Rotors for 2-piston Shimano BR-MT410 extremely limited?

[stompandgo]

This is not my area of expertise, so I'll fall back on diagnostic principle. What was the last thing that you changed? When did the problem appear? If the brakes were the last, are the rotors true, and is there no contact between the rotor and the pads when spinning the wheel on the stand? If it was the fork, can you put it back to the original settings?

 

[Chazmo]

Is the fork compressing to a different level now with you on it, Ringo, than before you serviced it? If so, the extension of the stanchions may have changed (probably more extended now??) while you’re riding, and maybe oscillations are occurring that weren’t possible before.

In any case, my bet is not on the fork. I think stompandgo’s advice is right on. My bet is that the rotor is slightly warped and/or the pads are making oscillating contact. Like stomp said, can you spin the wheel on the stand (or off the ground) and watch the brake contact?

 

[Gionnirocket]

Is the wheel mount a through bolt or drop out?
If the latter, make sure it's fully seated.
Sometimes it's hard to do in a stand. When back on the floor, loosen the release, wiggle the wheel and tighten the lever. Then double check your pad/rotor clearance.

 

[Ringo9]

This is not my area of expertise, so I'll fall back on diagnostic principle. What was the last thing that you changed? When did the problem appear? If the brakes were the last, are the rotors true, and is there no contact between the rotor and the pads when spinning the wheel on the stand? If it was the fork, can you put it back to the original settings?

Rotor was indeed the last thing changed, together with the post mount adapter to push the caliper further out where it needs to be for a 203mm rotor (previously mounted directly on the fork with 160mm rotor).

Few days before that I played around a bit with fork settings and pressure to bring the behaviour more to my like as I'm new to this and didn't have a baseline to judge whether the existing setup was good or bad.

Thing is, I can't be sure I went "hands off" before changing the rotors and after playing with the fork so I can't be sure it was indeed the rotor or the fork.

Now, fork settings and pressure I can more or less revert to where they used to be, I think I can recall those values.
Rotor seems to be true. There was some touching of the pads at first but I fine tuned the position of the caliper and the wheel now spins freely when in the air.

If the fork just so happened to break/need a service right after those events it would be quite a coincidence but as I said the bike just clocked 1000km so for a cheap fork it may not be that unusual.

Last thing I can always do is put back the stock rotor (and remove the post mount caliper adapter) so I can eliminate new rotor being the cause, I just didn't want to jump straight to it.

@Chazmo That could be because of the extra air pressure I added recently, going from 90psi to 130psi. But I'll revert that and check.

@Gionnirocket the wheel mount is a through axle bolt.

 

[Gionnirocket]

Rotor was indeed the last thing changed, together with the post mount adapter to push the caliper further out where it needs to be for a 203mm rotor (previously mounted directly on the fork with 160mm rotor).

Few days before that I played around a bit with fork settings and pressure to bring the behaviour more to my like as I'm new to this and didn't have a baseline to judge whether the existing setup was good or bad.

Thing is, I can't be sure I went "hands off" before changing the rotors and after playing with the fork so I can't be sure it was indeed the rotor or the fork.

Now, fork settings and pressure I can more or less revert to where they used to be, I think I can recall those values.
Rotor seems to be true. There was some touching of the pads at first but I fine tuned the position of the caliper and the wheel now spins freely when in the air.

If the fork just so happened to break/need a service right after those events it would be quite a coincidence but as I said the bike just clocked 1000km so for a cheap fork it may not be that unusual.

Last thing I can always do is put back the stock rotor (and remove the post mount caliper adapter) so I can eliminate new rotor being the cause, I just didn't want to jump straight to it.

@Chazmo That could be because of the extra air pressure I added recently, going from 90psi to 130psi. But I'll revert that and check.

@Gionnirocket the wheel mount is a through axle bolt.

The other common causes of wobble are loose, worn headset bearings and spoke tension so you can check these...
Sometimes coincidence can be a some_ma_na_bitch
But I agree... Go over what was recently touched.

 

[Shifty Shane]

Thanks @Shifty Shane, @Base and everyone else ( I'm bad at multi-quoting from several pages ) So...

Reading an earlier post saying most aftermarkets rotors in a shop measured around 17mm contact patch I went ahead with the MDR-C Maguras and... as I was afraid, their contact patch at the lowest point measures at most 12.5mm... That leaves a good 3.5mm of the B05S pads sticking out as they measure ~15,5mm high (vertically). However as you can see from the pictures this "contact gap" varies from 3.5mm down to 0 (full pad cover) as the pockets on the Maguras are a varying size shape. I wonder whether this constantly varying contact area during braking (as the wheel turns) will a) be felt / heard b) reduce the expected stopping performance or c) won't make any difference apart from looking not sized correctly to the trained eye...

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PS. Thinking about possible performance impact: Magura actually sells pads that match these exact rotors. Those pads are made also for 2-piston calipers (but from Magura) so it's just 1x left and 1x right, and are shorter in height than the B05S. That means the contact area is not larger than the one I am getting now with Shimano pads and they are supposed to work fine. That must mean that the only possible side effect is either noise or a varying wear on the pads? but with the wheel turning it shouldn't be the case? I wonder if anyone has tried this combo before. I really want to keep them and try them but that will void any return...

I wonder if the compatible Magura pads are any wider to compensate for the reduced height.
When I got my 203mm Centerline rotors and noticed the shorter outer pad contact surface, I was concerned that the inner portion of the pads would wear differently than the rest of the pads, because they weren't in contact with the rotor for the full revolution.
I also thought the pads eventually wearing down the thickness of the rotor spokes/arms wouldn't be good either.
Once I looked into the compatibility further, everything I read suggested the rotors with the narrow outer contact area were meant to be paired with 4 piston calipers that had narrow but wider pads, or 4 pads per caliper.
My goal was to affordably improve the front braking force to be similar to the rear 180mm rotors with equal application. I plan to eventually upgrade to 4 piston calipers when I start riding off-road downhill trails, so I'll save the narrow 203mm rotors for the 4 piston calipers. The Tektro calipers and pads I recently received have a better contact patch after 20 min break-in.

 

[Ringo9]

I wonder if the compatible Magura pads are any wider to compensate for the reduced height.
When I got my 203mm Centerline rotors and noticed the shorter outer pad contact surface, I was concerned that the inner portion of the pads would wear differently than the rest of the pads, because they weren't in contact with the rotor for the full revolution.
I also thought the pads eventually wearing down the thickness of the rotor spokes/arms wouldn't be good either.
Once I looked into the compatibility further, everything I read suggested the rotors with the narrow outer contact area were meant to be paired with 4 piston calipers that had narrow but wider pads, or 4 pads per caliper.
My goal was to affordably improve the front braking force to be similar to the rear 180mm rotors with equal application. I plan to eventually upgrade to 4 piston calipers when I start riding off-road downhill trails, so I'll save the narrow 203mm rotors for the 4 piston calipers. The Tektro calipers and pads I recently received have a better contact patch after 20 min break-in.

I thought of trying the Magura pads as well, they even sell the pads & rotor as a bundle, but I wasn't sure how compatible they would be with my calipers so I decided to test it.

As an update, I put back the original rotor and removed the caliper adapter but the wobble is still there although the severeness seems to vary depending on the terrain. Played around with fork's settings and it's still there.
Btw, I only realized how poor the 160mm rotor was in terms of stopping when I put it back, wow

So since that didn't solve it I switched back to the 203mm setup, wobble is the same as with the 160mm so I'm guessing maybe the fork is on its way out? It's not a real issue as I don't do high speeds with my hands off, just annoying to know. Maybe in spring time I might consider upgrading to a better fork.

 

[stompandgo]

I would rebuild the fork first before any further brake changes.