Mountain bike wheel sizes: 26in, 650b and 29in explained

How to choose the right wheel size for you

It used to be so simple. Mountain bikes had 26in wheels and that was that. It had been that way since 26in wheeled beach cruiser bikes were first raced down Californian mountains and, apart from occasional experiments, it stayed that way for more than years.

Then development dynamo and marketing genius Gary Fisher started pushing 29erwheels on his bikes. Fisher certainly wasn’t the first convert but he was backed by the massive manufacturing, ordering and selling power of Trek Bicycles. As the initial handling and equipment issues were gradually sorted out 29ers gained momentum and more and more brands eventually jumped on the ‘wagon wheel’ bandwagon.

29in wheels aren't great for everything though, and with the 26in stranglehold broken, other innovators revived the intermediate 650b (aka 27.5in) wheel size in a mountain bike format that potentially promised the best of both worlds.

Eager to repeat the new bike sales surge created by 29er wheels, fast-reacting companies jumped on the new 650b size. The new bikes look better, handle better, fit more people and more riding styles and, almost overnight, 650b is pushing 26in wheels to the brink of extinction.

But what are the real differences in how wheel sizes ride and which one is the best for you?

26in

The original wheel size might have been an accidental standard based on beach cruisers, but it still has a lot going for it.

For a start, smaller diameter rims and shorter spokes mean 26in wheels can be made lighter and more responsive than other sizes. That means a more agile feeling, faster accelerating bike on smooth surfaces.

They can also be made stiffer and stronger too, which is why most top downhill riders are still sticking with 26in wheels.

Spares are much easier to find than 29in and far far more common than 650b replacements. That makes it much easier to get going again if you puncture a tube, tear a tyre or crumple a wheel far from home. That’s obviously another bonus for downillers and jump bike riders, who are the most likely to destroy their gear. Lots of shops are already selling 26in frames and components cheap too, so there are tons of upgrade bargains about.

Because they hit stuff at a steeper angle and drop into holes easier they clatter and lose speed more rapidly than bigger wheels in the rough though. They’re not as stable steering or as grippy as 650B or 29er formats of the same tyres either.

  • Can be made lighter, stiffer and stronger than other sizes
  • Loads of existing 26in wheels, tyres, forks and bikes makes spares cheap and easy to find
  • Feels lumpier and stalls easier than bigger wheels on rough terrain

650b / 27.5in

29ers certainly made it easier for the MTB industry to introduce a third wheel size, but we’re still shocked how fast 650B has been accepted.

The first thing to realise is that the wheels aren’t actually 27.5in but closer to 27in. As a result they’re significantly faster to accelerate and easier to flick around than a bigger 29er wheel.

There’s less steering inertia and flex in the handling too, so handling feels more responsive and balanced. The wheels are still small enough to work with long travel suspension frames and forks without them feeling or looking weird.

650B tyres still roll over rough ground more smoothly and grip noticeably better than 26in equivalents, although not as well as 29in wheels.

Because the new wheel size has been introduced so suddenly, most manufacturers are struggling to make enough bits for complete bikes, let alone extras for shop stocks. That means spares are a lot harder to find in a hurry so stocking up in advance is wise. As supplies are tight don’t expect to get bits cheap either. Most manufacturers are still concentrating their 650B efforts on ‘trail’ and ‘enduro' bikes too, so specialist cross-country and downhill machines are thin on the ground.

  • Faster accelerating, stronger, stiffer and more agile than 29in but noticeably smoother than 26in
  • Handling and wheel placement feels a lot more natural than 29er wheels
  • Spare tubes, tyres, wheels and other stuff are still really hard to find in a lot of shops

29in

The wheel that broke the stranglehold of 26in produces a very different feel. Because 29er wheels are larger, they’re generally heavier and harder to get moving.

Their size and stability also means it’s taken a while for bike designers to make big wheeled bikes handle in a fun way. They’re still harder to hustle on really tight twisty or jump and pump trails compared to smaller wheels. It’s also more difficult to make big wheels and small frames or long travel suspension fit together too. Crucially, because they’re not as quick to get going and their smoothness dulls the sensation of speed they often feel much slower than they actually are. Add sometimes awkward looks and it’s easy to see why 29ers took a while to catch on.

Once rolling though 29er tyres hit rocks and roots at a shallower angle and with more momentum so they roll over the top easier. The longer contact patch means any given tyre grips better or you can run slicker, speedier rubber without slipping. Add their natural extra stability and they’re perfect for powering straight through trouble at high speed.

There’s a full range of different styles of 29er bikes to choose from now too, although most are still focused on the cross-country and trail categories.

  • Smoother, grippier and more stable for better control on rough terrain
  • Slower to get moving but hold their speed better once rolling
  • Feel awkward on tighter, slower trails and harder to sync with long suspension or short riders

How to choose the right wheel size for you

So where do you fit into this three ring circus and which diameter is dialled for your riding?

The biggest question right now is whether it’s worth buying a new 26in wheeled bike. The short answer is only if you desperately need a new downhill bike. The smallest wheel size is still the strongest where strength matters most and while several companies are experimenting with 650b downhill bikes and gear they’re still mostly at prototype stage.

You’ll also struggle to find 650b or 29er bikes for really budget prices too, although that might change when 2015 bikes are released.

So is 29er doomed to disappear soon too? Not if you’re either just starting out or want to finish first. Cross-country riders are definitely going to stick with bigger wheels simply because they’re faster on less technical, high speed race courses and open trails. As they roll over stuff smoother with better grip and stability they also make a lot of sense for less confident or novice riders. They also reduce the arse-kicking issues of hard tail bikes which again ties in with both cross-country race and novice users.  

Otherwise 650B is definitely where all the current frame, fork, wheel and tyre development is now focused for trail and enduro bikes plus an increasing number of cross-country machines. As they’re often totally fresh designs you get the latest performance boosting technologies as standard. The resulting blend of agility and smoothness really does seem to offer the best of both worlds to the widest range of riders, particularly those after maximum fun and versatility from their MTBs.

So while it might cause confusion at first, by letting you ride faster, safer and further to cram more fun potential into every meter of trail, reinventing the wheel has turned out to be a really good idea.

Guy Kesteven
Author: Guy Kesteven

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