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Thread: Fat bikes

  1. #1
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    Default Fat bikes

    After pondering whether or not this is really the place to attempt to review a fat bike, the determination was made that this is the PERFECT place to post a review of a fat bike, precisely because this forum is so road oriented and fat bikes probably seem so ridiculous to people who have predispositions to skinny tired bikes (as they were to me, despite my predisposition to riding bikes on dirt)

    Iíll try not to make this about MY fat bike but context is appropriate so Iíll toss out some specs and history so people know where Iím coming from. IMO, thereís no such thing as an objective review; our judgments are colored by our past experience and current expectations.

    I built a fat bike a few years ago for an acquaintance that has since become a friend. Some of you might be familiar or even personally know RickyD who lives in MD and rides the trails that I grew up riding. We have similar tastes in trails, similar riding styles and objectives and I have a very good working knowledge of his ďhomeĒ trails so it wasnít too difficult to make some educated guesses about what would work for him. At the time, I canít say that I fully understood why anyone would intentionally ride a bike with enormous tires on those trails but we had some mutual trust so I went for it. He seems to be quite happy with it and his photography makes me pine for those mid-Atlantic trails so much that my curiosity about using a fat bike as an every day trail bike was piqued. Heís managed to inspire a few other people as well whoíve placed orders with me so I figured that building one for myself for R&D purposes was the only right thing to do.

    For those who dork out about such things, I arrived at a 68.5* HTA with 54mm of offset. 410mm chainstays, 60mm BB drop and 714mm front center. Itís a little unconventional but itís right in line with what I like and fits my riding style quite well.

    The only thing that really differentiates this from my 29ers are the wheels and aside from the fabrication challenges, the wheels only change the inertia and traction. Inertia, traction and to a small extent, steering.

    Back to more contextÖI started racing mountain bikes in the early Ď90ís. By the mid Ď90ís I finally accepted that I was way more interested in the various elements of technical riding available in the mid-atlantic than I was in putting in the required effort to be anything more than pack fodder at the XC races. Standing on the ďexpertĒ podium at a trials event was possible and the work put into it was even fun. My focus shifted, my riding style when out on trail rides shifted and the required equipment shifted. Thatís all just a really long way of saying that Iím fairly used to heavy tiresÖit was the only way to prevent constant pinch flats on the trails I enjoyed.

    The transition from DH tires on a 26Ē wheeled bike to moderately heavy tires on a 29er wasnít a big deal and this is when I finally get around to telling you that making the switch from moderately heavy tires on my 29er to the 1400g Nateís on my fat bike also wasnít a big deal. They take more effort to accelerate, thatís a fact, but from my perspective itís a non-issue. People who save grams in their tires may find the difference to be unappealing.

    Traction. This is where Iíve been blown away over and over again. In my experience so far on anything dry, traction seems unlimited. There are two sections at one of my regular spots that give me trouble. Both of them are technical, both of them are uphill and my fitness is what causes me problems. Now that Iím writing, it seems weird to propose that traction can overcome a fitness issue but let me explain. I can handle a bike pretty well but when I have tunnel vision because my heart rate is at 190 it all goes out the window. Keeping the cranks revolving around the BB is about as much as my brain can handle so navigating a loose, rocky, uphill S-bend is out of the question and timing my pedals to avoid rock strikes has long since leaked out of my brain. In these instances, the excess of traction provided by 4Ē wide tires removes some of the complication of line choice, the front wheel isnít deflected by an angled root or rock, it simply rolls forward. The rear wheel doesnít spin out while I shift my body weight forward to maintain momentum over the root step-up, it just hooks up. For me this has been a bigger revelation than full suspension.

    Thereís a different area where the abundance of traction has saved my ass. Some of my favorite trails ďlocalĒ to me are east of Mt. Hood. This is the time of year when the trails, especially the turns, accumulate dust. Those of you who are familiar should chime in, but to this east coastie, those conditions have been an interesting learning curve. On all of my other bikes, thereís a sweet spot between sitting back to let the front end float a bit when hauling ass down hills (and risking pushing the front wheel through the turn) and getting just the right amount weight on the front wheel to keep it engaged but not so much that it spoons and digs in to the powder too hard. The fat tires enable me to corner much faster. In fact I havenít been able to push it through a corner yet. With the 6Ē of talc in some of the corners at Knebal Springs, thatís a pretty amazing revelation to me.

    I generally stay off the trails if itís super muddy but Iíve ridden a few times in wet conditions. Traction on anything wet other than wood is still amazing. Wet roots will still put you on your ass just as quickly as a normal tire if youíre not paying attention. In deeper mud, the big tires are definitely squirmier than something normal but I havenít noticed a significant difference when itís just a soggy top surface.

    There is a bit of a learning curve when it comes to tire pressure. Iíve slowly been working backwards from 11psi. Most of the trails out here are non technical and thereís not too much worry about pinch flats. For me, at pressures north of 10psi, the front wheel rebounded harder than Iíd like in some situations. My last ride was at 8psi and it was by far my best experience. Iím going to drop it to 7psi on my next time out to see what changes. If I can tighten up my schedule and family responsibilities in the fall, I hope to head out east to put myself through the ringer for a long weekend or possibly a week of riding techy stuff. Itíll be fun to see if I still enjoy the bike as much for that type of riding.

    Iíve only had this bike for a couple of months and it still has the new bike mystique. I doubt itíll keep my off my 29er forever but the traction is addictive and itís not short on fun. Iím headed down to Oakridge, OR next weekend and am 90% certain that Iím taking the fatty with me despite the likelihood of being the guy on the clown bike. Itís all about how much fun can be had and it seems impossible that it would be less fun than my 29er.

    If you can get past the clownish appearance and youíre not counting grams, give one a try sometime. Itíll put a smile on your face.
    Sean Chaney
    www.vertigocycles.com
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  2. #2
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    Default Re: Fat bikes

    Thats rad. Thanks. I'm really looking forward to some quality 29+ tires to start hitting the market.
    Do you have any experience with any of the 29X3 or 2.75 from surly?
     

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    Default Re: Fat bikes

    Very interesting. I'm not able to make use of a fat bike in my current life, but thanks a lot for taking the time to write this - we bike nerds always love a well-considered review from a person of experience!
    Andy Cohen

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    Default Re: Fat bikes

    Quote Originally Posted by miwuksurfer View Post
    Thats rad. Thanks. I'm really looking forward to some quality 29+ tires to start hitting the market.
    Do you have any experience with any of the 29X3 or 2.75 from surly?
    Not yet. This new found addiction to traction has me thinking hard about it though. I was going to build myself a 27.5 bike this winter just to get some information on it but my fatbike experience has morphed that into a 27.5+ situation. I have an order in for a mixed wheel size 27.5+/29+ bike that'll come up by winter and another one for a 26+ but I don't have any time on any of those platforms. I have elevated expectations though and I'm looking forward to digging into the builds.

    FWIW, my buddy Jon has been telling me that he's unimpressed with the 29+ tire offerings thus far.
    Sean Chaney
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    Default Re: Fat bikes

    Quote Originally Posted by VertigoCycles View Post
    For those who dork out about such things, I arrived at a 68.5* HTA with 54mm of offset. 410mm chainstays, 60mm BB drop and 714mm front center. It’s a little unconventional but it’s right in line with what I like and fits my riding style quite well.
    Can we get a picture? Would love to see how you got the tubes together, especially the chainstays.

    Quote Originally Posted by VertigoCycles View Post
    There is a bit of a learning curve when it comes to tire pressure. I’ve slowly been working backwards from 11psi. Most of the trails out here are non technical and there’s not too much worry about pinch flats. For me, at pressures north of 10psi, the front wheel rebounded harder than I’d like in some situations. My last ride was at 8psi and it was by far my best experience. I’m going to drop it to 7psi on my next time out to see what changes.
    Which gauge are you using?

    I love the Meiser Presta Accu-Gage in 30 and 60psi, and they make a 15psi version now!
    Fred Blasdel

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    Default Re: Fat bikes

    Quote Originally Posted by blasdelf View Post
    Can we get a picture? Would love to see how you got the tubes together, especially the chainstays.
    Untitled by VertigoCycles, on Flickr

    Clearance is close, but not as close as the photo looks. I made a 120mm wide PF30 BB shell for this bike and another one I'm starting next week.

    Quote Originally Posted by blasdelf View Post
    Which gauge are you using?

    I love the Meiser Presta Accu-Gage in 30 and 60psi, and they make a 15psi version now!
    I'm using the Meiser 15psi gage. I figure that even if the exact reading isn't accurate, it's a good comparator since I'm starting from scratch with my understanding of how these tires work.
    Sean Chaney
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    Default Re: Fat bikes

    Good write up Sean. I'm always surprised at how good fat bikes feel on our more sugar sandy FL trails. Hitting a deep sand section and the bike not even slowing down is a feeling that is really welcome.

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    Default Re: Fat bikes

    Quote Originally Posted by VertigoCycles View Post
    I'm using the Meiser 15psi gage. I figure that even if the exact reading isn't accurate, it's a good comparator since I'm starting from scratch with my understanding of how these tires work.
    I haven't found anything remotely as accurate, even nice floor pumps tend to spit out complete nonsense at lower pressures

    They're at least very precise, the measurements are repeatable and the needle moves in increments much smaller than the hashmarks
    Fred Blasdel

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    Default Re: Fat bikes

    Quote Originally Posted by blasdelf View Post
    I haven't found anything remotely as accurate, even nice floor pumps tend to spit out complete nonsense at lower pressures

    They're at least very precise, the measurements are repeatable and the needle moves in increments much smaller than the hashmarks
    I also have one of those Craftsman handheld compressors with an integrated digital gage (measures to 1/10ths) that runs off the same battery as my drill. It seems to agree with the Meiser but it's finicky with the state of the battery and the display only works when the charge is near 100%.
    Sean Chaney
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    Default Re: Fat bikes

    I'd like to ride a fatty. They just look so slow....

    At the GA SS State Championships a few years ago there was a guy on a Pugsley. The course was FAST, I averaged 13+mph and I'm not that quick. A few corners were slightly off camber and pretty sketchy at speed, but word around camp was that the fatty abosolutely FLEW through those corners thanks to all the traction of those big fat tires.



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    Default Re: Fat bikes

    Grew up riding road, then caught the singletrack bug in the late '80s - used to ride many state parks and powerlines year round in MA, S. VT, etc., then my attention gradually shifted back to road.

    Fast forward 20+ years, when the correct number of bikes is n+1, and suddenly a fat bike looks like a good time - particularly for winter riding in the NE.

    Reviews like this fuel the itch to demo...
     

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    Default Re: Fat bikes

    Nice writing, Sean.

    I could ride a Salsa Mukluk this winter and liked it a lot. I could clear rocky sections despite the hard compound of the On One Floater tires. At first, the bike over steered at high speeds because of the weight, but three turns later you are anticipating that effect.

    410 mm chainstays? That sounds very good, I love short chainstays on my bikes.

    Vertigo Cycles Titanium Fat Bike por bundokbiker, en Flickr

    Sweet!
    luis prado alonso

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    Default Re: Fat bikes

    Good write up Sean. Welcome to the Wide World of Fat. (WWF... damn, that one was taken.) It's a black hole of fun from here...

    The first thing I also noticed on early rides upon my own fat bikes was the sheer amount of traction and how the tires hook up on steep, technical climbs. You're also finding how tire pressure can really play a huge role with how the bike handles with only small changes. Myself, I mostly concentrate riding in snow on fatties with the rare ride on dirt and it's interesting how the conditions change, tire pressure can be added/dropped to match it to improve the performance and traction. I've become a snow connoisseur by chance because of those fat tires. My own runs 29+ during the spring, summer and fall. I'd say 29+ most likely is one of the smoothest running and feeling fully rigid bikes I've ever ridden and I agree with Jon that the 29+ tire options currently out there are less than impressive. The fun factor is there however. It sounds like there is a bunch in the pipe though for that tire/wheel size in terms of tires from rumors. 29+ is a really interesting wheel/tire size that has a lot of possibilities. It has a lot of the traction attributes and feel that a true fat wheel does but not nearly as much rolling resistance so it's a really interesting "best of both worlds" scenario from what I have found.

    The one thing that I found here on the east coast that's tricky is a fat bike in techy conditions at high speed. Sometimes that front end gets to bouncing or hopping and you have to check speed quickly. The other interesting thing is geometry setups and how that changes performance in different conditions from techy trails on dirt, flat out swooping singletrack to sandy conditions or then on snow. Snow is a completely different animal in many ways and the bike at speed will actually pick up and float or hover. At speed, you can push and slide the bike through turns moto style which is a blast on snowmobile trails. There's a lot of that here in NH, and most rides are up, up, up and then all the way back down again and going flat out on a fat bike laying into turns on snow is about as fun as it gets. Crash? Whatever. You're off into the sauce and it's just powder.. Those tires hum at speed. Not to mention the snowmobilers all stop and talk to you - you're not a weirdo or a clown. They think it's as cool as it gets. Or at least the ones I've bumped into! But the experience of riding the same trails that you do when there isn't any snow is kind of special. Magical I'd say as the environment around you is so different than during the spring or summer. It's kind of otherworldly to be out in the snow riding your fat bike on singletrack you normally would ride on your 29er. 5" tires are a game changer in snow - that's where it's at. Techy trails, 3-4" tires are where it's at. Rim width also plays a role too as it either pinches the sidewalls or spreads them so the tires profile changes depending on how wide the rim is and how the tire performs also is effected. This plays well with my sensibilities as I really enjoy working with subtleties and nuances.

    In contrast, ride that fat bike for a good month or so, then pull out your 29er. You will feel like greased lightning. The first time I did this, I could not believe how fast the bike felt without all that rolling resistance beneath me. It's apparent when you first step on a fat bike just how much rolling resistance is present, but 5 minutes later, that fun factor melts it away and it becomes relative only to be screamingly obvious when you step back onto your 29er. Both have their place in my own stable though, and I love them for their stark differences and subtle similarities. I do not think I would trade one for the other and enjoy both equally. But I really do like my 29er when it comes to dirt and singletrack - I will be honest about that one!

    But if I had to get rid of all of my bikes and keep one, I'd keep my fat bike and that extra set of 29+ wheels. IMO: That's the one bike to rule them all for someone who has to ride 4 seasons, and the seasons are seasons that include snow. 29+ and fatties with 5" tires are about the same diameter, so no changes in geo for the most part. Win win. (The next two builds are actually Fat bikes with 29+ wheelsets in tow.)

    For me, fat bikes really get to the root of what was so attractive to me about "mountain bikes": Big, fat nobby tires. Sweet singletrack in front of me. Blasting through turns. Just out there in the woods having fun. That's it in a nutshell.
    Kristofer Henry : 44 BIKES : Made to Shredô
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    Default Re: Fat bikes

    I'm just happy to see all these singlespeed fatbikes! Gives me hope.

    Has everyone pretty much settled on 170 mm symmetrical rearends (or 177 for the TA crowd)?
    Will Neide (pronounced Nighty, like the thing worn to bed)

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    Default Re: Fat bikes

    Quote Originally Posted by Will Neide View Post
    I'm just happy to see all these singlespeed fatbikes! Gives me hope.

    Has everyone pretty much settled on 170 mm symmetrical rearends (or 177 for the TA crowd)?
    IMO, symmetrical is where it's at. 135mm QR, or 15x142mm TA for front (rigid). Rock Shox's introduction of the Bluto sports a 15x150mm TA. That "should" be the standard moving forward for suspension fat forks. Rear: 170mm QR or 177mm TA for 3.8-4" tires. 190mm QR or 197mm TA for 5" tires.

    170 or 177mm for TA plays best with 3.8-4" tires. You can build around a 5" tire with 170 or 177mm TA but chainline with tire clearance becomes an issue. Wolftooth for one makes a ring that effectively moves the ring 5mm outboard, so you gain some room, but you also increase chain overlap when in the 36 or higher gear. My own runs 36t max with a 170mm rear end in combination with this Wolftooth ring meant for 190 rear ends.

    190/197mm rear axle spacing is really to deal with 5" tires to reduce the chain rub issue with the tire and improve chainline. I'm highly considering rebuilding my own after this winter around a 190mm rear axle spacing. One of the two next builds will be 190mm rear spacing, and I want to see just how much of a factor this plays with 5" tires. The chainline now is not exactly ideal with a 170mm rear axle spacing and a 5" tire. It's ok, but it's close! The wolftooth ring made a huge different for clearances.

    Where it came into play for me was really low pressure to gain traction in really slippery conditions as the day was warm or snow was melting - the tire would not rub but if you hit a large enough object, or went through a sizable "dip" in the trail, that displaced the tires and changed it's shape, the chain would rub as it left the chainring, so the underside of the chain/chainring only. So occasionally at really low pressures, I'd hear this odd rub noise and after watching and looking down as I rode, I figured out where the noise was coming from. But I also learned that with 5" tires, I did not need to run as low of pressure in certain conditions like I had when running say a 3.8 Nate out back. The change in tire pressure creates a larger tire patch, so as much as you're attempting to gain traction, you're also looking to gain float by adjusting your tire pressure to increase the tire's contact patch. This works the same way on sandy conditions too. Traction and float = change in tire pressure on a fat bike.

    It seems that 3-4" tires are settling into a rhythm for dirt/trail. 5" tires on 70-100mm wide rims are better suited for snow. Once you exceed 4" on dirt, you're not really gaining anything except rolling resistance IMO. 1" difference in diameter doesn't seem like much, but it's the difference between punching through and not in soft conditions on snow which means riding and not hiking. I was blown away by this change this past winter.
    Kristofer Henry : 44 BIKES : Made to Shredô
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    Default Re: Fat bikes

    Quote Originally Posted by Will Neide View Post
    I'm just happy to see all these singlespeed fatbikes! Gives me hope.

    Has everyone pretty much settled on 170 mm symmetrical rearends (or 177 for the TA crowd)?
    All the bikes I have in the pipe are for 197 thru back ends. Titanium can only be squished so much for tire/ring clearance and with the stays getting super short, you just can't fit it all in there without moving something out of the way. In my case, I'm moving the chainring (and thus the cassette) out to the drive side to get more clearance.
    Sean Chaney
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    Default Re: Fat bikes

    A while back Salsa posted a great explanation of the drivetrain/tire interactions:



    http://salsacycles.com/culture/tech_..._tire_capacity
    Fred Blasdel

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    Default Re: Fat bikes

    Quote Originally Posted by VertigoCycles View Post
    All the bikes I have in the pipe are for 197 thru back ends. Titanium can only be squished so much for tire/ring clearance and with the stays getting super short, you just can't fit it all in there without moving something out of the way. In my case, I'm moving the chainring (and thus the cassette) out to the drive side to get more clearance.
    I'll be switching over to 190mm as everyone has asked for room for 5" tires whether they need it or not. It's a good move, but I'm happy that I experimented in 170mm and 5" tires because if the request ever does come in (which it has), I know I can make it all work and still have a pretty tight setup. 170mm is really ideal at 3.8/4" tires. I've also noted that the larger tires kind of like a little more wheelbase/chainstay length. Too short and it gets a bit on the choppy feeling side I feel. (this is in regards to 5" fat and 29+)

    Quote Originally Posted by blasdelf View Post
    A while back Salsa posted a great explanation of the drivetrain/tire interactions:
    And one of the reasons I push people towards 1x setups on fat bikes. Especially with the newer cassettes and 10/11 speed options in combination with thick/thin rings. I've spent 2 winters on the same Wolftooth ring and as worn as it has gotten, I have still not lost a chain.
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    Quote Originally Posted by fortyfour View Post
    I'll be switching over to 190mm as everyone has asked for room for 5" tires whether they need it or not.
    I have yet to have a conversation with someone interested in a fat bike that didn't want 5" clearance. Now that the Bluto is out, you'll start to see things trending around suspension forks and associated geometry as well.
    Will Neide (pronounced Nighty, like the thing worn to bed)

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    Default Re: Fat bikes

    Quote Originally Posted by Will Neide View Post
    I have yet to have a conversation with someone interested in a fat bike that didn't want 5" clearance. Now that the Bluto is out, you'll start to see things trending around suspension forks and associated geometry as well.
    It'll be interesting to see what small builders are going to do to get around the massively wide crown of the Bluto. Luckily for the steel builders there are pre-bent down tubes available...for the ti guys, not so much.
    Sean Chaney
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