It knocked only once but seemed lighter than before.
Just so I get things right in my mind I imagine the bump or compression rate to be how much pressure has to be applied to the shock to get it to move. So a higher rate means a stiffer ride. The rebound rate is how much travel occurs once the shock has reached its highest point? What I am not sure is if I move the rebound wheel all the way to zero and click it plus 4 times is that giving me a little rebound or a lot? God I think I might be stupid. haha
So what are your actual settings now for bump and rebound at F&R?
This guy gives a good explanation of the reason why soft suspension is better on bad/bumpy roads: https://www.youtube.com/watch?v=hGZRairqHNI and how coilovers work: https://www.youtube.com/watch?v=xmr14nCivZA
The springs essentially support the weight of the car at each corner and the dampers are essentially there to control the rate of compression (bump) and extension (rebound) and to prevent the spring from oscillating (boinging). The damper is essentially a piston with holes in it so that when force is applied under compression, the damper can shorten in length whilst the spring is being compressed and lengthen when it is in extension. The piston can do this because there are holes (with valves) which allow the oil inside the piston to pass from one side to the other (in simplest form). Adjustable suspension permits you to open or close the valves to alter the rate of flow, which affects the speed at which the fluid passes from one side of the piston to the other, which in turn regulates the speed at which the spring compresses and extends.
The piston in the damper should be somewhere in the mid-range of movement when the car is loaded at rest or on a smooth surface. So, when the car is moving, both bump and rebound are "relative" expressions, where if the spring gets compressed as the wheel hits a slight raise in the road, the spring (and damper) will rebound, afterwards, to the mid-range position of movement, as it was at rest, or when travelling on a smooth surface. The damper settings are softest when the oil can flow most freely through the valves in both bump/compression and rebound, therefore when both bump and rebound are set at their softest settings the valves are open the most.
Hope this helps.
This guy gives a good explanation of the reason why soft suspension is better on bad/bumpy roads: https://www.youtube.com/watch?v=hGZRairqHNI and how coilovers work: https://www.youtube.com/watch?v=xmr14nCivZA
The springs essentially support the weight of the car at each corner and the dampers are essentially there to control the rate of compression (bump) and extension (rebound) and to prevent the spring from oscillating (boinging). The damper is essentially a piston with holes in it so that when force is applied under compression, the damper can shorten in length whilst the spring is being compressed and lengthen when it is in extension. The piston can do this because there are holes (with valves) which allow the oil inside the piston to pass from one side to the other (in simplest form). Adjustable suspension permits you to open or close the valves to alter the rate of flow, which affects the speed at which the fluid passes from one side of the piston to the other, which in turn regulates the speed at which the spring compresses and extends.
The piston in the damper should be somewhere in the mid-range of movement when the car is loaded at rest or on a smooth surface. So, when the car is moving, both bump and rebound are "relative" expressions, where if the spring gets compressed as the wheel hits a slight raise in the road, the spring (and damper) will rebound, afterwards, to the mid-range position of movement, as it was at rest, or when travelling on a smooth surface. The damper settings are softest when the oil can flow most freely through the valves in both bump/compression and rebound, therefore when both bump and rebound are set at their softest settings the valves are open the most.
Hope this helps.
tertius said:
OK sorry about the thread resurrection but I would appreciate a bit of clarification. I have been fiddling with my setup for a while now and still not sure I am doing this right (idiot). When I look at the shocks I see a + and - sign. Checking my front setup last night I have the following:
5 clicks from full - on the bottom (bump) and 4 clicks from full - on the top (rebound).
My question is is full - essentially the softest setting? So is my current setup close to the softest setting?
I ask as I have found that as I increase the bump setting they become exactly that, bumpy, but it isnt't as controlled as I would like. I am looking for a firm ride but with not too much rebound, firm and flat I would describe the goal. So if I click my front bump up to say 11 out of 16 (5 away from full plus) I find it is fidgety and not there is too much vertical movement? I want hard ride but little or well controlled vertical movement. I am never sure how the rebound will work when I significantly raise the bump. Do I have to raise the rebound in line with it (i.e lots more +), or can should I leave it on a low (soft setting as well)? This seems like an art but I am really not making progress.
I have tried just change the front and check, and also change front and back and check.
I understand that the low to medium speed is what I am adjusting and the high speed ratings are fixed these being 2 way not 3 ways.
OK just been doing some searching and found this
http://www.rapid-racer.com/suspension-tuning.php
After all my changes, looks like I now have pretty much everything wrong :lol:
I have too low bump front and back (as the car is starting to dive and squat)
The rebound has to be set higher than the bump (mine is lower by 1)
The car is bouncing along more than expected (due to the mismatch in rebound to bump, and too low rebound)
So... I will change the settings to
Fronts: bump 10/16 and rebound 12/16
Rears: bump 11/16 and rebound 13/16
And give that a go. Should be hard and hopefully the vertical movement will be minimal.
http://www.rapid-racer.com/suspension-tuning.php
After all my changes, looks like I now have pretty much everything wrong :lol:
I have too low bump front and back (as the car is starting to dive and squat)
The rebound has to be set higher than the bump (mine is lower by 1)
The car is bouncing along more than expected (due to the mismatch in rebound to bump, and too low rebound)
So... I will change the settings to
Fronts: bump 10/16 and rebound 12/16
Rears: bump 11/16 and rebound 13/16
And give that a go. Should be hard and hopefully the vertical movement will be minimal.
Found some guidance..
For tuning your car to a specific track, this is a simple guide:
On corner entry: if the car is oversteering when you're braking into a corner, you haven't got enough weight transferring to the front quickly enough. Solution - either:
• soften the rear rebound dampers (to make the rear rise faster), or
• stiffen the front bump dampers (to make weight transfer bypass the front springs), or
• do both.
If it's understeering when you're braking into a corner, you've got too much weight transferring to the front too quickly. Solution - either:
• stiffen the rear rebound dampers (to make the rear rise more slowly), or
• soften the front bump dampers (to make more weight transfer go through the front springs), or
• do both.
At corner exit, if the car's oversteering when you're accelerating out of a corner, you haven't got enough weight transferring to the rear quickly enough. Solution - either:
• soften the front rebound dampers (to make the front rise faster), or
• stiffen the rear bump dampers (to make weight transfer bypass the rear springs), or
• do both.
If it's understeering when you're accelerating out of a corner, you've got too much weight transferring to the rear too quickly. Solution - either:
• stiffen the front rebound dampers (to make the front rise more slowly), or
• soften the rear bump dampers (to make weight transfer go through the rear springs), or
• do both.
In general, the bump setting is for controlling grip and the rebound setting is for controling handling.
For tuning your car to a specific track, this is a simple guide:
On corner entry: if the car is oversteering when you're braking into a corner, you haven't got enough weight transferring to the front quickly enough. Solution - either:
• soften the rear rebound dampers (to make the rear rise faster), or
• stiffen the front bump dampers (to make weight transfer bypass the front springs), or
• do both.
If it's understeering when you're braking into a corner, you've got too much weight transferring to the front too quickly. Solution - either:
• stiffen the rear rebound dampers (to make the rear rise more slowly), or
• soften the front bump dampers (to make more weight transfer go through the front springs), or
• do both.
At corner exit, if the car's oversteering when you're accelerating out of a corner, you haven't got enough weight transferring to the rear quickly enough. Solution - either:
• soften the front rebound dampers (to make the front rise faster), or
• stiffen the rear bump dampers (to make weight transfer bypass the rear springs), or
• do both.
If it's understeering when you're accelerating out of a corner, you've got too much weight transferring to the rear too quickly. Solution - either:
• stiffen the front rebound dampers (to make the front rise more slowly), or
• soften the rear bump dampers (to make weight transfer go through the rear springs), or
• do both.
In general, the bump setting is for controlling grip and the rebound setting is for controling handling.
Yeah, I think you might have being going the wrong way! I realised that I haven't helped things by quoting "clicks from fully closed" (for the reasons exdos and tertius mention - this is how the manual tells you to adjust them as well). Sorry Phil! :?
Whether it's rebound or bump, "+ve" = harder = more closed = more damped. The easiest way to orient yourself is to think of closing a tap on the top of the damper to firm up rebound, and closing a tap on the bottom of the damper to firm up bump. More bump damping resists the shock compressing. More rebound damping resists it extending.
So by "11/16 rebound" I actually meant five clicks short of the softest setting aka "fully open". You definitely want to be in the softer half of the adjustment range for road driving. At least as a starting point. Recently I've been using "full soft" for long, boring journeys (which would be 1/16 rebound and 1/12 bump using your approach). By most people's standards, e.g. a hungover wife in the passenger seat, it's still a fairly stiff setup.
Assuming you are talking about "+ve clicks" here, bump is max 12, so you might end up with an unforgiving front end and an even more understeery car than normal with those settings. Worth experimenting though - so many factors affect oversteer/understeer.
The main traps I've fallen into are trying to sort the ride by fiddling with bump (it doesn't help it much) instead of rebound (it does wreck it a lot!) and trying to make the rear more planted by changing the damping. I'm still on stock camber and don't have RTAB limiters, so will try sorting those things next. On a recent NC500 trip the bump steer was frankly a little scary.
For "firm and flat", the defaults seem pretty good to me, which are rebound at 8/16 and bump at 6/12 (front), 5/12 (rear)... clicks from fully closed (+ve) this time!
Whether it's rebound or bump, "+ve" = harder = more closed = more damped. The easiest way to orient yourself is to think of closing a tap on the top of the damper to firm up rebound, and closing a tap on the bottom of the damper to firm up bump. More bump damping resists the shock compressing. More rebound damping resists it extending.
So by "11/16 rebound" I actually meant five clicks short of the softest setting aka "fully open". You definitely want to be in the softer half of the adjustment range for road driving. At least as a starting point. Recently I've been using "full soft" for long, boring journeys (which would be 1/16 rebound and 1/12 bump using your approach). By most people's standards, e.g. a hungover wife in the passenger seat, it's still a fairly stiff setup.
pHilli0 said:
Assuming you are talking about "+ve clicks" here, bump is max 12, so you might end up with an unforgiving front end and an even more understeery car than normal with those settings. Worth experimenting though - so many factors affect oversteer/understeer.
The main traps I've fallen into are trying to sort the ride by fiddling with bump (it doesn't help it much) instead of rebound (it does wreck it a lot!) and trying to make the rear more planted by changing the damping. I'm still on stock camber and don't have RTAB limiters, so will try sorting those things next. On a recent NC500 trip the bump steer was frankly a little scary.
For "firm and flat", the defaults seem pretty good to me, which are rebound at 8/16 and bump at 6/12 (front), 5/12 (rear)... clicks from fully closed (+ve) this time!
MrPT said:Yeah, I think you might have being going the wrong way! I realised that I haven't helped things by quoting "clicks from fully closed" (for the reasons exdos and tertius mention - this is how the manual tells you to adjust them as well). Sorry Phil! :?
Whether it's rebound or bump, "+ve" = harder = more closed = more damped. The easiest way to orient yourself is to think of closing a tap on the top of the damper to firm up rebound, and closing a tap on the bottom of the damper to firm up bump. More bump damping resists the shock compressing. More rebound damping resists it extending.
So by "11/16 rebound" I actually meant five clicks short of the softest setting aka "fully open". You definitely want to be in the softer half of the adjustment range for road driving. At least as a starting point. Recently I've been using "full soft" for long, boring journeys (which would be 1/16 rebound and 1/12 bump using your approach). By most people's standards, e.g. a hungover wife in the passenger seat, it's still a fairly stiff setup.
pHilli0 said:
Assuming you are talking about "+ve clicks" here, bump is max 12, so you might end up with an unforgiving front end and an even more understeery car than normal with those settings. Worth experimenting though - so many factors affect oversteer/understeer.
The main traps I've fallen into are trying to sort the ride by fiddling with bump (it doesn't help it much) instead of rebound (it does wreck it a lot!) and trying to make the rear more planted by changing the damping. I'm still on stock camber and don't have RTAB limiters, so will try sorting those things next. On a recent NC500 trip the bump steer was frankly a little scary.
For "firm and flat", the defaults seem pretty good to me, which are rebound at 8/16 and bump at 6/12 (front), 5/12 (rear)... clicks from fully closed (+ve) this time!
Ahhh !! Now I have been out and spent the morning tweaking. OMG what a difference a few clicks make
) Finally after so long without understanding how these setup, I have a really good firm and flat ride for fast road driving. Really pleased with how they are performing now, I knew they were good but wasn't seeing it. Now its clear as day. 
8) :lol: Thanks for everyones contributions to this thread gents
monaco_blue
Member
MrPT said:
Strictly speaking bump steer is unwanted front toe change occurring during suspension compression and is much more a function of the mechanical geometry of the suspension than the shock absorber settings. Heavily lowered cars can be susceptible to this. Ideally you want the track rods to be parallel to the ground when the car is sitting normally; this minimises toe change under compression and droop. But some change is inevitable.
Glad you're making progress, Phil.
I'm not far off stock rear ride height (actually 5mm below the recommended KW max for the spring perch, but still with 100% thread coverage on the perch itself). From the angle of the trailing arms it does look as if bush-limiting will reduce toe change under compression - does this match your experience?
I think you are right though - the rear suspension geometry on these cars seems to be at best "exciting" and at worse "fussy". Doesn't help that it has a light rear (compared to rivals) and you sit on the back axle, but few Z4/Z4M owners seem totally happy with it.
monaco_blue said:
I'm not far off stock rear ride height (actually 5mm below the recommended KW max for the spring perch, but still with 100% thread coverage on the perch itself). From the angle of the trailing arms it does look as if bush-limiting will reduce toe change under compression - does this match your experience?
I think you are right though - the rear suspension geometry on these cars seems to be at best "exciting" and at worse "fussy". Doesn't help that it has a light rear (compared to rivals) and you sit on the back axle, but few Z4/Z4M owners seem totally happy with it.
Anybody’s KWs getting a little clunky? Might just be me getting old and irritable, but I swear that the rears have started making a metallic clunking sound over bumps that they either didn’t before, or did but a lot less audibly. It’s louder on the rear right and I’ve pretty much checked everything around the strut, with the exception of removing the coupe’s roller cover completely.
Top mount nuts are torqued and I’ve given the two nuts that hold the top of the shock to the top mount a decent spannering. A quick search reveals that a bit of clunkiness is common when fitting aftermarket shocks, but I think I’ve already covered the usual causes. Could the noise be coming from the damper assembly itself? I switched to very soft settings about a year ago, and that might have been when I noticed the noise more, now I think about it.
Still really happy with the suspension - particularly on /40 and /35 profile tyres - so this is just a niggle!
Top mount nuts are torqued and I’ve given the two nuts that hold the top of the shock to the top mount a decent spannering. A quick search reveals that a bit of clunkiness is common when fitting aftermarket shocks, but I think I’ve already covered the usual causes. Could the noise be coming from the damper assembly itself? I switched to very soft settings about a year ago, and that might have been when I noticed the noise more, now I think about it.
Still really happy with the suspension - particularly on /40 and /35 profile tyres - so this is just a niggle!
mine has zero noise from the rear shocks but i can hear the front solid mounts doing their thing, nothing a new gt4 didn't do on my last drive, if you getting clunks in the rear id be looking at worn bushings, RTAB maybe? top mounts deformed slightly allowing play??
but i cant see any reason why the rear damper would clunk. Investigate.
but i cant see any reason why the rear damper would clunk. Investigate.