Shimano B01S pads

[djrowell]

Can anyone help with this question?
My bike is fitted with Shimano BR-M447 disc brakes. I have recently had to change the brake pads, which are Shimano BS01 resin pads.
The replacement pads come with two split pins. One is 2.7mm diameter, the other 3.2mm diameter. The correct one for my brake type according to Shimano is 2.7mm. However, the two pins are unmarked and try as I might, I have found it impossible to tell which is which. Both are a loose fit in the brake housing.
My question is: does it really matter which one I use? If it does, why do Shimano not mark them?

[Brucey]

one pin is nearly 20% fatter than the other and (usually) a bit shorter



the 3.2mm dia pin (Y-8C5 05000) is used in various brakes including

- Shimano Deore BR-M525-M
- Shimano Deore BR-M525
- Shimano BR-M495
- Shimano BR-M475-M
- Shimano BR-M475
- Shimano BR-M465
- Shimano BR-M416-A
- Shimano BR-M416
- Shimano BR-M415
- Shimano BR-M375
- Shimano Tourney TX BR-TX805
- Shimano Nexave BR-C501

In some cases (eg BR-M495) it can be fitted as a substitute for a threaded pin ('pad axle') with an M4 thread in the LHS of the caliper.

The 2.7mm dia pin (Y-8DB 06000) is used on brakes including

- Shimano BR-M666
- Shimano XTR BR-M9020
- Shimano XTR BR-M9000
- Shimano XTR BR-M987
- Shimano XTR BR-M985
- Shimano Saint BR-M820
- Shimano Deore XT BR-M8000
- Shimano Deore XT BR-M785
- Shimano SLX BR-M7000
- Shimano SLX BR-M675
- Shimano ZEE BR-M640
- Shimano Deore BR-M615
- Shimano Deore BR-M596
- Shimano Alivio BR-M4050
- Shimano Acera BR-M3050
- Shimano BR-M447
- Shimano BR-M395
- Shimano BR-M355
- Shimano Alfine BR-S700
- Shimano Cyclocross BR-CX77
- Shimano Cyclocross BR-CX75
- Shimano BR-RS785
- Shimano BR-R785
- Shimano BR-R517
- Shimano BR-R515
- Shimano BR-R317
- Shimano BR-R315

I suspect that the pin length is sometimes important. I also note that the head shape on the 3.2mm dia pin is different from that on the 2.7mm dia pin; this may be significant in those cases it is used to replace a threaded 'pad axle', i.e. it may not pull through as far, or risk damage to the screw threads in the caliper body. In some cases either pin may be acceptable.

cheers

[djrowell]

Thanks Brucey, I hadn't twigged the difference in length or the slightly different shape to the head. It does beg the question of why Shimano don't make them obviously different so that there is no argument. If I could find somewhere on their website to register a complaint, I would.

[Brucey]

I suspect that you might get into a pickle with some mechanical calipers if the longer pin is used; the end of the pin might stick out unless both sides are folded back. But in general split pins are incredibly reliable in bicycle brakes; you are far more likely to have a problem with some other part of the brake! By comparison car brakes often use 4mm or 3/16" dia split pins for pad retention; by those standards the ones on bicycle brakes seem somewhat over-engineered!

Also note that dealing with shimano disc brakes is a bit 'Alice'; you are soon down a rabbit hole wondering what exactly is going on; I don't believe for one moment that it was necessary to have quite as many models as they have made; after all most of them have the same mountings, the same piston sizes, and even use the same pads. They also go wrong for the same reasons, which is something they didn't bother changing....

cheers