Max Front Spring Rate With Standard T/b

[niklas 1]

tyre gets most grip when tread is flat on the road surface, ideally, the wheel is perpendicular to the road surface. lateral grip is shared between the front and rear wheels depending on the weoght distribution and weight transfere, nothing else, i'e more lateral grip on the rear during accleration. pretty much irelavent what tyres are used. the static neg camber is only really there to counteract flexy type stuff and any posotive camber gaied during roll or compression, like on Mac struts.

 

There is actually a very big difference depending on which type of tyre is being used!

The grip from semi-cut slicks (compared to road tyres) enables a lot higher cornering speed which leads to more roll which requires more neg camber to keep the tyre flat to the ground. And the difference between semi-cit slicks and slicks is also very big leading to even higher cornering speed thus even more roll and so on...

 

I agree totally on the weight transfer and weight distribution bit BUT the front outer wheel will always take a huge amount of the cornering forces depending on the weight on the front axle. Looking at the traction circle we see that when we start putting two different loads on the tyre (cornering + acceleration) the total available traction is quickly descending!

That's why the wear on the front tyres are a lot higher and the risk of overheating the front tyres (while it's sometimes hard to get enough heat in the rear tyres) are such a big problem on front-heavy FWD cars. Especially in endurance racing.

 

[tony perks 1]

My own 2p's worth, I get good results from running a 195 front spring, with std 1.6 bars in the back and running challenge spec inserts in fixed platform billys front and 309 tarmac rears billys, i used the 195's as a compromise beetween factory advised 185 gravel settin and 225 tar settings as although i do a tarmac rally championship, some venues are super smooth eg colerne then you get other places like down ampney or ditton priors that are ..........not so smooth. As for the handking it is very neutral turning in nicely with no snap oversteer and from phot's little body roll, However in the wet its a pig to get to turn in understeer city! but great fun all the same oh by the way i use michelin and dunlop moulded slicks with a very tight tran-x slipper.

[TVH 0]

I guess I need to clarify that from my perspective I'm talking about a pure racing setup running on semi-cut slicks (aka r-tyres). That type of tyre is very common over here but I'm not sure which type is commonly used in the UK.

Road tyres obviously don't require that amount of neg camber and doesn't produce as much roll, while slicks typically require 5-6 degrees neg camber to use them right.

 

For just road fun and the occasional track day, a more road-oriented setup will give much more fun!

 

But when you go beyond that and just need to go faster, the next step is to locate where the grip is lacking. And this is normally the outer front wheel which takes something like 65% of the load during cornering and probably even more when accelerating out of the corner.

So that is my reasoning for a very stiff front setup, increasing the grip of that wheel as much as possible. It doesn't mean I ignore the rear axle but there are physical limits to what can be done without altering the suspension completely.

 

But I think it's the same as with engine tuning, there are many different ways to reach the same result!

 

Bumping up this old thread...I agree with you Niklas. There's a desperate need for more camber under hard cornering. Just look at this pic and you will see what happens on the suspension, I'm approaching a fast left hand corner at 130kmh, running on racing slicks, 309 wishbones, top mounts set to full caster, 325lb front springs. Looks like outside front goes to positive camber! Much, MUCH more static camber is needed to overcome the issue.

 

Another thing, if you look at the picture you see how high the car is. It should be 5cm lower, or even more! But the problem is, the wishbones already point upwards, roll center is somewhere below ground level. This will increase body roll even more. The solution would be modifying the wishbone mounting points on the subframe, has anyone done it? Or do you guys just lower it and fit some ultra stiff front springs?

[TVH 0]

Most series' don't mind you adjusting the geometry of the lower wishbone provided you only alter it to fit offset bolts, which is fairly easy to do, then lift the pivot as far as you can vertically.

 

How far can it be lifted, any estimate?