How to Convert Your 29er to a 27.5+ All-Trail Bike

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If you’ve ridden a fat bike or even a “plus size” bike, you already know what a huge improvement bigger tires can make. If you haven’t given fat or plus-size riding a try yet, here’s what you’re missing:

  • Better handling through technical terrain.
  • The ability to make your own trail.
  • More fun.

Sure, there are tradeoffs (like increased rolling resistance), but after riding nearly a dozen fat and plus-size bikes I can tell you the tradeoffs are more than worth it. I badly want to make a full suspension fat bike my primary rig but alas, my “new bike budget” is limited at the moment. But it turns out there’s a solution: the 29er to 27.5+ conversion!

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I’ve been riding my converted 27.5+ Santa Cruz Tallboy for several weeks now, and I love it. It’s a full suspension big tire bike that checks pretty much all the boxes for me, and I don’t foresee going back to regular 29er wheels anytime soon. Of course there are a lot of considerations before making this type of conversion, so I thought I’d answer some of the common questions here.

“Is there a way to make this work for MY 29er?”

Probably. I used the WTB Scraper rims to build up my 27.5+ wheels, and they’re a great choice because they’re much narrower than fat bike rims and even most standard plus-size rims. Clearance top-to-bottom is rarely an issue for 29er conversions since the outer diameter of a 27.5+ tire is roughly the same as or smaller than a standard 29er tire. Side-to-side clearance is the real limiting factor, though I can almost guarantee these 45mm rims will clear your frame and fork–but tires are another matter.

The mountain bike industry seems to have settled on 3 inches as “plus-size” when it comes to tires, and right now you can find 27.5+ tires between 2.8 and 3.25 inches wide. If you want to be safe, start with a 2.8-inch tire and if you have room left, go bigger. With my fork I could probably go with a 3.0 tire but in the rear 2.8 inches is about as tight as I’m willing to go.

“Will this affect my bike’s geometry?”

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A little. With the Scraper rims and WTB Trailblazer 2.8 tires I found my bottom bracket was lowered about a quarter to half an inch. That doesn’t sound like a lot, but if you’ve been riding your 29er for a long time, you’ll notice. I find myself bashing pedals on rocks and roots more frequently, though nothing more than glancing nicks so far. The upshot is a lower center of gravity, which can actually improve cornering and overall bike handling.

“What do I need to buy to make this happen?”

The good news is you just need a 27.5+ tire and a wide-ish 27.5 rim. You can use standard hubs to build up the wheels, though you won’t be able to reuse your 29er spokes. I don’t know of any complete 27.5+ wheelsets that are meant for conversions on the market at the moment, but keep your eyes peeled. In the meantime, you’ll need to build up a set of custom wheels (your local shop should be able to help with this).

Note the muddy scrape marks on the tire.
Note the muddy scrape marks on the tire.

The great thing about this “conversion” is that you can easily switch back to your 29er wheels whenever you like. Slap on a set of 27.5+ wheels for bikepacking but keep your 29er hoops for racing.

Check out these in-depth reviews of the WTB Scraper rims and the Trailblazer 2.8 tires. I also reviewed a set of 27.5+ tires from VEE Tire Co., though sadly they didn’t fit my 29er frame.

“What kind of tubes can I use?”

Tubes designed specifically for 27.5+ tires are as rare as unicorn teeth at the moment, but not to worry! The Scraper rims are tubeless-ready and I haven’t had a single burp or flat during my tests. When I do get a flat, my plan is to use a 29er tube. Sure, it won’t be perfect, but should get me home. Some have also suggested looking for thicker DH-specific 27.5 tubes… but these can be heavy.

“How different is the ride quality with a 2.8-inch tire vs. a 2.35-inch 29er tire?”

For me, the ride quality is very different. I’d love to be able to go wider to get the same ride feel as say, a 4″ Salsa Bucksaw, but 2.8 inches still gives me improved technical handling and off-trail maneuverability and confidence.

“Does the 27.5+ wheel feel too small?”

I’m a tall guy (about 6′ 3″) and 29er wheels fit me like Michael Jackson’s glove. The 27.5+ wheels do feel a little slower, but overall the bike also feels more maneuverable–just as you would expect. I won’t be converting to 27.5 anytime soon, but 27.5+ is close enough to 29er for me.

“How much will this cost?”

At the moment, building up a set of 27.5+ wheels isn’t cheap. Plan to spend around $700 for a basic set, though that does include labor. You could get away cheaper if you do the labor yourself… or way higher if you choose blingy hubs and lightweight spokes.

Building up a set of 27.5+ wheels is a great way to turn your 29er into a dual-use rig ready to handle everything from XC racing to adventure riding to fast, technical descending. Have you converted your 29er to a 27.5+ rig? We’d love to see your photos!

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