Has anyone swapped BB on a BMC Roadmachine?

Discuss light weight issues concerning road bikes & parts.
gurk700
Posts: 302
Joined: Fri Jan 20, 2017 7:40 pm

by gurk700

EDIT / UPDATE: I just received my Wheels Manufacturing BB that is made of aluminum. Solved the issue. Aluminum pieces are way more rigid than the plastic duraace cups so the brake cable doesn't push them out of the way. Bike is finally fully built.

I've swapped many BB's on many bikes and I'm a little puzzled here. For the roadmachine there really seems to be only one path for the rear brake hose. Once you route it through that path, the brake cable blocks where the spindle is supposed to go through.
I can kind of force the brake cable and bend it out of way but with a DuraAce BB, it just doesn't work. The cable pops the middle section of the BB out. Only other solution I can think of is to buy a one piece metal BB so there's no interference.

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Last edited by gurk700 on Sat Feb 16, 2019 4:58 am, edited 1 time in total.

by Weenie


AlgaeHater
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Joined: Sun Jan 27, 2019 2:53 am

by AlgaeHater

When I swapped out the drivetrain on my RM 02, I encountered the same problem. I installed a threaded BB from Wheels Mfg:

https://www.competitivecyclist.com/whee ... ExOmJiODY=

Very happy with this BB. Solid construction that's unlikely to creak. I installed the same BB on my Timemachine Road as well.
2019 Bianchi Oltre XR4 eTap
2019 BMC Timemachine Road 01 Di2
2018 BMC Roadmachine 02 Di2

TiCass
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by TiCass

Maybe your cable is a bit too long? I believe it should go over the axle spindle.

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TonyM
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by TonyM

TiCass wrote:
Tue Jan 29, 2019 5:24 pm
Maybe your cable is a bit too long? I believe it should go over the axle spindle.
That's also what I was thinking...I can't remember having the brake cable going under the BB on my RoadMachine02.
Last edited by TonyM on Tue Jan 29, 2019 6:29 pm, edited 1 time in total.

AlgaeHater
Posts: 67
Joined: Sun Jan 27, 2019 2:53 am

by AlgaeHater

According to the BMC assembly manual, the rear brake line goes under the BB:

https://www.bmc-switzerland.com/fileadm ... ual_EN.pdf

This is how it's setup from the factory for all RMs.
2019 Bianchi Oltre XR4 eTap
2019 BMC Timemachine Road 01 Di2
2018 BMC Roadmachine 02 Di2

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TonyM
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by TonyM

AlgaeHater wrote:
Tue Jan 29, 2019 6:39 pm
According to the BMC assembly manual, the rear brake line goes under the BB:

https://www.bmc-switzerland.com/fileadm ... ual_EN.pdf

This is how it's setup from the factory for all RMs.

Thanks for the info and the link! :thumbup:

TiCass
Posts: 226
Joined: Thu Aug 04, 2016 1:13 pm

by TiCass

AlgaeHater wrote:
Tue Jan 29, 2019 6:39 pm
According to the BMC assembly manual, the rear brake line goes under the BB:

https://www.bmc-switzerland.com/fileadm ... ual_EN.pdf

This is how it's setup from the factory for all RMs.
Thx for the link!
Well, that might means the cable is a bit too short. The opening should be unobstructed.
Last edited by TiCass on Wed Jan 30, 2019 12:32 pm, edited 1 time in total.

AlgaeHater
Posts: 67
Joined: Sun Jan 27, 2019 2:53 am

by AlgaeHater

I don't think it's an issue of the brake hose being too short. When I was building my RM 02 Di2, I found that the stiff brake hose wouldn't follow the contour of the BB housing. It would push up against the plastic sleeve of the Shimano PF86 making re-assembly difficult without damaging the sleeve. In contrast, installing the threaded BB was a snap.
2019 Bianchi Oltre XR4 eTap
2019 BMC Timemachine Road 01 Di2
2018 BMC Roadmachine 02 Di2

gurk700
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Joined: Fri Jan 20, 2017 7:40 pm

by gurk700

Hey guys! I honestly don't think it's a brake hose length issue. I have a lot of slack and tried it every way. The channels for the hose are at the bottom of the BB. The cable has maybe an inch and a half where it's not in a channel. So to bend it any other way is quite impossible.

My theory is that I need a BB with metal tube instead of plastic DuraAce. That way the super stiff cable doesn't push the plastic out of way or damage it. So pretty much what AlgaeHater said.

I'm gonna look into that WM one thank you for posting that!
Last edited by gurk700 on Wed Jan 30, 2019 7:06 am, edited 1 time in total.

Mr.Gib
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by Mr.Gib

Just take a moment to contemplate incredible stupidity of this design. Even the most flexible cable would still interfer with the crank axel. If left long enought, at some point the axel would wear through the hose. I love Switzerland. On my visits there I have never encountered any person or thing that would lead me to believe that this was possible. Shame.
wheelsONfire wrote: When we ride disc brakes the whole deal of braking is just like a leaving a fart. It happens and then it's over. Nothing planned and nothing to get nervous for.

gurk700
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by gurk700

Mr.Gib wrote:
Wed Jan 30, 2019 7:06 am
Just take a moment to contemplate incredible stupidity of this design. Even the most flexible cable would still interfer with the crank axel. If left long enought, at some point the axel would wear through the hose. I love Switzerland. On my visits there I have never encountered any person or thing that would lead me to believe that this was possible. Shame.
100% agree. Cervelo, Sworks, Felt and multiple models of these brands. Never had this issue.

Axle wouldn't eat through the hose as the spindle is completely contained in the BB shell that doesn't spin, but doesn't change the fact that it's bad design. I know the photo makes you think the BB is already installed and you still can see the cable. But I haven't installed the BB seeing how it's gonna be blocked by the cable. The one time I attempted I couldn't cause the cable pushed the plastic BB off axle.

Anyway... Just gonna order an all metal BB.

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TonyM
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by TonyM

My RoadMachine02 did not have this problem.

The cable is too short IMHO.

iamraymond
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Joined: Wed Jun 28, 2017 8:59 am

by iamraymond

My SLR01 has a similiar BB design and did not have this problem. I agree with TonyM that the hose is too short.

Was this a frameset build or a standard BMC build where you are changing the BB? If the bike is still disassembled and you haven't yet fixed the hoses to the frame, then I'd try giving the rear brake hose a bit of extra slack from the front.

ibloch
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Joined: Sun Jan 13, 2019 12:21 pm

by ibloch

I have the same problem and it is not a problem of hose length. It's just that the rather stiff hydraulic hose does not follow the bend so well as it should.

Or there is a trick, which I haven't found out about yet....

Here is the photo of how this looks on my new Roadmachine 01 2019 frameset.
IMG_0057.jpg
Haven't gotten to pressing the BB yet, but was wondering about the same point.

Mr.Gib
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Location: eh?

by Mr.Gib

gurk700 wrote:
Wed Jan 30, 2019 7:08 am
Mr.Gib wrote:
Wed Jan 30, 2019 7:06 am
Just take a moment to contemplate incredible stupidity of this design. Even the most flexible cable would still interfer with the crank axel. If left long enought, at some point the axel would wear through the hose. I love Switzerland. On my visits there I have never encountered any person or thing that would lead me to believe that this was possible. Shame.
100% agree. Cervelo, Sworks, Felt and multiple models of these brands. Never had this issue.

Axle wouldn't eat through the hose as the spindle is completely contained in the BB shell that doesn't spin, but doesn't change the fact that it's bad design. I know the photo makes you think the BB is already installed and you still can see the cable. But I haven't installed the BB seeing how it's gonna be blocked by the cable. The one time I attempted I couldn't cause the cable pushed the plastic BB off axle.

Anyway... Just gonna order an all metal BB.
Yes, this is true, but I never use the plastic sleeves. My BB's always seem to spin better without them - even with careful and correct install. :noidea: And how would one even make sure a sleeve is sitting correctly with a tough hose pushing against it. The sleeve would end up jammed against the crank axle. In that situation it is theoretically possible for the crank axle to wear through the sleeve and then the hose.

I will continue to argue that all we are getting screwed from a maintenance perspective when it comes to everything internal and integrated. Nothing but headaches that keep bikes in the shop instead of on the road. This industry has a long way to go to get to solutions that represent real gains for the consumer.
wheelsONfire wrote: When we ride disc brakes the whole deal of braking is just like a leaving a fart. It happens and then it's over. Nothing planned and nothing to get nervous for.

by Weenie


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