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  1. #1
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    Fixed Gear Moonlander

    I am new to the world of mountain biking (I normally ride mountain unicycles) but am building up a Surly Moonlander. I ride a Surly unicycle with a 100mm rim and a Surly Nate tire.
    I want to build the Moonlander with a fixed gear as it will be closer to what I am used to (there is no coasting on a uni). I bought a frame with an offset fork with the thought that I could have the option to have a fixed gear bike and flip the wheels if I really needed to change the ratios. For instance, I could gear it for normal riding and commuting and then have the front wheel with a granny gear for snow or sand or whatever.
    As I am new to bikes with so many components I am at a loss as to exactly what I need. I believe a Surly MWOD crankset will still be need for the Moonlander but if I understand it right I don't need a front or a rear derailer? The chain just goes wraps straight around both cogs. Is this correct?
    Also what hubs should I use? I was thinking of getting a Surly Dingle cog for normal use. What should I get for the front to make a granny gear when it is switched out? Or do I need a different gear for the front?
    Again I have never ventured into bike building before and I don't have a reliable LBS to ask these questions to.

    Thanks for your time in answering these questions.

  2. #2
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    First off, sounds like a fun project and best of luck with it!

    The Moonlander offset primarily serves derailleur gears. If I've understood correctly, you could fit Clown Shoe rims with BFL tires to the front and rear of a Pugsley as well, but the limitation of that frame is using the large gears of the cassette. It's not a huge deal - you have 14 mm more Q-factor than you'd have with a Pugsley. With the Pugs you'd have a wider choice of cranks. Mr. Whirlies are not the best when it comes to price/quality-ratio. If you haven't touched the frame, I'd consider using a Pugsley frame instead. I'm sure you'll find a definite answer as to whether the rims and tires of your choice will fit. (Clown Shoes and Nates should fit.)

    You don't have to use the MWOD crankset, because that thing is also designed specifically to facilitate using a wide range of gears on a cassette and allow a small (granny gear) ring where regular cranks have their middle gear. The smallest middle gear on normal cranks is something like 31-32 teeth. On a singlespeed or fixed machine I feel that a granny gear is unnecessary - with a 32/22 you'll already be climbing trees. My singlespeed Moonlander is currently geared 26/15 for all-around use, which is about the same as 33/19. The latter would be better for chain wear. (I only have 26t in the front because at times I run a 1x9 setup and 26 is the best chainring size for me in that use.)

    You're right about derailleurs: you don't need them at the front or rear. The chain wraps straight around the chainring and cog.

    I've done some fixed mountainbike riding and it's really fun. With fat bikes the Q-factor changes things. Compared to your unicycle, the BB is closer to the ground and it's in between wheels instead of the center of one. When you steer, the front wheel follows one path and the rear has its own. For this reason I've found coasting to be very handy with the fat bike in tight situations.

    There are a number of ways to have choice when it comes to gearing. One is simply having two cogs in the rear. The downside is that the chainline will not be straight for one (or either) of them and you only have three teeth of range. Another is a "dinglespeed", where you have two cogs and two chainrings. One slower and one faster combo. For example if you have 32/20 for slow stuff and 34/18 for commuting, the chain length remains the same and you can get a straight chainline on both gears. If you couple the dinglespeed with other cog options on the front tire, you get two more gears. The front wheel cogs should be within three teeth of their rear wheel counterparts, so you can still use the same chain and the adjustment range of the fork ends in the rear doesn't run out.

    If you're sure about sticking to fixed or singlespeed use, you could use 135 mm SS Disc rear hubs for both wheels. If you want the option to run cassettes, build the wheels with Shimano hubs and lock it fixed with the Surly Fixxer. A cassette hub is better for the Moonlander offset and Clown Shoes, because the spokes form an even triangle, which result in an even tension on either side.

  3. #3
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    Here's a quick shot of my Moonlander drivetrain:



    In the rear you see lots of space for the cassette - now occupied by spacers and a single cog.

    The chainline is more outboard than necessary, as you can see from the huge amount of space between the chain and tire. With less offset in the rear and narrower cranks, the chain would still clear the rear tire with ease. This is why I think that for dedicated SS/fixed riding the Pugsley is a better choice even if you want big tires and wide rims.

  4. #4
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    Saul Lumikko,

    Thanks for the information. It is very thorough and had given me a lot to think about. I was going through some website this morning and discovered the Surly Ultra NEW fixed hub.
    As I said before I am very new to bikes, but it seems like it might be a good idea to build one wheel with this or this type of hub for fixed gear fun, and then build the other wheel with a hub that could take a cassette. This way I could swap the wheels hopefully without too much effort and have a lot of versatility.
    My main goal now is to fix up a bike that is fixed gear but having the option of a cassette in the future might be a good idea.
    Any thoughts?

  5. #5
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    One thing to keep in mind is that the offset fork will be the same offset as a pugs but less than a moonlander. I don't believe there is a fork option with the same offset as a moonie. If there is I don't know about it.

  6. #6
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    Quote Originally Posted by evilcat View Post
    One thing to keep in mind is that the offset fork will be the same offset as a pugs but less than a moonlander. I don't believe there is a fork option with the same offset as a moonie. If there is I don't know about it.
    Surly sold a 28mm offset forked ML for a while you could swap wheels....just 2013 I think...

    Moonlander fork confusion?
    Safe riding,

    Vik
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  7. #7
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    Quote Originally Posted by Harry D Collier IV View Post
    Also what hubs should I use? I was thinking of getting a Surly Dingle cog for normal use. What should I get for the front to make a granny gear when it is switched out? Or do I need a different gear for the front?
    Again I have never ventured into bike building before and I don't have a reliable LBS to ask these questions to.

    Thanks for your time in answering these questions.
    If you are 100% committed to riding a FG fatty you don't need to think about derailleurs, but when you start to hit really soft conditions you'll need a low gear that's fairly useless on hardpack surfaces. You may also want to carry gear on your fatty and use it in a way you don't currently use your uni.

    So just a thought....if you have a swappable ML...why not build 1 FG wheel and one cassette wheel? Then you can run: FG, SS or install gears without the hassle and cost of a wheel rebuild. There is no downside to running the cassette wheel up front and the FG wheel as the drive wheel.

    With external cable routing you could swap in a 1 x 8/9/10 setup in 15 mins and use it for a specific ride while quickly going back to the simplicity of FG for most of your missions.
    Safe riding,

    Vik
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  8. #8
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    I ordered a Moonlander frame and the website said they would swap out the forks to give me the moonlander offset fork for free. It is now an option to buy these separate I think. The frame is the new sand color and the fork is the space black but I am having them both powdercoated so they will match.
    Vik,
    I like the idea of 1 FG wheel and 1 wheel with a cassette. I will probably use the FG one predominantly but if I go on a long trip I can switch them up without too much difficulty.
    Thanks for the advice everyone.

  9. #9
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    Name:  100_0003.JPG
Views: 874
Size:  66.5 KBThat was my FG before the tire. And with the tire,Name:  100_0212.JPG
Views: 837
Size:  112.6 KB Not much room, but it works.

  10. #10
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    I like Surly's Singleater chain tensioner. It means the chain doesn't have to be perfectly tight. An extra link here or there doesn't matter, and that gives you some extra flexibility. Plus, with a tight chain if you get clothing stuck in the chainring it will mangle it, but a chain tensioner allows it to pass through easily (and maybe your finger too). This chain slack would also make it easier to run the two front chainrings / 2 rear cogs, manual transmission option mentioned above.

  11. #11
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    Fixed Gear Fatty - lot's of fun!

    Check out 63xc.com--The Offroad Fixed Gear Site for basic MtFx info. The names comes from 63 gear inches - their estimation of best gear ratio for offroad.

    From Sheldon Brown :
    Gear Inches
    One of the three comprehensive systems for numbering the gear values for bicycle gears. It is the equivalent diameter of the drive wheel on a high-wheel bicycle. When chain-drive "safety" bikes came in, the same system was used, multiplying the drive wheel diameter by the sprocket ratio. It is very easy to calculate: the diameter of the drive wheel, times the size of the front sprocket divided by the size of the rear sprocket. This gives a convenient two- or three-digit number. The lowest gear on most mountain bikes is around 22-26 inches. The highest gear on road racing bikes is usually around 108-110 inches. Unfortunately, the handwriting is on the wall for all inch-based measurement systems.

    I note that this gives you the equivalent wheel diameter for 1:1, or unicycle/no gears. Can you envision riding a 63" diameter Uni? I settled down to a 49" gear on my Karate Monkey (29x2" tires).

    And here's Sheldon's full Fixie article list Sheldon Brown /fixed/

    But what I'm running now is:
    Fixed Gear Moonlander-img_2155s.jpg

    Moonlander with 3spd fixed gear hub (Sturmey Archer S3X) and DingleSpeed cogs, currently 36x16/39x13:

    Offroad, I stay in the 36x16, with 41"/49"/65" gears. 39x13 was intended for getting to the trail, but I don't use it much.
    Fixed Gear Moonlander-img_2618s.jpg


    Note that 36+16=52=39+13. The secret of DingleSpeed is the same number of teeth in either gear so the chain length needed is the same. You can tolerate a 1-2 tooth variation, but you have to stay within your chain adjustment range - with a little for chain wear. I tried this, and swapping is a pain especially if you run a chaintug. Even the optimal same #teeth plan requires a little chain adjustment to swap, but 1/2 turn vs many turns of the adjuster.

    A note on fixed gear - chain tension during operations will munch any tensioner anyone ever tried. No derailers or etc.

    Also, you will need a straight chainline (cog and ring lined up) or you WILL derail the chain. This speaks also to the cog and ring you choose - if they are ramped/shaped for a derailer gearset, your chain WILL derail, and usually just as you're starting down a bumpy descent (have we talked about brakes yet?). And a derailment on a fixie is not just "no drive" - if you don't have a brake or two on the bike it's "no stop". Or worse yet, the chain binds (no freewheel - all parts keep moving) and locks up/destroys things. I have a small bit of chain saved that is bent at 90degrees - sideways. Singlespeed rated stuff with full teeth is what you want.

    Ok, so to get that lovely chainline matched up for both cog/ring combos - Surly's Dingle Cog matches the chainring spacing of a crankset, and using it with a Surly Fixed hub (get the disc version if you want to have a rear brake - or a front brake!) lines it up with mid/hi position on the cranks. On a Moonlander, with the 28mm offset, the only cranks that will line up are the MWOD and the OD. I'm running a MrWhirly, with the Moonie width spindle - but with a standard spider running rings at mid&high (both sides of the outer tabs):

    rather than the MWOD mid-bolts-to-low arrangement.

    Clear as mud? Feel free to ask specific Q's?

    Oh yeah, and here's my Muni (that I can barely ride)
    This isn't a "you're doing it wrong" topic.

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  12. #12
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    Quote Originally Posted by Mark_BC View Post
    I like Surly's Singleater chain tensioner. It means the chain doesn't have to be perfectly tight. An extra link here or there doesn't matter, and that gives you some extra flexibility.
    You can run a tensioner with a single speed setup, but not a fixed gear drivetrain as Wade points out.

    A SS or FG chain does not need to be uber tight....you are better off running it on the looser side than on the tighter side.

    With the ML's horizontal dropouts there is no reason to mess with a tensioner even for a SS drivetrain.
    Safe riding,

    Vik
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  13. #13
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    Well, looks like the drivetrain pic doesn't want to load, so:



    The S3X uses splined cogs (single speed for cassette). Those are Surly cogs with the wide bases, wide parts facing each other for max separation.

    Also note - no rear brake. Front by itself is acceptable, but I would run a rear brake if I could.
    This isn't a "you're doing it wrong" topic.

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  14. #14
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    Quote Originally Posted by Harry D Collier IV View Post
    I ordered a Moonlander frame and the website said they would swap out the forks to give me the moonlander offset fork for free. It is now an option to buy these separate I think. The frame is the new sand color and the fork is the space black but I am having them both powdercoated so they will match.
    Vik,
    I like the idea of 1 FG wheel and 1 wheel with a cassette. I will probably use the FG one predominantly but if I go on a long trip I can switch them up without too much difficulty.
    Thanks for the advice everyone.
    Just be aware that will need a bunch more chain to run that cassette. The tensioner on the derailer takes about 20 more links.



    You can use 2 master links in the chain to give you that difference, or have 2 chains with 1 master link each so you can just swap chains. Most folks who run cassette/single wheelsets plan on the single as a limp-home option requiring you to break and shorten the chain - I think. Anyone knows better, speak up.
    This isn't a "you're doing it wrong" topic.

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  15. #15
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    That is a nice looking muni. What size are the cranks? They look very long.
    So if I understand correctly the outer chainring on the MWOD + the outer cog on the dingle should = the inner chainring + the inner cog.
    The MWOD chainring sets look to have a huge difference in size between the two gears. Something like 20/33 or 22/36. Stupid question but is it possible to make a MWOD that is 33/36 and what kind of difference would this make between the two? Big enough to notice?
    If I made a 33/36 and then a 17/20 dingle everything should match up correct?

  16. #16
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    Probably a dumb question but what's the advantage of fixed gear over single speed? I would think that you wouldn't want the cranks to push you. I know for trials and stuff it would useful but for mountain biking?

    I always shudder when I see the FG couriers whipping through traffic downtown without any brakes. What if they need to stop on a dime?

  17. #17
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    Coming from the world of unicycling I feel more at home that way. I tried to put a geared hub in my uni and it just wasn't the same. I would still have a brake on my bike, even if it was just a drag brake for downhill.
    As a kid in the early 80's all I knew was fixed gear bikes. You couldn't coast but you could go backwards.

  18. #18
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    Forget couriers, this is mountain biking. The control you have with a FG-VS-FW is near perfect.

  19. #19
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    Quote Originally Posted by Harry D Collier IV View Post
    That is a nice looking muni. What size are the cranks? They look very long.
    So if I understand correctly the outer chainring on the MWOD + the outer cog on the dingle should = the inner chainring + the inner cog.
    The MWOD chainring sets look to have a huge difference in size between the two gears. Something like 20/33 or 22/36. Stupid question but is it possible to make a MWOD that is 33/36 and what kind of difference would this make between the two? Big enough to notice?
    If I made a 33/36 and then a 17/20 dingle everything should match up correct?
    Thanks. The cranks are 175's - because I came to Muni via MTB! That's my usual crank length, and I interpreted Muni in terms of needing "low gears" - which meant more leverage vs the ground to me. Either a smaller wheel or longer cranks. Fat wheel was what I wanted, so cranks are the only other factor.

    Another Sheldon Brown Link - Gain Ratio This comparison system takes in cranks, gear ratio, and tire radius. For a Uni, it's just tire/cranks. My 29" tire/175mm cranks is 368.5/175 = 2.1 The Moonie, with the 36/16 and S3X has 3.0, 3.6, 4.7 I find that climbing/standing works best in the 3.6 - in 3.0 it's more like standing/spinning, needs more resistance to use the available power. But when doing techy stuff, the lower the better. Once I get good enough to really go ride mtb trails, I may need shorter cranks - but I need to get my skills up.

    You've hit on the reason I went away from the MWOD ringset and got a spider. MWOD starts with the granny - 20, 21, 22, 24, or 26t are available but the bought sets are 20/33t and 22/36t only. The outers are available in 33 and 36t only. Dingle cogs are 17/19, 17/20 and 17/21 - 2-4t difference. Closest MWOD combo is 26/33, 7t difference. Plus, the ratios kinda suck.

    Once you go to a spider, you have more and better options.
    Surly SS chainrings are available in
    94mm BCD x 30t, 31t, 32t, 33t, 34t, 35t and 36t
    104mm BCD x 32t, 33t, 34t, 35t and 36t
    110mm BCD x 34t, 35t, 36t, 38t, 39t, 40t, 42t, 44t, 46t, 47t, 48t, 49t and 50t
    130mm BCD don't matter - no MW spider for this size.

    For the Moonie, I did find max ring sizes of 37t mid and 41t high. Bigger than that they hit the wide chainstay. But a 37/41 + 17/21 setup would fit - if you like the ratios. I really like the 3.6 gain ratio (49 gear inches with 175 cranks) for general offroad. That would match the 21t with a 36t, and put a 40t with the 17t for a 5.0 gain (68 gear inch with 175's). That puts you in the 110BCD list, right where I am. Gives you more options, but you can only move up by one tooth - and those are hard to find rings (37t, 41t).

    Here's a great view of the MWOD system:
    MWOD_Chainring_Instructions_-_02.pdf
    This isn't a "you're doing it wrong" topic.

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  20. #20
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    Quote Originally Posted by Harry D Collier IV View Post
    So if I understand correctly the outer chainring on the MWOD + the outer cog on the dingle should = the inner chainring + the inner cog.
    The MWOD chainring sets look to have a huge difference in size between the two gears. Something like 20/33 or 22/36. Stupid question but is it possible to make a MWOD that is 33/36 and what kind of difference would this make between the two? Big enough to notice?
    If I made a 33/36 and then a 17/20 dingle everything should match up correct?
    You got it right - however, the rear forkends (which you use for chain tensioning) allows three teeth of range, so you don't need to be precise. For example if you want 36/20 and 33/20, you can do it without altering chain length. With the larger combo the rear wheel will be a bit closer to the front, that's all.

    33/20 and 36/17 is a good example and should work very well. 33/20 is good for general use - not frustrating even on a bit of commute - and 36/17 gets you good speeds.

    Now, how to get those chainrings is a bit trickier. Forget about the two-packs they offer, they are designed for gearies who want a crawl gear and speed gear. We don't want that big of a difference. The largest separate inner chainring is 26t. The spider doesn't look durable and I've seen them fail - I wouldn't use one. This is precisely why I suggested other cranks, because with regular MTB cranks you slap on your thirty-something tooth chainrings (easily available) and you're done. I'd ask around if any other cranks would clear the chainstays.

    EDIT: Seeing as wadester has recommended the Mr. Whirly spider, I don't want to make too harsh statements about it. I don't have personal experience with it (apart from handling one), I've only seen two of them broken and to me it looks like a faulty design. But this is just one opinion.

  21. #21
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    Quote Originally Posted by Saul Lumikko View Post
    EDIT: Seeing as wadester has recommended the Mr. Whirly spider, I don't want to make too harsh statements about it. I don't have personal experience with it (apart from handling one), I've only seen two of them broken and to me it looks like a faulty design. But this is just one opinion.
    You have a point. My spider bolts (the 58mm BCD part) loosened up on me a few rides after I started using it, and one "eyelet" got a bit munched. I "massaged" the tweak enough to work, and used blue loctite when I retightened it. That was several hundred miles ago. If I hadn't caught the loose bolts when I did (after I lost one - oops) the spider would have been trashed similar to some pics I've seen. YMMV. Always check new high load components closely for the first few rides.
    This isn't a "you're doing it wrong" topic.

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  22. #22
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    Popping in to say hi to another muni rider! "Hi!"
    I ride a 24" Conundrum.
    Fixed Gear Moonlander-image.jpg
    Cool to try a fixed fattie! Good luck!
    2010 Surly Conundrum
    2012 Pugsley
    2012 Felt Brougham
    2013 Salsa Colossal
    2013 All City Nature Boy
    2014 Big Dummy

  23. #23
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    I have looked up the Surly chainrings and they seem a good option. So I just buy it all separately Chainrings, spider, bottom bracket, and cranks and then throw them all together myself. This seems like the best option. I am sure that other companies make cranks and spiders that will work but I know the Surlys will fit so I will use them for the time being.
    What size do I need though. MM wise? I mean do the two chainrings need to be the same size or different. Like a 36t 110mm and a 39t 110mm or a 36t 94mm with a 39t 110mm?
    Nice to meet another conundrum rider as well. I wish they still made them. They are great to ride.

  24. #24
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    You bolt the spider to the five 58 mm BCD holes on the crank and the chainrings on both sides of the spider. The outer BCD of the spider and BCD of both chainrings must match. You'll put chainring bolts through all of them with the spider sandwiched in between.

    As for which outer BCD you should choose for the spider, I think the most sensible would be a size where suitable chainrings are easily available, 110 mm. But I believe the smaller 94 mm spider would be more durable because of smaller leverage.

  25. #25
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    I'm not entirely up to speed on the issues people have been having with their mr whirly spiders, but I think they were mostly confined to the 5 chainring bolt spiders, not the 4 chainring bolt ones. When there's 5 bolts they line up perfectly with the bolts on the crank arms which seems to weaken the spider.

    I've been using a 4 bolt spider and WTC ring for a few months without issue.

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