OK so our new car is up and running. We have not seen a dry day since the car is running, so we have NOT tested in dry conditions. On the other side, till this week, the last 2 years were very dry and we hadn't run in the wet for almost 2 years, so this means maybe I don't remember that our 2008 prototype (the last one I drove in the rain) also did this. Did it or did it not, I don't think it's acceptable.
Here is the problem. You are approaching a braking point, and as soon as you brake hard the rear end starts to sound clack clack clack real hard, the whole car starts to shake real hard. Rear tires lock up and then get loose and lock up and get loose.
Nothing of this happens if you use the clutch (obvious, just wanted to clear that out).
The outer CV joint (Taylor race) has some freeplay in the hub (in our design, the CV joint couples into the hub itself), but the 2008 prototype (which we tested a month ago in the DRY and showed NO signs of this wobble, none of our cars have ever showed this, you can see the video searching for F-SAE MARZO on youtube) has a lot more free play (LOT of miles on that car) and has never shown this, neither did the 2009 prototype. The braking disk (2 piston caliper with floating disk) has the same freeplay in the pins as it did in previous prototypes (the freeplay recommended in Tune to Win or something like that). The hub has no play at all in any direction, and the hub-wheel coupling is very tight. Caliper mounts are the practically the same as in 2007, 2008, and 2009 and they are TFT so that is not the problem.
If you turn the engine off, stop the car and shift to 1st gear, and start to push the car (normally it would stop wheels blocked by the gearbox) the wheels will do just what I explained before, try to turn, then block and slip, then try and turn again, and then block, all of this with the axles not rotating at all.
In normal braking situations we have always shown a slight clack clack clack in our previous cars, when downshifting, but with no problems at all, and we think it's the combined movement of the chain and gearbox free play, or something like this in the drive train, but nothing like this, I mean our 2008 and 2009 prototypes are pretty good cars both finishing in the top ten in AutoX in MIS.
We have tried various brake balances and even increased the rear end wheel travel in rebound, but the problem stays the same. I'm starting to think it is just the grip conditions in the wet and the slip ratio admittance (in wet conditions you loose grip really fast when slip ratio decreases, when you start to block the wheel), and I'm praying to the racing gods that we don't see that in the dry, hopefully tomorrow morning. So, I wanted to know if any of you guys have felt this wobble in your car, and if luckily for us you did, how did you solve it. I wanted to know if you have any suggestions or theories of what it could be, anything would help.
Thanks in advance and if you have any additional questions about the problem I can answer them all.