DH and I have been riding the Bromptons for a couple of months now and we are very happy. He takes his on the bus every day, so I really scored! I'm happy that it is making his commute so much easier.

I have a 3-speed Raleigh Sports that we both love. My two other bikes are an 8-speed Retrovelo Paula, heavy but geared low enough to get up really long hills and a Nuvinci-hub Raleigh SuperCourse, which is overkill for my riding.

I decided to go with 3-speed Bromptons because 95% of our riding is multi-modal, picnics, and shopping. I planned to consider a retrofit to a BWR hub+derailleur or a Schlumpf Mountain Drive.

Some of the very steep hills are defeating me, and it's time to try to add some granny gears. The gearing is already -18% (44x14) on our bikes. We don't need anything higher. We do need lower.

I spoke to David at Electric & Folding Bikes Northwest yesterday and he told me that Schlumpf no longer manufactures the Brompton specific MD, but no big deal because they can be installed on Bromptons.

Using a calculator that I found at http://xldev.co.uk/bgc.html, I came up with the following:



I think the SMD is the best choice for me. I get a wider range than a BWR+derailleur, and more importantly, it is all LOWER gears.

With a 50 I get:



Any opinions?