Tommys86 said:
This thread needs to be released as a trilogy film or podcast - far too much to read in my coffee break!
So I'll cut to the chase, and apologies if it's already covered. We now have 2 sets of standard D90s......but currently run a standard setup (wider rears etc).
For a RACE car - do we fit rears all round - extra width on the front? As per above, seems like many racers run same all round, either D90 rears or another alloy etc. (accept it's probably going to boil down to personal preference!)
IF so, do we fit "wets" to the remaining 4 fronts? Logic being a narrower tyre (on rear), wet tyre, might cut thru standing water better / rivers (Spa).
Tom
Yeah thanks Tom, grab another Coffee break!
This may of been a simple subject to understand, but it's not always easy to explain and get your head round it with a few lines...
It's also difficult to accept for many as there is a huge following and lots of hearsay that big wheels and Tyres make your car handle better...
This discussion and subject was, and still is aimed at Road cars for the Road, because Racing has different requirements where some trade off's that are uncomfortable and hard to master they all part of Racing and not something most road car drivers would put up with.
There is however some characteristics that can be applied to the racetrack in regard to wheel & tyre lighter weights, which will make the car faster EG: Fitting lighter wheels, and also reducing the unsprung weight, but generally Racing Tyres and even semi road legal tyres are much heavier than Road ones, due to stiffer sidewalls. So it's not easy to have a lightweight Racing set unless you start looking at Magnesium..or Split rims.
The adjoining subject of Tyres, the widths and their sidewall percentage profiles though are not as clear cut on the track because
of the previous explanation regarding HEAT.
So if you ran 205/55/16 all round on 7x16 Rims and used Road Tyres as I did at Oulton but on a hot track for 40 mins you'd
not only overheat the tyres but would be much slower than your current staggered set up on R888's, even though these wheels are heavier, because the weight deficit will be clawed back becasue the tyres can corner at higher G-forces and not overheat.
In regard to your wet question, Understeer usually is the Killer with rain, hence why also where possible car's run a bias valve to knock off the higher front to rear braking split. You could try a square set up in the rain more like 7x16's and 205/55.16 all round as opposed to 8x16 and 225/50/16 because a narrow tyre you can raise the pressure to decrease the chance of aqua planning and most of all the contact patch on narrow higher sidewalled tyres is longer (Front to back) as opposed to a wide tyre which has a narrow band from left to right, which is not as good on slippery surfaces. So your actually getting a bigger contact patch in a shape more beneficial for the wet by fitting narrower higher profile tyres than benefit the acceleration and braking zones..
A higher centre of gravity is better for the wet too if possible, It loads and tips up the vehicle weight on the tyres slower and more progressively. When I raced karts we raised the seat height when wet, Formula One also does a similar thing to the COG as the wet tyres are "taller" than the Slicks so when fitted they raise the front & rear ride height for the same reasons.
Even in wet conditions full weight transfer and maximum grip occurs where the inside tyre lifts off the ground, this assists turning as there is no differential, only a solid axle.
Other factors also contribute to the Wet balance are your ARB sizes and the bump & Rebound shock absorber settings, which need decreasing for more movement.
Because of the Transaxle 50/50 balance the theory is you only need to provide grip for the task and weight distribution at hand and if this is split at 50/50 then the same size should be used.
Where some go is in the direction of the wider rear like the 255/40/17 especially when the front is 205/50/17 it's out of balance, the 225/45/17 front is slightly better but I've always found the rear end on all the transaxles I've owned (inc a 968) are totally user friendly and I don't recall ever having any oversteer from the power or steady state cornering.
Also I've found a wide tyre on the transaxle front doesn't and won;t turn in as keen as I want, this is why I only fitted 205 on all 4 corners of the 24 because it doesn't need any wider on the front or the rear, Tyre width is relative to the job at hand, look at the lightweight small diameter high profile Tyres on the Racing Caterhams.
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