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Disc brake BCD?

#1 2018-06-30 7:37am

AlurencatBMX
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Disc brake BCD?

Hey guys. I bought a fixie and well, it's no longer a fixie. However, what I wanted to know is the BCD of a disc brake and how many bolts it has. It *looks* very similar to where my fixed gear was but I'd like to be sure before I risk it.

https://s3.amazonaws.com/uploads.bmxmuseum.com/user-images/41840/img_20180630_1534125b37959639.jpg


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#2 2018-06-30 12:00pm

Minx20
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Re: Disc brake BCD?

Are you wanting to put a disc rotor on and a disc caliper adapter?

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#3 2018-06-30 12:49pm

Otto_Maddox
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Re: Disc brake BCD?

It's likely the same six bolt pattern for a disc, but intended for a fixed cog. The frame does not look like it has the clearance for a disc, even a small 140mm rotor.

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#4 2018-06-30 1:44pm

Crashman
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Re: Disc brake BCD?

Otto_Maddox wrote:

It's likely the same six bolt pattern for a disc, but intended for a fixed cog. The frame does not look like it has the clearance for a disc, even a small 140mm rotor.

Nah nah nah, that's a disc mount. There are at least two bolt patterns and one is Chinese. Measure center-to-center across the entire thing and get the BCD, then check eBay.


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#5 2018-07-01 1:50am

AlurencatBMX
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Re: Disc brake BCD?

Minx20 wrote:

Are you wanting to put a disc rotor on and a disc caliper adapter?

The thought has entered my head yeah. Whether I will or not? dunno tbh. I'd like to stop the surface of the rim being killed by brakes if that was possible.

Otto - I think it's OK. but could easily cut some cardboard discs and see if they fit in there.

Crashman wrote:

Otto_Maddox wrote:

It's likely the same six bolt pattern for a disc, but intended for a fixed cog. The frame does not look like it has the clearance for a disc, even a small 140mm rotor.

Nah nah nah, that's a disc mount. There are at least two bolt patterns and one is Chinese. Measure center-to-center across the entire thing and get the BCD, then check eBay.

Yeah when I looked at it before I took the fixed off it looked more like they had made the fixed to go there instead of it being a proper fixed set up (like my SE wheels has). That looks like this.

https://s3.amazonaws.com/uploads.bmxmuseum.com/user-images/41840/fixed-gear-hub-1369840234-05b3896e447.jpg

I just found this pic though, this looks a lot more like what I got on the mags.

https://s3.amazonaws.com/uploads.bmxmuseum.com/user-images/41840/fixed-disk-word-hub_25b3896f74e.png

Last edited by AlurencatBMX (2018-07-01 1:55am)


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#6 2018-07-01 2:08am

AlurencatBMX
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Re: Disc brake BCD?

OK so I've sorted the mount.

https://s3.amazonaws.com/uploads.bmxmuseum.com/user-images/41840/a2z-retrofit-med5b3899eb7c.jpg

Which in my case will be fitted like so.

https://s3.amazonaws.com/uploads.bmxmuseum.com/user-images/41840/handsome_dog_frame_24_04_2011_61_1155b3899fb7d.jpg


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#7 2018-07-01 6:01am

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Re: Disc brake BCD?

Hahah! I wonder what the chain tensioner is for, since braking force would appear to push the axle toward the rear of the slot?


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#8 2018-07-01 7:37am

Otto_Maddox
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Re: Disc brake BCD?

Crashman wrote:

Otto_Maddox wrote:

It's likely the same six bolt pattern for a disc, but intended for a fixed cog. The frame does not look like it has the clearance for a disc, even a small 140mm rotor.

Nah nah nah, that's a disc mount. There are at least two bolt patterns and one is Chinese. Measure center-to-center across the entire thing and get the BCD, then check eBay.

You're mistaken. It's a modern flip-flop wheel intended to be used with a six bolt cog.

https://s3.amazonaws.com/uploads.bmxmuseum.com/user-images/245546/sixboltfixedcog5b38e671ee.jpg

Last edited by Otto_Maddox (2018-07-01 7:38am)

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#9 2018-07-01 8:03am

blue78
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Re: Disc brake BCD?

AlurencatBMX wrote:

what I wanted to know is the BCD of a disc brake and how many bolts it has

There are 2 common ones, 44mm and 48mm; 6 bolt.

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#10 2018-07-01 8:06am

blue78
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Re: Disc brake BCD?

And I'm going off of memory here:  the area where the disc mounts should be 15mm from the locknut.  Or in other words, with the wheel mounted on the bike, there should be 15mm between the inside face of the dropout and the face of the disc mount on the hub.
Somebody correct me if my memory is wrong...

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#11 2018-07-01 8:16am

troynlori
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Re: Disc brake BCD?

Measure center to center from two adjacent holes.  Everything else is defined by geometry.  Besides, with a decent caliper you can straddle the middle and just measure the BCD.   So measure adjacent holes only if you only have a ruler....


Hey!

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#12 2018-07-01 10:24am

AlurencatBMX
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Re: Disc brake BCD?

blue78 wrote:

And I'm going off of memory here:  the area where the disc mounts should be 15mm from the locknut.  Or in other words, with the wheel mounted on the bike, there should be 15mm between the inside face of the dropout and the face of the disc mount on the hub.
Somebody correct me if my memory is wrong...

OK well I have 18ishmm. Are you sure it's 15 without the disc on? I assume the disc is around 3mm thick?

https://www.amazon.co.uk/Hope-Bolt-Hub- … oding=UTF8

You can get all sorts of spacers tbh.

blue78 wrote:

AlurencatBMX wrote:

what I wanted to know is the BCD of a disc brake and how many bolts it has

There are 2 common ones, 44mm and 48mm; 6 bolt.

Right just measured it, it's 44mm. Are they M4? I had to wreck the bolts to get them off as they were some sort of torx fitting and my allen keys were slipping. I ended up cracking them loose, then removing with clamp on grips so they went in the trash (the bolts).


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#13 2018-07-01 10:46am

AlurencatBMX
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Re: Disc brake BCD?

Crashman wrote:

Hahah! I wonder what the chain tensioner is for, since braking force would appear to push the axle toward the rear of the slot?

I would imagine those are just part of that guy's frame. It was just a random pic I grabbed from Google.


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#14 2018-07-01 1:56pm

Crashman
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Re: Disc brake BCD?

troynlori wrote:

Measure center to center from two adjacent holes.  Everything else is defined by geometry.  Besides, with a decent caliper you can straddle the middle and just measure the BCD.   So measure adjacent holes only if you only have a ruler....

Yep

Last edited by Crashman (2018-07-01 2:23pm)


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#15 2018-07-01 8:21pm

blue78
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Re: Disc brake BCD?

AlurencatBMX wrote:

Are they M4?

I think they are M5.

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#16 2018-07-02 12:13am

AlurencatBMX
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Re: Disc brake BCD?

Wicked cheers. Will have a dig around for some later, if none I will order some :)


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