Wednesday, October 17, 2012

Fat Bike Style: 135mm vs 170mm

170mm fat bike hub
I've been thinking about fat bike frame designs of late. The times seem to be a changin' in that niche of cycling, and part of that has to do with how the frames are spaced in the rear.

To be sure- fat bikes weren't always "fat". Once they were ordinary mountain bikes. Riders found that the tires punched through the snow too easily, so there were a few tinkerers around that began to experiment.

These fellows first welded two rims together making the wheels wider, and mounting tires on that, then wide rims were made, and you know the rest. Frames had to be modified along the way. Of course, limitations existed.

One of those was the hub width of 135mm. Eventually, with the advent of single speed hubs, someone got the idea to use a rear single speed hub as a front hub, thus widening the front out to match the back, and allow for wheel swaps in case of free hub failure. One could put the front wheel in the back, and run the bike as a single speed, or fixed gear bike, to bail themselves out of the Arctic wilderness.

The Surly Pugsley picked up on this Arctic/Alaskan idea and propagated it with distribution to all corners of the earth for several years. Being able to use standard parts was important not only for survival in remote areas of the Northern latitudes, but for folks piecing together one of these from Surly's frame, fork, tire, and wheel  parts that were fat bike specific. It made sense then to use the "off set" frame idea.

Pugsley- The Standard Bearer
But now things are different. It started up there in Alaska with Fatback Bikes, then others picked up on the symmetrical rear for fat bikes which required a 170mm spaced rear hub. Hubs became easier to get in 170mm, and more are being added as we speak to the pile. Having to be limited to a 135mm rear hub is not an issue anymore, and the idea of front to rear wheel swaps is not important to 90+% of riders out there.

While there isn't really anything wrong in practice with an off set frame and off set wheel build to fit it, the symmetrical wheel build and frame theoretically should be a stronger wheel. Plus, it just looks less goofy. But again- Pugs and Moonlanders, (another Surly offering with an even more radically offset frame), are working great for a lot of riders.

However; it seems to this writer, just looking around the fat bike landscape, that Surly and maybe one other company are the only 135mm offset flag bearers, while just about everything else is a symmetrical rear/170mm layout. Which begs the question: "Is the industry going to 170mm rear ends and if so, where does that leave Surly and their fans?" Not that Surly or their fans care, but I just find it intriguing to think about.

I think I know at least part of the story concerning why it is that Surly so doggedly holds to it's ways of doing things concerning fat bikes, but ya gotta wonder, is that going to make sense five years from now? Ten? I wonder.

It's interesting to sit back and think about that, or better yet, think about that while riding your fat bike!


JR. Z. said...

Why not ask similarly about the track-ends that Surly uses. Once you slide a dedicated single-speed hub in the Surly track-end, it all makes sense. Sure, you could run a freewheeling 170mm hub as a SS with a spacer kit, but what about fixed gear (other than resorting to a TommiCog)? I love the fact that I can abuse my Pug without worrying about all the parts I'll be replacing. With a total of six well sealed Phil Wood bearings under me as the only (real) moving parts, I don't hesitate to ride right into the ocean or through the chemical soaked slush on the side of the road. Fatbikes, for me, are about the carefree fun I had when I was a kid. Therefore Surly's offset/track-ended bikes will always have a place in my heart :)

Guitar Ted said...

@JR. Z: While you may see all those "negatives" as reasons to stick to your Pugs, I, after 10 plus years of riding winters, have not seen any issues using cassette style hubs, vertical drop outs, or any issues using those hubs as single speed hubs.

Again- YMMV- but all your points do not really invalidate going to a 170mm rear hub standard, in my opinion and experiences.

jkeiffer said...

I don't have a need for full fat where I live. But I'm a full fat convert. I do not like that Surly's offerings use a rear hub as a front. I won't be able to use their forks, as I have no reason (like you mentioned) to ever need a rear hub in the front. Wish that was different. I won't worry about 170mm hubs, because that's not my need. (I think it sounds good for other though.)

RGB Nameless said...

135mm hubs are better because... infinite choice of hubs, and most of this hubs are not overpriced.

For me, even $100 Salsa Mukluk 3 hub is WAY overpriced, because for the same money I can buy a lot better and lighter 135mm hub...

When you use a doublewall rim, offset wheel is the same as non offset. When you use a wide 80-100mm single wall rim - straight wheel may be better.

JR. Z. said...

@GT: My goal was to, simply, present another (worry free) perspective, not to point out "negatives" or invalidate the standard. I totally understand draw. But in my 5 years of winter riding, I've seen cassettes turn into blocks of ice and brakes freeze both open and closed. In 12 years of off road riding, I've heard of deraillers ripped off by tall grass and freewheels getting stuck freewheeling due to dusty, muddy, or sandy conditions. Again, NOT saying cassettes or IGHs or, even freewheels are a "bad" thing, just pointing out that the option is still around (and will hopefully remain so) for those of us who use these bikes at their limits.

P.S. I'm the first one to admit that if I had the money, I'd have a 100mm/BFL capable symetrical frame built with custom (wide) flip-flop rear hub!

Guitar Ted said...

@RGB Nameless: Offset is not as strong, (theoretically, and probably in practice, laterally), which is far more important as these fat bikes get used for more than soft surfaces.

Yes- there are more 135mm hubs, but there are 170mm OLD hubs in a range of prices and more are coming. That wasn't the case four years ago, and with every new 170mm hub, your point gets less important. The point is that there is a tipping point where all these old arguments for 135mm hubs becomes a much less significant advantage. That time is quickly coming....

@JR.Z: I understand your "worry free" alternative for you is "X", for someone else, it may be "Y", (which was my point). Both are valid, but have little to do with where standards are going with fat bikes.

Matt Maxwell said...

Surly Fan = Honey Badger

Objectively the 170mm is probably better and maybe that's the way things will go, but plenty of bike fads have come and gone. In a few years will there even be fatbikes? I hope so, but who knows.

I just had someone come in to work today who needed four bolt disc rotors.

Guitar Ted said...

@Matt Maxwell: This===> "Surly Fan = Honey Badger"

Pretty much sums up a large portion of this debate.

I like Surly as much as the next guy, but I also don't see perpetuating a philosophy, which is becoming less practical, in the face of industry change as a good idea.

But what the heck do I know.

Say- do you have any four bolt rotors? ;>)

Nicholas Carman said...

The 135mm offset design has many advantages, all of which suit personal needs, not the fatbiking public as a whole Personally, I have been grateful to have access to quality, inexpensive rear hubs on several occasions. I don't have a lot of money, so this is an important feature to me. I have built 29" wheels for my Pugs, and have recently built lighter wheels with Marge Lite rims. Cheap hubs have made it all possible.

The offset in the frame is not the issue that we lose sleep over, but the asymmetrical use of the rim bothers our sensibilities. I do not think that the offset build significantly compromises the integrity of the wheel. In fact, the spoke angles are ideal, it is only the spoke bed offset that is unusual. I have done much more than ride snow on my offset Marge Lite rims, with no apparent ill effect. The wheel is in fine shape after much use, and abuse.

Finally, fitting an IGH to a 170mm fatbike is near impossible. Even with the Salsa spacer, which effectively creates an offset 135mm rear end, the options are limited. Dedicated offset designs still reign for IGH use.

Aside from these benefits, which do not affect all users, I support the move to dedicated 170mm rear ends, and sym. 135mm front spacing. In fact, 9zero7 debuted a 186mm rear spacing at Interbike, which allows the full range of gears, 100mm rims and BFL sized tires ,previously unavailable without drivetrain mods. The Phil Wood prototype fatbike used a 185mm rear end, although they are considering a 200mm rear end for better chain clearance, and prudence, if the project continues.

Guitar Ted said...

@Nicholas Carman: Again, you speak to my point that in the past the 135mm hub made sense due to costs/convenience. Much in the same way 26 inch wheels suited mountain biking, but this doesn't mean that either of those standards are best suited to the particular jobs we are referring to here.

My point is that these "advantages" are becoming less advantage and more "just the way things are done". Perhaps it is time to let that go and move on. That's where I am coming from

No doubt you and several hundreds of others have enjoyed offset wheel/frames for years. However; it stands to reason as a wheel builder that you strive for symmetry and even spoke tensions to get the strongest, longest lasting wheel. I do not believe offset fat bike technology is going to give us that.

If you can have the best way of doing something, (at a reasonable price, which is happening now), then why not?

It'll be interesting to see how this goes in the future, especially when suspension comes for fat bikes.

MG said...

Hahaha... I just about fell out of my chair laughing when I read Matt Maxwell's "In a few years, will there even be fatbikes?" question.

I think a more valid question may be, who will be left behind without a fatbike in a few years? Because, as I see it, for the foreseeable future, there are only going to be more and more great fatbikes/parts to choose from. And that includes 170mm spaced hubs.

I'll be buying another fatbike waaaaay before I even think about a 650B mountain bike. That much is certain.

MG said...

@Guitar Ted... When suspension comes, I hope they incorporate through axles. Even my rigid Mukluk has challenges with fles due to the QR skewers, so suspension will need through axles, bottom line.

Nicholas Carman said...

The combination of assym frames and offset spoke beds create more ideal spoke tension than most multi-speed road wheels. The spoke bed offset is the remaining issue. Have any offset wheels ever failed as a result of being built off center? I agree that sym. fat wheels are theoretically ideal, but I'm not sure that offset wheels are inferior for the conditions to which they are subjected.

I hope most fatbikes settle on a 170 or 185mm rear end and parts become available and affordable for all, as with 29" parts, etc. Aside from the benefits of cost and convenience, it will be nice to have at least one offset frame option in the future for penny pinchers, IGHs, and globe-trotting cycletourists searching for the most reparable option.

I think symmetrical wide rear ends are truly better, but they generally satisfy a theoretical issue, rather than an actual shortcoming. As an aside, It may be time to move to 145mm for standard mtbs. I would also welcome the return of offset 29er rims.

Guitar Ted said...

@Nicholas Carman: As to wheel durability, a respected wheel builder that has done several hundred fat bike wheels reported that he saw more failures with offset wheels than he did with symmetrical ones.

Of course, this may be a function of symmetrical wheels being fairly new for fatbikes, but none the less, it points up that the offset wheels do fail for some riders. Theoretically, the chances that a symmetrical wheel failing should be less. Even with single wall rims as a consideration.

On IGH hubs: Unles we are talking Rohloff, which is insanely expensive, IGH hubs just do not have the durability required for off road adventures. The axles are not heat treated due to the design requirements, and many fail due to this. So, it isn't a slam dunk idea, unless we are talking Rohloff, which is an entirely different design than most IGH hubs.

In my opinion, the Pinion Gear Box would be a far better solution, and you could run a symmetrical frame with 135mm spacing with that.

rideonpurpose said...

I have built up two fatbikes for "family" use in the last year. Both are built with nicer parts than a Mukluk 2 stock build... so I wasn't going "cheap". In both cases I went chose the frame based on keeping 135mm hubs front and rear.

Screw new random standards and screw the companies going away from their own roots and what used to make them cool to give them to us!

Guitar Ted said...

@rideonpurpose: Random standards? I think Greg and Pete and the other Alaskan guys that came up with some of these ideas would say that they were anything but "random".

Shoeless Joe said...

I am personally fed up with ordinary drive trains. I would love a fatbike but to buy one with a derailleur seems daft for the use it would get. having a part of a frame designed to fail - hanger - just pisses me off. Death to the derailleur hanger. I have had a alfine 11 and that didn't last long because i like to ride hard up steeps and the gear ratio outside shimano's recommended ratio range. The weight in the rear wheel just doesn't appeal. When are Shimano and or sram going to admit they should set a common standard with tha Germans at Pinion? Such slow progress.

Anonymous said...

Well I am a dedicated american even to the point of having custom parts made. I will never ride a Chinese or Taiwan frame or fork as I have seen them fail many times over. If surly went under today no sweat here as I do not ride Taiwan made bikes from Walmart anyhow...Jon

MG said...

Yeah, the fact that I ride for a British bike company that has its frames made in Taiwan makes me less of an American... LOL! I've seen as many US built frames fail as Taiwan built ones. Your flag-waving falls on deaf ears on that point.

But please do ride whatever bike makes you feel good... No argument there!