The trails where I live are very hilly and so I end up doing a lot of downhill as well as a lot of uphill riding. I’ve tried a number of different configurations of my two munis now and what I’ve found to be the best from a pure climbing perspective so far is a 24" wheel, 2.8" Big Roller tire and 148mm cranks. I also tried 150mm cranks and any difference was imperceptible. The same setup except with a Duro Wildlife is also quite good. The Wildlife gets better traction in the sloppy stuff and climbs better in the mud, but otherwise I think the extra weight makes it just a slightly weaker climber overall.
My 27.5 with a 3.25" Duro Crux and 170mm cranks climbs really well so long as I can keep it balanced and navigate the correct line. With those long cranks it can keep going up some very steep terrain, sometimes to the point of losing traction. The problem is trying to keep it upright and on the right line while pushing them. When I can do that I give it the edge over the 24"/148mm combo as I can simply outpower the 24". The 24" however is more nimble and because of that on average it climbs better.
The 27.5 with 145mm or 137mm cranks is awful in comparison with the 24". The torque simply isn’t there to keep it going uphill much past a 25% grade. Some months ago, I felt it climbed better with the 145’s, but now I realize that was just the limits of my ability at the time. I did not have the control then to make use of the 170s torque and to keep my balance on those very slow steep climbs.
I’ve tried the 27.5 with a High Roller 2 as well, but I had camber issues with it and I never really paid much attention to its relative climbing ability as I hated riding it.
One other thing I think that gives the 24" the edge is a lower center of gravity. I might put some 170’s on it just as a climbing experiment, but I don’t think I’d want them full time. There are a few hills I’ve been attempting to climb for months now without success and it would be cool to finally conquer them.
That’s my experience so far anyway. I’m curious as to what others experiences have been.
For me, this is a wonderfully helpful post!
I have a 27.5+ Oracle with the 3.25” Duro Crux and 150/125/100 cranks. I wrestled with the decision of that crank setup vs the 170/142/114 cranks.
I have a 24” Koxx White Russian with 130mm cranks, a 24” Schwinn with 150mm cranks, and a Koxx Track Monster with 165mm cranks.
So far, I’m most comfortable climbing with the 24” with 165mm cranks, but my “climbing” in Texas probably seems flat compared to your climbing. I need to seek out steeper sections to specifically work on climbing.
Thank you for the detailed analysis. I hadn’t compared tires to see if that makes a difference, but since I haven’t yet encountered anything steep enough to lose traction I figure my tires might not make a difference (yet) anyway.
I’ve forced myself to learn and do all of my advanced riding on my KH29" with a 3" Maxxis Minion DHR and now the 3 1/4" Duro Crux and 127mm cranks is my setup.
The 127’s keep me from spinning out when it turns into a stair climber.
Some loops that had certain uphills have taken me years to be able to ride them without dabbing.
A zero dab ride is my goal. (no dismount for any reason)
I think fine slow and standstill riding are half of my success and I think conditioning is the other half.
This is just what works for me.
All of this it moot as now I’m waiting for my new knee. While that happens I can’t push the envelope for riding (can’t fall hard) so I keep my cranks set at 150mm for absolute control.
(edited to fix old man moment… I don’t even have 137mm cranks, my cranks are 127mm)
The trails I have aren’t much and I can do them just fine on a 24x1.95 tire or a 29x2.5 and on all my unis I have 125mm cranks so that’s never a variable for me. The 29 is faster than the 24 so I use it more often but I think on the uphills it’s about a wash as I’m mashing the 29 or just slowly plodding along the 24.
I’ve found that for long grinding climbs around obstacles where you are forced to stop between pedal strokes, longer cranks work better because the extra leverage helps you get around past the sticking point.
For short steep climbs I like shorter cranks because they make it easier to spin good circles and keep the momentum going.
If you’re trying to be absolutely optimal, I think you’ll want different setups for different kinds of climbs.
I plan on continuing experimenting. I need to get more time in with the 27.5 and I want to try it with higher tire pressure. One of my biggest problems climbing with it has been autosteer. It’s not that noticeable on flat ground or downhills, but when I’m climbing I find I just can’t always make the corrections I need to to keep my balance.
I plan on putting 170s on the 24" also and trying that, but I don’t think it’s a setup I would want to ride much with as it would be awfully slow and prone to pedal strikes.
I’m somewhat dubious about speed gains to be made by using shorter cranks. Partly it’s obvious that your feet can make a smaller circle faster than a large one and I accept that, but how much faster? I don’t think that’s a linear function. I doubt there’s an actual 16.66% speed gain when you switch from 150mm to 125mm cranks. The change in torque should however be a more linear function as that’s just a matter of how much force you can apply and how long your lever is.
I feel my knees come up too much on 148/150’s.
What i’ve found is 138mm Nimbus 29er muni - easy to mount, pretty good experience to ride.
117mm Nimbus 29er road - it’s much harder to static mount. Balance point feels a lot smaller. I’m thinking of putting that uni back to 125’s.
Well, I’m going to give up on the 27.5 with 170s. I’d heard some noise while climbing earlier, but I wasn’t sure what was causing it. Now I know it’s the tire rubbing on the frame while under load. My wheel is pretty darn close to true, with about 1mm of wobble in it and the rubbing seems to be happening on both sides. It seems that the combination of a big tire, long cranks, a heavy rider and a handle saddle are just more than the frame can deal with.
You have done a lot of great research. Another possibility is to upgrade your wheels, tires and tubes by making them light as possible. Some things I have done are change my aluminum rims out to carbon ones bought at Light Bicycle. Change my tires to the extremely light WTB Ranger 2.8. And put in light weight tubes. That allows me to run shorter cranks while climbing and gives me the best of both worlds.
What are your before and after weights? And what wheel size are we talking about?
Unfortunately I don’t have an adequate scale to document the weight savings when I upgraded my rims to carbon with lightweight tires and tubes. But the climbing performance gain was astounding! It’s amazing the difference shaving just 250 grams can make……The wheels I upgraded are 26” with 137 cranks and 27.5 with 145 cranks. Both frames are aluminum.