10 replies to this topic

[Mario]

I'm no expert on car physics or racecar set-up for that matter, but I do know that break bias is towards the front as weight is transfered to the front of a car under braking. Are there any conditions in which brake bias would be set-up to the rear, say 45-55 or 40-60? Or is brake bias generally set to the front? If possible, hypothesize the type of brake bias employed for an F1 car at Interlagos.

Thanks

[blkirk]

The only time you would want a rear brake bias is in a tail heavy car with bad brakes. The bias is determined by the weight balance of the car at maximum braking since this is when the most weight is on the front wheels. You want a bias that is a bit greater than the weight balance at that point. As an example, if the car is 45-55 normally, but 60-40 under braking, then you would want to set the brake bias to something like 62-38. The reason for this is that locking the rear brakes will instantly spin the car, so it's best to give the driver a bit of a margin of safety. The size of the margin depends on the driver.

As far as what they used on the cars at Interlagos, I have absolutely no idea. It depends on tire choice, downforce, wheel base, CG location, and driver preference. If I had to hazard a guess, I'd say somewhere around 60-40 to 55-45.

[Bluehair]

In addition to front-rear bias, there is also a very small left-right bias to be taken into consideration. Prior to the race at Brazil they mentioned that at an anti-clockwise track, the left front would try to lock up more frequently than the right front and so it's disc and calipers could be slightly smaller/lighter. Not much, but some measureable amount. The opposite holds true of most clockwise circuits. Of course we're really splitting hairs here but it just shows how much detail that goes into these cars!

[Manson]

In the wet, the drivers tend to use more rear bias to prevent the fronts from locking up on corner entry. Less speed/less weight transfer to the front = more rear brake needed.

As far as left front to right front is concerned. In some oval track series, they run more LF brake so that the car pulls to the left under braking and handle better apparently. Dirt sprinters in the US use no RF brake at all (no caliper, rotor, nothing!). Personally I like the car stable under braking and not jerking one way or the other.

[Mario]

Manson,

More rear bias as in more than 50% to the rear? If so, that is interesting.

[Engineguy]

Originally posted by Mario
Manson,

More rear bias as in more than 50% to the rear? If so, that is interesting.

I assume he meant "more rear bias" to mean less front bias than normal. If you were expecting zero weight tranfer you might approach 50/50, but, having been up close and personal to both F1 and CART cars running in the wet, I can vouch for the fact that they are still getting serious weight tranfer. I always assumed they pussyfooted around in the rain until I saw them in person... they are still braking pretty hard.

[BRG]

The only application for serious rearwards brake bias that I can think of is gravel rallying, where you want to lock the back wheels to get the car sideways. Even then it is not more than 50% to the rear. This suited the old rear wheel drive rally cars (Escorts etc) and is still useful for current front-wheel drive cars to help to overcome their inherent understeer. The top level 4WD WRCars still use some rear brake bias on gravel, but less than the 2WDs.

[imaginesix]

Originally posted by blkirk
The only time you would want a rear brake bias is in a tail heavy car with bad brakes

Precisely.

I don't know much about drag racers, but they seem to fit the above description. So if they even HAVE brakes front and rear, then I would have to say that they also have >50% rear brake bias.
More likely so for the highest-performance category of dragster, whatever they're called.

[Bluehair]

I think I have one little case for rear-brake bias: Assume that the bias is changed by the driver a couple of times per lap (say during qualifying). Assume also that there is a place on the track that has a steep incline during braking. If this were the case, with most of the load on the rear, you would also want the braking force back there. I don't think any such section of track exists on the F1 tour, and I doubt that drivers would want to fidget around with the brake bias every lap, but I thought I'd throw that out there just for SAG (since abbreviations are so popular, I'm sure you can all figure that one out).

[DangerMouse]

you could also switch all brake bias to the rear when exciting turns to turn left foot braking into a form of traction contol. The FIA are banning electronic brake distribution systems in 2002,

[Alien]

Originally posted by Bluehair
I think I have one little case for rear-brake bias: Assume that the bias is changed by the driver a couple of times per lap (say during qualifying). Assume also that there is a place on the track that has a steep incline during braking. If this were the case, with most of the load on the rear, you would also want the braking force back there. I don't think any such section of track exists on the F1 tour, and I doubt that drivers would want to fidget around with the brake bias every lap, but I thought I'd throw that out there just for SAG (since abbreviations are so popular, I'm sure you can all figure that one out).

In Austria A1, there are a couple of uphill braking zones that may encourage drivers to set the rear bias a bit more to the back, i do that on my sim