Formula B4 brake pressure?????? « Singletrack Forum

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Formula B4 brake pressure??????

11 posts & 5 voices | Started 10 months ago by vonnoelio | Latest reply from vonnoelio

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vonnoelio - Member

Hi there,

I recently purchased a used set of B4's off of Steve(sleigh62) on here. They are an old set of brakes and have managed to free up the pistons and get them moving in and out. I have re-bled the lines and while I have lever pressure, the pads grip on half travel on the lever and full grip at full travel.

My interpretation is that I need more pressure in the system, I believe I cant be losing pressure as (1) the pistons would not return and (2) they would get progressively worse.

Any ideas?

Cheers
Noel.

Posted 10 months ago #
brant - Member

Have you tried lubing up with Piston Grease?

Posted 10 months ago #
18bikes - Member

Brant's onto something there, that stuff solves quite a lot of issues

Posted 10 months ago #
vonnoelio - Member

Cheers Brant and 18bikes, I will try and get some piston grease and give it a go.
Whilst anything to help the action on the pistons would be good I dont understand how this will increase the resistance on the lever itself???

I am a relative newbie when it comes to this sorta stuff so if I appear ignorant apologies all round.

cheers
Noel.

Posted 10 months ago #
compositepro - Member

This is another one of those threads where clear concise instructions would be the order of the day!!! Pictures on how to use piston grease would also be usefull as the OP says hes new to all this ,I think just for those of us who are unsure on how much to use and if there may be clearance issues upon insertion of the piston ...should you wipe off the excess?

Posted 10 months ago #
clubber - Member

they're taking the piss. sounds like you have some air in the system so you'll need to get them bled. mtb brakes aren't pressurised as such.

or lube yourself up with piston grease. up to you

Posted 10 months ago #
18bikes - Member

Clubber is right, sounds like air in the system, bleed the brake and then lube the pistons using either brake fluid or silicone lube, NOT piston grease (google it if you really want to). Use the brake lever to force one piston out at a time (holding the other back with a tyre lever), apply your chosen lubricant to a cotton bud, wipe around the piston and push it back with a tyre lever, repeat for the other piston. Wipe away any excess (this applies for piston grease too ;)) We recommend doing this when changing pads to prevent pistons seizing

hth
Matt

Posted 10 months ago #
vonnoelio - Member

Compositepro thanks for the reply. So far I have had the pistons out and have given them a v. light sand with some high grade wet'n'dry. They have gone back in nice and straight and I do have some movement both back and forth. I will try some piston grease as I dont believe it'll do any harm, make sure I take off any excess.
Clubber, I am with you I think, however I have bled them already and I believe all air is out of the system. My thoughts are it must be an air in the system problem! I need more pressure in the system which should give me more resistance on the lever, right?

Does anyone know if there is any adjustment on the levers, as I have heard that some levers have this? Would this help in this instance?

I think my course of action will be:-

1 - grease pistons
2 - rebleed system
3(?) - replace reservoir
4(?) - new hoses

Cheers
Noel.

Posted 10 months ago #
vonnoelio - Member

Cheers 18bikes, I'll pick up some silicon lube. As to all your instructions I have done this, hopefully the addition of the lube may help but I agree on the air issue. That just makes sense to me.

Noel.

Posted 10 months ago #
clubber - Member

one thing that may save rebleeding. use an elastic band on the bar/brake lever to hold the brakes on hard and leave overnight with the bike the right way up. ideally tap the caliper with a spanner or simlar.to try and free.up any air bubbles. then remove the reservoir cap and elastic and cycle the lever. you may well see a load of air bubble out. top up the reservoir and refit the cap.

Posted 10 months ago #
vonnoelio - Member

Cheers Clubber,

have put on the rubber band and will check when home from work.

nice one.

Posted 10 months ago #

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