Brake calliper under BB good or bad?

roubaixtom

Hi,

Looking at getting Rose Xeon CGF-2000 however the brake calliper is mounted under the BB. From a practical point of view it will probably get dirty under the BB. However Rose state that it is 10-15% more efficient under the BB and also makes the bike more comfortable due to the absence of the brake bridge on the seat stays.

Rear brake under BB, pain in the a*** that should put me off that particular bike, nothing to worry about or a benefit?





Cheers

dj58

That looks like the direct mount version BR-6810-R Ultegra rear caliper. That is not a new idea and the performance of the brake should not be affected, however It will get dirtier and may required more cleaning/maintenance in view of the fact the reverse side of the brake is in the firing line from all the detritus coming off the tyre.

If you want to familiarise yourself with it go to http://si.shimano.com/#seriesList/38 under the heading BR-6810, download the pdf files EV-BR-6810-R-3601.pdf and DM-BR0003-06-ENG.pdf, refer to p15 on.

Remains to be seen whether the idea will catch on or die a death as with chain stay mounted brakes on some late 80's MTB's.

Wheelspinner

Scenario 1: You are a highly-paid professional bike racer, with a personal mechanic, soigneur, nutritionist, psychologist and a marketing agent, plus your own website.com. In this case, brakes under the BB are fabulous daaaahling, save you milliseconds in drag efficiency, and they are 0.032467% more comfortable after the seventh day in a row of more than 200km riding through the Alps.

Scenario 2: You are an amateur, mainly weekend rider, possibly a MAMIL, with limited time and fettling skills. In this case, brakes under the BB shell are about as dumb an idea as you can possibly have. Avoid if you can.

alihisgreat

Wheelspinner wrote:

Scenario 1: You are a highly-paid professional bike racer, with a personal mechanic, soigneur, nutritionist, psychologist and a marketing agent, plus your own website.com. In this case, brakes under the BB are fabulous daaaahling, save you milliseconds in drag efficiency, and they are 0.032467% more comfortable after the seventh day in a row of more than 200km riding through the Alps.

Scenario 2: You are an amateur, mainly weekend rider, possibly a MAMIL, with limited time and fettling skills. In this case, brakes under the BB shell are about as dumb an idea as you can possibly have. Avoid if you can.

Scenario 1 (pt2): Your brake is rubbing and can't be adjusted from the team car... or at least you can't pretend your brake is being adjusted to get a tow.


and regarding the original question I think if you ride in the wet/winter a lot its probably not a great idea... but for a best bike/race bike I don't see why not.

roubaixtom

Yes it will be my best nike, have a winter bike + cross bike to use in bad weather. To be honest the more I look at the bike more I like the clean lines putting the caliper under the bb allows.

frisbee

I had a mountain bike with a rear brake under the chain stays, never had any problems with it.

The bike is still kicking around and the brake still works.

brettjmcc

I have a TRP mounted under my BB on my Quintana Roo. Adjusting brakes is a PITA. I basically comes down to having to take the cranks out to do it properly, I can't access the brake blocks. This may be different on a normal bike, as I have an aero chainring

iron-clover

I personally would avoid brakes under the BB, as I spend enough time as it is adjusting my brake calipers (they are only Tiagra though tbf) as it is, and having one under the BB would make the job a lot more difficult.

I would ignore the supposed benefits, as they will almost certainly be negligible- probably more psychological than anything, and only buy if you really like the look of the bike and don't mind potentially spending much more time on maintenance. You'd probably have to clean it thoroughly after most rides too to prevent grit from getting in between the caliper arms and seizing them up.
But if you don't mind doing that in order to own that particular bike, then why not?

How Far is too Far

On a best bike that is used mainly in the dry I can see no reason why not. If it was on a winter bike I think it would become a pain.

roubaixtom

Very true, I clean my bike after most rides. Most of this summer the bike will be ridden abroad so it shouldn't be too much of a problem. How are they adjusted?

Also, surly they don't get that dirty compared to normal calipers as the rear caliper gets all the spray from the rear wheel.
Cheers

alihisgreat

Roubaixtom wrote:

Very true, I clean my bike after most rides. Most of this summer the bike will be ridden abroad so it shouldn't be too much of a problem. How are they adjusted?

Also, surly they don't get that dirty compared to normal calipers as the rear caliper gets all the spray from the rear wheel.
Cheers

Under the BB it gets spray off the front wheel.

roubaixtom

true, any worse than rear wheel though?

Bar Shaker

If it had a small removable shroud, it would be protected form the crud thrown up by the front wheel and would be more aero* with a lowering of the bike's CoG.

That would tick my boxes.


* the normal place for a rear calliper is after the air has been disrupted by your kegs, the seat tube and the seat stays. What is exposed gets hit by very dirty air that may well be moving forward at close to bike speed. The gains would be very small.

MountainMonster

Get a bike with disc brakes! It is amazing compared to standard rim brakes.

dj58

Roubaixtom wrote:

How are they adjusted?

Tom, if you read the pdf files I referred to earlier, it shows how to set up and adjust the brake. Adjustment for pad wear is made by the SM-CB90 in-line adjuster/quick release mechanism that is in the second photo.

janesy

I have a Trek 5.9. same brake.

Works perfectly, never goes off center - its direct mount so impossible.
It gets the same crud as if it would on the stays. not a problem.

Only issue is replacing the pads as chainset is in the way.

rolf_f

janesy wrote:

It gets the same crud as if it would on the stays. not a problem.

Well, no it doesn't. It is getting additionally all the crud thrown off the front wheel. Enough to wreck the wheel bearings on a cheap wheelset I once had so certainly enough to do nasty things to a BB mounted brake. Of course, if it is a sunny day bike this doesn't matter.

simon_masterson

It's been done on time trial frames for years. Dangerfield, Cammish et al used to have a bridge regardless; I can believe that leaving the bridge off makes a very small difference to frame response.

I can't see it being worth bothering with on a regular road bike though, unless it's a marginal-gains-tastic machine with no paint.

roubaixtom

I just like the rose and am planning to buy it. But because it stands out from most due to the caliper being under the bb I was just cautious.

janesy

Rolf F wrote:

janesy wrote:

It gets the same crud as if it would on the stays. not a problem.

Well, no it doesn't. It is getting additionally all the crud thrown off the front wheel. Enough to wreck the wheel bearings on a cheap wheelset I once had so certainly enough to do nasty things to a BB mounted brake. Of course, if it is a sunny day bike this doesn't matter.

I was just saying that I have not has a problem. Yes its on my nice bike but have ridden it through most of this winter inc Rapha500.

Anyway its never bothered me. Rolf F, do you have this brake?

John.T

I have had my 2007 Madone frame changed to a 2014 version under warranty. Now running a Bonty direct mount brake under the BB. If anything it stays cleaner than the seat stay mounted one on the old frame. Works just as well.

redvee

13Bikes from Halfords have them fitted at the BB and I can see plenty of problems given the target market, even though I look after my bike I would steer well clear.

rolf_f

janesy wrote:

Rolf F wrote:

janesy wrote:

It gets the same crud as if it would on the stays. not a problem.

Well, no it doesn't. It is getting additionally all the crud thrown off the front wheel. Enough to wreck the wheel bearings on a cheap wheelset I once had so certainly enough to do nasty things to a BB mounted brake. Of course, if it is a sunny day bike this doesn't matter.

I was just saying that I have not has a problem. Yes its on my nice bike but have ridden it through most of this winter inc Rapha500.

Anyway its never bothered me. Rolf F, do you have this brake?

No, I haven't. And, to be honest, for a best bike it wouldn't put me off. But for something that has to put up with what my Ribble Gran Fondo does, it would (5 days a week in all weathers plus winter weekend riding - currently on 25000 miles). As it is, the caliper bushings on that aren't as slick as they once were. The wheel bearings I ruined were on a tourer that I removed the mudguards from for a while - the rear bearing started giving trouble not too long after. I had to strip it and regrease it after each wet ride.

I find that although I'm pretty good at keeping my bike clean, the BB area still tends to get neglected the most (and cause most problems with poor shifting due to crap build up in the cable guides). I'd have thought that any maintenance, adjustment and cleaning on a BB mounted caliper would require the bike to be upside down - maybe not such a big issue but given that the only practical benefit of having the caliper in that position is to be able to tell people that that is where your caliper is, it perhaps isn't worth it!

DKay

janesy wrote:

Only issue is replacing the pads as chainset is in the way.

If you own a mixture of carbon and alloy rims, I can see that becoming a collosal PITA.

rolf_f

DKay wrote:

janesy wrote:

Only issue is replacing the pads as chainset is in the way.

If you own a mixture of carbon and alloy rims, I can see that becoming a collosal PITA.

TBH, can't see it as much of a problem myself. Invert bike, unbolt old cartridge, slip Tacx brake block tuner over rim. Loosely fit new cartridges. Spin wheel so the Tacx thing pushes the pads into position. Tighten up. Remove tuner, put bike back on wheels.

Certainly quicker than swapping pads in conventionally positioned calipers without the Tacx thingy. More likely to get oily digits from the drive side but nothing life threatening.

seast91

I have the Rose Xeon CGF-3100 Di2.

Servicing these brakes is a simple job, just turn the bike upside down or invest in a bike work stand.

Centering is great as it is done with an allen bolt that adjusts the position and the brakes are fixed to teh frame so don't move in use.

Dirt in the caliper is also not an issue. The caliper gets no more dirty than a traditional caliper, to clean them properly you need to remove the rear wheel but I remove my wheels to clean the frame properly anyway.

There is one problem however and advice would be appreciated as I aren't sure if this is the caliper or just the brake blocks. After about 20 miles in bad weather the gaps in the brake blocks fill with grit/grime and braking becomes a noisy affair, not to mention the obvious wear on the rims. I can't see that this is due to the positioning of the caliper as much as it would be the shape of the block...does anyone experience this with Shimano blocks/recommend an alternative?

holiver

Direct mount brakes under the BB would be good for a summer bike I reckon. I would rate accessibility for any other type of bike more important though, as the brake is sure to get more road muck on it from the front wheel spray. Lots of cleaning required!

arthur_scrimshaw

Roubaixtom wrote:

true, any worse than rear wheel though?

Yes, most of the heavy duty muck on a back wheel is thrown off by the time it gets to the (conventionally mounted) rear brake. The chainstay mounted rear brake gets all the muck thrown off front wheel which is why so much gunk accumulates around the BB cable guides. Of course if you've got longboard mudguards with a flap you're quids in.