[insite94]

Hi all! Not sure if this is the right forum to post, but I have a question for the list:



I am trying to get more TERMINAL SPEED out of my stock '92 968. Aside from proper maintenance, tuning, and addition of a performance chip, I am considering changing the rear tires from the stock 225/50/16 to 225/55/16. The conversion math says I should pick up 3.4% more "real" MPH than indicated on the speedo over stock, which brings up the ABS question.



If I leave the front tires at 205/55/16 and the rear tires now turn 3.4% slower at indicated speed, will the ABS light come on (since the ABS sensor perceives a 3.4% differential between front and rear revolutions per mile)? I guess the real question is at what percentage differential will the ABS hiccup?



Furthermore, if I change the front tires to a bit taller ratio (say from 55 to 60), will that "trick" the ABS sensors into thinking that all 4 wheels are again turning with the same revolutions per mile and not trigger the light?



Thanks in advance for any help on this.



Buzz

Partial Post: Please Login or Register to read the full post.

[Greimann]

According to the owners manual, it take s 6% difference to disable the ABS, so that is no concern.



Your goals of gaining top speed may or may not be met. Top speed is a complicated balancing act between engine power, gear ratio, aerodynamic drag and rolling resistence. Aero being the most significant. factor. You just can't do a straight calcualtion and get that result. It may well be that reducing the rolling radius may give you a higher top speed because you have move the engine RPM into a more favorable range. A quick simulation in Cartest 2000 shows that is the case. A smaller tire gives a higher top end, according to the program.



I think your best bet is to work the aerodynamic aspect first. That will by far have the biggest bang for the buck. Lower the car as low as you can with springs, and adjust rear ride height to get the best speed. Tape over the nose opening with racers tape. Euro lenses, delete the areial, tape over the hatch seams. Etc....



Why do you want to go faster anyway. I'm calling the CHP! <img src="/forum/images/smilies/968/biggrin.gif" class="smilie" alt="" />

Partial Post: Please Login or Register to read the full post.

[insite94]

"Why do you want to go faster anyway. I'm calling the CHP! "



Personal challenge, I guess <img src="/forum/images/smilies/968/laugh.gif" class="smilie" alt="" /> I have a need for speed. Besides the stress on the stock motor gets me that much closer to the "need" for a PowerHaus Turbo! <img src="/forum/images/smilies/968/biggrin.gif" class="smilie" alt="" />



Buzz

Partial Post: Please Login or Register to read the full post.