Conversion kit on folder - TSDZ2 or other?

[Bogmonster666]

I am trying to convert my decrepid old mountain bike to a rear hub but also started looking at my folding bike. Its a Tern (Dahon derivative) 20 inch wheel with an 8 speed cassette Anyway the drpouts front and rear are not standard sizes and I know there are front hub motors that will fit but I think they are a little hard to come by at the moment.

I know other have installed a TSDZ2 CD and I think that would be my preferred option. However, I think with the standard chainring supplied (which I think is already dished) then the chainline will be way out of whack making the lower half of the cassette unusable. Has anybody managed to source and fit either a chainring with greater dishing or found some other solution such as a spacer? I don't think I will bother with the TSDZ2 option if I can't find a solution for the chainline.

I may still consider a hub but stetching a 75mm front aluminium front to 100mm does not sound like a good plan. I think the rear droputs are 125mm but will check - they are not 135mm.

I suspect that I may not find a satisfactory solution for this bike so if I am hell bent on a folding bike conversion then I may need a new bike - and not in a position to justify that kind of outlay at the moment.

The reason for the folder is that I travel to Bristol quite frequently and it is a bit too far by bike, and few ebikes bikes will have the range for the round trip I expect. Today I catch the bus but I get a lift to and from the bus stop which is still a far way - I live in the middle of nowhere. A folder would solve this problem. However, unless I can find a cheapish solution I will carry on getting lifts or just cycle under my own power to the bus stop.

BM

 

[Nealh]

A Tern (an attempted copy of Dahon by design) would be the last bike I would put a mid drive on esp as they snap in half due to the extra motor stress.

 

[Woosh]

I know other have installed a TSDZ2 CD and I think that would be my preferred option. However, I think with the standard chainring supplied (which I think is already dished) then the chainline will be way out of whack

can you check the chainline on your folding bike? measure the distance between the middle of the seat tube to the chain ring.
The chainline on the TSDZ2 is 50.2mm

 

[Bogmonster666]

That would be unwelcome. I thought it might be ok as the bottom bracket and the rear wheel are all in the same back half of the frame behind the hinge? I can certainly see that spanning the frame hinge would be a bad idea...

 

[Bogmonster666]

can you check the chainline on your folding bike? measure the distance between the middle of the seat tube to the chain ring.
The chainline on the TSDZ2 is 50.2mm

OK, just found a better measuring stick, BB is 68mm and chainline is ~42.5mm so not too far off.

Any thoughts on the Neath's comment about frame strength given the BB is in the same half of the frame as the rear wheel?

BM

 

[Nealh]

If one searches the www. one should find pics of snapped Tern frame sthat have been converted to E bikes.

 

[Bogmonster666]

If one searches the www. one should find pics of snapped Tern frame sthat have been converted to E bikes.

I know a number of Tern farmes were recalled and replaced (mine included) because of a problem in a weld. My understanding was that the replacemtn frames were OK for regular use but you may well be correct in that they are not up to a mid-drive motor. Do you beleive this is a Tern specific issue or a more general issue with folding bikes?

Here is a link to a sheared frame: https://ternframefailure.forumotion.com/t2-tern-link-d8-frame-shearing-in-two

 

[Bogmonster666]

I know a number of Tern farmes were recalled and replaced (mine included) because of a problem in a weld. My understanding was that the replacemtn frames were OK for regular use but you may well be correct in that they are not up to a mid-drive motor. Do you beleive this is a Tern specific issue or a more general issue with folding bikes?

Here is a link to a sheared frame: https://ternframefailure.forumotion.com/t2-tern-link-d8-frame-shearing-in-two

Having read some more I think frame issues persist on other Tern bikes. It looks like the recalled frames are 'probably' OK but it does not make me feel good about using the bike. Tbh I had stopped cycling for a long time due to ill health and have not used the folder after the frame was replaced. I agree, it is probably not a good candidate. Kind of not feeling too confident about using it much at all really now....

It does also appear that Term appears to be more effected by frame problems than other manufacturers of folders...

 

[Woosh]

Any thoughts on the Neath's comment about frame strength given the BB is in the same half of the frame as the rear wheel?

I assume they had a bad batch with the material the main tube is made with.

 

[Bogmonster666]

I assume they had a bad batch with the material the main tube is made with.

I have not seen any reports on the replacement Tern link frames failing, and all the failures I see are in front of the hinge and not particularly in an area that would be stressed by a mid drive motor - but still my confidence is knocked a little...here is a link to the recall notice for these bikes in the US: https://www.bicycleretailer.com/recalls/2014/06/25/tern-recalls-about-1-700-folding-bikes-because-frame-concerns#.YulNnITMKM8

Rather disturbingly in 2016 they had a recall on their higher end bikes as well: https://www.bikefolded.com/tern-verge-eclipse-folding-bikes-recalled/

As I say, I think the original 2014 recall did resolve the issues on the Link bikes and all the failures were forward of the hinge - but it is a worry...

 

[Nealh]

https://www.reddit.com/r/ebikes/comments/bbaayg

 

[Woosh]

all the failures I see are in front of the hinge

the underside is where the loading stress pulls open the two sides of the main tube (tearing).
Aluminium is sensitive to hot fracking. That's why if the top tube is convex, I much prefer it is made from steel rather than brittle aluminium. Alternatively, have a concave top tube plus a very substantial box section.
Just seen the pic that NealH posted. Put me right off adding any mid drive to the Terns.

 

[Nealh]

That pic/incident pulled from Reddit, there was an official Tern forum which they pulled. It had one thread with over 300 pages about failures inc ebike conversions.
Even as late as 2018/19 there was pic of a Tern gsd e bike with the bosh mid drive, it also broke in half.

 

[Nealh]

Before I bought the Ute, Tredz had a Tern node cargo bike reduced from 1900 to 1250. I nearly hit the buy button, then I saw the pic above .

 

[guerney]

I wouldn't put a mid drive on a Tern. Perhaps @Woosh has a suitable front or rear hub? I probably would have installed one of those, had I have been able to find one in the UK. I might still, and put the bbs01b on to a mountain bike. Despite my worries, my 2006 Dahon Helios P8 with bbs01b continues totally unsnapped - 3113km so far, some while towing a 65.5kg trailer, many while carrying very heavy veg. It's survived the odd small jump, three collisions. I worried about a creaking noise, but this turned out to be a loose motor nut (the big one) and a stiff hinge - the Bafang tool and oil sorted that out. It's such an old bike hardly anyone has heard of, so here's a link:

World Wheels - The No 1 internet source for Dahon Folding Bikes in UK and EU

World Wheels: Online Retailer of Dahon folding bicycles. We carry Dahon's complete line of portable folding bicycles and folding bike accessories.

www.cyclemotion.co.uk

 

[Bogmonster666]

I would think the obvious way forward is to look out for a used Dahon or similar if I am serious. Not worth taking the risk with the Tern. They did add an additional strengthening part to the replacement frame but in the picture above you can see this is one of the more recent frames with the added strengthening piece. Tbh the ride to the bus stop is relatively flat so I should just go under my own power.

I did cycle a moderately hilly 12 miles on my mountain bike tonight with front and rear panniers full of caving kit. 6 miles to the cave, hauled 95 buckets of digding spoil out and cycled 6 miles back. I am slowly getting cycling fit - but can't say I get masses of enjoyment cycling...a means to an end...

 

[guerney]

I bought mine from a friend many years ago for £100, kept it in my loft unused. Old Dahons can be had for around the £250 mark on ebay or Gumtree. I have to use a folder, easier for work travel. It still folds after conversion - the battery had to be mounted to the rack.






The video below shows a mid mounted battery. I considered converting a Dahon Jetstream, but the suspension looks expensive to replace (if replacement parts are actually available).

 

[guerney]

The reason for the folder is that I travel to Bristol quite frequently and it is a bit too far by bike, and few ebikes bikes will have the range for the round trip I expect.

How far is it to Bristol? Last time I checked my local bus companies, some wouldn't allow any folding bike other than bagged up Bromptons - the brand wasn't mentioned specifically, but the size constraints specified when folded and bagged, suggested such in their Ts&Cs.

When new, my 19.2ah battery yielded 43 miles at high assistance (less by now, after 3113km of use), more at lower assistance.

 

[Bogmonster666]

How far is it to Bristol? Last time I checked my local bus companies, some wouldn't allow any folding bike other than bagged up Bromptons - the brand wasn't mentioned specifically, but the size constraints specified when folded and bagged, suggested such in their Ts&Cs.

When new, my 19.2ah battery yielded 43 miles at high assistance (less by now, after 3113km of use), more at lower assistance.

I don't think FirstBus specify a max size for folding bikes but I will double check. I have seen somebody take on Raleigh folder to that is a typical 20 inch folder. The round trip to Bristol is about 44 miles. Its quite hilly as well as I live in the highest village on the Mendips so getting home always means a reasonable hill. I'm not a fair weather cyclist so cold and wind to deal with in the winter. My trips to Bristol are to see my son and go indoor bouldering usually on a week night so only there a couple of hours so no chance to recharge.

The 'local' bus stop however is only 3.6 miles away. Or, if I need to travel into work (Bath) then it's a different bus stop that's 5.3 miles away. There is a bus that comes through the village, twice a day, but only on Tuesdays, and going to Wells and not in the direction of Bristol or Bath - kind of useless in the extreme for me....I think the oldies take it into Wells for a cup of tea and gossip.

BM

 

[guerney]

With my level of fitness (low), my 19.2ah battery wouldn't give me 44 miles range over quite hilly terrain. If I had to make that journey by bike every day, and couldn't charge the battery at work, I'd of course opt for a larger capacity battery. I'd also buy higher capacity than needed for that journey, to future-proof against the diminishing capacity which results after many recharge cycles.