rmag

Haven't had a chance to hook up the RPM sensor to my datalogger. At the edge of running out of certain gears in a few sections at the local track. To better analyze data, ran a chart to see how much MPH left in gear without having to shift. Figured a few of you might find it useful...

GrantG

Looks like close to 5% difference - the smaller diameter Hoosiers should feel a little more snappy, acceleration-wise (almost as big a difference as RS vs. GT3).

Terry L

More like 4% - 1.1 inch difference over the 25.6 inch diameter of the smaller wheel. And the speedo should be off by the same amount, assuming it is driven off of or calibrated to the rear tires. If it is from the front tires the difference may be a lot less. Does anybody know?

lawjdc

Are your numbers for the '10 GTRS or for the '07 GT3?

rmag

'10RS. Here's the site to do calculations:
http://www.apexgarage.com/tech/gear_ratios.shtml

Carrera GT

I don't know that you can feel it (at least, I can't feel it when I had a similar difference in a previous car) but the gearing advantage would be quite real and should show up in segment times at points on the track where gearing comes into play. I don't think losing 5 mph in 3rd is going to impact any driving situations and once you're in 4th, it's irrelevant. Overall, I'm surprised it's not more of a detriment.

lawjdc

Thanks - the 4th gear speeds were way too low for an '07 GT3 or RS

GTgears

The difference between a standard GT3 and an RS is about 3 times as great as these differences. This change is way less noticeable than the short ring and pinion being used in the current run of RS cars.

GrantG

You're right, I was thinking about 6th gear...

rmag

Yep! It's taking some getting used to. Agree that 19"-18" is a marginal difference where as gt3 to rs is VERY noticeable I actually prefer the GT3 gearing over the RS for this track. Problem I have is there are 2 straights (one in 4th gear, the other in 5th) where I am within 3-5mph of redline. First event in this car at the that track, so corner entry speeds are probably about 5mph to slow. Once familiar with car I'll probably have to feather throttle at tail end of straights as an additional gear shift will cost more time.