Lowering Bilstein Dampers - Damage?

[colourclassic]

I purchased a set of brand new Bilstein B6 dampers for my R33 approximately 4,000km ago. Obviously these are not height adjustable, but are complemented by a set of King Spring 'Lows' to give the car a slightly lower CG and better looks.

I would like to machine some circlip grooves for the lower spring perch to further lower the car approximately 15-20mm. I understand the relationship between height and handling, so no need for an explanation on that.

My question is, does lowering a gas-charged shock absorber which is still relatively new pose any danger as far as shortening its life or causing damage to the valving/internals? Obviously the dampers compression stroke would be reduced, and this is my biggest concern as far as longevity and durability.

Cheers!!

[GTSBoy]

15-20mm is too far. SK's kit B6s (of which I have just installed a set of 4 on my R32) have extra grooves machined in above and below the original pair. These are only ~5mm apart, so you get about an extra 10mm up and down.

I found that Kings lows (KDFL-101 and KDRL-102) sat my car ~30mm too low even when setting the spring perches in the highest grooves. I had to go to GTR springs KDFL-116 7 KDRL-87SP and set the perches in the bottom original slot in order to get the ride height perfect (in line with both what SK recommend and what is also legal in SA). That gives me about 355mm at the front and 350 at the rear.

There is no way that a lower CG and looks is worth compromising the handling of the car that much by dropping it as far as you are asking for. How high is it now?

[djr81]

Well try this for a trick. Put the car on full lock (ie turn hard left) and stick your head under the guard. Look to see how much shock travel you have at the current ride height. If you like you can try and measure the height between the top of the damper and the bottom gof the bump stop. Then have a think about how much travel you will have when the ride height is 20mm lower......

[colourclassic]

Cheers guys.

GTSboy, the car is currently sitting at roughly 345mm both front and rear. I actually had a set of grooves machined to my specification to give the car an extra ~5mm of forward rake. I was thinking of going an extra 10mm lower to 335 front and rear.

djr, I'll have a look today, but you're both probably right, 20mm lower will be excessive.

I'm still interested in my original question though, does operating a new damper in the final few inches of its travel cause damage to the valve stack, piston or any other components?

[djr81]

No is the short answer. But the complication is you dont really want it bashing the bump stop repeatedly and definately dont want it bottoming out.

To get more travel you need to change the hats on the dampers (The bits that hold it to the chassis)

[GTSBoy]

Agreed. Provided it doesn't hit the internal bump stops you're OK. The actual position in the travel doesn't determine the way the damper operates at all. The valving is all about piston speed.

Way back in the way backs, when we used to lower HQ (and similar) Holdens until the front crossmember was ploughing grooves in the road, you'd buy dampers (sorry, back then they were shockies) with a shorter body simply so they'd run closer to the middle of stroke and avoid the internal bump stops.

Of course we usually had air shockers in the rear.......

[colourclassic]

"The actual position in the travel doesn't determine the way the damper operates at all."

Sweet, that answers my question!

Cheers guys!

[NISSAN GTR]

Just to add B6 Dampers are designed for use with lowering springs - maximum lowering is 25 mm , i have been running a set forever with Tein S Techs

[colourclassic]

Cheers mate, I had down-travel limiting spacers installed to enable a slight lower ride height while keeping the springs captive. Hopefully their life isn't effected.