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Ron

Seeking the next best ski
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If you are in the market for a new fat bike, you have undoubtedly seen a few new bikes featuring 27.5 wheels. Which is better: 27.5 or 26? Hopefully, this article will help with the buying decision. I did a ton of investigation and interviews, including an interview with Why Cycles to get to the facts. Before the review, read on for the advantages of 27.5-in. wheels and information on tires and tire pressure (PSI).

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  • Fat bikes have only been designed around 27.5 wheels for a couple of years. The advantages to a 27.5 are the ability to run a narrower fat tire and get the same or greater diameter with increased tire patch contact for increased traction, decreased rolling resistance, and lower PSIs for more comfort. The sidewalls on a 27.5 tire are lower and stiffer, improving handling and cornering. The 27.5 also has a improved attack angle, reducing resistance in deeper snow or loose conditions.
  • 26-in. wheels are claimed to be better in deep snow or loose conditions, but that claim is based on comparing a 26x4.6/5.0 tire to a 27.5x3.8 tire. That's true, however, 27.5x4.5 tires are taller, have the same or greater footprint, and, due to lower sidewalls, have improved handling ability.
  • 26-in. wheels claim to "spin up" faster. This isn't true unless the tire radius is less than a 27.5-in. wheel and tire!
  • "Can you run a 27.5 on a 26 frame?" Even if you can fit the wheel and tire on your 26 bike, a few things can occur to the geometry of a frame designed around a 26 wheel: the bottom bracket height changes as well as the head tube angle, wheel flop, and Trail. All of this adds up to a bike that wasn't optimized for that wheel size.
  • You can run a 26x4.5 or 5.0 tire on a 27.5 frame. If you so desire, you can easily run a 26, but why?
  • The real issue comes down to tires. 27.5 wheels for fat bikes are relatively new. There are only a handful of tires available and all but the Bontrager Barbagazi 4.5 are 3.8 or 4.0. To date, Trek, Farley, and Why Cycles Big Iron are the only companies that specify their bikes can accommodate tires wider than 4.0 in Why? A 26x4.6 tire (about the max width of 26-in. tires) is about the same height as a 27.5x4.0 tire, so the rear triangle, fork, bottom bracket, and head tube must be designed for taller tires. Manufacturers will need to radically modify frames' geometry to accommodate tires larger than 27.5x4.0. That costs a lot of money for R&D.
  • Tire selection will have the biggest effect on your fat bike. Most riders on 27.5 wheels are running their 3.8s at 8-14 PSI on dirt and as low as 1-3 PSI in the snow. Even 0.5 lb of pressure can make a difference. For winter riding, you may want studs or stickier rubber compositions. Tread design and height are also important factors. So, if you demo a bike, make sure you get the pressure dialed as well as the right tire for the right temperature and terrain you are riding. Ride with a pump and gauge. And go tubeless!


The Big Iron

I toyed around with the idea of getting a fattie for about 2 years and finally pulled the trigger on a Why Cycles "Big Iron." Why Cycles is based in Carbondale, CO. They offer three tiers of build levels but what's really cool about Why Cycles is that you can customize your bike around your wants and needs. Since the company sells direct to consumer, it offers a 30-day money-back return policy. All Why Cycles frames are titanium. The Big Iron comes with a Bontrager Haru Pro full carbon fork and is designed around a 27.5-in. wheel. The build weight of my large frame without pedals is 25 lb 10 oz. For comparison below, I used the Trek Farley, 19.5-in. frame and the Salsa Beargrease in large. I also used the Otso Voytek and Rocky Mountain Suzi Q in my research.

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Some comments on geometry where it pertains to fat bikes:
  • Tire size. After riding the Barbagazi, I strongly recommend a bike that can run a 4.5 tire. The Barbagazi is seated at 4.45 in. on the I9/HED, 82mm internal width rims and measure 31 in. tall.
  • Head tube angle. 68.7°. Modern fat bikes are going to slacker head tube angles, making them more stable and allowing a better angle of contact in snow. You may think that's too steep, but If the head is too slack, it will increase the trail and wheel flop to the point where the bike is unstable and ponderous. I found a range of 69° down to 68° across the field.
  • Chain stay length. Like the Farley, the Why Cycles also features an adjustable rear to allow for tire space as well as tweaking your ride. For riding in rocky terrain or deeper or loose snow, or touring with weight and bags, you might want a longer chain stay. Shorter will make it snappy and quick.
  • Trail. The Big Iron's trail of 98 is a nice blend of stability and quickness. Since you are pedaling a ginormous front end, how it reacts to inertia and input is very important! Trek Farley is 91. A lower number tends to make for quicker turning but can be less stable.
  • Standover height. When wandering off a packed trail and sinking into deep snow, you want a bike with a slanted top tube with plenty of standover. It also provides more room in the frame to stow gear.

How I Spec'd My Big Iron
  • I9/HED Carbon 825 "Big Rig" wheels (see wheel image here). There is no better upgrade than a good set of wheels and hubs. I9 Fat Bike hubs come with grease that is rated down to -40°F!
  • Bontrager Barbagazi 4.5-in. tires. Although marketed for snow, these babies roll with gobs of traction!
  • Revive 160 dropper post. You need to buy a dropper that is weather- and temperature-appropriate.
  • The drive train is a SRAM Eagle-based mix with GX rear, XX1, 30t cranks paired with a 10-50 cassette.
  • SRAM XO1 RS brakes. According to many articles, for cold weather, DOT or Mineral will work but DOT is preferred, especially below -15°F. Riding in super cold, below -30°F? Go mechanical.
  • Enve M6, 780mm handlebars. Wider bars with short stems and a long reach make for stability.
  • Diety stem and "bits" in lime green to match; super short stem pairs with the wide bars.

Initial Observations

I have to say, this bike is beautiful! The overall shape of the frame, badass HED I9 wheels, and green accents look awesome. I own a Moots (handmade Ti frames in Steamboat), and I was skeptical about the welding and frame build, but the welds are clean and precise -- not up to the same level of the Moots, but close enough, IMHO, Why Cycles has a more advanced geometry. Just look at the images below. Beautifully shaped Ti tubing most notable in the down tube where it's "ovalized" for vertical compliance and horizontal stability, and the rear and chain stays have a noticeable double S curve, allowing tire clearance and ride compliance. There is some really well-done etching on the frame, too.

Ride Impressions

The one word to sum the bike is FUN! I rode an 8-mi loop that has a bit of everything from a 14% section of climbing (and descent) to rock gardens to fast hard pack. I set the tire pressure at 10 PSI. On pavement you can feel the drag of the monster-sized Barbagazis, but once you get onto the trail, you lose the majority of the drag and feel the incredible traction and unstoppable rollover power. The titanium has a very nice feel; it really helps to mute vibration; combined with the big tires, I never felt the need for a suspension fork.

The trail starts with a moderate climb and goes into several switchbacks. I was laughing on the first climb; the tire traction seemingly pulls you up the hill. Going into the switchbacks, I was shocked how nimble the Big Iron was in the corners. I was expecting the front tire to wander or want to go straight but it handled much like my Yeti SB5. Continuing up, I went through a section of irregular jagged rocks where I would normally thread my tire through; with the Big Iron, you just roll over it! No problems and super fun. On the way down, the dropper worked flawlessly and comes with a great remote trigger. You just point and roll with the bike. I was flying down sections letting the tires soak up the hits and the Big Iron was plenty stable. Part of the stability is the 68.7° head angle, which is slack enough for descending and provides stability at slow speeds. Descending switchbacks was unreal. Due to the tire width, you could stand on the outside pedal and tilt the bike more than on my Yeti. The Big Iron just slithered through almost effortlessly. I don't think I will be adjusting the chain stay from the factory setting from midpoint, where the bike feels very balanced.

Overall, the Big Iron was a total blast and I am sold! I will be testing different PSIs, and in spring I will test 3.8 tires to see how they differ from the 4.5s. I encourage riders to get on a fattie to see for themselves that these bikes aren't ponderous, lethargic beasts only for snow but are rather super fun, quick, and agile. No, they wont replace your 150mm full suspension bike, but they are far more versatile than you might think.

Please click below for full-size images of frame details.
 

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Ron

Ron

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@Tom K. Seems like Trek is "all-in" on 27.5 Fatties. The Haro pro carbon fork is sweet and their tires are really nice. The Barbagazi is amazingly light, ~1230 for a 4.5 is incredible.
 

Jersey Skier

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No, they wont replace your 150mm full suspension bike, but they are far more versatile than you might think.

Please click below for full-size images of frame details.

Throw a Manitou Mastodon on the front and you might take that statement back.
 
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Tom K.

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@Tom K. Seems like Trek is "all-in" on 27.5 Fatties. The Haro pro carbon fork is sweet and their tires are really nice. The Barbagazi is amazingly light, ~1230 for a 4.5 is incredible.

IIRC, that's been the case for awhile, now. I came close to a fat bike a few years back, but it would be a silly indulgence in the PNW. There is seldom a period over 10 days where I cannot go on some kind of "regular" bike ride, and when that happens, it usually means exceptional skiing!
 
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Ron

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Don’t under estimate just how much fun these are on dirt. Total blast
 

Jwrags

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While I like the look of your fun on the new bike I like the look of snow on Mt. Werner in the background better:daffy:
 
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Ron

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My Friend was riding on 26x40 tires. I jumped on it to feel the difference. It was like riding a kids bike. The wheels felt tiny. Yep, it spun up fast, but too fast, I much preferred the traction and roll of the 27.5x4.5's. You would finesse the bike better especially on the climbs.
 

Blue Streak

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Do you have studdable tires for the winter?
They make them, right?
Or are the stock tires safe for icy and snowy roads?
 
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Thought I would add this to the end of the fat bike review since the Why Cycles Big Iron summer skin conversion to 29x3.0.

I decided to go 29+ based on the recommendation of Andrew (owner of Why Cycles) I had Mike Curiak https://lacemine29.com. build a set of wheels. Mike specializes in 29" wheelsets and has built well over 10,000 sets. He came highly recommended by a couple pugs including @Tom K. who knows him personally. Mike is also active on MTBR.COM and builds a lot of wheel sets for those folks too. He is also a Mountain Bike Hall of Fame member with a. list of achievements and world records. Mike built me a set of Derby i40 carbon wheels with DT Swiss 350's. Derby's are a CO company that has a great reputation for quality rims and stands behind their products. Mike took the time to really understand my needs and built a great wheelset. In less than a week, I had them at my doorstep. The entire process was professional and a pleasure, I cant recommend him highly enough.

I picked up a FOX 2020 34 130 fork from The Pros Closet for $550.00. They had some OEM closeout blemished forks. I couldn't find anything wrong on mine. Killer deal.

Got out on my first ride in 2 years, Felt great to climb up Emerald mountain. I did a short ride, maybe 8 miles with about 1500 or so climbing. Gotta say, the 29x3.0 is a blast to ride on flowy Xc stuff with occasional rock gardens. I ran the tires at 12 front 13 rear and with the 130 Fox fork, it was a great ride, honestly did not miss the rear shock one bit. Emerald starts with a 1/2 mile slog of a ~10% avg climb (starts at 12) and then once your on the trails its flowy switchbacks going in and out of trees. As you get up about 800’ it goes into thick Aspens with tall ferns and wildflowers and higher up it turns into thick evergreens. The 3.0 tires have such massive grip even with the modestly treaded Bontrager XR2 tires front and rear, I had no issues on our hard packed dirt with some moon dust over top. They climb extremely well and roll over anything in their path. Despite all this, they don’t feel ponderous or heavy and we’re quite easily steered along the trail between rocks and roots. I am not sure of the actual geometry of the fork now but it’s 68.7 when setup with 27.5x 4.5 tires but now I’m running a Fox 34 130 with about 25% sag. That said, on the down, it had a nice balanced feel and I didn’t find the front end squirrelly or having to force it on tighter switchbacks. The bike flowed really well. Maybe even smoother than the Yeti and that’s saying a lot. Climbing, I set the fork to its mid position for small hits and open for the descent. I set my fork up at about mid-range rebound and dampening; A couple of clicks to the faster and firmer side. This worked extremely well. It was the first time on the Fox 34 2020 fork and I was very happy with its performance. Very smooth and effective on small Rapid succession hits and nice smooth rebound on larger Hits. On the down, there are several rock gardens that the bike just rolled though like they were pebbles and the 130 fork was plenty for bigger hits along the way. Not once did I feel the need for a rear shock. I hover-butt through rough terrain anyway but with the 3.0 running at low PSI, it acts like a rear shock. The BIG IRON handles beautifully in the snow with the big 4.5 tires and even nicer with the 3.0’s. I wasn’t sure what I was getting into when I set this up but I am loving it. Its a shame because there’s only a few 29 plus bikes out there and for those riding xc stuff this is all you need. Trek may have a few Staches and WHY CYLES makes a Plus for Bike packing but why not get a bike setup like this and save a bunch of weight and a ton of money? If you are thinking of getting a Fat bike for winter (and I think you should), I would suggest a BIG IRON and buy another fork and wheelset for summer. If you are riding mostly XC stuff, you will find this is all you need and you will have 2 bikes in one. take the money and buy some more ski's. :).



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Tom K.

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@Ron, looks like a blast!

Did the switch from fat bike tires and wheels to 29+ affect your BB height much?
 
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I cant say for sure but probably some. The 29x3 is about the same height as a 27.5x4.5, I would imagine that with the fork sag, it would be a little lower. No pedal strikes yesterday though. it pedaled great.
 
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what I can tell you is that tire pressure on the 3.0 is critical. too much you're going to get bounce. at the low pressures I ran, the ride was smooth and assured. I really was surprised at how much chatter the rear tire absorbed. I have been a "wider is better" advocate for years and love wider tires so this is right in my wheelhouse. I love the ride of the big wheels, the roll-over, massive grip and general feel is awesome. they kick ass when climbing on switchbacks. you get them rolling and on tight, steep corners, and they just go right up. :)
 

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Some great views of Reno from the Northwest
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UPDATE: I've ridden the 29+ setup now several rides and settled in on 12 psi front 13.5 rear. Yeah, the half a pound psi is noticeable. its right where any bounce is removed on my 172 plus gear body. 13 is pretty good as well,I never feel tire squirm.

the Bontrager XR2, 3.0's are about 860 grams (Many 2.6's are 800+) so they dont feel ponderous or sluggish at all. the moderate tread works well on the mix of trail conditions; hardpack , moon dust, moderate roots, rocks and some areas of 1" gravel/stone. I think the width of the tire affords them good grip. The only area where I find I need to be a little cautious is carrying too much speed into corners with loose soil; they dont bite as well but I wouldn't give that up for just how fast these tires roll.

for the Fork, I am at 75psi, and a few clicks faster/firmer from center on Rebound and dampening. YMMV. For the climb up, I leave it in the mid setting and that works great, for the traverse and down, full open. I rode a couple miles with the fork locked on rocky and root-filled trails to see how it would ride rigid and although its doable for certain, the 130 in the Open position is so much nicer and keeps the bike much more composed and controllable. it also keeps the rear a little quieter. I still dont really miss the rear shock, the 3.0's at low PSI do a great job of soaking up terrain. I adjusted my riding position slightly; on sections with a lot of roots, especially in quick succession, I now let my butt just make contact with the saddle to help keep the rear of the bike from bouncing at speed. (I used to stay completely off the saddle) this works well unless its steep and I need to be behind the saddle. The 130 is really nice too. I am nearly bottoming on several runs on the way back down so having that extra travel allows the fork to work in its sweet spot. I dont ever feel its overkill. Most people use a 120 which is fine but I wouldn't change my 130.

Climbing is crazy good on this bike and even on really steep sections, I figured out that if you spin up a bit just before entering the switchback, the bike really maintains its inertia well. Theres a couple really steep tight switchbacks on the trails behind my house on Emerald that were a real challenge with the Yeti but they are noticeably easier with this bike. Descending through Switchbacks is a blast, The balance of this bike is different, more than likely its the less steep head angle so you dont need to be on the front wheel with as much weight to get to bite. It makes for less body shifting through the turn. the steeper HA also is quicker despite the mass.
 
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