car setup & weight adjustment

[pulsarboby]

will be setting up my suspension within the next month, but i just wondered if anyone knows a rough guide to weight (driver weight lol)

may sound silly but theres an immense amount of weight plonked in the driver seat, which has got to affect the way the suspension etc is setup!

eg im 17 1/2 stone (yeah i know fat b@stard, before you's all start:lol: ) but would i adjust rebound, height, damping or camber or all of them? and would that be on o/s front shock only or rear aswell on driver side?
obviously the suspension must be adjusted on one side more than the other to compensate for driver weight or the car will not handle correctly!

i have only ever done this to a bike before but thats relatively easy compared to car. i wondered if there was some kind of set formulae as a rough guide to driver weight.>suspension adjustment to o/s?

 

[Odin]

you should search for some of Jim's posts, He can talk for England about susp settings :shock: :lol: :lol: :lol: :lol: .




Rob

 

[pulsarboby]

i have rob, but tbh a lot of it goes right over my head lol
and even then i cant find anything at all regarding taking driver weight into consideration:sad: i dont really want to take car in somewhere to have setup (not that im being a tightass) i would rather pay someone to show me how to do it correctly, then i can make certain adjustments at different tracks myself so car handles to its optimum.

books are ok (which i can buy) but none seem to take driver weight into consideration, and seeing as im a big fooker lol, i would say thats a very important factor.
if i cant find any info then it will have to be trial and error which is gonna take me a lot lot longer, to get right.

 

[tomble]

Don't know if this is any good to you, mate?

It has a small mention of driver weight in there..

http://www.articlecity.com/articles/auto_and_trucks/article_1601.shtml







Tom

 

[youngsyp]

Bob,

As you've touched on, for the optimum result, you need to adjust all the suspension settings, including alignment with a weight substitute for yourself, in the drivers seat. A good one is bags of cement dust or, my favourite, paving slabs.

Obviously, you need to make sure the ground the car is sitting on is also level.

Once you've done that, adjust the ride height to your preference. After this, you should get the alignment (toe and camber) adjusted to suit the ride height settings.
Once that's done, you can move on to adjust the bound and rebound after driving the car, and getting a feel for how you want the chassis to perform.
This is the trial and error bit and will take some time. Again, this part will almost certainly change from track to track. Strictly speaking, so should the camber and toe and ride height but, I'd see how you get on with these set at one 'baseline' set up first, on the different tracks you use. Then if you think you benefit by changing these settings, for the different tracks, go from there.

Setting up a spreadsheet in Excel would be a good idea. That should make tracking the changes easy.

When I fitted my coilovers, it took me a day to get the ride height as good as I could. From memory, it was around 3mm different across the rear axle and 2mm different across the front. That was a first go so, next time I do it, to lower the back a touch, I'll try and get it a bit more accurate.
Once you start to play around, you will start to see patterns forming and from there, it will start to get quicker, in terms of getting the settings you want. For example, an adjustment at the NSF, will have a greater affect on the OSR than the rest of the corners etc...

Paul

 

[pulsarboby]

Don't know if this is any good to you, mate?

It has a small mention of driver weight in there..

http://www.articlecity.com/articles/auto_and_trucks/article_1601.shtml

Tom

thanks tom that is very usefull, ive just now learned that its crossweight that needs to be altered, but still does not explain what exactly, i guess ride height:?


i like this quote lol:
Cross weight is usually difficult and time consuming to adjust on a street car even if you have installed aftermarket suspension components such as coilovers. Unless you are building a pure race car for oval tracks, you don’t have to worry about cross weight adjustments. Remember that the weight distribution of your car, particularly front bias, is the most fundamental characteristic that affects how your car handles. Keep in mind that the weight of the driver affects weight bias. Placing parts on the right side of the car will help balance the weight of the driver on the left side<.


what the fcuk am i gonna find to put another 17 1/2 stone on other side to match my weight (other than another fat b@stard):lol: :lol: :lol: thought the idea was to remove weight not place christ knows what in car to balance it:doh:

so back to square one again!



thanks paul....but still dont understand!:?
if all these settings are made with slabs or whatever placed in passenger side, then surely the car will still be unbalanced when they are removed?

 

[Braveheart]

Put Clares handbag + your wallet in passenger side, that should do it.

 

[pulsarboby]

Put Clares handbag + your wallet in passenger side, that should do it.

:lol: :lol: reckon her bag will be enough scotty, with all the crap she carries round with her!
ive got short arms and deep pockets so cant reach my wallet

 

[youngsyp]

if all these settings are made with slabs or whatever placed in passenger side, then surely the car will still be unbalanced when they are removed?

Bob,

That should be drivers side. You're aiming to simulate the effect your weight has on the chassis set up. By placing, what amounts to the same weight as you, in the drivers seat, you can set the chassis up around this and therefore, equalize the side to side, front to back and opposite corner to opposite corner weight balance.
Of course, if you have a set of scales (4), you can also corner weight the car, for an even better balanced chassis. There are a few places dotted about the country that'll do that for you.
If it's basic settings you're after, as Rob said, have a look round for Jim's threads. That's where I took my basic ride heights etc.. from. I can vouch that they work very well although, mine aren't identical to Jim's set up. I do still have the nose down **** up stance though. The ride height on mine is around 10mm higher at the back than it is at the front.

Paul

 

[Braveheart]

:lol: :lol: reckon her bag will be enough scotty, with all the crap she carries round with her!
ive got short arms and deep pockets so cant reach my wallet

:lol: :lol: :lol:
You must have scottish blood in you.
You can get it surgically removed. A stagged walk through many of our dark streets in glasgow could see that done for you.... :doh: :shock:

 

[pulsarboby]

ah right! got you now.
reading the other thread on crossweighting had confused my poor little brain lol
yes its now starting to make sense, thanks!

 

[youngsyp]

ah right! got you now.
reading the other thread on crossweighting had confused my poor little brain lol
yes its now starting to make sense, thanks!

If you look at it in the simplest of ways: Draw a line down the exact middle of the car, from front to back. With your weight substitute in the drivers seat, each parallel corner measurement should be the same. So, if the OSF right height is 330mm, so should the NSF. If you have 1.5 degrees of negative camber on the NSF, you should have 1.5 degree's of negative camber on the OSF. And similarly with the NSR and OSR. Obviously though, you don't have to equalise the ride height and other settings front to rear as, each end behaves completely different to any steering input etc...

If that's trying to tell you how to suck eggs, I apologise. I just wanted to break it down.

You'll be surprised how much different each measurement will be without the weight substitute in the drivers seat. So, it's very worth while taking that approach.

Paul

 

[pulsarboby]

yep your right paul, gotta say that i did not actually think of substituting the driver weight when making the necessary adjustments.
il start with the wheel track as im running a 20mm larger track on rear to help with understeer

then ride height which i was gonna set at 20mm higher on rear (once again this should help car oversteer i think) as it will not bog down on rears so easy with a higher, and harder damper setting to rears.

then i can start messing around with preload etc, but its all a bit of trial and error there really.

gonna leave front camber at 0 to start with.

 

[youngsyp]

yep your right paul, gotta say that i did not actually think of substituting the driver weight when making the necessary adjustments.
il start with the wheel track as im running a 20mm larger track on rear to help with understeer

then ride height which i was gonna set at 20mm higher on rear (once again this should help car oversteer i think) as it will not bog down on rears so easy with a higher, and harder damper setting to rears.

then i can start messing around with preload etc, but its all a bit of trial and error there really.

gonna leave front camber at 0 to start with.

Sounds like a plan to me.

One thing, as I understand it (thanks again Jim), adjusting the ride height will have a significant effect on toe. So, it might be an idea to adjust the ride height first, and then the toe angles etc...

It's nice to be able to measure and make all the changes yourself. I have to pay £95 everytime I adjust the alignment/ ride height !

Paul

 

[warringtonjack]

You could just sack it all off, and reconfigure the drivers position for dead centre, a la mclaren F1!! :lol: Might even be an easier option! :lol:

Oh no, hang on, dunno if I could cope with the missus bleating into my earhole from the back seat!! :roll:

 

[youngsyp]

You could just sack it all off, and reconfigure the drivers position for dead centre, a la mclaren F1!! :lol: Might even be an easier option! :lol:

You'd still need to substitute your weight though, no matter where the drivers final position was. ;-)

Paul

 

[campbellju]

Bob, I think I gave you my number if you need a hand but this sticky has most of what you need to know on ride height/corner weighting.

http://www.gtiroc.com/forums/showthread.php?t=34637

A few highlights;

1. level your floor
2. Stick weight of yourself in the driving seat. (Notice my amusing use of the kitchen sink in the sticky)
3. set your tyre pressures
4. Set all your springs to full loose and your dampers to full soft
5. Set front ride height first before rear. there is so much weight on the front that this has a big affect.
6. Set camber, then set toe, then tweak both to what you want. If you run lots of castor like I do this becomes a complete nightmare.

optimum settings....

There are no perfect settings and everybody is different but here are some guidelines:
ride height centre to arch
front 325 to 340mm
rear 330 to 355mm

Higher is better in wet, lower better in dry.
The centre to arch difference front to back should be 5 to 15mm
High difference improves turn in but makes rear less stable. Small difference can make the rear feel like its dragging its a*se around.
Optimum for the ride height and difference is very dependent on the components your using and your driving style.

Corner weights are important but suspension geometry equally so. Our macpherson suspension makes it impossible to do them independently so I shouldn't get hung up on it.

level your L/R your ride height, make sure you are happy with it and then if you want take it to get cross weighted. There are no home garage solutions for cross weighting but I shouldn't get as hung up on it as most people seem to. Many race cars use asymmetrical setups anyway and you can understand what weight each corner is supporting through spring deflection.

As an aside, your 17.5 stone will have the biggest affect on the driverside rear corner as your weight is roughly split 50/50 front to back doen the drivers side and your rear has softer springs. 17.5 stone equals 111Kg that puts about 55Kg at the back and deflects a 3kg/mm spring by 18mm or a 5kg/mm spring 11mm. Like Paul said, once you've been round the car a few times you can work out which corner to change to help balance your corner weights better.

Set dampers to the minimum you need to control re-bound. Damper difference front/rear should be small and only be used to improve transistions not to change the overall balance as some people do. On dampers matched to springs then much more than 10% difference and you should probably tweak something else.

Camber amount is dependent on how low you've gone on your ride height, what castor you use and how sticky your tyres are. For serious track use think -2 to -3 front with about 50% at the rear to start with. This is very dependent on level of grip, higher grip needs more camber

toe, for track think 0.1deg toe out front and rear as a starting point. You might want to move to 0.2deg toe out front to improve turn in further. Toe in at rear can numb the turn in but helps on catching oversteers. Nothing wrong with straight ahead and I wouldn't go past 0.2 deg toe in/out front or rear. If you need to then something else is wrong.

Widening track increases stability so if you widen the rear you will understeer more. If you then raise the ride height it will unsettle the rear end more. If you do them both then they might cancel each other out but it will point more weight over the front which might help... sounds wierd but might work and I know FWD owners do everything they can to keep the weight over the front. Widening the front track instead might be a better compromise and leaving the rear height/track where it is. There are no right answers for our cars and if you're thinking dry race track only then we might need to get a bit more extreme on some of your components/settings.

In a nutshell that's it.

To set ride height you need a tape measure.
To set camber you can use string and a calcultaor but now I borrow Stu's £80 digital camber guage because its as accurate and a shed load quicker.
My toe plates cost me about £10 to make (I'm tempted to buy something but you need to spend £300 to £500 to get something much better)

On the day at the track you can only easily adjust tyres, dampers and roll bars.

 

[pulsarboby]

thanks jim thats very usefull info there, which il put into practice.

im surprised that having a large rear track and narrower front will make it understeer more though, would have thought it would have been the other way round! as on hard turn in the back would try to kick out due to the narrower turning angle on the front.
ie imagine say a trike lol, it would be impossible to make it understeer because the rear is much wider, but i could well be wrong?

 

[fubar andy]

There are no right answers for our cars

Have to agree there.

I'm certainly not as advanced at Jim, but I have found that after a trackday, I record my settings for what I feel what the best setup for my car.

From recording my settings at Oulton Park one month, the next month when I went to Donington Park that set-up wasn’t working well. So I spent the morning changing it till I was happy with its characteristics and handling and made a note of that.

I find that its more a case or trial and error, utilize what Jims posted (cheers Jim) and then take it to the track to fine tune to your personnel driving style

When I corner weighted mine I just used 4 bags of cement ;-)

 

[bracpan]

I am also a fat bugger and know a bit about suspension set ups etc. My self and a technician spent 3 hours with electronic corner weight's etc and let me tell any theorists its not possible to get the corner weights to read correct across the front and the rear at the same time with the driver like me sitting in the car.. We did get a good compromise in the end but its not perfect. But it did handle better.
To be honest if its a road car look at the Whitleline site and they give all the settings, use them and the car will be great for road use.
For competition ( like mine) it will take you ages to get the setup correct. I still have a few small things to try this year but I am getting close now, and its taken 3 years of competition to get it where it is now.
Good Luck
Phil