2.50/17 38L front & back

[meuhey]

I weight 200lbs can I use such a setup on my ct125?

 

[SneakyDingo]

Why do you want to? There are many reasons not to use that setup and multiple alternatives, many of which are easier and safer to install and acquire.

Keep in mind, your gear, accessories and cargo add to the carrying weight of the bike. Most of the weight of this bike is carried by the rear wheel. With that, I give an an Engineering answer: there are weight scales you can buy for cheap that go up to 500 lb. Place the rear tire on the scales, hop on the bike and see what they say, and if it's less than ~291 lbs then the engineer's answer is, "it's within spec."

 

[Happy Campa]

I think it's a good question. Those tires would have less rotating mass. I am curious as well.

 

[SneakyDingo]

Those tires would have less rotating mass.

I figured someone might make a statement about weight; the other is gearing affecting tire rollout (gearing is solved with an aftermarket sprocket).

There's been some looking into the weight of tires before. The 2.5x17's that I've looked up in the past are somewhere in the range of 4.5 lb to 5.0 lb. The 2.75's are in the range of 5.2lb to 6 lb. There's also a fairly decent amount of variation in actual tire weights with motorcycles, particularly off road tires. The generalized comparison case here would be SR244's vs. SR241's (since a 2.75" SR244 doesn't exist), which would be 4.9 lb vs. 5.9 lb (delta of 1 lb)

It's also worth remembering remember that the wheel is the sum of all its parts. I have a JTR sprocket here that's almost the same size as the OEM one, and it's 2 lbs heavier than the OEM sprocket. Additionally, the OEM 2.75" inner tubes are 3 oz lighter than the double tough tubes in the 2.25-2.5" size. So the rotational mass will depend on the sprockets and the inner tubes as well, assuming we're all using roughly the same wheels.

Tire research for bicyclists have done to death the impact of additional rotating mass (e.g. Wired even had an article, and that article is newer than the research - I can find a link if I have to, but it's not a good use of my time). Generally speaking, the mathematicians approximate that the weight of the tire is the equivalent of 1-2x the weight on the frame - that is, at worst a tire that's 1 lb heavier is the equivalent of riding a frame that's 2 lbs heavier. That also applies to cars.

So looking at that potential equivalent weight savings of 2.5 lbs total across those tires, doubling it to 5 lbs savings if we're considering the not-that-accepted-but-acknowledged-as-possibly-true 2x factor.

But OP is a 200 lb rider. Hydration alone will account for 1-2 lb weight fluctuation. The difference between my heavy "winter" and my light "summer" gear is 3 lbs.

Unless you're a superlight rider, the savings from having 2.5" tires instead of a 2.75" tire is unlikely to add up to more than losing some weight. Now, if you're like DaBinChe, who has shared some of this data and apparently weighs something like 120 lbs, then I'll say... you probably should consider it. But that's also well within the tire's load rating.

 

[Happy Campa]

I figured someone might make a statement about weight; the other is gearing affecting tire rollout (gearing is solved with an aftermarket sprocket).

There's been some looking into the weight of tires before. The 2.5x17's that I've looked up in the past are somewhere in the range of 4.5 lb to 5.0 lb. The 2.75's are in the range of 5.2lb to 6 lb. There's also a fairly decent amount of variation in actual tire weights with motorcycles, particularly off road tires. The generalized comparison case here would be SR244's vs. SR241's (since a 2.75" SR244 doesn't exist), which would be 4.9 lb vs. 5.9 lb (delta of 1 lb)

It's also worth remembering remember that the wheel is the sum of all its parts. I have a JTR sprocket here that's almost the same size as the OEM one, and it's 2 lbs heavier than the OEM sprocket. Additionally, the OEM 2.75" inner tubes are 3 oz lighter than the double tough tubes in the 2.25-2.5" size. So the rotational mass will depend on the sprockets and the inner tubes as well, assuming we're all using roughly the same wheels.

Tire research for bicyclists have done to death the impact of additional rotating mass (e.g. Wired even had an article, and that article is newer than the research - I can find a link if I have to, but it's not a good use of my time). Generally speaking, the mathematicians approximate that the weight of the tire is the equivalent of 1-2x the weight on the frame - that is, at worst a tire that's 1 lb heavier is the equivalent of riding a frame that's 2 lbs heavier. That also applies to cars.

So looking at that potential equivalent weight savings of 2.5 lbs total across those tires, doubling it to 5 lbs savings if we're considering the not-that-accepted-but-acknowledged-as-possibly-true 2x factor.

But OP is a 200 lb rider. Hydration alone will account for 1-2 lb weight fluctuation. The difference between my heavy "winter" and my light "summer" gear is 3 lbs.

Unless you're a superlight rider, the savings from having 2.5" tires instead of a 2.75" tire is unlikely to add up to more than losing some weight. Now, if you're like DaBinChe, who has shared some of this data and apparently weighs something like 120 lbs, then I'll say... you probably should consider it. But that's also well within the tire's load rating.

I love nerding out on stuff like this.

 

[SneakyDingo]

You should definitely pick @m in sc's brain then, he's got lots of smarts rattling around up there.