brake master cylinder/booster size

[bernmc]

I wouldn't think that thin discs would afect the pedal feel - once the pads are up against the disc it should take the same amount of pressure to brake.

Do you know anyone with a brembo'd VR4 that you can compare with? I have a bit more pedal travel than before, but it's not spongy, and stops like @$!£!!

I'll try to remember to measure the EVO cylinder this evening when I get home. You can compare it with the one you have on (but you'll have to take it off to measure the piston... another bleed after that etc).

Just by eyeballing the thing, it didn't look any different from the Leggy's.

Anyone here with a leggie cylinder lying about that they copuld measure and compare with my EVO measurements?

[Gly]

yeh its strange...

when the motors not running, i can pump the pedal and it becomes rock hard,

but once the motors started it becomes all spongie

[Gly]

been doing some reseach

and the evo 5-6 master cylinder is 17/16"
----- (17/16) inch = 26.9875 millimeter

and the vr4 item is 1"
----- 1 inch = 25.4 millimeter


so the bore on the evo item is bigger,
and can push more fluid,



thats a differance of
1.5875mm,

im not sure what the stroke is on the car so can work out how much extra the evo item displaces,

but this may be the issue on my car?! is it significant enough?!


any more input is greatly appreciated




so now im gonna find me a evo5/6 master cylinder!

[Kenneth]

it is the stroke that is important.

The smaller bore means you actually get more pressure multiplication on the pistons, but if the stroke is shorter then you may have issues such as you have encountered. if on the other hand the stroke is longer, then you just need more pedal movement, but get more force on the disks for the pressure you put on the pedal

you really need to find out what the stroke is.

[Gly]

yeh but the stroke shouldnt change if im only changing cylinders,
and the pedal determines what the stoke can/will be.

it will only move as far as it can now,

but because it has a bigger bore and therefore more fluid withinn,
with the same stroke it will move more fluid,
thru the same lines, giving more pressure to the calipers

correct?

[bradc]

Remember as well that the area difference isn't 26.9875/25.4 = 1.0625 ratio, it is 26.9875^2/25.4^2 = 1.1289, which is a sizable difference.

I still think there must be something wrong though, Uc's car isn't like that at all, you and me have both driven it, and the brake pedal doesn't feel like what you're describing.

[Kenneth]

yeh but the stroke shouldnt change if im only changing cylinders,
and the pedal determines what the stoke can/will be.

it will only move as far as it can now,

but because it has a bigger bore and therefore more fluid withinn,
with the same stroke it will move more fluid,
thru the same lines, giving more pressure to the calipers

correct?

it depends on what the standard stroke is on the EVO... what if it has less travel than the Legnum?

The point I am trying to make is that it may not matter, get the bleading done and then see if that helps.

Is the facelift VR-4 master cylinder different than yours? If so, then it might be worth while changing, if not then you shouldn't need too.

Have you looked at the pedals to see if there is any stoppers or anything?

[Gly]

yeh, looked into that,

all the legnum/galant v6/vr4 cylinders are the 1" size

[Gly]

think ive got it now!

my booster/master combo is wrong!,


the brembos are fitted on a v6 leggy,
booster size 7" + 8" with 1" master cylinder,


the vr4s have
booster size 8" + 9" with 1" master cylinder


the evo 5/6 has
booster size 7" + 8" with 17/16" master cylinder


and the 7/9
booster size 8" + 9" with 17/16" master cylinder



so i have to get swap booster or master or both,
cant have all the small items on there!

i hope!

[bradc]

Yeah you've got the small option for both booster and master cylinder.

Do you think changing to a larger master cylinder would affect the performance of a VR-4 equipped with brembo's?

[Gly]

well the evo 7 has brembos aswell,

changing to a larger master, will just mean less predal travel is needed,

im gonna grabs kens spare booster on saturday and see how it goes,
ill take the master aswell, just in case mine is fubar'd

ill just change the booster to start, see how that goes,
if thats no improvement then ill swap to kens master cylinder aswell,

so i can at least eliminate parts,

[bernmc]

think ive got it now!

my booster/master combo is wrong!,


the brembos are fitted on a v6 leggy,
booster size 7" + 8" with 1" master cylinder,


the vr4s have
booster size 8" + 9" with 1" master cylinder


the evo 5/6 has
booster size 7" + 8" with 17/16" master cylinder


and the 7/9
booster size 8" + 9" with 17/16" master cylinder



so i have to get swap booster or master or both,
cant have all the small items on there!

i hope!

Gly, pm this info to physician and get him to put it in the library - it's a useful resource.

[Gly]

done.

[Gly]

just called a couple of places,

manukau mitsubishi,

new genuine evo5/6 master brake cylinder,
$528 + GST ex japan,

kempys,
2nd hand genuine evo 5/6 master brake cylinder,
$120 + GST, availible now

[bradc]

I guess we know which way you'll be going if you can't get Kenneths one working

Are you keen to come out to my place this weekend to do it? Andrew (allbeitmine) is coming out to swipe some stuff from my spare engine, we could have another BBQ and etc.

[Gly]

sorry doing it tomorrow at my dads place,
dont wanna get stuck out in karaka just incase it all turns to ****!

i maybe able to come out saturday avo, but that depends on how the booster swap goes,

gonna try just doing the booster first,
if thats dont solve it, will try kens master cylinder,

after that evo cylinder,

hopefully just the booster will do the trick!

will still get the evo master, just later on down the track.

[Gly]

the story/problems never ends,

anyone got a facelift vr4 chassis # i could use,

have been looking at more brake related parts,
and the brake proportioning valve has a diff part number aswell!


the v6 one is MB699555

and the vr4 one is MB699554

and the evo one is MB699554

[Gly]

what would be more like to cause a soft pedal... (needs to be pumped twice to make the brakes solid?) (when the car is running)

wrong proportioning valve, (the evo 5/6 and vr4 one are the same, mines different but i dont know how different)

too small a brake booster, (i have same as the evo 5/6 one)

or too small a master cylinder, (i have the same as a vr4, but smaller than the evo one)

[bradc]

ec5w-0200998 You really need to write my chassis number down somewhere

If you do come out it would be appreciated, I'm going to be in Newmarket tomorrow morning until about 11am, so I can come and help you out at your dads place if you need any help

[Gly]

oh is yours a late 98 facelift?
thats what caps reports it as be manufactured.. 3/11/98

whats the chassis number on your prefacelift???