Wedge Tr7, Tr8 or SD1 3.08 rear needed....

[tr7andtvr]

The tracks that are near me are Charlotte, CMP, VIR, Barber and Road Atlanta. Charlotte and Atlanta have long straights. I guess I could go back and forth. But I'm thinking the 3.45 with big wheels might be the best option, and it's easy to swap wheels. The car has the older 4 speed style rear end currently therefore it needs to be replaced. Well I say that.... I better check! Nothing else has been correct so far !

 

[tr8todd]

A 3.90 with stock size tire will still get you to 125MPH. Not too many tracks in the country where you can get a TR7 to it's top speed. TR8s yes, TR7s no. Most tracks you spend your time between 45 and 100. You need a 3.90 if you want to get the most out of that anemic 4 cylinder.

 

[cheseroo]

This is a 4cyl? No way do you want a 3.08 for anywhere except Bonneville. I will admit that the Chumpcar MPV for a TR7 is attractive. The TR7 is valued at $100 as compared to my Jag at $275 and my RX7 at $435. The Imp isn't listed but I'm sure it would be close to zero. Chumpcar's goal is to equalize the Animal Farm with a baseline is $500. Anything over is penalized 1 lap per every $10 over the $500. There is a dollar value assigned to performance parts that bump up your value. The list is as long as your car. So with the TR7, you can put $400 worth of (chumpcar valued) parts on your car and not be penalized. For example, a header is $50, non-OE shocks are $100, cam $100, etc. Where I see the problem is that I can't find in the rules where you get bonus laps for being under the $500. They only add laps if you go over their $500 value. I don't see how a legal $500 TR7 is going to keep up with a 91 E30 BMW 325 that is allowed $50 in performance parts. My XJ12 is faster down the straights and slower in the corners than the E30/miata brigade but has overall slower lap times. The TR7 is going to be slower everywhere and since they limit stints to 2 hours, you can't make up time with fuel strategy by long stinting. Everyone is in the same class. This will be a Sisyphus level challenge with a TR7. Our first LeMons race was with a TR7. The car was considered such sh*t that it was given a 50 lap head start on the field. It lost although it scared the crap out of everyone by leading at the end of day 1. I don't believe LeMons ever gave anyone a head start after that.

This bias towards modern performance cars is why I think non-traditional cars like the TR, the Jag and the Imp are better off in LeMons. My RX7 (and the Jag) I will run in occasional Chump events because they can do ok. The Imp stands no chance. But in LeMons, I get to race (cleaner) plus have a shot at a trophy (with the Jag and Imp) because they have multiple classes. The lowest class (where the TR/Jag/Imp reside) is class C but guess what, class C pays better than the overall winner on laps. Plus in LeMons they pay real money, not credits. The Jag won class C earlier this year and made 50% more than the overall winner. The Imp won a subjective award and made 4x as much as the overall winner. In LeMons, the TR is celebrated, in Chump it's laughed at. If you were talking about a TR8 (valued at $200 in Chump), you might have a hope of sniffing at the leaders. The 7 is just going to get smoked in Chump. In LeMons, there's a comraderie when you bring a British car. Strangers will come up and talk to you. heck, even the MG guys will offer you a beer. In Chump, you get viewed as an oddball. It seems like you are deadset on running Chump and I do think you should try both series but my experience with the Britcars has been better in LeMons.


You are going to want the 3.90 and even then you will want to run the lowest profile tires you can find. There's virtually nothing Chump/Lemons legal (180-190TW) in the 13" size, everything is harder. At 14" you have the the S-Drive Yokohama at 300TW (185/55-14). The Dunlop Direzza comes in a 185/60-14 and 195/50-15. All of these are shorter than the stock TR7 tires. You are going to need all the acceleration you can get. The fastest speed I have seen with the Jag in either series is 130. The mazda doesn't seem to get much over 110-115. You don't need the tall gears you are asking about. You want low (high numerical) gears.

 

[tr7andtvr]

I don't think much of old mazdas rx7 or mg's from the same time frame. Although I have a 8 the 7 will dust a B and can beat the rx7. If not the driver of the 7 needs a refresher from skip barber!

 

[cheseroo]

Glwt

 

[andybry2u]

SDI, I believe
But Todd might be correct on the number but his sounds funny
From the TR7 site
And then there's the R380 to that...

Anyway, Mildred asked: "to further sort this issue. Does anyone have the 3.08 differential installed?"

Yes, of course - most all the TR8 have the 3.08:1 rear axle ratio. (Some have the 2.84:1 and a small
fraction, mainly cars built for race or rallye use the '7 ratios...)

My TR8 currently have a R380 gearbox (= 0.77:1 5th gear) and the 3.08:1 rear axle ratio.
[The 2.84 with Quaife is currently sitting in the garage again.) Stock alloy rims with 185-70*13 tyres.
The speedo is off by some kph/mph, I think this was a deliberate oem design decision...

OK Mildred, with the above data (and as close as I could keep your wanted 60 mph with a metricated TR8
(the wonders of GPS!) I get roughly 2290 rpm in 5th gear.

Cheers,
/Odd

Hi there if your interested in selling the 2.84 ratio crown wheel and pinion on a Quaife please let me know
cheers

Andrew