All Mountain trail Bike build and advice.

[geosped]

I'm gonna post some pics for those that are interested in a "real trail" bike. I posted good useful info on the pic's captions to make this easier to understand. Below are pics of a good bike if your intention is trail riding. This is like a Rubicon for Jeeps. It's heavy and beefy designed to go trail riding. It's got a very good component spec which should hold up better with the hard abuse of a 1000w motor. It's NOT a down hill beast and not meant to do large drops but can jump and is very capable all mountain bike. Bikes intention is to be a weekend warrior trail rider for a heavier rider. I' mostly ride blues (intermediate) to expert trails (black) very little jumping :-( At least not yet. If your a lighter rider under 200lbs I'd go with the BFANG BBS02 if your heavier over 200lbs I'm 235 I'd go with a BBSHD although the BBSHD is way overkill. It's way to much power and so far I've had 0 issues with the motor.

A couple of things and misconceptions for trail bike. This is an education thread and help you make an informed decisions when your looking for a donor bike. A lot of people use a FS MTB bike to start but and the information for Trail Riding can be misleading and you will quickly find your self looking at the wrong type of bikes. If you want to trail ride make sure you do the following when seeking out a good donor bike. If you follow these simple steps you will be a happier trail rider.

1) FRAME:
Make sure you pick a bike with a straight down tube. This will allow you to maximize how high you can stick the BBSHD up on the frame. Tubes with bends ultimately wont allow you to mount the motor high enough on the frame there by lowering your clearance meaning you will with absolute certainty be nailing stumps and large rocks when you go over them NOT GOOD! So forget Giant Bikes like the Anthem or Trance for example. This is not ideal for trail riding even though it's a great mtb. It does not make a good candidate for a diy emtb.
2) Battery Sizing:
Size your battery based on your riding style. Do NOT make the mistake of getting a 10ah or LARGER battery. There is no need and the larger battery only weighs you down. You dont need it and dont want it. In my case I'm 235lbs I use an 8ah 52v 21700 T40 Samsung cells. This battery allows me to ride for 20miles on intermediate to expert trails in North Georgia about 2hrs of riding and I still have some juice left over. If you ride more than that then go up to a 10ah. If you ride less than that then use 6.5ah. The 21700 cells are larger than the 18650's and provide plenty of discharge rate. The pack does not even get warm after a long climb or stretch.
3) Suspension Travel:
If you plan on riding TRAILS then do NOT GET A Cross Country XC bike as a donar. You will be tempted and there are a BUNCH of used bikes that fit the profile. But do your self a favor and get a "Trail, All Mountain, Enduro, or Down Hill" style BIKE ONLY!!!! The sweet spot is an All Mountain or Enduro. 140-180mm of travel. If the bike has 100mm of travel KEEP LOOKING!!!!
4) Wheel size:
A lot of folks say a 26" wheel is fine but I would disagree. A 26" wheel although your powered you do not have the same rolling resistance to carry your self over large obstacles. A 27.5 or 29"er is the ideal wheel size. Sure you can power pretty much over everything but it's much easier to roll over something where your not really slowing down you find your self loosing a lot of momentum. Find a bike with a 27.5 or 29" wheel. It will allow you to climb easier and more efficiently over anything and typically provide a bit more clearance underneath. They are also faster on the top end but slower on the start. The downside is there more expensive.
5) Motor Type:
For trail riding you want a mid drive so you can take advantage of your gears. Mid Drives are also more efficient when going uphill as they don't get heat soaked like a rear hub drive will. You also want the weight in the middle of the bike and NOT over the rear wheel. You need a good balanced center of gravity (COG). Smaller Chain Ring in front means more TORQUE Large Chain Ring in front means higher top end more SPEED. So if your mountain biking you want more torque. BUT be careful with a smaller chainring and chain line. You might not have enough offset with a small chain ring. For motors right now the options are fairly limited and BFANG BBSHD and BBS02 are the best bang for your buck options. There are better and more expensive options though. I use the BBSHD but the BBS02 is also a great option that provides plenty of power and is lighter and smaller but less power. Buy either option and you will be happy. Be carful when selecting a BFANG kit. These KITS IMO ARE NOT COMPLETE!!!!. You will need an after market chainring (lekkie or Luna), a cheap chain guide (keep chain from popping off), and shift sensor (cut's power to the motor while you shift) with out this you will tear up your drive train.
6) BB Bottom Bracket Length:
Make sure you figure out what kind of BB your using. There are a few good guides out. Measure the length underneath. BBSHD kits come in 68-73mm 73-86mm and 92mm they may even have a 100mm . They also have extension kits. For example my bike is using a Lekkie 86-92mm extension kit.
7) Nuances of newer frames and considerations:
Newer frames and or heavier duty bikes like All Moutain / Trail, DH or Enduro's may have ISCG tabs on the bottom bracket. Meaning this will interfere when you go to install a kit like the BBSHD. You will have to cut at least one tab off. Not a big deal with a Dremel but then again your cutting into your nice expensive bike. It can be a bit scary. These types of bikes will typically come with Press Fit Bottom Brackets so you will need an additional adapter and make sure you get the right size. Lastly chain line issues are a real issue as these beefier bikes are wider and dont allways align properly with the motor. So make sure you pay close attention to the chain stay clearance and chain line. Look at the Luna Eclipse chain rings they have a good tutorial on chain ring offset. My first emtb had a Lekkie 42T but this did not provide enough offset on my new bike so I got a Lunna 42T which has about 25mm of offset. Still wont be enough but it's the best I can do and NO I'm not taking an angle grinder to my BB.

A few drawbacks about the BFANG BBSHD. Throttle can be jerky. Reprograming of the FW will probably be required. What works for me is using the Start Current Sensor to 6 instead of 10 and make sure to set throttle Mode to Current (under throttle settings) One of the con's of the BBSHD is It comes with a crappy chain ring which will need to be replaced, Get a Luna Eclipse or a Lekkie, Another con is it typically does not come with a Shift Sensor make sure you get one. You also need to get a cheap chain guide. Make sure you get one. You really should consider all of these factors when pricing a kit as if you want the best possible experience you should do all of this stuff. Ask me how I know. I will say that the BBSHD is a BEAST. It's been very durable and reliable. It's extremely powerful. To give you an idea. I climbed a hill with a 2018 Specialized elevo in turbo mode and it's far far less powerful from a performance perspective that my BBSHD. Things that will help prevent your chain from popping off: Chain Guide, Narrow Wide chain ring and clutched derailleur. IMO the best bang for your buck here is the chain guide. But you really want all three. The lekkie and Luna chainrings are all Narrow / Wide teeth pattern so your good there and most newer higher end bikes have a clutched rear derailleur like Shimano XT.

Some additional considerations. Crank Arm's. Typical MTB crank arms are 170mm. This provides a lot of torque but with an emtb you don't really need such a long crank arm. Consider getting a 165mm crank arm. This will lower your chances of getting pedal strikes when riding.

On my particular build the only thing that I'm missing right now is what to do with battery. I will more than likely create a mount right above the motor and place it there on some sort of platform and secure it. I like the look under the sadel but this is not ideal especially when using a dropper post if your looking to bomb down some trails. You got to get your seat all the way down. In my case I still have plenty of clearance with the seat all the way down but it's still not ideal. I'm putting extra weight up high.

Let me know your thoughts and If I'm missed anything.

NOTEABLE PICS BELOW:
The pic with the chainline. This is a horrible chain line. This is one of the issues when selecting a bike like this. As you can see it's already using a Lekkie 42T which has an offset of 18.3. I'm going to swap this out to a Luna Eclipse 42T chain ring which has an offset of 24.8mm providing a bit more help. I dont think it's going to be enough. The reason you want a straight chain line is to prevent premature ware on your chain, rear cassette and chain ring. Chain is going to take the most abuse.

Chain Stay Pic. It's hard to see but I have plenty of clearance for a 42T chainring with more offset. You want to make sure that the teeth of the chainring will not touch the chainstay. If it does you will need to use bottom bracket spacers. On my last bike I had used three 1mm BB spacers.

Chain guide IMO great cheap insurance. Look at the inside of the chain guide. It's obvious the chain is getting slapped around and the chain guide is doing it's job. With out this if the chain pops off it may scratch and or do more damage to your frame.

 

[geosped]

On the pick where the lines are run directly under the motor. DO NOT do this as you will pinch the lines. Run them one on one side and the other on the other side. This was a bad idea one that I corrected.

I bundled the wires and put some heat shrink. This is a little bit of added protection overtime wires can chafe and or get caught up on a branch. The heat shrink does add a little protection.

See the one pic where the wires have been rerouted on the sides of the red bracket. you dont want to have the wires under the motor.

 

[Grantmac]

Either of the Bafang motors are a poor choice due to weak bottom bracket, horrible chainline, bad ground clearance and way too big of a chainring.
Unless your trail riding is extremely mellow that is, any jumping other than the smoothest of tracks they won't hold up.

Unfortunately your options are limited with the best currently available being a low voltage build with the CYC X1 Pro and a Castle Creations ESC or VESC running throttle only. Unfortunately not the quietest.
The Lightest drive which is supposed to be released soon is another good option so long as they get the BAC855 programming figured out which nobody else seems to have accomplished.

 

[TNC]

Grant, I think that might be a bit of an overstatement on the 02/HD. There is one real negative that can't be argued, and that is ground clearance. Now, I will say that I measured the ground clearance on the demo Trek Rail 7 we have at the shop, and my Nomad has a tiny bit more measured ground clearance...about a 1/4". The benefit of the Rail is that it has a rubberized bash guard. After riding my Nomad/BBSHD setup in some rocky areas, I do have to pay a little more attention to the clearance on ledges and such...and make some concessions on approach. However, in the few spots where this occurs, the throttle becomes a big aid instead of just slamming into a ledge under pedal power only. I've kissed the motor a time or two already, but it was hard to even find a contact point...the motor case is pretty darned robust. But the motor does extend further than what you normally have for clearance, just not the kiss of death IMO. I was concerned about the wiring coming out the lower back of the motor, but it seems to be in a spot that doesn't get the contact I thought it might. I did wrap the main bundle with braided rubber fuel line as pictured below.

On your weak BB comment, are you saying it's weak in terms of breakage, or that it's a square spindle design, or is it the capture system of the motor with the non-drive side nut system? On the square spindle crank interface, I do wish it was something like the Ultra uses just for peace of mind. However, even in my younger years of more aggressive riding with drops and radical terrain, I never broke or wallowed out one of my crank arms. Using quality crank arms and proper installation and torque goes a long way. On the method by which the motor is attached to the BB, I was not fond of that design. However, I rode the bike quite a bit before making an additional retention plate and never had the motor loosen...see retention plate below. Using a curved, heavy duty rubber pad at the downtube contact patch and making an additional retention plate is just good insurance.

On the chainline, this is only a problem depending on the bike design. Geosped had a decent challenge because his BB width is a little different and he had ISCG tabs to deal with. On my Nomad and an '03 Santa Cruz Bullit I have, this motor did yield a less than optimum chainline with that factory chainring which was easily fixed with a Luna Eclipse 42T. Yes, it required a purchase of an expensive chainring, but it is a fix for the problem. My chainline on both bikes was right in line with my factory chainline. You are correct, however, in that all bikes are not a guarantee for a perfect chainline, but I'd say most 68mm-73mm BB bikes will work...just do some measuring and checking first. Some full suspension designs may always be a wild card in fitment.

On the gearing issue with a 42T chainring...yes...normally that would be horrendous on a pedal-only bike. But with a 9-speed,11-50 steel cassette...Box 3 and others...that is not a problem. It's not a problem because a BBSHD in particular has more than enough torque to cleanly pull through fewer gears and without all the small incremental jumps between traditional pedal-only drivetrains...and that's without unduly loading the motor in too high a gear. Initially I watched my watt guage on my 500C display very carefully, and as long as I wasn't trying to be ridiculous in a high gear situation while accelerating or starting from a stop, the motor was never challenged. This is where the BBSHD apparently shines over the 02 version. That's not to say one should just hammer willy-nilly on the pedals or throttle in any gear or aggressive situation. You have gears...use them. It just doesn't take as many gears or being in a super low gear as it relates to the terrain you're in.

So Grant, I sound like a rep from Bafang, don't I?...LOL! Well, maybe a little, but it's based on experiencing something I really didn't expect would be as good as it turned out. To be honest, I would rather have something like a Luna X1 with the Ultra in-frame motor that is designed like our Trek Rails and Specialized bikes at the shop. I'd rather have the Ultra motor rather than the nice Bosch units that are in our bigger hit Trek emtbs. I'm also a dirt motor guy, so more power is always appreciated...LOL! I think my SC Nomad is a superior bike in terms of handling and suspension on the X1 as delivered, so for the moment I'll stay with the Nomad/BBSHD. And we can't forget to mention the programmable aspect of the Bafangs to suit the rider and conditions.

I'm not finding a lot of warts on this setup, and those I did find are pretty much all solvable or easy to live with. And this may be the point you're making in your opinion. I think the Bafang mid-drive application for actual off road challenges is probably a better fit to a bike person who has some decent mechanical skills and riding experience. I'm not an Erv Kanemoto level mechanic or a Hans Rey level rider, but I'm not bad...LOL! The mechanical skills definitely helped in setup and dealing with the niggling annoyances that cropped up. And let's be honest. Most mountain bikers are not "sending it" out at Bartlett Wash outside of Moab. Most mountain bikers will have no issue on most of the trails being ridden and how they're riding them. I still contend that the BBSHD will perhaps do a little better than you're giving credit with proper setup in the proper bike.

And Grant, while I am differing with you on some of your takes on the Bafang mid-drives, my long winded encyclopedia here is in discussion form and not meant as an attack. Differing opinions are good for discussion...not cussin'...LOL!

 

[COAR]

An XC bike might be a totally workable option if you're not regularly smashing through rock gardens or hitting large drops. The plus is the lighter weight will offset some of the motor/battery, and the frame triangle may be large enough to hold the battery. Just don't go full weight weenie to the point you're severely compromising strength. As TNC alluded to, most riders don't need extreme equipment and would probably be fine with a short travel bike (I've see some folks ride ridiculous stuff on 120mm), but personally the geometry would be a deal breaker if the head angle is too steep (i.e. twitchier, and sketchier going downhill).

A fully kitted conversion will most likely weigh 50-60lbs. Mine is closer to 50. Before building I was concerned about the weight, but now I barely even notice it until I have to lift the bike over a fence or load it on my car.

As for frames, it's probably best to stick with either steel or aluminum. I would worry about cracking the BB shell on a carbon bike tightening it the way I did on my steel one.

The controllers definitely need to be reprogrammed to be more usable on the trail. I went with a config that basically allows 5 lower power levels, and 5 higher power ones. Anything above 30% dramatically reduces the pedaling effort required - to the point I'm pretty much spinning out with a 30x11 on flat.

And I don't think it was mentioned, but it will take some playing around to get the cockpit comfortably setup. I went with a thumb throttle and the 500c display, both mounted on the left side. You probably want the display close enough to easily change levels without removing a hand, however with a dropper post and the throttle mount, it's a bit of a reach.

 

[TNC]

COAR, the weight deal is surprising, but maybe it's a little like a dirt motor. When you have good power, the weight isn't nearly as onerous...LOL! My Nomad weighs a hair over 50 pounds...without the battery...I use a backpack. What the bike loses in flickability it gains in stability. Coming from a dirt motor, it doesn't "feel" heavy underway, but you're right about loading and unloading the bike.

On the throttle I was using the Bafang thumb throttle. It worked fine but wasn't intuitive to me like a motorcycle throttle feels. One of the Luna full grip throttles fixed that, but the throttle is a very preferential thing for most. And I really don't use a lot of throttle except when I start to get stalled or off line like in some rocks where a blip of the throttle gets me going again.

 

[HrKlev]

Great thread!

The reason why I never went with a Bafang is the lack of torque sensor. I had another cadence based system as my first ebike, but I just didnt get used to it in the technical bits if the trail. I guess its a personal thing what you get used to. If I didnt find my own solution I would probably have given the bbs2/bbshd a try after I got fed up with my tsdz2.

BTW, I find the 27.5 trend is quite rudiculus, the difference between 26 and 27.5 is almost non existant. I understand the 29 size, but the 27.5 are nowhere in the middle between 26 and 29. Feels like it was just a thing to force people to upgrade rims, wheels, etc. Biggest reason to go from 26 to 27.5 is just the availability of tires.

 

[Grantmac]

I think probably I ride much rougher trails then most DIY ebikers.
Anything hanging outside the frame is going to get destroyed here and 28t chainrings are common. Square taper is definitely not going to hold up and neither are the tiny bearings inside the BBSx bottom bracket.

I think they are a decent drive so long as people manage their expectations and pick the right frame.

For me personally the right DIY hasn't come along yet so I'm sticking with leg power until it does. I got bored with my 2400w cyclone build because 60# is just too heavy even on a full DH frame.

 

[geosped]

I think probably I ride much rougher trails then most DIY ebikers.
Anything hanging outside the frame is going to get destroyed here and 28t chainrings are common. Square taper is definitely not going to hold up and neither are the tiny bearings inside the BBSx bottom bracket.

I think they are a decent drive so long as people manage their expectations and pick the right frame.

For me personally the right DIY hasn't come along yet so I'm sticking with leg power until it does. I got bored with my 2400w cyclone build because 60# is just too heavy even on a full DH frame.

I've ridden all over North Georgia and although I don't ride the free ride sections I do ride all the black trails and I can say the BBSHD kit has held up rather well not a single issue. I've put over 300 miles over the last four months I've gone through a set of brake pads, and my dropper post is giving me issues now. I've had to degrease my head set as it started squeezing. On occasion like every six rides I'll have to re-tighten the cranks. I've had no broken chains, no chain pop offs just solid performance. It's extremely quit as well. I've heard other ebikes and the BBSHD is as quite as they get. I avg anywhere from 1-2hr ride and I ride 2-3 times a week. The BBSHD has held up great.

Great thread!

BTW, I find the 27.5 trend is quite rudiculus, the difference between 26 and 27.5 is almost non existant. I understand the 29 size, but the 27.5 are nowhere in the middle between 26 and 29. Feels like it was just a thing to force people to upgrade rims, wheels, etc. Biggest reason to go from 26 to 27.5 is just the availability of tires.

I have to disagree I know it's just 1.5" noticed a huge difference between a 26" and 27.5" I would have preferred a 29" but to each his own. The big difference for me was I cleared things easier same trails. Things I struggled with on my 26" seemed easier to clear I also could tell my rides were easier. Maybe it was the suspension on the newer bike but my 27.5" certainly felt like it was easier to ride.

For those that have clearance issues most of the time people are putting these kits on the wrong frames. You really need a straight downtube. If your frame has a bend near the cranks then for sure your gonna bottom out. If pick the right frame you won't have clearance issues.

The other main issue I see folks using too big a battery like a 14-17ah battery to ride trails. If your just riding for a couple of hours your much better off with a smaller pack. My 8ah 52v pack will last a couple of hours and or a solid 20 miles of mixed throttle trail riding. Why carry the extra weight. Just a lot of miss information out there.

 

[TNC]

Great thread!

The reason why I never went with a Bafang is the lack of torque sensor. I had another cadence based system as my first ebike, but I just didnt get used to it in the technical bits if the trail. I guess its a personal thing what you get used to. If I didnt find my own solution I would probably have given the bbs2/bbshd a try after I got fed up with my tsdz2.

BTW, I find the 27.5 trend is quite rudiculus, the difference between 26 and 27.5 is almost non existant. I understand the 29 size, but the 27.5 are nowhere in the middle between 26 and 29. Feels like it was just a thing to force people to upgrade rims, wheels, etc. Biggest reason to go from 26 to 27.5 is just the availability of tires.

Apparently a decent amount of respected manufacturers will disagree with you on the viability of 27.5" wheels/tires. Plus on top of that, a good deal of this depends on application, preference, terrain, etc. Longer travel big hit and DH bikes can benefit from 27.5 with many riders, and smaller framed bikes for shorter riders can also benefit. It's about freedom of choice and application. "Ridiculous" is having no choices. And I'm no 29'er hater by any means.

 

[HrKlev]

I dont hate on bigger wheels either, my next bike will probably be a 29er, I like them a lot. What I dont get with the 27.5 is that they are not in the middle of 26 and 29, they are much closer to a 26. I highly doubt any of us non pro riders would notice the step from 26 to 27.5 in a blind test on comparable bikes. Now in a few years there are tons of great bikes out there that dont get to choose the great tires and wheels because the 26er are dying. We would have been fine with 26 and 29. The 27.5 is too close to the 26 to justify replacing the bike to get decent tires i the future. Thats just my opinion.
The manufacturers agrees with anything they make money out of.

 

[geosped]

I dont hate on bigger wheels either, my next bike will probably be a 29er, I like them a lot. What I dont get with the 27.5 is that they are not in the middle of 26 and 29, they are much closer to a 26. I highly doubt any of us non pro riders would notice the step from 26 to 27.5 in a blind test on comparable bikes. Now in a few years there are tons of great bikes out there that dont get to choose the great tires and wheels because the 26er are dying. We would have been fine with 26 and 29. The 27.5 is too close to the 26 to justify replacing the bike to get decent tires i the future. Thats just my opinion.
The manufacturers agrees with anything they make money out of.

I went right from a 26" Cross Country Specialized Epic with a BBSHD to a 27.5" All Mountain bike at first, with out a BBSHD and the first thing I noticed, is that I was not struggling at all over the sections I struggled with the 26" that 1.5" diffrence in wheel size made a considerable difference. I could tell immediately. When I put the BBSHD on the 27.5" it was like climbing over obstacles were not even there. A 29'er is a lot harder to get up to speed. If your pedaling a lot it definitely takes more effort to get up to speed but once your there it's much easier. I ride with friends that are a bit shorter like 5.6 - 5'8 and they prefer a 27.5" bike over a 29er. I've owned both and with a kit like a BBSHD I'd prefer a 29er but you also have a lot less options out there in terms of adequate frames "straight down tubes". Having ridden both I'm still saying at least for me it was more than a little difference going from a 26" to a 27.5" The most noticeable difference to me was being able to get over drops or climb drops that I could never do before with the 26" I'd have to get off and walk over and I was able to do just fine with the 27.5". Also I think the 29ers dont have as many beefy options out either. I see a lot more trail or enduro type on 27.5 like 150-180mm travel. Most of the 29ers I've seen have less travel. I think when doing an DIY and you plan on trail riding one should strongly consider beefier equipement, like bigger shocks, better brakes, better quality components etc... Even though my cross country bike was a very nice spec, XT it was sketchy as hell with only 100mm of travel and 1.95" tires were the widest I go get on that my rim. I had a tendency to bottom out the suspension and putting more air and firming it up led to very harsh riding.

 

[COAR]

I went right from a 26" Cross Country Specialized Epic with a BBSHD to a 27.5" All Mountain bike at first, with out a BBSHD and the first thing I noticed, is that I was not struggling at all over the sections I struggled with the 26" that 1.5" diffrence in wheel size made a considerable difference. I could tell immediately. When I put the BBSHD on the 27.5" it was like climbing over obstacles were not even there. A 29'er is a lot harder to get up to speed. If your pedaling a lot it definitely takes more effort to get up to speed but once your there it's much easier. I ride with friends that are a bit shorter like 5.6 - 5'8 and they prefer a 27.5" bike over a 29er. I've owned both and with a kit like a BBSHD I'd prefer a 29er but you also have a lot less options out there in terms of adequate frames "straight down tubes". Having ridden both I'm still saying at least for me it was more than a little difference going from a 26" to a 27.5" The most noticeable difference to me was being able to get over drops or climb drops that I could never do before with the 26" I'd have to get off and walk over and I was able to do just fine with the 27.5". Also I think the 29ers dont have as many beefy options out either. I see a lot more trail or enduro type on 27.5 like 150-180mm travel. Most of the 29ers I've seen have less travel. I think when doing an DIY and you plan on trail riding one should strongly consider beefier equipement, like bigger shocks, better brakes, better quality components etc... Even though my cross country bike was a very nice spec, XT it was sketchy as hell with only 100mm of travel and 1.95" tires were the widest I go get on that my rim. I had a tendency to bottom out the suspension and putting more air and firming it up led to very harsh riding.

to play devil's advocate, how much of that is due to an overall increase of bike capability (more travel, slacker geo, fatter tires) vs the moderate increase in wheel diameter? I have 2 hardtail mt bikes: 1 with a BBS02 and "26+" wheels (2.75 x 26, effectively 27.5" in diameter), and the other a 29er with more modern geo (slacker HT and longer reach). The 29er feels more playful and agile (as it should being half the weight), and is also more confident on the DH despite having 10mm less travel and a lower quality fork, but it's hard to tell if that's due to the better geo, or the better rollover of the 29s. FWIW I don't feel much issue in peddling it up to speed - proper gearing helps a lot with that.

When I was researching my since-abandoned mullet conversion, I found this site comparing the wheel differences. Despite a nominal 1.5" difference, 26->27.5 actually only sees a 1" increase in wheel diameter.

https://www.mbr.co.uk/news/product_news/etrto-364583

 

[scianiac]

It is a real shame that 26in tire options are now so limited as I agree 26in is just fine or better for some applications. For me the biggest difference with wheel size is based on bike/rider size. My relatively short travel (100mm) 29er in size small already looks downright silly. To make the frame small enough and still fit the large wheels the proportions get all weird and with longer travel bikes it gets even worse. While the bike does ride over things nice and it's long length makes it very stable it feels a bit difficult to control and I feel like I have nowhere near as much weight control as I would like due to the bike's length to my size being ratio. While long, slack, and low bikes have their place and I can see why the trend is going that way we all don't ride park. The trails I ride are very tight and technical, often full of tight switchbacks and chicanes between trees, a long slack 29er can't do it's high speed monster truck thing if you can't really be going more than 6mph through a flat rock/root garden. I think my next bike will be a 27.5 unless I find a really nice 26 with modern enough geo and can just live with the limited tire options.

From an E-MTB perspective I think there is something here. While the improved rollover of larger wheels makes a bike "faster" I don't know that I really care, if I want to go faster I will just apply more power. For handling I would rather have more suspension travel and higher volume tires than larger wheels. Similarly I would rather have a shorter bike I can move the weight around more (again due me being short) to help me get over difficult terrain than larger wheels and a bike I'm more along for the ride with. This of course wouldn't be an issue for a taller person who can move their weight around on a longer 29er with ease.

TLDR: Smaller wheels are better are better for smaller bikes/riders.

 

[Greendog]

I still don't really get the point in 29 inch wheels not impressed at all,
yes tiny bit less rolling resistance 10 percent less supposedly, don't believe that honestly think bit clumsy, and make the bike just to big,
OK if your 7ft but not as manoeuvrable and subject to more giroscopic influence so not as good as 26. the 27.5 s I rode were comfortable seemed make frame bit more upright could have just been the bikes though ,
but on an ebike pointless , 26 is optimal puts the cranks at the right height, not to mention compatibility issues which always seem to equal extra money for manufacturers as oposssed to actual benefits for us,
is just trying push the BS line that newer and bigger is better and in line with fashion of manufacters since 2000 for making things more about commercial than quality, which I don't agree with,
and yes i do find it annoying the better tyres not available in 26 so much anymore , ebikes are bit of a different ball game to MTB as weight not so critical , rant over was hoping someone would mention 29s as they my pet MTB hate but I'm old school and think square taper cranks and 7 speed freewheels perfectly good for ebikes :wink: , don't get me started on taper forks just kidding but if anyone has any plus points in defence of 29s love to hear them

 

[scianiac]

Yeah in many ways I agree with you about 29ers, the only reason I have one is because it was the best deal I could find on a used full sus. I can see though that for many applications that 10% (which must be pure rollover and doesn't take into account the rider absorbing the terrain which they may be able to do better with smaller wheels) is useful to gain maximum speed in some race conditions. But on an ebike or really just in a lot of real trail riding conditions the maneuverability and control is worth more than the efficiency.

For an Ebike the efficiency is nice but often the things you gain from loosing a little bit of efficiency is worth way more, like putting faster rolling tires on, sure they roll slightly more efficiently so I have a tiny bit more range but at the loss of traction, that trade off isn't worth it for real trail riding.

 

[markz]

Depends on how and what terrain you ride and what you are riding.
Square tapered for those who don't pedal much.
26 for those who dont care or for those who want quick action
29 for those who ride on the pathways or want a bit extra speed or just bought a 29'er

 

[ZeroEm]

I like the larger 29" wheels for rolling and riding the roads. For off road eBike's they are bulky and would only benefit riding over larger objects. Depends what type of terrain.