Grassroots Motorsports

Subscribe get a full year for only $23.95 Sample Free Test Drive—no strings attached

LeGrand Mk 18 : Real Work Begins Feb 4, 2009

• 
• 
• 
• 

Like many older D Sports Racers, our LeGrand originally came with a locked rear axle, or “spool.” This feature is simple, light and cheap. The downside is that it causes a lot of low-speed push. To solve this problem, modern sports racers use limited slip differentials mounted in custom housings.

We sourced a Wavetrac differential from Autotech Driveline. Meanwhile, we’re having Bill Gendron of Small Fortune Racing make a custom housing for the differential that will be nearly a bolt-on. The housing will include a brake rotor, sprocket and a chain tension adjuster. This modification is the key to making a LeGrand (or any sports racer) turn at low autocross speeds. Bill stopped by our shop and chatted with us while taking measurements for our new rear end.

After our meeting with Bill, we put our car on our Longacre scales to see just how much this little beastie weighs. We were happy to see that we’re at 823 pounds. With our approximately 200- to 220-pound drivers, we’re in the ballpark for the SCCA Solo B Modified minimum weight of 1020 pounds with driver. We’ll have to be careful once we start some modifications—we know we’ll be losing 20 pounds when we change over to the lighter Keizer wheels.

We also played around with the car’s current rear wing. Using a carpenter’s angle finder, we cranked in a 15 degree angle of attack, then added a Gurney flap to the trailing edge. The Gurney flap will help the wing generate downforce at lower speeds and higher AoAs without stalling. Aerodynamics is a fascinating subject—we just ordered Simon McBeath’s book “Competition Car Aerodynamics” to learn more.

• 
• 
• 
• 
• 
• 
• 

---

Comments

thatsnowinnebago:

That green looks fantastic, keep up the good work. What kind of LSD did you get, Torsen, clutch, etc.?
Feb 4, 2009 3 p.m.

Per Schroeder:

It's a Wavetrac, which is a lot like a Torsen T2R (which is a lot like a Quaife with a small friction disk to keep some preload) Per
Feb 4, 2009 7:14 p.m.

thatsnowinnebago:

Ah, I didn't realize Wavetrac was a type of differential, I thought it was a brand.
Feb 5, 2009 1:20 a.m.

Per Schroeder:

It is a brand…and also a type. I like that it's made in the states and pretty reasonably priced.
Feb 5, 2009 10:29 a.m.

nderwater:

It's ironic to think that 823.6 (and more) is a corner weight on most of today's cars, not a total. With slicks, the LeGrand must be a monster in the corners.
Feb 10, 2009 9 a.m.

Per Schroeder:

Yep, as long as the tires are fresh, it sticks like flypaper.
Feb 10, 2009 12:50 p.m.

gerhard_k:

Per - are you saying the new wheels are 5 pounds less than the original LeGrand wheels? That would make those, like, 13 pounds. Really??? I always thought LeGrand's wheels were pretty light…
Mar 13, 2009 10:43 p.m.

Per Schroeder:

It's actually about 4…the LeGrand wheels are 12 for the backs (at least these castings are) and the Keizers are 8.
Mar 16, 2009 4:58 a.m.

You'll need to log in or register to comment.

After our meeting with Bill, we put our car on our Longacre scales to see just how much this little beastie weighs. We were happy to see that we’re at 823 pounds.