Brompton vs Road bike speed / efficiency

[Tenkaykev]

There's an excellent YouTube channel created by Pam and Gilbert, a couple of folding bike enthusiasts. Loads of really useful information that's exceptionally well presented. The lates upload compares the performance of a Brompton compared to a road bike, interesting and informative.

View: https://www.youtube.com/watch?v=F98oQ7Xo5mI

 

[gom]

An excellent Brompton channel. I recently recommended their analysis of Brompton handlebar types to a friend, who was very impressed by the amount of detail.

 

[Kell]

What I've learned today:

Surprisingly, the deflection of the chain line to the largest sprocket is more efficient than running a straight chain line to a smaller sprocket.

 

[rogerzilla]

All derailleur bikes I've seen give a better chainline to the smallest sprocket. Ideally the chainring should lie in a plane halfway between the two, but it would hit the folded rear triangle before that.

I would have said 1mph difference from a road touring bike, a bit more for a road racing bike (the term "road bike" is moronic...is a Brompton not a road bike?!), M-type slower than S-type due to the upright position.

I gear Bromptons for about 57" cruising gear but I'd go for 60" on a road racing bike.

 

[mitchibob]

I love this, it's missing a couple of variables, like certain Surrey/Sussex roads roughness with little wheels compared to big ones, but the speed differential is really close to what I observe. One thing I don't quite understand though, well, there could be bunch of excuses this year, but on climbs that I'd previously a PB on Brompton, only one I've beaten when doing again on my road bike, and that was last year, when I was in good form. Fair enough, the weight of the two is similar, maybe the road bike is at most a kilo lighter. But I can't even attribute my PB on Box Hill to having any kind of draft from the Ride 100, as I set my best the week before, with no-one helping, plus, I just don't go fast enough up there to get a benefit from a draft. Coombe Lane today on road bike? I was faster on Brommie couple years back on a ride where it was the last climb after Coldharbour and Barhatch Lane, in January?!?! Just dunno how I did that now.

 

[GM]

Cor, my brain hurts now after watching that!

 

[ExBrit]

This is why I have drops and aerobars on my Brommie. They really work.

 

[12boy]

I would have liked a bit of data on the chainpusher options, thinking they may be a hair more efficient than the SA hubs. Other than that I was impressed with the article. I also wonder if my kind of riding, involving slowing and accelerating, might make a positive for Bompton small wheels.

 

[rogerzilla]

I was riding mine around central London this week and, the occasional pothole aside, they work better there than in the open country. You're constantly stopping for traffic lights (unless you're a local, in which case you NEVER stop for traffic lights) and the roads are smoother, in a kind of worn-out, polished way. Out here in the provinces, we have stuff like chipseal to contend with, and 16" wheels HATE chipseal.

 

[matticus]

This is why I have drops and aerobars on my Brommie. They really work.

But does it still fold nicely? (the biggest problem with the one I hired recently was a reach waaaay shorter than on my own bikes. Felt dreadful! And I much prefer drops to flats, AOTBE ...)

 

[ExBrit]

But does it still fold nicely? (the biggest problem with the one I hired recently was a reach waaaay shorter than on my own bikes. Felt dreadful! And I much prefer drops to flats, AOTBE ...)

Yes it does. The aerobars are quick release (on and off in 30 seconds) but still very solid to ride. I did have some trouble fitting them onto the S-bar and had to make my own shims from the bands of hose clamps wrapped in electrical tape. I've dropped the bars another 4cm since I took this photo. The drops fold on either side of the front wheel. And those pedals are quick release SPDs from FlatBike. Add a Brooks B17 and you have a bicycle capable of some serious miles.

It still fits in an IKEA Dimpa bag.

 

[matticus]

Yes it does. The aerobars are quick release (on and off in 30 seconds) but still very solid to ride. I did have some trouble fitting them onto the S-bar and had to make my own shims from the bands of hose clamps wrapped in electrical tape. I've dropped the bars another 4cm since I took this photo. The drops fold on either side of the front wheel. And those pedals are quick release SPDs from FlatBike. Add a Brooks B17 and you have a bicycle capable of some serious miles.

It still fits in an IKEA Dimpa bag.

View attachment 608522

Thanks. But how wide are those bars?? I know the wheels are only 'ickle, but still ...

 

[ExBrit]

It's a standard S bar (55 cm wide) with clip on drops from Amazon. I started with ergonomics drops from Origin8 but the flat sections were not in the right place for me so I replaced them with curved drops from Vincinta. It's a nice ride unless you're built like a linebacker. If you rotate them correctly you get a bar-end hand position as well as the drops.

There are tons of manufacturers that make Brompton compatable bars but I think going wider than 55cm might affect the fold.

 

[matticus]

Ah, clearly there is a world of Bromptom accessories I don't know about yet! (not crazy keen on drops with no brake levers, instinctive reaction)

 

[ExBrit]

You are absolutely correct. When I switch from my road bike to my Brompton and vice versa I find myself reaching for the brakes in the wrong place sometimes. I thought about replacing the Brompton brakes and gear shifters with higher quality generic ones, but decided that was too much. I'm surprised Brompton doesn't offer drops as a handlebar option.

In order to add drops you either need to cut off the end of the Brompton grips or replace them with Ergon GP1 or similar.