Ride heights

[melly]

Just had new suspension put on my 1995 4ltr Chimaera (fully adjustable) could anyone tell me what the correct ride heights are for the car.

Thanks

[Dave N500 CHM]

I fitted Gaz shocks to mine last weekend and set them up about three threads from the bottom.
Haven't had the chance to get them all the same yet but when measured before and after I had :
Front near std was 15.5cm, now 13cm
Front off std was 14.5, now 13.2
Rear near was 17.5, now 13.9
Rear off std was 16.5, now 12.5

Its too low at the back and I want the same height all round so I'm going to try 14cm first.
Does look cool beng so low though. Will post some pics

[Dave N500 CHM]

http://good-times.webshots.com/photo/

http://good-times.webshots.com/photo/

Edited by Dave N500 CHM on Saturday 23 September 19:25

[GreenV8S]

Dave N500 CHM said:

Haven't had the chance to get them all the same yet but ...

When you say 'get them the same', don't be tempted to try to adjust the ride height at each corner by moving individual spring seats. You want to set the spring seat heights to the same position on the left and right sides of the car.

[adam459]

the lower the better.

[GreenV8S]

I don't agree with 'the lower the better' for handling, although I agree it does look nice and agressive lower. After you've chosen the ride heights, remember to get the geometry reset.

[trackcar]

yeah the "lower the better" approach works really well right up to the point you actually want to drive the thing. stand back and admire, that's all it will be good for.

[dc53]

adam459 said:

the lower the better.

WOW! your car is really nice, and i agree about "the lower the better", but only look's wise, i think it makes the cars lines look better and more of a cerbera's 'IMO'.But when driving it wouldnt be know-where near as good handling wise as a well set up chim.

[Dave N500 CHM]

GreenV8S said:

Dave N500 CHM said:

Haven't had the chance to get them all the same yet but ...

When you say 'get them the same', don't be tempted to try to adjust the ride height at each corner by moving individual spring seats. You want to set the spring seat heights to the same position on the left and right sides of the car.

DOH, yes, that’s exactly what I was thinking in what can only be described as a moment of madness!
Really need to get the car on a flat surface, the wobbly driveway the pics were taken on isn't ideal either.

[pupp]

Hmmm....can I just understand what is being said here? When I played with mine, the only way to get the ride heights I wanted was to end up with different platform settings at each corner. I went pretty low and I like it, but do also use marginally lower profile tyres on the front too

[GreenV8S]

pupp said:

When I played with mine, the only way to get the ride heights I wanted was to end up with different platform settings at each corner.

You've almost certainly messed the corner weights up. Unless your chassis is bent, the corner weights will be more or less spot on with left and right spring seats set to the same height. The further you go away from this, the further out your corner weights will be. The only time you want unequal spring seats is when the center of gravity is a long way from the center line of the car. In production roadgoing TVRs, it isn't.

[Dave N500 CHM]

GreenV8S said:

pupp said:

When I played with mine, the only way to get the ride heights I wanted was to end up with different platform settings at each corner.

You've almost certainly messed the corner weights up. Unless your chassis is bent, the corner weights will be more or less spot on with left and right spring seats set to the same height. The further you go away from this, the further out your corner weights will be. The only time you want unequal spring seats is when the center of gravity is a long way from the center line of the car. In production roadgoing TVRs, it isn't.

This is why I want the same ride height all round. Does anybody know the corner weights on a Chim?

[Colin L]

Yeah it looks good, but its safer for us all if you go spend some money and have her set up correctly.

With the back end higher than the front it could led to some real handling problems, also if you are unluckly to have an accident, will your insurance pay out because you set up the car?????

Its a small question you may want to ask yourself, there are some PHer's who know how to set up a car correctly and then the DIY ones and they are ones who will run into trouble or out of road..

Only my thoughts, but am sure quite a few agree.
Colin L

[GreenV8S]

Dave N500 CHM said:

This is why I want the same ride height all round. Does anybody know the corner weights on a Chim?

It's within a few percent of 50:50 front:rear and left:right. In order to get the ride height right you need to have a perfectly flat surface and measure the chassis height very carefully, you need to allow for stiction and so on. Really a waste of time since the car is symmetrical, just make sure left and right spring seats are set the same and the corner weights WILL be right. If you set them differently you can be pretty certain the corner weights are wrong. Do not under any circumstances try to set the ride height by eye, the body is very assymetrical, varies from car to car and even moves around on its own as the body heats up and cools down and flexes. You also need a surface that is flat to far better accuracy than you can see with the naked eye.

[pupp]

GreenV8S said:

pupp said:

When I played with mine, the only way to get the ride heights I wanted was to end up with different platform settings at each corner.

You've almost certainly messed the corner weights up. Unless your chassis is bent, the corner weights will be more or less spot on with left and right spring seats set to the same height. The further you go away from this, the further out your corner weights will be. The only time you want unequal spring seats is when the center of gravity is a long way from the center line of the car. In production roadgoing TVRs, it isn't.

I've messed them up? How... I've not installed a ton of brick rubble anywhere And is there any allowance for 16st of driver in this all corners are equal theory?

[GreenV8S]

pupp said:

I've messed them up? How... I've not installed a ton of brick rubble anywhere And is there any allowance for 16st of driver in this all corners are equal theory?

Corner weighting is not about moving the center of gravity, it is about spreading the weight evenly between the wheels so that there is no net torsional preload on the chassis. Adding a hefty driver will move the CoG sideways slightly but only slightly (perhaps an inch), and the torsional preload this introduces is extremely small. It'll cause a very small amount of roll too, probably the equivalent of about 2% of the static deflection i.e. not enough to be bothered about unless you are racing and have optimised everything else and are scrabbling for every thousandth of a second. In practical terms, it is so hard to get the weight distribution better than equal spring heights (side-to-side) give you, and so easy to get it a lot worse, that it just isn't a sensible thing to do.

[pupp]

GreenV8S said:

pupp said:

I've messed them up? How... I've not installed a ton of brick rubble anywhere And is there any allowance for 16st of driver in this all corners are equal theory?

Corner weighting is not about moving the center of gravity, it is about spreading the weight evenly between the wheels so that there is no net torsional preload on the chassis. Adding a hefty driver will move the CoG sideways slightly but only slightly (perhaps an inch), and the torsional preload this introduces is extremely small. It'll cause a very small amount of roll too, probably the equivalent of about 2% of the static deflection i.e. not enough to be bothered about unless you are racing and have optimised everything else and are scrabbling for every thousandth of a second. In practical terms, it is so hard to get the weight distribution better than equal spring heights (side-to-side) give you, and so easy to get it a lot worse, that it just isn't a sensible thing to do.

Ok, so all else being equal and the chassis not being obviously bent, when faced with significantly different chassis rail heights over a level surface (that vary even further with and without 'driver' of equivalent weight installed), how would you suggest someone proceeds, other than by platform heights? Might be different if there was separate height adjustment built in a la Radical but there isn't and setting equal platforms was clearly going to result in an unacceptable attitude (although that's exactley where I started). FWIW, everyone who goes in the car remarks on how well it handles...

[Dave N500 CHM]

GreenV8S said:

Dave N500 CHM said:

This is why I want the same ride height all round. Does anybody know the corner weights on a Chim?

It's within a few percent of 50:50 front:rear and left:right. In order to get the ride height right you need to have a perfectly flat surface and measure the chassis height very carefully, you need to allow for stiction and so on. Really a waste of time since the car is symmetrical, just make sure left and right spring seats are set the same and the corner weights WILL be right. If you set them differently you can be pretty certain the corner weights are wrong. Do not under any circumstances try to set the ride height by eye, the body is very assymetrical, varies from car to car and even moves around on its own as the body heats up and cools down and flexes. You also need a surface that is flat to far better accuracy than you can see with the naked eye.

Thanks Peter. I thought the weights were 50:50 all round just wanted to check.
That's what I love about TVR's, they are bloody mid-engined!!!

[seasider]

Mine is lower front than rear

[GreenV8S]

pupp said:

Ok, so all else being equal and the chassis not being obviously bent, when faced with significantly different chassis rail heights over a level surface (that vary even further with and without 'driver' of equivalent weight installed), how would you suggest someone proceeds, other than by platform heights? Might be different if there was separate height adjustment built in a la Radical but there isn't and setting equal platforms was clearly going to result in an unacceptable attitude (although that's exactley where I started). FWIW, everyone who goes in the car remarks on how well it handles...

I would look for reasons for the chassis rails being at different heights. Are the springs all the same length (i.e. left versus right) at the normal ride height? If not, perhaps one or more springs has sagged or they are not actually the same spec on both sides. If the spring lengths are the same and the spring seat positions are the same then the total damper lengths i.e. between the end fittings should be the same. If they are the same but the chassis is not at the same height on both sides then something is bent, twisted or deformed. I'd measure everything I can see until I found where the difference was. The chassis is not absolutely rigid but is pretty stiff so if the spring lengths are different at one end, it may be that the assymetry is at the othe end. In this case you'd find diagonally opposite springs carrying more than their fair share - in other words the corner weights are out. For this to occur with the spring seats all level implies either the ground is not flat or something is bent. You can find where the problem is by jacking up one end of the car under the middle of the chassis so it is free to pivot in roll, and seeing if the other end then fits square. See if either of the anti-roll bars have any load on when the car is flat. See if any of the bushes are collapsing, especially the damper mounting bushes. It's a problem somewhere, and you need to fix it, rather than counteract it by offsetting the spring seats.

The only time you want the spring seats set unevenly side/side is when the weight is a long way off the center line. On a production roadgoing TVR, it isn't.