Winfried

Hello,

I'd like to replace the original single chainring on a folder with a compact double eg. 50/34. FWIW, it currently has a 7s derailleur in the back, and I measured 52mm between the center of the seat tube and the center of the chain.

What do you suggest to maximimze the chances of finding the right braze-on clamp (Litepro etc.) + derailleur (and two-speed shifter) so I don't order a bunch of parts that won't work?

Since we're not talking performance bike, entry-level parts are fine.

Thank you.

Tourist in MSN

Since your bottom bracket is not centered on your seat tube axis, a derailleur might not work if you tried to install a clamp that wraps around your seat tube. That is the reason that I did not put a double or triple on my Airnimal Joey. (Now, Joeys have an way to add that, but my frame is older.)

You might want to contact the manufacturer of the bike frame.

In my case I put a Sram Dual Drive rear hub on the bike to give me the wider gearing range I wanted. Those are now discontinued, but Sturmy Archer makes a similar hub.

It looks like there is a bolt on the back of your seat tube, if you are lucky there may be a way to mount a derailleur on that.

2_i 

For shifting, any 2- or 3-speed shifter will work. An item that you will likely need no matter what is the Sram slanted adjustment washer for braze-on derailleurs, needed to tune the angle of the derailleur. The obvious critical piece is the braze-on derailleur mount for folders. My only experience is in fitting one for Brompton. As a rule of thumb, these commercial adapters are of low quality. You can adapt one designed for a larger seat tube diameter with a shim, but generally not the other way around. Because of the variability in folders' geometries, it is hard to tell which adapter will work. You will likely need to go over more than one before settling. The obvious source for those adapters, and even slanted washers, is AliExpress, but they are a scam operation on the customer service side. If you find something similar on Amazon or Ebay, from personal experience better buy there as platforms yielding more security.

Winfried

I don't understand what that means. That the BB is more to the left or the right than the bike's center, and that somehow prevents installing a derailleur clamp on the seat tube?

I did. They're not interested.

I'd rather stick to a 100% derailleur solution since I bought that bike to get the best performance (for a folder, that is).

Good idea. It's for a small water bottle.

Nice to know. How is it used?

https://www.bike24.com/p2400555.html

Since they're cheap and sometimes offer free returns, I'll order several of them and give it a try.

What about the derailleur for a double compact? I read road derailleurs have a different geometry than MTB derailleurs.

If need be, can I replace the bottom bracket for one with a shorter/longer axle?

2_i 

You put it between the adapter and derailleur and, with this, rotate the derailleur by 4-5 degrees one way or another.

The free returns normally mean we keep the money, and you are free to return the product. Read the hundreds of reviews on Trustpilot and elsewhere that give more details.

I am not the right person to be asked about suitable front derailleurs as I largely lost the ability to see what people are struggling with - too much skill in matching awkward derailleur-chainring combinations. You can always start with what the manufacturers market as a set.

Regarding the BB axle, you may start with the original BB shifted to the right with spacers. The cassette spacers can be used on the BB, too.

Winfried

"Because of the steep seat tube, the derailleur was rotated too far forward, or too ‘clockwise’ when viewing the bike from the right side. To fix this, I tried a SRAM angled front derailleur shim. These can be used to ‘fix’ an odd seat tube angle; you sandwich one between your front derailleur and the braze-on mount." (source)

Tourist in MSN

I was unaware that shims existed for adjustments like that. That is why I said it would not work. But maybe with the right shim it would.

2_i 

There is this Gineyea adapter that has an adjustable angle. (Use a CC with good consumer protections if you buy on AliExpress - according to reviews, PayPal protections are worthless in the context.) Changing the angle, however, also changes the fore-aft position for the mounting point, so it is good to have the ability to change the angle independently. These slanted shims can be filed a bit to reduce the rotation angle. Finally, you can pile two washers at each other for a larger angle. In the latter case, you may need to use the rounded rim-brake bolt-washers on the outer side of the adapter.

Winfried

I was more concerned about 1) the distance between the clamp and the two chainrings (since it can't be modified), and 2) what derailleur could move sideways to reach both chainrings.

Duragrouch

EXACTLY what brand and model bike?

I have done EXACTLY what you want to do, 2X on a 20"/406 wheel folder.

The fact that the seat tube is completely behind the bottom bracket shell is not a problem; The seat tube is actually at a bit steeper angle to compensate for this, but not enough to cause derailleur cage angle problems, and the front derailleur adaptors adjust fore and aft to position the derailleur properly.

I find no clamp style front derailleurs to fit folding large diameter seat tubes. You must use an adaptor to mount a road "braze-on" style FD. I cannot speak for other brands, but Dahon 20" wheel folders, all used a 33.9mm diameter seatpost (very oversize), plus shim/bushing between it and the seat tube. STEEL frame Dahon seat tubes had a thinner wall thickness, than ALUMINUM frames, so different outside diameter of the seat tube, so use *two different adapters*, important, unless they now make one that fits both. I have the earlier Litepro adapter that I bought through a dealer who has retired. A newer style adapter is now sold, I have not used yet.

I use a Microshift 9 speed triple front derailleur for my 2X setup; I originally planned a 3X, but I could not get the FD to go in far enough for the inner ring. I kept it for the 50/34 double I used, glad I did, the big cage keeps the chain from dragging on the 34/11 combo. However, the upshift force on that FD is enormous, too heavy a spring, too much for gripshift, had to go to trigger, and it's still high. I'd like to fit a Shimano FD but it won't fit the adapter, as it has a double-shear linkage (more durable, but more space), this interferes with the adaptor. The Microshift cantilevered linkage is more compact. But even so, this FD has a very large inner top flange (lip) to the cage, preventing the cage from going far enough in, I had to grind a small part of that off to make it work, with zero problems in function or durability. If you use a square taper BB, you might space the crank out more, but do NOT try this on a hollowtech II design, as it reduces the clamp area for the left arm and it will come loose. Ask me how I know. I highly recommend the hollowtech II style in 50/34 with ISO External bearings, a common wrench pattern. I went 5x110mm BCD. I think the chainline rating is 43.5mm (from frame center to halfway between the 50 and 34 rings). This put it dead on center with my 7 speed rear cassette on 130mm OLD. When I had spaced the crank out 4mm (before the grinding as noted above), when on the low cog and downshifting from big to small ring, it would drop the chain. Now, installed as intended, not. I think your 52mm measurement is close to where my big ring is, but for a double, I think the chainline to between the two rings will need to be smaller than that number.

The original rear derailleur, Dahon compact short cage mounted forward of the axle, worked terrible, shifted backwards, and would not accommodate the 2X crank. No conventional rear derailleur mount on that frame. I used a Shimano Tourney TX with a mid (GS) length cage, with integral claw mount to fit under the rear axle nut. They are now $14, super deal, work great. If you have horizontal frame dropouts, fits great. If vertical dropouts, there is a protrusion on the back side of that claw mount that you need to grind off flush, for it to fit straight. If you want a different rear derailleur, you can just get a claw mount hanger and use any derailleur, but it will cost more.

50/34 11-30 on 20"/406-44 gives me 21-85 gear inches, like the lower 2/3 range of a touring bike or a Sturmey-Archer 3x9. Enough low to spin up hills, enough high to gently pedal down mild grades, I don't need higher.

big/big and small/small combos (I left more chain on than needed, to allow going from 30 low cog to 34 later):

Fentuz

I think you will need the "less pretty" type of bracket as they give more setup flexibility

or that


for the derailleur, it is up to your shifter but, sora, claris are good starter. You will most likely need a need crankset and the the inner Rin will be where your current on is, may be a little closer to the frame. If you stick with a litepro crankset or generic FSA or claris, you will be fine and it is just the case of adjusting things to align properly.

Duragrouch

The above is the only style of adaptor I have seen of late. Litepro's earlier design they stopped making, but can provide for a minimum quantity order, like 100, last I checked. I think this newer design may allow the derailleur cage to go inboard more, though it looks like it may not be as strong (the upper projection may be less rigid than the older design), but it seems to be selling well so it's probably fine. I did not see different size models so my bet is it's set up for the larger diameter aluminum frame seat tube, with a shim for steel or it just flexes to accommodate it.

Regarding "adjusting things to align properly" on the crank, uh, my experience says caution; Like I said in my post, I tried that with a hollowtech II style, 4mm spacer on the drive side, reduced left arm clamping length by same (about 30% if I recall), I thought that was doable, but the left arm came loose. You need the full design length of clamp around the spline there. I altered the derailleur to correct that, everything worked, and chainline was perfect.

2_i 

The problem with the mounts you point out is that the finger on which the derailleur mounts is secured with just one bolt. Some protrusion prevents rotation, but it is quickly sheared off in use, and the finger is largely free to rotate. In addition, the first mount is pointlessly bulky under the finger, and its buildup interferes with the derailleur cage. The mounts that grab the seatpost near or above the derailleur mounting point work better, but the details depend on the particular setup. This includes things working tentatively on a bike that is not particularly challenged in use.

OK, you can always file off the stops on the derailleur to get extra reach. Another tool, when using an adapter band with a larger diameter than the seatpost, is an asymmetric shim around the seatpost that pulls the adapter in our pushes out. Finally, you can use a triple derailleur. These have a wider swing but bring a bulkier cage. My remedy for everything are the higher-end Suntour triple derailleurs you have to fish for on Ebay, such as XC Pro. These derailleurs are very capable shifting, but have compact cages in the lateral direction.

Winfried

Thanks for the tip.

A 50/34 compact fits and the 7s derailleur works with the 34T ring — on a stand at least.

The seat tube is 41mm wide, and the distance between the right side of it and the 50T ring is 41mm.

Turns out I had a Litepro B clamp lying around. I'll just order a cheap road front derailleur and give it a shot.

Incidently, the four Litepro clamps can still be found on AliE: B, K, P, SP8.

2_i 

By all means, you are sure to learn when you try something in practice. The geometries of the folders vary, and just a few mm one way or another may be enough to eliminate or create a problem.

Duragrouch

The P-frame adapter is what used to be sold by a longtime dealer as used for the Dahon aluminum frames (matches it saying for Mu frames, and also Mariner, et al).

On my steel frame, I have what looks like the K series for steel frames (matches it saying for Speed 8).

Both of the above had the outer finger, resting in a channel on the ring, so it could adjust fore/aft. However, that feature adds thickness to the assembly, obstructing how far the FD cage can go inboard. I just barely made it on my Dahon Speed, by grinding off a small portion of the cage top lip. I was hoping that the less-strong looking adapters, might prevent the need for that, but I was wondering if just as strong as the previous design, and perhaps not.

That Shimano 10 speed FD will NOT fit my adaptor, and perhaps the other Litepro adaptors as well. As I mentioned, the Shimano has a double-shear linkage that prevents a correct mounting. I have one of those derailleurs; Why? Because it has a longer arm (so more cable leverage) than other Shimano FDs, so needs a longer cable pull, LBS says "fits only shimano 10", AND has a softer spring. As I said, my Microshift FD is a bear to shift, impossible with gripshift. If I can find an adaptor that works with the Shimano 10, I want to try installing a triple gripshift and then try to shift my double crank by going from 1 to 3 on the shifter. This may work if the FD long pull is exactly 2:1 versus short pull, but I don't know the exact ratio. But that would drastically lower shifting effort by trading displacement for force. The LBS mechanic, quite experienced, does not know if this scheme will work, but smiled and said it's a good idea to try. He said that 10 FD has a shorter cage than the triple I use, but should work for a 50/34 double. I like the long cage on my triple FD, only adds a tiny bit of weight and has no chain drag when on the small/small combo.

Fentuz

Well, I did not have any issues you mentioned. The braze-on post never rotated and when properly set (located and clamped), it did not interfere with the derailleur. Only issue I had was the lack of thread lock which is easily fixed.

yes direct mounts are better but folding bikes frames don t allow this hence folding bike bracket are offset like the bottom bracket so that the derailleur is "co-centric" with the bottom bracket.

2_i 

Great! Below is the photo of the mounts that I mounted and rode with at some stage, but that came off due to the problems that developed. Many more in storage never went on because they were spare duplicates or something. From smaller problems, the curvature of the well for the derailleur is much different from typical derailleur's curvature, the stop for the cable is not optimally located in relation to the mounting point - to get there you have those fingers going up or down, tiny screws grabbing very small thickness of alu.

Winfried

I ordered a "Shimano Sora FD-R3000 2x9-speed Front Derailleur Brazed-On" (it's "dual pull", not just bottom pull), and a "Shimano Touney TZ SL-TZ500 3-speed Thumb Shifter left". We'll see if the Sora fits the Litepro B clamp and the 50/34 dual compact I had handy.

Provided you do need a 10s-compatible derailleur, you could try different shifters, such as Sunrace's M90 friction shifter left

It's turning into a museum :-p

Turns out AliExpress' "free return" option only applies to one item if the order included multiple items to save on shipping. So, to be able to return each item and get a refund in case it didn't fit, make sure you ordre each item separately.

Duragrouch

Good to know, thanks. My thoughts were specifically to "non-compatible", i.e., using a 3X gripshift 1-3 on a 2X, to get lower upshift force. However, a) that 10 speed FD, with softer spring AND longer lever arm, may be enough, and b) gripshifts have a poor leverage ratio, the cable barrel is just under the surface, so that M90 with a better leverage ratio, may be enough. With the current Microshift FD with overly strong spring and shorter arm, I had to go to a Shimano trigger shifter, and I still need to upshift by using my right thumb to push the (left) lever inline with my thumb, whereas using left thumb in an arc is too much force for my hand.

Duragrouch

Thanks for the info. Hmm, I guess it was a poor assumption of me to think, well they are selling well, they must have tested the design. Sounds like not. The ones with the post held by only the one screw from underneath, looked weak to my eyeball. My earlier design Litepro, stronger design, is working well going on 3 years and a lot of shifts. But it does require grinding off the forward-most part of the FD cage inboard lip, for sufficient clearance, and thats for just a 2X, would be impossible for a 3X, with the small ring even more inboard. I hope the earlier design Litepros (top right in pick above) will be available going forward. However it doesn't fit Shimano FDs, that's a problem.

Fentuz

hang on, as you said, you are /have been a mechanical engineer so surely you know about 1st rule of 6 sigma: "rather your Data". here, we have 1 users having issues with several designs. It is not a representative sampling. I have used successfully 3 of these brackets (1 litepro and 2 of the cheap big squary ugly version) and I did not have any issues with the brackets themselves.
Note that there are many successfull example on the forum and the internet - here is my favorite which I used as inspiration when I build my helios X18TT now x10.

As I said, I did not get any issues with the bracket however, I did noticed twice derailleur pulling but, it had nothing to do with the brackets.
The shifting cable routing on folding bike is not great to bends. Add to that wear and tear and fiction due to poor English weather and lets face it, servicing neglect as commuting bike and the added load and stiffness caused extra load on the bracket. Cleaning and lubrification freed up the shifting system and everything went back to normal.

When commuting all year around in the wet, frost etc., I found that the brake and shifting cable needed an overall once a year. a jagwire kit is ~£10 and it takes 1hr to do the swap at most and as i said, never had a problem but equally, my isolated experience is not a representative sample.

2_i 

Wow! One photo below shows 2 practically new mounts where the tabs preventing the fingers from rotation, at the contact of the finger with the band, begin to shear off. The next photo shows how a derailleur fits into the well on a Litepro mount. Both photos illustrate well what kind of products one deals with.




As to these mounts selling well? I have 9+ of them.

Fentuz

Again, I have used the same things and did not have a problem. so my point remain valid, it may not work for you but it did for me as it did for many others. if they were that bad, people would moan about it and ask for solutions.
yes, the 2nd mount does not look great but i must say i don't think your derailleur would fit properly on my gravel bike braze on mount of my road bike are the boss looks really shallow.

Again, I do not deny you had many issues but I cannot find many bad reports; even on this forum there are several users of those mounts and yet, you seem to be the one with issues. It may be that people just get on with it and modify them to fit without saying anything.

Winfried

I've been using the old K clamp for years on a Brompton with no problem.

https://www.aliexpress.com/i/1974235466.html