Answered Brakes question can anyone help

[Kernow]

Ok my daughter now has 2 vitus escarps the older one has Xt brakes on 180 disc front , the new one has sram brakes with 200mm rotors .
She also has a second set of wheels which she wants to fur both bikes . So I figured the best way is convert the old bike to a 200mm front disc .
So I bought a couple of 200 mm scram discs and a post mount that Iam told allows the Xt caliper fit 200 mm discs . Which it does seem to perfectly
The old shimano post mount uses bolts right through into the fork with cup washers on but those cup washers are only on the outside so pointless .
My uncertainty is the new post mount , it bolts to the fork with 2 bolts provided , no problem , but I now obviously need bolts for the caliper and the shimano bolts are way too long ,
In the picture I’ve just bolted the caliper onto the new sram mount using bolts with flat washers which seems to work fine but there isn’t any cup washers used , and I can’t see the need for them , so why do shimano use them on the outside only ?
Perhaps they just help stop the caliper moving sideways as it’s tightened ?
Sram mount the calipers with cup washers both sides as in the second pic
I Just want to know if I’ve got the correct mount , or is it done another way for 200 mm discs with shimano calipers
If I had another bike here with 200 , or 203mm shimano I could probably answer this easily , but as it’s brakes and my daughter using them , I want to be certain .

 

[Kadale]

I’m not certain this is the answer however from a car - Motorsport background I can tell you it’s best to have some “float” on the Caliper to allow it to centre in the disc when applied as it will grab the disc evenly.
As long as the pands are making contact on the disc correctly I would work with either cup washer of the softer mounts

Ride it yourself and if it brakes smoothly you will be fine.

Don’t forget to lock tight the threads on the bolts

 

[Gary]

so why do shimano use them on the outside only ?

Sounds like whoever fitted the caliper had bolts that were too long and used the conical washers (being thicker) to take up some thread so as not to ruin the delicate threads in the fork.
I have a few shimano brakes and none ever came supplied with conical washers.

 

[Gary]

Ps. do you have GOLD shoes?

#PimpAF

 

[mark.ai]

I got a Shimano post mount adapter recently and it came with those cup washers and instructions to fit them on the outside of the mount like you describe your old one - no idea why though! But like you say they are needed for the length of the screw otherwise it's too long.

I think if the screw is too long then any washers on the outside would work, cup or flat ...

I've also looked at Guide RE brake mount instructions recently and they are setup just like your first picture with the cup washers on both the outside and inside, which does allow for rotation of the caliper. Presumably the Guide RE caliper is also designed to account for that extra offset further out.

 

[Re-Cycle]

You do need those conical washers on the outside of the Shimano adapter. If you don't use them the force on the bolts will not be straight (don't know how to describe this better, English isn't my native language ).

Sram uses these conical washers on both sides so the caliper can not only be centered above the disc but also tilted to correct minor imperfections of the disc tabs not being straight.

Shimano has two different (PM) adapters for 203mm discs. One with two bolts through the caliper straigth into the fork, that's the one you use the conical washers with.
And another one with two bolts to mount the adapter to the fork, and two other bolts to mount the caliper to the adapter. No need for conical washers there, because the adapter has been faced in the correct angle.

This is the best one imo, because you don't need to loosen the bolts in the fork (magnesium, not a really hard metal) everytime you need to center the caliper.

 

[Kernow]

You do need those conical washers on the outside of the Shimano adapter. If you don't use them the force on the bolts will not be straight (don't know how to describe this better, English isn't my native language ).

Sram uses these conical washers on both sides so the caliper can not only be centered above the disc but also tilted to correct minor imperfections of the disc tabs not being straight.

Shimano has two different (PM) adapters for 203mm discs. One with two bolts through the caliper straigth into the fork, that's the one you use the conical washers with.
And another one with two bolts to mount the adapter to the fork, and two other bolts to mount the caliper to the adapter. No need for conical washers there, because the adapter has been faced in the correct angle.

This is the best one imo, because you don't need to loosen the bolts in the fork (magnesium, not a really hard metal) everytime you need to center the caliper.

Thanks you’ve answered it here , and what ineffectively I have is the second type of adapter , and you have confirmed it doesn’t has cup washers .
Actually looking at my last picture above “I leaned over and took in the dark “ which is my giant hardtail there are no cup washers used there .

Thanks for all the answers , it wasn’t an easy question to compose or understand I think .

 

[Kernow]

Ps. do you have GOLD shoes?

#PimpAF

I don’t , but you’ve confused me again by asking , which isn’t difficult .
Ps I did paint my boots silver while painting the workshop roof ?

 

[Gary]

I don’t , but you’ve confused me again by asking , which isn’t difficult .
Ps I did paint my boots silver while painting the workshop roof ?

in the first pic. the shoe looks gold. on my screen

or are they black n blue stripes like that dress from Facebook?

 

[Re-Cycle]

On this pic you can see that the caliper has an angle compared to the disc mounts on the fork. So if you don't use the conical washers the bolts will take a "bending" force when you tighten them.
View attachment 9912

 

[Kernow]

in the first pic. the shoe looks gold. on my screen

or are they black n blue stripes like that dress from Facebook?

Ahh that’s the workboots I referred to that I managed to paint silver doing the roof , I had no idea they were in the picture ?

 

[Lad]

The fancy washers are called CPS/Tri Align washers.

Shimano use the between the caliper and the bolt head with the 180 or 203mm adapters
The adapter doesn't keep the caliper at 90 degrees to the bolts. If the bolts aren't at 90 degrees to the caliper they won't be able to tighten the caliper bolts down straight.

I think SRAM also use additional CPS/Tri Align washers between post and adapter for even more accurate caliper alignment.