I agree

The primary problem with the R888, other than NASA's handling of the "transition", is that they don't last as long. While it can be an issue if the tires are slower or not, it's really not such a big deal if everyone is actually using the same tire, and if they were to last as long as an RA-1 did.

is the shorter tire going to make the short fifth a requirement ? seems like it's a nice to have at most of our tracks but a shorter tire might change that. ?

SvoChuck wrote:


The shorter tire will impact gearing. Not sure how much, but we will use 5th gear more I would guess. The other thing is I would expect a 225/50 RA-1 to last longer than a 205/50 RA-1. This is due to the wider 225 tire. Also a change in tire size may require FURTHER set-up changes. We can't expect a 205 RA-1 to be the same as our beloved 225 RA-1. Somethings to consider.

SvoChuck wrote:



Yes, our gears will effectively be shorter, so we'll run through them faster and use 5th more.

Specs from Toyo's website...

225/50-15 R888: 22 lbs, 23.7" dia, 9" tread width, 875 revs/mile

225/50-15 RA-1: 23 lbs, 23.9" dia, 9" tread width, 886 revs/mile

205/50-15 RA-1: 20 lbs, 23.1" dia, 8" tread width, 917 revs/mile

I'm not sure how the RA-1's get more revs per mile than the R888's while having a larger diameter, but whatever... it's close enough.


944 Gear Ratios...

1st: 3.6000
2nd: 2.1250
3rd: 1.4583
4th: 1.0714
5th: 0.8286 (short 5th; long is 0.7297)
FD: 3.8889

Rev limit is approx 6500 RPM.


1st Gear Shift Point:
6500 Engine RPM / (3.6000 * 3.8889) = 464.284 Wheel RPM
464.284 * 60 = 27857.04 Wheel Revs Per Hour
27857.04 / 875 = 31.84 MPH on 225-wide R888's
27857.04 / 886 = 31.44 MPH on 225-wide RA-1's
27857.04 / 917 = 30.38 MPH on 205-wide RA-1's

2nd Gear Shift Point:
6500 Engine RPM / (2.1250 * 3.8889) = 786.552 Wheel RPM
786.552 * 60 = 47193.12 Wheel Revs Per Hour
47193.12 / 875 = 53.93 MPH on 225-wide R888's
47193.12 / 886 = 53.27 MPH on 225-wide RA-1's
47193.12 / 917 = 51.46 MPH on 205-wide RA-1's

3rd Gear Shift Point:
6500 Engine RPM / (1.4583 * 3.8889) = 1146.145 Wheel RPM
1146.145 * 60 = 68768.7 Wheel Revs Per Hour
68768.7 / 875 = 78.59 MPH on 225-wide R888's
68768.7 / 886 = 77.62 MPH on 225-wide RA-1's
68768.7 / 917 = 74.99 MPH on 205-wide RA-1's

4rd Gear Shift Point:
6500 Engine RPM / (1.0714 * 3.8889) = 1560.037 Wheel RPM
1560.037 * 60 = 93602.22 Wheel Revs Per Hour
93602.22 / 875 = 106.97 MPH on 225-wide R888's
93602.22 / 886 = 105.65 MPH on 225-wide RA-1's
93602.22 / 917 = 102.07 MPH on 205-wide RA-1's


The indicated speed on our speedometers will be higher than these actual numbers, because our cars originally came with larger tires than what we are racing on.


Although the differences here are only a few MPH, it is a decent impact for our ~130 WHP cars.

The more we have to use 5th, the more it hurts those of us that do not have the short 5th gear, even if mathmaticaly the long 5th is shorter.

We just got hit with another reason to abandon 225/50-15 tires... The price has gone up. Chris found that our local dealers are now wanting around $162-167 per tire for RA-1 or R888 in 225/50-15.

I see even higher prices at online retailers like aimtire.com: www.aimtire.com/typ_category.asp?Unique=...33&ObjectID=6650

As of right now, aimtire.com wants $178.75 for 225, but 205 is only $139.00. That makes 205's $159 cheaper per set! I know that 205's are a hard sell for us because of the 5th gear issue, but with a price difference like this, the cost of a short 5th tranny is really becoming less of an issue.


For comparison, you can get 225/50-15 Kumho V710's for only $156.00 from TireRack.com, and those tires are a lot faster. Part of why I gave up a high-HP car on V710's to come race a 944 on RA-1's was because I was sick and tired of burning through tires so fast. But now I'm faced with the fact that V710's cost less than R888's, and we're going through 225-wide R888's almost as fast as I went through 205-wide V710's on a car with twice the HP. That just doesn't seem right for a class that wants to be low cost.