Chinese Carbon MTB > Fat Bikes
Crank for 120mm fat bike frame bottom bracket
PeterQ:
Cuz we make fat bike frames with 120mm threaded bottom bracket, do you guys know what crank will fit for these frames?
Chadding:
Wait until someone else confirms it, Peter, but I'm pretty sure these will work fine on the Fat Chiner:
http://www.universalcycles.com/shopping/product_details.php?id=57213
peteroaknyc:
HI,
just out of curiosity , is it possible to make the fat bikes with 73mm bb schell???I'am not into fatbikes,but wanted to start a project with one of yours peter, but than i saw that the bb is not 73mm.I need it for a middrive ebike.
Greets Peter
Akchugacher:
Wanting to pick up a fat frame but have 2 issues/concerns with the Chinese frames.
1. All the major US carbon frames (Corvus, 907, borealis) do a 197 rear with 100mm bottom bracket. but all the 197mm rear Chinese frames do a 120mm bottom bracket. It makes sense for proper chain alignment yet US companies are not doing the 120mm bottom bracket. Does anyone notice poor chain alignment on their US frames? maybe 1x drives fix that issue? The 120mm BB limits the available cranksets and makes you pedal like a bowlegged cowboy, lending itself to potential injuries if putting in lots of miles. The 190mm rear does have a 100mm but that brings me to the second issue
2. this has been mentioned but not sufficiently answered in my mind. a 190mm rear that has a through axle? Are there many hubs available to build off this sort of wheel?
Thanks in advance for the help
PS sorry I posted this under another topic but thought it might fit better under this discussion
cmh:
--- Quote from: Akchugacher on September 12, 2014, 10:23:31 AM ---Wanting to pick up a fat frame but have 2 issues/concerns with the Chinese frames.
1. All the major US carbon frames (Corvus, 907, borealis) do a 197 rear with 100mm bottom bracket. but all the 197mm rear Chinese frames do a 120mm bottom bracket. It makes sense for proper chain alignment yet US companies are not doing the 120mm bottom bracket. Does anyone notice poor chain alignment on their US frames? maybe 1x drives fix that issue? The 120mm BB limits the available cranksets and makes you pedal like a bowlegged cowboy, lending itself to potential injuries if putting in lots of miles. The 190mm rear does have a 100mm but that brings me to the second issue
--- End quote ---
As I understand it, a 190mm frame with a 100mm BB uses a longer spindle, with spacers on both sides to get the crank arms out to get the chainline necessary for the 190mm spacing and the wider tires. So, in this case, the 120mm BB actually gives you a wider support from the bearings and makes the extra spacers unnecessary so is actually a kinda cool idea. What's surprising is that the 120mm BB isn't common from all the other 190mm frames. That's actually really effin' cool and should result in a massively strong BB area.
If you don't believe me, that's cool, I'm still getting all the sizes and standards under control and might have it wrong, but before you call foul, check out this chart from RaceFace:
http://raceface.com/comp/pdf/FatBike-CrankSetup-Chainline.pdf
Looking in the first green block, the 190mm rear spacing specifies a 189mm Cinch axle and a 11.5mm spacer on each side, whereas a 170mm rear spacing specifies a 169mm Cinch axle with only a 1.5mm spacer on each side. Now if you had a 120mm BB like the Chiner fatties, you could skip the 11.5mm spacers and use the 1.5mm spacers and have 20mm extra width to your BB bearings.
If you're really worried about the Q factor - well, first, don't get a fat bike. ;D But if you're still worried about the Q factor for a 190mm rear spaced bike, sure, you could technically run a setup designed for a 170mm rear (with the narrower 100mm BB) but your chainline would now be off compared to the rear cassette. Also, depending on your crank setup - you might not be able to run the really wide tires due to the chain interfering. Notice that the max. recommended tire width for the 170mm rear spaced setup is only 4.0" vs. the 5.0" of the 190mm rear spacing. That's the whole point - move everything out farther so you can fit the wider tire.
Like I said, this is as I understand it right now, I might be wrong. Sometimes when new bike standards come out it seems like it's a national secret and nobody actually wants you to understand it. Plus, there's usually a bunch of folks who don't understand it who think they do and write articles that just confuse things. :o Eventually, however, the real facts percolate up through the BS and it starts to make sense - just in time for the Next Big Thing (tm) to come out and render everything useless. ;)
--- Quote ---2. this has been mentioned but not sufficiently answered in my mind. a 190mm rear that has a through axle? Are there many hubs available to build off this sort of wheel?
Thanks in advance for the help
PS sorry I posted this under another topic but thought it might fit better under this discussion
--- End quote ---
Yet another place where the standards are all over the place - ಠ_ಠ - and there are a ton of different rear spacing options. As I understand it at this point, though, for our purposes there are two standards - the 170mm and the 190mm rear end. Either a 170 or 190mm hub is quick release only. For thru-axles (really surprised that a QR is even an option with triangles that damned wide) it's just like the 135->142mm jump - add 3.5mm to either side to locate the wheel, and you get a 7mm wider hub OLD, so 177 or 197mm. If someone is actually making a 170 or 190mm thru-axle, I'd guess it's missing the extra length on the ends to locate the wheel in the rear triangle. That's just a guess for me, but personally I'd say that if you're getting 190 it's a QR and if it's 197 then it's a thru-axle.
Notice that their latest fatty frame, the IP-N019, lists exactly that - the QR or TA options with the appropriate sizes:
http://www.xmiplay.com/ProductDetails1693
...but amusingly enough, it's back down to the 100mm BB shell width. :D
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