So, how wold someone go about turning the LeGrand roller above into a BM car? One way to get started in BM is buying a car that is already prepped and set-up for BM autocrossing. Although quick and convenient, the problem with that is that there are not much more than a handful of cars in existence that can go out and be competitive. Therefore, the next best thing is buying a BM-eligible platform and do the prep-work yourself.
Older sports racers are common starting points for a competitive BM car. However, most of them have older engines and might be a little tired structurally from years of roadracing. That's where this LeGrand does have a leg up. I have not seen the car, but, just based on the description, it should be structurally very sound since it is essentially a new chassis. The only track-time this car has ever seen is one autocross event. Ever. Other than the engine, it is complete and even comes with two sets of wheels that appear to be the right size (the most common set-up is 8x13" wheels in the front and 10x13" wheels in the rear). Therefore, you would not pay for an engine that may eventually come out of the car anyway.
Ok, let's assume you bought this car, all you'd have to do to get that car on track is installing an engine. In order to be competitive, a good option would be a mid-2000s fuel-injected 1000 cc motorcycle engine. 2005-2008 Suzuki GSX-R 1000 engines are very popular options. This is pretty much what's required for the 1000 cc motorcycle engine installation, along with estimated costs:
- Engine, $2000-3500
- Oil pan (required to lower engine and assure proper oil supply in a car application), $500-800
- Fuel pump, $80-200
- Fuel pressure regulator, $100-180
- Header (the motorcycle header won't work due to its routing); this one is a little more tricky and I have to recalibrate myself on what's available, parts kits are available in the $300-400 range, ready-made headers up to $2500
- Misc. items: throttle cable, clutch cable (unless the engine has a hydraulic clutch), a new chain and a smaller front sprocket for a better gear ratio
- Fabricating and welding in engine mounts
Now, with the engine installed, you are ready to go and run the car in A-Modified. Why AM? There are two reasons:
- BM has different minimum weights for different engine sizes. For a car with a 1000 cc 4-stroke engine, the minimum weight is 1020 lbs, including driver. The LeGrand was designed as a very lightweight car for the SCCA DSR class that had a minimum weight of 900 lbs. The car in this configuration could be less than 750 lbs and would definitely require ballast for most drivers to make the car legal in BM. Scrap lead works well and can be had for cheap.
- BM also has a minimum wheelbase requirement of 80" to prevent ultra-small cars. The LeGrand was designed with a 78" wheelbase, which means it needs to be stretched. This could be done in three different ways, either by relocating the front wheels, relocating the rear wheels, or lengthening the chassis. The most common way of doing this would be relocating the rear wheels through a suspension modification. The material to do that is probably no more than $100, but a bolt-on kit, which is available, would cost significantly more.
With those modifications, the car would be ready to run in BM, but there is more needed to make it competitive. The two items required to make it a front-runner are:
- An LSD. The older cars, including the LeGrands, where typically built with what's called a "spool", basically a rigid connection between the two rear axles. That does not allow the two rear tires to run at different speeds when cornering, which guarantees understeer. The spool needs to be replaced with a differential. A Quaife or Wavetrack differential (the VW Rabbit fitment is very adequate) runs in the $900-1000 range. Other options are available. This is just for the naked differential, and packaging is the challenge. "Kits" are available that run in the $3000-5000 range, and minor fabrication and welding might also be required. Depending on the fit, modifications to the axles and CV joints may or may not be required.
- A Solo-specific rear wing for adequate downforce. A well-designed wing is very effective and can drop your times by two seconds or more, depending on the course and the surface. A competitive 2-element wing can be had for $2000-4000. Another options is building your own for a few hundred dollars worth of material. Some minor fabrication may be required to mount the wing.
Now, you have a car that can be a contender and front-runner at pretty much any event. A little more tweaking and tuning would make this one of the fastest cars in the country.
You probably noticed that I mentioned the words 'fabrication' and 'welding' several times. If you have the skills and equipment to do those two things, it clearly makes these modifications a lot cheaper, basically the cost of the material. Having a friend who can do these things is the next best option. Having to pay a "professional" for this work makes it quite a bit more expensive.
So, there you have it, one route to owning a competitive BM car.