Big brake drawback?

[Balazs]

Hi,

I had my front brakes upgraded with Diamante calippers from the junkyard. They were rebuilt before installation. Also one of the rear calippers needed rebuilding. I bought new discs and pads, both in the front and in the rear, and also the brake fluid was replaced, of course.

So basically I have four brand new brakes.

I think the brakes were bleeded properly (first in the rear, then in the front, then the rear again). I took the car for a test drive but I could push the pedal almost completely to the floor (I tried it with and without the ABS). Then all brakes were bleeded again, and some improvement was noticeable (there was a very little air in the rear). Unfortunately I still have to push the pedal much further, then with the old brake.

Is there still air in the system, or it is usual when installing big brakes? Maybe the pedal must be pushed more to move the extra oil that is needed for the +2 pistons?

 

[jott5555]

try useing this and bleeding it.. http://www.bmw-m.net/TechProc/bleeder.htm

it may help a bit.. and the order in which you want to bleed is rear passanger, rear driver, front passanger, front driver..

do this multiaple times.. do not switch back and forth..

 

[Balazs]

Thanks for the info, every brake was bleeded about 5-6 times, before we bleeded the next one, but there still must be air somewhere.

But if everything is fine, is there any noticeable change on the pedal when switching to big brakes? Now I have to push it about 1,5-2 inches further...

 

[Darksyne]

and the order in which you want to bleed is rear passanger, rear driver, front passanger, front driver..

do this multiaple times.. do not switch back and forth..

Thanks for the info, every brake was bleeded about 5-6 times, before we bleeded the next one, but there still must be air somewhere.

Just a heads up. According to the factory service manual the proper order is:
Passenger Rear > Driver's Front > Driver's Rear > Passenger Front

I was only able to get a firm pedal after following the order I just posted.

Here's a screenshot from the service manual

 

[FORMONTOYA]

According to the factory service manual the proper order is:
Passenger Rear > Driver's Front > Driver's Rear > Passenger Front

this is correct. after doing this properly you should have at least the same 'feel' as you had before (as weird as it might seem, the brake circut is diagnal_2 circuts, look at the illistration). it does not matter if you have 10 piston calipers it should feel the same or better. the more pistons you have the greater surface area you have to push against which 'binds' up the pad/rotor which would mean less force applied for the same amount of 'bind'. the pedal travel should actually be a little less since you have new pads. if it goes further, then there is air in the lines.

one thing to get better 'feel' and firmness from the brakes is the braided lines (the weak link). you will really be surprised how much the rubber flexes in the factory hoses.


jim

 

[Balazs]

Thank you guys for the answers.

 

[jott5555]

thats weird... i always assumed ut was the other way.. must be the way the porpurting valve is set up