Front brakes dragging after bleed

[Zevk]

Sounds like another flush and fill of brake fluid may be required

Try to use a mighty vac brake bleeder

If still not good, new seal of caliper may needed….?

[fireypete]

I was just thinkin'...The fluid I flushed out was 5 years old, so whilst the old fluid has gone the damage it has done sitting there has not.  I reckon I left it too long and stuffed the seals, so they wont pull the pistons back.  Ive never serviced a caliper, so i may have a crack.  At least get some seals and see if the pistons are OK

[Zevk]

I would just try carefully flushing another 1-2 bottles of new fluid thru

Have you cleaned out the master cylinder reservoir with a lint free paper towel?

Don’t pull the lever without fluid in the reservoir….if you let the reservoir get to low, you will introduce air into the system and without a mighty vac, you may regret it…. 

Same goes for replacing the seals, as the fluid will all drain out all the fluid and then need to bench prime the calliper, especially if hoses are removed…

Good luck 

[ZuluTiger]

There are two places you have to look, IMHO. The fluid reservoir is just a hopper that needs to be kept topped up to supply extra fluid to cope with pad wear. In itself, it has no effect on the rest of the system but can be the source of gunk.

The first real problem is at the calipers themselves. All it takes is a ridge of corrosion to form and they will not 'retract' and then drag. Bear in mind, the piston really only stops pushing, it never truly retracts. I don't know of any shortcut once this happens as you need to figure out what is doing it and it is likely to be muck or corrosion, if not an actual seal. Stripping and cleaning is not as bad a job as it seems but does take time.

The second problem is if the master cylinder has muck in the return gallery. This causes the effect that the fluid is unable to return to the reservoir with the lever relaxed. It has the effect of the brake being gently applied. If both front discs are dragging, this is likely the culprit. With a little creative 'spacering' to mimic a brake pad and disc, it's possible to figure out which caliper is dragging, if you get my drift. Master cylinder cleaning is much more involved as it requires stripping out the plunger and multiple seals. Bleeding the entire system after this is also a tiresome job but provides peace of mind in the long run.   

[Paul2bikes]

Over fill the ressie & the fluid has nowhere to go when it heats up but to push pistons out, resulting in warped discs.

The caliper pistons do retract, this can be seen once serviced, they are designed to do so. I ensure this is happening before re-fitting. The pistons should move freely eg push one in by hand & others will slide out.

In 27 years & 170k miles of Hinckley Trumpies with Nissin calipers, I have never had any issues with master cylinders, I may have been lucky there. Problems are usually just dirty pistons. Calipers need cleaning regularly. When neglected they end up with (as I've said before) corrosion in the dust seal groove forcing the seal tight onto the piston causing resistance.

Our TS front calipers are not usually a problem if serviced at regular intervals, it's the back caliper position that causes problems.

[Rhead]

yup. the seals are made to stretch a bit and pull the cups back. On my 02 sprint, the cups were not slippery enough and would pull back too much causing excessive lever travel. The opposite of your issue. I spray my calipers with brake cleaner every couple of months and have never had to touch them.    https://www.freeasestudyguides.com/brake-piston-seal.html

[ZuluTiger]

The point I was making is that it's a miniscule retraction designed only to avoid rubbing. Sometimes it's impossible to even see. As Rhead says, too much of this would result in a mushy lever and too much travel. The biggest internal contributor to both master and slave maloperation is corrosion due to the hygroscopic nature of brake fluid. Since the ingress is usually at the reservoir, the master is often damaged internally, first. I still think I'd check the outer edges of the slaves for corrosion and crud first, based on their torrid work environment.

It'll be good to hear what the final outcome reveals.

[Paul2bikes]

I hope this explains it easier, the next one will be in braille. 

[ZuluTiger]

Paul, watching this video, I can see why you came up with the Braille comment .....  Pretty good all round!

[leew]

Has the 2013 got abs? You may need to bleed the abs pump(you can do it with Tigertool & a suitable eobd reader, look up user:tiger800xc, he wrote it, it's free & brilliant!). But you may also be right with sticky calipers