Suspension motion ratio and corner weights T350

[Hedgetrimmer]

Suspension set up seems to be a hot topic at the moment. I have been talking to Simon at Cornering Force to see what he would recommend and he has asked for the following info:

1. Suspension motion ratios. Ie the rate the wheel moves relative to the spring.
2. Typical weight distribution front to back.

Can anyone shed light?

Thanks

[steveT350C]

quick google suggests near 50:50 weight distribution.. Not sure how accurate you want.

http://en.m.wikipedia.org/wiki/TVR_Tamora

Quote from TVR car club here, http://www.tvr-car-club.co.uk/about_tvr.asp

"Throughout all the changes, Trevor's basic concept of fitting a GRP body to a multi-tubular chassis with front engine and rear wheel drive, with particular attention being paid to power/weight ratios, has produced ever more exciting cars for the enthusiast. The aim is to produce a lightweight car with plenty of power and torque, combined with a front engined rear wheel drive layout to give the maximum pleasure for the enthusiastic driver. The engine is set as far back as possible in the front to give the car a near 50/50 weight distribution. Current models weigh about the same as a small saloon but with 3.5 to 5 times as much power dependent on model."

Suspension motion is bit beyond me and google. Just came up with this thread.

Eta, the T cars could be considered mid-engined....

Edited by steveT350C on Tuesday 7th October 16:42

[Hedgetrimmer]

Thanks Steve. The weight distribution just needs to be close to reality given that cars will vary in spec.

The motion ratio is simply the ratio of how far a wheel moves relative to the spring. Ie a wheel might move up by 10cm yet the spring may only shorten in length by 8cm as the spring is further down the suspension arm to the point of axis. Simples!

[K4TRV]

Real world Tamora - 2002 with 4.3 TVR Power engine and internal roll over bar.

Total weight without driver 1128Kgs. Corner weighted (with driver) each year, approx 51% front & 49% rear.

Suspension motion, why? Have you std or aftermarket dampers/springs?

You need a Suspension specialist - but one who has some knowledge of TVRs, in my very humble opinion.

There are a few around and I use Neil Garner, N Wilts?

T

[ShiDevil]

Centre of Gravity both Suspension Specialists, that's all they do and knowledge of TVR's

[Hedgetrimmer]

I am looking to replace the Harvey bailey dampers with Bilsteins or go for Nitrons valve'd for road use. However I am concerned that the Nitrons springs are too stiff at 400 and 325. Ohlins can be spec'd with 325 and 250 and standard springs are 200 and 225 (rear tuscan 2).

A chassis engineer is assessing the spring rates for me based on the weight of the car and the spring rate that the wheels see. I know many people are very happy with Nitrons an others find the springs too firm. I prefer a supple ride but don't want to bottom out on soft springs and therefore I am just want to do a bit of research first.

Edited by Hedgetrimmer on Tuesday 7th October 21:04

[K4TRV]

Hedgetrimmer said:

I am looking to replace the Harvey bailey dampers with Bilsteins or go for Nitrons valve'd for road use. However I am concerned that the Nitrons springs are too stiff at 400 and 325. Ohlins can be spec'd with 325 and 250 and standard springs are 200 and 225 (rear tuscan 2).

A chassis engineering is assessing the spring rates for me based on the weight of the car and the spring rate that the wheels see. I know many people are very happy with Nitrons an others find the springs too firm. I prefer a supple ride but don't want to bottom out on soft springs and therefore I am just want to do a bit of research first.

Horses for courses. My Tam's set up for Sprinting/speed hill climbing. However, oup norff/Derbtshire, Mr Joolz Lane; [e-mail] (spitfire4v8 on here?) has a wealth of experience.

if you are truly seeking the "knowledge" he would be my first choice, that is not just Sport set ups but subtle road versions too - give him your requirements??

With respect there's only so much you can do with our Tam's suspension. Many have ended up with quite awful solutions, go an speak to some TVR experts first, preferably Joolz (I'm just a fan of his, no other connection!!)

Good luck.

T

[Hedgetrimmer]

I am talking to Simon at Cornering Force in Harrogate who has rebuilt dampers for me in the past. As you say horses for courses but the motion ratio will help before wasting money on trying to compensate for too stiff a set of springs if I go down the standard rate.

[m4tti]

Hedgetrimmer said:

Suspension set up seems to be a hot topic at the moment. I have been talking to Simon at Cornering Force to see what he would recommend and he has asked for the following info:

1. Suspension motion ratios. Ie the rate the wheel moves relative to the spring.
2. Typical weight distribution front to back.

Can anyone shed light?

Thanks

Wouldn't it ultimately depend on the spring used as to how far the wheel can travel vertically. Rock hard springs result in little travel.

Why doesnt he measure it himself before and after.

[Hedgetrimmer]

m4tti said:

Wouldn't it ultimately depend on the spring used as to how far the wheel can travel vertically. Rock hard springs result in little travel.

Why doesnt he measure it himself before and after.

The ratio doesn't change as the wheel and spring should move at the same ratio. Ie the suspension arms will still follow the same arc. A stiffer spring will simply reduce the ability of the wheel to move. Ie the spring compresses less and the wheel moves a smaller distance.

It is useful to know the ratio in choosing the spring rate as a ratio closer to one means more force is required to compress the spring for a given wheel movement. Therefore a softer spring can be used. Dampers also play a part obviously in reducing the springs ability to move.

[m4tti]

But if there's a mathematical formula to calculate it and it isn't affected by variables such as spring stiffness why doesn't he calculate it taking the car as a blank canvas.

[plasticman]

[Hedgetrimmer]

m4tti said:

But if there's a mathematical formula to calculate it and it isn't affected by variables such as spring stiffness why doesn't he calculate it taking the car as a blank canvas.

He is 100 miles away and I haven't got the time to mess about going back and forth. I was hoping that someone might know the motion ratio anyway which would save the hassle. I could probably do it myself by measuring the spring length for a given wheel movement.

[Hedgetrimmer]

plasticman said:

Perfect! That'll do.

[plasticman]

That read out was from a tamora with standard suspension and was not in any way set up before I measured the corner weights . I could not believe how good it was !
The wheel to suspension movement is not a constant ratio but tring to get it closer definately helps.

[Sevenman]

Hedgetrimmer said:

Suspension set up seems to be a hot topic at the moment. I have been talking to Simon at Cornering Force to see what he would recommend and he has asked for the following info:

1. Suspension motion ratios. Ie the rate the wheel moves relative to the spring.
2. Typical weight distribution front to back.

Can anyone shed light?

Thanks

The motion ratios are on my list of things to find out as well. When combined with the corner weights that should give a lot of information on why different spring rates being used.

My Tamora (with rebuilt GGPs) is on 400 lb/in front / 375 rear. I found 325 rear too soft. These are dramatically different to what I understand were stock spring rates.

Having seen how little rear damper travel is available on my car before it starts squashing the bump stops the rear suspension design seems to be 'interesting'. Front is ok, it doesn't use all the available travel. And that is with what I think is a fairly high ride height for a Tam.

From my blog post on a visit to Center Gravity - http://www.sevenman.co.uk/?p=444

My Blog said:

Of concern was the rear damper travel when the suspension was laden. In terms of piston travel before the bump stop (which is 5cm and quite soft) there was only 15mm on the driver’s side and 20mm on the passenger side, and the piston was shiny, so that travel is being used. The front suspension had much more piston visible, and it was clear that it was not reaching the bump stop as there was a short dirty section of piston.

[Cornering Force]

Hi

The idea behind this original question was to get the info needed to take a view on the apparently quite large range in spring rates that are being sold with aftermarket dampers.

You're quite right that if we get the car in we can get the motion ratio empirically but i thought somebody on here may have done that already - hence the question. If we know the corner weight (derived from the total weight and front to rear split) and the motion ratio then we can specifiy a spring rate for the car reasonably well (depending on its use etc etc).

Just a thought to save some time and customer's money :-)

cheers

Simon

[SergSC]

This looks helpful
http://eibach.com/america/en/motorsport/products/s...

[Watersong]

Hedgetrimmer, Your question is certainly one that I have never heard asked for before and looking through the previous comments it would appear not a lot of other people have either, but may I suggest maybe contacting the original suspension supplier for the info. I've found a lot of companies are willing to help enthusiasts like us, the problem however getting to talk to the right person to start with maybe your biggest problem. Good Luck

[Watersong]

Hedgetrimmer, Your question is certainly one that I have never heard asked for before and looking through the previous comments it would appear not a lot of other people have either, but may I suggest maybe contacting the original suspension supplier for the info. I've found a lot of companies are willing to help enthusiasts like us, the problem however getting to talk to the right person to start with maybe your biggest problem. Good Luck