Now that the Brompton C Line Urban has arrived, aka Mr Bumble, it’s time to start the conversion to single speed. But before we begin, I’ve decided upon a slight change to the setup described in previous bike blog posts. My initial thoughts were for a 44T/12T chainring/sprocket combination, giving me a gear ratio of 60.9″, a reasonable starting point based on experience riding Mr Orange, my 6-speed Brompton C Line Explore.
However, as I suspect this will turn out to be too high, I’ve decided to start with a different combination, retaining the 54t chainring and 16T sprocket. This gives me a slightly lower gear ratio of 56.0″. And in addition, there is no need to shorten the existing chain and that means should I change the setup for a slightly higher gear in the future using a 13T sprocket, I won’t need purchase another, longer chain. I can always install the 44t/12T chainring/sprocket combination later if required.
But, another however. After unboxing this very yellow beastie, which is always a delight, I set about checking everything was working okay. And, as expected, just about everything was working okay, all except one item, the front wheel bearings. If you lift the front wheel off the ground, or in my case the spare room floor, and spin the wheel, you hear a very nasty grinding noise from the wheel bearings, which can also be felt through the handlebars. Not good at all and very annoying as I was keen to get cracking with the single speed conversion. Mind you, it’s -6 degrees in the shed, so perhaps not.
Comparing the front wheel to our other Brompton’s, the difference was quite marked, confirming that there was indeed a problem. So, I contacted Brompton and they also confirmed the bearings should not make any noise, and asked me to send a video clip, which I’ve done. Brompton also stated the issue could be rectified at a local Brompton dealer, which in my case would be Edinburgh Bicycle, or I could return the bike to them for an exchange. Now waiting for a reply.
Interestingly, the C Line Urban comes with an extended seat post, about 70mm longer than the C Line Explore. Something I didn’t realise when ordering. It does not come with a pump either, through that isn’t an issue. The longer seat post is. Not only does it mean the folded bike will not fit inside the Ikea Dimpa bag I need for carrying the bike on public transport but it also means I’ll have to adjust the seat height each time I unfold the bike, something I don’t need to do with the C Line Explore with its standard seat post. Looked at cutting down the seat tube length but it has a flared end so that’s out. So, will have to replace the seat post with a standard one. More another day.
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