Very interesting thread and a subject I've had quite a bit to do with.
![](./images/smilies/spacer.gif)
I had a dune buggy which was built with adjustable rose joints on the double wishbone suspension so I have been able to play with the settings quite a bit.
![](./images/smilies/spacer.gif)
The first thing which a lot of people don't understand is the idea of weight transfer in corners.
![](./images/smilies/spacer.gif)
Equal length double wishbones
![](./images/smilies/spacer.gif)
(as found in several
![](./images/smilies/spacer.gif)
"high performance" kitcars) are
![](./images/smilies/spacer.gif)
*the* most dangerous thing out there.
![](./images/smilies/spacer.gif)
They're fine in a straight line but your car wants to roll as it goes around a corner.
![](./images/smilies/spacer.gif)
If both wheels are forced to remain perpendicular to the ground then most of the weight is on the outside edge of the outer tyre.
![](./images/smilies/spacer.gif)
If anything goes wrong the most likely outcome is you'll end up with the car on it's roof.
![](./images/smilies/spacer.gif)
Mcphereson struts were designed as an
![](./images/smilies/spacer.gif)
"economy" suspension design but they actually work pretty well.
![](./images/smilies/spacer.gif)
Systems using either unequal length wishbones, single wishbones or Mcphereson struts allow the cars body to roll
![](./images/smilies/spacer.gif)
*and* still press the outside wheel into the ground evenly.
![](./images/smilies/spacer.gif)
Sure, the inner wheel isn't doing much but the outside wheel is much more evenly loaded.
![](./images/smilies/spacer.gif)
That's where you start to get problems with low profile tyres.
![](./images/smilies/spacer.gif)
A tyre with a high profile will actually roll as the suspension position changes.
![](./images/smilies/spacer.gif)
When you travel in a straight line the contact patch is the centre of the tyre.
![](./images/smilies/spacer.gif)
When lateral forces build up
![](./images/smilies/spacer.gif)
(as in hard cornering) the tyre wall flexes and the tyre will actually curl slightly.
![](./images/smilies/spacer.gif)
It does this rather than breaking grip.
![](./images/smilies/spacer.gif)
A low profile tyre can't curl in the same way so the cornering forces load up until traction breaks.
![](./images/smilies/spacer.gif)
The other thing which escalates this problem is also to do with the tyre walls.
![](./images/smilies/spacer.gif)
When you steer suddenly the wheel will actually move about within the tyre.
![](./images/smilies/spacer.gif)
It can do this because the tyre wall is more flexible.
![](./images/smilies/spacer.gif)
In a low profile tyre the wall is more rigid.
![](./images/smilies/spacer.gif)
This gives you sharper handling
![](./images/smilies/spacer.gif)
(as well as more bump steer and tram-lining) but it also means that the car is now capable of sharper steering manoevres which, in turn, load up the tyres faster and cause slides with less warning.
![](./images/smilies/spacer.gif)
I found a cracking ebook about suspension setup on the net somewhere.
![](./images/smilies/spacer.gif)
Unfortunately, I can't recall the website.
![](./images/smilies/spacer.gif)
I did print it all out though so I'll post a link to it when I get home.
![](./images/smilies/spacer.gif)
If any of you want to look for it yourself it was called something like
![](./images/smilies/spacer.gif)
"A guide to suspension tuning in small vehicles", it really is a bible for suspension tuning.
![](./images/smilies/spacer.gif)
And it's free.
![](./images/smilies/spacer.gif)
Beyond that, the only other point worthy of making is regarding
![](./images/smilies/spacer.gif)
"on the edge" handling.
![](./images/smilies/spacer.gif)
.
![](./images/smilies/spacer.gif)
.
![](./images/smilies/spacer.gif)
It's all very well to say low profile tyres lose traction only in extreme conditions and if you're driving hard enough to cause it then you will be concentrating hard enough to catch it.
![](./images/smilies/spacer.gif)
Erm, no.
![](./images/smilies/spacer.gif)
If I'm blasting down a country lane on a sunday then fair enough.
![](./images/smilies/spacer.gif)
I probably will be paying attention.
![](./images/smilies/spacer.gif)
If I'm driving home from work on a rainy winters night when a car pulls out in front of me or a child runs out into the road then I could really do without the added worry of whether the back end is going to let go as I try to manoevre safely.
![](./images/smilies/spacer.gif)
Each to their own but I'd never dream of putting wheels and tyres on a car which could make it more dangerous to drive, even in the rarest situation.
![](./images/smilies/spacer.gif)
Aside from that, after spending my time crashing from pothole to pothole in our glorious road network, I think higher profile tyres are preferable.
![](./images/smilies/spacer.gif)