Rebuilt Bilstein Dampers - Advice Please?

[revilla]

I've been convinced for some time that my dampers were well past their past. They've been heading slowly down hill, slowly enough for me not to realise until they were properly shot.

In the meantime various people have tried to convince me that Bilsteins are just not up to the job, they are like that sir etc. etc. and that I should be investing large amounts of cash in Quantums or Nitrons.

Last night I went out in mucus72's newly built and frankly superb 420R. His car is an SV (like mine) on standard Bilsteins with adjustable platforms (like mine) and we covered roads that I know well and drive daily, so I was able to compare the ride qualities.

The difference was night and day! His car was smoothly gliding over sections of poor surface that would have mine flapping about like a stranded fish. If my car rode like that I would be note than happy. In comparison I would mine has a clear tendency to jolt and crash over minor ruts and bumps, then bounce. We also compared the feel of pushing down on the rears of our cars; where his dampers were fairly firm and then seemed to rise back quickly, mine compressed easily but were then really sluggish to rebound. Completely different.

So I'm now even more convinced that all I need is a decent set of Bilsteins that work as intended. I don't need anything more special or track oriented. Car is strictly road use only. Car is also a "keeper", so I want a solution that will last.

I'm aware that dampers can be sent back to Bilstein for a refurbish. My dilemma is whether I should do this or buy some new ones. A refurbish I think is about half the cost of replacement. 

Has anyone had experience of refurbished Bilsteins? What is and is not covered by the refurbishing process? Do they replace the end bushes? Do they repaint them (if not, easy enough for me to do, just interested). What sort of turn around time do they offer? 

Should a rebuilt damper perform every bit as well as a new damper?

Any experiences and advice appreciated thank you.

[Dr Slotter]

A Bilstein refurb pretty much means they will replace any components that are worn out or have failed but won't do any comestic work. I imagine they would if asked though. The important bits are as good as new. They will do the bushes if asked but I think they make them specially rather than have a stock of every possible bush size.

I had them do my fronts last year and other than it taking a bit longer than expected because they had to make a new component from scratch for me, it was fine. Perhaps two weeks turn around, I can't really remember. If you give them a call they'll tell you how busy they are.

[Wrightpayne]

They are at Meridian in Leicester so pop in and see them.

Ian

[nickh7]

I've tried 4 different sets of dampers over the 20 years I've had my car and the biggest upgrade was moving to Freestyle over Bilstiens, I then went backwards with two stiff a set up with Alloy AVOs.  

earlier this year I switched to Nitrons and the control was another big step forward but the perfect combo has been the fitting of the R888rs  . I can't get over just how brilliant they work together. I'd ask what tyres you have v the ones on the 420R? Perhaps you need to try a combo of the two

[ballisticsupersport]

I'm no expert on dampers, my 7 has the same ones fitted as yours does. I recently changed from 6 X 13" wheels on cr500's all round to 6" front 8" rear with ZZS tyres. Putting it bluntly it ruined my car and it was almost impossible to keep in a straight line on anything but perfectly smooth tarmac, tram lining was also a big issue. I then got my car setup properly 'flat floored' and it now handles better than ever and is a joy to drive on road and track.

The reason I mention this is that it seems that 7's are so sensitive to setup, even down to seemingly insignificant variations in tyre pressures that it's almost impossible to put the difference between two cars down to just the dampers.

The dampers could well be shot but it might be worth taking the car to someone for their expert opinion.

In any case, I would have thought sticking with standard Caterham fit Bilstiens is probably the way to go particularly if you're not going on track.

Hope you get it sorted and are back enjoying your car soon.

Tom

[revilla]

Thanks for the input re setup and tyres. I've actually been through a number of different tyre and pressure combinations and the ones I've got on at the moment (T1Rs at 16psi) are by far the best ones for me of any that I have tried. R1Rs had a lot more grip but tramlined horribly unless I blew them up silly hard which made the ride even worse. These ones seem to suit my road driving quite nicely and I enjoy feeling the car moving around a bit.

The ride issues have to be honest just slowly gone downhill over the time I've had the car. The tyre swaps have made little difference other than as described above and I've had it flat floored. Recent corner weight check also showed it well balanced. Tracking is about 20' toe in which is where I find I like it best. I've tried tweaking tyres pressures in both directions and I can feel the difference, but they don't affect this problem.

To be honest it isn't a problem keeping it going in straight line, it's more a problem of bouncing up and down! With these tyres and settings, even on rough uneven surfaces it just tracks straight and true, you just bounce along. It's reached the point where I actually feel sick. Today I was noticing just how much bouncing up and down I was doing on apparently smooth sections of the M1! I think the dampers are just not ... well .. damping.

Pushing down on the back of the car the dampers give quite a long way and quite quickly. They then slowly rise back again over several seconds. A good shove and goes straight down, then you can actually stand back and watch it slowly creep back up. They seem to be quite soft in compression and very stiff in rebound. That doesn't sound normal, and doesn't seem to be the behaviour of other Sevens I've tried bouncing. which have more resistance to compression and a much much faster recovery. So I think on the road they are just letting the springs compress until they hit the bump stops when you hit a hump and then not really allowing them to recover before the next knock. What I'm seeing when I press the back down seems to fit with the feel I'm getting on the road.

I suspect the dampers are as old as the car, which is now 13 years. I've certainly never done anything to them in the last four years I've owned it. I don't know how long they tend to last for, but I do think they are getting a bit tired.

[Mucus72]

Didn't realise that they were only down the road as WightPayne says. I'd definitely pop down Andrew and get them to accurately diagnose. Would be an interesting experience and yet another reason for a blat, even if the bucking bronco makes you sick ;)

[tomwood]

Hi Andrew, if my own experience is anything to go by then I'd say there is a very realistic probability that the dampers are shot as you have surmised yourself. In my case I managed to kill one of the dampers after less than 3 years/2500 miles and 13 years is a while....

In my case I think I was unfortunate to 'pop' one whilst 2 up in the car having gone through a particularly deep depression in the road at speed. Think this managed to rupture the seal on one of them necessitating a rebuild.

I have just this week received by refurbed shock back from Bilstein. They were very helpful and the turnaround was something like 3 days from them receiving it in the post and sending it out again to me so about a week all told, not bad if you ask me.

they re-shimmed it, put new seals on it, filled it with oil and repressurised it. Cosmetically it came back a lot cleaner than when it went so all good there. I plan to fit it back to the car when I get home later.

when I took it off the car I did a bit of testing on it, compressing it and watching the rebound. It was similar to the response you are seeing with yours, didn't seem to rebound with any great speed.

including postage and VAT etc it was something like £115 for one so assuming you don't get any economies of scale doing them all at the same time then it's going to be the best part of £500 to have them all done but then what's a brand new set of Nitrons etc going to cost you?

lets be honest they won't be in the best of condition after 13 years so you'll definitely get a benefit in having them all looked at. My SuperSport R rides beautifully on the standard Bilsteins so they are definitely good when fully working. Also if you don't track the car much do you really need anything more advanced?

Tom

 

 

[p.mole1]

My car was on standard Bilstiens,none adjustable platforms and it was abysmal,it darted all over the road tramlined, a real handful on bumpy roads. Also my car had no rake and I had no way of lifting the rear.

They were however 21 years old and had covered 22000 miles,the bushes were shot but it had really good ride quality.I changed to Nitrons and it's like a different car, had my dampers had adjustable platforms I would of probably had them refurbished (depending on cost).

[revilla]

@p.mole1 - Thanks for the info. Mine may be only 13 years vs. your 21 but they've covered 30000 miles. I do have adjustable platforms and in terms of geometry I think I've got the car set up pretty well (i.e. to my liking). It doesn't tramline, it's lovely and stable, no darting around. Just a harsh ride.

[revilla]

So yesterday I had two opportunities:

1) 160 miles of blatting on interesting back roads with some rather quicker cars that put my suspension to the test. It was really struggling.

2) Lots of chances to compare the way my suspension felt with other cars at the museum trip. By this I mean pushing the car down and feeling how stiff it was, how far down I could push it and how it bounced back up again, rather than actually driving them (but I've already done a couple of driving comparisons and I know mine feels different on the road).

What struck me was that while there was quite a range of stiffnesses, every other car I tried seemed to bounce back quickly. Not one single car had anything like the sluggish rebound that mine shows. A couple of other people also took the opportunity to bounce mine in return too and the response was generally "Ewww, it shouldn't do that!".

With a good shove of my (not inconsiderable) weight on one back corner, I can push mine down rapidly through most of its available travel. It then takes several seconds to creep back up. You actually have time to walk round the back of the car and push the other corner down while the first one is still visibly rising.

I think on the road they are working like ratchets, being very soft in compression and very stiff in rebound. Bumps are compressing them and they're not having time to recover before the next bump compresses them again, so each bump winds the ratchet up a notch and I end up with the springs compressed down and running on the rubber bump stops.

I know tyres and geometry are all part of the mix and the tyres I'm running are budget road tyres (Toyo T1Rs) which aren't doing me any favours when it comes to ultimate grip in corners but from the investigations I've done I'm pretty much 100% sure that my dampers are the real source of the ride problem now.

[Simon.Rogers]

There is something rather odd happening.

Yes they may well be a little light on compression but I would expect them to be just as light or weak on rebound also.  Its the spring that pushes the damper back apart so its odd that the damper is restricting this to a greater degree than others,

Your description of what could be happening is just what happens to an over damped car in rebound.  Its called "jacking down".

I hope you make the best decision for your use.

My only one point that I have seen typed above that I don't agree with is that its only for road use and so don't need the ultimate damper or words to that effect.

Whilst I would agree that your not chasing a "time" on a lap I really think that good dampers can make more of a difference to a car on the road than they can on track.  Conditions on the road are far more varied and uneven giving a requirement for much better damping.

[Alan Archer]

Well having read all of the above, yesterday I tried it on mine, I sat on each of the rear corners in turn and the back went down approx 35mm, I then had time to get off, turn around and watch the back end still coming back up, it took a good couple of seconds which sounds exactly the same as Revilla is saying!

Alan

[SM25T]

Maybe you need your (ordered) new spring dampers soon, Alan !

[stuart147]

Just thought I would post regarding my experience of Bilstein service. 

All I can say is how fantastic it is. I took my dampers over to them in Leicester a couple of weeks ago and fetched them back yesterday. To say that they look as good as new is an understatement. The guys in the service department have fantastic product knowledge and will answer any questions that you have regarding the work.

Stuart

 

[micksmetafors]

I had 4 Bilstein M0 dampers re-furbed and re-valved last year. There are different specs available for re-valving to if you want. David Masters provided the info and some of them are heavily damped in rebound. I haven't still got the spec sheets nor can I remember the different M numbers. I went for M2 front and M0 rear if I remember well. M2 rear seemed very hard for road use.

Not sure if this will help you,

Steve