20" vs 26" bike wheel, what's best?

[dogman dan]

FWIW, motorcycles are mid drives. So none of that really applies to how hub motors run.

Chalo is not really wrong at all. He's just got a different, more slow traveling point of view. The disagreement is really comparing apples to oranges mostly. 26" wheel is wrong for some applications, right for others.

Once you start thinking in terms of above 2000w of motor, then it does get dumb to want a 26" wheel hub motor wheel for street use. Plenty of power now to overcome any issues with lower rolling resistance. But if your bike will be used on street and dirt, the many 26" full suspension bike builds are the way. Or, at least, not quite as small a wheel as a scooter or 20" bike wheel.

Re visiting one of Chalo's points, as cars have needed better MPG lately, tires have gotten larger diameter. But again, mid drive, they adjust the gearing for the large wheel.

 

[Wheazel]

Answering the threads question is a matter of many compromises.
You need to determine how your riding will look like. What events will be common and what will be uncommon or nonexistant.
Then decide "what wheelsize is best".

 

[evolutiongts]

20" wheels in conjunction with high power ie. above 3000watts and fitted with 16" moped tires will give a better ride, traction, cornering power, than 26" wheels.

26" would be better for off roading.

 

[MadRhino]

20" wheels in conjunction with high power ie. above 3000watts and fitted with 16" moped tires will give a better ride, traction, cornering power, than 26" wheels...

False for the three affirmations
That is a perfect score

 

[MadRhino]

Sorry, this shouldn't have been told without explanations.

Smaller wheel diameter do have some advantages, but they are not in the domain of traction and ride quality.

All other factors equal,
the small wheel steers easier but cornering performance is poor.
at high speed, it is riding closer to destruction
potholes and bumps are making it a harsh ride
it is making braking distance longer

I believe you meant that a good small wheel is better than a crappy large one.

 

[TroySmith80]

I built a 20" wheeled cargo bike for a lot of very logical reasons. I don't like it very much because it rides too rough.

 

[dogman dan]

Nice bike otherwise though... A do over with a 26" front wheel, and shock fork might help a lot. The front cargo might be affecting the ride a lot too.

I would not say my latest bike rides rough. But it's definitely for street use. It's certainly not perfect for everything. But it does tow my trailer great, better take off on uphill starts than the 26" wheel for sure. It handles beautifully because of a good size contact patch on the steering/ braking wheel, and perfect placement of the battery weight.

 

[Voltron]

The large front wheel/small back wheel look... everything old is new again....



It got cropped off... but thats a passenger trailer he's towing. Check out the solid drive rods to the back wheel...like an old locomotive.

 

[MadRhino]

everything old is new again.....

Sure not my first wife

Nice find. The bike is looking very much like some builds on ES.

 

[Voltron]

thats like the old joke.... a farmer goes to the big city for the first time and has never seen an elevator. He sees an old woman go it a small room, and then minutes later a young beauty step out of the same door. He then exclaims " I can't wait to bring my wife with me on the next trip!"

 

[dogman dan]

Yeah, anything you invent for a bicycle, has been done by somebody before. Likely in 1895 or so.

At one point, all the really creative people were into bikes, and some of them went on to build really interesting things. Like the airplane.

Sorry if any French guys are reading this, but Santos Dumont was still bad ass, even if he was second.

 

[Voltron]

If you're talking early flight, its hard to beat Otto Lilienthal. He's the first person recognized as doing controlled repeatable glider flights in the 1890's, and was able to soar small hills where the wind was strong enough to hover stationary with respect to the ground. His work led the Wright Bros to relocate to someplace windier.. Kitty Hawk NC, where all this is required learning when you are a young hanggliding instructor there teaching on and flying the same dunes the Wrights did their non powered glider tests on.

 

[slowhands]

John CR and Dogman others are right on I am now going from a 26 to a 20 or maybe a 24 but I know I need to go smaller , Chalo is so wrong its funny he should read the history of the motorcycle

Really? I have to disagree. Chalo is totally correct. He makes these blunt pronouncements, but he's been correct every time. Voice of Experience. "..20 inch wheels have a much harsher ride, more rolling resistance, less traction, and accelerated wear characteristics compared to 26 inch wheels". The reason to go to a small 20" wheel with a non geared hub motor is so the hub motor can spin faster, which hub motors need to do for good power. In other words, you compensate for a flaw of the motor by using a small rim. If you have a geared hub motor or mid drive, there is no advantage to a smaller rim. With a smaller rim, you need a fat tire and excellent rear suspension for similar riding comfort, which adds weight and rolling resistance. You may find you like that solution better, a matter of personal taste. Wheelies are easier on a smaller wheel. But the technical points go to a larger rim.

There are significant advantages to a larger rim, namely smoother ride, lower rolling resistance, better traction. In fact many of the high end mountain bikes are moving up from 26 to so-called 27.5" (and also adopting a solid 12x142mm rear axle, another upgrade). I believe that the 26" wheel is here to stay though, due to customer acceptance and lower cost than the newer 27.5" technology. Some say the makers just want to obsolete the old and force you to upgrade, but the 26" wheel has market share that won't go away. Time will tell though, I'm sure looking forward to riding one of the newer bikes to see what I think.

Just as a complete digression, I'm hating 9mm quick release axles more every day. My first pet peeve is they make wheels too easy to steal. Second peeve is they are too flimsy. This week I had two broken axles to fix. Snapped right at the drive side bearing race, both. You can't expect a hollow 9mm tube to be as strong as a solid one of similar materials. On my bikes, I replace with solid axles. I'm thinking the 12mm axles make even more sense.

 

[Chalo]

I think 27.5" wheels are a pretty crass attempt by the industry to get people to buy the same kind of equipment they already own, but for more money. I look at it this way: for all the same reasons that 26 inch wheels are better than 24 or 20 inch wheels, 29 inch wheels are better than 26. And if you really are too short to get good results from 29 inch wheels, 26 inch wheels are only 9.5 percent smaller in outer diameter (assuming 50mm tall tires). Why bother with wheels only 5.5 percent smaller than 29ers, only 3.8 percent bigger than 26 inch, if they cost extra and reduce parts availability? I'll tell you what the manufacturers' reason for 27.5" is: You have to buy a new bike to get it.

Just as a complete digression, I'm hating 9mm quick release axles more every day. My first pet peeve is they make wheels too easy to steal. Second peeve is they are too flimsy. This week I had two broken axles to fix. Snapped right at the drive side bearing race, both. You can't expect a hollow 9mm tube to be as strong as a solid one of similar materials. On my bikes, I replace with solid axles. I'm thinking the 12mm axles make even more sense.

Rear quick release axles are 10mm in diameter; fronts are 9mm. Rear axles chronically break not due to their diameter, but due to the amount of overhang imposed on them to accommodate multiple speed freewheels. Axle breakage is generally not a problem with hubs spaced for single speed or five speed freewheels, but became an inevitable problem by the time seven speed freewheels arose.

That's why cassette freehubs have become more common-- they can use the same old axles and bearings, but with much less overhang. In my observation, cassette hub axles only break when the dropouts are out of alignment such as to put large bending loads on the axle when the QR is tightened.

Solid axles are not of much help in preventing axle breakage. They add hardly any strength or stiffness to the axle-- only as much as a rod the size of the hole in a QR axle. Almost all the axle's strength is in its outer layer.

I like freewheel hubs when their axles are larger than the frame slot allows. For instance, one rear freewheel hub I made has an axle 19mm on the drive side, reduced to 16mm to pass through the hub bearings and out to the other side of the frame. Even though it's made of aluminum, that axle will never bend or break under foreseeable riding loads. It's drilled and threaded at the ends for 3/8" (9.5mm) bolts that fasten it to the frame.

GSport hubs were a commercial example of hubs using the same principle: oversized axle with only the end bolts passing through the frame slots.

A seven speed freewheel hub made this way would suffer no axle breakage problems whatsoever.

 

[John in CR]

The effect of the increase in rolling resistance is minuscule and is likely to be more than offset by the aerodynamic gain of a lower bike and smaller wheels especially considering an ebiker's higher typical speed. Of course a smaller wheel follows the dips and bumps more, but the ride is easily made smooth by a properly tuned suspension. If you're talking about a hardtail, then regardless of wheel size you need a smooth road and/or learn to avoid obstacles, because that big heavy DD hubbie is hammering your spine. For serious off-road riding hubmotors simply aren't the correct answer. As far as traction goes, if there's a difference it's gotta be tiny, and anyone riding in a manner where it could make a difference will hit eat asphalt so often they probably need the lower performance of the motor in that larger wheel.

The advantages of the smaller wheel in efficiency and performance are tremendous, which I outlined earlier (https://endless-sphere.com/forums/viewtopic.php?f=3&t=74541#p1125393).

Fellow ebikers, don't listen to big wheel advocates. Guys like Chalo are the same prejudiced group who created the ridiculously restrictive ebike laws for much of the world. Simply use the smallest diameter wheel you can live with on any DD hubbie.

Once you figure out how to make the small wheel cool enough for you to ride, then you'll come to appreciate a big advantage I forgot to mention. When putting an ebike together you quickly find that the biggest premium is space, and smaller wheels free up a lot of space for batteries or controllers.

 

[markz]

Good point on the space saving aspect of smaller diameter wheels. I am sold on the idea of smaller wheels. I think most of us ride on the road anyway.
There is absolutely no reason to go 27.5" or 29" tire for a hub motor. Non! I've read articles on it, and they debunk the issue too. For professional bicyclists sure, but for regular folk, just stick to 26" tires, and if you want better performance out of your DD motor, then go smaller.

 

[Voltron]

I've been thinking about moving UP to 20", from my 16"... you know, for some of plush ride and traction that I hear about, but I'm not sure I''m ready to trade it for the hot acceleration and smoking uphill romping I have now, esp since I have all the traction I could ever need, and enough comfort to ride for two hours straight already...





Thinking mid motor and chain drive for the next iteration... and I agree Chalo is right about many bike things... but not this particular thing.

 

[sendler2112]

The issue I see for a country road commuter with using a 406 wheel is 53/11 gearing at 90 rpm topping out at 24.5 mph.

 

[dogman dan]

Again with the apples and oranges. It's for hub motors that a wheel smaller than 26" works well, and,,,, for street. But for dirt, you can get very good performance in 26" in several ways. Slower winds help some, and a gear motor works well too if you don't jump much and shear the axle key all the time.

Obviously with a mid drive, you just choose the gear you need, and could run a 36" wheel if you really wanted to. In a mid drive bike, I'd see no real reason at all to go with a really small wheel. But you don't have to have a 26" wheel to have a good ride. Not in motorcycle tires and rims. But in a skinny bike tire, then 26' rim will help a lot with the ride quality.

 

[Voltron]

Sendler2112's numbers actually work out about right...with the 53/13 gearing I'm running, top comfortable pedaling speed is 23ish, and 28 or so in a sprint, which actually works out just fine for jumping on the pedals coming out of corner or climbing, then settling into a tuck as the motor really gets into its 30+ powerband. And making it easier to get a little more top end pedaling without running some kind if jackshaft, or Schlumpf drive at the crank is one of the things heading me towards a bigger back wheel, but then my commute changed and I do a lot less long and straight runs, so it sort of dropped in importance now that sprinting is dominating.

 

[Chalo]

... and I agree Chalo is right about many bike things... but not this particular thing.

You'd better tell automobile and motorcycle manufacturers, then, because they're missing out on your wisdom.

My last motorcycle had a 25 inch front wheel and a 26 inch rear wheel. Pretty much all street cars, motorcycles, and bicycles made have wheels in the 25 to 27 inch overall diameter range, unless they're bigger for fashion reasons. These are well financed, mass-produced machines that can start with whatever wheel diameter they want, and make the rest of the system conform to it. What do you think the engineers behind these things aren't getting, if smaller wheels are just as good? Smaller wheels are a little cheaper to make, and car companies love that so much. Why don't they use them?

I understand that in the e-bike world, a donut wheel is the equivalent of a drag racer's 4.11 ratio differential. But it comes with serious tradeoffs that make it the wrong wheel for most jobs.

 

[sendler2112]

Playing with the simulator does show the leverage advantage of a 20" wheel on take off though. Take a NineC 3004 in a 20" wheel and a NineC 3006 in a 26" wheel. Given a 72V pack and 40A controller, they both hit the same 40 mph top speed. But increase the load with extra weight and a steep hill to extrapolate the performance at launch from a stop and the 20" wheel will accelerate almost twice as fast in the beginning. Assuming it is not spinning out. The 20" also keeps a slight advantage in power consumption with the throttle set to 35mph for each case. But can't really be pedaled above 25mph for open roads which is my hang up. So if you have a lot of stop and go traffic, then the 20 will be much quicker. But for all the reasons stated above and to have enough wheel inches to pedal, I would choose a 26.
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NineC 3004 in a 20" wheel top speed is the same at 40 mph
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NineC 3006 in a 26" wheel top speed is the same at 40 mph due to the slower and torqeyer wind but...
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NineC 3004 20" loaded up a 20% grade. Even with it's high speed wind, the 20" wheel accelerates much faster at 9 mph versus 6 for the 26" wheel.
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NineC 3006 26" loaded up a 20% grade
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NineC 3004 20" throttled to 35mph is still using 1 amp less than the 26" wheel even though the rpm's are up well beyond the lugging zone of take off.
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NineC 3006 26" throttled to 35mph.
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[madin88]

My advice to the creator of the thread:

try it out by yourself by buying two different wheels. for instance 16" and 19" moped rims or 20" and 24" bicycle..
nobody can tell you what you personally going to like more except yourself. its about making tradeoffs between performance (mainly a cooler running motor) and riding comfort.

what i can say from my personal experience:
on one of my bikes i changed from 16" to 17" moped and the bike felt noticeable comfortablier in ALL aspects after that.
both the 16 and 17" tires had the same width (2,75") and similar rubber compound, so the gain was almost entirely related to the larger diameter.

on another bike i have laced the same motor into 24" bicycle rim (so about the same unsprung weight) and i hardly can feel a difference in comfort between this and the other bike.
because of this experience i would say 17" is the sweet spot for both- comfort and performance. if you want to have a lightweight wheel for a not so heavy hub, than 22" BMX should be a good size but there also should be good tires available. it does not help much if the size is optimal but than you cannot find good tires..

about the suspension:
even a 500$ premium damper CANNOT smooth out the disadvantages in road handling a heavy hub motor brings with it. IMO the only thing that really helps (aside from larger wheel size) is a good tire with soft compound (true racing tires for instance) and low air preassure.

 

[Ykick]

My advice to the creator of the thread:

try it out by yourself by buying two different wheels. for instance 16" and 19" moped rims or 20" and 24" bicycle..
nobody can tell you what you personally going to like more except yourself. its about making tradeoffs between performance (mainly a cooler running motor) and riding comfort.

what i can say from my personal experience:
on one of my bikes i changed from 16" to 17" moped and the bike felt noticeable comfortablier in ALL aspects after that.
both the 16 and 17" tires had the same width (2,75") and similar rubber compound, so the gain was almost entirely related to the larger diameter.

on another bike i have laced the same motor into 24" bicycle rim (so about the same unsprung weight) and i hardly can feel a difference in comfort between this and the other bike.
because of this experience i would say 17" is the sweet spot for both- comfort and performance. if you want to have a lightweight wheel for a not so heavy hub, than 22" BMX should be a good size but there also should be good tires available. it does not help much if the size is optimal but than you cannot find good tires..

about the suspension:
even a 500$ premium damper CANNOT smooth out the disadvantages in road handling a heavy hub motor brings with it. IMO the only thing that really helps (aside from larger wheel size) is a good tire with soft compound (true racing tires for instance) and low air preassure.

And good advice it is!

 

[John in CR]

It seems like there's a lot more whining about unsprung weight than there would be about a harsher ride due to a smaller wheel. Since there's such a big decrease in heat created using a smaller wheel, then for those who are satisfied with a given level of power, torque, and efficiency can use a smaller and much lighter hubmotor. I'll throw 40% out there as an easily supportable estimate of the potential weight reduction, and that's without a change in quality or design.

Issues like pedal clearance and aesthetics are easily solved. Greater rolling resistance and less traction are such small differences they're silly to bring up. If ride comfort is all you have to hang your hat on, then I submit that a significant reduction in unsprung weight will have greater positive effect than the ride comfort detriments of the smaller wheel itself.

Let's hear some more anecdotal evidence in support of big wheels.