Dockhead

I had to take my Jetstream EX off my boat -- it just took up too much space, and although light, it was too awkward to haul out of the lazarette and into the dinghy.

I normally live on the boat 2 or 3 months in the summer and cruise around the Baltic Sea or European Atlantic coasts, and a bike is really, really useful as ground transportation, and also just for the fun of going for rides in places.

So I'm in the market for another folder, this time something with 16" wheels and a better more compact fold than my Jetstream.

A lot of sailors swear by Bromptons, and they certainly have a great fold. I'm just a bit skeptical about how well they ride. I used to knock out 50 mile rides on my Jetstream just for fun. I guess I could reduce my ambitions but can you ride a Brompton even 10 miles with hills?

Grateful for any advice.

Fentuz

Not sure about the packit but if this type of folding works for you, you may consider Dahon curve d3 and Dahon K3+.

When it comes to distance, I would say it is down to range and gear gaps. With brompton, a 6 speed should suit and if you want to push some miles, copy the chapter 3 spec to increase the ratio performance/comfort.

Dockhead

The 6 speed Brompton has a derailleur -- something I would like to avoid for a boat bike. I was always bending the derailleur on my Jetstream when I kept it on the boat. The chain was an awful mess, and I still have chain stains on one of my sails (:banghead) from it.

Maybe, however, the Brompton folds in such a way that the derailleur is protected, unlike my Jetstream? Maybe I could keep it in a bag so that it doesn't get chain grease on stuff?

What I'd really like is hub gears (like Alfine 8 or 11 speed) and a belt drive. But none of these super tiny folders come with that as far as I can see. The Pakit comes as a single speed with belt drive -- can you can get a hub motor. With the motor it still only weighs 30 pounds. That could be a solution.

OR -- there are Rohloff conversions for Bromptons. That would be something, but also $$$$

Dockhead

Here's where you can get hub gear and belt drive conversions for Bromptons:
https://www.kinetics-online.co.uk/fo...n-alfine-kits/
It's not cheap, but maybe worth it. £815 for the Alfine 8 speed with rear rack. Another £295 for the belt drive.
Rohloff is £1835. But I think total overkill for a Brompton. I think the Alfine will be fine.

Total cost for converted new Brommie with 8 speed Alfine and belt drive would be about £2300 or about $2800 which is not much different from Bike Friday Pakit.

Being happily carless I can afford to splurge a little on bikes.

Or to save a little coin, buy a used one. The whole drivetrain will be replaced so not hard to have it in nearly new condition.

Dockhead

Or a Birdy? Bit bulkier than Brompton, but looks like a very good fold and much less bulky than the Jetstream. Full suspension and 18", rather than 16" wheels. So should be much better for longer rides. Can be ordered with Rohloff. No belt drive possible, however, because of the peculiar folding system.

tcs

Dahon Curl D9. Folds smaller than a Brompton and way smaller than a pakit. Nine speed derailleur, adjustable bars and disc brakes for those 50 mile rides.

Or if you want an ebike, a Dahon Curl Ei4.

tcs

Here's James Stannard, setting a FKT for LEJoG (879 miles) @ 83 hours:



I didn't get this fellow's name. He rode the 750 mile/1200 km P-B-P this past August:



And here's uber cycletourist Heinz Stücke, Guinness Book of World's Records "Most Traveled Person":



A little jaunt by the Brompton factory personnel:

linberl

If $ is not an issue, get a belt drive pakiT. You can get roadie level gearing (whereas brompton limits you to 6), a lighter bike, no chain and no derailleur (IGH). NO issues. And a much longer frame warranty.

tcs

You've probably looked at the folded dimensions (cm):

Birdy: 80x34x62
Dahon Jetstream: 83x29x66
BikeFriday pakit: 96x25x61
Hummingbird: 117x20x60
Tern BYB: 81x33x51
Dahon Qix: 67x26x60
Brompton: 58.5x27x56
Dahon Curl: 58x27x54

Listed in descending order of total folded (XYZ) volume. Perhaps there's one dimension that's more critical to your space on your boat or dinghy.

Dockhead

Thanks, that's really useful!!

I'm really surprised the Pakit is so bulky!! That scratches that. And the Birdy it turns out is even bulkier than the Jetstream!!

What's critical on the boat is not really any one dimension, so much as low volume (the Jetstream takes up too big a portion of my lazarette, even on a 54' boat), and even more important -- that bits don't protrude out of it so that it can be smoothly fit in with other stuff (like sailbags), and you don't set it down on vulnerable bits like the chainwheel. And there's no derailleur sticking out like the Jetstream. So a well-fitting bag or case would be a huge plus.

I guess I'm back to the Brommie.

Dockhead

Very encouraging; thanks!

Dockhead

But the belt drive Pakit is only a single speed?

Jipe

The derailleur of the Brompton is not a real derailleur, it doesn't switch gears as fast as a real derailleur but no risk to damage it like a real derailleur. The derailleur of the Dahon Curve is much more exposed/prone to be damaged.

For the size of the Birdy, these are the values given by Riese & Müller with the saddle fully pushed to the rear to maximize the handlebar-saddle distance, i.e. the worst case size.

The size given by Pacific Cycles is 61cm(H) x 33cm(W) x 72cm(L) its what most user experience.

You can buy a fully equipped Alfine 8 or Alfine 11 or Rohloff Brompton from Kinetics Glasgow. It can also have a belt drive but since the transmission is protected between the two folded parts of the Brompton when folded its not really useful.

linberl

NOPE - 8 speed alfine belt drive

Bike Friday - Configure your 2022 pakiT Mk1B - 8spd belt

Dockhead

Great; thanks!

Dockhead

Thanks -- lots of really useful information.

I'm interested in what you say about the Brompton drive train -- so you mean that the chain and derailleur are all protected between the folded parts? So there's no need for either the hub drive or the belt drive? If so then I could just buy a standard 6-speed one which is much cheaper than anything else I'm looking at.

I was looking at Kinetics and the conversions are reasonable in cost. For about €2k you can really pimp the Brommie with Alfine, belt drive, disk brakes, new wheels, new fork. Just add a donor used Brommie and the cost is similar to Pakit with Alfine.

But best riding of all of these must be the Birdy. Just need to get my head around those dimensions.

tcs

Quote:

The derailleur of the Dahon Curve is much more exposed/prone to being damaged.

Quote:

...so you mean that the chain and derailleur are all protected between the folded parts? So there's no need for either the hub drive or the belt drive?

Here's the folded Dahon Curl:


As you can see, the derailleur and the chainwheel are buried deep within the fold.

Jipe

The derailleur of the Brompton is not a derailleur that hang under the left base like a usual derailleur, its a kind of small fork, there is no risk to hit and damage it.

The weak points of the Brompton are:
- comfort: if you have to ride on bad roads, cobbles, trails its really bad. The Birdy with its 50mm wide tires and suspension is excellent in these conditions. I am afraid that the Curl will be as bad as the Brompton for the comfort?
- efficiency: the 6s speed transmission is not very efficient (wide gaps between gears) but not only, the geometry+frame are less efficient too, I have a Rohloff on my superlight Brompton (rear titanium frame modified by Kinetics) and even so its less efficient than the Birdy with derailleur or Rohloff (the Nexus 8 Birdy is less good).

The hydraulic disc brakes of the Birdy are of course much better than the rim brakes of the Brompton. Kinetics can convert a Brompton to disc brakes but its a major weight increase compared to a Brompton with titanium fork and rear triangle. The Curl exist with disc brakes (there were many different iterations of the Curl).

Last point, for the use on a boat, an aluminum frame bike like the Curl or Birdy is probably better than a steel frame bike like the Brompton (there is also a latest T-line full titanium Brompton but its much more expensive and not available yet n several counties).

50PlusCycling

Another vote for the Dahon Curl. I recently took a Curl out for a test drive, and was impressed. I am a former Brompton owner, and I also have a Birdy and a Moulton. The Curl folds smaller, and more quickly than any of them. I like the simplicity of the Brompton, and it is a pleasant bike to ride about town. However, Bromptons don’t have a lot of gearing, and proprietary parts make upgrades difficult. The Curl has a funny “whale” shape, and due to it being made very ruggedly, is a little heavier than I expected. But much of the weigh comes from the 8 speed internal geared hub, and heavy crankset.

I decided to get the Curl for my wife, as I have enough bikes, and it is small enough that we can easily carry it when we fly around,

Jipe

I searched for the Dahon D9... and couldn't find anybody selling it !?

On the eu.dahon website its listed as a 2024 model.

When I look at it, I see three problems (besides the comfort, probably worse than the Brompton due to lack of rear suspension and stiffer aluminum frame):
- no front block bag carrier, same low rear rack as the Brompton that doesn't allow to carry rear pannier.
- chain tensioning when folded: its the old style Birdy system with a rear derailleur extension arm that was used on the Birdy 1 and Birdy 2 and never worked well.
- 11-28 cassette with 46t chainring this is much too short (5.56m max) and limited in range (Pacific Cycles mount a 52t chainring with 11-28 cassette on the Birdy and its too short, 46t is even shorter, Riese & Müller mount a 9-32t cassette + 52t chainring on the Birdy Touring and that's OK, wider range, longer gear inch).

Dockhead

I had not considered these before. Can even be had with an 8 speed Shimano Nexus internal hub. No belt drive, but packs up in a bag so maybe the chain is not a problem. Hmmm.

Fentuz

The brompton derailleur is much more compact with a very limited range of movement from the fork as Jipe mentioned.


The hanging mechanism you can see on all bompton is a plastic chain tensioner. When it comes to folding, the front wheel come to cover it so I believe it would take a lot to damage the system.
If bending derailleur/derailleur hanger is a real concern, ~5€ will buy you a cheap derailleur guard but I honnestly cannot see the point.


I'm not sure about the Rohloff, it is expensive, weighty, and I don't believe it increases the range that much. With these bike you cannot gain on the most important thing, aero so all you can do is light weight and low rolling resistance.
When I looked into brompton for commute (17miles each way with 2 15% hills, a S6L would have worked but it required a few mods inc carbon hollow crankset (more because I have to swap to 165mm to avoid knee pain and I want a bigger chainring), lighter tyres, seatpost, saddle and lighter front wheel (because I couldn't be bother to mess with the rear system).

If you want a speed bompton, you can copy the spec of the chapter3
If you want a "all road", you can copy the spec of the explore



By the way, is this yours?

Dockhead

Ha, not my boat, nor my bikes.

I would never keep mine on deck, and certainly not at the bow, where they would get drenched with seawater, which means quick death for any bike.

Jipe

The Rohloff offer the widest range for the Brompton, i.e. 1.54m to 8.11m with a 54t chainring and a 13t cog.

Its not much heavier than a 6s Brompton transmission, on my Brompton it added about 150g wrt. the original 6s transmission.

This is obtained using the original titanium rear triangle widened to 135mm by Kinetics.

Yes, its expensive but its reliable and has an excellent efficiency as good as a derailleur and allow to change gear while pedaling what is not possible with other IGH.

tcs

No one on the Dahon Curl Facebook group has complained about this, but if it was a problem for a particularly sensitive owner, an industry-standard component suspension seatpost could be fitted.