Brakes Wheels 2nd Gen Tires Most liked posts in thread: Turns out the rears lock first

Yeah I would have gotten an F on my exam (did vehicle dynamics in college) if I had proposed a system that locked the rears first.... I think the modern abs systems cover a lot of non standard baseline biases that flat out woun't fly on a car that didn't have abs.

I have have massive front rotors (328x28mm) that should have biased more to front if anything. I could run less aggressive rear pads but the rear rotors get hot enough to need rear track pads so :fingerscrossed: into the braking zones :crazy:

 

Ugh looks like it was the controller not the sensors aka $$$ not quite able to justify a 15k bosch motorsport unit but still not a cheap part :-/ oh well such is the cost of beating on the car!

 

Oh snap I should have know to ask. I actually just dropped the mini at the shop as I am recovering from a motorcycle crash (it was at the track so full leathers etc means just a dislocated arm and a few tiny things which more annoying than anything, obv can still drive the mini but I am favoring my stronger arm) and the garage is full of motorcycle bits and while I am almost back to normal (~85%) the crazy contortions needed to work on the mini seem like unnecessary risk till i am 100% again. I appreciate it though, will definitely ping you for spares next time Are you doing the trackdaze event at VIR in Nov? I will be there.

 

Thanks man, been doing the car thing for years but still got tons of noob level stuff to learn on the bike side but it is making me faster in the car as the weight transfer and need for smoothness is 10x higher! See you there! :cornut:

I even run stiffer springs in the front to counter this effect somewhat (to the slight detriment of handling). I am pretty sure it is a fact of the system relying on the abs module to control line pressure. Without that, way too much pressure gets sent rearward. When functional my rear brakes last 4x longer than the front brakes because there is so little going on back there. On a car without abs you have to use a prop valve or similar tech to mechanically limit the line pressure the rears will get so you don't have the bias changing with abs fails, meaning the fronts will lock first always. I would be shocked if a car with fully functional brakes had the rears lock first. When stuff breaks that obviously goes out the window.

 

Yeah that is why I thought my bigger front rotors would have resulted in it being harder to lock the rears.... maybe i should cut the rear pads in half haha. I know a few teams have done that in the fast to reduce rear brake bias and stay within the rules

 

The mini has a 4 channel ABS though so line pressure won't be the same at each wheel, Yes, it is a closed system but there are multiple lines. Line pressure won't be the same front and rear even on non-ABS cars, a proportioning valve or similar tech will prevent that specifically to account for the weight transfer. There are even standard equations that help you figure out what spring strength to put in your system. There are a ton of inputs cg, rotor dimensions etc. but it is fairly basically to figure out what the safe max line pressure is for emergency braking. I agree with the physics I am just disagreeing that it isn’t already accounted for in mass produced systems unless someone screwed up big time. If an engineer showed me a braking system that had equal power front and rear when functioning as intended I would be shocked. Weight transfer has to be accounted for in the system design or everyone would have to be a finnish rally driver!

Here are few quick reads that might help:
http://www.drivingfast.net/technology/abs.htm
https://en.wikipedia.org/wiki/Proportioning_valve