Issues with disc brake adapter upside down
 

I recently installed post mount TRP Spyres on an IS mount using IS to PM adapter on 160mm rotors (SM-MA-R160P/S).

When the adapter was mounted with arrow up, the pads only contacted half the rotor.
When the adapter is mounted upside down, then the pads contact the full rotor, I can see the top of the rotor level with the top of the pads and the barrel adjuster is pointed up at the cable run at a good angle.

It is the same situation for front and rear.

Is this normal or expected? Have I the wrong adaptors? I can’t seem to see a safety issue with this.

Thoughts?

https://cimg3.ibsrv.net/gimg/bikefor...a66541363.jpeg
https://cimg4.ibsrv.net/gimg/bikefor...6d1f64fa3.jpeg
https://cimg5.ibsrv.net/gimg/bikefor...7b712f929.jpeg

If you click on "Mount style" on this page, you'll see that SMMAR160P/S is a rear mount. Front mounts have F in them.
https://bike.shimano.com/en-EU/produ...MAF180PP2.html

Does it fit correctly now?

Yes?

Run it.

...I miss you.

Both adapters are that number and both front and rear needed to be mounted upside down. The front adapter arrow points down, obviously, and the rear arrow points toward the BB.

It’s just that when a part has an orientation arrow and, for it to work, requires to be opposite that orientation just gives me pause.

When reversed, yes.

We DID have a good thing going, but you lost my trust when you cheated on me.

then run it... that part doesn't care which way it's mounted.

It pretty clearly is not the front brake part, or the arrow would point correctly and wouldn't be labeled R for rear.

But if it works, that's fine too.

...trust is such an ephemeral concept. I thought we were bigger than that.

Agreed. Both adapters have the same number ergo the orientation arrow, on the rear, should point up.

BUT she’s a-workin anyway.

Thank you for your help.

Stop using big words, you know I don’t like big words.

...maybe the intention was to make certain you install them with the bicycle inverted in a stand ? Did you try it that way ?

That's brilliant! Ok, I'll remove the adapters, put the bike in the stand, inverted, then reinstall! You sir, clearly, are not paid enough.

.
...we'll always have Paris. :)

You’re just responding to get the last word, ain’t ya?

How does the pad placement look on the other side of the caliper?

Front and rear IS adapters for the same size rotors are different sizes because front IS mounts are set at 160mm and rear IS mounts are set at 140mm.

Comparing a flipped 160mm rear adapter to a 160mm front adapter, I'd be surprised if the pads were contacting the rotor properly.


https://cimg3.ibsrv.net/gimg/bikefor...6162da76d7.png

Well, at the risk of sounding impertinent (that is not my intent), if the pad, as shown in the photo I provided, is contacting the rotor properly, then wouldn't the OTHER pad be the same? Yes, both pads appear to contact the rotor properly - the top of the rotor, as shown in the photo, is level with the top of the pad. If I mount the adaptor the correct way, with the arrow pointing up on both front and rear, the pads only hit about half the rotor.

This (and as well as other things in my life) is why I am confused and though t to ask you fine folk for your opinion.

I'm asking if the pads on the other side of the caliper are also contacting the rotor properly

One side might look fine, the other side might not.


https://cimg2.ibsrv.net/gimg/bikefor...18cf6496ba.png

Yes, both pads look ok, they are not rotate as shown in your diagram.

What's in that image mightn't look as extreme in real life it.

So when you look in where the green arrow is pointing, there's no part of the pad overhang of the rotor?

https://cimg3.ibsrv.net/gimg/bikefor...299572d6e3.png

The bottom of your flipped rear adapter is similar position to a front 160mm adapter, the top of your setup is completely different, there must be some of the pads overhanging the rotor.


https://cimg7.ibsrv.net/gimg/bikefor...688c31228d.png

I've stared down inside the caliper until I near gone blind, both pads are level with the top of the rotor. It is difficult to get a photo, but if you look at the bottom of the pads in the photo you reposted, you can see the bottom of those pads are level, since the pads are the same size, then the top of the pads are level with the top of the rotor, and I can confirm this by sighting inside the caliper and I see the pads are level with the top of the rotor.

Best I can do for a photo of the front caliper and pads.


https://cimg3.ibsrv.net/gimg/bikefor...61bcf3a0f.jpeg

The inner edge of the rotor isn't a good way to check for alignment.

Shimano makes two types of rotors (narrow and wide) and two types of pads (narrow and wide), they don't recommend using wide type pads on narrow 2 piece rotors, the pads used in the Spyre/Spyke brakes are exactly the same as Shimano wide type pads, the rotor you're using looks to be a Shimano narrow 2 piece like the RT76 / RT81 / RT86 / RT-EM800.

I've seen a few photos of wide pad use on narrow rotors, the pads were overhanging the inner edge of the rotor and wearing on the arms of the rotor.

What you can see from the outside looking in, mightn't show the full story, after a bit of use I'd remove the pads from the caliper to see if there's any unusual wear on them.

https://cimg5.ibsrv.net/gimg/bikefor...ccbab329f7.png


https://cimg6.ibsrv.net/gimg/bikefor...bb1ff3132e.png

It wasn't cheating, you know that, cheating implies you didn't encourage him. You practically pushed him out.