Porsche GB To Restore ex-Le Mans 924 Carrera GT
01-14-2016, 08:57 AM
#31
I believe Patrick was talking about the best sizing for performance, not street driving. The 944 platform can definitely benefit greatly from bigger fronts on a square setup, similar to the factory race cars. Many people who put on staggered sets normally meant for 911's, for example turbo twists, are still limited by the very narrow fronts, and don't have enough power or the right suspension/sway bar balance to make use of the massive increase in rear grip. A square setup with wide tires all round will not only offer the best balance at the edge of lateral grip, it also lets you brake way harder without locking up.
I would go so far as saying that people putting 911 staggered sets on their stock 944's have greatly contributed to the myth that bigger/wider wheels decrease performance, because all they are doing is adding unsprung weight all round while not being able to effectively use the increase in rear grip.
I would go so far as saying that people putting 911 staggered sets on their stock 944's have greatly contributed to the myth that bigger/wider wheels decrease performance, because all they are doing is adding unsprung weight all round while not being able to effectively use the increase in rear grip.
Craz..
I may of picked this up wrong for sure, but the wording
"Also a great example of what the factory thought when sizing the front wheels."
For me Factory means the Porsche production company for road cars?
If it was meant the Race team/ factory etc...then my reply makes no sense..
I also picked up on the staggered situation re 944 v 911's and hence my comments referred to a street / road car set up which when typical RWD and especially German (BMW, Mercedes & Porsche Sportcars) the reason the Tyres are staggered is down to the job of the front and rear tyres...
Wider rear tyres obviously have a bigger footprint and more molecules clenching the surface which is to cope with (Traction) the power....
A Front doesn't have the twist from power, hence why it has a smaller footprint but also on road cars it helps Mr. Average identify a loss of grip if the car understeers first.
Often anybody taking their street car on a track experiences this natural manufactures "built in" set up of understeer.
Racing is totally different and understeer is a pig.............So hence bigger fronts are often used in the case of the 50/50 even weight distribution of the 924 / 44 / 68 the same size tyres can be used all round as this allows for a great balanced when all 4 wheel slip angles are the same.
When higher power cars are used like the turbo, a wider rear is needed to eradicate wheelspin, but the static "steady state" cornering balance is affected as the rears have more grip than the fronts and Understeer occurs...
Tyre pressures, and Rebound rates can be changed to assist a better balance etc..etc... but this is all racing and getting back to the thread Comment with respect, I'm unsure if Patrick was referring to Street cars? where the Porsche "Factory" will never go oversize on a front for the safest street balance...or Racing cars ?
R
01-14-2016, 10:10 AM
#32
Pro
Yes, I agree with you. The factory road cars are definitely tuned towards under steer. You can especially see this with the sway bar balance and staggered wheels on the later, more powerful cars, where Porsche was trying to avoid having average drivers getting into over steer situations. A stark contrast to the factory race cars where Porsche was trying to squeeze out the best possible performance.
01-14-2016, 12:30 PM
#33
Yes, I agree with you. The factory road cars are definitely tuned towards under steer. You can especially see this with the sway bar balance and staggered wheels on the later, more powerful cars, where Porsche was trying to avoid having average drivers getting into over steer situations. A stark contrast to the factory race cars where Porsche was trying to squeeze out the best possible performance.
I may have some wheelspin issues? that's why I've installed the Wavetrac LSD
I gonna run lower rear pressures (29psi) for that dragster twisting effect, and I do have a reasonable 55 series profile......(See Avatar)
I may have to short shift in 1st off the trafic lights to 2nd then bury the pedal?
Time will reveal all....
I'll learnt so much about balance and handling Racing these 6 speed Shifter karts... intensely over 10 years and on and off over 20!
One of if not the best pieces of Advice I was told when i was learning the ropes...was :
Often people chase and try and cure the end of the car with a (Lack of) grip problem, when it's often easier and more effective if you look at the other axle and make a change to upset it and lose the grip here to balance the 4 wheels slip ...
So Eg: Understeering..........Upset the Rear !
Fit a Stiffer rear sway, increase the tyre pressures by 10% to get the slip angle more loose..., Increase the shock Rebound rate etc...
Karts actually have so much lateral grip (Due to no suspension)
Often it's too much ! and you need to loose grip !
Many a time it's too much and quite a big issue trying to lose it especially on the rear axle as it has no differential, so the inside tyre must come off the floor very slightly as it has less rotations to turn......
R