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TR4 - shortening the front springs


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Hi everyone.

 

I need to get the bump stop gap at the front of my ’62 TR4 up from their 12mm to 22mm (an increase of 10mm). So I think I have a couple of options. (Some of you will at this stage be asking why the hell does he want to do that – and for you I have added an explanation later on.)

 

Anyway – back to my options and call for advice, which hopefully will enable me to make a decision as to which option looks to be easiest.

 

Option 1 - Grind off 5mm from both ends of the spring.

 

Has anyone done this and have any pointers?

 

Option 2 - I've seen it said that you can reverse the lower wishbone arms (to lower the front). But I have never read a practical account of it being done. So again - has anyone actually done this and if so are there any snags to be aware of?

 

Re Option 2, I have scaled off the WM drawing and reckon that this would effectively increase the bump stop gap by about 16mm. Since I only want a 10mm increase I could then add a spacer of 6mm thickness to the spring.

 

OK – that’s my question asked!

 

…………………………………………………………………………………….

 

No need to read on unless your inquisitiveness has got the better of you.

 

The reason for wanting to do this………..

 

Having restored the car using Revington's 450 lbs front springs (and 160lb rear leafs) I find I'm low on “rebound distance". That is to say, the static distance between the (front) chassis bump rubber and the underside of the lower wishbone (where it impacts) is only about 12mm. Now, i have never seen this clearance stated but 12mm seems very small to me, and scaling off the WM drawing suggests something like 22 mm would be about right.

 

By my reckoning 22mm would equate to a maximum rebound at the wheel (again, from the static position) of about 36mm. That seems about right to me and would in fact be similar to what I now get at the rear (again, after some lowering and fettling).

 

Thanks in anticipation

Norman

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I needed to shorten the front springs on the CV8 (ride height was way too high), took them to a coil spring expert where they shortened and 'scragged' the springs (don't ask!). Not expensive, about €100 for 4 springs, peace of mind because it was done by the people who knew what they are doing.

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Thank you Justin - so scragging is the answer. You learn something new every day!

Norman

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Option 2 - I've seen it said that you can reverse the lower wishbone arms (to lower the front). But I have never read a practical account of it being done. So again - has anyone actually done this and if so are there any snags to be aware of?

 

Re Option 2, I have scaled off the WM drawing and reckon that this would effectively increase the bump stop gap by about 16mm. Since I only want a 10mm increase I could then add a spacer of 6mm thickness to the spring.

 

It's fairly common practise among the Reliant Scimitar fraternity to flip the wishbones over then bolt the lower shock/spring mount to the underside of the wishbones to lower cars at the front. It's TR front suspension on Scimitar Coupés and GTE's of course.

 

I haven't tried this on my Scim or TR, as I didn't need to lower either. I've tried searching Scimitar Web but couldn't find any definitive advice. If you're seriously thinking of going down this route, you could try joining at http://www.scimitarweb.co.uk/sgwrs/(don't need to be a club member to join) and I'm sure someone will give you an answer.

 

 

Nigel

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Well thanks for all that guys.

 

Whilst I'd like to try a little sgragging I'm leaning towards doing the obvious and talk to Revingtons first. I'm sure I ran a cursory rule over the springs, but an accurate and recorded measurement "no"!

 

Then, if i can change over the wishbones in a day, I'll be happy. I seem to remember struggling during the restoration and thinking what a bl###y long spring which was not helped with two 5mm thick SuperPolySomething spacers.

 

Just looked at the original springs (shorter but with the ali spacer) and I noted that the end coils are already ground to get them seating square, and I have my doubts if another 5mm wouldn't leave them a little thin.

 

Thanks for bringing a little clarity guys

 

Norman

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Well, for the benefit of those who may search the subject in the future I have two things that I must add.....

 

One - Do the sensible thing and contact the supplier :huh:. Neil Revington said (without hesitation or repetition)....

.......He would not add the 5mm extra thick isolators with his Red stripe 450 lb springs ("unless I really wanted to add more ground clearance" - which I don't).

.......He reckons the velocity ratio, wheel to shocks is a little above 2:1 (More than the 1.7 I had thought it was).

 

So, if I replace the (two per spring) +5 mm extra thick PolyWhatNots with the standard ones I will get an extra 10mm clearance at the bump stop and therefore and I should be getting about 40mm+ rebound at the wheel - QED.

 

Two - I realise I was incorrect in thinking that reversing the wishbones would have the same effect. Whilst it will lower the ground clearance it doesn't increase the final rebound bump stop clearance. My muddled thinking there!

 

Anyway, although I have yet to remove the +5mm isolators I'm now confident it will regain my rebound clearance.

Thanks for your contributions guys.

Regards

Norman

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