29" wheels on the ultra eagle?


Active Member
I have the Ultra eagle and I could have sworn on the Biktrix website they gave the option to purchase a 29" wheelset during checkout but I don't see it anymore. Does anybody know if I can put 29" wheels on this? And if Biktrix discontinued them which ones should I get?

What would be the advantages and disadvantages of going to 29"? I will be going faster right? I have had a 26" fat tire for almost 2 years now and the 27.5" 3.0 wheels on the was my first experience with wheels of this size and I really like the bigger wheels. Whenever I get on my 26" now I feel low (maybe it's just in my head) and so I'm wondering if I like the 27.5 that maybe I will like 29".

I ride on the street and go off road through trails, there's a lot of hills in Colorado if that makes any difference. Will bigger wheels help me get more distance out of my battery? If I have a bigger wheel does the bike go farther for every pedal revolution? If that makes any sense.



Well-Known Member
Buying Guide - 26" VS 27.5" / 650b VS 29er

26" Advantages
• Tend to weigh less than 27.5" & 29er bikes, as their smaller wheels and forks save weight
• Smaller wheels are often better for technical terrain that requires fast reaction time, such as quick twitchy trails
• Fits all size riders very well; whereas larger bikes such as 29ers are often difficult for smaller riders to fit onto
• Quick off the line acceleration
• Increased lateral strength for riders who require high travel DH / FR bikes
26" Disadvantages
• Less forgiving while going over bumps, roots, rocks, ect....
• Slower top end speed than bikes with larger wheels
• Smaller wheels require added suspension to soak up terrain. This can lead to decreased efficiency in the suspension by adding pedal bob to the bike.
• Smaller tire footprint than bikes with larger wheels often means less traction
• Requires a higher tire pressure than larger wheels

27.5" Advantages
• Provides a higher top speed than 26" bikes while having faster quick reaction times than 29er bikes. This is the main advantage of a 27.5" bike, as it's goal is to utilize the advantages of both 26" & 29er bikes
• More forgiving than 26" bikes
• Larger wheels mean less suspension needed, which increases overall bike efficiency
• Higher top speed when compared to 26" bikes
• Good off the line acceleration than 29ers
• Better traction than a 26" bike
• Good alternative for small riders who want a larger wheel bike, but don't fit comfortably onto a 29er
27.5" Disadvantages
• While more forgiving than 26" bikes, these bikes are still less forgiving than 29er's
• Slower top speed when compared to 29ers, even though they're faster than 26" bikes.
• Slower off the line acceleration when compared to 26" bikes
• While having better traction than a 26" bike, 29er's still have better overall traction because of their large wheel size

29er Advantages
• Faster top end speed
• Larger wheels are much more forgiving than smaller wheels when going over roots, rocks, ect.... Picture the difference between a full size truck and a Honda Civic going over the same pothole. The pothole would hardly be felt in the truck, where as it'd probably feel like it was swallowing up your Civic because of the difference in wheel sizes
• Larger wheels mean you need less suspension travel to soak up terrain, which generally leads to less pedal bob and increased efficiency.
• Great for taller riders
• Larger tire footprint on the ground at all times means increased traction, which is great for climbing & descending
• Because of increased traction, the ability to confidently ride over more aggressive terrain without avoiding obstacles which you might with a 26" bike and overall increased bicycle stability, the 29er will make you a much more confident rider
• More efficient on longer rides
• Can be run with lower tire pressure, if you so choose, than smaller wheels, allowing for a smoother more comfortable ride
• Increased rotational weight
29er Disadvantages
• The larger wheels make these bikes slower to react quickly to fast twitchy trails; however where you may have simply avoided obstacles in the past on your 26" bike, you may simply find yourself rolling right over them with the larger 29er wheels
• Generally harder for smaller riders to fit onto
• Larger wheels, fork and frame tend to add a slight amount of weight to the overall build
• Slower off the line acceleration
• Generally not suited for DH / FR riders


Active Member
Appreciate that! It looks like it could be a good fit for me then I don't do any technical off-roading or mountain biking. I only go off road to take a shortcut to where I'm going. I'm wondering what the turns would be like though. I'm 5'9 and I have a medium frame so it sounds like I should be fine as for it being more difficult to get into for smaller riders. The eagle also has a dropper seat post. My only other concern would be the slower off the line acceleration but I don't have to worry about that with the ultra motor. It already wheelies in too low of a gear off the line with 27.5. The roads are definitely rough here, I like that the bigger wheels will soak up the terrain more. I don't have any issues climbing but it's pretty sweet that it helps with that and traction. Maybe if it's less stress on the battery/motor to climb I can get more life out of my battery. I really wish I could put a 21ah on this bike but it won't fit.

Can anybody recommend some good 29" wheels for the Eagle? Does it matter or any well reviewed 29" wheels would work? I have no idea about wheel brands etc and want to make sure they are good one.


Well-Known Member
The larger wheels will hurt climbing ability as they'll result in a higher effective gear.

But, I'm not sure the differences are that big. I'm going to hazard a guess that you're not going to see that big a difference going from 27.5" to 29ers. One thing to check out is this Gear Calculator. You can run it with your bike's gearing and then change the wheel size to see how your cadence would need to change to achieve the same speeds. You can also run some calcs to see how much larger the rolling diameter is. If you were coming from 26" I'd say Go for it, but 27.5" wheels are already a great middle size.

The Ultra Eagle is currently sold as a 27.5" Boost configuration, with a 12mm through axle rear and a 15mm axle front. Biktrix's website implies a 110mm front length and 140mm rear, but I'd double check the markings on your existing axles to be sure, as my 27.5" Boost bike has 120mm front and 150mm rear spacing. I'd also double-check with Biktrix that the 29ers will fit - it could be they made some frame geometry changes recently that preclude the larger wheels.

The other thing to think about is whether you're happy with the 11-50 gear range or whether you'd want to upgrade to the 10-50 range. To get the 10-50 range you'll need to get a rear hub with an SRAM XD driver (yours has the normal splined driver) and then a new rear cassette. You can keep your SRAM derailleur and shifter.

Finally, you'll need to choose wheels with a rim width that's compatible with the tire widths you want to run.


Active Member
I will probably wait on it then but, in the advantages for 29.5" in your post says it does help with climbing but, you're saying it doesn't so I'm a bit confused.

"Larger tire footprint on the ground at all times means increased traction, which is great for climbing & descending"

I guess I figured if going from 26" to 27.5" makes a difference it's 1.5" difference so going from 27.5" to 29" is another 1.5" so I thought it would be just as much difference going from 26" to 27.5".

I was considering to go to a 10-42t Sram CS-XG-1175-A1 but I am a bit confused about the "splined hub" issue and don't want to mess anything up and get a cassette that can't handle the motor etc. I'm not too sure what exactly I need. Which rear hub and 10-50t cassette would you recommend?
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Well-Known Member
My understanding is that the footprint isn't larger, just oriented differently. Weight and tire pressure are the primary factors for tire footprint size.

While it's the same 1.5" from 27.5 to 29 as from 26 to 27.5, as a percentage, it's a bit smaller. I guess the real question is: What are you experiencing that makes you think of spending money to get larger wheels?

As for cassettes, you already have an 11-50 set, so I wouldn't go to a 10-42 unless you find you never need the low gears you have today - especially if you're going for a larger wheelset you'll find you'll be at least in one lower gear than previous for the same cadence-speed relationship. The larger wheels will make each gear feel "taller" anyway, so maybe you won't need to go to a 10 tooth top gear. How often, if ever, do you wish you had a taller top gear today?


Active Member
Not experiencing anything in particular maybe wanting to go faster with bigger wheels, and that I liked feeling higher up on the 27.5 compared to my 26" and figured that maybe I would like the 29" even more. If it was more efficient and able to help me run longer on my battery would be nice but not sure how realistic that would actually be. I'm not totally set on this, was just something that crossed my mind.

I do need low gears because there's a lot of hills here but I already am not able to go too low in gears because I will wheelie from the torque but since I'm used to the 11-50t now maybe it would be better to stick to 10-50t but I'm confused on exactly which parts I would need and about the compatibility with the ultra eagle.

I don't even have any idea what a "taller" gear means or feels like
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Well-Known Member
Like I said, it depends on what you want to spend and how much you want to change. You can go 11-50 on a standard splined hub, and that 50 tooth will get you that low gear you say you're missing today. And note that going to bigger wheels will work against you having low gears, so it does sound like you want a bigger rear cog if you go to 29" wheels.


Active Member
Like I said, it depends on what you want to spend and how much you want to change. You can go 11-50 on a standard splined hub, and that 50 tooth will get you that low gear you say you're missing today. And note that going to bigger wheels will work against you having low gears, so it does sound like you want a bigger rear cog if you go to 29" wheels.

My low gears aren't a problem. It's already too low, the torque is so much as it is that I have to be careful Im not in too low of a gear when taking off otherwise it will wheelie. I should be ok missing my lowest gear. Anyway I guess it's something to think about seems like I won't know for sure unless I tried it.


Active Member
I just went out riding and paid attention to which gear I'm in on hills and taking off from a stop. I can climb the steepest hill in gear 4 if I was in gear 3 it would be smooth like butter but anything lower than gear 3 is literally not usable. I just feel like I'm free spinning the pedals and not going anywhere.


Active Member
I guess all this talk could have been for nothing. I was checking with Biktrix and they said that the 29" may not even fit on the medium frame. They said to take it to my local bike shop to see what they say. By measuring it I am under 1.5" available clearance, plus accounting for tire bounce I don't know if this is enough clearance.


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