Circumference ?

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XTINCT

XTINCT

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Here's one for you tech heads. Answer this. When calculating the circumference of your Commando wheel (required reference to Commando), Do you figure the radius to the tire edge as in figure A or to the ground as in figure B. Have at it.
 

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I would use A for circumference and B for torque.

I had to download the attachment to open it.
 
Neither, I calibrate using GPS doing a 10 mile run and compare to the bicycle speedo and adjust the circumference so the distance on the bicycle speedo equals the GPS. It does not match either A or B.
 
I mark the tyre and the road and push the bike a set number of wheel turns, mark the road again, measure the distance between the marks on the road and divide by the number of wheel turns.
 
XTINCT said:
Here's one for you tech heads. Answer this. When calculating the circumference of your Commando wheel (required reference to Commando), Do you figure the radius to the tire edge as in figure A or to the ground as in figure B. Have at it.
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For what purpose are you wanting to know the tire radius? Gearing, bike speed calcs or what?
 
I just lift the wheel off the ground and use a tape rule around outer edge of tyre. My cycle speedo set using that method agrees with a GPS speedo.

Ian
 
Triton Thrasher said:
I mark the tyre and the road and push the bike a set number of wheel turns, mark the road again, measure the distance between the marks on the road and divide by the number of wheel turns.
Click to expand...

If you are trying to calibrate a Speedo, or calculate speeds for gearing, I would use Triton's method with this modification:

Sit on the bike to load the tire while moving the set number of wheel turns.

Otherwise, sit on the bike and have someone measure the distance from the axle center to the ground ..... use this measurement as the tire radius.

Slick
 
Triton Thrasher said:
I mark the tyre and the road and push the bike a set number of wheel turns, mark the road again, measure the distance between the marks on the road and divide by the number of wheel turns.
Click to expand...

The old school ways are the best o_O you might even check your tyre pressure and have someone do the marks whilst you sit on it!
 
Me? I just use the published data, knowing whateverinthehellitis I’m trying to calculate, that this is close enough.

Circumference ?


https://www.avontyres.com/en-us/tyre-details/?cartype=motorcycle&id=59

Done it for decades, car, truck, bike tires
 
You really need to use the circumference of the tyre, Avon quoted in the 1970s on their own tyre brochure for roadrunner tyres if I remember , for 18 and 19 inch tyres a difference of only 200 mm it’s that close.
 
Bernhard said:
You really need to use the circumference of the tyre, Avon quoted in the 1970s on their own tyre brochure for roadrunner tyres if I remember , for 18 and 19 inch tyres a difference of only 200 mm it’s that close.
Click to expand...

You might want to check that! 200mm = 7.874016"
 
Xtinct still has not revealed the reason for asking the question. It still holds true that diagram A is the correct one to use for calculating the circumference of the circle. Whether it provides the answer required for the intended task is another question completely.
 
I was never good at geometry. If I wanted to know the circumference of, say, an Avon 4.10/19 Road Rider, I'd post, "What's the circumference of an Avon Roadrider 4.10/19?" on this forum! I suspect the answer would show up in a few hours :)
 
MexicoMike said:
I was never good at geometry. If I wanted to know the circumference of, say, an Avon 4.10/19 Road Rider, I'd post, "What's the circumference of an Avon Roadrider 4.10/19?" on this forum! I suspect the answer would show up in a few hours :)
Click to expand...

More likely than not many answers would appear and you would have to decide which one you liked.
 
MexicoMike said:
I was never good at geometry. If I wanted to know the circumference of, say, an Avon 4.10/19 Road Rider, I'd post, "What's the circumference of an Avon Roadrider 4.10/19?" on this forum! I suspect the answer would show up in a few hours :)
Click to expand...
26" (published diameter) x 3.1416 = 81.68"
 
rvich said:
Xtinct still has not revealed the reason for asking the question. It still holds true that diagram A is the correct one to use for calculating the circumference of the circle. Whether it provides the answer required for the intended task is another question completely.
Click to expand...

Perhaps he is trying to find out how long a set of wheel bearings will last, in kilometres ? It might be before he runs out of petrol.
 
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