Pad/ rotor contact area

D

deafwish

Likes Bikes
Hey all,

I have concerns that my Shimano M445 front pads on my 2011 Giant Reign 2 are only in contact with 2/3 of the rotor face.
I had realised that my front Shimano brake bracket (mounts the caliper to the fork) has an "up" arrow that faced down to the ground, so I have swapped that around.
The pad still only seems to cover 2/3 of the rotor though!?
Has the bike shop possibly installed the wrong bracket?

Some pictures:





 
rone

rone

Eats Squid
Unbolt the caliper and remove those Avid adjusters. Some muppet has got their brands confused. Shimano face up directly to the mount without those silver spacers. Would probably point this out to the shop involved as it's a bit of a gumby mistake, with potentially serious consequences.

Edit - see photo below. Bigger rotor, but the caliper is mounted directly against the adapter.
 

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D

deafwish

Likes Bikes
Bang on - problem resolved!
Thanks for the advice, Rone.
One of the bolts has a slight bend in it. Is this an elliptical design for adjustment or is it just bent & in need of replacement?!
Will bring it up with the bike shop!:eek:
 
harmonix1234

harmonix1234

Eats Squid
deafwish said:
Bang on - problem resolved!
Thanks for the advice, Rone.
One of the bolts has a slight bend in it. Is this an elliptical design for adjustment or is it just bent & in need of replacement?!
Will bring it up with the bike shop!:eek:
Click to expand...
It shouldn't have a bend in it.
If it does, it is probably due to the bolt being extended futher than it was intended to be whilst the spacers were in.

I could be wrong though. But I have never seen a bent bolt 'on purpose'.
 
Yakuza Michael

Yakuza Michael

Likes Bikes
Some of the new Shimano brakes are coming with the conical spacers, they are for use under the head of the bolt to allow some tolerance in the post mount system. In your case, as stated above, they were just put in the wrong spot.
 
D

deafwish

Likes Bikes
^^^ Put in the wrong spot or mistakenly put there - period?!
Sorry to sound stupid - but should they be there or not?:confused:
 
rone

rone

Eats Squid
Not. Only Avid use those spacers. Pretty sloppy work by the shop IMO. The bolt shouldn't be bent either.

Yakuza Michael said:
Some of the new Shimano brakes are coming with the conical spacers, they are for use under the head of the bolt to allow some tolerance in the post mount system. In your case, as stated above, they were just put in the wrong spot.
Click to expand...
Which Shimano brakes would they be?
 
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floody

floody

Wheel size expert
The logic behind the conical spacers eludes me - if the other side of the mounting tab is directly in contact with the bolt head the spacers won't allow for any adjustability, they are redundant and might as well be solid.

Yakuza Michael post some model numbers, photos or other evidence about these shimano brakes with avid style mounts. Again, one set of conical washers is pointless, the caliper will locate to the the flat surface of either the bolt head (as pictured) or the adaptor (if the spacers are under the bolt). Makes no more sense than using a full halflink chain for chainstay length issues.
 
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harmonix1234

harmonix1234

Eats Squid
Also, you may want to get some new pads.
It probably dosn't matter too much, but if they are worn down a lot in the middle there will be a hard edged ridge at the top of the brake pad where it has not been worn down.

When you put your brakes on, this small unused bit will be the part that contacts the rotor and you may not have much stopping power until it wears down.

Probably not much of a prob if it's only a few rides old though.
 
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T-Rex

T-Rex

Template denier
If you are going back to the shop, ask them (nicely) to supply you with a new set of pads at no charge. At the end of the day their fairly ordinary workmanship will have resulted in your pads wearing unevenly, as others have stated.

Under the circumstances, I'd say that's the least they can do for you.
 
rone

rone

Eats Squid
I'll admit I havent seen that before, but as Floody said, it serves no purpose having the adjustment spacers on one side only.

Still set up differently to yours, though.
 
Dales Cannon

Dales Cannon

lightbrain about 4pm
Staff member
The only time a spacer or washer is needed in between the caliper and the mount is if the rotor contacts the caliper body. This will NOT happen with Shimano calipers and Shimano rotors. I have Hope rotors which are a couple of mm bigger in diameter than the equivalent Shimano rotors so I fitted a flat stainless washer between the caliper and mount. Just enough to clear the caliper. Throw the spacers away you do NOT need them. If the pads have a ridge on the outside you can wear them down by rubbing on concrete or as has been suggested ask the bike shop for new pads. While you are at it get a new caliper bolt to replace the bent one. A bent bolt will prematurely wear the tapped thread in the mount so it is a bad thing.

The Shimano washers are between the bolt head and the caliper and do not affect the geometry or fit up of the caliper and mount, they are simply to get the best possible contact area between the bolt and caliper. Forget about it these aren't necessary either unless something is wonky.
 
E

ex729

Cannon Fodder
Hi :)

I think that this spacer is for aligning bolt head to caliper body, because pm tabs on fork have slightly different angle than brake adapter. If you don't use this washers, or place it in wrong spot you can bend the bolt (or maybe even stressed threads in fork tab).
You can see this situation here (from mtbr thread):

Yakuza Michael said:
Some of the new Shimano brakes are coming with the conical spacers, they are for use under the head of the bolt to allow some tolerance in the post mount system. In your case, as stated above, they were just put in the wrong spot.
Click to expand...
Shimano use this washers in new style 180mm brake adapter:
http://techdocs.shimano.com/media/t...01/SI-8170A-001-ENG_v1_m56577569830667774.PDF
where you use only 2 bolts. This adapter use 4 bolts. Look at bolt angles:


Cheers,
Luke

Sorry for my english :)
 
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rone

rone

Eats Squid
All well and good, but look at the unswept area on the first pic. Similar to the OP's don't you think?
 
E

ex729

Cannon Fodder
rone said:
All well and good, but look at the unswept area on the first pic. Similar to the OP's don't you think?
Click to expand...
Yes, because this is wrong setup (washers are between adapter and caliper).

This is correct setup (washers under the head of the bolt):
 
T-Rex

T-Rex

Template denier
ex729 said:
Hi :)

I think that this spacer is for aligning bolt head to caliper body, because pm tabs on fork have slightly different angle than brake adapter. If you don't use this washers, or place it in wrong spot you can bend the bolt (or maybe even stressed threads in fork tab).
You can see this situation here (from mtbr thread):
View attachment 192683

Shimano use this washers in new style 180mm brake adapter:
http://techdocs.shimano.com/media/t...01/SI-8170A-001-ENG_v1_m56577569830667774.PDF
where you use only 2 bolts. This adapter use 4 bolts. Look at bolt angles:


Cheers,
Luke

Sorry for my english :)
Click to expand...
Looking at the top picture here, you can clearly see that the top bolt is bent, caused by the top of the adaptor being thicker than the bottom, and both being through bolted. This could have been corrected by having less washer thickness on the top than the bottom. I'll bet it was the OP's top bolt that was bent, although it's not as clear in his pic, the setup is the same as shown in ex729's pic. Bending a high tensile bolt like this is dodgy, it could fail any time. Get the shop to give you a new one of them too.

EDIT: This really is very poor workmanship by the mechanic.
 
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