[DeTomaso] Tire Comparisons

[John Taphorn]

List has been quiet, so I'll share a recent Pantera project I am working through on my car.

I've started down the slippery slope of an exterior cosmetic freshening of my GT5 and have started with wheels and tires.  Out with the 15" and in with the 18"/19".  One reason for going to the larger size is the availability of the reasonably short 285/30/18 that is only about .75" in taller than the stock 15" tire.  Curiously, A shorter tire for a 17" wheel is not made.  Of course, the logical concomitant to the front 18" is then to go to the 345/30/19 Viper rear tire for availability and to maintain the width.  

I'd like to Open Rode Race this car and the 345/19 is almost a full 3 inches taller than the stock 345/15.  That is the difference between 97mph and 109mph at 4000 RPM.  A reasonable alternative to the taller 5th.  

I currently have 17"/18" wheels on my L.  By extending the lugs on the GT5 with 12.5 x1.5 threaded rod, I  was able to mount the L's wheels/tires at various front to back spacings on the GT5.  I removed the shocks to allow me to jack the tire into the wheel well and measure for interference.   This permitted me to see how much suspension compression that I could achieve before contacting the flares. I taped a 5/8 inch rubber hose on the outside lip of the 335/30/18 to mimic the diameter of the 345/19.  

Using the stock sized wheel as a benchmark, I held a digital inclinometer on the lower A-arms to determine allowable compression at various back/front spacing of the front and rear tires.  As a back up, I also measured the spacing of the shock mounting points at the point of interference.  With nuts on the threaded rods to act as the mounting surface, I was able to try all combinations of spacing.

Among the criticisms of larger diameter tires on a GT5 is the higher ride height often required to provide adequate clearance of the flares.  The problem is that the flares curve back into the body faster than the suspension pulls the tire back.  Unless one reshapes the flares, they are the first contact point on a flared car.  In contrast, on a stock bodied car, the first contact point is generally the inside upper frame rail.  In my opinion, I found an acceptable compromise with the wheel spacing that will allow stock suspension settings.  Of course, even with the same suspension settings, the taller tires will have the body's stance 1.5" higher in the tail and .375" in the front.  I'll live with that.

With this data in hand, I moved forward with new wheels.  Now, of course is tires.  I went to the Viper Forum to try and learn what those boys are finding acceptable for rubber.  I found this review and thought it may be helpful for others.  


This is a cut and paste from a C&D tire test from the summer of 2009. I have been asked it several times so, I thought I would post up the information here
Could any of these nine low cost offerings knock off the Pilot Sport PS2? 

The Michelin Pilot Sport PS2 in the test size of 225/45-17 costs $192.00. 

Here's where the challengers come in price wise: 
BF Goodrich G-Force T/A KDW2 ($126)
Bridgestone Potenza RE760 Sport ($132)
Dunlop Direzza Sport Z1 Star Spec ($137)
Falken Azenis RT-615 ($121)
Hankook Ventus V12 EVO ($106)
Kumho Ecsta XS ($120)
Ling Long L688 ($57)
Nitto Invo ($117)
Yokohama S-Drive ($115)

The test covered several different areas of performance. AutoX , skid pad , braking , price and ride quality. I am not going to reproduce the entire article but, here are some of the numbers 

AutoX times wet/dry

Michelin Pilot Sport PS2 60.7 / 60.1

BF Goodrich G-Force T/A KDW2 61.3 / 59.6
Bridgestone Potenza RE760 Sport 62.5 / 60.1
Dunlop Direzza Sport Z1 Star Spec 60.8 / 59.3
Falken Azenis RT-615 64.2 / 59.8
Hankook Ventus V12 EVO 61.0 / 59.8
Kumho Ecsta XS 65.4 / 59.0
Ling Long L688 65.8 / 61.1
Nitto Invo 61.9 / 60.5
Yokohama S-Drive 61.5 / 60.3

SKIDPAD, g's wet / dry

Michelin Pilot Sport PS2 0.88 / 0.92

BF Goodrich G-Force T/A KDW2 0.85 / 0.91
Bridgestone Potenza RE760 Sport 0.80 / 0.90
Dunlop Direzza Sport Z1 Star Spec 0.86 / 0.92
Falken Azenis RT-615 0.80 / 0.91
Hankook Ventus V12 EVO 0.87 / 0.93
Kumho Ecsta XS 0.77 / 0.94
Ling Long L688 0.73 / 0.88
Nitto Invo 0.82 / 0.91
Yokohama S-Drive 0.84 / 0.88

after the testing the Car and Driver test drivers and staffers still consider the Pilot Sport PS2 the top summer performance tire.

Final Results for the challengers

#1 Dunlop Star Spec
#2 Hankook V12 EVO
#3 Kumho Ecsta XS
#4 Bridgestone RE760
#5 BF Goodrich KDW2
#6 Yokohama S-Drive
#7 Falken Azenis
#8 Nitto Invo
#9 Ling Long L688

to see some of our in-house test results use this LINK
__________________