theoldduffer
1 µW
- Joined
- May 16, 2013
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- 2
I can see some obvious benefits of generally using a larger size wheels on a bicycle, but are there any benefits to using a smaller wheel, say a 20" over a 26"?"
tOD
tOD
Any benefit to going with smaller wheels?
- Thread starter theoldduffer
- Start date
Spacey
100 kW
Yes, stops your Crown motor from going 60mph
theoldduffer
1 µW
- Joined
- May 16, 2013
- Messages
- 2
Spacey said:
And that helps, exactly how?
dogman dan
1 PW
Guess you never went 60 mph on a hundred buck bike from walmart.
A small wheel is a lower gear for a hubmotor. This can greatly effect efficiency, especially if the rider is heavy and the hill steep. Small wheel for the win. More torque in the small wheel. And the same rpm is slower, if 60mph is too scary on your bike.
But a big motor in a 20 inch rim is often radially spoked, and might be weaker than a 26" wheel laced one cross. Regular bike wheels are often laced two cross, and are very resilient and strong. I stick with 26" wheels for riding on dirt or worse than dirt paved roads.
For pedalers, the bigger the wheel the less rolling resistance. Who cares with a powerful motor? But it matters to pedalers. This is why a horse drawn freight wagon used to have a 6' tall wheel.
A small wheel is a lower gear for a hubmotor. This can greatly effect efficiency, especially if the rider is heavy and the hill steep. Small wheel for the win. More torque in the small wheel. And the same rpm is slower, if 60mph is too scary on your bike.
But a big motor in a 20 inch rim is often radially spoked, and might be weaker than a 26" wheel laced one cross. Regular bike wheels are often laced two cross, and are very resilient and strong. I stick with 26" wheels for riding on dirt or worse than dirt paved roads.
For pedalers, the bigger the wheel the less rolling resistance. Who cares with a powerful motor? But it matters to pedalers. This is why a horse drawn freight wagon used to have a 6' tall wheel.
Sigh..
When we're talking about hub motors with a single gear ratio ( that is, direct drive ), the smaller the wheel, the more the torque, but top speed lowers, which can be increased again by adding more voltage.
This can mean for higher continuous power output and dramatically better acceleration in a hub motor.
I have not seen any proof that rolling resistance is better for taller wheels. This is perpetrated by bicyclists, but i have not seen any science done. A smaller wheel has less rotating mass and a lower moment of inertia, these are advantageous.
The taller the wheel though, the better it rolls across imperfections in the road. There is more surface contact with the road.
Radial lacing is not particularly weak when we are talking about a really really small wheel.
When we're talking about hub motors with a single gear ratio ( that is, direct drive ), the smaller the wheel, the more the torque, but top speed lowers, which can be increased again by adding more voltage.
This can mean for higher continuous power output and dramatically better acceleration in a hub motor.
I have not seen any proof that rolling resistance is better for taller wheels. This is perpetrated by bicyclists, but i have not seen any science done. A smaller wheel has less rotating mass and a lower moment of inertia, these are advantageous.
The taller the wheel though, the better it rolls across imperfections in the road. There is more surface contact with the road.
Radial lacing is not particularly weak when we are talking about a really really small wheel.
migueralliart
10 kW
Smaller wheel + HS3540 = WIN too
Oh yeah. Even my HS3648 was a rocket, and that's the worst wind for the job
The magic pie was effin' nuts in a 20". I never knew it's full potential; had to tune the amps down to the point where a mis-movement of the wrist wouldn't throw me off the back of the bike
The magic pie was effin' nuts in a 20". I never knew it's full potential; had to tune the amps down to the point where a mis-movement of the wrist wouldn't throw me off the back of the bike
Spacey
100 kW
Well I will be putting this Crown in a 24inch wheel, even though it's the 65 Torque version I will be running it at 24cell A123 and do not want to be going more than 35mph....just lots of torque muwuhahaha
spinningmagnets
100 TW
Direct-drive (DD) hubs benefit from a 20-inch wheel, due to the higher "magnet speed".
Since geared hubs have the motor spin 5 times faster than the wheel, they might actually be going too fast in a smaller wheel. Whether or not it is too fast would be due to limits such as A) fat laminations, instead of the desireable thin lams (0.50mm vs 0.35mm). B) cheap low-silicon steel in laminations, instead of higher quality steel with high silicon content and few impurities. C) Your controller doesn't handle high electrical frequency well (some do).
Another benefit for 20-inch wheels is when you use the wide heavy-duty wheels, they will accept the 16-inch Pirelli moped tires. Smaller wheels don't handle potholes as well, but on smooth roads, they work well.
Since geared hubs have the motor spin 5 times faster than the wheel, they might actually be going too fast in a smaller wheel. Whether or not it is too fast would be due to limits such as A) fat laminations, instead of the desireable thin lams (0.50mm vs 0.35mm). B) cheap low-silicon steel in laminations, instead of higher quality steel with high silicon content and few impurities. C) Your controller doesn't handle high electrical frequency well (some do).
Another benefit for 20-inch wheels is when you use the wide heavy-duty wheels, they will accept the 16-inch Pirelli moped tires. Smaller wheels don't handle potholes as well, but on smooth roads, they work well.
dogman dan
1 PW
I've not seen the math on larger wheels either. But I've seen the history. Back when everything was horse or man powered, NOTHING had tiny wheels.
Have you ever pushed 20 or 30 tons of gravel or cement around? I garan dog tee you that a fight breaks out over who gets the one wheelbarrow with a bigger wheel.
Does any of this rolling resistance stuff matter when you have more than one horsepower to run your bike. NO. But the torque thing will, with a hubmotor.
But don't try to tell the pedalers to dump their 29er, and go back to 26. They will say hell no.
Have you ever pushed 20 or 30 tons of gravel or cement around? I garan dog tee you that a fight breaks out over who gets the one wheelbarrow with a bigger wheel.
Does any of this rolling resistance stuff matter when you have more than one horsepower to run your bike. NO. But the torque thing will, with a hubmotor.
But don't try to tell the pedalers to dump their 29er, and go back to 26. They will say hell no.
cal3thousand
10 MW
dogman said:
I would have thought that the large wheels back in the day were for the poor road conditions. Smaller wheels not being able to span the larger potholes would get stuck.
Kingfish
100 MW
Random scattered thoughts... It's all about leverage.
History shows that large wheels are better at moving big loads than little wheels - until the advent of iron, steel, roller bearings, gears, and prime movers.
Roman Chariots had smaller wheels for racing... and not too bad for running down gladiators
Stage Coaches had smaller wheels up front for tighter steering and bigger ones in back for load.
The horse drawn mobile artillery cannon had large wheels.
Steam Locomotives have large wheels.
The largest mining trucks in the world use big mombo tires.
The Space Shuttle Crawler had BF'n tractor wheels.
Though my ebike has plenty of torque as a 2WD, I'm considering moving to smaller tires because the frame is so dang high. Not terribly worried about losing 5% of the top-end; speed is wasteful for xCountry.
D'oh it's Millertime! KF 8)
History shows that large wheels are better at moving big loads than little wheels - until the advent of iron, steel, roller bearings, gears, and prime movers.
Roman Chariots had smaller wheels for racing... and not too bad for running down gladiators
Stage Coaches had smaller wheels up front for tighter steering and bigger ones in back for load.
The horse drawn mobile artillery cannon had large wheels.
Steam Locomotives have large wheels.
The largest mining trucks in the world use big mombo tires.
The Space Shuttle Crawler had BF'n tractor wheels.
Though my ebike has plenty of torque as a 2WD, I'm considering moving to smaller tires because the frame is so dang high. Not terribly worried about losing 5% of the top-end; speed is wasteful for xCountry.
D'oh it's Millertime! KF 8)
parajared
10 kW
Run on the same bike, at the same voltage amperage and wattage, my 20" MXUS always runs much cooler than my 26" 9C. Not entirely sure why this is.
I switched my HS3540 from a 26" wheel to a 20" wheel. The difference in acceleration is crazy.I don't worry about overheating anymore either despite running 100v at 90amps and no cooling holes, heat was an issue in the 26" wheel. I have much less issues with the spokes now too. With the 26" wheel I was always battling to keep it true and wobble free and I had some issues breaking spokes. With the 20" wheel I've had no more spoke issues at all so far, wheel wobble is much less pronounced even with loose spokes.
I like the 20" wheels. I'll probably go back to 26" wheels only for the winter so I can use my studded tires.
I like the 20" wheels. I'll probably go back to 26" wheels only for the winter so I can use my studded tires.
Chalo
100 TW
neptronix said:
Lower weight, lower inertial moment, higher strength-- these are all advantages of small wheels. If these advantages outweighed the disadvantages of higher rolling resistance and higher energy losses to bumps, racers would use small wheels.
They don't.
P.S. - I forgot to mention the aerodynamic advantages of small wheels. These are especially significant in the over-20mph range that cycle racers inhabit. They still don't offset the rolling inefficiencies of smaller wheels compared to bigger wheels. Racing cyclists use pretty much the biggest wheels that can be compactly fitted to frames for small people (like cycle racers).
MadRhino
100 GW
Large wheels freeride much faster on a DH track, and they run smoother too.
My favorite size is 28.5" OD (3.0 X 26 tire)
Compromises have to be made though, for fast motors to run cooler.
My cromotors are on 24" wheels, only slow motors do live well in large wheels.
Wheels smaller than 24" are making harsh rides with poor handling on rough terrain, they are good only for the streets.
I could add that ebikes that are built on small wheels are not stealth, and often with wrong geometry.
My favorite size is 28.5" OD (3.0 X 26 tire)
Compromises have to be made though, for fast motors to run cooler.
My cromotors are on 24" wheels, only slow motors do live well in large wheels.
Wheels smaller than 24" are making harsh rides with poor handling on rough terrain, they are good only for the streets.
I could add that ebikes that are built on small wheels are not stealth, and often with wrong geometry.
spinningmagnets
100 TW
It is my opinion that the Tour de France uses full diameter wheels because the manufacturers want it that way. I think that any competitive racing college bicyclist using 20-inch wheels on a recumbent that is fully faired...might do well in those type of races.
Chalo
100 TW
spinningmagnets said:
Today, you may be right, but remember that Le Tour has been happening for over 100 years. The customary wheel size was arrived at by results-based means. Bigger wheels made the bikes heavier and more cumbersome for the tiny men who were the most successful riders, and smaller wheels cost speed by other means.
If you look at racing bicycles since the 1890s, you'll see that tire widths have varied quite a bit according to road surfaces and available tire technology, but wheel diameters have remained very similar-- even though there have been many incompatible rim diameters and tire types within that same general size range.
If so, it would be because of the fairings and despite its small wheels.
Small wheels squander energy at least three ways: They transfer more energy to the rider and bike as shocks by falling into holes more deeply and surmounting bumps more suddenly. They work their rubber harder by flexing it at greater angles of deflection, causing hysteresis losses. And because their tires sink more deeply under the same load, they exhibit higher levels of shear and scrub (therefore friction) within their contact patches.
These kinds of losses are such that when you reduce one, you increase another-- for example, you might use higher tire pressure or a narrower tire to diminish the contact patch, but that would dramatically increase energy lost to shocks and vibration. And of course, any method that successfully reduces total energy loss can also be applied to a larger wheel for even better effect.
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