Best front chain ring for top speed on 20inch bike

[Bonzo Banana]

It's the welds that are failing on some Terns, not the frame material. Perhaps aluminium's low melting point, might make poorly skilled factories err too much on the side of caution? It's easy to mess up an aluminium weld. I certainly hope the OP reports back about his conversion. I think the steel framed Dahon is the Boardwalk. The Brompton fold patent has expired, I'm surprised more new folders aren't using that folding mechanism design. I can't cope with 16 inch wheels, and three gears are useless everywhere but parts of Lincolnshire, also while cycling on gigantic billiard tables which stretch forever in all directions - the former I actually fell asleep while cycling on, the latter I've had nightmares about... in both cases there was far too much endlessly boring green.

I wouldn't do any jumps with Dahon's Pandemic Special - no rebar:

Some of the Bromptons are just 3 gears i.e. just the SA 3 speed hub but others have the 2 speed derailleur system which gives them a wide range of gears similar to the Nexus 7 or Nexus 8. It's how Brompton got around the much reduced reliability of the Nexus 7 and 8 for long term use. Some may not like the 6 speed system with 2 shifters but its their engineering solution to the problem. The Nexus 7 is actually a 9 speed hub with 2 gears mapped out so is actually a lot less reliable than the Nexus 8 and only has a 244% gear range compared to something like 308% for the Nexus 8. I personally wouldn't use a Nexus 7 on a bike although admit I do have a folding bike with a Nexus 7 but I don't use it very much. I think I'm right in saying the Brompton has wider range gears than the Nexus 7 (with the 2x derailleur) but not as much as the Nexus 8. I haven't bothered to google to check though. Actually changed my mind just checked. 302% for Brompton and 307% for Nexus 8. Even the standard 3 speed Brompton isn't far off the Nexus 7 as its a wide ratio 3 speed hub.

https://en.wikipedia.org/wiki/Comparison_of_hub_gears

 

[guerney]

I've never tried a Nexus - my aluminium framed Dahon from 2006 (manufactured in April, according to it's frame number) has 8 speed SRAM X4, and even with a mere 250W bbs01b manages all of the steepest hills, despite the 52T chainwheel. Although I always curse and blame the derailleur during the adjustment of new cables, it's unfounded: reliable and accurate, and still working perfectly even after all these years. Older Dahons were better made. It doesn't feel like it'll snap in half, but I could be spectacularly wrong. Aluminium frames do eventually fatigue and crack, which is when I might try to source a less used bike of the same make and model - sadly they're rare these days.

 

[Nealh]

The pics of the Tern weld failures showed up poor weld penetration/depth and for the most part seemed to rely on ugly surface weld.

 

[djneils98]

BBSHD on a Tern .
Did you not do your homework and see the 300+ posts on one of the forums about Terns failing, more so once an ekit was added.

I doubt 300+ people have put a bbshd on a tern let alone had one fail doing it.
Mine is a Verge D9 model and brand new - it seems to be older Link models that had the frame fail - tern had a recall on them - I'll keep monitoring the frame though!!
Loving the conversion so far - fingers crossed they've sorted the frame issues!

 

[djneils98]

My 20" Dahon folder hasn't broken in half yet (I've even done a few jumps, had two crashes), but it has a "Rebar" reinforcement over the hinge and a mere 36V BBS01b... I'll stick to 15A, which is fast enough for me - no load top speed of 28.6mph, derestricted temporarily 22.4mph flat out on a private road on throttle (since disconnected), therefore I'm amazed the OP managed 32mph; cadence must be higher on the HD?

bbshd cadence is 160rpm I believe. Though I had a BBS02 750 on it previously and that wasn't much slower

 

[AndyBike]

I'd also think about upping the brakes if you intend on trying to take the bike to a higher speed. The rotors arent that big, and the brakes specced arent exactly that powerful. Too fast you might overwhelm the system.

Sorry, im a bit of a brake nut

Speed is nothing without control

 

[djneils98]

I'd also think about upping the brakes if you intend on trying to take the bike to a higher speed. The rotors arent that big, and the brakes specced arent exactly that powerful. Too fast you might overwhelm the system.

Sorry, im a bit of a brake nut

Speed is nothing without control

it seems to stop very well tbh

 

[Bonzo Banana]

I doubt 300+ people have put a bbshd on a tern let alone had one fail doing it.
Mine is a Verge D9 model and brand new - it seems to be older Link models that had the frame fail - tern had a recall on them - I'll keep monitoring the frame though!!
Loving the conversion so far - fingers crossed they've sorted the frame issues!

I'm sure it doesn't effect your newer Tern but some of the failures were quite funny. There was a russian forum where the father had given a Tern to his son with the idea that as his son grew he could just alter the height of the seat and handlebars etc so wouldn't have to buy him another bike for the next few years. I can't remember the age of the son '7' springs to mind and very light and the frame still failed although admittedly kids can treat bikes badly. Possibly one of the most comical failures because the boy was so light though.

I think it was on this forum

https://forum-velomania-ru

Фотографии сломавшихся рам и рулей складников

Похоже назрело. Публикуем здесь фотографии и ссылки на развалившиеся рамы складных велосипедов. Пусть будут в одном месте. Просьба вставлять картинки картинками, а ссылки на внешние страницы указывать только в качестве дополнения.

forum.velomania.ru

 

[djneils98]

I'm sure it doesn't effect your newer Tern but some of the failures were quite funny. There was a russian forum where the father had given a Tern to his son with the idea that as his son grew he could just alter the height of the seat and handlebars etc so wouldn't have to buy him another bike for the next few years. I can't remember the age of the son '7' springs to mind and very light and the frame still failed although admittedly kids can treat bikes badly. Possibly one of the most comical failures because the boy was so light though.

I think it was on this forum

https://forum-velomania-ru

Фотографии сломавшихся рам и рулей складников

Похоже назрело. Публикуем здесь фотографии и ссылки на развалившиеся рамы складных велосипедов. Пусть будут в одном месте. Просьба вставлять картинки картинками, а ссылки на внешние страницы указывать только в качестве дополнения.

forum.velomania.ru

lol. that link doesn't work for me.
The part where the frame folds on my bike is pretty chunky compared to older Terns from a few years ago. Hopefully the fails and subsequent recalls have resulted in better design

 

[Nealh]

No one said anything about 300 kits or bikes, just that the thread had 300 odd pages to it.
Some used mid drive and some hubs, One UK women was on holiday in france and her tern had no kit yet it broke, she said as alight weight is scared the pants out of her as she had just pulled up to a stop and suddenly the frame gave way, seconds prior to that she was wizzng down a hill quite quickly as she put it.

 

[guerney]

No one said anything about 300 kits or bikes, just that the thread had 300 odd pages to it.
Some used mid drive and some hubs, One UK women was on holiday in france and her tern had no kit yet it broke, she said as alight weight is scared the pants out of her as she had just pulled up to a stop and suddenly the frame gave way, seconds prior to that she was wizzng down a hill quite quickly as she put it.

You're right, many weren't even conversions:

 

[djneils98]

No one said anything about 300 kits or bikes, just that the thread had 300 odd pages to it.
Some used mid drive and some hubs, One UK women was on holiday in france and her tern had no kit yet it broke, she said as alight weight is scared the pants out of her as she had just pulled up to a stop and suddenly the frame gave way, seconds prior to that she was wizzng down a hill quite quickly as she put it.

Sorry you originally said 300+ posts and it sounded like they were from Tern owners whose bikes had failed. But now I see it's gone from 300+ posts to 300+ pages in a day!
But seriously - tern obviously had some issues on bikes made perhaps 5 years ago or more - I can' see any reports of bikes make in the last few years failing.They had recalls (over 1700 bikes) and I would expect a large manufacturer to take the issue seriously and rectify the problems in the design of bikes going forward. Mercedes cars from the early noughties had serious rust issues but. no-one would say today 'don't by a merc as they all rust' would they?

 

[Nealh]

A merc didn't break in half though whilst driving it, the analogy is pointless when we are talking of potentially serious quality flaws in a bike design.

Yes, it was 300 +posts not pages. Only 2 or 3 years ago one of the gsd/hsd models suffered the same failure.

 

[djneils98]

A merc didn't break in half though whilst driving it, the analogy is pointless when we are talking of potentially serious quality flaws in a bike design.

Yes, it was 300 +posts not pages. Only 2 or 3 years ago one of the gsd/hsd models suffered the same failure.

sorry if the anology went over your head. I'm just saying a little hysteria goes a long way sometimes

 

[Nealh]

Horses for courses, I'm simply not a fan of folding bikes.
Tern took along time to accept any liability and initially dismissing failures to user misuse, it was the yanks who filed a law suit that eventually got Tern to own up to failures and recalls.

 

[djneils98]

Horses for courses, I'm simply not a fan of folding bikes.
Tern took along time to accept any liability and initially dismissing failures to user misuse, it was the yanks who filed a law suit that eventually got Tern to own up to failures and recalls.

sure - I'm not sure anyone is a fan of folding bikes. For me having one was a necessity as I need to regularly stick it in the back of a taxi. I'd have much preferred a bigger bike.

 

[guerney]

sorry if the anology went over your head. I'm just saying a little hysteria goes a long way sometimes

I sincerely hope that your Tern doesn't snap in two from the torque of the Bafang HD, or because of generally poor welding! But if it does, I trust you'll upload photos and a long thorough gripe about it all here.

 

[djneils98]

I sincerely hope that your Tern doesn't snap in two from the torque of the Bafang HD, or because of generally poor welding! But if it does, I trust you'll upload photos and a long thorough gripe about it all here.

Well it's been almost a year so far and fingers crossed. I can't see why the torque of the motor would put any stress on where the part of the frame that's failed fails given the motor and drivetrain are all attached to the rear section of the bike. As others have said the frame issues affected more standard terns than ones that have been converted. I think whether they were converted or not is irrelevant to the failures. But of course if it does break I will make you happy and post pics of all my injuries!

 

[guerney]

Well it's been almost a year so far and fingers crossed. I can't see why the torque of the motor would put any stress on where the part of the frame that's failed fails given the motor and drivetrain are all attached to the rear section of the bike. As others have said the frame issues affected more standard terns than ones that have been converted. I think whether they were converted or not is irrelevant to the failures. But of course if it does break I will make you happy and post pics of all my injuries!

If you weren't aware of Tern welds failing before, you are now! Inspect regularly for cracks... Hearing of your bike breaking and anyone suffering injuries would make me unhappy, for a time, I think - as I said, I get a bit of creaking from my folding Dahon bbs01b conversion at the onset of PAS, but only at the higher settings... weirdly it sounds like it's being emitted from the handlebar stem, but of course it could be that it's being transmitted via the frame from somewhere else. I expect it won't snap, because it's survived two crashes so far and the frame and welds seem fine. I'll ride it till it breaks, which seems to me highly unlikely.

 

[guerney]

Well it's been almost a year so far and fingers crossed. I can't see why the torque of the motor would put any stress on where the part of the frame that's failed fails given the motor and drivetrain are all attached to the rear section of the bike. As others have said the frame issues affected more standard terns than ones that have been converted. I think whether they were converted or not is irrelevant to the failures. But of course if it does break I will make you happy and post pics of all my injuries!

Perhaps high torque would flex the frame toward the motor side, and at some angle? It's significantly higher torque than a normal rider could exert, and there would be more frame flex at high PAS and throttle acceleration settings? And if the welds aren't strong enough in the middle of the frame where those welds are, that part of the frame could fail, I suppose. Whatever, the proof will be in the pudding.