996TT wheels on 993 C4S tire ?
08-10-2013, 01:32 AM
#16
Rennlist Member
Join Date: Apr 2006
Location: Rainforest (Vancouver, BC)
Posts: 7,570
Received 1,034 Likes
on
464 Posts
What Ken and Kein are saying is that running a 315 on the rear with a 245 front will tend to increase understeer. Reducing the gap in tire width front to rear will bring the car closer to a neutral or balanced car when pushed hard.
08-10-2013, 10:28 AM
#18
Rennlist Member
Join Date: Sep 2008
Location: Flyoverland - Central, Ohio
Posts: 3,226
Received 247 Likes
on
176 Posts
JHG, I'm still a novice at this DE stuff, but I have read and followed a lot of Ken's 993 comments and he and other "trackers" on the forum have been doing this track setup and driving for awhile. So I was reading between the lines as to what I surmised Ken was saying "balance" (w/o saying).
Tim was much more succinct then I was.
As I imagine it, wider in the rear helps with rear traction. Great for straight acceleration. But if speed in the corners is your DE goal, then too wide in the rear compared to the front will not allow the car to rotate in the corner (as much), thus understeer. Having the rear slip sideways a "tad", will help the car turn in a corner, thus straightening out the corner allowing the application of more power as you open up the wheel on exit. Too much rear traction in the corner may then just push the front (understeer) as you apply more power.
And all of this is dependent on suspension set ups, horsepower, etc.
I also wonder how such a wider rear will effect the 993 VC AWD action (if any)? If the VC works of slippage in the rear (heating up the VC fluid) compare to the speed of the front tire rotation and wider eliminates slippage in the rear in the corner, would you then lose the AWD effect (if there was any to Ken's point) in a corner as you understeer and apply more power? In theory slippage in the rear in a corner (with 993 AWD) should shift some power to the front. Eliminate slippage in the rear with wider tires on a C4 may actually eliminate the AWD benefit (if any). Just conjecture on my part.
And YMMV.
Regardless let us know what you do and how it works out as we are all looking for more data
Tim was much more succinct then I was.
As I imagine it, wider in the rear helps with rear traction. Great for straight acceleration. But if speed in the corners is your DE goal, then too wide in the rear compared to the front will not allow the car to rotate in the corner (as much), thus understeer. Having the rear slip sideways a "tad", will help the car turn in a corner, thus straightening out the corner allowing the application of more power as you open up the wheel on exit. Too much rear traction in the corner may then just push the front (understeer) as you apply more power.
And all of this is dependent on suspension set ups, horsepower, etc.
I also wonder how such a wider rear will effect the 993 VC AWD action (if any)? If the VC works of slippage in the rear (heating up the VC fluid) compare to the speed of the front tire rotation and wider eliminates slippage in the rear in the corner, would you then lose the AWD effect (if there was any to Ken's point) in a corner as you understeer and apply more power? In theory slippage in the rear in a corner (with 993 AWD) should shift some power to the front. Eliminate slippage in the rear with wider tires on a C4 may actually eliminate the AWD benefit (if any). Just conjecture on my part.
And YMMV.
Regardless let us know what you do and how it works out as we are all looking for more data
08-10-2013, 01:17 PM
#19
Three Wheelin'
Thread Starter
Kein, Thank you for the explanation. As you can all tell, I am pretty new to this. 
My car has Bilstein HD w HR springs, I am told this is margnally better than stock. I added a strut brace to the front because, well I really dont know. I had read that it hells stiffen the front a bit and would reduce the flex in the body. The shop I use set it up for street use since I was just going to do a few DE days.
In the corners, the car tends to push. I have gotten used to it but it would be nice to take those corners a little faster.
Why the wider rears? The stock 993 C4S tire is a bit narrow on the 996tt wheel. The edges of the rim are wider than the sidewall. I dont know what this does to performance but it bothered me. I thought a slightly wider tire would fix that. I did not think about how it would affect performance, guess I thought wider would simply be more traction. I didnt consider the effect of a wider rear on the handling of the car.
Why the Nittos? During my last de, my instructor suggested better tires, specifically mentioning the nitto nt01s. When I got home that night there was a set on rl for a pretty good price.
My car has Bilstein HD w HR springs, I am told this is margnally better than stock. I added a strut brace to the front because, well I really dont know. I had read that it hells stiffen the front a bit and would reduce the flex in the body. The shop I use set it up for street use since I was just going to do a few DE days.
In the corners, the car tends to push. I have gotten used to it but it would be nice to take those corners a little faster.
Why the wider rears? The stock 993 C4S tire is a bit narrow on the 996tt wheel. The edges of the rim are wider than the sidewall. I dont know what this does to performance but it bothered me. I thought a slightly wider tire would fix that. I did not think about how it would affect performance, guess I thought wider would simply be more traction. I didnt consider the effect of a wider rear on the handling of the car.
Why the Nittos? During my last de, my instructor suggested better tires, specifically mentioning the nitto nt01s. When I got home that night there was a set on rl for a pretty good price.
08-11-2013, 10:25 AM
#20
Rennlist Member
Join Date: Sep 2008
Location: Flyoverland - Central, Ohio
Posts: 3,226
Received 247 Likes
on
176 Posts
JHG, Let us know how it works for you. Engineers love more data. :-)
As I listen to pro drovers talk, some like a car that understeers, others oversteer, others loose, and some want it balanced. Enjoy your DE time, I for one want to see as many 993's as possible on the track regardless of the width of their rear tires :-)
As I listen to pro drovers talk, some like a car that understeers, others oversteer, others loose, and some want it balanced. Enjoy your DE time, I for one want to see as many 993's as possible on the track regardless of the width of their rear tires :-)
