borat52

I have a 1993 impreza WRX, JDM.
I've never really been happy with the brakes on it so just had a new set of 6 pots and 330mm discs put on the front.
Although the stopping power from high speed is greatly imroved I'm still not happy about the way the pedal feels, My brother has an FTO dad has a GTO and also a pajero. All of these have a distinctive feel in so far as the pedal is light for about half an inch and then suddenly becomes harder with a lot of braking force for little foot effort.

The pedal on my impreza is pretty hard from word go and needs a lot of force to apply a decent braking force. Its mostly in traffic lights where it drives me mad. Does the impreza have servo assited brakes? Do all pedals feel like this?

cheers
will

StickyMicky

try having the brakes pressure bled, my mate at quick fit does this for me, they clamp a new cap over the reservoir and force fluid through the system, this gets any trapped air out the system.

you may also have a problem with your rear calipers, did you check them?

theotherphil

Did you also upgrade the brake lines to braided hoses?

gaz-cole

the problem sounds to be elsewhere but remember the bigger the front brakes the more fluid needs to be pushed into them before you get a good feel, also may sound daft did you bleed the back brakes aswell have you checked them to see if they are free and unseized aswell as the sliding brakets you could try putting brake pipe clamps on the back to see if the pedal is stiff on the front and then vice versa only when stationary of corse, and lastly some cars you can adjust the amount of travel on the pedal not sure about these models not had a look but might save you some hassel, also about the servo turn your engine off and when you push the brakes you when get a couple pumps of the pedal with a dull hiss noise and then after you have done this hold your foot on the brake pedal with firm pressure and start the engine if the pedal sinks the servo is ok, normally if the servo had gone you would know about it

Chelspeed

> but remember the bigger the front brakes the more fluid needs to be
> pushed into them

Not necessarily, the more pots the smaller each one is so 6 small pots on AP's may be the same volume of fluid as 4 bigger pots on the standard caliper.

Lets check, 6 pot diameters are 2 at 27mm, 2 at 31.8mm, 2 at 38.1mm. Total area is 5013mm2.

Assuming piston movement is the same for all (might be double on single pot sliding type) then we can easily check. Anyone know piston diameters for 4 pots and single pots?

gaz-cole

it was just a maybe from the way the problem has been described it could be 1 of 10 problems and comparing brakes from different manufactures isnt really a reliable comparison

Tazz Kill Er

I've been trying to find out similar data on this thread

https://www.scoobynet.com/brake-mast...r-t548076.html

what would be good to know is the master cylinder piston diameter.

i want to know if the master cylinder can cope with the bigger brakes if i upgrade my classic

Tazz Kill Er

Just found that the piston diameter on 4 pots is 40.4mm giving atotal piston area of 5128mm2

richiewong

IIRC Subaru's aren't over servo'd (sp) in the brakes so require more 'push' then the on/off feel of some cars.

borat52

rear brakes are working fine, the pads/discs are very worn though. I have a replacement set which I'm getting fitted next week. Ive had the system bled twice now and a set of stainless hoses all round fitted.
Its probably as you said, the brakes on the mitsi's I have metioned are very much an on/off feel, the subaru is different, I quite like the on/off feel with a brake pedal though.
Hopefully a new set of discs/pads on the rear will help things as well as bedding the fronts in properly.
thanks for the input.

Chelspeed

> Just found that the piston diameter on 4 pots is 40.4mm giving atotal piston area of 5128mm2

Marvellous many thanks. I rest my case! In theory you need a bigger master cylinder for standard brakes than 4 pots. But in practice the difference is small so the standard m/c will do for both.

Wonder Wagon

Could it be the brake pad compound?

borat52

been from greenstuff to DS2500's lately, and now to wilwood BP10 pads with the new calipers. Rear discs/pads are properly shot now though. Left rear is scraping on the disc and making a horrid noise. Have new calipers/discs/pads for the rear, getting them fitted next week.
I'll update this thread with the results.

TTZZ

I now drive a forester 2.5xt, this is a big improvment on brake scompared to my old my98 impreza turbo.
But after driving my friend audi A6 this weeken,it was a complete shock when I hit the brakes of my forester again.
The pedal went down to the floor in my opinion, no braking.
Yes the subaru's have poor brakes.
To improve the stiffnes, you can try a larger mastercylinder, use a mastercylinder brace
change the hoses tot braided steel hoses.
And for more cold bite, change the pads for pagid blue rs4-2
Regards JE

Jay m A

iTrader: (2)

Don't you also have to consider the internal design of the caliper fluid chamber?

I would imagine total fluid volume of a 6 pot caliper (not just the pots) would be larger than the equivalent 4 pot