Ultralight

As a newbie looking to get back into biking after 25+ years away, and now considering folder, I appreciated all the instructive information I've received here. Looking from low end stuff all the way to high end bikes (yes, expensive) to educate myself.

Question - anyone fit a Sram XX1 system on a folder?

The entire group provides a 420% gear ratio, about 17-18% between each shift, and the entire group weighs under 1.6 kg. This group would include 11 cassette, derailleur, shifter/cable, bottom bracket, and crank including chainring.

Thanks,
UL

feijai

A big range is cool. But because folding bikes have small wheels and are often limited by the maximum size of the front chainring, the range often doesn't matter so much as the size of the minimum sprocket. For example, on my Tikit, I have the maximum possible front chainring (60T), and a rear cassette that goes down to 11T, and I could still use more top end.

What's interesting about the XX1 is that it has a minimum size of 10T, so you can eek out a bit more top end. But in the folding world there's already a common cassette which goes to 9T: the Shimano Capreo. And it's far cheaper than the XX1. Indeed for the cost of the XX1, or much less, there are many other wider options available, ranging from Schlumpf to the SRAM DualDrive to various internal gearhub systems.

osco53

I love my little stock folder and yes I ride In the top gear now and then, It's an 8 speed.

But If I want to go fast I take out my fast bike

Right tool for the job ya knows,,,,

And the cost of the XX1 ,,no thanks I just Upgraded the worn out system on my mountain bike with the Shimano Deore XT M8000 1x11 for less than half the cost of the XX1,,
Only thing the small cassette gear is an 11 tooth but still,,,,
I'm told by those who have ridden both this system shifts just as well as the now over priced XX1...

bhkyte

I have the 3x9 set up and the Sach 3x7 and a 3 x 8 for a future project.
I really like the dual drive set up. Gives you the 36ish upgear percent ideal for folders.
3 x 9 requires less double shifting.
The 11 would be great.
Some people don't like the extra complication, but you don't have a triple front.
Works with road race shifters which is great.

Ultralight

Thanks everyone for the replies. Very helpful. At this point all the suggestions are very helpful to expand my understanding. I had mentioned the SRAM as more of an upper hand solution for a 'deluxe' and 'weight weenie' approach - say if someone wants ot match a group to a titanium folder (i.e. swift) or titanium mini velo bike. The internal gear hubs and Schumlpf seem to have real advantages but with weight penalty. Rohloff is also $$$$.

I could not find weight to the Shimano XT 8000 group but appreciate the heads up. Definitely looks like a more reasonable set.

Thanks!
UL

Darth Lefty 

You could in theory customize the bottom of the Capreo cassette with a larger cassette and a Wolftooth bottom sprocket and make it 9x9-42 which would be pretty wild. The RD would probably drag on the ground.

fietsbob

No . thats MTB, big wheel stuff..

for ultimate foldability : Brompton .. Mine a 3 speed , 2 speed 150% reduction gear crank , Swiss Mountain drive .. 17~80 GI

I have the Rohloff Hub ... A Plus... No derailleur to bang out of adjustment , while Bike is folded..


Also, have a Bike Friday Pocket Llama travel bike .. The gearhub can be really low geared in small wheels ,
and high with double chainrings..

Or 2 speed Overdrive hub , same Swiss company , 1.6X [34, '54.4'] chain stays on 1 chainring ,
when engaged the cranks turn at a different rate than the chainring..

1, 16:53t is fine for me.. 526% range..

Nightdiver

If you really want that 10-42 without the XX1 price, there is the GX1 at a much lower price point.

invisiblehand

Indeed. Especially for 16" wheels. But depending on how high you want to go -- a NWT with 1.75" wide tires and 56-11 combination gets to ~95 gear inches -- which is higher than many XX1 29'er. There is a "value" SRAM 1x11 groupset now.

SRAM GX 1x11 transmission first ride review - BikeRadar USA

Although I should note that for any folder, one really doesn't want the SRAM crank and the cassette only fits on a wheel with the XD driver. Shopping around, I'm thinking that one could go under $500 excluding the rear wheel. Maybe $400 or less depending on the crank one decides to use.

I did a few calculations on whether the derailer would be too low to the ground with the 42-tooth cog on a 349 wheel in another thread: the chain pitch is 1/2", the 42 tooth cog circumference is ~21" and the radius ~21/(2*pi)". My take was that at the very least it would be close if not impossible. I'd have to take detailed measurements to determine whether striking the ground would be a serious issue.

I've never seen one on a small wheeled folder. I don't know enough about the XD 11 rear hubs to determine what's reasonable. A quick look usually pops up a bunch of 142 OLD hubs that are quite expensive. But the MTB folks can probably tell you what your 135 OLD options are to fit a great selection of bikes and whether there is a reasonably priced SRAM option rather than Hope, Chris King, and so on.

My take is that a single chainring setup makes the most sense on a commuter bike that you fold often. IME, you want it light and a single chainring usually makes folding easier. But on the most multi-mode commuter friendly bikes with 16" wheels, the big 42-tooth cog is an unknown.

Shimano Capreo will get you the tiny cog -- 9-tooth cog -- that makes a super wide drivetrain feasible: a 9-36 would get you that super wide range with derailer performance. In practical terms you might still have derailer strike issues. From memory, the first four cogs of a Capreo cassette are fixed and it's 9-speed unless you can find a custom 10-speed cassette. I personally would pass on looking for a 10-speed capreo cassette and stick with 9-32 with some bigger jumps.

Winfried

Alternatively, you could go for an Alfine 11 IGH, which weighs 1.7kg, and provides a 409% gear ratio without the issue of having a derailleur so low to the ground. Both Dahon and Tern have folders with that IGH.

Yet another alternative, is to get a six-speed Brompton, and replace its single chainring with a compact double chainring: According to Hub Gear Calculator, with a 50/34, gear development is 445% (99.7 / 22.4 * 100), which is pretty good for a super compact folder… provided you don't mind juggling with two speed shifters. I did that simple change, and am very happy with it.

bhkyte

Sorry I thought you were referring to an 11 speed version of dual drive. Sorry for my irrelevant post. No more than usual.........

smallwheeler

so, i guess that would be a 3 x 3.66666667 dual drive.

dynaryder

Big thing to keep in mind with XX1 with regards to folders(and mini velos);the rear derailleur is extra long cage. Dodgy to use with 20" wheels,and pretty much impossible with 16's. Also note that Capreo is 130mm spacing,9spd,and rim brake only. Either one of these systems requires using proprietary parts,so you're going to be limited in choices.

Honestly,on a small wheeled bike,I'd go with a short cage rear der and a double up front. Trek's Émonda has a 2x11 drivetrain,and the 56cm is 10lbs,so multiple chainring setups can still be made light.

bhkyte

Having just been to italy my Roman numeral skills should have been better.

However a 3.66666667 x 3 would give me 11.00000001 ish gears.........

seattlecycles

Hi, Ultralight,

The answer to your question is yes. We are Seattle Cycles and have just introduced a line of new folding bikes made of titanium. Our Burke 20 model with 20" (406) wheels uses SRAM XX1 with a 420% gear ratio (gear inches from ~ 23" to 100"). Weight is 8 kg and the bike rides beautifully. Please check out our website at Seattle Cycles for details. Or if anyone is visiting Interbike now please drop by our booth (10010) for a chat. We would love to show you the bikes.

Cheers,
Mike Yap & the Seattle Cycles team

Ultralight

Beautiful site.

Wow, 8kg - that is with saddle and pedals? And is the 8kg accurate? That would be 18lbs.

At least you do confirm that SRAM would provide a very lightweight package and is workable. 23-100" is a great range.

I did not see pricing. One of the challenge I suppose is the other titanium bike that is currently getting a lot of press and attention.

Thanks,
UL

invisiblehand

Cool stuff.