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# Determining weight capacity of tires

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# Determining weight capacity of tires

06-01-23, 02:10 PM
#1
tiger1964
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Determining weight capacity of tires

I have a friend who wants to repurpose a bike as an errands bike; he has plenty of shops in a tolerable radius. The bike is a custom-built (by Bilenky) upright tourer and for various Euro trips he has moved on to other bikes. The Bilenky looks right, and is equipped with a Rohloff hub (for this entire bike, \$\$\$ doesn't begin to describe it, more like \$\$\$\$\$\$\$); plenty sturdy and has all the right bits for brakes, etc. And he wants to electrify it. So far -- cool. Alas, he's worried about weight capacity: the bike is something like 38LB and you have to add in the electric conversion, plus the cargo load, and he's a pretty big guy. So, before he starts throwing money at the project, is there a way to determine what the weight capacity is of a given tire? For instance, he rides on Continental's GP5000 and also Gatorskins on other bikes, so I hit their website -- all kinds of info but no max weight capacity (like a car tire would). The bike is on 28mm tires now and a rudimentary check shows 35mm no problem, not so sure about 42mm. Any thoughts on how to calculate whether he can do this?
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06-02-23, 11:31 PM
#2
Leisesturm
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It really wouldn't be the tires that have a weight capacity limit (GVWR) it would be the wheels. HOW does he plan to equip the bike frame to carry the weight of ... errands? I don't know seems like an easier solution is simply to buy a trailer. I also think some e-bike rated tires like Marathon Plus would be part of the upgrade. Their GVWR is irrelevant also but the Conties are deffo not up to the demands of being thrashed by an e-assist.
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06-03-23, 04:09 PM
#3
tiger1964
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Originally Posted by Leisesturm
It really wouldn't be the tires that have a weight capacity limit (GVWR) it would be the wheels. HOW does he plan to equip the bike frame to carry the weight of ... errands? I don't know seems like an easier solution is simply to buy a trailer. I also think some e-bike rated tires like Marathon Plus would be part of the upgrade. Their GVWR is irrelevant also but the Conties are deffo not up to the demands of being thrashed by an e-assist.
Thanks, food for thought, I am passing this along to the bike's owner. Unsure how to calculate a wheel's max weight capacity. Use to p*ss him off I could suggest Campagnolo high-flange and tubulars...
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06-03-23, 07:12 PM
#4
ThermionicScott
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For a first-order approximation, you could use one of those online "15% drop" calculators to figure out how much pressure you'll need for the load, and then check if that is over the maximum pressure rating of the tires.
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06-05-23, 09:07 AM
#5
tiger1964
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Originally Posted by ThermionicScott
For a first-order approximation, you could use one of those online "15% drop" calculators to figure out how much pressure you'll need for the load, and then check if that is over the maximum pressure rating of the tires.
OK, you lost me there. I did a search and found a % calculator, alright, but I am not sure what values you're suggesting I put into it.
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06-05-23, 11:06 AM
#6
ThermionicScott
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Originally Posted by tiger1964
OK, you lost me there. I did a search and found a % calculator, alright, but I am not sure what values you're suggesting I put into it.
This one is as good as any. Just pick the tire width and plug in the total weight of the rider, bike, and gear: https://www.renehersecycles.com/tire...re-calculator/
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06-05-23, 12:58 PM
#7
tiger1964
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Originally Posted by ThermionicScott
This one is as good as any. Just pick the tire width and plug in the total weight of the rider, bike, and gear: https://www.renehersecycles.com/tire...re-calculator/
Now that makes a lot of sense - thanks! Passing this along...
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06-06-23, 10:47 AM
#8
Leisesturm
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Just saying, those calculators ... any of them have input for multiple riders? Or a 'single rider' that weighs 350lbs+. (tandem team)? Heck there are plenty of triplets on the road. At least a dozen Quads. They all use regular tires. I've seen a 10 man bike that used moped tires but it could just as easily have used a standard bike tires. They would have handled the 2,000lb(!!) load just fine. I ride a tandem, with and without, my Stoker daily which is a 150lb weight difference for the tires. Even if I wanted to, there is no practical way for me to adjust the tire pressure for the load change when the Stoker gets off. And I have found that, in practice, it's irrelevant. Inflated to Max PSI, there is no difference in ride quality or anything else when 150lbs. are suddenly taken out of the equation.

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