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Hi spec rear brakes


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Hi All,

having fitted new rear 2 pot hi spec Iva brakes I have struggled to get a peddle.

My front hi spec 4 pots use banjo type fitment for the flexi hose, I used the same set up for the rears. I had M16 rears and although not great always stopped the car.

I suspect that the rears are a standard hose fitment but can’t for the life of me find a resource from hispec which confirms this.

Any info would be gratefully received - talking to hispec is usually a waste of time...

Thanks again in advance

Craig

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Unfortunately there is only one guy at Hi-Spec who knows his stuff.

Back when I was building my car I quickly gave up with them, but they were selling rebadged Wilwood gear.

I got all my stuff from Rally Design, who were always happy to chat over options, but more importantly steered me away from some of my own ideas.

If this is your caliper (I cant see any other 2 pot calipers) their description shows M10x1

http://www.hispeccalipers.co.uk//ultralite-2.html

 

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Interestingly having just spoken with Hispec, they tell me that the standard fitting is a banjo as I have. However, the chap did say that it wouldn't matter if I had a standard 10 x 1mm fitting either so a bit miffed you could say. 

So, when bleeding the brakes I use the Gunson kit and put 20 lbs of pressure through the system to check for leaks. I have no leaks. I bleed all four corners, the fronts from the inside out and the rears tops and then bottoms although the chap from Hispec says only the tops need bleeding.

Any one have any ideas as to why I have no brake pedal despite having new 4 pot fronts and new 2 pot rears with new flexi hoses front and back with no leaks?

Currently I have put 1.5 litres through the system to flush out all of the old fluid. Following each bleed of all four corners I try the peddle which feels good. After several pumps, the brake pedal just sticks all the way and does not return giving me no pedal.

Cheers

Craig

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Only the top bleed screws need bleeding. The other 2 are only there so you can mount the caliper either way up.

Start with the simple possibilities. Is the brake pedal itself binding on its bearings? When it sticks down, try pulling it up by hand.

I assume you do mean it sticks down?

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With no leaks I would suspect the master cylinder is passing a bit each time and not returning properly on release.

20psi resets the pistons in the MC.

Has the MC been assembled without internal return springs?

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Hello and thank you to all responders. I’ll get back into the garage tonight to see what’s occurring. Thank you so much for your suggestions, gratefully received.

MC was not stripped as only 1028 miles from new. That said, I’m not ruling it out for replacement. 

Im fairly sure I have a return spring on the peddle but can’t quite remember - it’s an age thing...

It’s what the happy people at hispec said about the bottom screws, many thanks for the clarification though - experience tells me that it’s a bit of pot luck with getting the correct information out of them - thanks 

I’ll check and come back with findings.

Cheers

Craig

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  • 3 weeks later...

So, my trusty Sierra MC had corroded and had a score to  the primary end of the MC. So out with the old and in with a new collected from GBS.
Now bleeding with Gunsons ezibleed! 
while I realise that it is best to bleed the MC on the bench, I decided due to space and not wanting brake fluid every where that I install and bleed in the car. Well I’ve now put a litre through, lots of air out and have a peddle which goes all the way to the floor. While I know there is a marmite attitude to these one man bleed systems I don’t have a choice - it has to be a one man job. As such is there a specific way in which this should be approached? I’m bleeding off side rear, near side rear, near side front and lastly offside front. As mentioned I put a litre through it yesterday and had clear fluid no bubbles.L but peddle all the way to the floor.

in light of above, just wondered if there was anything I was doing wrong.

Cheers

Craig

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Try testing the MC by fitting blead nipples to all outlets and bleading each. If this does not work you have another duff MC.

If it does work try connecting the ports one at a time and bleading untill you find the problem circuit.

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I would only use those eazibleeds to get the initial fluid into the lines, I'd then move to the more "manual" approach. I don't know the reason why this happens, but I'd guess it's because of air pockets maybe in the moving parts of the system (pistons) that you're not moving when you use an eazibleed? Sometimes it's a bit trial and error but I find pumping the pedal (on closed bleed nipples) sometimes consolidates air in the system, and likewise the old bleed pipe into a partially-filled recepticle really helps you visualise how much air is still in there. Surely you can find someone to sit and press the pedal for half an hour :) ? As said above, start with the longest run of brake pipe (normally nearside rear?) and work your way down to the shortest (normally offside front?)...

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Just a thought, you now have 12 pistons needing fluid in a system designed for 6? The master cylinder will have to travel further to supply more fluid to the extra pistons causing longer pedal travel. Perhaps it’s time to upgrade the master cylinder if you haven’t done so already.

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