Discussion
A question about relative track widths front/rear. There is this idea that on a RWD car the front track width should always be at least 1" wider than the rear as this will reduce rear inside to front outside weight transfer, and hence reduce the chance of the inside rear lifting and loosing traction etc. etc. However a lot of cars turn this rule-o-thumb on its head, the MX5 for example right from the start had a wider rear track, the Ginetta G40 equal track and cars such as the Porsche Cayman more extreme with a rear track 2" wider than the front.
So the question for the suspension and chassis gurus who is right? (or rather what is right) Is that old rule of thumb potentially not applicable to cars now as perhaps it was in the old days when track cars were much more traction limited?
So the question for the suspension and chassis gurus who is right? (or rather what is right) Is that old rule of thumb potentially not applicable to cars now as perhaps it was in the old days when track cars were much more traction limited?
NJH said:
A question about relative track widths front/rear. There is this idea that on a RWD car the front track width should always be at least 1" wider than the rear as this will reduce rear inside to front outside weight transfer, and hence reduce the chance of the inside rear lifting and loosing traction etc. etc. However a lot of cars turn this rule-o-thumb on its head, the MX5 for example right from the start had a wider rear track, the Ginetta G40 equal track and cars such as the Porsche Cayman more extreme with a rear track 2" wider than the front.
So the question for the suspension and chassis gurus who is right? (or rather what is right) Is that old rule of thumb potentially not applicable to cars now as perhaps it was in the old days when track cars were much more traction limited?
In theory that can help, but it's just one of many approaches and will cause the opposite problem with transfer in the other direction. In reality track widths these days are usually set by a) practicalities and b) aesthetics.So the question for the suspension and chassis gurus who is right? (or rather what is right) Is that old rule of thumb potentially not applicable to cars now as perhaps it was in the old days when track cars were much more traction limited?
If you're limited to a 1.8m overall width (e.g. F1) then you'll always be better off with the full 1.8m at both ends than limiting one end to keep a ratio.
FWIW the rear end on my Locost has ended up around an inch wider track than the front due to fitting 8" slicks and having to clear the inner arch. Traction has improved all round due to the extra rubber and controlling tyre temps a bit better, which has outweighed any weight transfer changes.
I think this difference (1-2 inch) matters little , much less than different spring and antirollbar rates. You are also mixing different layouts: front and rear engined. Additionally I assume the manufacturers would normally prefer the front wheel lift which would increase understeer for safety reasons.
Ferrari 430 and 458 have a much wider front track whereas boxster and cayman are the other way round. Its easy to understand why 1" or 2" wider on the front could be popular as with front tyres are usually a fair bit thinner putting the outside edge in the same place would result in that wider front track. For cars like the boxster and cayman though it looks more like a conscious decision Porsche made to do things that way, why?
If the rear track is wider for example a force applied on the outside wheel will make the car turn around the front more than if the track widths were arranged the other way round. I confirmed this years ago on my 944 when I put spacers on the back to square off the track widths (basic design has 20mm wider front track), the result was it eliminated the inherent understeer the car had on the power, but I was always convinced the car lost some bite on turn in.
What interests me about this is its something you more or less never hear or read about despite that fact that for most of us either tracking or racing production based cars we can put on spacers, different wheels etc. to our hearts content.
If the rear track is wider for example a force applied on the outside wheel will make the car turn around the front more than if the track widths were arranged the other way round. I confirmed this years ago on my 944 when I put spacers on the back to square off the track widths (basic design has 20mm wider front track), the result was it eliminated the inherent understeer the car had on the power, but I was always convinced the car lost some bite on turn in.
What interests me about this is its something you more or less never hear or read about despite that fact that for most of us either tracking or racing production based cars we can put on spacers, different wheels etc. to our hearts content.
Gassing Station | Suspension, Brakes & Tyres | Top of Page | What's New | My Stuff