Front brake lever free play

I'm putting together a curvy as a trackday bike and having cleaned up the calipers and fitted braided lines I have a concern about the front brake. After bleeding the lever can be pulled solid so I know there's no air in there, but the initial travel is too much, the lever moves about an inch (even on max span adjuster) before it bites, meaning in use it's much too close to the bar. Any ideas?

[Adam Ef]

Are your pads new or worn?

[andy650]

Air or spongy lines

The pads are used and bedded in to the discs. The lever isn't spongy, it just has too much initial travel.

[ophic]

Worn piston seals can retract the piston too far off the disk resulting in too much movement. Try replacing these.

[Tannoy964]

Originally Posted by Tomcatracing

The pads are used and bedded in to the discs. The lever isn't spongy, it just has too much initial travel.

I had a similar problem with the front brakes on my 2002 track bike which I recently build. I serviced the callipers fitted braided lines, dot 5.1 fluid, new pads and bled the system to within an inch of my sanity....and is still had a level (on setting 1) that basically ended up being able to be pulled back to the bar (and a bit spongy). Very disappointing for its first outing, Anyway, I now have a lever that stops about 30mm from the bar (not great but a lot better). How? When I got the bike back a mate came over and suggested the following: Unbolt the callipers (leave the brake lines attached) then remove the pads. Take the master cylinder off the bars and lash it up on a temporary set up so it faces up hill (banjo bolts down). Remove some of the brake fluid carefully with a syringe (this goes back at the end) then one at a time push each piston (starting with LH calliper) in then pump it out (not all the way!) with the lever CAREFULLY , then push in again and repeat a few times then repeat on calliper No. 2 (we put something the the other calliper when doing this to retain the pistons). No bleeding involved and no obvious signs of air coming out (couldn't watch the reservoir all the time so there may have been the odd bubble?). Anyway as I say, when it all went back on there was a big difference in the feel. I'm not saying this will cure your problem (everyone has their own preferred brake setup method) it' just seemed to work for me. As a belt and braces approach I've also ordered some levers off the bay...they may offer a wider span range...or maybe not! but they weren't mega bucks.

Thanks for that tannoy but I have a nasty feeling ophic is right, I had a similar problem with the pointy I raced at the Manx in 2010. We cured that by changing the seals, which was a right PITA, so I was hoping there might be some easier options to try first. Reverse bleeding could certainly be helpful if it was spongy, but it's not. So I guess we'll see how we get on with the seals

[Bibio]

define 'cleaned up the callipers'?

Originally Posted by Bibio

define 'cleaned up the callipers'?

Literally that. They were crusted in years of brake dust and the last owner had slathered copper grease all over the pads. So I degreased them with cellulose thinners and scraped off the clag. Worked the pistons so I could see they were free, I guess not free enough though

[Bibio]

copper grease eats rubber.
thinners eats rubber (to a point)

you cant free sticky pistons by pumping them in and out. pistons stick or seize due to the build up of the aluminium oxidising at the back of the seals, this forces the seals to grab the pistons more. before we now know better the workshop manuals and common practise was to install piston seals with brake fluid, we now know that the brake fluid being hygroscopic attracts moisture which is the main cause of the aluminium oxidising in the seal recesses. when assembling brake calliper seal/pistons you use Red Rubber Grease (RRG).

you must remove the oxidisation in the seal recesses before fitting new seals.

no amount of spraying brake cleaner or other cleaners will remove the oxidisation. the calliper pistons MUST be removed and the recesses cleaned of oxidation. then and only then can you fit new seals using RRG rubbed into the seals. RRG acts as a barrier against moisture/water ingress while also keeping the rubber pliable. RRG was invented for the very purpose with use on brake seals. RRG can also be used on the sliding pins as its very high melting point.

do not ever use copper grease anywhere on brakes, this is why there are anti squeal shims on the back of pads.