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AlurencatBMX · 2018-06-30 7:37am

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.

Minx20 · 2018-06-30 12:00pm

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

Otto_Maddox · 2018-06-30 12:49pm

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.

Crashman · 2018-06-30 1:44pm

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.

AlurencatBMX · 2018-07-01 1:50am

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.

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

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

AlurencatBMX · 2018-07-01 2:08am

OK so I've sorted the mount.

Which in my case will be fitted like so.

Crashman · 2018-07-01 6:01am

AlurencatBMX wrote:
OK so I've sorted the mount.
https://s3.amazonaws.com/uploads.bmxmuseum.com/user-image … 99eb7c.jpg
Which in my case will be fitted like so.
https://s3.amazonaws.com/uploads.bmxmuseum.com/user-image … 99fb7d.jpg

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

Otto_Maddox · 2018-07-01 7:37am

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.

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

blue78 · 2018-07-01 8:03am

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.

blue78 · 2018-07-01 8:06am

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...

troynlori · 2018-07-01 8:16am

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....

AlurencatBMX · 2018-07-01 10:24am

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).

AlurencatBMX · 2018-07-01 10:46am

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.

Crashman · 2018-07-01 1:56pm

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)

blue78 · 2018-07-01 8:21pm

AlurencatBMX wrote:
Are they M4?

I think they are M5.

AlurencatBMX · 2018-07-02 12:13am

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

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Disc brake BCD?

#1 2018-06-30 7:37am

Disc brake BCD?

#2 2018-06-30 12:00pm

Re: Disc brake BCD?

#3 2018-06-30 12:49pm

Re: Disc brake BCD?

#4 2018-06-30 1:44pm

Re: Disc brake BCD?

Otto_Maddox wrote:

#5 2018-07-01 1:50am

Re: Disc brake BCD?

Minx20 wrote:

Crashman wrote:

Otto_Maddox wrote:

#6 2018-07-01 2:08am

Re: Disc brake BCD?

#7 2018-07-01 6:01am

Re: Disc brake BCD?

AlurencatBMX wrote:

#8 2018-07-01 7:37am

Re: Disc brake BCD?

Crashman wrote:

Otto_Maddox wrote:

#9 2018-07-01 8:03am

Re: Disc brake BCD?

AlurencatBMX wrote:

#10 2018-07-01 8:06am

Re: Disc brake BCD?

#11 2018-07-01 8:16am

Re: Disc brake BCD?

#12 2018-07-01 10:24am

Re: Disc brake BCD?

blue78 wrote:

blue78 wrote:

AlurencatBMX wrote:

#13 2018-07-01 10:46am

Re: Disc brake BCD?

Crashman wrote:

#14 2018-07-01 1:56pm

Re: Disc brake BCD?

troynlori wrote:

#15 2018-07-01 8:21pm

Re: Disc brake BCD?

AlurencatBMX wrote:

#16 2018-07-02 12:13am

Re: Disc brake BCD?

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