I got some nice shiny Protechs from MNR recently and set about positioning the mounts at the weekend.

However the ride height is way too high using the brackets on my GTS de-dion axle. Not sure how GTS builders have gotten around this as my shocks are only one inch longer than GTS spec at 13" fully open.


rear shock position 1

Currently full droop is reached when the trailing arms contact the chassis rather than the shock fully extending, which is obviously no good.

So what I propose doing is lopping off the existing mounts on the de-dion and adding some new ones slightly further inboard and on the beam itself. This adds an angle to the shock. Anyone see a problem with this?


rear shock position 2

This should give me a decent ride height whist being able to use all of the shock travel - important when there's only 3" of it!

Early Mk/Ron champion de-dion allowed longer upper trailing arm bolt to permit mounting of the damper in single shear.

This is of course dependant on the location of your damper top mounts as well.


de dion

You have 3 options from the way I see it:

1. Get some shorter springs for your shocks. This will allow you to lower the ride height.

2. Get the correct length shocks (12"

3. Modify the axle.

Personally I would go for #1.




David

If there's space with the wheel why not add a bracket just outside the trailing arm bracket and use a common bolt to mount shock and trailing arm.

Thanks for the suggestions so far.

Mounting on the same bolt as the upper trailing arm is a reasonable suggestion, but I don't know if it buys me enough extra space. Unless, I'm getting something wrong in my thinking, which is a definite possibility.

Flak monkey, your photo is interesting (not least because it answers another question I had about the panhard rod).... That looks to be about the amount of droop I would have if I had 12" shocks, but I think the trailing arms need to be much more horizontal, even on full droop) to get a reasonable ride height at the back. My target for reasonable ride height is 100mm front, 125mm rear. How much do you have? Am I missing something?

Also, I only have 3" of shock travel so I need to be able to use it all. That rules out shorter springs, or using too much spring preload for that matter.

Mine is set to 125mm rear and 100mm front at the moment. This sees the trailing arms pointing very slightly down toward the back.

Those shocks are 12" as supplied by GTS.

Adam,

After buying a couple of second hand shocks that were the wrong size I assembled the rear end and measured, then ordered shocks to suit, iirc mine are at least an inch or two shorter than yours. I looked at swapping for shorter springs but there's not enough travel due to the shock body length, I also looked at moving the pickup on the axle aswell but with the brake caliper in position the options seemed limited. Changing the shocks for ones that actually fit is the best route imho as I've been there and done it. Protech may exchange your current shocks, even if you have to sell them on here or ebay you will loose little or no money.

Ned.

quote:

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Originally posted by flak monkey
Mine is set to 125mm rear and 100mm front at the moment. This sees the trailing arms pointing very slightly down toward the back.

Those shocks are 12" as supplied by GTS.

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They arent at as much of an angle as they look in that picture.

Once the car is down on the ground the trailing arms sit like this:




(Best pic i have, sorry)

Theres still a good amount of shock travel available, though How much I couldnt tell you for certain. Maybe 2".

There is no preload on the springs (175lb) to give 5" ride height.

David

Gts rear bulk-head is 1" taller than book.

quote:

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Originally posted by big_wasa
Gts rear bulk-head is 1" taller than book.

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quote:

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Originally posted by big_wasa
Gts rear bulk-head is 1" taller than book.

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Angling the shock reduces effective spring rate and damping action.

I have this problem with my chassis and a GTS axle, one possibility is to mount the damper on the inside of the top trailing arm bolt, either in single shear (not technicaly good, but M12 bolt is up to the job IMO) or adding some bracketry to put the bolt in double shear.

You also lose the benefit of having the shock mounting eyes the "proper" way for the axle (i.e. like the GTS design), but lots of locosts have live axles with the shocks mounted the other (book) way so it shouldn't cause problems.

quote:

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Originally posted by MikeRJ
Angling the shock reduces effective spring rate and damping action.

I have this problem with my chassis and a GTS axle, one possibility is to mount the damper on the inside of the top trailing arm bolt, either in single shear (not technicaly good, but M12 bolt is up to the job IMO) or adding some bracketry to put the bolt in double shear.

You also lose the benefit of having the shock mounting eyes the "proper" way for the axle (i.e. like the GTS design), but lots of locosts have live axles with the shocks mounted the other (book) way so it shouldn't cause problems.

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