Faulty Damper(S)? Excessive Pitch/lean Since Gti-6 Conversion

[Anthony 1,002]

Curious one this which has had me scratching my head.

 

Ever since fitting the boat anchor that is a GTi-6 into my 205 I've never been happy with the handling or the nose-heavy feeling, which I had put down to the addition ~30kg weight over the nose and the Eibach 7001 springs I had at the time being too soft to properly cope with that extra weight.

 

Certainly this tallied up given that the front was sitting noticeably lower with the iron-block GTi-6 lump compared to the alloy-block 8v.

 

With this in mind, I went through various sets of springs trying to find something that sat at a sensible height and which was a bit stiffer to cope with the additional weight.

 

Tried a few different springs that had been recommended by others on here onto the original dampers (a set of Skip Brown Bilsteins) - standard 309 GTi springs, 206 GTi lowering springs, some Xsara VTS lowering springs etc, but none were right, either sitting too low or still feeling far too soft and nose heavy.

 

Then I tried a pair of Bilstein Challenge dampers I had in the garage with some Koni purple springs on them which always sat a little high on an 8v so I figured would be about right and indeed with them fitted, the car felt much better and you could actually drive it in anger without feeling like you were on the verge of a major accident.

 

Finally got around to swapping those springs over to the SBC dampers last night and... it's feeling way too soft again with excessive pitching/leaning. Hmmm.

 

Logically then it has to be the SBC dampers that are at fault, but I can't understand how or why. In every other way they feel perfect as you'd expect for sub 10k road mile dampers - firmly damped and not a hint of bobbing or failing to settle after big undulations as you'd normally see with tired dampers - and they're much stiffer than what many other people are (presumably happily) running on GTI-6 and other XU10 conversions.

 

When I say "excessive pitch/leaning" I'm talking leaning so heavily on the outer front wheel when you turn in with any degree of enthusiasm that the tyre will hit the arch with a typical lowering spring and the inner rear wheel will be lifted a good 6+ inches off the ground and come back down with a thump. Couple that with a change of direction from one way to the other on a trailing throttle and you get considerable amounts of roll-oversteer too - benign enough that you can easily catch it, but clearly not right.

 

You'd think from driving it that the front ARB was disconnected or broken, but it doesn't appear to be (disconnect one end and try to move it and you can probably only bend it an inch or so) and is unchanged since it drove nicely with the 8v.

 

The curious thing is that once you've got the car turned in and past the alarming nose-heavy pitching, the balance of the car is very good - the front end has lots of grip, you can steer the car on the throttle perfectly and it'll happily lap a private roundabout with the tail sliding couple of degrees out of line with no drama at all.

 

The same dampers when fitted to the 8v prior to converting drove beautifully, and whilst another 30kg odd over the nose isn't insignificant, I can't believe for a second that it should have this much of a drastic impact on the behaviour of the car on turn-in. As said before, they've only done 10k or so road miles. Certainly I've driven 205's with iron block engines in the past on much weaker dampers and nothing like this.

 

The full spec of the car suspension wise is as follows:

 

Front:

Skip Brown Bilstein front dampers with 200/100 inserts

309 GTI front wishbones

205 GTi front ARB

Newish standard top mounts

Tracking set to zero

 

Rear:

205 GTi rear beam with solid mounts

Skip Brown Bilstein dampers with 350/260 rating (IIRC)

20mm torsion bars

23mm rear ARB

306 GTi rear trailing arms (so 1.2 degrees negative camber)

 

Any ideas? Can a faulty damper behave like this or is there something else I'm overlooking?

 

TL;DR: Can faulty front dampers cause a car to excessively lean and pitch but otherwise drive, feel and behave perfectly?

[Gman 29]

To answer your final comment Anthony, I would say yes.

 

I recall that before fitting my challenge spec dampers, every time I jumped on the anchors the car used to corkscrew everytime. Initially I thought it was some slight brake imbalance, but I changed the front shocks and springs (the old springs were old, but visually appeared fine) and the corkscrewing stopped.

 

This clearly suggests that the shocks do work with the springs to provide additional compression resistance when cornering, and thus if the shock is knackered, the spring/shock unit will compress further and thus impacting on the role of the car.

 

There are people better placed to advise, but just my 2p worth

[GilesW 41]

Ask Henry1.9gtiwhatsit.

 

After meeting him at the weekend it seems he's tried every combination/adjustment of suspension and geometry on a 205 that anyone ever could.

 

But in my (in)experiance - failing/failed/incorrect dampers could certainly lead to similar handling issues.

[Anthony 1,002]

I know Henry well enough - it's me that put his current beam together for him

 

I'll be a little miffed if the dampers are broken already, although it's not the end of the world given that they're rebuildable at fairly sensible money. Certainly it's thrown me as they otherwise seem to drive/behave perfectly.

 

The SBC dampers themselves I know should be fine with the weight and hence I'd discounted them as being at fault given that they've done so little miles and drove so well on the 8v. I know Allye on here is running my old SBC dampers (with slightly softer 200/80 inserts) quite happily on his 309 V6 and 2052006 (Pete) has a almost identical suspension/engine setup to me and he's been quite happy with his AFAIK other than it being a little low with the standard SBC springs.

[welshpug 1,646]

Theyre pretty bloomin old arent they Anthony?

[Anthony 1,002]

They were first used in 2011 IIRC when Feb bought them so not particular old.

 

The ones that were on Feb's original Sorrento (one you did the clutch on at some point I believe) that I subsequently bought off him were certainly much older and are what I suspect you're thinking of, but were still in good working order when they were sold.

 

I'm not convinced that age/mileage in itself is that much of an issue - the SBC dampers on my 306 hatch are years old and have certainly done well over 100k miles now. Despite that, they still subjectively drive and handle very nicely, although I am planning to get them rebuilt prior to swapping them onto the estate replacement.

[welshpug 1,646]

Yeah I did the clutch when geraint had the car, in between feb owning it again, they were on there then and im sure it was a lot longer than 3 years thats the set I was thinking of indeed.

 

Sounds like the high speed damping has gone, no idea how the innards work though, Phillip m could tell you most likely!

Edited July 10, 2014 by welshpug

[Slo 283 1 Cars]

Anthony I've just fitted a pair of these to my car last week and my god what a difference. It just floats my boat anchor around now.

 

Before it was a bit way and a bit whoa on bends however I had fitted second hand shocks that were clearly worn out when compared to these new ones when i was swapping the springs.

 

Also got matching rears to go on and new mounts but cba atm

[Miles 331 1 Cars]

I think it's the SB valving thing, A mate of mine and who you know (Das) has swapped his SBC dampers out and gone to Koni and seems happy buy time will tell after his mapping later in the month, He's gone from 8v to GTi6 now.

Having driven a couple myself too I have never thought much of the set up either.

[Rippthrough 98]

It'll be the low speed bleed for the compression that Mei, rather than the high speed. It's common if the oil has started to degrade and the innards rely more on bleed than the shim stack for low speed control.
They are relatively soft on low speed compression the last time I took a spin in a 205 with some on - but that's partly why they do find so much grip and allow you to steer on the throttle even on broken roads, sounds like yours have just gone a bit too far Anthony!

[acox99 74 1 Cars]

Have you tried playing with tyre pressures? Could be a combination of dampers and tyres waking about in the rims

[Stu 18]

It certainly sounds like the valving to me, i run Koni's on mine and like you, experimented with various spring setups across the same dampers after swapping over from an Mi to a '6 engine and ultimately ended up with some 306 D Turbo lowering springs that seemed to have a decent increase in spring rate but still sat right.

 

I also needed to firm up the dampers to loose the 'floaty' sensation just as it was put it into a bend; soon as it was loaded up it was fine, but it lacked confidence on the initial turn in.

 

Maybe the SB dampers fine, just not got the bump/rebound characteristics that suit the boat anchor hung over the front wheels

[Henry 1.9GTi 36]

my meg does the same anthony. way too much movement at the front feels like its rolling over the tyre due to lack of support. Just a low speed bump setting imo. And then if its got too much rebound will try and 'suck' it down or not let the front recover causing some odd direction change issues. Cars with switchable dampers feel the same in comfort in terms of support at the front, and then alot better in sport/track.

 

Doesn't have to be anything wrong with the damper to make it behave poorly to a certain mass / spring setup as I'm sure you know anyway. As per description I would expect the challenge spec are firmer than the SBC ones?

[Anthony 1,002]

Lots of very good replies these, thank you

 

Sounds as if it is a damper related issue, although not whether it's that they are failing or whether they're just simply not valved to cope with the additional weight. Either way, sounds like in the short term my best bet is to refit the Challenge dampers to keep the front in check and to go from there.

 

Longer term, I think I'm erring towards going to go back to an alloy block engine as I'm not particularly smittent with the GTi-6 and even with the Challenge dampers fitted the detriment to the handling balance/sweetness I loved about the 205 is an unacceptable trade off to me.

 

Anthony I've just fitted a pair of these to my car last week and my god what a difference. It just floats my boat anchor around now.

 

Before it was a bit way and a bit whoa on bends however I had fitted second hand shocks that were clearly worn out when compared to these new ones when i was swapping the springs

They're Bilstein B4's and I've actually got a pair in the garage.

 

They certainly work well as an OE replacement damper, but on paper atleast they're a downgrade over what I've got now and certainly to drive they're much softer than the SBC dampers (which in turn are a little softer than the Challenge) although I've no idea of the exact rating of the B4's

 

That said, last 205 GTi-6 I drove on B4's and otherwise standard suspension drove well enough from what I remember of it, just feeling a little more ponderous and inert than an 8v would on similar suspension. I expected broadly similar with this, just with the notch raised up a few clicks, but instead it's way worse.

 

 

I think it's the SB valving thing, A mate of mine and who you know (Das) has swapped his SBC dampers out and gone to Koni and seems happy buy time will tell after his mapping later in the month, He's gone from 8v to GTi6 now.

Having driven a couple myself too I have never thought much of the set up either.

Interesting that Das has swapped as he was happy with the suspension when I last saw him and it certainly seemed to work well enough from the passenger seat. I spose I could just phone him to ask, but do you know what his reasoning was for changing - was it that the SBC stuff wasn't coping very well with the additional weight or for some other reason? Only ask because on paper and from what I've driven of both setups (I've owned a couple of cars with Koni yellows) I'd say that they're only on par with the Bilstein's and not a step up like say AST's would be.

 

With the 8v fitted though I always found the SBC setup worked very well as a road car, particularly on typical British roads that are hardly billiard table smooth.

 

 

It'll be the low speed bleed for the compression that Mei, rather than the high speed. It's common if the oil has started to degrade and the innards rely more on bleed than the shim stack for low speed control.

They are relatively soft on low speed compression the last time I took a spin in a 205 with some on - but that's partly why they do find so much grip and allow you to steer on the throttle even on broken roads, sounds like yours have just gone a bit too far Anthony!

Thanks Phil

 

I guess the question is can a man of your talents tweek the valving so they'll cope with this lump of pig iron without unduely negatively impacting what I like about them? I appreciate that you can't defy physics.

 

To an idiot like me ( ) that's a bit clueless when it comes to the finer points of dampers and valving, am I correct in thinking that low speed is the (comparitively) slow movement in terms of roll and pitch as the damper compresses, high speed is more (comparitively) fast movements like bumps, and rebound is controlling the return from a compressed to normal uncompressed state by slowing the release of the stored energy in the compressed spring?

 

Have you tried playing with tyre pressures? Could be a combination of dampers and tyres waking about in the rims

I've had a quick play around and settled on 30psi for the front axle, but it's not a tyre issue - the feeling is quite different to how it feels when a soft sidewalled tyre is getting pulled under the rim, but rather feels like the body is just flopping over onto the outer front wheel.

 

The front tyres themselves are actually providing surprising amounts of mechanical grip despite the shell pitching around like a boat in a storm and it will turn in exceptionally well.

 

 

It certainly sounds like the valving to me, i run Koni's on mine and like you, experimented with various spring setups across the same dampers after swapping over from an Mi to a '6 engine and ultimately ended up with some 306 D Turbo lowering springs that seemed to have a decent increase in spring rate but still sat right.

 

I also needed to firm up the dampers to loose the 'floaty' sensation just as it was put it into a bend; soon as it was loaded up it was fine, but it lacked confidence on the initial turn in.

 

Maybe the SB dampers fine, just not got the bump/rebound characteristics that suit the boat anchor hung over the front wheels

Out of interest, which 306 TD springs did you end up with? Last time I tried 306 springs they sat too high hence trying Xsara springs instead (given that standard Xsara VTS springs lower a 306 about 30mm)

 

I wouldn't describe the current situation as floaty, or atleast not in the way that I would use the term. My 306 estate is more what I would call floaty as the comfort spec dampers just can't keep the body in check if you try driving it in anger - the relationship and link between body movement, wheel movement and forces acting on the car just starts to get vague and blurry.

 

The 205 doesn't seem to get floaty at all in the way that I use the term, but I think that is probably more lack of rebound(?) damping that makes it feel like I'm describing.

 

my meg does the same anthony. way too much movement at the front feels like its rolling over the tyre due to lack of support. Just a low speed bump setting imo. And then if its got too much rebound will try and 'suck' it down or not let the front recover causing some odd direction change issues. Cars with switchable dampers feel the same in comfort in terms of support at the front, and then alot better in sport/track.

 

Doesn't have to be anything wrong with the damper to make it behave poorly to a certain mass / spring setup as I'm sure you know anyway. As per description I would expect the challenge spec are firmer than the SBC ones?

Yeah, that description seems to fit pretty well - feels like a lack of support and the body just sort of flops over onto the outside front corner, much like it would with the front ARB disconnected with mild spring rates.

 

I am just amazed how a mere 30kg odd additional sprung weight over the axle has had such a huge difference given how comparitively small percentage it is overall, assuming of course that nothing has failed/degraded in the meantime since I last drove them with the 8v.

 

It's a dramatic enough change from one set of dampers to the other that my missus noticed instantly from the passenger seat. I can't remember the exact damping rate figures for the Challenge dampers now, but they're in the ballpark of about 20-25% stiffer from memory.

[2052006 10]

 

I am just amazed how a mere 30kg odd additional sprung weight over the axle has had such a huge difference given how comparitively small percentage it is overall, assuming of course that nothing has failed/degraded in the meantime since I last drove them with the 8v.

 

It's a dramatic enough change from one set of dampers to the other that my missus noticed instantly from the passenger seat. I can't remember the exact damping rate figures for the Challenge dampers now, but they're in the ballpark of about 20-25% stiffer from memory.

 

I can't see how this can be the case though Anthony. Like I said, mine has never, at least as far as I'm concerned, handled like you described in your first post and it's a very similar overall set up. I'm sure I'd have noticed. What I can notice, I think, is a combination of the front setup not being as spot on as I'd like (too low with the SBC springs, wishbones not at the correct angle and the boat anchor effect). I'm pretty sure it doesn't lift an inside rear and like I said, the only time it scrubbed the front arch was at Brands Hatch, as it went into that big dip just after the pit straight (can't remember the name) resulting in a lot of compression, obviously. Never down that on the road though.

 

If your SBC dampers worked fine with your 8v, surely an extra weight of 30kg isn't going to make them completely unsuitable? I think they must be "broken" (technical term ​ ) in some way, rather than just unsuitable for the weight of the engine.

 

It's a pity mine's in bits, otherwise it would have been useful for you to have done a comparison. And I would have loaned you my dampers, but I've just stuck the struts back on, and now the rear of the car is on axle stands, so can't easily take them off!

[Miles 331 1 Cars]

He just felt it was never quite like it used to be when his brother had it on Koni's I believe, As said the couple of times I drove it mainly on the SBC springs it never felt great but improved allot with Eibach's fitted but still off the Group N spec, Anyone know what setting's SBC used as they would not tell Das.

He did even think about removing the neg camber kit too which might be on the cards yet but until he's had it mapped we will find out.

[Rippthrough 98]

Without stripping them to see how sophisticated the internals are, I can't really say for certain - but give what they are and the price I can guess they're nothing particularly fancy inside, probably a rebadged twin, so whilst they could probably be made stiffer, chances are it would also impact the ride and possibly end up with a bit more hysteresis and fade.

Anyone opened a set up to see what the internals are like?

[welshpug 1,646]

I think theyre pretty much the same insert as the height adjustable units, my bmw shares nigh on identical type inserts too.

[EdCherry 34 1 Cars]

Probably not worth the time and effort with the SBC dampers - it would be much easier for Phil to tweak the Bilsteins inserts and give a much better overall damper than fiddle with the SBC stuff.

[welshpug 1,646]

Sbc units are bilstein.

[2052006 10]

Anthony, if you've got some B4s in the garage, could you not stick those on? If they are stiffer than the SBC units, then you know there's a problem with the SBCs, rather than them just being unsuitable.

[Batfink 201]

There's no way the b4's are stiffer

[unariciflocos 49 1 Cars]

An mot station back at home had a vibrating platform for testing dampers. 10 quid and I'd get two nice print outs with damper response to every possible frequency and amplitude of travel. Maybe you have one around and it will answer your question for good.

 

My guess would be old worn out or faulty units. Any of the sets you tried new or freshly refurbished?

[Mac Crash 78 1 Cars]

Just wondering where these "private roundabouts" are?