LSD recommendations for stock m42

[Bizzyboy904]

I know there is a 4:10 lsd available for these cars, but has anyone had any different ratios that felt better with the 5 spd. This car will be a daily driver that will eventually have 16in wheels (stock 14in bottle caps now.)with a decent sized side wall if that will make any difference. te reason I want an lsd is because I am starting to do auto cross.

[M42Power]

I cant tell you about lsd's but i run a 3.64 small case diff in my car and it is plenty of fun to beat on it. For auto x you have the added benefit of being able to hit 60 mph in second.

[G FORCE]

Subscribed for further info.

[Ocell]

I run a 4.1 LSD in autocross. I've never hit my rev limiter in second, but I do run out of first gear very quickly. I kind of like it because I can get my shift out of the way early. I think our course designs can be fairly fast, too. The gearing also feels decent on the couple tracks I do. It's a bit high on the highway, but it's nice to be in the power-band when I'm looking to pass someone.

I'm running 15" wheels with 205/50R15 tires.

Here are a couple videos where you can see my tach, if that helps.

[AndrewBird]

Wheel size will have no effect on rolling diameter. Tires are what determine your rolling diameter. If you go to a bigger wheel, you will need to have a tire with a shorter sidewall to make up for it to keep the same rolling diameter. Here is a good tool for figuring out what tire you will need:

http://www.miata.net/garage/tirecalc.html

[Bizzyboy904]

u makes i use the maths. u bad man make my head hurt!

225/45/16 is what the calculator says is equal to my stock rolling diameter. Not wide enough to warrant the heavier wheel. I plugged in some wider wheels and it threw every thing off, I think I will just stick to 4:10 the car doesn't make power until 4k anyway.

[jalopi]

For figuring out your wheel/tire package:

http://rimsntires.com/specspro.jsp

http://www.willtheyfit.com/

For getting a good idea of what your new top speeds in each gear will be, where you'll be at in the powerband, ect when changing rears:

http://www.teammfactory.com/gear-calculator

[mr.vang]

Get a 2.73 differential and get 35+ mpg on the hwy.

[Bizzyboy904]

seems like i would stall out in 1st gear WOT

[wazzu70]

I couldn't imagine anything less than a 4.10 for autocross. A 4.27 would probably be even better. 3.73 is the highest gearing I would consider to get a highway cruiser/reasonable acceleration.

[Dj Buttchug]

yea for auto x you will want 4.10 at least. Good news is a medium case 4.10 LSD can be had pretty easily around here for like 300 bucks + or - a few.

[TobyB]

there are 4.44 small case gearsets kicking around, too, if you REALLY like to r3v...

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[SmokeE30]

There's also supposed to be 4.88s available as a e30m3 optional ratio

[wazzu70]

There's also supposed to be 4.88s available as a e30m3 optional ratio

Yeah, its a mororsport ratio though so its incredibly expensive and rare.

My car has the equivalent of around a 4.44 ratio (an E36ZF and 3.73 gearset). Its a lot of fun :) I dont think there is much of a need to go steeper though.

[jntar]

I prefer the 4.10. Where I live we have two autocross locations. A very small course and a very large course. The small course i never leave second gear and only on a rare occasion bounce off the limiter. The large course I do switch between second and third, but the 4.10 is still well within the power band. I run a shorter tire than stock 205/50R15, so if you're closer to stock size you'll be slightly lower in the revs, which would be good as well.