gregwee

I have a 2009 MU SL, and it's all still stock. However, I've been thinking of adding a 2nd chain ring in front to convert it to 18 speeds.. Anyone know if the MU SL frame will fit a double chain ring crank or is it too narrow? If it can be fitted, suggestions for cranks, derailleur, etc..

Another idea is to convert the rear hub to a multispeed (either 2 or 3) and get 18/27 gears that way.... However, I really like the minimal spokes on the rear wheel and would be loathe to loose that just to add more gears...

Any info greatly appreciated.

cplager

I believe (read: am guessing) that there is enough room to put on a front derailleur. I think you'll probably want a top swing (low mount) front derailleur. You'll likely (but not necessarily) need another bottom bracket.

If it were me, I'd definitely try.

gregwee

Thanks for the info... I'm assuming the new bottom bracket has to be longer so the crank sticks out more to accommodate the 2nd chain ring?

Since the frame doesn't have a mount point for the front derailleur, I'll need to buy an adapter for that as well..

HGR3inOK

For a front derailleur hanger, see: https://www.thorusa.com/accessories/special.htm

-HANK RYAN-
Norman, Oklahoma USA

gregwee

Thanks for the link..

cplager

Many front derailleurs attach directly to the downpost. You're probably best off getting one of these.

fietsbob

6x3 ? Sram Dual drive will do all that in the rear hub. triple crank is the 3 internal gears, instead.

just needs a 135 wide rear end.

or 9 x 2?

ThorUSA

you wont need a new bottom bracket, in case of alignment issues, the double adapter comes with a spacer you can use in order to move the right side outwards.
Internal gears are nice, but usually need a wider rear end, and they are heavy, which would somehow diminish the light Mu SL characteristics.
Front derrailleur clamps are usually not as large to fit the rather huge diameter Dahon or Tern seatpost tubes which is roughly 41 mm thick

Best Thor

pacificcyclist

I own a Dahon Mu SL 2007 model with the ThorUSA front derailleur adapter. And yes it works and yes it works really well. The internal hub option is way too heavy compared to Thor's adapter and it introduces inefficiencies. And since I want to go fast, as fast as those riding Madones and Cervelos, the IGH hub is simply too heavy and too much drag to keep up with the fast roadies and defeats the purpose of having a LIGHT road folding bike which the Mu SL is good for. You don't need a new bottom bracket or crankset. Existing bottom bracket and crankset work fine. You just have to remove the chain guard, move the big ring (I think it's a 53T or 55T) in place of the chain guard and then install a smaller ring. Since the crankset is 130BCD, the smallest you can install is a 39T and can give pretty good low gears for the fitness rider. If you are not a strong rider per se, I would advise going to a 50/34 compact crankset instead. See how you feel first.

Installing the adapter is pretty straightforward. Like Thor said; it just needs to be aligned with the supplied spacers to get it just right over the chain rings to shift properly. Also, you need to fashion a cable stop adapter under the bottom bracket to give anchorage to the cable housing of your front derailleur. Without it, you have nothing to leverage or pull the derailleur with since the Dahon Mu SL wasn't designed with a front derailler cable stop in mind. Either a Shimano 105 or Tiagra works fine. Tiagra is better if you want more of a 16T difference between the large chain ring and the small just in case, you want something like a 60T big ring and a 39T small. You can get by with the Shimano 105 only if you use an indexed thumb friction shifter. I got a $3 retro thumb shifter which looks really, well, retro and matches the SRAM click shifter on my right.

Other than that, you will get 18 speeds and it really expands your Mu SL to do enjoyable rides likewise you would struggle with only 9 speeds.

cplager

I'm assuming you're talking about this adapter (search for Dahon MU front).

(Thor may not be able to link to his own pages, but I believe we can link to a merchant's page if we wish.)

pacificcyclist

Yes for the Mu adapter.

gregwee

Thanks for the very detailed info. Looks like 18 speed with the front derailleur is the way to go for me. Also found the "Dahon MU front derailleur hanger" on Thor's special parts page.

Regarding changing the FSA crank to double chainring, the current 53T is fine, so I'll just add the 39T as the smaller chainring for lower gearing.

For the front derailleur, I assume I'll need a road derailleur versus a mountain bike derailleur due to the 53T/39T setup, unless anyone knows if an X9 front derailleur can handle 53T/39T? I would actually prefer pure index shifting if that's possible versus friction shifting, and if the X9 front derailleur works, then that will be the easiest solution as it matches the X9 system that's on the bike now. If that doesn't work, I can always install an SRAM Apex/Rival front derailleur, but have no idea if the X9 Front trigger shifter will work with the Apex/Rival derailleur?

To install the front derailleur in the Thorusa adapter, I assume I'll need to get a "Braze-on" front derailleur, correct?

Any info greatly appreciated.

pacificcyclist

Yes you need a braze on front. I have no idea on SRAM. I only use Shimano stuff. Sorry.

gregwee

No problem. Thanks for the info.

gregwee

After searching, found out that the X9 Front Derailleur can handle up to a 48T max, so it won't work with the FSA 53T/39T crank.. Looks like I'll definitely need to use a road front derailleur instead of an MTB one.

I'd still like to stick with an SRAM X9/X0 trigger shift, and so far, I've found the X0 Spec sheet where it states that the SRAM X0 shifter is compatible with SRAM and Shimano front derailleurs.. I'd definitely prefer confirmation before buying it though.

Has anyone installed SRAM X9/X0 trigger shift with an SRAM Apex/Rival/Force or a Shimano front derailleur and have it working without problems?

cplager

I use an SRAM X.9 (10 speed) front derailleur on my 9-speed Cruzigami Mantis where I have a 50/39/24 triple.

Front derailleurs are notoriously under-spec'd (meaning that they can handle more than the manufactures claim they can). I have very little doubt that a MTB derailleur will actually work just fine.

That being said, I see no issue going with a road front derailleur either and using a trigger shifter with it.

Long-story-short: You'll be fine going ahead with what you are planning and you'll probably be fine if you decide to try another option as well.

gregwee

Thanks for the info Charles. However, 50T is only 2 teeth more than the max spec... My 53T is 5 more than the max spec, so I don't think I'd take the risk with the X9 front derailleur.. I've had confirmation that the SRAM X9/X0 trigger shifts are 1:1, which is the same ratio as the SRAM road derailleurs and Shimano road front derailleurs. So, that's the way I'm probably going to go..

gregwee

I found a 39T FSA Chainring on ebay. Will this work with the FSA crank that came with the MU SL?

pacificcyclist

Yes, I have the same chain ring as this from FSA.

gregwee

Thanks. Just bought it.

jmm

Any idea why it's limited to 48T max? Since it's intended to be a braze on, and there are supposed to be industry standards for where those mounts are attached to the frame, might it only be limited with a standard fixed mount, and possibly not with Thor's mount, which can be "raised"?

Another possible limitation could be a too small radius on the lower edge of the cage, which might not necessarily be a show stopper.

Not an unequivocal endorsement, just food for thought from someone who has exceeded manufacturers recommendations in the past, and won, sometimes.

John

gregwee

No idea why there's a 48T max, but that's what it says in the SRAM X9 Front Derailleur Specs. It may not necessarily be a show stopper, but why bother to "tinker" and try to get it to work when I can buy a front road derailleur that is actually specified to work with 53T/39T without tinkering.

I'm in the process of buying all the necessary parts for the upgrade.

Bought the FSA 39T chainring on ebay, and a 2 speed X0 trigger shifter locally... Also, since I'm in Hong Kong and not the US, I will be picking up a Litepro Front Derailleur adapter for MU frame instead of Thor's as these are readily available here in the local shops. For the front derailleur, I've decided on a Shimano 105 braze-on, which should be compatible with the SRAM X0 trigger shift and can handle 53T/39T without problems.

cplager

Front derailleurs are tuned to the size of the rings they are going to shift. That being said, they work quite well on different size rings (people use regular road derailleurs to with 60+ tooth rings without issues.

You should have no issues using the 105 with SRAM trigger shifters.

dynaryder

I would guess because it's intended to work on a MTB/trekking/hybrid triple. Road doubles(53/39,50/34) don't have more than a 14-16t difference. A standard MTB triple 44/32/22 has a 22t spread,and hybrid triples are usually 48/38/28 or 48/36/26 for a 20-22t spread.

gregwee

Does anyone know the Bottom Bracket size for the MU SL? I've seen some pretty good deals for used cranks with bearings, and I may end up upgrading the Crank/Bottom Bracket bearings if it fits, which is why I need to know the size..