26" vs 29" vs 650 - bullshit or not?

I helped a friend out by fixing some derailleur issues they had, but it was the first time I’ve looked at a 29" up close (having kids has meant I haven’t been as up to date on bikes as I used to be when I worked in a shop).

My first impression was how big it is (an Avanti Aggressor 29.1 if you are interested), and even just riding it around the street in order to adjust the gears felt like I was on top of a penny farthing. My commuter (26" hardtail with rigid forks) felt like a wippet in comparison.

Even though I’m out of the loop, I can’t see what the fuss is. Lots of claims that it is easier to roll over obstacles (hmm) and give a bigger tyre contact patch, but with quite cheap entry level bikes available with good 80mm-120mm front suspension, I think this is a furphy. Also, just put on a wider tire for more contact.

If anyone can teach me physics, please do, but my understanding is rotational weight is much worse than static weight- you are always starting and stopping your wheels and drivetrain, so weight savings here are much better than weight savings in the frame or components for example. A 29" with a huge tyre is a lot heavier than a 26", and would flex more too. It needs a bigger frame, so you’re wheel base is longer, and weighs more (smaller chainrings though) - all adding up to be not as good.

Then there is the 650 (or 27.5") which looks more like marketing on top of the 29". Is this just a cynical way to get people with perfectly good bikes to buy something new? I found this bikeradar video which didn’t answer any questions:

Any 29" advocates comments appreciated.

Angle of attack is the best comparison, as far as rolling over obstacles.

My ipad isn’t cooperating, so I’ll work on a better response a little later. I’m totally pro 29" by the way. Been riding one for 6 years and haven’t looked back.

What’s your objective? If you need a bike to go a few miles back and forth to work, pick what you want, performance, going over obstacles and knobby tires are usually not objectives when going on a paved road. If your objective is something other than commuting, you will need to narrow it down before any recommendation is made.

I think their are several reasons for 650B over a 29er. The biggest being toe overlap. On small frames, if you have large wheels, either your toe will hit the front wheel when turning or you need a funky geometry that won’t fit the rest of your body.

As for marketing hype, yes, bike companies will do anything to get you to buy the latest and greatest. Is 11 speeds that much better than 10? But that can be said of any industry. Everyone wants you to turn it up to 11.

As for your concerns of heavier wheels or a stiffer frame. Money talks. If I spend enough, I can buy a 29 wheelset with tires that weighs less than a 650B. And I have yet to see a good peer-reviewed study that shows a correlation between a stiffer frame and an increase in performance Stiff frame=better is a huge part of bike companies wanting you to buy the latest and greatest.

Because its so hard to quantify, the acceleration bit gets lost in the wheel size discussion. 25 years in, I’m still a smaller wheel guy for technical riding- it’s easier to get smaller wheels to cooperate on the techy, natural trails that I prefer. That said, with the high end all but abandoning 26in, I don’t have any problem going to 650b as its only 4% larger (and closer to 26in wheel/tire combos than 29). It’s not enough to justify changing bikes for, but seeing where the industry is headed I won’t cling to 26in wheels when buying my next frame.

Of course, I’m off to 24 Hours in the Old Pueblo and for the first year I’ll be riding a geared 29er (a Felt Edict Nine with reasonably light 1,500g wheels). It’s a fast, rolling course that encourages keeping one’s speed up. That’s also the reason that I prefer 29er singlespeeds. We’ll see how the bigger (and heavier) wheels work when it comes time to squeeze passes in among the cacti- the only thing that has me concerned. I did the 7-day Trans-Sylvannia Epic (in PA) last year on a BMC 29er and was happy with it on the long, steady days on lumpy trails (but wasn’t doing a lot of passing given the format of the event and our pretty mellow team).

MTBR’s Angry Single Speeder did a nice comparison last year and theorized (after switching back and forth during the same event) that the faster wind-up gave him a passing (and thus lap time) edge. We’ll see.

Talking to BMC at Interbike last year about their decision to move their enduro bike to a 29in wheel (rather than 650b), it came down to the numbers. The less experienced the rider, the greater the gains from larger wheels. Once you get into advanced riders, thanks to skill level or simple time spent on smaller wheels, the time differences apparently fall into the noise. There’s also a level of confidence/unstopability imparted by larger wheels once they get up to speed- not necessarily a bad thing. At the end of the day, ride whatever you’re comfortable with. I personally prefer the feel of 26/27in wheels, so will likely stick with them for everything but smooth trails or marathon-type events.

As far as XX1/XO1 1x11 drivetrains go, the cassette and derailleur prices are bonkers- but it’s really, really hard to go back to the noise and weight of a 2x or 3x drivetrain. Don’t try it unless you want to buy it. (But that’s another topic.)

I saw it in the other topic, very nice.

$400 for a rear cassette! Holy Moly!

In that video the Storck guy talks about rider heights, that 650 stop at 185cm and 29" from then on. Seems like a smart idea.

I meant stiffer wheels, but I do believe in stiffer frames. Years ago I built a set of mammoth rims with 13g spokes (maybe 12g, can’t remember, but they were stupidly fat), and was so surprised how much better they turned, even though they weighed a ton. Logic would suggest that any technology used to make a 29" light would make a 650 lighter. My physics understanding of a stiffer frame is that I want my pedalling energy to go into turning the rear wheel, not flexing the frame.

I’ve ridden the same trail on all three wheel sizes - though not on the same day, and with pretty different bikes ranging from 26" all mountain (mine) to 27.5 all mountain (Santa Cruz Bronson in carbon/XTR, sick) to 29" hardtail (Niner RDO full XTR).

Being 5’5" and mostly torso I don’t see myself ever riding a full suspension 29", or even something with more than 100mm of front squish. The front end gets too high and you have to do funky stuff with your stem. That all said the bike RAILED berms; I’m guessing I felt the angular momentum effect, the stability of the wheels when leaned over. It climbed like a rocket but that’s because of the stiff light carbon and the XTR build.

The Bronson in 27.5 was a little harder to quantify, since there’s the VPP to deal with. It wasn’t as tricksy as a 26", like it didn’t like getting airborne, compared to a 26". I guess I didn’t perceive the wheel size to be that much of a difference. Was hard to separate it from the bike suspension and build too.

I plan to stick with 26" for as long as companies keep making them…which might not be much longer. My 26" Yeti SB66c won’t be made for 2014, they are going exclusively 27.5 and 29. There’s enough marketing BS momentum behind the 27.5 movement that it won’t go away and the industry can keep calling it the next big thing.

Oh and fat bikes and gravel grinders too.

What’s next?!@? Hubless tubeless spokeless and airless 27.5 mountain bike wheels? :unamused:

I bought a new 29" low entry cross country mountain bike mid last year and was very impressed with it. Regardless of the wheel size entry level bikes always have crap suspension and I reckon the big wheels actually made a huge difference in its smoothness out on the trails as well as commuting. Its the other wheel sizes actually look odd to me now.

Just to expand on Nurbs link, this justification by Giant for 27.5" (Who I think mostly missed the 29" phase) I thought was interesting http://www.giant-bicycles.com/en-au/globalstartpage/giant-27-5/#technology

While I don’t think I would notice any real difference between a 27.5" from a 26" wheel, because of the popularity and success of the new wheel sizes, if a manufacturer now doesn’t change to at least one of them then they will struggle to stay relevant.

That’s pretty interesting, coming from BMC, about less experienced riders having more to gain from a bigger wheel. That’s been what I’ve seen, especially with roadie converts. The 29" wheel is maybe more familiar, like a 700c, and they’re probably hardtails so it feels more efficient to them. Being less experienced they are almost certainly riding less technical trails, so their bigger wheels aren’t disadvantaged by tighter or steeper terrain. All that said, the Specialized Enduro 29, the Tallboy, the new Ibis, SB95, all seem to be very capable bikes in tougher trails. Where I ride (Pacific Northwest, the wet side) its predominantly 26", 5 to 6" travel, grind up and bomb down…maybe not the best environment for larger wheels.

Less expensive alternative is a Wolf Tooth or Race Face narrow-wide chainring, and a max 36t cassette with clutch derailleur in the rear. There are kits to get you a 42t max cog as well…all for much less than XX1. But yeah I hear its pretty awesome and that XX1 cassette is a work of industrial art.

You guys have made some great points, so I won’t elaborate too much on my view.

How tall are you Jaime? I’m 6’4" (193cm) so I’ve always had big bikes. I always felt on a 26" bike that I was going to go over the bars when I stood up on it. I don’t have that feeling on a 29er. I ride a Surly Karate Monkey which is by no means the lightest or fastest bike out there. But, it’s durable and versatile (I put 700x35 Nokian studded tires on it for ice, and 700 x 45 for commuting, and 29x2.2 for trails.)

I live in the Midwest, so I don’t have the advantage or necessity for 6" of travel on both ends of my bike. I can roll over anything and carve through berms and doubletrack through grassy meadows faster than most on a 26".

I love it. I switched years ago and I’m not looking back.

[soapbox] Again, I have never seen any peer-reviewed anything correlating stiffness (of anything) and improved performance. I am happy to read any evidence that’s states otherwise, but I don’t know of its existence. Go to any wheel or frame manufacturer website. Under their aero section, they will have all sorts of numbers showing the decrease in wind resistance will decrease wattage by x amount. In their stiffness sections, they will have their stiffness rating but never any corresponding savings in wattage. Occasionally some student at a university will publish a paper and I have read a few, but none I have read to date will show anything of significance.

With wheels, obviously if you are flexing enough to rub your brake blocks, you will decrease performance. Disc brakes eliminate that problem and if you are running calipers, let them out a bit. I have a set of wood rims (road bike) that even with a 36 3x are like noodles, especially on a climb. But with no brake rub, I’m not going up that hill any faster than with my aero carbon rims that are incredibly stiff with 20 radial on front and 24 2x on the back.

If you look at the physics, if there is any flex, it is a closed system, it will flex back and the only energy loss is through either heat or noise. If your BB is red hot, you may have a point, otherwise any energy loss due to flex is insignificant. All you need is a different pedaling style for a noodle over a stiff bike.

I will fully concede that your perception will most definitely affect performance. If you like riding a stiff bike over a noodle, you will be faster on the stiff bike, there is no doubt about that. If your pedaling style suits a stiff bike, you should ride a stiff bike. That is user preference. But your stiff frame and wheels still can get beaten by the guy who prefers the noodle, they just use a different technique. Sean Kelly is the perfect example. His Vitus tubing was a complete noodle compared to the SL, SLX, 531 and 753 used by his competitors yet he was able to crush them in a sprint. [/soapbox]

All this talk makes me want a new bike!

I’m just 6 foot (183cm) but I’ve run the smallest frames possible on a mountain bike with long seat posts and long (sometimes high) stems, so I’m used to lots of standover height. My friends 29" was way too big for her and she’s 5’5", and felt too big for me. I’m coming around to the angle of attack idea, and also its a smart way to get roadies used to 700C over to MTBs (I believe the erto size is exactly the same, 622mm, for 29" and 700C). If anything the 650/27.5" seems to be the marketing rubbish. I remember late 90’s some local guys were talking about running downhillers with 20" BMX wheels, so they could have super bombproof rims and ridiculous amounts of travel.

The bike world (especially magazines) is full of pseudo-science and marketing nonsense muddying the waters, which I have been sucked into more than once. I happily concede my understanding to someone who knows what they are talking about.

622 is correct. My wheels are actually cyclocross rims. Options abound…