Ring and Pinion Ratio

Greetings all,

Im looking to get some opinions for R&P ratio selection from those that have or are currently using their car for dual purpose racing. Back story is that I recently sent my Staffs gearbox off to TRE to have some repairs made to the selector finger bores on the bearing carrier and my pinion gear was found to be in poor shape. I am contemplating changing from a 10:31 to a 9:31 and was curious if that has any implications if I make the financial mistake of road racing the car in the future :rolleyes:.

I currently have a 15:36 (2.400) first gear putting top of first in the neighborhood of 60 MPH at the Honda rev limit; I imagine this is probably higher than most. The issue I have with the Staffs is that I dont think integral 1st gear input shafts were made for the 4 speed configuration of the gearbox. The 15:36 I currently have I lucked into getting from Lee Williams from a previous special build he had done. Essentially if I want a different 1st gear ratio I have to convince someone to make one for me.

I previously justified the gearing by saying I lose more time in a run for other mistakes than I would gain off the line or in the occasional slow corner. But looking at the bright side of things the pinion condition presents the perfect excuse for me to change to a 9:31 ratio to bring me back into normal range for autocross 1st gear (~55 MPH by my public school math). I have a selection of ~20 gear sets ranging from 17:34 (2.000) through 26:25 (0.962) to use for either application.

Any comments are appreciated.

Matt Boian
14 CM

Quote:

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Originally Posted by mboian90

I have a selection of ~20 gear sets ranging from 17:34 (2.000) through 26:25 (0.962) to use for either application.

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Matt,

Given the above statement (i.e. having gear sets for both Solo and Club Racing), I would go with the 9:31.

After 4 years of running Solo with the 10:31 (and a 13:38 fixed first) in the DB1, I switched to the 9:31. With the 9:31, speeds shifted downward ~5 mph across the range making a noticeable positive impact on the performance of the car.

Take care,

Yes, integral 1sts and even integral 1st & 2nds were indeed made for the 4 speed ( I was the original importer). 12/36 or 12.38 were the common 1sts, if I remember correctly. Somebody out there may have one that they are no longer using.

No idea if the new Staffs manufacturer still makes them.

Quote:

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Originally Posted by R. Pare

Yes, integral 1sts and even integral 1st & 2nds were indeed made for the 4 speed ( I was the original importer). 12/36 or 12.38 were the common 1sts, if I remember correctly. Somebody out there may have one that they are no longer using.

No idea if the new Staffs manufacturer still makes them.

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That is an interesting piece of information. Did the original shafts that you imported place the integral 1st in the middle top "2nd gear" location of the shift pattern?

I had talked with TRE about using one of the Atlantic style integral shafts that puts first at the bottom left of the pattern and blocking out 5th to keep it a 4 speed. I wasnt fond of the idea because I wanted to keep the shift pattern the same. Mostly I wanted to keep the 1-2 shift on the same shift rail for autocross. I had also looked at the integral 1st and 2nd (again Atlantic style) with the idea of blocking out 1st and just using the 2nd but I think the ratios choices werent any better than what I have.

Quote:

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Originally Posted by mboian90

That is an interesting piece of information. Did the original shafts that you imported place the integral 1st in the middle top "2nd gear" location of the shift pattern?

I had talked with TRE about using one of the Atlantic style integral shafts that puts first at the bottom left of the pattern and blocking out 5th to keep it a 4 speed. I wasnt fond of the idea because I wanted to keep the shift pattern the same. Mostly I wanted to keep the 1-2 shift on the same shift rail for autocross. I had also looked at the integral 1st and 2nd (again Atlantic style) with the idea of blocking out 1st and just using the 2nd but I think the ratios choices werent any better than what I have.

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The 4 spd integrals had 1st in the normal position, and the 5-speed was different.

Quote:

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Originally Posted by R. Pare

The 4 spd integrals had 1st in the normal position, and the 5-speed was different.

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So looking back at some of my notes I may have remembered wrong. The issue may not have been the 4 speed vs 5 speed but MK5 vs MK9 gears. All of the gear sets I have are MK9 size and I think the only layshafts I was able to find were with the larger MK5 spline pattern. I could have gone that direction but didnt want to buy new gear sets for 2nd through 4th. Apparently I was being really picky...

Sounds like a 9:31 isnt readily available right now so I am going to start looking around again to see what I can find.

The DB-6 basket case that I bought obviously was run for a whole weekend with no oil in it. So, I bought a new Staffs box, with an eye toward running both road races and autox. TRE then prepped it for me. The whole process took 6 months because it was not in production at the time. It was also Not Cheap.

Road racing requires a 10:31 final for a low drag car. I ordered an integral 13:38 1st gear layshaft for autox in addition to a conventional layshaft. That results in 49 mph at a Honda engine redline.

So, an integral 1st can be had if you are patient and willing to pay.

I'm thinking that it really doesn't matter what 2nd or 3rd gear you may have, because it's going to come what your comfortable with, if you go up and down the grid you will hear different thought process from the 3rd to 4th only shifting (3rd speed unknow) to shifting only to 2nd gear that go's to 72 mph and then a 2nd to 3rd shifting point, to living with a 1000 rpm drop to a 1500 rpm drop AND then you could own a Honda which throws everything out the window.

Now the new talking point is First gear and a 45 mph to a 50 mph and a 53 mph which is better, I'm not sure? I'm going to do some testing with the 12.38 and a 13.37 fixed first with a 10.31 ring gear in a 60 foot times, so which will pull a better 60 foot time and so on.

Just thinking out loud and I Really like my ratio's at this point and so I'm going to wait until after I do the 12.38, 13.37 60 foot times and see if there is a ten or 2 to make.

Ben

Ben,

I fall in the category of only using 1st and 2nd because of the tall first. In the 3 years I have had my car I have only actually needed to shift it into 3rd on one course. I think it runs out to a little above 75 MPH. 3rd gear is a running joke between myself and JD (codriver you talked to on the phone) because I used to say at every event "I think I might actually need third on course" and then never get close to it. There have been a number of tight courses where I havent got out of first. When I bought the car liked it because I was moving from a bone stock ES miata on all season tires to a CM. Keeping the car on the course was enough work for me so not having to worry about shifting too much was a good thing. Im now wishing I had something like you mentioned where I still mainly just use a 1st and 2nd and have a 3rd to pull across the line.

Matt Boian
14 CM