Spax Dampers

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evilally
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Spax Dampers

Post by evilally »

I recently picked up a set of brand new gas filled Spax front dampers for a 405 on ebay for a tenner. Does anyone have any experience of these? What's the advantage of a gas filled damper versus oil filled? I was pondering replacing the front dampers, as I'm sure after 141k and 14 years they'll be a little tired. Would new springs be in order as well?
'96 405 1.6 GLX with 306 GTI engine on Cat cams @ 195bhp

'05 RenaultSport Clio 182 Cup, 102k

'97 406 1.9TD, 314k.
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Chris570
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Post by Chris570 »

I've run spax stuff on my AX and it made the car handle even better than before a HUGE improvement over OEM, question is though do you want your car more setup for track or road....
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evilally
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Post by evilally »

Sounds good, possibly a bargain for a tenner? While they are apparently 20% stiffer than OE, I don't think they are intended as a track orientated damper.

One thing I did notice about my old dampers......the piston would retract when left. Does that mean they're shagged?
'96 405 1.6 GLX with 306 GTI engine on Cat cams @ 195bhp

'05 RenaultSport Clio 182 Cup, 102k

'97 406 1.9TD, 314k.
patanga
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Post by patanga »

Hi evilally

Regards your question about the spax dampers being gas charged, they are still oil operated, but with the inclusion of a small nitrogen gas charge. The oil is still required to provide the damping control through the foot valve. Many O.E. shocks do not have the gas charge (probably more to do with cost, but in some rare instances the nitrogen charge has been known to be the cause of a symtpom known as gas thump, or an additional harshness.). O.E. design is usually all about ride comfort at a price, so plain oil shocks are usually the standard choice. In gas over oil dampers, the gas charge is injected during the build process to displace the air that would otherwise remain in the cavity at the top of the damper. The nitrogen charge is much less likely to mix with oil than the air and so your new dampers will suffer much less from the risk of cavitation or fade.

The reason the shaft in your original dampers drops when you let it go (obviously you have already taken them a part) is in part and most likely because they are the worn out original 'oil only' units. It is the gas charge that keeps the internals pressurised and hence the shaft pushed up. This is not a good or a bad thing it is simply a by product of the gas pressure.

Fresh 'oil only' dampers, out of the box, will have a good go at keeping the shaft where ever it is placed in its range of travel because the internal valving is fresh and restricting oil flow as designed, plus there is no real force acting on them. Further to this, if the bump valve coding is softer than the rebound then the shaft would likely drop due to gravity and time, if left to sit due to the lesser oil restriction in bump travel. This observation is of course only relevant when the damper is not fitted and becomes a mute point for both 'oil only' and 'gas over oil' dampers once on the car, as the springs are then what hold the vehicle's ride height.

At 141,000 (miles I presume) your dampers would be well and truely shagged. This would explain why the shaft would drop even more quickly than when it was new. You will find that worn internal components and contaminated, broken down oil will be the cause. In my experience, a good life for quality euro O.E. dampers is probably around 80 - 90k's and in Jap / Asian models (where lesser quality parts are often used) around 40 - 50k (i.e. miles).
Cheers
Ron
Last edited by patanga on 02 Mar 2011, 10:19, edited 7 times in total.
evilally
(Donor 2020)
Posts: 742
Joined: 17 Apr 2008, 22:39
Location: Clydebank, Near Glasgow.
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Post by evilally »

Thanks Patanga, a most useful post. Is it worth while fitting with new springs?
'96 405 1.6 GLX with 306 GTI engine on Cat cams @ 195bhp

'05 RenaultSport Clio 182 Cup, 102k

'97 406 1.9TD, 314k.
patanga
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Location: Australia
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springs

Post by patanga »

Hi evilally

Yes most definately. Coil springs carry weight over a camparatively small foot print when compared to torsion bar springs and leaf springs (I'm making he assumption of quality product, not cheap, poorly manufactured product being used). Because of this, coil springs are working harder in a relative sense. Metal fatigue in springs is a very real issue and you will most definately benefit by replacing them with a quality after market brand. I have found the O.E. Peugeot torsion bars to be quite dudrable, but then they are also doing a lot less work in the rear end.
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