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spongy brakes
beaver34 - 9/4/12 at 06:27 PM

just changed my front brakes from m16 calipers to a set of hispec 4 pots

the pedal is more spongy now not driven the car at all, is this normal with a 4 pot brake having 4 pistons and more power? or will it get better one they are used

i bled it and there is no air in the system and the rest of the system is unchanged

thanks for any input

CRAIGR - 9/4/12 at 06:32 PM

Assuming you have replaced the pads with new ones it will feel spongy until the pads bed in.

Ben_Copeland - 9/4/12 at 06:33 PM

New pads may give a little spongy feel, get the bed in first and see whats what.

beaver34 - 9/4/12 at 06:35 PM

quote:
Originally posted by CRAIGR
Assuming you have replaced the pads with new ones it will feel spongy until the pads bed in.


yeah ok sounds fair enough,

ashg - 9/4/12 at 07:53 PM

i know its a daft question but did you bleed both nipples on each calliper?

beaver34 - 9/4/12 at 08:02 PM

quote:
Originally posted by ashg
i know its a daft question but did you bleed both nipples on each calliper?


Yep, although not much air in them to be fair, I'll see if it's front or rear the spongyness is in but sure it will be the fronts

britishtrident - 9/4/12 at 08:23 PM

Alloy 4 pot (or more ) light alloy calipers tend to trap air but they also less ridgid and flex under pressure a a lot more than 2 pot or single pot steel callipers.

To get rid of the air try taking one pad at a time out pumping the brakes a little to get the pistons just over half way out then push the pistons back in repeat for each pad and calliper.

They are also more prone to the calliper not being properly aligned with the disc which will cause spongeyness.
To check for this pump the pedal a couple of times to put the pad in contact with the disc then use a thin feeler gauge to check for uneven gap between the pad and the disc. If presents the pad to the disc is even at a small angle or is tilted you will get spongeyness, the cure is careful hand fettling and or shimming of the lug-brackets on the upright.

[Edited on 9/4/12 by britishtrident]

[Edited on 9/4/12 by britishtrident]

beaver34 - 9/4/12 at 09:35 PM

quote:
Originally posted by britishtrident
Alloy 4 pot (or more ) light alloy calipers tend to trap air but they also less ridgid and flex under pressure a a lot more than 2 pot or single pot steel callipers.

To get rid of the air try taking one pad at a time out pumping the brakes a little to get the pistons just over half way out then push the pistons back in repeat for each pad and calliper.

They are also more prone to the calliper not being properly aligned with the disc which will cause spongeyness.
To check for this pump the pedal a couple of times to put the pad in contact with the disc then use a thin feeler gauge to check for uneven gap between the pad and the disc. If presents the pad to the disc is even at a small angle or is tilted you will get spongeyness, the cure is careful hand fettling and or shimming of the lug-brackets on the upright.

[Edited on 9/4/12 by britishtrident]

[Edited on 9/4/12 by britishtrident]


The caliper are direct fitment and seem to sit straight but will check that,

When you say take a pad out and push the caliper back in do yo open the bleed nipple or let it push the fluid back up the system?

Thanks though

tasmod - 10/4/12 at 12:38 PM

Take care if pushing pedal with pad missing, it's so easy to exceed the seals.

I had similar problems with mine, two things helped, shimming the calipers and careful pad bed in. Must admit though I'm still not happy with mine compared to the M16 calipers. To be honest the M16 was just as capable as the 4 pots to lock the wheels, with more feel.

I had a rolling road session done at Andy Nobles years back and he commented on the large size of the M16's compared to weight of the car. I tend to agree with him now, it was overbraked even then.

procomp - 10/4/12 at 02:18 PM

Hi

What size pistons are fitted to the Hispec units. ? Do you require a master Cyl change to go with the new setup. Do you have a twin cyl setup to be able to adjust the bias to suit properly. ?

Cheers Matt

beaver34 - 10/4/12 at 02:50 PM

Hi Matt,

Running a twin setup as it is, not sure on the piston size I'll email them and find out,

Didn't spec the master it came like that so will check with guys who built it

beaver34 - 10/4/12 at 06:55 PM

took some pics tonight, would the way the brake hose goes create a air lock with it going from the top in?






owelly - 10/4/12 at 07:52 PM

One of those piccies gives the inpression the pads are not square in the caliper wgixh suggests its not square to the disc or the disc isn't seated square to the hub?

The Venom Project - 11/4/12 at 09:30 AM

I have the same problem, Hi Spec 4 pot calipers front, standard R1 caliper rear, when I push my foot on the brake it takes one full push to the bottom and then once I push again, they are fine. My calipers are new, new pads, I thought I had all the air out of the system, there must be air still in, I did only open one side of the front caliper nipples, is this half of my problem?

Does anyone recommend the auto bleed kits?

It is generally me doing this on my own, I can get help, but an auto kit helps me do it faster.

I have taken the face of the pads, so don't think its got anything to do with new pads, as after its first full push, they are excellent.

Any help would be great

Cheers

Nick

[Edited on 11/4/12 by The Venom Project]

beaver34 - 11/4/12 at 12:12 PM

my understanding was if it pumps up on the pedal then its air in the system that needs removing out, 2 person is the best way to do it as far as im aware

mine does not change dependant on the pedal pumps its stays the same, i rebled it again and its no better, will look at pad contact but to me it looks spot on

The Venom Project - 11/4/12 at 12:34 PM

Im sure can make it much better, just ordered a 1 way valve kit for £7 inc postage with a clear tube, the guy reckons its an easy 1 person job, no opening and closing of the nipple, just connect, open and pump, sounds very rude :-)


So will await this and see if I can make it better. Always worth a shot, and I will post my results or failures

beaver34 - 11/4/12 at 01:49 PM

failing that we can console each other

scudderfish - 11/4/12 at 01:55 PM

If the piston area is greater on the new callipers, you'll have to push the pedal further to exert the same pressure if you haven't changed the master cylinder. However you'll be exerting the same pressure over a greater area to get a greater braking force.

Regards,
Dave

The Venom Project - 11/4/12 at 02:06 PM

quote:
Originally posted by beaver34
failing that we can console each other


it must be achievable, we are not the only 2 kit car owners who have had this and still have it as an issue.

Will let you know

If I sort it, bring yours over and we will sort it ;-)

Nick

beaver34 - 11/4/12 at 02:25 PM

quote:
Originally posted by The Venom Project
quote:
Originally posted by beaver34
failing that we can console each other


it must be achievable, we are not the only 2 kit car owners who have had this and still have it as an issue.

Will let you know

If I sort it, bring yours over and we will sort it ;-)

Nick


you bring your over, mine dosent work!

The Venom Project - 11/4/12 at 02:40 PM

Cool, sounds like a plan

Nick

tasmod - 12/4/12 at 07:38 AM

Solid pedal after first pump sounds like piston retraction as fluid drains back. If calipers are higher or same plane as m/cylinders this is possible.

Maybe need a 2lb residual pressure valve for the fronts to keep pistons out.