Abu Mahendra

I wonder, have those problems been rectified in the MkIII version?

astage

Not had that, but have had half-a-dozen people query if it is one of those 'new fangled electric bikes'. Possibly because I have a top pack on the rear rack - the only place for the drinks, etc. - and no obvious gears being a Rohloff.

ttakata73

An easy way to check front end flex is to push the bike against a solid wall, weight the bike, and push forward on the bars while looking down the stem towards the brake. I can clearly flex the Brompton stem enough to block my view of the brake when I push forward. On my cheap Dahon Dove I can see it flexes much less because the stem is tapered and actually clamps the outside of the steerer tube. I can't detect any front end flex on my Hooligan which runs a 1.5" steerer; it's built like a tank.

It's probably not the Brompton's stem flexing much but the loose quill clamping interface that magnifies the top of the stem's movement. A quill stem only presses against a small portion of the steerer's inside (smaller diameter) surface whereas threadless stems clamp the entire outer (larger diameter) surface of the steerer. Bottom line it's a poor design that the rest of the bike industry left behind, but Brompton is too cheap to update.

Regarding the Birdy issues above:
3) not much frame clearance. Clearance for what?
4) not much tyre clearance if fit wide tyres. My Gen3 GT comes with 18x1.9" tires which is OK for me. Wider tires force a wider fold so it has to stop somewhere.
5) alloy frame get worn away if chain line incorrect Yes, biggest chainring I can fit is a 58t (still too low a gear). Any bigger and the chain will start eating the swingarm when on the 32t cassette. Hopefully whenever Gen4 is done they realize it needs gearing to match a regular 700c road bike and redo the entire rear swingarm.
8) stupid chain catcher can get bent and jam in rear cassette, breaking derailler, Gen3 moved this to the bottom bracket.

chagzuki

I've been saying this for years on this forum. This aspect needs a redesign, but this flex is in fact softening the ride considerably. So once frame stiffness is optimized a new rim format with wider tyres would be necessary to improve the ride quality and with that rolling resistance. It's accepted wisdom now that wider tyres roll better, and on such small rims running narrow tyres is plain silly. I'd summarize the thread dedicated to figuring out why Brompton's are slower than other folding bikes roughly in this way: the Brompton frame is providing the suspension rather than the tyres, the rider's energy is going into flexing the frame and the tyres roll poorly.

rumrunn6

it is at home w/o me on it

Schwinnsta

I think a good part of the loss is the shock but I am not sure how comfortable it would be with out it. It would be nice if the Brompton accepted wider tires but I only see one company, Greenfield 16x1.5. It would be nice to be able to run these and still have fenders.

Rick Imby

Dahon MU D10 Problems
Lazy---barely gets out of the garage
Scared of water---Super Rainy spring won't leave the garage
Slow---Doesn't seem to climb hills well at all
Sneaky--folded up and hiding behind all my other bikes
Flabby---went back to original tires and wheels and she is much slower
Jealous--sitting behind the new 27.5+ mountain bike that seems to get all the miles

avole

I think you have this wrong. Which handlebars do you have? The only references seem to be yours, and I admit I didn't spend much time on this, and a blogger whose theories re suspension are eerily close to yours. However, there is a case that, in the case of the M handlebars, they do flex, which isn't so surprising given their design. You're also wrong about accepted wisdom, since there is now a backlash about small/wide tyres and rolling performance, which, as I'm sure you'd agree, dependent on a number of factors. If the Brompton is slower than other folders with the same size wheels, I'd blame riding position more than anything else.

Anyway, in the interests of research I'll contact Brompton next week and see what they say.

chagzuki

I think the rear suspension is a net gain and therefore increases speed overall. It's a matter of tuning the firmness for your weight/conditions.

chagzuki

I'm using a third party bar, there's no flex in it. But the bike was originally an M-Type and I switched that out for an S-stem plus Aberhallo extender to arrive at a similar height bar. I was disappointed to find that flex felt the same. I've ridden many Dahons too. They all flex to some degree, and I found that the amount of flex in a Brompton was comparable to a Dahon Curve. 20" Dahons flex less but since the stem is aluminum in some ways it feels worse/less healthy. Tern Beefed up this aspect of the bike (look at their design) and other Brands have switched (including Dahon on the Curl) to a stem/handlepost that integrates the steerer, which it seems to me is the logical conclusion of folding bike design. Technology like oldy wedge stems are absurd.

avole

It seems odd to me that few people, at least on the internet find any flex with their Bromptons. Nevertheless, it'll be interesting to see what the manufacturer has to say.

Abu Mahendra

what's the wheelbase of the Spin 2?

splithub

..it has horizontal dropouts, 800-830mm.

chagzuki

I guess it's not a concern for many people. For instance, if you look at forum recommendations for choosing between Tern bikes and Dahons they tend not to lean in either direction, despite the fact that Tern prioritized certain factors that in their opinion would make for an improved product. The rotation of the front fork on folding makes for a more compact fold, and other changes increase stiffness but also increase weight. Consumers don't seem to be too concerned with these differences. Ten years ago Dahon had a maxim on their website claiming they aimed to improve their bikes by 10% every year. In the last 8 years most of their bikes haven't changed at all, and they've abandoned that marketing slogan. It seems the market has reached a plateau, but in my opinion there's still scope to take the Brompton design to its logical conclusion, which would result in a much improved machine: faster and more comfortable.

Schwinnsta

If Brompton were to make a major remod I would put the stem first on my list. Although, not critical of the flex, I agree that they should update the attachment at the base. However, I would like to see them add adjustabality to to the stem using a system like Tern's Androse stem. Also, 16-305 with wide tire capable. They could do this but it would be a lot ask.

kidshibuya

What backlash? Road bikes are going wider and wider, we have gone from 19mm to 32mm not being uncommon. Right now 25mm is standard but this jumps to 28mm for the bumpier races, and this is with 700cc wheels, the trend is clear (and pro cycling is always decades behind). Scale it down and you need even wider since the bumps are relatively higher. You need to think about what vibrations and the shaking that high pressure tyres produce actually is. If you and your bike are being pushed up every time you hit a bump because your tyres arent deforming then where do you think that energy comes from? It isn't free. You and the bike might weigh 90kg, each bump is lifting 90kg up. It isn't magic, the energy to do so is being directly taken from your forward momentum. Run lower pressure and you are only losing the energy needed to deform the tyre rather than lift you and the bike...

avole

Try reading some of the posts on the Road forum.

tds101 

Dahon Speed 3i (custom build): I hate that, at the time, I didn't have access to an 8 speed hub. I need 8 speed for this to be my full-time commuter.

Dahon Curve: I luv this bike,...BUT,...I'm not able to convert it to an 8 speed because my original wheel builder retired. I'm contemplating my local LBS, as they're excellent. Also, the handlebar stem I swapped from the original flexes a bit much.

Dahon Speed P8: I swapped the rear shifter, and it shifts PERFECTLY - except that I need to cycle it through all the gears a few times before I ride first. The issue is the internally routed cables bind up, and the ones I have now are brand new, and heavily lubed inside the housing. It's just to much of a bend when folded. Makes me hate taking her out for a spin.

Tern Joe P24: It's HUGE!!!

Abu Mahendra

Would ISO355 not be a better choice?

Schwinnsta

I had not thought of that as I have never had a bike that fitted them so I am unfamiliar with what is available. I would not want to increase fold very much, though.

Abu Mahendra

Taking Schwalbe as a guide, its website shows the following in terms of tire availability by ISO size:
355: Eight tires ranging 32-50mm in width
349: Four tires ranging 30-35mm in width
305: Eight tires ranging 40-57mm in width

​​​​​​To my mind, the move ought to be to 355.

avole

Abu Mahendra

You're right. Brompton's got a captive audience, a cult-like following, hence insensitive to price, and indifferent to continuing evolution and improvement of the product. And besides, increasing the wheel rim diameter by six millimeters, less than a quarter of an inch, from 349mm to 355mm without appreciable increase in folded volume is beyond the technological prowess of the Brompton.

Nachoman

I don't care for the triple, up front, on my Bike Friday Pocket Rocket.
The drop on my handlebars is also way too deep.
All remediable.
But since it functions fine, I don't want to spend more money on this bike.

bhkyte

If I still had a Brompton I would put about how much the stem flexes.
not a problem on my Birdie or Mezzos.
other than that all my Bromptons have been perfect.
thats why I have sold 3 and not replaced them........