Smaller brakes
- Thread starter katnip
- Start date
RallyGuy24
New member
Preping the STi for some gravel time??? Yay!
I am guessing the ABS will need to be adjusted, but this is a guess. Maybe the ABS measurement is based on a certain circumference (i.e. distance traveled per rotation), which has now changed:idk:
edit--actually, just pull the ABS fuse and get the CEL delete. Who really wants ABS with threshold braking....
edit--actually, just pull the ABS fuse and get the CEL delete. Who really wants ABS with threshold braking....
Last edited by a moderator:
Redline
Member
I'm guessing the ABS sensor, but not because of distance traveled. The amount of brake surface area has changed, so has your overall stopped power. The pressure you are able to apply to the brakes is now concentrated on a smaller area, thereby creating more PSI on that smaller braking surface instead of being distributed over a large area.
I'm not sure what the ABS sensor measures exactly. I'm guessing there is a longitudenal motion sensor, that tells the computer that you are still in a forward/backward moving motion, and that your stopped wheel shouldn't be stopped. The computer then releases break pressure (pulsating break motion) and re-applies it as needed. However, I'm not convinced that it actually measures the PSI in the line or any combination thereof.
Someone who knows ABS systems will need to chime in. I'd be interested to know precisely WHAT the ABS system measures, other than forward/backward motion.
I'm not sure what the ABS sensor measures exactly. I'm guessing there is a longitudenal motion sensor, that tells the computer that you are still in a forward/backward moving motion, and that your stopped wheel shouldn't be stopped. The computer then releases break pressure (pulsating break motion) and re-applies it as needed. However, I'm not convinced that it actually measures the PSI in the line or any combination thereof.
Someone who knows ABS systems will need to chime in. I'd be interested to know precisely WHAT the ABS system measures, other than forward/backward motion.
RallyCat
Member
Grossly oversimplified, but ABS measures the relative rate of rotation of the wheels. When it senses that one (or more) wheel is spinning significantly slower than the others, it "releases" the brake pressure on that wheel to get it spinning again.
Are you changing only the front brakes? If so, then you'll probably need to mess around with the front/rear bias. If you leave it alone, you may end up with too much braking power in the rear making for some not so fun braking characteristics. This may also be necessary for a complete brake swap (it would not surprise me if the bias was different for STI brakes versus WRX).
There may be some tweaking to the ABS system involved, but I don't recall ever hearing that was necessary. Just have Alan rig up one of those nice little ABS kill switches like he had in the WRX for you.
Tim
Are you changing only the front brakes? If so, then you'll probably need to mess around with the front/rear bias. If you leave it alone, you may end up with too much braking power in the rear making for some not so fun braking characteristics. This may also be necessary for a complete brake swap (it would not surprise me if the bias was different for STI brakes versus WRX).
There may be some tweaking to the ABS system involved, but I don't recall ever hearing that was necessary. Just have Alan rig up one of those nice little ABS kill switches like he had in the WRX for you.
Tim
I can't comment on downsizing directly.. but there have been tons of people to install the STI brakes onto WRX cars without issues involving ABS... just ask your seller.
The bias will certainly be effected, but it seems the popular opinion that the STI has too much front bias in stock form, so you may not even notice or possibly enjoy the difference.
TheNailman
Warcock
different caliper bolts though. i overlooked that prior to my swap.
