Subject: [Fot] Gearing for Lime Rock

From: yellow04 via Fot <[email-masked]>
Date: Thu, 05 Jun 2025 07:51:39 -0400

I have been asked by numerous folks about what rear end gear to run at 
Lime Rock. Several of our guys with a lot more laps at Lime Rock than I 
do have chimed in, thanks everyone for your input. Sometimes a picture 
is worth a thousand words, so here's my input.

https://youtu.be/xIg5KQwM-pw

I clipped a lap from my in-car camera from the 2024 Lime Rock Vintage 
Festival. My tach is plainly visible and I added captions on what I am 
doing with the gearbox. The lap shown is somewhere in the mid-1.05's. 
The camera is one of those Go-Pro knockoffs, so the quality is junk, but 
it got the job done. The sound was cut, if you heard what the camera 
records for sound you would thank me!

The gearing I use in the TR250 is a 4:10 R&P, a Triumph gearbox with 
close ratio gears, a stock Laycock overdrive and I am running on Hoosier 
Speedsters with a diameter of 24.2 inches. My shift point is 6000. This 
example should be easy to reference against your race car assuming you 
are familiar with high school math! This is the same as I used in my old 
TR4 racer and the TR3, except my 4-cylinder racers use a Moldex crank, 
Carillos and a cam that ran to 7000. With the additional revs afforded 
by the billet bottom end, I don't need the overdrive to enhance the top 
end. Again, it's all in the math.

My line through Big Bend and the Uphill are not optimal, but that is a 
conversation for another time.

Watch the tack twitch as I crest the Uphill, you know you did OK when 
you get a little wheelspin there!

Hope this helps.

Henry Frye
KCup chair
860.508.3118
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