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

[Voltron]

... 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.

Why would I want to talk to car and moto manufacturers? You're just being silly, because we're talking about ebikes! Comparing them to cars and motorcycles that have the power to go 75+mph and weigh hundreds to thousands of pounds (where traction and ride comfort are actually factoring in) just doesn't work. On a moderately powered, lightweight vehicle you just don't need that much wheel.

But maybe you need to share YOUR wisdom with all the companies that are recognizing the benefits of small back wheels...

 

[Voltron]

THIS ISN'T VOLTRON.... (just a girl he splits his house with and also doesn't have an ES account) but I've ridden his blue baby ALOT! Best ride I've ever been on, and I've been on quite a few electric bikes out there. That bike is actually what got me interested in electric bikes because it feels perfect when you ride it. I think the traction and comfort/ride quality is the best I've ever experienced. He has let me ride it sometimes on fast, windy mountain roads and I felt safe and comfortable the whole way.

[youtube]OJglGTHijNE[/youtube]

That got us thinking about what bikes I've ridden....( we're standing here together and thinking about it...)

Felt Verza
Felt Outfitter
Haibike xduro 29er (Felt great, but like nothing compared to the blue baby)
Multiple Pedegos
Yuba Spicy Curry
Extracycle Edgerunner
Izip Path+
Some Prodecos
Haibike Trekking RX and Pro
Stromers
Izip E3 Metro (great feeling)

thats the short list anyways....

 

[dogman dan]

Damn right, but that bike does not have a small bike wheel on it. You know that makes all the difference for traction. The small bike wheel is a compromise, when it comes to traction. But putting a really fat back tire on a bike can be a bit tricky. Now your bottom bracket is too narrow, etc.

That reminds me, I need to get on the hunt for a 20" bike tire for my new bike, something in 2.5" wide.

 

[John in CR]

How many forum members have had traction problems due specifically to a small wheel on their hubmotor? ie They ate asphalt running a small wheel and wouldn't have if they were running a larger wheel on their hubmotor. I'd venture to say that number is exactly 0 as long as you exclude having more thrust force at the contact patch with a 20", which would be a rider error, not a tire problem. IOW it's a non-issue.

Let's also look at how many people had heat failures running a 26", who wouldn't have running a 20" with the same settings. That most likely would cover the overwhelming majority. While we're counting up failures, at least some of the axle spinouts wouldn't have happened running 20's.

Now let's look at how many people report a significantly higher fun factor when going to a 20" wheel. Include better hill climbing too. That's 100%. Those who worry about looks, or have pedal strike or geometry issues simply need to be creative. The Edgerunner cargo bike above is a good example that a small wheel can look fine. Miles' elegant e-Moulton is another good example.

While these are just anecdotal evidence, at least they're supported 100% by the physics. The physics also explains why there are millions of hubmotor driven electric scooters, and other than a very few low power models sold in areas with very flat terrain, there are no emotos with hubbies.

 

[spinningmagnets]

Somewhere near the beginning of this thread is a statement along the lines of "it depends on the job", and I feel that is the correct answer. If I was going to replace one of my cars with a serious ebike, the Edgerunner is at the top my short list.

I just read a glowing review of a full-suspension downhill bike with a 27.5 rear tire, and a 29'r front, and the reviewer gave very specific details as to the situations where that was beneficial, so readers could determine if their type of riding would make that worth a test ride. Another bicycle shop review mentioned some of their riders have bought full-suspension fatbikes, and swapped the 4-inch wide tires for 3.0's

If you put heavy and bulky cargo on the back of a longtail, the lower mounting of cargo is a benefit. If you don't it isn't. If you live where there's frequent and large potholes, that's gotta be a major consideration, too.

 

[sendler2112]

I was surprised to see through playing with the simulator though, what a huge advantage for acceleration it is for hub motors to run the smaller wheel even when they are wound for the same top speed. For an urban play bike or cargo bike up to 25mph, the 20" rear really is a no brainer. Keep the 26" on the front.

 

[Chalo]

I've built more twenty inch bikes and trikes for my own use than most here ever will: five that I can think of, four of which I still have. Twenty inch wheels are strong, and often I need that. They take side forces on trikes and sidecars better than bigger wheels by far. They allow a lot of room for other components or loads. There are many wide, high pressure, smooth treaded freestyle tires in the 20" size. That's why they are good for trikes and cargo bikes.

On the other hand, they ride roughly and they have high rolling resistance, short overworked contact patches, and increased tendency to bounce clear of the road surface. That's why they're suited for low speeds, just like trikes and cargo bikes.

Turn up the speeds, and all their shortcomings come into sharp focus. My current e-bike is a pusher trailer based on a tagalong kid bike, fitted with a 16" hub motor wheel. Even at low speed and low motor power, plus hitch geometry that causes it to push itself firmly into the ground when applying power, it spends a large amount of the time bouncing and skittering across the ground surface. The only reason I can live with it is because neither I nor my luggage has to ride on it.

 

[Jonathan in Hiram]

I was surprised to see through playing with the simulator though, what a huge advantage for acceleration it is for hub motors to run the smaller wheel even when they are wound for the same top speed. For an urban play bike or cargo bike up to 25mph, the 20" rear really is a no brainer. Keep the 26" on the front.

That's the ticket, I have two bikes now with 9C hub motors, one in a 26", the other a 20", they feel quite different on the same battery and controller, the 20" is much snappier although the 26" has a bit longer legs. It seems that you trade a bit of top end speed for considerably better acceleration/hill climbing and better range. The 26" will walk away in a straight and level race after about the first hundred yards or so but on rolling hills the 20" comes a lot closer overall, pedaling seems to make a little more difference with the 26" than the 20".

Sooner or later I'm going to break down and get a Phase Runner controller, I'll be really interested to try field weakening on my 20" setup.

 

[Voltron]

Well.. the main reason I jumped in on this thread so hard was Chalos comments about hokey scooter hub motor conversions being as merit-less as an electric shopping cart for getting around. So my comments are meant for that issue... not cars, motorcycles, pusher trailers, or skinny 20" regular bike wheels and tires.

And yes... a 26" on the same power pack will have a little better top end.... but the point is you up the voltage on the smaller wheel until its top end speed is only limited by your instinct for self -preservation kicking in

 

[Chalo]

Donut wheels are still impaired. That's why racing scooters need scooter-only racing classes. They can't compete with bikes that have full sized wheels.

 

[Voltron]

Well.. the main reason I jumped in on this thread so hard was Chalos comments about hokey scooter hub motor conversions being as merit-less as an electric shopping cart for getting around. So my comments are meant for that issue... not cars, MOTORCYCLES , pusher trailers, or skinny 20" regular bike wheels and tires.

I put it in bigger letters for you this time for you.... not talking about MOTORCYCLES! So you can make that perfectly valid point as many times as you want and it still won't apply to the ebikes we're talking about..

 

[Chalo]

Real bicycles have always had bigger wheels than that. That's where I started from. In fact, the more critical the performance aspect of a bicycle, the larger the wheel. Small wheels have always been associated with slow bicycles.

 

[sendler2112]

the 20" is much snappier although the 26" has a bit longer legs.

Are your motors the same number of turns? There is no reason the 20 can't have the same top speed and still be snappier if it is wound for it with less turns.

 

[Voltron]

Real bicycles have always had bigger wheels than that. That's where I started from. In fact, the more critical the performance aspect of a bicycle, the larger the wheel. Small wheels have always been associated with slow bicycles.

Real bicycles? Like nobody else here rode a non ebike for years and years and years and started there too?? That sounds as judgmental as the people that yell "cheater" at real Ebikers....

And with normal human leg power, every bit of rolling resistance counts, and trying to get broad gear range is tougher on small wheels... but again... we're not talking about racing a road bike!

"Small wheels have always been associated with slow bicycles" ...until small powerful hub motors came along that is! Welcome to the new paradigm.

 

[Chalo]

Then I argue you are talking about motorcycles. Which also do better with bigger wheels.

 

[Jonathan in Hiram]

the 20" is much snappier although the 26" has a bit longer legs.

Are your motors the same number of turns? There is no reason the 20 can't have the same top speed and still be snappier if it is wound for it with less turns.

I have a 2807 in a 20" and a 2809 in a 26", not quite enough difference in the winding to make the 20" as fast as the 26".

Agreed that it's possible to make 20" machine as fast on the top end by picking the right winding, I'm using what I already had on hand though.

Chalo is right in that a bigger wheel tire has a lot of advantages, the problem is working with the current state of hub motor technology a smaller wheel is better in some fairly crucial respects for certain types of street riding. And then of course there is the packaging issue that John brings up, bigger wheels take up more room that could be used for cargo, batteries and so on.

Fatter and more supple tires at lower pressure do help smooth out the inherent roughness of the smaller wheels. For ebike road transportation purposes where acceleration, thrust and climbing are priorities then the smaller wheel is superior from a strictly electric thrust point of view. Long distance cruising with little stop and go on flattish to rolling terrain can take a larger wheel and make it work a bit better than a small one for electrical propulsion purposes.

 

[Voltron]

Then I argue you are talking about motorcycles. Which also do better with bigger wheels.

Did you see the gigantic smile on the girl in the video up there loving riding it? THAT'S the only argument I need to be convinced small scooter wheels in back work just fine!
And she knows electric bikes, so she knows what she's smiling about!

 

[John in CR]

Then I argue you are talking about motorcycles. Which also do better with bigger wheels.

Did you see the gigantic smile on the girl in the video up there loving riding it? THAT'S the only argument I need to be convinced small scooter wheels in back work just fine!
And she knows electric bikes, so she knows what she's smiling about!

Chalo, completely dismisses the simple fact that DD hubmotors perform significantly better and more efficiently in smaller wheels. Then he supports his prejudiced statements with info that rule out bikes with suspensions as well as bikes without suspensions, while ignoring the beauty of single track that makes potholes and obstacles easy to avoid. Bikes without suspensions cause much more harshness of ride than the ride difference of a 20" vs a 26". Also, a suspension sucks up drastically more pedal effort than the minuscule increase in rolling resistance of a 20" wheel. The prejudiced part is that it's ok for him to build many bicycles with 20" wheels, but it's a horrible thing for ebikes to run a 20" wheel. Even funnier is while making mountains out of mole hill differences, the handling and safety defects of his pusher trailer are ok despite a cargo ebike being far better.

 

[Chalo]

What I think 20 inch wheels are bad for is fast bikes-- whatever kind. They are fine for slow bikes, just like 6 inch solid wheels work fine for shopping carts.

But the only reason they seem to interest you guys is that they help you go faster (on a bike that's less suitable for speed).

 

[Voltron]

You're perfectly free to think that. And all the people that have had a great experience on them are going to think something else.

And it's been pointed out a few times, but the speed isn't the only interest, or even the primary interest, for me anyway. It's the lack of heat build during hard city sprinting and climbing.

 

[Jonathan in Hiram]

What I think 20 inch wheels are bad for is fast bikes-- whatever kind. They are fine for slow bikes, just like 6 inch solid wheels work fine for shopping carts.

But the only reason they seem to interest you guys is that they help you go faster (on a bike that's less suitable for speed).

My 20" bike is slower than my 26", the difference is in quickness and hill climbing grunt rather than speed. The 20" bike also is easier on the battery and has significantly more range on the same pack, albeit that is mostly due to lower speed.

There is a difference between an electric assisted bicycle and an ultralight electric scooter/motorcycle that happens to have pedals more as a legal fig leaf than anything else and the engineering compromises are going to be different for the two machines.

 

[Punx0r]

Anyone claiming there is no disadvantage to a small wheel needs to compare it directly to the same bike with a 26" wheel before a valid comparison can be made. If, instead they say something like "I accept small wheels carry some inherent disadvantages, but for my application that is an acceptable compromise when other factors are considered" then that is fine.

 

[Joachim]

the best wheel size is the size that fits the frame :lol:

I,like the bigger wheel size @ speeds above 30mph

I ride a mtb with 29inch tires and i like to have more torque from a rolling start and death stop....will a 26inch
wheel give me these things without wheelspin are lift up the front?dont like wheelspin are wheelies(you dont move forward if the tire spins are the front lift up in wheelies...waste of energy ).

 

[dogman dan]

I'm particularly sensitive to a harsh ride. I destroyed my lumbar disk close to 30 years ago. So my commuters I rode 30 miles a day had to have suspension.

But now, having lengthened the bike, I find this 20" back wheel does not give me a harsh ride at all, or skitter around with poor traction. No, it's not a scooter wheel, but notice the striking similarity in frame geometry to the scooter wheel bikes being praised in this thread. That's no coincidence!!! I Noticed success when I saw it. But,,, for high speed use I would want more tire back there than a 2".

What I'm trying to say is there is more to it than just wheel size. Where that wheel is located makes a huge difference. small wheel on the right frame geometry is the key to a good ride.



This bike though, this DID give me a harsh ride.

 

[slowhands]

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.

.....

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.

Today I changed a solid 10mm axle that was bent. I guess the good news is it did not break. But it was bent so bad the bearings were binding. I thought it was the brakes dragging, but no, bent axle. This was on a full suspension mountain bike that I suppose did its fair share of potholes and rocks. It was some off brand, so maybe cheap steel in the axle too. Anyway, it sure was bent.

But this was not an electric bike, just a much used/abused mountain bike. It turns out my local bike shop does not carry axles, he said too many types they just special order them. So, I tore down a solid axle from a 24" wheel. I end up with so many 24" bikes they get to be donors. I reserve the 20 inch wheels for shopping cart trailers, they work great for that. LOL

The moral of the long story is I'm sold on stronger axles, bring on the 12mm axles. Until ebikes become a big enough market though, I don't know if anyone will build a standard axle and torque control that will work for really high power. Frame mounting must be stronger too.