Kinetics Brompton Rohloff kit?

[Pale Rider]

Yes, mine oozed a little for years. Early last year when it began to drip it was time to act, if only to stop the mess! (Not overfilled, I always put only 15ml Rohloff oil in during a change.)

Same here.

If I hammer down a gravel track, fine particles cover the hub, stuck to it by a mist of oil.

It is a beautifully engineered piece of kit.

As an example, the little filler plug has a conical taper on it to make it almost impossible to cross thread, unlike the Shimano ones which are chopped off square.

 

[rafiki]

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 16T 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?

 

[Kell]

There are other forces at play.

Shorter crankarms means that pushing bigger ratios is more difficult.

The position of your knee over the pedals will be different too.

The upright position means aero will slow you down so you might not need such high gearing.

These last two are pretty much linked.

Factory supplied Bromptons all seem to have the seat pushed as far forward on the rails as it will go.

This obviously means that you sit more upright. And it means that your knees are at least somewhere close to the optimum point of being directly above your pedal spindle when that pedal is at its foremost point. (Although I found mine were still behind by some margin.)

Pushing the seat back makes you slightly more aero, but takes your knees further away from the ideal.

Maintaining speed is harder on a Brommie too due to less momentum of smaller wheels. So you have to keep pedaling way more than you would on a road bike.

 

[rafiki]

Much food for thought there. I will have a look at both bikes as I have set them up for me and compare with the above in mind. the Thorn used to be 39/16 but I found that to be too low by about 1 Rohloff gear. Changing to 44/16 put that right. I guess there will be some trial and error with the conversion. Thanks very much for your input.

Edit: I just checked and both bikes have 170 mm cranks.

 

[Pale Rider]

The Rohloff has a famously wide range so it ought to look after you even if the front or back gearing is less than optimum.

Gearing range on small wheeled bikes does seem to be a problem.

My view is Brompton tend to sacrifice a low enough bottom gear to give a high enough top.

 

[12boy]

Kinda with Kell on this....My Brompton with 58/13 chain ring and sprocket is 71.7and my Surly Steamroller with 48/18 is 72.5. I feel overall effort is similar but the B accelerates and loses momentum more quickly and is more sensitive to uneven, broken surfaces. The Steamroller accelerates more slowly but holds speed more easily. The handling is very different as well. So, they are very similar in effort once underway but the riding experience is very different. I enjoy both equally.

 

[rafiki]

Kinda with Kell on this....My Brompton with 58/13 chain ring and sprocket is 71.7and my Surly Steamroller with 48/18 is 72.5. I feel overall effort is similar but the B accelerates and loses momentum more quickly and is more sensitive to uneven, broken surfaces. The Steamroller accelerates more slowly but holds speed more easily. The handling is very different as well. So, they are very similar in effort once underway but the riding experience is very different. I enjoy both equally.

Good to know. Thank you.

 

[rafiki]

The Rohloff has a famously wide range so it ought to look after you even if the front or back gearing is less than optimum.

Gearing range on small wheeled bikes does seem to be a problem.

My view is Brompton tend to sacrifice a low enough bottom gear to give a high enough top.

I love my Bromton bike but I find the gear changing a pain, literally. I have mild arthritis in both thumbs so I tend to plan gear changes carefully to avoid any unnecessary movements. My old 1994 Dawes Mean Street XT hybrid had lovely Shimano XT Rapidfire shifters but I changed them last year for cheap and cheerful twist shifters which made life a lot more comfortable. I am looking forward to the Rohloff shifter on the Brompton, I have no problems with it on the Thorn.

 

[Pale Rider]

What do you make of the Rohloff shifter in comparison to the Shimano?

I have both on bikes and find the Shimano a bit better.

 

[rafiki]

The newer Rohloff 'Wave' shifter is better than the old Rohloff triangular shifter I think. Both can be a bit clunky as you probably know but one gets used to that. Keeping the shifter and Ex Box well lubricated helps a lot of course. The Shimano derailleur XT Rapidfire ST-M738 3x8 shifter combo was very slick and very fast. It was very well made. I was sad when I needed to change it for twist grips.

 

[Pale Rider]

A bit clunky is how I would describe the Rohloff shifter.

Sounds like I may have an older one.

Much as I like the hub, that is one of the few minor negatives.

 

[rafiki]

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...

 

[Nibor]

@Rohloff_Brompton_Rider

 

[rafiki]

@Rohloff_Brompton_Rider

I saw his posts about his bike and have messaged him but we haven't connected yet.

 

[Nibor]

I have met him and he seemed very happy with his ( it was a while ago though)