# Brompton vs Road bike speed / efficiency



## Tenkaykev (4 Sep 2021)

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


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## gom (4 Sep 2021)

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.


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## Kell (6 Sep 2021)

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.


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## rogerzilla (6 Sep 2021)

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.


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## mitchibob (8 Sep 2021)

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.


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## GM (8 Sep 2021)

Cor, my brain hurts now after watching that!


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## ExBrit (9 Sep 2021)

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


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## 12boy (9 Sep 2021)

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.


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## rogerzilla (10 Sep 2021)

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.


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## matticus (10 Sep 2021)

ExBrit said:


> 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 ...)


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## ExBrit (10 Sep 2021)

matticus said:


> 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.


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## matticus (10 Sep 2021)

ExBrit said:


> 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 ...


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## ExBrit (10 Sep 2021)

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.


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## matticus (10 Sep 2021)

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)


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## ExBrit (10 Sep 2021)

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.


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## mitchibob (11 Sep 2021)

ExBrit said:


> 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



It's well capable of serious miles without aero bars, and having used them on road bike recently, really like to have a really smooth, straight-ish road, and with Brommie, think I could only use them on a track. They definitely work, but can be terrifying... certainly don't blow my nose using them.

That said, could you clip them on and unclip them fast enough to do an hour record where bike had to be folded at the start and end of the hour, with the time saving of using them during the hour? I really think a brommie hour record, where bike should be folded start and finish, could but fun to see. Well, the start and the end ;-)


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## Kell (14 Sep 2021)

ExBrit said:


> I'm surprised Brompton doesn't offer drops as a handlebar option.



I have to say - I'm not that surprised.

The Brompton may be a capable bike in other scenarios, but it is first and foremost a city/commuter bike.

Things like an Airnimal Chameleon would be a much more effective fast, folding bike - especially taking on board some of the learnings from that video about friction angles and rolling resistance.


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## T4tomo (14 Sep 2021)

matticus said:


> 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 ...)


I only commuted on mine, but S- bars with (stubby -so allow the fold) bar ends, got you into a reasonable position, with not to far to reach for the brakes, without going to the excess of fitting drops. You also need time to get used to a Brommie if you've never ridden one.


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## Kell (14 Sep 2021)

matticus said:


> 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 ...)



Don't say that to Berlinonaut, he won't have it.

I also felt the same with mine - so I fitted some old school bar ends from one of my MTBs. 

What I would say as a word of caution though is that I deliberately went for an (old version of the ) H-type because the hinge is higher up the stem. On the original bike this meant the higher bars didn't catch the ground when folded. But I also gambled on it meaning that when I fitted lower, wider bars and bar ends, it would mean I could still fold it. 

Which it did...


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## rogerzilla (15 Sep 2021)

If you want a faster bike with 16" wheels, try a Moulton F-frame. Not the easiest things to work on, and phenomenally heavy in their original state with chromed steel kit, but poor road surfaces don't upset them due to the full suspension.


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## Kell (17 Sep 2021)

I have to say, I thought they'd put too much emphasis on friction and rolling resistance, and not enough on aerodynamics. But I was watching it while doing something else, so they may be correct.

However, I take my basis from watching the Guy Martin 'Tandem' documentary where they tried to beat the record for the furthest travelled in 24 hours on a tandem. They didn't really bother trying to reduce rolling or mechanical resistance as they accounted for such a small proportion of what would actually slow you down. They interviewed Mike Burrows and his figures were:

90% air resistance.
7% rolling resistance
3% mechanical resistance.

From about 5:15 in the video below.


View: https://www.dailymotion.com/video/x3g0lqm


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## Kell (17 Sep 2021)

PS - I'm also very jealous of Guy's Orange Carb O


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## rogerzilla (17 Sep 2021)

The percentage due to air resistance is higher at higher speeds, though. For most Brompton riders, it's probably 50%.


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## matticus (17 Sep 2021)

rogerzilla said:


> The percentage due to air resistance is higher at higher speeds, though. For most Brompton riders, it's probably 50%.


Yup. the quote above doesn't mention that the 24h record will be well above 20mph. Average amateur/leisure Brommie ride? Quite a lot slower, I predict - and it's a v^2 realtionship ...


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## rogerzilla (21 Sep 2021)

I volunteered to help test some proposed new road markings/rumble strips today and took the Brompton as they wanted a wde variety of bike types. The Brompton was actually no problem due to its wideish Kojak tyres, although the vibrations did make the rear end clank once (no clip, hard suspension block). Apparently the road racing bike on 23mm tyres was more inclined to get upset.


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## ExBrit (21 Sep 2021)

I think it's great that people who make these decisions are asking cyclists for input. Thanks for representing us. Where I live, CalTrans just does whatever they feel like, so it seems. Don't you love the way this bike lane ends in a row of parked cars with no warning?


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