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  1. #1
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    Smallest practical wheel size?

    I've got a cheap A-Bike knock-off with 6" wheels. It's ride-able on smooth surfaces, but you feel every crack in the pavement. Gravel roads or other loose pavement are out of the question.

    On the other hand, my Strida with 16" wheels is fine on gravel and every other road surface I've come across.

    Between those ranges, what is the smallest PRACTICAL wheel size for typical city use (mostly paved, but with the occasional rough patch)? Is 6" even usable with perhaps a wider tire or some kind of suspension?

    Looking for replies from people who actually own and ride on smaller wheels.

  2. #2
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    In general I think that wheel size is much much less important than people think it is. People think that since drastic changes in wheel size result in drastic changes in appearance, it should also indicate drastic changes in rideability. I believe this is a misconception similar to the misconception that small wheels require you to pedal faster. People that understand gearing know that small wheels do not necessarily require you to pedal faster, just that you need to compensate the gearing. Likewise, I believe that small wheels do not drastically affect ride quality as long as they are compensated for elsewhere.

    In my opinion the only disadvantage of small diameter wheels that can't be compensated for by other means is the tendency of the wheel to get stuck in cracks. If the diameter is smaller than the cracks then this becomes a problem of safety. If the diameter is bigger then the crack then this becomes a problem of efficiency. Everything else can be compensated with suspension, longer wheel base, etc. For example, look at cars. Despite wheels of around 20 inches in diameter, they seem to manage fine at extremely high speeds on extremely poor roads. They compensate for the small diameter with both a longer and wider wheel base and a sophisticated suspension system.

    Thus, neglecting efficiency, the smallest practical wheel size is slightly larger than the biggest crack you plan to encounter. I think six inches would be fine in most situations if you had wide tires, good suspension, and a long wheel base. Of course, these things would make the bike larger and heavier, somewhat negating the advantage of the small wheels.
    Last edited by makeinu; 09-14-07 at 12:35 PM.

  3. #3
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    Quote Originally Posted by makeinu View Post
    In general I think that wheel size is much much less important than people think it is.
    Not me, I'm with you on this one.

    ... smallest practical wheel size is slightly larger than the biggest crack you plan to encounter.
    Good point, "smallest practical" depends on what you're riding on. 90% of my riding is smooth pavement, yet I live on a gravel road. So however small I go, I need the widest practical tyre. What kind of rubber comes on the CarryMe?

    Additionally, the biggest BUMP you might encounter is a factor as well - if you can't avoid it or unweight the front wheel over something. Last night I was turning tight figure-eights in my driveway to show off the A-Bike to some friends, and suddenly the front wheel just seized as solidly as if I had hit the brake.

    I kid you not: The A-Bike choked on a small pine cone.

  4. #4
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    Quote Originally Posted by lee_rimar View Post
    I kid you not: The A-Bike choked on a small pine cone.
    Honest - I didn't do it on purpose!

  5. #5
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    Quote Originally Posted by Pine Cone View Post
    Honest - I didn't do it on purpose!
    I figured it was your evil twin.

  6. #6
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    Quote Originally Posted by lee_rimar View Post
    Not me, I'm with you on this one.

    Good point, "smallest practical" depends on what you're riding on. 90% of my riding is smooth pavement, yet I live on a gravel road. So however small I go, I need the widest practical tyre. What kind of rubber comes on the CarryMe?

    Additionally, the biggest BUMP you might encounter is a factor as well - if you can't avoid it or unweight the front wheel over something. Last night I was turning tight figure-eights in my driveway to show off the A-Bike to some friends, and suddenly the front wheel just seized as solidly as if I had hit the brake.

    I kid you not: The A-Bike choked on a small pine cone.
    I doubt the gravel on your road is much bigger than 1" in diameter. If the machine is otherwise optimized, a 6" diameter wheel should easily be able to roll over things smaller than 3" or so. I don't believe the issue of your imitation A-bike choking on a pine cone is inherently tied to wheel diameter. A basketball rolled along the ground at speed can often plow over a street curb. Monster Trucks climb over obstacles approaching their wheel size. There are other factors at play. Of course, efficiency is another story, but lots of popular bike improvements sacrifice efficiency (brakes, hub gears, etc).

    The width of the Carryme's tires are 1.5". Not very wide, but I believe the wheelbase is much longer than the A-bike.

  7. #7
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    Quote Originally Posted by makeinu View Post
    I doubt the gravel on your road is much bigger than 1" in diameter. If the machine is otherwise optimized, a 6" diameter wheel should easily be able to roll over things smaller than 3" or so...
    Big difference: A fixed obstacle as part of solid surface is not the same as a loose surface made up of lots of little bits. The small, short, high pressure (90 psi) contact patch of the A-Bike's 6" tire moves the gravel instead of the bike. The longer, lower pressure (60 psi) contact patch of the Strida's 16" tire rolls over the gravel.

    In short: The Strida is ride-able on gravel and the A-Bike isn't.

  8. #8
    Senior Member geebee's Avatar
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    Another factor to consider is that below 16" the range of tyres is not that great.
    It's hard enough getting decent perfomance 16" tyres in my City.
    Greenspeed GLR trike
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  9. #9
    Small wheels ARE better! OldiesONfoldies's Avatar
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    I tour with 20" wheels - find that its the most optimum size for performance and folding. But the little 8" wheels on the Carry Me surprised me. Would you believe it can be ridden on a Malaysian oil plantation unsealed road? Its possible and was attempted successfully recently by one of my crazy friends...

    Here's proof -



    Guess its the rider, not the bike at the end of the day!

  10. #10
    Smiling and Waving thebikeguy's Avatar
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    I'm sorry but anything with smaller tires than 20" feels like a child's toy to me.Like if I crank too hard something will snap or bend.Not so good if you have a longer commute.

  11. #11
    Small wheels ARE better! OldiesONfoldies's Avatar
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    Quote Originally Posted by thebikeguy View Post
    I'm sorry but anything with smaller tires than 20" feels like a child's toy to me.Like if I crank too hard something will snap or bend.Not so good if you have a longer commute.
    Tell that to Dr Alex Moulton.... not sure if he shares your view

  12. #12
    Smiling and Waving thebikeguy's Avatar
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    The Moulton is definately strong enough.It's built like a real bike.Same as the Twenty,good solid bike.But still not so great on a longer tour.Those 16" wheels just aren't as smooth as the 20".And the prices for these bikes are starting to get crazy.

  13. #13
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    I've got 16" wheels on my giatex. The advantage I've found for the smaller wheels are that it seems a bit easier to get up steep hills. Maybe that's just my imagination, though. I've also found that acceleration is faster (which is bad on a bike where most of the weight is in the back. I've almost fallen over backwards a few times). I think if my bike had better gearing and some form of suspension, the wheels would be fine.

  14. #14
    Eschew Obfuscation SesameCrunch's Avatar
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    Quote Originally Posted by thebikeguy View Post
    I'm sorry but anything with smaller tires than 20" feels like a child's toy to me.Like if I crank too hard something will snap or bend.Not so good if you have a longer commute.
    Ummmm......, I'm trying to figure out how anything on a bike would be more prone to snapping just because the wheels are smaller....

    I'd grant you that the ride is twitchier, but that doesn't have anything to do with strength or durability.

  15. #15
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    A well engineered 16" wheeled bike can be as tough and durable as any other. You'd have to think carefully about going fast off road, but you would on a 700c racing bike too. I think we should be careful about making wrong assumptions about children's toys and small wheeled bikes. Maybe they don't appeal to everyone's idea of what a bike should be. That's fine, but it doesn't mean they aren't as tough as old boots. I met an old guy with an eight year old Brompton the other day out in the middle of nowhere. He'd got on a bus with it in the morning, travelled twenty five miles, and was riding it home. He said he did this about three times a week and that he had put over 15000 miles on the bike. He was at least 65 years old. I think the bike will outlast him easily.
    “Get a bicycle. You will not regret it, if you live." - Mark Twain

  16. #16
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    In high school I used to ride a Honda scooter with 90/90-10 size wheels (16") and it was no problem. Even took it up to 80 mph a few times and the ride was pretty stable. Though the wheels were much wider than bicycle wheels.

    I think that 16" is the smallest you want to go. Even with a lot of gears, 8" wheels won't get you very fast.

  17. #17
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    Based on my experience with 16" Schwalbe Big Apples I'm inclined to think you could make something fairly useful using their two smaller sizes - 50-203 (12 x 2.00) & 50-254 (14 x 2.00) The 12" is rated for a 70 Kg load.

    I'm pretty fussy about tires, and don't want to spend my ride paying close attention to road surfaces, so thats as small as I'd go. For tires that small, suspension would be a big plus, especially if it were part of the folding system.

  18. #18
    Senior Member cyqlist's Avatar
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    Quote Originally Posted by MnHPVA Guy View Post
    Based on my experience with 16" Schwalbe Big Apples I'm inclined to think you could make something fairly useful using their two smaller sizes - 50-203 (12 x 2.00) & 50-254 (14 x 2.00)
    Hey, thanks for that info. I did not know those were available in the 203 size - a possible future option for my Mobiky, though I'd prefer not to go narrower than the original 62-203 (12½ x 2¼) tires that came on the bike. One thing the Mobiky has is lots of clearance for even wider tires if they were available, and no caliper brakes to get in the way.

    I think the 203mm rim size may be the smallest practical size for building up a traditional spoked wheel, which allows the use of available hub gears and hub dynamo. Has anyone seen a smaller wire spoked wheel?

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