Tire Size Shoot Out: 29×2.35 vs. 29×2.6 vs. 27.5×2.8

There was a time when we didn’t have a choice if we wanted wheels and tires on our bikes, they were 26” in diameter, and 2.1” in width.  We’re fortunate that the market has evolved to allow us the option of wheel and tire sizes to best suit our needs.  With this “Tire Size Shootout:29×2.35, 29×2.6, and 27.5×2.8” we wanted to better understand the strengths of the most popular sizes.

Here at Crankjoy, we have ridden all these tire sizes in the past like with Perspective Shift: 2.6″ and 2.8″ Tire Opinion.  We’ve never had the opportunity to ride them back to back, on the same day, and on the same bike though.  This shootout was performed with different tire sizes on a 27.5+ hardtail, in order to test ride them all on the same day and reflect on their differences.

Shootout Test Details

Leading up to the test, each wheel was ridden on a variety of trails to get pressures dialed, but the testing and report is based on a 3-mile loop in Harlow Lake Recreation Area just outside of Marquette, MI. The trails on the test loop are fairly fast and aside from a lot of embedded roots, not terribly technical.  The surface is fairly firm with some pockets of loose sand mixed in.  The loop was broken into three timed sections:

• 1.0 mile mellow descent that loses 250 feet of elevation. It has some roots but generally is pretty smooth with some corners thrown in.
• 0.8 mile flat and smooth two-track, slightly descends, losing 30 feet of elevation over 0.7 mi.
• 1.2 mile climb with 280’ of ascent.  The surface was mostly hard packed with a few patches of packed sand and some embedded roots.  The climb got progressively steeper and rootier as it neared the top. 

In order to minimize factors that could impact the results, all tires were run on the same day, on the same model wheels, and on the same bike.  

The test tire chosen was the Schwalbe Nobby Nic.  In my experience, it is a great all-around trail tire, it falls neither in the full XC nor the DH end of the tire spectrum.  Further, they are available with the same compound and construction for each size, with the exception of the 2.35” tire not having the APEX bead reinforcement added to the wider tires needed for cornering support at the lower pressures these tires allow.

ENVE Composites M6 rims were used, past experience has proven it to be a maintenance-free wheelset that tips the scales at XC weights.  Rim width was chosen for each tire size based on Schwalbe and ENVE recommendations.  

Before the test, each wheelset was ridden enough to establish appropriate tire pressures.  Pressures were set as low as possible to avoid squirm under high loads and to provide adequate bottom-out resistance when changing rock gardens at speed.  For reference, I’m 170lb geared up and ride fairly aggressively.

Tire and wheel dimensions and pressures.

The test bike was a Why S7, a Ti framed hardtail that handles like a trail bike, but has that wonderfully direct feel that comes with a hardtail.  The S7 was designed for 27.5+ tires, but with sliding dropouts and clearance for 3.0 width tires, it allowed for each size of tire to fit within the frame.  Further, it has a bottom bracket drop of 65mm, which is slightly lower than most designed to run 29” tires.  This meant with the  29×2.6” tires on the bike, the bottom bracket was still at a normal height.  To minimize variation between the test runs with different tire sizes, the dropouts were set to their midpoint (432mm chainstay length) to allow clearance for the 29×2.6” tire, and left there for the entire test.

Special attention was given to how the test laps were ordered.  The tires were run back to back and then run again in reverse order to better understand if the differences were normal variation or actual differences in tire performance.  Each wheelset was ridden at the same target power, for both the flat and climb segments.  However, the downhill segment was ridden by feel since power targets were difficult to maintain.  Heart rate was also measured for reference.  Ride characteristics were noted after each lap.

Test Results:

Ride Feel & Subjective Ratings: 

My favorite setup was 27.5+, it was the most forgiving of trail and surface irregularities, but it also was the most intuitive and flickable.  Impacts were dulled to a manageable level, allowing me to focus on having fun, rather than managing impacts. 

29×2.6 offered similar impact absorption to the 27.5 setup.  It did handle sharp transitions better than the other two sizes.  However, handling was quite a bit more cumbersome, and it felt like it added more heft than the 1/3 lb. indicated on the scale.  There’s promise for 29×2.6 and I’ve had great experiences with it in the past, but when ridden back to back, the 27.5+ was simply more fun, and it wasn’t any slower.  

29×2.35 was what you’d expect.  Sprightly & quick feeling, but the reduced bump absorption vs. the other two sizes on test detracted significantly from the experience.  This was apparent on both the front (130mm travel) and the rear of the bike.  Further, climbing didn’t FEEL any faster.  I found I had to work harder to maintain traction on the rough sections of the climb, as it was wet on the day of testing.  Despite the drawbacks, if my riding was limited to hammering out hot laps on a smooth XC loop, it may be my choice.  But if I needed anything more versatile, I would choose the 27.5+.

These results surprised me. 

In the past, I hadn’t liked the 27.5+ set up as much, I’d wager that the reduced weight and responsiveness of the high-end wheels and tires improved the ride experience compared to the relatively heavy wheelset I had run with 27.5+ prior.  Further, I’d really enjoyed the 29×2.6 tires coming into the test, but when ridden back to back with the others it offered little advantage at the expense of intuitive handling.  Read on for details.

Subjective Ratings:

Line Holding

The descent had a number sections of successive root impacts, some off-camber and wet.  The 27.5+ and 29 x 2.6” could be ridden straight through at full speed, with the 2.6 hinting at a slide.  However the 2.35 tires needed more attention, slight slowing and careful management of tire load to make it through.

Cornering Traction

Big tires for the win, both the 2.6 and the 2.8 excelled, they were just bulletproof and could be fully weighted through the corner.  When the 2.35 tires were weighted to maintain traction, they had a far lower threshold before pushing wide in the corner.  

Climbing Traction

It was a draw between the three sizes until I hit the roots, here the 2.8 and 2.6 showed a clear advantage, requiring less body language to stay hooked up.

Handling / Intuitiveness

This was the surprise of the test…27.5+ was the clear winner.  It allowed for easy mid-corner correction, ample traction, & minimal disturbance from trail chatter.  The 29x 2.6 tires were reluctant to accept a mid-corner correction, nearly sending me off the same corner on both test laps.  The 29×2.35 felt the most responsive, but relatively speaking, were disturbed by trail chatter, forcing me to focus more on managing bumps than cornering.

Acceleration

The order of ranking here is no surprise, as they are in order of weight.  The only surprise is how close the different sizes felt to each other when it came to outright acceleration.

Segment Times*

With limited resources and it was only possible to get 2 runs on each tire.  Any differences noted here won’t be statistically significant, but every effort was taken to minimize variability.  The power numbers & heart rate values were surprisingly close for each timed segment, and the test order should have minimized variability between runs due to fatigue and weather.

Descent Segment

The wider tires in the test felt faster, and they were, but the difference was small.  The 27.5×2.8 and the 29×2.6 were tied and came out slightly ahead of the 29×2.35” tires.  Power numbers omitted as they are not relevant for this descent.

Smooth Flat Trail

Interestingly, all sizes were within 2 seconds of each other.  It’s important to note though that I didn’t do a great job of matching power through this segment run to run.  The 29×2.35 time, although slowest, was posted using 6-8 fewer watts.  That may be significant, but to claim so would be a guess, I’ll let you be the judge, but I think it’s too close to call.

Climbing 

This is where the biggest difference in speed was, the 29×2.35 tires showed the fastest speed and the lowest power and heart rate.  Are 8 seconds significant?  Not statistically.  But even though it seems like a small difference that’s over a 100’ gap at the top of the climb.  It’s a difference I would love to have if racing at the elite level.

Overall Lap

There wasn’t much difference here, and since the power and heart rate numbers weren’t met I’d consider it a tie.

Closing Thoughts

Based on these results, I’m going to keep 27.5+ mounted.  They were just more fun than the other sizes, and the speed advantage to the 2.35 set was small enough that I’m willing to compromise in climbing speed for the superior ride feel.  

The 29×2.6 set offered similar composure to the 27.5+ over rough terrain, but it was resistant to mid-corner correction.  The 2.6 didn’t offer the fun, intuitive feel that the 27.5+ setup had.   Additionally, it did not present a noticeable or measurable decrease in rolling resistance. It wasn’t bad per se, but I didn’t feel that advantage was nearly enough to offset the better handling of the 27.5+ setup elsewhere. 

I’d choose the 29 x 2.35 for a dedicated XC race setup.  Despite similar overall lap times, XC and endurance races are won and lost on the flats and the climbs, and here is where the 29×2.35 showed and advantage. 

In this case, I may have come away with more questions than answers.  Would a mixed wheel size setup combine the best attributes of the 27.5+ and the 29×2.6? How would a dedicated 29×2.25” XC race tire compare to the speed champion (barely) of this test, the 29×2.35?  I intend to repeat this test to answer those questions once the snow melts.  Until then, happy trails.

We chose the Schwalbe Nobby Nic for this test not only because it’s offered in the same casing and rubber compound for all three sizes but because we love the tire too!  Here’s a recent review: The Speedy Trail Slayer: Schwalbe Nobby Nic 2.6″ Review