Sachs Damper Protection

[Patrick Bateman]

What are people currently doing with theirs over and above the crap rubber boots that came as standard?

As I've mentioned in the main Sachs rebuild thread, a scraper/wiper seal mod is what I was wanting but Cornering Force are currently unable to offer this so my freshly refurbed dampers are standard.

I forget the exact kit but I know there was a different rubber boot/bump stop that has been mentioned in the past although not sure of success.

 

[NickReilly063]

Do you mean these Patrick - these are the original ones -

Soufflet et butée amortisseur Sachs Clio 2 RS

Retrouvez tout pour l'entretien, la préparation et l'optimisation sur www.optimiz-access.fr Spécialiste pieces Renault Sport Alpine et RS PERFORMANCE

www.optimiz-access.fr

 

[Patrick Bateman]

Yeah they're the originals which don't do a huge amount to stop the ingress of dirt but there's an aftermarket kit available that's been mentioned in the past.

Will need to have a dig and see what it was.

 

[marrow]

Frayz’s Inferno orange 182 - Back in the old flame

Not much happening on WZD lately. However something I’ve had for a while has been a freshly powdercoated front ARB I’ve been meaning to fit. The ARB bushes are literally the very last bush on the car to replace. I had been putting them off as they have a reputation for being a royal pain in the...

cliotrophy.co.uk

Check out what Frayz uses.... any help?

 

[hoolio]

Powerflex do this kit.

 

[Patrick Bateman]

That’s the exact kit I was meaning.

Anyone have decent feedback on it?

 

[hoolio]

Used with the original top “bump stop” and secured over the top of the damper with the cable ties ( I had an idea to use double sided tape around the top of the damper also) I think the shaft should be kept pretty free of dust and any other crap.

 

[James__H]

That’s the exact kit I was meaning.

Anyone have decent feedback on it?

I can't directly, as I haven't tried it. If you're using them purely as a gaiter/dust tube then they're probably OK. But... I can lend some insight into development of 'bump stops' from some work a few years ago.

The primary function is load management into the body (in parallel to the spring), and with it the wheel displacement.

They're also known as spring aids, as they contribute to the effective spring rate of the car.

OEMs finely tune these for the following considerations:

• So the maximum combined load into the body is reached at the end of wheel travel (at zero speed). The unsprung mass will have been controlled (and damped) over the full wheel travel.
• So the wheel and tyre don't smash into the wheelarch
• The gap from the 'nose' of the spring aid to the bump cap of the damper (where the seal pack is). A gap allows only the main coil spring to contribute to the wheel rate (also know as the on centre wheel rate) before the spring aid is engaged at larger wheel travels
• The nose shape can be designed for a softer, less perceptible engagement point
• Density (more dense = less total travel = higher initial rates)
• Length - has to be tuned hand in hand with density to achieve point 1 and 2.
• 'Rate rings' can be added to a low density spring aid, to achieve soft initial engagement but quickly ramp up the rate if you have short wheel travel or awkward spring aid packaging.

I won't bore people with the different key areas on spring aid force/displacement (or even rate/displacement) curves, but sufficed to say, my suppliers on a previous project had a wide range of attributes to hit which were precisely chosen for critical load, ride and handling characteristics by some very nerdy and clever chassis engineers (I can't include myself here )

Not only that, these parts are subject to tough component durability testing, including at different temperatures for thousands of hours.

Our Trophys have Cellasto front spring aids, which is a closed cell foam. This allows the spring aids to compress (rather than flow like rubber) and that has the added benefit of not trapping the damper rod. You don't want this added hysteresis (friction/stiction).

Add into this the effect on roll stiffness as well as the vertical stiffness mentioned above, and you can see how much consideration one needs to engineer these components.

The sort of driving we do in these hot hatches will constantly engage the spring aids/bump stops. We want our combined vertical systems to function perfectly with the motorsport grade dampers.

Ont that note, the Sach's hydraulic compression stop is almost certainly designed to engage only at the travels that the OEM spring aid gives.

So.... in my opinion, steer well clear from anything but Renault OEM spring aids/bump stops! I wouldn't trust that anything else had been engineered as thoroughly or as appropriately as an OEM part.

 

[hoolio]

James this is why I have suggested in my post that the Powerflex be used used in conjunction with the original bump stop that can be be removed from the gaiter. The yellow poweflex item can just be removed and the remaining bellows used simply as a sleeve. Hope that makes sense, bottle of wine now under the belt.

 

[photo_ed]

I can't directly, as I haven't tried it. If you're using them purely as a gaiter/dust tube then they're probably OK. But... I can lend some insight into development of 'bump stops' from some work a few years ago.

The primary function is load management into the body (in parallel to the spring), and with it the wheel displacement.

They're also known as spring aids, as they contribute to the effective spring rate of the car.

OEMs finely tune these for the following considerations:

• So the maximum combined load into the body is reached at the end of wheel travel (at zero speed). The unsprung mass will have been controlled (and damped) over the full wheel travel.
• So the wheel and tyre don't smash into the wheelarch
• The gap from the 'nose' of the spring aid to the bump cap of the damper (where the seal pack is). A gap allows only the main coil spring to contribute to the wheel rate (also know as the on centre wheel rate) before the spring aid is engaged at larger wheel travels
• The nose shape can be designed for a softer, less perceptible engagement point
• Density (more dense = less total travel = higher initial rates)
• Length - has to be tuned hand in hand with density to achieve point 1 and 2.
• 'Rate rings' can be added to a low density spring aid, to achieve soft initial engagement but quickly ramp up the rate if you have short wheel travel or awkward spring aid packaging.

I won't bore people with the different key areas on spring aid force/displacement (or even rate/displacement) curves, but sufficed to say, my suppliers on a previous project had a wide range of attributes to hit which were precisely chosen for critical load, ride and handling characteristics by some very nerdy and clever chassis engineers (I can't include myself here )

Not only that, these parts are subject to tough component durability testing, including at different temperatures for thousands of hours.

Our Trophys have Cellasto front spring aids, which is a closed cell foam. This allows the spring aids to compress (rather than flow like rubber) and that has the added benefit of not trapping the damper rod. You don't want this added hysteresis (friction/stiction).

Add into this the effect on roll stiffness as well as the vertical stiffness mentioned above, and you can see how much consideration one needs to engineer these components.

The sort of driving we do in these hot hatches will constantly engage the spring aids/bump stops. We want our combined vertical systems to function perfectly with the motorsport grade dampers.

Ont that note, the Sach's hydraulic compression stop is almost certainly designed to engage only at the travels that the OEM spring aid gives.

So.... in my opinion, steer well clear from anything but Renault OEM spring aids/bump stops! I wouldn't trust that anything else had been engineered as thoroughly or as appropriately as an OEM part.

Excellent and comprehensive post there James, thanks for sharing.

 

[James__H]

James this is why I have suggested in my post that the Powerflex be used used in conjunction with the original bump stop that can be be removed from the gaiter. The yellow poweflex item can just be removed and the remaining bellows used simply as a sleeve. Hope that makes sense, bottle of wine now under the belt.

Yep absolutely @hoolio ! I think I referenced your use as a gaiter only in the first paragraph but I appreciate this wasn't made clearly by myself Mine is split (held on with a cable tie!). Wine does sound good....

@photo_ed many thanks! Hopefully it made some sense.

 

[hoolio]

Yep absolutely @hoolio ! I think I referenced your use as a gaiter only in the first paragraph but I appreciate this wasn't made clearly by myself Mine is split (held on with a cable tie!). Wine does sound good....

@photo_ed many thanks! Hopefully it made some sense.

As Ed said. Yours was an excellent, considered post. Much better than anything I would have been capable of last night (or any time actually)

I just want people to think I was advocating using that huge piece of yellow polyurethane (?) As such I any of the bellows on the market would work as long as the diameter is similar. The Powerflex seem to be one of the few that have the option of enclosing the bottom.

 

[Patrick Bateman]

Used with the original top “bump stop” and secured over the top of the damper with the cable ties ( I had an idea to use double sided tape around the top of the damper also) I think the shaft should be kept pretty free of dust and any other crap.

Cheers all. This is what I'm going to do. Not sure of a better alternative, short of getting a scraper/wiper seal modification.

 

[Patrick Bateman]

Can anyone explain if I'm being a twat here...at a glance these will neither fit the original bump stop or even fit over the dampers.

Don't even look like they'd stretch.

 

[Patrick Bateman]

Do you mean these Patrick - these are the original ones -

Soufflet et butée amortisseur Sachs Clio 2 RS

Retrouvez tout pour l'entretien, la préparation et l'optimisation sur www.optimiz-access.fr Spécialiste pieces Renault Sport Alpine et RS PERFORMANCE

www.optimiz-access.fr

And looking at this...is this link for the gaiter only or the complete thing pictured including the bump stop?

Assuming they don't come in pairs?

Might be easier to just use all original parts and use a jubilee clip to secure the bottom of the rubber.

 

[photo_ed]

And looking at this...is this link for the gaiter only or the complete thing pictured including the bump stop?

Assuming they don't come in pairs?

Might be easier to just use all original parts and use a jubilee clip to secure the bottom of the rubber.

Mine arrived as per original - complete unit - bump stop & gaiter.
Price I think is for one if my memory serves me.

 

[Patrick Bateman]

Cheers, my original gaiters have definitely seen better days and it'll be good to have 2 sets of stops.

Have you tried securing the bottom of the gaiter to the shock at all?

 

[photo_ed]

Have you tried securing the bottom of the gaiter to the shock at all?

I haven't I'm afraid. When my dampers were swapped for the new set by Mick at Diamond, he was able to use my original bump stops and gaiters, but did note that they'd need doing 'next time around'. Thus I've invested in some new bumps and gaiters for the set of dampers I'm currently restoring in readiness for the next swap. I'm afraid they live in a different parts hoard to the one I have here at home (...dont ask! ) so I can't even trial fit them for you to see if they can be affixed, sorry.

 

[hoolio]

Can anyone explain if I'm being a twat here...at a glance these will neither fit the original bump stop or even fit over the dampers.

Don't even look like they'd stretch.

They will fit over the original Stop as it is fairly elastic and will stretch. See the picture below, it is just stretched over the top of one of my new ones as I didn’t want to take it apart. But you get the idea and I did manage it with an old stop I have ( as Ed now in a different “cache”)
I have to admit to not trying to fit it to an actual damper but would suggest it would stretch in the same way.

 

[Patrick Bateman]

Have I definitely got the right thing?

How on earth does this get over the shock?? I just played about with the gaiter and it has some stretch but not much.

Look at the difference in diameters.