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Author: Subject: Static ride height question
thelynxeffect

posted on 9/9/18 at 07:22 PM Reply With Quote
Static ride height question

So amongst other this today I set my static ride height , the only question I have is should I accommodate sag of the driver in the base settings I.e. Should the rear RHS be set slightly higher than the left to take the driver sag into account? I get about 8mm of sag on the right and about half that on the left when I climb in.


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gremlin1234

posted on 9/9/18 at 09:33 PM Reply With Quote
you should set ride height (and corner weights...) to as close as 'normal running condition'
ie if just you driving
then weight in just the drivers seat,
but if you will normally have a passenger, weights in both seats

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thelynxeffect

posted on 10/9/18 at 05:08 AM Reply With Quote
What sort of corner (front/rear) weight ratio should I be aiming for? Just road driving.
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907

posted on 10/9/18 at 06:15 AM Reply With Quote
You can only change front to back by moving stuff, i.e. mounting engine further back or forwards.
In reality this can only be done in the design stage.

Might be able to move the battery but thats about it.



The main thing is with corner weighting is to have equal grip on all 4 tyres.

Think of sitting on a dining chair, weight on all 4 legs, this is a correctly set up car.

Now chop 15mm off one leg. Chair now sits with weight on just 2 legs and wobbles.



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thelynxeffect

posted on 10/9/18 at 09:54 AM Reply With Quote
But using your analogy, if I were to chop an inch of the front two legs, the CofG of me on the chair would shift forward and thus the weight on the front legs would be greater. Hence I can adjust front/rear weighting by modifying ride height?
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JimSpencer

posted on 10/9/18 at 10:42 AM Reply With Quote
quote:
Originally posted by thelynxeffect
But using your analogy, if I were to chop an inch of the front two legs, the CofG of me on the chair would shift forward and thus the weight on the front legs would be greater. Hence I can adjust front/rear weighting by modifying ride height?


Theoretically you are correct - but it'd be so marginal as to make little/no noticeable difference.
The weight bias front to rear is determined by the location of the major items in the car - you would move considerably more weight from the rear to the front my moving your seat forward than by adjusting the ride height at the rear


Back to your original question:-

In short;- Yes the off side rear would normally have a higher static, unloaded, ride height to allow for the driver.
Assuming
The car is set up to be used mainly with just the driver in it.

How much will depend on the corner weight settings, but your measurement giving a 4mm net difference could be possible.

A couple of hints:-
Make sure the car still has some rake in it once you're in it - circa 10mm ish higher at the rear than the front.
Plus
If you haven't got the kit to get the car aligned and corner weighted prior to using it in anger - go to somebody who has, it transforms how these cars feel to drive.

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thelynxeffect

posted on 10/9/18 at 11:19 AM Reply With Quote
Thanks for the replies guys, all taken on board, we have corner scales at work so iíll give it a go, also have a wheel alignment rig so will have a play with that, if all else fails iíll go to the pros.

[Edited on 10/9/18 by thelynxeffect]

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40inches

posted on 10/9/18 at 12:16 PM Reply With Quote
I used this Exel sheet to do the calculation. https://robrobinette.com/corner_weight.htm
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ianhurley20

posted on 10/9/18 at 04:19 PM Reply With Quote
On my car I set it all up so the gound clearances were as specified. On the road hit the brakes and front left locks first. Increase the preload on the rear right and try again. Once I got to the right locking I backed off a bit and then it could be either wheel first. Ok this is not computer corner weighting but it is how I got my car balanced for my weight in the drivers seat. I do have passengers but never push the car as much then so its fine for me - if you always have two then thats the way to test. - OR - get it set up on some super dooper computer scale things. But then again this is a Locost forum.





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Toys2

posted on 10/9/18 at 10:32 PM Reply With Quote
quote:
Originally posted by JimSpencer
quote:
Originally posted by thelynxeffect
But using your analogy, if I were to chop an inch of the front two legs, the CofG of me on the chair would shift forward and thus the weight on the front legs would be greater. Hence I can adjust front/rear weighting by modifying ride height?


Theoretically you are correct - but it'd be so marginal as to make little/no noticeable difference.
The weight bias front to rear is determined by the location of the major items in the car - you would move considerably more weight from the rear to the front my moving your seat forward than by adjusting the ride height at the rear


Back to your original question:-

In short;- Yes the off side rear would normally have a higher static, unloaded, ride height to allow for the driver.
Assuming
The car is set up to be used mainly with just the driver in it.

How much will depend on the corner weight settings, but your measurement giving a 4mm net difference could be possible.

A couple of hints:-
Make sure the car still has some rake in it once you're in it - circa 10mm ish higher at the rear than the front.
Plus
If you haven't got the kit to get the car aligned and corner weighted prior to using it in anger - go to somebody who has, it transforms how these cars feel to drive.


That's interesting can you explain the benefits of rake? Thanks in advance

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JimSpencer

posted on 11/9/18 at 08:45 AM Reply With Quote
quote:
That's interesting can you explain the benefits of rake? Thanks in advance



Rake is a tricky one to explain in words (easier to demonstrate!) but i'll have a bash..

Firstly there's the practical side of things - Seven's are normally softer sprung at the rear than the front, so you need more suspension travel at the rear to avoid bottoming out on the bump stops.

But in the main itís the effect it should have on handling (assuming the car's set-up is in the ballpark)

Rake changes how the car applies its weight to the front and how fast weight transfer happens when we're braking and then turning in.

More rake will increase the static weight on the front and add steering, less rake the opposite - but having rake in the car will significantly decrease the time it takes to transfer that weight when we brake and try and turn in - or worse still pile into a fast corner with no brake, and just a lift for example.

So generally speaking, all other things being equal etc etc.. a car thatís nose up will tend to understeer and go from understeer to oversteer quite suddenly, with some rake in it itíll be the opposite..

The additional benefit is > set it up so it handles right with some static rake then you should have a car thatís easily adjustable with minimal inputs.

I.e. Ė when I was sprinting my Striker, we could alter it from a touch of understeer to a touch of oversteer by adding a millimetre or two to the rake.

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coyoteboy

posted on 11/9/18 at 12:23 PM Reply With Quote
quote:
Originally posted by JimSpencer
quote:
That's interesting can you explain the benefits of rake? Thanks in advance

I.e. Ė when I was sprinting my Striker, we could alter it from a touch of understeer to a touch of oversteer by adding a millimetre or two to the rake.


I'd be utterly staggered if a mm or two made that much difference!?





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JimSpencer

posted on 11/9/18 at 06:27 PM Reply With Quote
Hi

Surprising in a way isn't it?
But when the car's dialled (and it was, in 2011 I won the Midland Speed champs with it and it's still got a couple of the class records form then.) it's surprising how small a change you need to get a noticeable difference, not much mind but you could tell the difference..
My brother and I spent a LOT of time getting the setup right
We didn't have the bhp to do it any other way

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Toys2

posted on 11/9/18 at 06:41 PM Reply With Quote
quote:
Originally posted by JimSpencer
quote:
That's interesting can you explain the benefits of rake? Thanks in advance



Rake is a tricky one to explain in words (easier to demonstrate!) but i'll have a bash..

Firstly there's the practical side of things - Seven's are normally softer sprung at the rear than the front, so you need more suspension travel at the rear to avoid bottoming out on the bump stops.

But in the main itís the effect it should have on handling (assuming the car's set-up is in the ballpark)

Rake changes how the car applies its weight to the front and how fast weight transfer happens when we're braking and then turning in.

More rake will increase the static weight on the front and add steering, less rake the opposite - but having rake in the car will significantly decrease the time it takes to transfer that weight when we brake and try and turn in - or worse still pile into a fast corner with no brake, and just a lift for example.

So generally speaking, all other things being equal etc etc.. a car thatís nose up will tend to understeer and go from understeer to oversteer quite suddenly, with some rake in it itíll be the opposite..

The additional benefit is > set it up so it handles right with some static rake then you should have a car thatís easily adjustable with minimal inputs.

I.e. Ė when I was sprinting my Striker, we could alter it from a touch of understeer to a touch of oversteer by adding a millimetre or two to the rake.


That's brilliant, thank you for the time taken to explain

I bought a used Striker a couple of years back, the suspension set up "as bought" was from the school of, whack up the damping rate up to the point that the dampers were very stiff, 'cause a stiff car handles, yeah?
It was skittish and uncomfortable. I softened the rear considerably, the front rate was already near minimum, the car handled so much better. Though only used on the road
It was only when looking back at some photos, that I realised that the front was about 10-15mm higher than the rear. It's SORNed at the moment, so I haven't had a chance to test it with revised ride height

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JimSpencer

posted on 12/9/18 at 07:33 AM Reply With Quote
quote:
I bought a used Striker a couple of years back, the suspension set up "as bought" was from the school of, whack up the damping rate up to the point that the dampers were very stiff, 'cause a stiff car handles, yeah?
It was skittish and uncomfortable. I softened the rear considerably, the front rate was already near minimum, the car handled so much better.
It was only when looking back at some photos, that I realised that the front was about 10-15mm higher than the rear. It's SORNed at the moment, so I haven't had a chance to test it with revised ride height



Ok so first off you need to fix this bit:-

quote:
Though only used on the road


Strikers are at home on a track.. IMHO best £ for £ trackday car you'll come across, I'm probably a bit biased but don't reckon I'm far off if I am..

Mine (it's a Mk3 BTW) was effectively built 3 times, first time built as a road car with a crossflow/4spd in it, started competing in clubby hillclimbs locally, and after a few seasons rebuilt it to a 4AGE/5spd and went down the bullet hard route, and it was quicker but not right, too skittish and didn't inspire confidence. So stripped it back to a bare chassis, had a full cage added, dry sumped, flat floor, race tank etc - in short more "Race car that happened to be road legal, than road car that you could track" also added a front ARB, protech's valved for the car, much softer springs and decamped to various tracks for around 3 days in total and dialled it in.

It's ended up at circa 20% stiffer than stock (250/200 IIRC) , quite stiff front ARB though and it's lovely to drive, you can alter its stance mid corner as you wish, doesn't bite if it does let go etc, very confidence inspiring too.

Currently it only sees the odd track day (running an old single seater instead.) but it's not slow when it does.


Loooking at yours you've got a front ARB which is a good start, if it's still got the old shocks on it worth investing in good ones valved for the car (Protech's from procomp if I was to recommend) adjust the set up - and get it out there and have a bash, some good venues available to you to have a play!

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