Best XC mountain bike wheel size, 26, 27.5, or 29″ for Racing

What is the best XC / Cross Country Bicycle wheel size, 26″, 27.5″, or 29″?

These days wheel size is on the minds of most cross country bike racers. For instance most riders want to know what the future of the 26″ mountain bike wheel will be, and then secondly what is the best wheel size to upgrade to, 27.5″ vs. the 29″ mountain bike wheels.

Another very important question rider’s have is, can I upgrade my current XC mountain bike set up to the 27.5″ XC MTB wheelset (sometimes referred to as the 650B mountain bike wheel size) or even to the larger 29″ mtb wheel size?

Ok, let’s begin with the future of the 26″ wheel. If you currently own one or more trusty cross country bicycle steeds with the 26″ mountain bicycle wheel size, you are probably wondering if you should sell these cross country MTB bikes while you can, or hold onto them because you have so much invested in them vs. the return you will get from selling them, plus you may be very attached to them.

Tire manufactures (and XC mountain bike wheel manufactures as well) have made the bold claim this tire size will still be around and supported. After all, consider how many bikes have the 26″ mountain bicycle tire size.

That sounds great on paper and is a great press release, but we believe in the not to near future, the amount of premium tires, especially competitive XC MTB race grade mountain bike tires will slowly diminish, thus making it much more difficult to be competitive on this older wheel size. It could be 3 years, 5 years or even 10 years, but this is certainly the future of the 26″ wheel.

If you have been riding for some time you can remember how long it took for quality UST tires to become both readily available and semi-affordable in the 26″ XC wheel size. Thus as the 27.5″ and 29″ XC bike tires become more prevalent the future of the 26″ size seems dismal.

Many riders are really taking a bath as well selling their very expensive bikes, thanks to they hype of the larger tire sizes. Even the retailers themselves are dumping the 26″ bikes at super low prices, which is certainly a sign of what the future holds for the 26″ MTB cross country wheel size, right from the source.

While we are on this train of thought, we should quickly discuss if your current older 26″ XC mountain bike can be upgraded to either of the newer 27.5″ or 29″ mountain bike wheel sizes. There is a small chance the rear wheel might accept a 27.5″ upgrade, although it is unlikely or at least the possibility of experiencing some rubbing from the tire on the frame might occur under heavy riding conditions especially with modern larger profile tires.

The is a result of the fact that the mountain bicycle industry made a move to shorter chain stay designs some time ago. So unless you have a really old bike, chances are your shorter chain stay design won’t allow it. Of course if you have the bike in your possession you can measure the clearance. If you are considering purchasing a bike you want to upgrade, start with the geometry specs, and find out on the boards if any other riders pulled it off.

If you think you are able to make a rear 27.5″ MTB wheel upgrade, then the next discussion should be your front XC mountain bicycle suspension fork.

Will your mountain bicycle front fork support upgrading to one of the larger new wheel sizes, 27.5″ or even the 29″?

You may be able to swop the front XC 26″ wheel to a XC 27.5″ mountain bike wheel and tire assuming the tire does not rub on the top of the lowers fork crown. Measure carefully and consider the tires you run, because you don’t want to drop a bunch of money and then discover your tire is rubbing on your favorite trails.

If your fork is new enough you could even swop the lowers if need be. Remember the geometry might be a little off as well if you run your older 26″ cross country fork, with a newer 27.5″ XC mountain bike wheel. Most likely your head angle will become a little steeper. (i.e. – if you started at 70 degrees, you might end up at 71 degrees or steeper as 27.5″ fork lower is going to be slightly longer.)

What mountain bike wheel size is the right size for your size and riding style?

First, if you are new to the sport, there could be a great opportunity for you to purchase an older, used 26″ cross country mountain bicycle or a new blow out if any are still around for the same price or even less then and entry level newer 27.5″ or 29″ bike. For sure, riding a 26″ wheel is not going to suck any enjoyment out of your riding, and you may still be faster and more competent still than many of your friends who are running the larger wheel size.

For those who are want to upgrade to the XC 650B mountain bike wheel and tire, or the larger 29″ MTB wheel often referred to at a 29er, here are some of the things to consider:

Rider Size:

There are plenty of shorter both men and women at the professional level who run a 29″ wheel size, and of course being able to demo both sizes, would be very smart, or at least jumping on a friends bike makes great sense.

Generally the rule of the thumb is that 27.5″ XC mtb wheel corners a little better and is a little lighter, while the 29″ cross country mtb wheel is going to climb a little better and possibly even descend a little faster, but is more difficult to negotiate through really aggressive quick turning terrain.

Note – no one at the UCI DH Worldcup level runs the 29″ size, only the 27.5″ because it corners better, and there of course is no climbing, and the 29″ wheel is heavier.

On the UCI XC Worldcup level, riders are still split between the sizes. Most riders below 5’8″ (men and women) often ride better with the smaller 27.5″ (650B) cross country mountain bike wheel size, while taller rider often prefer the 29″ MTB wheel size. This is not set in stone, and the frame size you select combined with the geometry and the actual quality of the wheelset alone can make a big difference in your decision.

27.5″ & 29″ Mountain Bicycle Wheel / Rim / Hub Quality

If we are going to compare apples to apples, when it comes to making an intelligent decision on the right wheel size, remember that very poor built or a heavy wheelset might make one bike feel better then another, even if they are the same 29″ wheel size, or even if you are comparing apples to oranges and the bikes you are testing are the 27.5″ and the 29″ wheel size.

Thus it is important when testing to make sure the wheelsets and general part grouping are similar to get an accurate picture of the correct mountain bike wheel size that works for you. For more in depth information on wheel quality, read our article on Carbon XC Mountain Bike wheels vs. Aluminum cross country mountain bicycle wheels.

In closing, obviously getting some seat time on various bicycles with the two wheel tire sizes would be very helpful, but if this is not possible, consider the size rule as guide, and definitely search for comments and feedback from other riders who have the exact bicycle you want to purchase.

Some manufactures are already applying the size rule, and if want a small frame, or even medium, they might opt you into the 27.5 mountain bike wheel size, while the larger frames may already be set up as 29″ cross country mountain bike wheels and tires.

In the end, its all about having fun riding often, and purchasing the best mountain bike you can on your budget, and your intended use.

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