Rear disc brake conversion?

[Ubert767]

Can anyone advise on the conversion from worn CSS rim  "V" brakes to a rear disc brake on a Rohloff hubbed Mk1 Raven Nomad, please?
Rob

[PH]

I'm not sure what bike you have?  To convert to a disc brake the frame needs to have that fitting and the Raven didn't.

[Ubert767]

Hello PH,
As far as I'm aware my bike frame does have the necessary rear  braze-ons to accommodate a disk caliper, it's a 2007 MK1 Rohloff equipped Nomad.
Rob

[PH]

In that case - first see if the hub is disc ready or the rim brake version, some people chose to have that hub even with rim brakes to future proof it.  If not it needs the shell cap replacing which is a workshop job.  Then if it's an internal shift mech it needs converting to external (Can't fit a disc with an internal), you can do that yourself with the parts, but if you're sending it off for the cap you may as well have that done in the workshop. Cost of those two items was around £350 seven years ago, don't know what the current price would be.  Then of course you have the cost of the rotor and brake, plus the frame may need facing. Then it's just the wheelbuild. 
I went through it when I put the hub that originally came on my Raven, into a Mercury frame, SJS did the work.  If I had my time again I think I'd have sold the hub and bought a disc version new, there wouldn't have been much difference to the cost.

[Chris667]

I know this isn't what you are asking, but I have always felt a disc brake was more useful on the front, if at all.

[PH]

I know this isn't what you are asking, but I have always felt a disc brake was more useful on the front, if at all.

From a purely braking perspective, you're probably right, my folder has a better brake on the front than the back and it stops well.  But there are other considerations, if you want a lighter more flexible fork, that's more achievable with rim brakes and importantly for a Rohloff, if you want to avoid disturbing it for wheel builds a disc brake avoids the wear.   

[martinf]

Nothing to do with braking as such, but a rear wheel disc brake (or drum, roller or coaster brake) doesn't spray muck and water from the rim and onto the chain like a rim brake can.

Not much off an issue with a Chainglider, but it has made a difference on two of my bikes. Combined with a low hanging front mudflap to reduce spray from the front wheel.

[mickeg]

My Rohloff is on a rim brake bike and I have no plans to convert it.

One reason is that some rear Rohloff hubs with disc brakes have had oil leakage onto the rotor.  I say that based only on what I have read on this and one other bike forum. 

My point is that if you make the conversion, do your best to make sure that you have very good seals on your Rohloff to avoid any oil contamination on the rotor.  My Rohloff is one that I suspect would have a lot of contamination on the  rotor.

If you convert to a different rim, do not discard the CSS rim, those rims can't be obtained any more and I am sure someone would love to have it.

[in4]

I’ve had a rear css rim for 6 years now. The braking advantage remains good and much better than a non css rim.
The thought occurred how long a css rim is likely to last and if at some point  it would be necessary to fit a rear disc brake.

[PH]

I’ve had a rear css rim for 6 years now. The braking advantage remains good and much better than a non css rim.
The thought occurred how long a css rim is likely to last and if at some point  it would be necessary to fit a rear disc brake.

I have just one left in use, a 700c front dynamo wheel, it's been on three bikes since I think 2007, conservative estimate of mileage would be 80,000, the bulk of that while it was on commuting bikes.  It's currently on the Mercury and doing no more than 3,000 miles a year and less likely to be used in poor weather. it started life as almost 2mm thick and is currently 1.3, I'd expect it to be fine to 0.8. For me, that'll be another 20 years, there's a good chance of it outlasting me, or at least my cycling days.

[il padrone]

I’ve had a rear css rim for 6 years now. The braking advantage remains good and much better than a non css rim.
The thought occurred how long a css rim is likely to last and if at some point  it would be necessary to fit a rear disc brake.

I have had the CSS rims on my Thorn Nomad for the past 13 years. The braking did get to the point, about 5-6 years ago where the carbide had worn off and the Swissstop Blue pads were working really bad in the wet. I converted to standard brake pads and that improved things a lot.

In early 2021 I converted the whole bike to hydraulic disc brakes - a new Rohloff hub-cap and the 2019 Thorn disc fork with a new SON28 disc dynohub. That was fantastic for braking but I did have two glitches:

1. In mid 2022 I found a crack in the front fork rack-mounts. cleaning off by my LBS showed it to be into the fork-blade. Thorn/SJS were very useless; when I asked for their opinion they went 'full-lawyer' and denied any liability, even trawling my FB page to claim I was running rear panniers on the front rack, a thing I have NEVER done. It became clear to me when comparing the old & new forks that the narrower rack mount with the 5mm bolts had a reduced radius of brazing to hold it against lateral stresses ( I have been running Tubus Duo racks since 2011 when I made this bike up). Eventually I just got the fork fixed by my LBS, a skilled frame builder. He removed the rack-mounts, TIG-welded a plate to strengthen the fork then TIG-welded the rack-mount onto the plate. Not pretty but it is tough.

2. Beware of braking power with the discs, especially on the front. I had one bad low-speed fall where I believe that I was relying too much on the front brake and skated the front tyre off on some loose gravel on concrete water-channel bridge. I was pretty severely injured from a 'bag-of-spuds' fall onto concrete.

However overall, disc-brakes work very well for me on tours of all types. I have had very little maintenance required, only replacing the pads once for both front and rear. Each time I was a bit foxed, thinking the brakes needed bleeding when actually a new brake pad fixed the brake issue. No new cables, no cable adjustments, just damn-fine braking. I reckon the rims, now 13 years old with no more rim wear will outlast me.

[il padrone]

One reason is that some rear Rohloff hubs with disc brakes have had oil leakage onto the rotor.  I say that based only on what I have read on this and one other bike forum. 

I have hydraulic discs fitted to my Thorn Nomad with Rohloff. No issues with disc contamination. I never refill with more than 15ml of oil. This has dramatically reduced the oil-leak issue. I do get minor seepage on the frame around the drop-outs, but this never extends to the disc rotor. A bit of dust and dirt soaks up any oil film.