Suspension setting / improvements

[rsfruitbat]

Hi Guys

As i am now mainly doing tarmac I was wonderng if anyone can share their demon tweeks which improves the handling even more?

At the NEC I saw Teds Sud and noticed the top strut mounts are back as far as they can go to increase caster. Does this make a big difference?
Do solid / metal strut top mounts improve things significantly? I am still using rubber tops.
I also heard about moving the rear wishbone mounting backwards or forwards. What does this do and why?
I have also seen the front wishbone mounting lowered once. Why?
Tubular suspension kits. Are they worth it and how robust are they? I am still using stock items but with some extra welding reinforcement.
We all know about negative camber and how to mod it on our cars but is there an ideal setting? I tend to run about 2.5 deg negative.
Springs are variable for me between 200 - 300lbs on the front

What about rear suspension?
Apart from uprated springs (450lbish) and shockers the only mod i have is poly bushes and adjustable panhard rod (length for diff ride heights)

Come on guys, play nice. What have you done and why (and size is not important )

rsfruitbat

[Veesix75]

Well, I can only go on what I've been told, and equally from similar discussions then your personal driving style is as important to deciding what you want.

A stiffer rear can help with rear oversteer, which you might like/need on tight Tarmac. Softer rear gives more grip. Some rear toe helps with turn in.

More castor helps high speed stability.

I have about 2.5mm camber.

My springs are 400ish front and 650ish rear.

I like my car hard and flat, but I think I might be sacrificing a bit of grip in setting it fully hard (shocks on the hardest setting)?

My mate always liked his softer, and 'roll' into corners.

[rsfruitbat]

Hi Vee

I dont tend to struggle with high speed stability so the main advantage of changing the caster for me would be the leaning effect it generates when going into a corner? So i could maybe reduce camber and possibly increase straight line speed but get the same amount of camber within a corner? But i think i would be correct in saying that the leaning effect must be proportional to the angle of steer ?
One thing i have noticed is that i get a circle of increased wear about a third of the way in from the outer edge of the tyre. Do others see this? Any idea what causes it?

rsfruitbat

[Veesix75]

I get pretty even tyre wear on the fronts, the rears run perfect, tracking is set straight if I remember rightly, poss 1degree toe out if not straight.

I don't quite understand the castor v camber point, nor why you would reduce camber if it's no more than 2.5mm or so (that's because I'm not qualified to understand it).

[BS25]

Lots of questions but not many firm answers as there are so many variables!

To offer comment to a few:-

We have run tubular wishbones for well over 20 years - the reasons for them are weight reduction and the wish to run rod ends/spherical bearings throughout. I don't recall any of ours having ever broken (across several cars, definitely not broken any on the 33) but they have always been used for circuit racing. Your tarmac events will generally be rougher - even those based at circuits and especially those on old airfields. For me, I wouldn't run the risk of current tubular wishbones you could buy as they are not for rallying. If you wanted to go the tubular wishbone route then it would be best to find out what material others are using and have your own made to suit.

Assuming you are running radials, 2-3 degrees of neg camber is a good starting place and probably all you need for rallying.

Castor - a little more than standard is desirable though at the expense of steering weight (heavier). Can make life tricky depending on how aggressive your LSD is but you have power steering so that's ok.

Solid top mounts are a good thing - helps with feel and takes compliance out. The compliance issue is important for fast road/rally - a car with too little will give you insufficient feedback over bumps. Not an issue on smooth surfaces. BLS fast road suspension had a mix of rubber bushes (body mounts) and nylon bushes - not legal in the old Class F.

Tracking - a little toe out at the front will help with initial turn in, too much will have very sharp turn in but will scrub the tyres and wash out mid corner. Make a
of strings for setting up so you are sure you are getting what you want.

Driving style plays a large part as Tim has said. You have the added difficulty of not being able to directly compare your and your cars performance against others on track in the way that us circuit racers can. Sometimes following someone else through a corner quicker than you thought shortens your learning process, I know you'll encounter other competitors on a stage but it's not as clear cut as the repeatable circuit scenario. Perhaps do a track day to fully understand your car on a consistent surface/corner sequence? On that basis, don't change lots of things all at the same time - you'll not know the contribution each change has made. Of course, if you make lots of changes and it all works then take it! Get some tuition at a track day - in all honesty, at our level, there is more to find in ourselves than with little tweaks. It all adds up of course but it's worth considering.

The other side of the question is, what is your car doing? What are it's characteristics you like and don't like? Often it's a case of compromise. Consider your driving style and how that could be affecting what you understand the car to be doing - busy and quiet styles can be equally effective but FWD really needs to be smooth. You've mentioned 'leaning' - are you talking about roll? Have you got a FARB fitted? Try heavier springs. Play with tyre pressures, etc.

[rsfruitbat]

As I understand it more cAmber equals more rolling resistance. So it's easier to move a car about with no negative camber.
I'm not particularly good at this but as I understand if you increase caster i.e. Lean the struts back then as the wheel is moved away from dead ahead by the steering then negative camber is induced so in theory you might get the best of both worlds?I
My steering is set about the same as yours

Thanks BS that's all great advice. I had some of those BLS top mounts a long time ago. Take your point about the trackdays. Surprising how much you can learn by having some independent tuition.

My personal preference is a progressive rear end breakaway. understeer is my nightmare. I personally don't run a FARB. Found i get get more grip without it.

Rsfruitbat

[BS25]

If you are happy with the grip you get from the front then leave that alone as it works. Loosen the rear end - cheap way to prove it is increased tyre pressures until you can feel the difference. From there you can go stiffer springs, RARB, etc.

[Spacenut]

I can't add anything to the good advice already dispensed, but I can speculate on a couple of your observations - changing the height of the front wishbone inboard pivot relative to the rear pivot will introduce (if you do it right) some anti-dive geometry, which as the name suggests, stops the nose diving too much under heavy braking.

Moving both wishbone pivots up or down will alter the roll centre of the vehicle. This is the theoretical point about which the car rolls. For Mac strut suspension, you draw an imaginary line at 90 degrees to the strut vertical axis off to the side. Then draw another line along the axis of the lower wishbone out to the side. The point in space at which the two lines intersect is then used as the origin of a line drawn to the contact patch of the wheel on the ground. The point at which this line crosses the vehicle centreline is the height of the roll axis. Changing the roll centre front and rear can be used to tune the roll characteristics of the whole chassis, transferring more or less weight to the front or rear, promoting roll oversteer or understeer etc.

Moving the wishbone forwards or backwards relative to the strut top will change the castor angle more dramatically than an adjustable top mount.

There is potential to adjust the angle of the hub carrier where it bolts onto the strut. By changing this angle, and also changing the angle of the strut itself you can alter the scrub radius, which can be used to compensate for large wheel offsets caused by wide rims. Scrub radius is also linked to the change in wheel camber as you move from straight ahead to full lock.

A band of tyre wear near the centre of the tread is usually indicative of over-inflation. The actual position of the wear band will be influenced by the amount of wheel camber in a corner. Closer to the outboard edge suggests to me not enough camber gain for the kind of corners that you are going around.

I would imagine that too much toe (in or out) would result in the most rolling resistance.

Good luck finding your ideal tarmac settings!

Lauren

[rsfruitbat]

Thanks Lauren, Bryan.
Lot to think about.
With regard to the tyre wear i am running about 26psi not which I wouldn't have thought was too bigh?
Someone once said it was to do with the Ackerman angle?

With the rear suspension if you want for out is it just some washers behind the leading edge of the stub axle

front end grip is inconsistent which is what I need to fix first of at least which knobs to twist to influence it.

Rsfruitbat

[Veesix75]

On a moderate temp day I set my fronts to 26 and rears to 28. If it's a hot day I lower them 1 to 2 psi. This is cold.

On the newer Toyo r888r Toyo recommend a lower starting cold temp, I tried their recommendation and didn't like it, the tyres took too long to heat up. The r888r supposedly lasts longer before overheating .

I'm considering yoko's as people have said the grip levels maintain for longer during a race, but yoko's have a stiffer side wall so they are either sticking or sliding with not much in between compared to softer side wall Toyo according to some feedback I was given.

On a Tarmac stage, how hot are your fonts and what psi are the tyres hot ?

My car is 850kg with me sat in it post race.

I have the new r888r on the front and have seen an improvement to the old 888 in that it lasts a 20 minute race better on a hot day, but I stuck with the old 888 on the rear as it seems to warm up quicker and temp and wear wise looks perfect on my rear. The rears have done a good 20 or so track sessions now and are still very good. Fronts about 6 and have had enough and will be entering rubber heaven for next year hence the yoko thoughts.

[rsfruitbat]

Hi Vee
I start at 26 front, 24rear normally. Stages are typically 8-10 mins in length. Fronts will typically have risen to 30. Rears vary. Once back in service the fronts will get reset to 26. Rears will depend on how the car is handling.
I have used yoky,s quite a bit on the back and have found them quite progressive in how they break away. Last event I had old style toyo 888 on and found characteristics quite similar once I had sorted the front out.
On the front I am using either kumho or hankook in various compounds.
If it gets damp then I run yoky,s on the front aswell. If it gets really wet I have some old matador wets but based on oulto n they could be going in the bin.

Rsfruitbat

[Veesix75]

Be interesting to see what others think, but the fronts at 30psi seems low so needing a bit more heat. I tend to get 34 to hot on the fronts.

Why do you reset the fronts in service ? I set mine cold and don't change them again between qual and race . If it's a warm day then I expect the pressures will be slightly up from what I set them at but I leave them as long as they are similar to each other. It's the when warmed up pressure you need to keep consistent ?

Having said that the Toyo site cold / warm recommendations are different to what I use.

VEHICLE WEIGHT
COLD PRESSURE
HOT PRESSURE
Very Light < 800kg
17 - 22 psi
22 - 29 psi
Light 800kg - 1000kg
20 - 26 psi
24 - 32 psi
Heavy 1000kg - 1400kg
23 - 27 psi
28 - 40 psi
Very Heavy > 1400kg
27 - 35 psi

[rsfruitbat]

Forgot to say car with both of us in and about a third of a tank is about a ton.
Resting the tyres is something we have always done. What I am aiming for is about 28psi when we come back in. Higher than that and you get more understeer. Certainly feels like that. It's also the tyre man on the day what he recommends.
Rear the highest i have fun is about 32psi

[BS25]

I hadn't factored in that you may be using different makes of tyres front to rear! Have you tried running the same front and rear? I know a tyre is a tyre but there is more to it than that. Are they all treaded or are some cut slicks? If it were me I'd be tempted to run the same front and back to get an understanding of what the car is doing and achieve a balance that way - sidewall stiffness and construction can vary on 'similar' tyres. Running a harder compound rear is something I've done before - but always the same make as the front.

It's years since I've run treaded tyres - they were Dunlop D101's and D84's before that - both very good and I suspect the D101's are pretty much the equal of current 888's. I ran them on my modified production Sud (steel panels and race engine - similar to Malcolms, etc) - I got to 36F and 32R - cold - seeing an increase of 6psi all round. Good enough for lap records of 1.45 at Cadwell and a 1.39 at Croft in 1997.

What works for others may not work for you so it's a case of methodical trial and error!

[PETROLHEAD]

I'll bet its all down in the "Black Book" somewhere eh Bryan?

[rsfruitbat]

When i have had mouldd slicks on te back i have too much grip there.

At oulton i eneded up with yokys on the front and r888 on the back and that was handling nicely.
Coming down from lodge corner through the right hander and then the left you could feel the back starting to drift / breakaway, then the tighter right left flick on the opposite side of the circuit sharper turn in and more drift. overall less steering input was needed to get the car pointing where you wanted it to.
I have run Yoky's AO21's front and rear but it tends to be when weather is poor so the back end will move around more then anyways

So compared to you both my pressures are way down. Wiill bear that in mind for Rockingham.

So if my pressures arent to high what could be causing this groove?

rsfruitbat

[Spacenut]

With regard to the tyre wear i am running about 26psi not which I wouldn't have thought was too bigh?
Someone once said it was to do with the Ackerman angle?

Ackermann angle and scrub radius are essentially the same thing, defined in different ways. But I would have thought either would cause "feathering" of the tread, either outboard or inboard, rather than a band of wear around the middle of the tread...

[rsfruitbat]

Thanks Lauren
Next time I am down the shed I'll see if I can find an example and take a picture.

Rsfruitbat

[902a]

My new coilover struts..

Ali

[Kegsti66]

That looks very nice.

[rsfruitbat]

Looks very nice. Whose suspension is it?

Rsfruitbat

[902a]

Looks very nice. Whose suspension is it?

Rsfruitbat

KW Competition

[rsfruitbat]

Expensive?

[902a]

Expensive?

Not cheap as custom built. Many woud buy a secondhand car for the money I paid for 4 struts

[KevJTD]

Just checked, a set for my integrale is about £1,600...just curious, not serious as only a road car.
They do have a good reputation for quality though.

[rsfruitbat]

I somehow guessed they weren't going to be cheap!

Ultimately if you are happy with them that's all that matters

Not sure I would be able to tell the difference

Rsfruitbat

[PETROLHEAD]

£400 a corner?

in all honesty, it aint that bad really.

Ohlins, Penske etc would probably be double that, for the reasons of infinite confusion from over adjustability!


D2 suspension is probably half of that price, certainly well under £1k, and has earned itself a good reputation on the track day and modified scene.

I fitted a full set during Neils 155 restoration, actually it was a fiat coupe platform kit but i made it work, and it was lovely. If it lasts as good as it looks, they should be worth a look at