Soft brake feel - causes?

[caseys]

Morning All,

 

It appears my car has 'softer' brakes on it than should be the case. I went from an NA which I put UK front & rear calipers on to a UK with (unsurprisingly) UK calipers on too.

 

I put the braking not being as sharp/good as my NA down to it being a lardy UK spec and the weight difference - but after someone gave my car a spirited drive last time for me he said the brakes do indeed appear to be a bit on the bad side.

 

So what causes soft or detrimental brakes?

 

Points to take into consideration :

 

Flushed and changed brake fluid

Goodrich braided SS brake hoses on it - made some improvement but not much

Changed pads to CW pads and also put in fresh pins, anti-squeal shims, fitting kit etc at the same time as pads and fluid change.

 

The calipers are I believe the original on the car, so possibly just becoming inaffective? I know I can refurb them but doing a search not all parts come in the refurb kit so if it's a piston basically it becomes a bit more hassle? I don't think they're binding or such, after a drive I have gone round to each corner and there's no excessive heat / heat differential, nor does the car squirm at all under braking so bias I believe is ok.

 

The next step I'm taking is to replace both front calipers as I assume they're doing much of the braking force, I also have a brand new set of stock pads, shims, clips which I'll probably do at the same time.

 

I called toyota and also asked for the cost of the brake servo, is the servo and cylinder counted as separate parts? I'm hoping so as Toyota told me the servo is £724.10 EX VAT!

 

Any help on what I should logically try next?

 

Cheers

 

Si

[bignum]

There`s a couple of things to check before you go spending, make sure the pistons are not seized(you should be able to push them into the caliper fairly easy by hand, also have a look at the pad faces to see if they`re "glazed" if so take a some course sandpaper or a metal file and rough them up abit.Also bleed the whole system again.

Edited August 26, 2011 by bignum (see edit history)

[Guest George89]

What disc do you have and have they ever been faded during spirited driving? the disc might be wraped. I had very soft brakes until i changed to a brand new disc and everything felt solid again. Also make sure your brake fluid is topped up.

[Guest George89]

There`s a couple of things to check before you go spending, make sure the pistons are not seized(you should be able to push them into the caliper fairly easy by hand, also have a look at the pad faces to see if they`re "glazed" if so take a some course sandpaper or a metal file and rough them up abit.Also bleed the hole system again.

 

Push the piston in the calliper by hand? i have never heard that one before.

[Dnk]

I think the master cylinder is approx £300. caliper pistons are approx £20 each and i think CW does a st/st option, front caliper seal kit is approx £50 and does both calipers, similar for the rears.

 

I'd check each piston is moving freely 1st on all 4 calipers, you'll need a lever on the pistons if

the calipers are still on the car, be carefull you dont knacker the outer seal.

 

If the outer seals are the original ones then their just about on their last legs if not already in need of replacing.

 

If all the pistons move freely then try re bleeding the system, i use a vaccum bleeder

which works really well.

 

I'd refurb the calipers that are on the car if you can do them yourself, you'll only need pistons if the outer dirt

seals have failed and theres corrosion and pitting on the piston o/d so well worth a look first before you

splash out £400 on a pair of calipers.

The rears will probably be worse than the fronts, mine were but even with one being seized solid it was still fixable

and worked perfectly once it was refurbed with new pistons and seals

Edited August 26, 2011 by Dnk (see edit history)

[bignum]

If they are ok you should be able to push them in holding the caliper(obviously with the pads out and the caliper hanging off the car) and push the piston with your 2 thumbs, i did mine just a couple of weeks ago, saying that i have got hands like a farmer.

[Dnk]

Remind me not to shake hands with you

 

I've only got dainty little fingers but with the calipers off the car i could push

the pistons back in once they were rebuilt but even that needs a good grip

Edited August 26, 2011 by Dnk (see edit history)

[caseys]

There`s a couple of things to check before you go spending, make sure the pistons are not seized(you should be able to push them into the caliper fairly easy by hand, also have a look at the pad faces to see if they`re "glazed" if so take a some course sandpaper or a metal file and rough them up abit.Also bleed the whole system again.

 

I have two bottles of RBF600 sat downstairs flush and change and bleed is happening next week, as well as checking the pads and pistons.

 

What disc do you have and have they ever been faded during spirited driving? the disc might be wraped. I had very soft brakes until i changed to a brand new disc and everything felt solid again. Also make sure your brake fluid is topped up.

 

Discs aren't warped, definitely had warped discs once, I think due to rust on the mounting 'faces' (excuse me I can't remember the term), don't get any judder, nor wheel vibration at any speed.

 

I think the master cylinder is approx £300. caliper pistons are approx £20 each and i think CW does a st/st option, front caliper seal kit is approx £50 and does both calipers, similar for the rears.

 

I'd check each piston is moving freely 1st on all 4 calipers, you'll need a lever on the pistons if

the calipers are still on the car, be carefull you dont knacker the outer seal.

 

If the outer seals are the original ones then their just about on their last legs if not already in need of replacing.

 

I'd refurb the calipers that are on the car if you can do them yourself, you'll only need pistons if the outer dirt

seals have failed and theres corrosion and pitting on the piston o/d so well worth a look first before you

splash out £400 on a pair of calipers.

 

The rears will probably be worse than the fronts, mine were but even with one being seized solid it was still fixable

and worked perfectly once it was refurbed with new pistons and seals

 

As said, the calipers I think are the original UK ones. The caliper refurb kits appear to be £48 from Toyota, I didn't know Chris did a set. How long does a refurb take? As whilst I can put the car up on a ramp, I need to be able to do the job in a day.

 

If they are ok you should be able to push them in holding the caliper(obviously with the pads out and the caliper hanging off the car) and push the piston with your 2 thumbs, i did mine just a couple of weeks ago, saying that i have got hands like a farmer.

 

Ah, I like Dunk, being part asian have small japanese esq hands (which is handy for those hard to reach places in the bay though)

 

Cheers for the advice all, please keep it coming, I will document what I did and what the root cause is so that maybe we can have a guide for what to check - as doesn't appear to be a definitive thread in tech.

[Chris Wilson]

Running anti squeal shims makes brakes noticeably more spongy in feel. You can try running the pads with no shims between them and the caliper pistons, in most instances, with my pads, squeal won't be an issue.

[Dnk]

If you know what your doing and have the required tools then you should easily refurb

both front and rear calipers inside a day.

Obviously im not incuding splitting the 2 halves and powder coating them

 

The only issue would be if you needed any new pistons hence having a good look at them before hand.