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I have just retired my Tektro brakes (13 years of service) and replaced with a pair of cheap Shimano MT200.

I have a problem with extremely narrow gap between the disk and pads. The gap is so narrow that it makes it near impossible to adjust brakes for no rubbing. Also any amount of dirt that gets on the disk during winter ride is guaranteed to cause a lot of noise.

Brakes don't appear to be overbled. Pistons can be pushed all the way back into the caliper when pads are removed. Also lever freestroke distance appears to be usual. For contrast I compare this to another bike that has SRAM brakes on it. Lever travel is about the same but SRAM brakes have about 3x times as much of a gap between pads. It appears that for the same amount of lever travel SRAM calipers advance/retract 3x distance of Shimanos... This cannot be right.

It is difficult to take a picture of but here is a sketch:

enter image description here

What I have tried and checked so far:

Wheel off + pads off + push the pistons all the way back.

Makes no difference. Calipers can be pushed all the way in without a proble, Leveler bottoms out. After doing this, the bite point is lost and it takes a few pumps of the lever to let the calipers adjust and "find their place". After calipers are in place, the problem is back - gap is too narrow.

Re-bleed

I am no stranger to bleeding brakes. Done everything by the books. But for this particular subject it is important that I bled the brakes with pistons fully pushed back and largest bleed block (that fits) in place. This should make sure that the system is not overbled... I obviously don't pressurise the system. No improvement

Rotor thickness

My rotors are original from Tektro and I thought that maybe rotor thickness is different between Tektro and Shimano, but it does not appear so. Rotors measure 1.8 mm with a digital caliper...

Caliper tilt (pad not parallel to disc that makes visual gap smaller)

Nothing to say here, calipers are mounted straight. I readjusted them a few times.

Running out of ideas here. Any advice appreciated.

UPDATE 2021-05-10

About 2000 km later I can confirm that the correct answer was "just ride it". The problem was there for a while but eventually went away (around 1000km mark.

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  • Do you have access to calipers? Could be the rotors are thicker than Shimano calipers expect - I don't rememebr the numbers but 2.0mm to 1.6mm for tektro and shimano wanted rotors of 1.8mm max thickness. Comment because this is not my area and I'm going off memory. – Criggie Feb 1 at 21:36
  • That gap is normally sized for Shimano. The SRAM brakes I’ve dealt with have a similar gap. Magura are even tighter, so don’t worry. – MaplePanda Feb 2 at 3:33
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    @Criggie, rotor measures 1.8 mm with digital caliper. Sounds about right to me. – Art Gertner Feb 2 at 9:53
  • @MaplePanda, I can't measure the gap (would need some filler gauge for it) but it looks about at 1/8th of a mm (with rotor in of course). My SRAM brakes have about 1mm on either side of the rotor. – Art Gertner Feb 2 at 9:54
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    Unless your disks wobble as in out of true, and the rotors touch the pads, this is fine. – Carel Feb 2 at 18:41
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The gap depicted for your Shimano brakes appears to be of similar dimension to a couple Shimano systems I run. The spacing is very close and I'm often truing the rotors to ride rub free. Shimano hydraulic brakes are self-adjusting in relation of the pad to the rotor, so that when the pad wears, the spacing stays the same. Bed your new brakes in properly and be alert for rubs that might require truing of the rotor or recentering the caliper.

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Its unclear to me what the actual problem is, apart from your feeling the pads are too close.

If they are not pulling back far enough and rubbing the disc all the time, it could be stiffness just from being new and unused. Install them and ride...

You could try to lube the piston and seals (remove pads, squeeze out pistons and drip oil on them then work them in and out a few times a few times. Personally I would not bother unless I had a few miles on them and still had problems.

The issue of winter grime between the disc and pads will not go away or get better with a bigger gap.

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  • You should probably clarify that by dripping oil on the pistons you mean mineral oil which is used as brake fluid in Shimano brakes – Andy P Feb 2 at 8:39
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    Thanks for the advice to lube the pistons. These are brand new brakes just out of the box. And I actually did put a drop of mineral oil on them before installing. – Art Gertner Feb 2 at 9:56

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