[Mk2] [Generic] Rev 1 to rev3 brake upgrade

[xavier]

If you know how an ABS functions, you will know that the maitre cylinder is not used for the pressure of braking:

MC -> ABS -> Pressure 4 wheels

and

diameter piston MC - > 7/8 (rev1)
diameter piston MC - > 15/16 (rev2++)

Tiny difference

[cantfindausername]

In my experience the ABS is a ring of sensors that release the clamping force momentarily and not one that applies different braking forces to each wheel.

And yes, there is a tiny difference, but it is a difference none the less. The question was not is there a difference, but can I fit one whithout braking issues - to which the answer was - you wont have braking issues but you will have to work the pedal more - smaller piston will require more actuation to move the same amount of fluid as a bigger piston. That has nothing to do with ABS. Its a simple fact.

[pintovit]

So TNM, you should be the man to set this!

How is the build going? Also interested in the outcome, since I own a rev1 as well and the upgrade would be welcome!

Good luck mate!

Cheers,
Vítor

[Dame]

Actually the ABS pump does control the pressure exerted on each wheel. Simply put it works like this:

There is a valve in each brakeline (to each wheel) that will occupy three possible positions. 1. open to allow pressure from the MS into the brake clamping the wheel, 2. block to stop any further pressure being applied or 3. release which releases pressure from the brake claiming the wheel.

Since the valve is able to release pressure from a wheel, it also needs to be able to reapply pressure without intervention from the driver. This is the job of the ABS pump which reapplies a calculated amount of pressure to the brake.

In this way, the MS does not really control the amount of pressure applied to each wheel since in theory this job could be carried out exclusively by the ABS pump. The reason why the system is setup in this way i.e. with the MS sometimes providing the pressure instead of the pump is to give the drive the impression that the braking system works in the same way as a conventional system.

In fact the reason why you feel pulsing through the pedal when your ABS is operating is because the pump is automatically applying and releasing pressure.

HTH.

[cantfindausername]

You learn something everyday.

[Adam J]

This is providing you have ABS! If he does not then the MC does control it.

[Dame]

This is providing you have ABS! If he does not then the MC does control it.

well yes obviously ....

[HighwayStar]

Just wondering if any of the affiliates out there offer this upgrade as a standard service at a standard cost (or 2.... ABS and non ABS). Or if they have plans to?
Also will this conversion produce better results than simply upgrading standard rev1 brakes with carbotech pads and braided hoses which I guess would be substantially cheaper? Anyone out there with a view on this or done the latter?
Cheers
R.

[3sgte]

just to throw another spanner in the works

it is commonly thought that the rev2+ brakes need more fluid to make the pistons move the same amount .
i just wonder how this can be
the rev1,2,3,4,5 calipers all share the same pistons ,regarless of the overall size of the caliper
now since the caliper will obviously need more fluid to fill initially when bleeding .the actual amount of fluid to move the piston the same amount IE toward the disc will be the same

i fitted rev 3 brakes to my rev1 and noticed no change to my pedal .the only difference is the rev2+ brakes larger MC gived you less pedal travel ,which would mean that the force to move the pistons would have to be applied over less distance ,meaning that the pedal may move less ,but will need to be pushed harder . I would also imagine Toyota changed the servo to provide more vacum assistance on the rev2+ cars to counteract this disadvantage

also if anybody is intersted i have got a rev2+ master cylinder for sale for an ABS car(shameless plug )

sorry for the long post

Marc

[3sgte]

ok just checked the epc


front pistons, the same throughout revisions
back pistons, different part number
brake booster servo , different part number

so if the back pistons are very slightly larger they are only 2/6 of the entire system so would make very negligible difference

i still blieve the changes were made by toyota from rev2 onwards were just to reduce travel ,and provide more assistance for the brakes to counteract the increased force needed

and that rev3 brakes do not need more pedal travel when used with rev1 MC

[garbe]

How can I tell if the front calipers are rev2+
I know the rears have 22V stamped on them.

I bought a set but the guy had so many on the shelf, I know i got the correct rears, but when checking the fron they looked similar

[TheRoadWarrior]

The main reason the calipers were changed was to accommodate thicker discs (30mm at the front and 25mm at the rear) If you look on camskill they have pictures of the rebuilt rev1 and 2+ calipers which shows the difference.

[garbe]

Thanks did just that, the rev2+ fronts have a larger vent hole in the top of the caliper