Kinetics Brompton Rohloff kit?

[Pale Rider]

The older model had raised embossed, rubber, unpainted numbers (which wear off).The newer shifter has indented, painted numbers (which still wear off). I just got accustomed to 'clunky' and don't think about it anymore. Probably easy for me as I drive an older Land Rover Defender! Now that is clunky...

Yes, my numbers wore off quite quickly.

I've put a couple of blobs of paint on the shifter.

The little blob is low gear and the big blob is about in the middle.

I used to glance at the numbers, although it's fair to say you couldn't if riding in the dark.

A few reports of the shifter failing.

It probably is the weakest link of a Rohloff installation.

 

[u_i]

Yes, my numbers wore off quite quickly.

I've put a couple of blobs of paint on the shifter.

The little blob is low gear and the big blob is about in the middle.

I used to glance at the numbers, although it's fair to say you couldn't if riding in the dark.

I glue neoprene pieces on twist shifters, both the moving and fixed parts, that I can feel with fingers in the dark.

 

[Schwinnsta]

The reason for less speed on smaller wheels is that they are more jarring and ride harsher due to their smaller attack angle. These jolts are absorbed by the rider. The rider becomes the shock absorber with jarring energy dissipated in friction within the body.

 

[berlinonaut]

I'm thinking about the gearing for the Brompton conversion. The first thing I had to do was learn how to do the calculation! My Thorn Rohloff-equipped MTB has a 44T chainring and 13T sprocket. It's a 26" wheel. This gives about 71 gear inches. The gearing is just right for my normal daily rides. A standard 50T chainring on a Brompton with a 13T sprocket gives 61 gear inches. If I specified a 54T chainring that would still give only 66 gear inches. To achieve similar gearing to the Thorn I would need a 58T chainring on the Brompton. My question is this: between two very dissimilar bikes such as these will 71 gear inches feel the same on each or are there other forces in play?

My thoughts go as follows:
- you are set on the wheel size
- you are basically set on the 13t sprocket (to achieve a usable development with 349 size wheels)
- so your only variable is the size of the chainring.

The Rohloff's direct gear is the 11th, though there's no real relevant difference in drag between the gears. Still it seems a good idea trying to have the 11th (or close to it) as the standard gear for your typical riding in the flat (als you then have enough room to go higher with three more gears and massive to go lower when it get's hilly). The lower end is not really a problem with the Rohloff on a Brompton - it will basically always be short enough in real life. I'd try to avoid the 7th for typical riding as it is the noisiest gear.
So, depending from your typical speed and your typical favorite cadence you can find the appropriate size of the chainwheel. I use ritzelrechner for that where you have a lot of vaiables, a good visiualization and you can compare two different setups, too: https://ritzelrechner.de/?GR=RLSH&K...DV=gearInches&GR2=RLSH&KB2=54&RZ2=13&UF2=1330

Here I set the cadence to 75rpm (which is about my personal standard, your's may be different) and as I rather use meters of development than gear inches I created two screenshots:

Here we go with meters of development and km/h for the same setup:

Following the 11th gear rule I'd have to go to something like a 60t chainring to align my typical speed and cadence for the Brommi (in the sense to have my favorite meters of development in 11th). In reality I am running the 50t quite happily at the moment but consider to go a little higher (but not as high as 60t, maybe 54) longterm. Just that it would be a bigger operation as I currently run the old bottom bracket along with the old fixed chainwheel on that bike and a change is not urgent, so I avoid all that hassle for the time being. With 60t my highest gear would be ridiculously high as well - I'd never use it. To have some reserve for a real steep ascent seems more reasonabe to me.

 

[rafiki]

What a great resource, thank you for that. For the new conversion my hunch is to go for 54/13 and then play it by ear from there.

I haven't asked Kinetics yet but a new Rohloff hub is supplied with a default 16T sprocket. I preume they order their stock with the 13T option.

BTW my Thorn MTB setup is 44/16 not 44/13 as I originally posted. I have corrected the typo.

 

[rafiki]

Well the Rohloff kit arrived with some delays but that was to be expected. I had a little trouble removing one of the rear triangle hinge bolts but with Kinetics advice and a mini butane torch it came away cleanly. Refitting the rear carrier to the new triangle needed a bit of fiddling but it went on fine eventually. No problems with the Rohloff shifter and cabling. Even that dreaded ex box pulley wound on and inserted with only a few swear words. We are in a severe lockdown in Spain so I can't take it out to test it properly yet which is very frustrating but it looks good. Running it up on the stand it seems to work fine but we'll see when we are released.

I haven't decided what to do about the grips. The brake lever has a large protrusion for mounting the useless bell and prevents further movement to the left and the Rohloff shifter takes up so much space there is only 60 mm left for the grip which isn't enough. I'm looking at three options to make more space. I could grind off the bell support bulge thus clearing the way but that could be messy/unsightly or I could purchase a pair of replacement levers without any hindering protrusions or, perhaps, purchase a third party H bar with a greater width although I'd have to watch the fold.

 

[berlinonaut]

watch the fold.

Not particularily useful for your problem, but this could be a great marketing claim for Brompton

 

[rafiki]

Not particularily useful for your problem, but this could be a great marketing claim for Brompton

It's a 'flight check' I guess every Brompton owner gets imprinted on their subconscious after doing a mod or two then going back to the drawing board! Fitting the Quad Lock to the bar to hold my phone/GPS took some trial and error.

 

[rafiki]

I've worked out a couple of ideas for the grips/Rohloff shifter with the help of the guys at SJS Cycles. The first and easier is to buy a SRAM 'shorty' grip for the right hand bar and a matching 110 mm grip for the left. The shorty is 60 mm which is the exact length I have to fill so it remains to be seen if that short length works well with the shifter. The grips are cheap so worth a try. If that doesn't feel right I shall get a Joseph Kuosac mid-riser bar and replace the original. I'll lose about 20 mm height but I don't think that will be a problem. The JK is 600 mm wide giving me an extra 40 mm space on each side.
It may need trimming a bit if the fold catches the floor but I have a rack and Eazy wheels which they think gives enough room.

 

[12boy]

That bike is way too pristine.​

 

[rafiki]

For the moment it is. We are in total lockdown here in Spain until at least the end of this month and probably mid-May. We have already been confined for a month! Nothing would give me greater pleasure than to dirty it up! I still have bookings to ride it on the Camino de Santiago - Camino Frances in northern Spain at the end of May. 350 km over 6 days from León to Santiago de Compostela but as the weeks pass with this damned virus it looks less and less likely to happen. I envy those who are allowed out each day to exercise but not us I'm afraid.

 

[12boy]

I feel bad for mentioning it. As soon as I do something to my bike I've gotta try it out.

 

[rafiki]

Oh, please don't feel bad, what we are going through is very necessary and beginning to show results. The infection and death rates are on an encouraging downward trend in Spain. I have to be careful because, at 75 years of age, I am well into the high risk population. I am more fortunate than most as limited dog walking is permitted so I can walk my three pooches three times a day but only close to the house. I hope at the end of the month some of the restrictions will be lifted so that I can at least cycle out into the countryside and take the dogs into the forest but we shall see.

 

[Gunk]

I've worked out a couple of ideas for the grips/Rohloff shifter with the help of the guys at SJS Cycles. The first and easier is to buy a SRAM 'shorty' grip for the right hand bar and a matching 110 mm grip for the left. The shorty is 60 mm which is the exact length I have to fill so it remains to be seen if that short length works well with the shifter. The grips are cheap so worth a try. If that doesn't feel right I shall get a Joseph Kuosac mid-riser bar and replace the original. I'll lose about 20 mm height but I don't think that will be a problem. The JK is 600 mm wide giving me an extra 40 mm space on each side.
It may need trimming a bit if the fold catches the floor but I have a rack and Eazy wheels which they think gives enough room.

View attachment 514061

That is beautifully engineered bit of kit (but it should be for the price 😮) It is however a lot of an additional weight, Is the trade off worth it?

 

[rafiki]

800 grammes allegedly. I have had a Rohloff hub on my Thorn Sterling MTB for 10 years and I love it. Having ridden the Brompton from new on tarmac and gravel in standard 6 speed format I really didn't like the gear system and decided quite quickly I wanted a Rohloff on that too.