Wheel Size

Choosing a wheel size is one of the first decisions a bike buyer needs to make.

Road: For road bikes it’s pretty simple since they all come with 700c wheels. You could however convert your 700c road bike to a 650b road bike. Some come standard with 650b, but are pretty rare.

http://road.cc/content/feature/171905-650b-alternative-smaller-wheel-size-right-you

Gravel: More 650b bikes are available in this category compared to Road bikes.

Cyclocross, cross, or CX bikes: See Gravel above.

Street, urban, hybrid: bikes are almost all 700c but you can find a few in 650b.

Mountain bikes however is where an informed buyer will have to choose between 27.5 (650b) or a 29er (700c). I guess mountain bikers don’t like the metric system or something. For the first 30+ years of mountain bikes there was only one choice for wheel size – 26″. No one even discussed this. Around 2011 29ers became popular and in 2014 27.5″ wheels became popular since Giant went all in with this wheel size. The big 3, Giant, Specialized, and Trek have about 60% of the bike market. Giant is all in with 27.5″ though in 2018 have introduced more 29ers. Specialized is all in on 29ers but reluctantly have some 27.5″ mountain bikes. Trek has taken a different approach, a smart wheel sizing approach so the smallest frame sizes (xs and small) have the 27.5″ wheels and Medium through XL have 29ers. On some level, depending on what bike you want to buy, you may have limited options based on the bike companies philosophy. If you wanted to get a high end 27.5″ hard tail from Specialized, you can’t since none exist. If you want to get a high end full suspension 27.5″ Trek in a Medium-XL, you can’t since they up the wheel size to 29er in those sizes.

Here are the videos from these manufacturers about mountain bike wheel size. Keep in mind the bias that each company has.

Giant

This is a good write up, https://www.giant-bicycles.com/int/technology/detail/94 though Giant has (blah blah) 29ers (out of n mountain bikes). This page is impossible to find on their USA website so it seems they are backing away from their all in on 27.5

Specialized

 

Trek

So what should you get? I would recommend riding both sizes in equivalent bikes and see which one you like the best. The difference is significant and your height, what trails you ride on, and personal preference will significantly impact the decision.