Front brake lever excess travel on occasions.

[Stevex]

LM2 with de-linked brakes.
Front brake MC PS15 feeding 2 braided hoses to original calipers.
Stainless steel discs with sintered pads.
I've noticed that on occasions the lever pull comes back further than 'normal' to operate these brakes.
The brakes always work, it's just that sometimes the pull required is more than normal and when I release the pull and re pull, the travel is normal again.
The system is well bled, there's no pulsing to indicate warped discs, in fact discs and pads are nearly new.
The lever is solid when the pads bite, and braking is very good.
I've got into the habit of gently pulling the lever every now and again to check the lever travel and can't put the excess travel down to any particular instance during the ride other than maybe riding on less than smooth roads.
I've recently replaced the caliper seals and the pistons are aluminium.
I don't have a fork brace fitted.
Front wheel bearings are new.
Is it possible the fork bodys are slightly twisting on bumpy roads and pushing the pistons in?

[rodekyll]

I'll go with warped/bent disks even though you say it's not.  2nd choice is wheel bearings.

[oldbike54]

 Something is knocking the pads back , and it doesn't take much . Or , there is a bit of air somewhere .

  Dusty

[Triple Jim]

Agreed.  Pulsing shows up from rotor thickness variation much quicker than from warped rotors, but warped rotors can cause your symptom.

[Vasco DG]

Another possibility is a damaged seal in the master cylinder or a small score in the bore.

Pete

[Groover]

Watching because I may have this same issue. It's happened only once so far on my front. Went back to normal now.

[Triple Jim]

I can imagine it happening one time only, if you somehow bumped the caliper while moving the bike around the garage, for example.  It could cause a piston to retract, requiring a squeeze or two to get back to normal.

[oldbike54]

 Oh , Mr X , doubt if it is being caused by fork twisting , as the calipers and rotors follow the forks .

  Dusty

[Groover]

I can imagine it happening one time only, if you somehow bumped the caliper while moving the bike around the garage, for example.  It could cause a piston to retract, requiring a squeeze or two to get back to normal.

Ok, thanks! That makes sense. I like the cheap fixed that cost $0.00  I'll keep an eye on it. About ~100 miles since it happened in my case, and that's in town with a lot of braking going on.

[Triple Jim]

That's one advantage of "linked" brakes:  If either brake system fails, you still have a front brake.

[JoeW]

Agreed.  Pulsing shows up from rotor thickness variation much quicker than from warped rotors, but warped rotors can cause your symptom.

If the rotors are bad enough to cause this, it would happen more often and the brakes would pulse on application. I'm with Pete on this, it's the master cylinder.

[mtiberio]

Rebuild the m/c

[rodekyll]

I have excessive travel on one front m/c.  It's consistently down every morning.  I burp the bleeder and it always has some tiny bubbles.  I interpret that to be a bad m/c piston seal.  But it's consistent -- every morning.  (yes, I have parts in shipment to fix it).

[Stevex]

Many thanks for all your inputs.
Although the MC was 'new' when I fitted it about a year ago, I don't know how long it sat on the shelf.
As the only part of the system I've not touched, I'll re seal it this winter and give the bore a good inspection.