meine auto and the ring.

It's plenty clear Matt. Just trying to help and your behaviour says it all for me. Good day and good luck.

 

Brrrr, guys, guys. C'mon, let's be nice

I agree with vw_singh's suggestions - he does know what he's talking about - mainly a little more front camber or an additional rear ARB. Nice simple tuning.

No faff with spring rates, or top mounts, which are a big threshold to cross, making the difference between a daily road car and a more uncomfortable track car.

I agree with Matt not wanting to make the car more skittish at the rear though - it's the last thing that's needed. But, if you want more front end grip, then you are increasing the neutrality of the car one way or the other, and are therefore bringing the rear into play by definition. That shouldn't make it unforgiving if you get it right though.

An alternative - dismiss if you like, but it's commonplace in racing - is to bang up the rear tyre pressures. I was at Spa with a mate of mine in his Focus RS in 2004. Chewing away at front tyres, the damn thing had an damped throttle position sensor as standard, whereby the ECU slowed the lift-off efffect, making it hard to use a throttle lift to get it to change poise. A weedy rear ARB on cheese-soft bushings didn't help either.

The on-day solution was 45psi in the rears, and far more neutral handling on the big sweepers. Two corners and the difference was obvious.

Long term, having been in touch with a Prodrive engineer who revealed that they were more oversteery in the development stage, I was nagging my mate to get some harder rear ARB bushes made up to bring the rear bar into play more.

It's just subtle changes that are needed - not race suspension.

Toe out at the rear you don't need - it's dangerous in FWD. I've been there with a bent rear beam, and the things will swap lanes before you've touched the indicator, trust me. Lowering a rear beam will convert the OEM positive camber to more toe in at the rear. Toe in at the rear will make the car more understeery on track, since the back isn't trying to turn. Just a check to ensure the rear beam tolerances are ok will do no harm (see Haynes book of lies for settings).

Raising the rear will raise the C of G, and that may be a solution to try.

More toe-in at the front might make the car keener to turn, and if you've had the wisbones off at the front or changed them, the tracking might have moved (doubtful, but I had that on a F*rd once). If you've got more than 30 minutes of toe out at the front, then car will become very vague around turn-in, and cause understeer or lack of confidence in it.

I do hope this helps

 

Matt vw singh has given you the correct info, get your head out of your bum and listen.

Are you always this annoying?


edit Chris beat me to it

 

last bit is a little confusing, isn't toe out normally good to reduce understeer?

 

I've always found toe-in FWD to be far keener to get into corners, more confidence inspiring.

Toe out has some arguments for it, largely around better feel mid corner <---- though I'm quoting what I've read there. Also static toe out can pull up to straight toe on high power applications (> ABF fury ) as the bushings compress - but at this point I'm spearing down the road of nonsense as far as chassis-tuning a daily is concerned.

Hopefully there's enough ideas there.

 

toe in at the front will make the turn is more responsive... only ive just paid wedge to have the geometry done (-2* camber and paralell toe lol)

i wont be considering another rear arb. the rear of the car can be already used to hussle the car aroung a corner, esp helpful at the ring when youve turned into something and found it has a second tighter apex or youre piling into a right hander and want to tighten the line to allow another car to pass

i might experiment with tyre pressures, but tbh im hardly going to be able to replicate the same cornering situations again on a uk road

mine is currently on 195/50/15s. what would typical pressures be? vw recommend 38F/32R. ive got mine on 40F/40R

 

have you still not got it? i dont need to add more oversteer to the car. it does it nicely and when i want it to as it currently stands.

 

This is the key paragraph which is relevant:

If the car is to understeer less, you have to bring it up to neutrality. This means the rear has a greater part to play, which will be evidenced by more tyre / tyre-edge wear at the rear. There's no escape - the two are correlated & that is why many FWD manufacturers, Pugs excepted, used to get away with serving up understeering pigs. It's safer.

On toe, if you know where it's set ie parallel, you can alter it by counting 'flats' or turns. One turn each side, and you can always revert. Find the pitch of the thread on the steering arms and that'll then tell you how much change per turn of the arms you get. I guess it's M14 x 1.5, which IIRC is 1.5mm per turn.

Then compare with the Excel screengrab in the DIY tracking guage thread. IIRC, that's for 15" wheels.

Also worth a read-in, Suspension Geometry FAQ (camber, castor, toe & effects)

 

lower your 40psi in the front first

 

it seems more roll resistance at the rear would help (logical really) but i dont want to go as far as adding another arb... what about adding those rear spacers like ive been meaning to for ages? would be a very subtle change

 

Just on the rear wheel spacers, increased track width at the rear will just make the rear more stable and less susceptible to move.

Adding spacers on the rear is a way of increasing grip... trying to think of the explanation. C of G basically has its work more cut out trying to get the better of the rear contact patch.

Someone put that in engineering English for me!

 

hi,

At the risk of being ousted...

I can see what matt82s gettin at...people do seem to to be obsessed with ARBs. Prob because on a std or midly modded road car they make a big differnece for a small outlay.

I've got a 28mm rear bar and I find it makes the car very twitchy at the back. Think about it, the rear beam IS already one massive ARB, plus the factory bar, plus another massive bar, you lose independence at the rear.

An ARB gives oversteer by reducing rear end grip! What you really need for better turn in (and more outright speed) in more front end grip. I want to bin my rear bar so I'm looking at;

- widetracking the front
- stickier front tyres, or wider
- more castor

Also i think turn in (initial) understeer is differnet from mid-corner (steady state) understeer, i.e. Stiffer front springs will give better turn in but maybe more mid corner understeer.

they're just my feelings, i'm still learning as i go so I'm happy to hear opinions.

cheers

 

matt is that you??

 

yup, agree with you competely mr 82. praise the lord!

ive already got nice coilovers, my roll is pretty much non existent now (a lot of ppl stick arbs on to get rid of roll...)

when the car is loaded up i can adjust it mid bend, confident oversteer is predictable and in hand... hence i dont want to touch that aspect of it

i just want more turn in response

 

Just briefly referencing to a FWD racer's perspective, what those guys do is get as much grip at the front as possible. Camber, caster, toe, tyre width, tyre compound, spring rates, tyre pressures etc.

Once that's all done, optimised 100%, they may have to take grip off the rear to get the car balanced in a corner, to avoid heaps of understeer. The only way to do this is to manipulate the rear to remove some grip, because a FWD car will not set times whilst understeering (end of story).

So chucking the race stuff to one side, as it's easy to spear down that road, if a fast road motor's front suspension is not going to change, tyres are fixed, dampers and springs decided on (choice / budget / be-botheredness), top mounts not changing, and importantly camber is fixed, then the front end is done.

Then in comes fine-tuning the rear, possibly removing grip through rear tyre pressures, rear ARBs, rear geometry.

So wording the logic that way, it makes sense - but the work starts at the front.

 

thats why my car is so fast round the twisties then??

 

not as fast as Sheryl tho

 

youre thinking about someone elses car now