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Author: Subject: brakes getting worse after 4-pot istallation
alfas

posted on 3/8/18 at 09:33 PM Reply With Quote
brakes getting worse after 4-pot istallation

Locost m16 front, drum rear, unknown tandem master (looks like fiesta), cheapish aftermarket pads...brakes ok, good relation between effort and travel

changed m16s to hi-spec 4-pot M16, EBC standard pads

pedal has now slightly more travel but in the same time the efficiancy dropped
after the pedal travel comes to the end the pedal gets rock hard, but i dont feel that the brakes really bite. if feels like you need to push the pedal so hard until your master cylinder will snap.off the fixing bolts.

had a similar issue once on a sylva striker which came with such Hispecs, and EBC green stuff pads.
i changed them against the M16s of my other locost.....sylva fine, but locost, even it had a bias pedal box, became bad (identically like above with my actual locost)

any advise what i may do wrong?

(bleeding is not the issue!!!)

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rodgling

posted on 3/8/18 at 10:07 PM Reply With Quote
Perhaps less piston area in the new calipers, therefore less mechanical advantage? Check the dimensions, if that's the case then try a smaller master cylinder.
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alfas

posted on 4/8/18 at 06:01 AM Reply With Quote
the 4-pot M16 replacements should have more piston-area than the standard 2-pot M16...at least i hoped that...now im a bit confused and checked again hispecs homepage...and now found an option on the order-form to choose between 27, 31 or 34mm piston size....which i wasnt aware when ordering a few months ago, where i was supplied a pair of calipers whith a set of pistons of unknown size....(???)

which is very strange....as such a well known company would not supply a random piston size i guess?



the theory says: larger piston surface = increased brake power = longer travel of pedal

and the pedal travel has slightly increased after the new calipers had been fitted.

upon reversion this means the piston area must have increased

so im even more confused now



[Edited on 4/8/18 by alfas]

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mcerd1

posted on 4/8/18 at 06:35 AM Reply With Quote
braided hoses don't always make much on a difference, rubber ones are all reinforced anyway

Are the new pads properly bedded in ?

Personally I always thought that greenstuff pads were pretty rubbish
(managed to have a set smoking in 10min on a 45hp car)





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alfas

posted on 4/8/18 at 06:39 AM Reply With Quote
as im mainly missing the bite on those brakes you might be right that i need experiment with the pads rather than with the hydraulics....
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Bigboystoys

posted on 4/8/18 at 08:18 AM Reply With Quote
I run hispec rs4 on the front of my dax with ferodo ds2500 pads and my brakes are amazing.
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CosKev3

posted on 4/8/18 at 08:42 AM Reply With Quote
EBC pads have that initial 'running in' coating IIRC?

In our light cars it will take a fair few miles to wear threw that coating IMO before you get the proper bite of the pads

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alfas

posted on 4/8/18 at 10:02 AM Reply With Quote
with 2 track weekends that coating should be gone already.....
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OliilO

posted on 4/8/18 at 02:24 PM Reply With Quote
Is it that due to the increased piston volume, you need to push more fluid volume for the same effect which is why your brake pedal is going further into it's travel with less braking effect?
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CosKev3

posted on 4/8/18 at 04:12 PM Reply With Quote
quote:
Originally posted by alfas
with 2 track weekends that coating should be gone already.....


Went straight on track with new pads?

Could have glazed them?

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alfas

posted on 4/8/18 at 04:15 PM Reply With Quote
quote:
Originally posted by OliilO
Is it that due to the increased piston volume, you need to push more fluid volume for the same effect which is why your brake pedal is going further into it's travel with less braking effect?


larger piston surface = increased brake power = longer travel of pedal

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alfas

posted on 4/8/18 at 04:16 PM Reply With Quote
quote:
Originally posted by CosKev3
quote:
Originally posted by alfas
with 2 track weekends that coating should be gone already.....


Went straight on track with new pads?

Could have glazed them?


its a car without rosd registration.....just for the track.....brakes where not stressed in the first sessions....

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OliilO

posted on 4/8/18 at 04:29 PM Reply With Quote
quote:
Originally posted by alfas
quote:
Originally posted by OliilO
Is it that due to the increased piston volume, you need to push more fluid volume for the same effect which is why your brake pedal is going further into it's travel with less braking effect?


larger piston surface = increased brake power = longer travel of pedal


Whoops. Misread the original post; I read it as getting through all the MC travel before the brakes achieved any effect, rather than just a slightly longer stroke with less efficiency...

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MikeRJ

posted on 4/8/18 at 09:59 PM Reply With Quote
quote:
Originally posted by alfas
the theory says: larger piston surface = increased brake power = longer travel of pedal

and the pedal travel has slightly increased after the new calipers had been fitted.

upon reversion this means the piston area must have increased

so im even more confused now



Extra pedal travel could be caused by other issues, e.g. still some air in the system, or caliper is not being held perfectly parallel to disc so is flexing, or maybe the seals in the HiSpecs naturally pull the pistons in a little further than the M16.

You need to determine the piston size in your calipers; the fact that the pedal goes rock hard and you get little braking effort strongly suggests you have less piston area. To match the piston area of an M16 caliper (piston diameter 54mm) you would need four pot calipers with 38mm diameter pistons, so it seems that HiSpec don't actually have a direct replacement.

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Benzo

posted on 5/8/18 at 11:30 AM Reply With Quote
What pads had you previously?

Ive just bought a car with EPC pads in it all around and the brakes are horrific.

I will be changing back to DS2500 ASAP same as my previous 7s!

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rdodger

posted on 5/8/18 at 12:47 PM Reply With Quote
You say the pedal come to the end of it's travel and goes rock hard? Is it actually coming to the end of it's travel and therefore can't travel any further or is it just getting so hard you can't press it further?

I had my pedal go to the floor under maximum pressure with Willwood calipers. I changed the master cylinder to a larger one and hey presto great feel and confidence.

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alfas

posted on 8/8/18 at 08:00 AM Reply With Quote
it gets rock hard approx in the midlle of the possible pedal travel

there is deinately no air in the system

what i find strange that the caliper is offered as a M16 replacement caliper even it does not match the orignal spec in terms of braking power.
this said, which manufacturer of alloy calipers is offering the "correct" size of M16 replacement?



anyway....i will change the pads first....

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alfas

posted on 4/10/18 at 09:50 PM Reply With Quote
finally changed pads to well known quality brand...and brakes have improved....furthermore the car is now staying in-line during braking, whereas with the cheaper pads it was always pulling to the right.
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