Return to Website

NG Owners Club Forum

Welcome to the NG Owners Club Forum.

This forum is intended for members of the NGOC, if you are not a member
please consider joining  it only costs £15 a year...

The views & comments expressed on this forum are the views and comments of the person that posted them. The NG owners club does not take any responsibility for any views or comments made on the forum. The NG owners club reserves the right to remove any posting from the forum.

NG Owners Club Forum
Start a New Topic 
Author
Comment
View Entire Thread
Re: Re: Correct spring set up for TCV8

Martin,

Thanks for your posting... I already had 450 x 7's fitted and found thse to be too hard, so I went to the extreme and fitted some 375 X 7's with much better results although I'm finding it difficult to get the same ride height as the 450's.

I will try these throughout summer with varios damper settings to see if I can further improve the ride.

I was also going to get the fro weighed on a local weigh bridge to see if I can work something out if I can find the correct formula to use.

I'm runnng a v8 in mine, what do you have and where about are you?
Thanks

Richard.

Re: Re: Re: Correct spring set up for TCV8

Does it now ride too low? I noticed that the higher rate springs from Moss were only 6" - with the lower rate springs the weight of the car will compress them further. Perhaps 375 x 8"?

I am tempted to try 375 or 400 rather than the 425 I was thinking of at first.

I live near Brentwood (Essex). The car has an SD1 V8 & manual gearbox with a narrowed SD1 back axle. I currently have both front and rear dampers set to minimum, but the ride is a bit harsh if I go over anything much bigger than a toffee wrapper.
I have just spent 10 months rebuilding the thing as a v8 so there is plenty to think about - heat being a big issue.

Tyres are 185/70 15" - set to 23 psi (as a first guess). What tyres and pressures are you using?

All thoughts gratefully received!

Martin

Re: Re: Re: Re: Correct spring set up for TCV8

Hi Martin,
Your build sounds very familiar... I have just finished rebuilding another engine, but as your car, I have the same set up including the narrowed v8 axle.
The ride is better, but still taught. I think I may try some 8" springs some time but still not sure which rating! I live in Felixstowe, not too far from you but still quite a drive.... perhaps we could meet up some time a exchange ideas and experiences?
My mail address: - richwold@tiscali.co.uk
I'm riding 235/45 17" front and 255/45 17" rear. I have yet to play with the tyre pressures. Heat has not been a major problem but is always a concern on very hot day's however, the biggest challenge is getting all the air out of the system after any dismantling of the cooling system. If you mail me, I will forward some images.
Regards
Richard

Re: Re: Re: Re: Re: Correct spring set up for TCV8

My car is now using 250lb in springs at the front, much lower than my initial sums suggested, which I am happy with.

The problem now is the back - the narrowed Rover SD1 back axle is very heavy so the unsprung weight is a very high proportion of the rear end weight. This is not good for comfort. Maybe the RV8 springs or the Hoyle IRS (that will be just after I win the lottery..)

Re: Correct spring set up for TCV8

Hi Richard,
The simplest set of sums I could find were in the Haynes 'Race and Rally Car Source Book'. Without being able to weigh each corner of the car I had to use some guesstimation - the engine is behind the axle which throwa some of the weight to the rear - plus the operative moments about the wishbone pivot to the bottom damper mount and the bottom of the king pin are needed, also the combined weight of wheel and tyre will affect the best spring rate.
I was looking for a result that left the fillings in my teeth and didn't shake the car apart while driving over the rather rough roads in my area.
One really subjective test I used was 'If I push down carefully on the top of the radiator shroud does the car go down in the manner of a typical car?'.
At 375lbin the front suspension behaved as though it was almost rigid.
Tyres will be a factor in the choice - I have 185/70 15" which has some give in the sidewalls, currently at 23psi which feels about right (no science here!).


In the end my sums were some way out - the first springs would be good for a track - the set up was very solid, but not what I wanted. I am now using 250lb in x 7" springs. This means that the spring seat has to be wound some way up to get the right ride height, a higher rate spring would not compress so far.
There is a fair amount of experimentation involved in the combination of spring rates and damper settings (which I think I have at the third from lowest setting on mine).
I got the springs from Rally Design in Faversham who do a good mail order service, but there are quite a few suppliers.
One result of the settings I have is that I take speed bumps with care - the sump is quite low and my exhaust runs underneath the car.
Martin

Re: Correct spring set up for TCV8

All that happens when you wind the collar up on spring is to preload it.
wind it up an inch (250lbs per inch)wheel to spring movement), the force needed to move the spring needs to be at least 251lbs.
If you really need to work it all out put goulds maths into exel. It works...........

Re: Re: Correct spring set up for TCV8

Yes indeed, I don't know what the linearity of any change of spring rate will be as the spring is compressed - until the coils bind of course!The spring rate is set when it is manufactured, I had assumed the rate would remain around 250lbs for all practical purposes throughout the range of operating lengths of the spring.

The point of winding the spring seat up is to adjust the ride height on the car to make it level fore-and-aft, having no adjustment at the rear on my car.
This compensates for the spring compression due to the weight of the car. When I used higher rate springs the seat needed less adjustment because the spring was compressed to a lesser extent. Sorry I didn't explain that this was about ride height, not rate.