Direct 'Dear Dave' tech letters to dave@eyesoreracing.com. Coleman will share mind-numbing details, earth-shattering revelations, and technical nerdisms in this space each month.
Q. College transportation or rally car?
I don't have a car, or even a learner's permit, but I'm lucky enough to drive my parents' car once in a while. I recently turned 16. When I go to college, my parents are promising to get me a new car. I'm looking at the VW Rabbit and Jetta. I'm trying to stick with something practical, but my dream car is a Toyota Supra and I want to build it for drift.
I know the VWs are both front-wheel drive and they can be built as rally cars. I already know all the engine stuff I want to do when I make my purchase, but I don't know how I should tune the suspension for rally.
Would the set-up be similar to a road racing car, as I've seen with Project Corolla and Project Time Attack Miata, or is it more similar to drifting? Also, what kind of tires should I use: soft, medium soft, harder compound? And what tire pressures? I've been thinking about this for a long time, because in rally racing you can both grip corners and drift through them on slippery surfaces. One last thing I need help with is what type of LSD I should use for rally.
I am trying to prove to my friend that front-wheel-drive cars can do just as good in rally as the all-wheel-drive ones.
Dexter Alleyne
Bend, OR
A. Is it just me or is the room spinning?
I'm not sure where the Supra fits into the picture, but rallying your daily driver is a bad idea. You will hit a tree some day. After your first tree hit, it's always more enjoyable to still have a working car the next day. With that out of the way, I'll do my best with your questions.
Although there are occasional tarmac stages, US rallies are almost exclusively run on gravel, so suspension set-up is nothing at all like drift or track set-ups. The rough surface requires a high ride height and soft springs. Also, suspension articulation over uneven surfaces is hugely important, so anti-roll bars are either eliminated altogether, or a smallish one is used on the non-driven wheels, just to trim the handling balance.
Not only does shock valving need to be different, the shocks have to dissipate a lot more heat and withstand vicious loads. Dampers, camber plates, bushings and control arms that can withstand seasons of road racing won't last one 15-minute rally stage.
Tires? That's easy. You need rally tires. Naturally, there are different types for every conceivable surface. Even tarmac rally tires are vastly stronger than road racing tires seemingly engineered for the same surface. Though tarmac stages and race tracks are both on asphalt, road racers seldom jump, ditch hook, run over fist-sized rocks at 100mph or slide through three consecutive corners with all four tires spinning. Kinda makes you wonder why they bother with road racing, doesn't it?
Just like road racing, though, poor guys like you and I can get away with running cheap used tires cast off by the well-funded teams, so don't despair. At least not about the tires.
Unless you're rich, there are only three kinds of tires to worry about. On gravel, run the hardest compound gravel tire you can find so they'll last longer. In snow, get street snow tires, put inner tubes in them, and pump up the tire pressure to the max allowed on the sidewall. In the rare instance of a set of tarmac stages that don't lead directly into gravel stages, you'll need actual tarmac rally tires. I've never been in a rally with enough tarmac to justify buying tires.