Take 3 - I did some checks. I think it has nothing to do with ride height. But I measured my unfitted BC's. The Rear is 4kg/mm spring rates.
The Tare Rear Weight is 634kg = 317kg/shock = 317/4 = 79.2mm
Loaded Rear Weight from the owners manual = 920 = 460/shock = 115mm spring travel under load.

The Free air space in the coilover spring is 140mm (measured with 5mm pre-load) = 145mm this is how much the spring can compress before the coils close up or clash.
So, the empty car has 145-79 = 66mm clear deflection available for the road.
Loaded there is 145 - 115 = 30 mm free deflection.

It seems plausible that with low damping, this travel could be used up and the springs could clash.
On a Classic the rear shocks are 3kg/mm so even softer.

How does this sound to you? Peter

 

A bump stop is fitted on the piston so how could the springs touch?

dipster

 

A good point, dipster. I checked: the bumpstop is 108mm from the end of the rod, while the spring available travel is 140. So the Empty Car drops the spring by 74mm (in each of these there is the 5mm preload on the spring.)
When the empty car is on its wheels I expect the clearances to be about 65 in the spring and only 34 above the bumpstop.
The bump stop will most likely hit the top plate.
The question si then: does this somehow have something to do with the knocking? If the bump stop is soft enough it might still be possible for the springs to clash (go coil-bound)

 

Today i've been driving mine as normal but with the damping on 0 to start with, 10, 15 and 20 clicks for each road test, and the knocking is still there.

 

I've just fitted new rear shocks and camber plates and it's still knocking.

 

Sounds like its not the shocks/top mounts then.
Could it not be something else in the rear suspension ie, lateral link bushes, trailing link bushes, ball joints, stabilizer clamps, arb bushes/links? stuff in the boot?

Lots to check.

dipster.

 

I have just fitted my BC's today. 2006 STi, 5/4 springs. I am VERY CHUFFED !! Thanks Apex. Very good value and I am happy with the performance.

I have the knocking but it is only on a severe bump.
Despite all my blah blah above, it is not spring clashing.
I haven't put my seats back because I just got finshed as the light went.
But as I went for a few rides and tried different damper settings, I got the knock. It's in the top plate and I think it might be the nitrile donut that is clamped at the top. I won't make any confident pronouncements now, but tomorrow I'll go for a ride and sit in the back while my son drives and watch closely.
But the BC's are so much better than stock suspension (and quite a lot lighter, too - the rear coilovers are 3kg lighter each)
I am running 7 clicks front 10 rear and the ride in town is still very good. More experiments to come...

 

I must agree, they are a great improvement over the std STI setup.
Running 8 clicks front and back,
1.5 degrees negative camber all round,
zero toe front and back,
and a whiteline 22mm adj rear arb on middle.
Really impressed would be an understatement!

I only get knocks over potholes as well, to be expected really with coilovers by what I have been told.
The STI is hardly a quite car, what with tyre noise and diffs etc.


dipster

 

Just so I can check the degree of camber I'm currently running does anyone know what the lines on the camber plate indicate in term of "amount of degree's"

Cheers

 

They are just a referance and mean nothing as far as degress.

dipster

 

I agree, BC Coilovers are fantastic, great ride and build quality. I just find it strange that you don't get any noise or knocking from the front, aren't they identical to the rear?

 

I've got a set of the inverted BC's to fit to my Classic Wagon too. I'm currently using a set of GAB coilovers that have never knocked and seem like a good set of road use coilovers but they lack the travel of the BC's for the proper track work that my wagon will be doing.

I've been trying to get the time to fit them for 2 months now but my new engine has been taking longer than i anticipated but i should get the car back around the 23rd Feb so will get at them then and then take the car for a full geo setup. I'll post up here if there are any noises!

Cheers

James

 

What about KW Variant's ??? Anyone had knocking on those?

 

Can anyone suggest a few good Alignment places in the Midlands or within reasonable range? So far I have
TSL
Powerstation
Carnetix
Rager Clarke
Graham Goode

 

When fitting coilovers with solid topmounts, its easy to hear many more noises that were not transmitted into the car before.
Like lose hubnuts, rear diff bushes etc.
I have various 'noises' but I could hear these before with the rear seats out and std factory shocks.
As said before coilovers of all makes can and do knock when going over potholes, nothing new and nothing to worry about.

dipster

 

Yes they do, I read a old post today by our friend 911 saying they can knock.

dipster

 

I had BC's fitted a couple of weeks back and I have also had the knocking sound coming form the rear. The guy who fitted them siad that he could hear stuff jumping around in the boot as dampening was quite stiff. I just assumed that was what I was hearing until I read this post. Thinking back it does seem to only happen when I hit a decent sized bump or blemish on the road.

Still I'm chuffed to bits with the ride height and quality. Far better than my standard WRX suspension.

 

chevron, stafford. HIGHLY recommend them! 01785 223 336 ask to speak to simon, or book in for geometery set up with caroline and they will take care of you

 

I just fitted rubber top mounts today and I still get the same knock, must be a coilover thing!!