Best front chain ring for top speed on 20inch bike

So I have a Tern Verge D9 that I've put a BBSHD on.

Currently I have a 52T chainring on the front.

The smallest rear cog is 11T but currently the bike gets max speed in a higher rear cog.

Would I get any increase in max speed by going for a smaller front chain ring (say 44T or 46T) and utilising the 11T rear or will it not really matter?

smaller front chain ring will give you better climbing and a bigger one will give you more top speed.

 

you not got the programming cable ? as at max power that motor can get to 70-80kph if geared for that speed.

smaller front chain ring will give you better climbing and a bigger one will give you more top speed.

 

you not got the programming cable ? as at max power that motor can get to 70-80kph if geared for that speed.

HI - yes I get the general principle but was wondering if the BBSHD's max cadence was being held back by my current set up. The bike can get to about 32mph flat out - it only has 20 inch wheels. I think max speed for a BBShd on a full size wheel bike is about 40 - 45mph ish so maybe I am at the upper limit.

I have the egg rider so can adjust settings and it's pretty much maxed as far as I can see

tbh with wheels that size you are pushing it to the limit as going much faster and you could go in to a speed wobble.

 

but if you get the programme cable you can up the amps with the software if the batt can handle that amount of load non stop.

 

 

tbh with wheels that size you are pushing it to the limit as going much faster and you could go in to a speed wobble.

 

but if you get the programme cable you can up the amps with the software if the batt can handle that amount of load non stop.

 

the amps are set to 28amps which is the max the controller allows (its the 52v version)

The bike feels very stable at that speed

if you are at max amps then you will need to change the controller but 28 amps seems a bit low to me for the stock controller?

 

https://electricbike-blog.com/2017/01/02/too-much-is-never-enough-reprogram-your-50-amp-luna-ludacris-bbshd-controller-to-run-at-60-amps/

 

https://electricbike.com/forum/forum/kits/bafang-mid-drives/253-bbshd-program-above-30a

if you are at max amps then you will need to change the controller but 28 amps seems a bit low to me for the stock controller?

 

https://electricbike-blog.com/2017/01/02/too-much-is-never-enough-reprogram-your-50-amp-luna-ludacris-bbshd-controller-to-run-at-60-amps/

 

https://electricbike.com/forum/forum/kits/bafang-mid-drives/253-bbshd-program-above-30a

28 is what they come with on the 52v BBSHD and 30 is what the 48v ones come with

The guy in the video you posted isn't using the stock controller and I don't want to change the stock controller

Edited March 27, 20224 yr by djneils98

you will need another controller with more amps output if you want more top speed but can your batt handle a 50a load or more cos if it cant it will explode lol.

 

 

https://trampaboards.com/1-x-vesc-6-mkv--p-27529.html

 

https://www.youtube.com/watch?v=ZSPbBZeZARg

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.

80T? Not sure if these are compatible - I don't like the idea of a collision while riding a bicycle at those speeds

 

https://www.dutchbikebits.com/alligt-chainrings-60bcd

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.

 

 

 

 

 

Edited March 28, 20224 yr by guerney

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?

Edited March 28, 20224 yr by guerney

David Hon /Dahon bikes are safe and have a good welded hinge design, when the acrimonious split occurred with his then wife and a son they jumped ship. Apparently taking some of the company designs to form Tern bikes, one bit of the design they didn't manage to take apparently was the hinge fold plans and hence since Terns have suffered quite a few recalls due to hinge failures.

 

Those pics Guerney are just a few of the failures that have occurred with adding e kits to Terns and even a gsd e tern has had a massive failure just like that bbs one. The last time I read the Reddit page on the issue it was as I mentioned some 300+ posts long , not sure how much it has grown by now.

David Hon /Dahon bikes are safe and have a good welded hinge design, when the acrimonious split occurred with his then wife and a son they jumped ship. Apparently taking some of the company designs to form Tern bikes, one bit of the design they didn't manage to take apparently was the hinge fold plans and hence since Terns have suffered quite a few recalls due to hinge failures.

 

Those pics Guerney are just a few of the failures that have occurred with adding e kits to Terns and even a gsd e tern has had a massive failure just like that bbs one. The last time I read the Reddit page on the issue it was as I mentioned some 300+ posts long , not sure how much it has grown by now.

 

Yikes! ...and the last sort of failure you'd expect or want on a e-cargo bike! Quality and design were much better when Mr Hon was alive - that man was obsessed with folding bikes. The guys I buy my Dahon spares from (chiefly because I can't buy them anywhere else), have been selling Dahons and Terns for many years, and they tell me that very few bikes suffer hinge breakages if they feature a "Rebar", like this one (mine has 20" wheels and 8 gears, but the frame is similar). It's not especially aesthetically pleasing, the rebar, and I think that's why the newer Dahons designs don't have it. My bike does seem to creak a little at the handlebar post when the PAS switches on, but it could be my aged knees. The older Dahons generally had longer wheelbases too, and rode almost like real bikes (with added squirrely). Tern have been buying up Dahon trademarks for years, pretty soon it'll all be Tern. One could say it's taking a Tern for the worst.

 

 

 

https://foldingbike.biz/epages/7665e38c-067c-4fa0-9037-afac2266f927.sf/en_GB/?ObjectPath=/Shops/7665e38c-067c-4fa0-9037-afac2266f927/Products/DAHCUSPRESTOD3SLUSED

David Hon is still alive and still Dahon ceo.

David Hon is still alive and still Dahon ceo.

 

Whoah! Lol, why did I assume he'd died? Maybe he doesn't get as involved in design anymore or something, but Dahons were much better a couple of decades ago.

The close up pics of all the Tern failures seem to indicate a poor welding process of the hinge to the frames, esp with the weld depth barely looking like it has penetrated enough. Most of their welding was out sourced all over the place so QC was very poor.

The close up pics of all the Tern failures seem to indicate a poor welding process of the hinge to the frames, esp with the weld depth barely looking like it has penetrated enough. Most of their welding was out sourced all over the place so QC was very poor.

 

Aluminium isn't easy to weld in general, so when I had to make a swivelling technical drawing table at school, I made T and L blocks with long inserts for aluminium box section with nylon instead, also nylon hinges. The joints aren't even glued - the long nylon inserts can (eventually) be pulled out for the table to be disassembled, so my welding ineptitude made for a more useful item. I prefer things which fold or disassemble to pack away anyway.

Whoah! Lol, why did I assume he'd died? Maybe he doesn't get as involved in design anymore or something, but Dahons were much better a couple of decades ago.

 

Like many brands Dahon buy most of their bikes from other factories although they do have a mainly assembly plant in China now but they buy their bikes from other factories and this does mean price wise they are quite high for what you get. When Halfords used to sell Dahon folders they sold a model at about £450 which had very low end components yet did their own Carrera model with much higher quality components for £350. They soon stopped selling them as you can imagine. Tern seem to set themselves up as a more performance orientated folding bike company so push for lower weight designs and being a newer company perhaps have chosen a few poor factories by mistake. I saw the recall information and it was specific to models made by one or two factories not all and some of the same models were recalled and others were not.

 

In Europe many Dahons come from Max.com in Bulgaria but its mainly an assembly plant using parts from Asia. This is probably to avoid any tariffs.

 

Anyway my point about Dahon is quality varies by the factory used same as most US and European brands they may change factories regularly and use different factories for different price points.

 

I'm not sure which brand makes the best strongest folding bikes but steel folding bikes have three major advantages one is steel is more compact so can be made into a smaller folding bike, it's a denser material and the other is hinge mechanisms seem far superior made out of steel they seem to last longer than aluminium with far less fatigue issues and thirdly steel is more durable so can take the abuse of being bashed about which often many folding bikes endure. There is a weight advantage to aluminium but far less than other bike types as aluminium has to be more overbuilt in a folding bike so you lose some of the weight advantages.

 

It's like the Brompton vs the Dahon Curl they look very similar as Dahon has copied the Brompton but used aluminium instead. The Curl is a horrible folding bike, its heavier, weaker and rides terribly with a very harsh ride and will likely not last anywhere near as long. The Brompton has a flexing steel frame made from different steels at different points brazed together to get the right feel and also has a rear suspension system. A surprisingly comfortable bike despite its small wheel size the Curl sadly isn't like that. Also some Curls used the fairly unreliable Nexus 7 hub which compromised long term reliability. Bromptons typically use a fairly bomb proof 3 speed Sturmey Archer hub with or without a 2 speed compact derailleur system.

 

Anyway my point is Dahon do a steel folding bike (I forget the model name) but its the reputation for being a more durable model and you will recognise it by it's more compact tube profile.

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:

 

 

Edited March 30, 20224 yr by guerney

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

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.

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.

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!

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