Retro-fitting a braze-on front mech to a folder

[horizon]

So here's the update (I'm putting this up here for anyone thinking of doing the same to any folding bike where they want the extra gears.)

Well it all worked and superbly! The final spec was as follows:

Double chainset from Spa with 26/42 chainwheels (you may want a standard 52/34)
BB to suit
Litepro braze-on adaptor (this is the key bit)
Shimano FD-R440 double front deraileur (works with MTB shifters)
Long length of gear cable! (allows for the fold)
Long length of cable housing (there is no exposed cable)
Shimano Tourney left hand shifter: this is a (very) cheap friction shifter and there are better around!

There were really no major problems with the installation. At the heart of it is the Literpro adaptor that puts the "braze-on" in exactly the right place for the front mech on a Dahon or Tern folder. The trick is to get the right adaptor for your bike. Everything else just follows as per normal.

If there is an issue, it is that there isn't an obvious routing path for the cable. It runs under the BB of course but ths space is occupied already by the hole for the seatpost: this means that you cannot use a standard BB cable guide*. However, I've bodged mine with zip ties and tape and it works absolutely fine - you might have to choose your own best way.

* You might get one to fit but you still have to get the cable past the setapost hole.

What it has done is transformed a practical but limited folder from a "home to station" bike to one that has the world at its feet. The cost is around £100 depending on quality of parts and very little work. The biggest problem I had was really finding the best way forward - I posted this originally over a year ago but it should be just a week to order the parts and an evening to install it.

[Winders]

Does your Tern Link D8 use the small Neos derailleur or was it already set up with something more standard? I was put off the double chainset approach on our one as it had the Neos derailleur and I wasn't sure how much capacity it had for the extra chain length.

[horizon]

My own Tern Link D8 has a SRAM 9-speed derailleur fitted by the previous owner. I think (but I am not certain) that this involves a conversion part). It would originally have had (I presume) the Neos. The Tern Link D16 had a Claris groupset as does my Tern Node 16. My Node also has extra braze-ons on the seat tube to allow for a bottom pull front mech as well as the braze-on for the mech itself. This also resolves the cable routing problem that I alluded to above. I presume that the Claris would have added to the cost of the D16 (both Link and Node). While I don't know of course whether the Neos works with a double, I do know that Tern made it work (and so have I) with Claris/SRAM.

https://www.ternbicycles.com/uk/bikes/473/link-d16

[UpWrong]

Glad to hear it works. I think the Shimano FD R440 is a Road derailleur, hence the R designation. Road FD doubles will work with MTB trigger shifters.

[Cyclothesist]

Some real life experience of going down this route ....I too have a Tern Link D8 (2020 model) with a claris rear derailleur on an 12-32 cassette. I bought the litepro FD adapter and reusing a vero compact road crank, 110mm jis bb and a road double front derailleur and set about transforming my folder to a 16 speed set up with some serious climbing gears. I discovered it's next to impossible to eliminate chain rub in the FD in about 3 of the selected gears because of the short chainstays on the folder. That means the chain sweeps a bigger angle at the front derailleur than on a longer chainstay bike and impinges on the derailleur guide plates. I've reverted back to the original chainset while I have a rethink. I suspect that's why there are several Link D8 internet articles describing successful conversion to 9 speed with an 12-36 block using a shimano zee rear derailleur but few going to 2x at the front. I'm wondering if the claris rd can be coaxed to shift an 8 speed 11-36, I'm pretty sure it'll do an 12-34. I can see why Tern aren't doing 2x models of their current folders.

[2_i]

Folder cable woes can be largely solved by getting bamboo-type housing. In my own experience, the housing by TRLREQ, such as here on AliExpress https://www.aliexpress.us/item/2251832853241651.html, has been a good price-quality compromise. Their lining is low quality, so I get one from Jagwire. You do not need any ferrules or other special endings on cable ends. I just spread out the lining to a mushroom with a heat gun. That housing works with shift and brake cables and is in practice indefinitely reusable. The gain is that you can have long, awkward routing with abrupt turns, and the shifting stays relatively smooth.

[Winders]

I suspect that's why there are several Link D8 internet articles describing successful conversion to 9 speed with an 12-36 block using a shimano zee rear derailleur but few going to 2x at the front.

Lightweights! Our Tern Link D8s are now both 9 speeds, one with a 11-42T block and the other with a 11-46T block. Reading your experience, I’m glad I didn’t go down the 2x route in the end when searching for more hill climbing abilities. Whatever method you use, once you get a twenty-something inch bottom gear out of a folding bike it swiftly becomes a much more useful machine in any place remotely hilly.

[drossall]

2*9 came as standard on my Tern Verge X18 and works really well, with an excellent range of gears - 28-109".

[Cyclothesist]

That x18 is a lovely looking bike.
There's a growing niggle that I should be able to get 2x to work. The Link D8 frame is pretty much unchanged from the D16 except for the FD braze on and cable pulley mounts. I'm awaiting delivery of an FD 2000 and will report back on the next experiment. Wish me luck!

[Cyclothesist]

TL;DR FD 2000 didn't work out
The FD 2000 is an 8 speed front derailleur with a couple of unhelpful (for this use) peculiarities...
1. It has a wide bottom pivot link that catches on the arm of the litepro adapter limiting the FD inswing. I had fun making a curved shim to pack out the FD2000 so that it cleared the adapter.
2. It has a long cable attachment lever - so long that it impinges on the low chainstays on the Tern Link D8 on shifting to the larger chainring (50t) even with the FD as low as it could go above the large ring teeth. That one's a bit of a show stopper.
In the small chainring (34t) there was chain rub on the FD inner plates in the bottom 2 gears that couldn't be eliminated. (The derailleur at its absolute minimum and the low stop backed right out).
I kept the front chainline at 45mm as measured on the original D8 crankset. (Experiments with a shorter and a longer BB showed that didn't help)

So what have I learned?
1. It's an attractive idea but harder than I thought to retrofit 2x to a Tern Link 1x folder.
2. The Link D16 FD braze on mount is likely inboard of where the litepro adapter positions the front derailleur if there's no chain rub in the lower gears.
3. I'm not devoting any more time to the 2x conversion, but will look at a lower geared cassette when I need to replace the current one.

[Brucey]

any photos?

[Cyclothesist]

any photos?

Good point! I didn't take any at the time and I've put the original crankset back on again. I can take some tomorrow of the adapter and FD2000 to show the impinging problem if that helps?

[Cyclothesist]

I suspect that's why there are several Link D8 internet articles describing successful conversion to 9 speed with an 12-36 block using a shimano zee rear derailleur but few going to 2x at the front.

Lightweights! Our Tern Link D8s are now both 9 speeds, one with a 11-42T block and the other with a 11-46T block. Reading your experience, I’m glad I didn’t go down the 2x route in the end when searching for more hill climbing abilities. Whatever method you use, once you get a twenty-something inch bottom gear out of a folding bike it swiftly becomes a much more useful machine in any place remotely hilly.

Winders that sounds great! What rear derailleur are you using please?

[Winders]

Microshift Advent medium-length derailleurs in both cases. One runs a 11-42T cassette with a rapidfire style shifter and 44T chainring, the other a 11-46T cassette with a bar end shifter and 52T chainring. Ground clearance on road or gentle gravel surfaces is adequate.

For rougher surfaces or grass the super-short option which maxes out on a 11-38T cassette would be ample as it’s designed for kids’ MTBs. I am keeping an eye out for version 2 of the Advent X derailleur which appears to have more clearance than their earlier medium derailleurs - although it’s 10 speed it is compatible with Advent shifters when using a 9 speed cassette according to Microshift.

[Cyclothesist]

any photos?

Here are some photos showing the problem with the Claris FD2000 wide pivot hinge impinging on the adapter arm. The hinge is approx 3cm wide compared to 2.5cm on the 5700 105 for comparison. The (bodged but functional) curved shim sorted that by moving the derailleur back. You can also see the long cable lever compared to the 105. The new Claris FD2000 lever is like that of Tiagra 4700. It's never going to fit under the Link D8 seatstay.
I suspect an old style Claris FD24000 would not hit the seatstay with its shorter lever but I'd still have that annoying chain-rub in 3 gears.
I have tried the set up with the FD5700 and that rubbbed too only worse.