Wrong Damper Length or Wrong Mounting Point??

[Grim Reaper]

I have a question for the collective wisdom of Blatchat.

I am currently running Nitron dampers on my 2002 superlight, non watts link chassis, using 15" wheels.

If I have something near the recommended 75mm of space under the sump at the front, and wish to have 15mm of rake from front to rear, the rear dampers are set such that they will not extend much further (in fact they are pretty much at full extension as the tyres come off the ground almost straight away when the car is lifted on a jack)

Now, I am in the process of aquiring a set of 13" wheels, and having borrowed a set from another members and having grated the sump on the ground with them fitted on my car, I know I will have to raise the front to regain the 75mm clearance under the sump. But if I can not raise the rear any further as the dampers are already at full extension, how am I to retain the 15mm rake front to rear??

The question is, could I have the Nitron dampers fitted to the wrong mounting points on the DeDion tube? Is this the reason I have been suffering from severe understeer for the past 2 years or so? (thinking back it's probably since I raised the front to get more space under the sump to stop it hitting things in the road and found that if I raised the rear to try match it I could never quite get it high enough or it ended up too hard)

I have fitted them using the threaded bush below the tube (as per the build manual) but I am now considering the fact that I might have a set of dampers which are shorter than that which is required in order to use the lower mounts.

Just a quick measure of the dampers tonight (without removing the wheels) gives me a damper length of around 44cm with the car on the ground, and this will be with the damper at almost full extension as previously stated.

The fronts are at 34cm with the car on the ground, though they are not at full extension and will extend a little more when the car is jacked up enough to lift the tyres clear of the ground.

Reading through previous posts on the subject, I have found references to long Bilstein dampers and short Leda dampers, the longer ones seem to be required in order to use the lower mounting points and the shorter ones seem to be for the through the tube mountings.

Does anyone have the free length measurements of the short and long dampers that can be supplied for this car? Front and rear if there are differences at both ends?

Thanks in advance.

Grim.

[Peter Carmichael]

Nitrons are usually made to fit to the "through the tube" mounting, although the new generation de dion tubes don't allow for this.

[Ged]

Grim,

I've got the standard damper lengths for my '96 car, for fitting to the lower De-Dion mount.

 

Front

 

Open length eye to eye = 14” (narrow track)

Open length eye to eye = 15” (wide track)

Open length between spring pans = 7”

Metallastic bushes both ends ½” dia

Spring I.D. = 1.9”

Wire dia = 0.32”

Approx free length of spring = 7.25” (estimated, very little compression at fully open)

Note:- the spring length is for springs 9 years old, having done 23000 miles.

 

 

Rear

 

Rear dampers are the same for wide tack and narrow track.

Open length eye to eye = 18½” or 47cm

Open length between spring pans = 13”

Metallastic bushes both ends ½” dia

Spring I.D. = 2.25” (springs are standard progressive rate)

Wire dia = 0.375”

Approx free length of spring = 13” (estimated, no compression at fully open)

Note:- the spring length is for springs 9 years old, having done 23000 miles

 

I have a pair of standard MO Bilsteins if you want to do a comparison

 

[Jason Plato]

Ring Gary at Nitorn to check the dimensions - as Peter says , there are 2 lengths .

[Grim Reaper]

Ged, are these lengths for dampers that use the 'through the tube' mount or the 'welded on boss'?

Looks like I've got some bolts to order

[Ged]

The lower welded on boss

[rgrigsby]

Nitron will make up both types but it does sound like you have the through the dedion tube ones, tbh I think that would be the preferred mounting option given the problems people have had with the welded on bush. It's certainly how my Nitrons are mounted.

 

Rob G

www.SpeedySeven.com

[Mike Molloy]

I had a word with the chaps at Nitron about the damper lengths for their Caterham kit (developed in conjunction with that nice Mr Carmichael, apparently...)

He did mention that the rear damper was supposed to fit to the through-de-dion-tube fitting, but you can order with a 20mm extension to fit the standard lower mount.

I am afraid that playing with springs results in more questions than answers...

If I settle on a given chassis ride height (140mm front, +15mm rear) and wheel diameter (527mm front, 554mm rear), the damper extension in a steady state is fixed.

Question is, where do you want the damper rod to be in its travel range? If it is near full extension (as suggested by the original poster) then you have the advantage of lots of damped wheel travel before hitting the bump stop. However any body roll would cause the tyre to be lifted clean off the road (mental image of Pug 205 cornering tricycle stylee...)

Is there an optimum point? I guess stiff springs limit roll, so droop may not be much use?

 

If I was to fit Nitrons and use the through-de-dion-tube mounting, how does one attach to it? Just a long bolt and nyloc or is there an internal thread?

[Tom_C]

Roll will depend on ARB amongst other factors quite apart from spring rate.

 

And tricycle cornering is fun, but only with FWD I suspect. My clio does a great power off oversteer to get round tight corners.

 

 

Cheers

 

Tom

 

FH54WLX - only the car supports ManU, honest!

 

see here

[Shaun_E]

My Nitrons fit the under tube mounting - they were the same length as the Bilsteins that came off. I didn't notice an extension piece when I fitted them but that doesn't mean it isn't there 😳. Having read some of the stories regarding the under tube bush, I guess I should have gone for the shorter ones and used the through the tube mounting.

 

Yellow SL #32

[neil.cavanagh]

Dave (GrimR),

Sounds like you could have problems with your damper lenght as it is. The damper needs to be able to extend a bit as it is anyway. Otherwise when you go over a pothole or small depression in the road the wheel won't be abel to extend downwards, and so remain in contact with the ground...

 

anyway, I thought your understeer problems were due to the massive ballast on the left side on the car when I was in it... 😬 😬