spridgets
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RE: Dif for racing

To: dmeadow@juno.com
Subject: RE: Dif for racing
Date: Thu, 15 Aug 2002 10:52:00 -0500
Cc: spridgets@autox.team.net
> -----Original Message-----
> From: David C Littlefield [SMTP:dmeadow@juno.com]
> Sent: Tuesday, August 13, 2002 7:05 PM
> To:   John.Deikis@med.va.gov
> Subject:      Re: Dif for racing
> 
> Err, didn't you say in another post you had a Spec-Sprite?  If so, then a
> few things come to mind:
> 
> 4.22 is the required diff ratio, so if you use something else you are not
> Spec-Sprite any more.  However, that's something that would probably only
> matter to you.
        [Deikis, John]  Right!  Don't matter to me.  Car came out of the
showroom with the 3.9 so I run a 3.9.  But on short tracks, it's too high.
Your comments about tire diameters remind me that my question was pretty
dumb and that lots of variables effect true final ratio.  Would love to swap
pumpkins on the same day at the same track, but don't know if I have the
ambition!

        On a philosophical note:  I'm running "Rustbelt Spec Sprite".  The
RSS formula is "modify as little as you can stand to, run the DOT tires that
happen to be on your wheels or that you can get on sale, and if you pull
away on straights, LIFT!  It's not the race, it's the dice that makes the
fun.  ;-)

> The diameter of your tires is important in determining which rear-end
> ratio you should use, as is the type of gearbox you have.  For example,
> when my car was Spec-Sprite the 4.22 rear-end worked pretty well for even
> a fast track considering that the spec Firestone tires are relatively
> tall. 
> 
> When I went to a smaller diameter road race tire, Yokohama AO32R's, I
> found the 3.9 more appropriate for the faster tracks such as Road America
> and our home track at Texas World Speedway.  For the Hallett, OK event in
> October I'll switch to a 4.22.  That track is very twisty and hilly with
> one short straight.
> 
> Throw into that mix the fact that I also put a close ratio, straight cut
> gearbox in the car.  Now I'm in third gear most of the way through the
> TWS course with upshifts to fourth only on the straighter bits.  A friend
> with a nearly identical car (Spec-Sprite engine, Yokohama tires, CR box)
> ran out of revs on the straight with his 4.22 while I was still pulling. 
> In Spec-Sprite trim (Firestones, 4.22, standard box) I was in fourth gear
> most of the way 'round the track and didn't run out of revs on the
> straight. 
> 
> Whether a 4.11 would be a good ratio depends on your car and the track
> you typically run on.  The only way to know for sure (IMHO) is to run the
> two different rear ends on the same track under the same conditions and
> see if your lap times improve.  
> 
> David Littlefield
> 1962 MGA MkII
> 1974 MG Midget vintage racecar
> 1951 MGTD
> 1961 Jaguar E-Type OTS
> 
> 
> On Tue, 13 Aug 2002 17:41:27 -0400 John.Deikis@med.va.gov writes:
> > Okay, Spridget racers-- here's a $0.02 opportunity for you.
> > Generally, the 3.9 diff is considered too high for Spridgets at most 
> > tracks.
> > Seems a lot of folks run the 4.22.
> > Crunching numbers, It looks to me like 4.22 is pretty low.  Anybody 
> > have an
> > opinion on running a 4.11 rear (originally fitted to the Nash 
> > Metropolitan)?
> > 
> > --JohnD

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