Running smaller (diameter) track tires on C5Z
02-04-2014, 05:41 PM
#1
Drifting
Thread Starter
Running smaller (diameter) track tires on C5Z
I drive my basically stock C5Z a lot on the street and am trying to come up with ways to increase track performance without negatively impacting street manners. One thing I'm considering is running short tires.
My thought is that running a set of Hoosier A6's in 275/35/17 will give me roughly half an inch lower ride height on the track and also a slight bump in effective gear ratio compared to 275/40/17, plus the shorter sidewall might help steering response a bit.
Is there any downside to doing this?
I can't go wider than 275's without incurring a power/weight penalty in NASA's TT classing, so wider tires are out.
My thought is that running a set of Hoosier A6's in 275/35/17 will give me roughly half an inch lower ride height on the track and also a slight bump in effective gear ratio compared to 275/40/17, plus the shorter sidewall might help steering response a bit.
Is there any downside to doing this?
I can't go wider than 275's without incurring a power/weight penalty in NASA's TT classing, so wider tires are out.
02-04-2014, 06:23 PM
#2
Safety Car
The ratio change may or may not be helpful.
The feel will be different which may affect your lap times.
I can't remember if I ran 40s or 35s when I used to use 17" 275s, but you will be fine either way.
The feel will be different which may affect your lap times.
I can't remember if I ran 40s or 35s when I used to use 17" 275s, but you will be fine either way.
02-05-2014, 01:08 PM
#3
Drifting
I used 275/35ZR18 which are 25.5" tall.
The P275/40ZR17 is the same height as the ones above @ 25.5".
P275/35ZR17 is shorter @ 24.7" so you'd be doing more shifting. 3rd gear is already too short in the z06 tranny and now it'll be even less "good'er". You'll be grabbing 5th more often especially at the glen. I don't think I'd use the shorter tire.
The P275/40ZR17 is the same height as the ones above @ 25.5".
P275/35ZR17 is shorter @ 24.7" so you'd be doing more shifting. 3rd gear is already too short in the z06 tranny and now it'll be even less "good'er". You'll be grabbing 5th more often especially at the glen. I don't think I'd use the shorter tire.
02-05-2014, 03:09 PM
#4
Drifting
Thread Starter
Nuts. Do you not slow down to like 40-50 on most tracks? Seems like that is borderline 2nd gear territory and a slightly shorter 3rd gear would be useful, with faster corners switching from being at the top of 3rd to the bottom of 4th. I don't have any data to back up any of that though.
02-05-2014, 03:30 PM
#5
Race Director
A walk thru the pits to see what the fast guys run is all you need to do. No need to bench race it on the forum.
IMO I think it's worth a try. It should be a very easy calculation to figure your 4th gear top speed.
Overlay that on the tracks you run.
Done.
IMO I think it's worth a try. It should be a very easy calculation to figure your 4th gear top speed.
Overlay that on the tracks you run.
Done.
02-05-2014, 08:13 PM
#6
When I first put my TTA car back together in 2010 I set it up on 275/40/17s. Then I upgraded to 275/35/18s. The car feels more stable with the lower sidewall of the 18s. Also, putting them on the 18x10.5 rear Z06 wheel (vs. the fronts for the 17s) increased the track further adding to stability.