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Old 07-14-07, 09:11 AM   #1
pengyou
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Rated weight capacity of a bicycle

What is the usual weight rating of a cheap bicycle? What determines the carrying capacity for a bicycle - i.e. what is the weak link in the chain? Is it the tires? wheels? the frame itself?
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Old 07-14-07, 09:29 AM   #2
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The limiting factor is the rider's ability to actually turn the pedals. There are some guys in the clydes forum (of which I'm a member) who are well over 400/500lbs and have no problem riding bikes. There are guys in the car free forum who load their bikes up with their work tools (ladders, tool boxes, etc).
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Old 07-14-07, 09:53 AM   #3
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Thanks! What i want to do after i get my bike converted...is to be able to carry someone on the rear - actually have something mounted over the rear wheel that is comfy and will let a person sit almost indefinitely. I have read on a few sites that tires suffer from heavier weights on a bike. Can I find a tougher tire?
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Old 07-14-07, 12:04 PM   #4
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It's not the tire so much as it's having a strong rim and lots of spokes on the rear wheel. If you check out the Clydesdales/Athenas forum, you will be able to read some great recommendations for strong wheels. Also, I believe that if you have a bike with a steel frame, you can carry more weight. That said, I do carry quite a bit on my aluminum step-through frame.

When you say "converted", do you mean you're getting an Xtracycle or something like that?
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Old 07-14-07, 12:37 PM   #5
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Quote:
Originally Posted by pengyou
Thanks! What i want to do after i get my bike converted...is to be able to carry someone on the rear - actually have something mounted over the rear wheel that is comfy and will let a person sit almost indefinitely. I have read on a few sites that tires suffer from heavier weights on a bike. Can I find a tougher tire?
I believe that is illegal in some places. Check your local laws...
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Old 07-14-07, 01:12 PM   #6
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I've had good luck with Sun rims on a 36 spoke hub using 2mm spokes. With that I can load the back down with a ton of stuff and it doesn't buckle. The classic bicycle wheel really is astonishingly strong for its weight. A well built bike with strong, well-built wheels can haul 500 pounds for as many miles before losing a spoke. Though at some point the frame may snap. Exactly what that point is depends on where the weight is bearing down and how it's balanced, so it's hard to say what any bike's true capacity is. Some bikes tend to be less forgiving about very heavy loads on the front or back. The only bikes I know of that are factory rated for x hundred pounds are some of the Monarch utility bicycles from Europe.
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Old 07-15-07, 10:43 PM   #7
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What happens when a frame snaps? It sounds dangerous
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Old 07-15-07, 10:45 PM   #8
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Quote:
Originally Posted by donnamb
It's not the tire so much as it's having a strong rim and lots of spokes on the rear wheel. If you check out the Clydesdales/Athenas forum, you will be able to read some great recommendations for strong wheels. Also, I believe that if you have a bike with a steel frame, you can carry more weight. That said, I do carry quite a bit on my aluminum step-through frame.

When you say "converted", do you mean you're getting an Xtracycle or something like that?
By "converting" I mean adding an electric motor to the (probably) front wheel. I want to have my internal gear hub in the back so I can still cycle.
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Old 07-16-07, 12:09 AM   #9
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Originally Posted by pengyou
By "converting" I mean adding an electric motor to the (probably) front wheel. I want to have my internal gear hub in the back so I can still cycle.
I see. You might want to take this question to the e-bike forum, if that is your plan. I would not want to lead you astray in any way.
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Old 07-16-07, 05:12 AM   #10
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Quote:
Originally Posted by pengyou
What is the usual weight rating of a cheap bicycle? What determines the carrying capacity for a bicycle - i.e. what is the weak link in the chain? Is it the tires? wheels? the frame itself?
Usually the first signs of trouble you see is spokes will begin to break.

A lot of "cheaper bikes" (that is--those costing up to, oh, say,,,, $1000.00 or so) come with pretty cheap spokes. My personal theory is that bike companies go cheap-***** on the spokes because the spokes aren't big enough to print the spoke-manufacturer's name on big enough that you'd ever notice it.

Generally:
16 ga spokes are most common on better bikes ($500-$1000+).
12 ga is stronger, these are common on lots of cheaper dept-store bikes.
10 ga is strongest; only US company I know of that used them is Worksman cycles, for work bikes. Some Euro work bike companies use them too of course.

Roughly speaking (in terms of cross-section):
12ga is 3X as strong as 16ga
10ga is 5X as strong as 16ga

The reason that "better bikes" use weaker spokes than dept store bikes is because people in bike shops are more concerned with bicycle weights. With dept-store bikes, durability is more of a concern.

16 and 12-gauge spokes are usually freely interchangeable, but you will have to drill out bigger spoke holes for 10 ga in rims and hubs, and some hub flanges aren't big enough to safely do this.
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Last edited by Doug5150; 07-16-07 at 05:22 AM.
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