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The mkiv Supra Owners Club

Brake System - expert/experience needed.


Mike B

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I'm experiencing a fairly squishy pedal feel, brakes are good, always work to a good extent, b ut the pedal feel is a lot squishier than the last 2 sups I have had.

 

Pedal hardens and comperesses much further up the stroke one the brakes have been pumped and when hot (trackday) the pedal engages a lot further down the stroke than normal. this is very different to my last sup which had very positive feel, and never altered with use.

 

I also feel that the brakes are slightly out of balance, car pulls right, ever so slightly under hard braking...

 

I have completely changed the fluid today, bled all 4 corners right through, system is exactly the same.

 

Would a new master cylinder help?

 

how does the abs system interface with the brakes - could it be a fault in here?

 

any wisdom welcomed.

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Mike, I'm certainly not experienced, but Chris Wilson and Ian or someone were discussing braking instances the other day prior to Donington. A squishy feeling and a greater force required to get the braking up to scratch apparently indicates boiling brake fluid. I'll try and find it.

 

FOUND IT: half way down matey: http://www.mkivsupra.net/vbb/showthread.php?t=93122&highlight=brake+fluid

 

Perhaps change the type of fluid you're using mate? :)

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Think the stoppers are meant to help reduce/eliminate the movement of the brake servo+master cylinder experienced from the flexing if the bulkhead to which it is all mounted to.

 

So rather than as you press brake pedal a certain degree of additional travel happens cos your flexing the bulkhead the stopper prevents the master cylinder moving so effort is all transferred to braking and not moving the servo+master cylinder assembly............. sorry if that makes no sense what so ever!:)

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Get a Cusco Brake Master Cylinder Stopper fitted to the car, flush the fluid with Motul 5.1 :)

 

:yeahthat:

 

I have one of these fitted, they give a noticeable improvement in pedal firmness.

 

Another alternative is the Carbing tower bar, which has a buit in brace for the brake master cylinder.

 

http://f10.putfile.com/7/18616374710.jpg

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Guest Terry S
Hi Mike,

 

Get a Cusco Brake Master Cylinder Stopper fitted to the car, flush the fluid with Motul 5.1 :)

 

Think Terry had braided lines fitted already, if not get them done too.

 

Gaz.

 

Gaz the car has a Carbing brace with built in Stopper.

 

Mike that is all a bit weird, It has Project Mu teflon hoses on it, check those, if not, a master cylinder my help.

 

Did you put 4.1 in the car?

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Get someone to press the brakes on and off HARD with engine idling, with car on a ramp. Look to see if the calipers are moving AT ALL on their mounts, or the discs are flexing, if so it could very well be a partly seized caliper. If it had stock rubber lines I'd suggest you squeeze each caliper line off, in turn, with hose clamps, and see if the pedal suddenly gets a lot better. if it did that would ID the offending caliper(s). Braided hose CAN be squashed, but it's not good for it, nor recommended.

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Hi Terry,

yes matey - complete fluid change to 4.1, no difference - there is definately something awry somewhere... maybe she is missing your firm hand!

 

All disks are clean and getting pressure... I guess I may follow chris's disgnostics and then may try a new master, as I don't think that they are that expensive.

 

Front brakes are new and came off my last car where they were really good, on here they feel totally different!

 

The reason I asked about the ABS system is that maybe something is wrong in there and this is soaking up the pressure/feel...? stuck caliper would explain the slight yaw under hard braking, but not the pedal feel... right?

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