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I currently ride 25mm Conti GP4000 II tires on my DA C24 rims. I've been riding 25mm tires for a long time, and like the smooth roll and comfortable feel of the 25mm over the 23mm. I'm 145, so a 23 seems to bounce me around a lot more on rough pavement.

I just ordered a set of FLO 30 wheels because I want to try out a wider rim. I understand that wider rims are more comfortable and offer more control. Here's my question: is a 23 or a 25mm tire more appropriate on the wider rim? The rim measures 19.4mm internal and 24mm external.

I understand that a 25mm tire rolls better and is more comfortable but is less aero. I've heard mixed reports of whether a 23mm on a wide rim "feels" like a 25mm on a standard rim, and whether a 25mm on a wide rim feels squashy. Also, I've heard that some frames just don't have enough clearance for a 25mm on a wide rim because it balloons out to 28 or 30mm.

I suppose I could try a pair of 23mm tires, and see how they feel, but if I don't like them, it seems like a waste of money.
 

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Is your clearance tight right now? Yes, your 25mm tire will be effectively wider on the wider rim, but not as dramatically as most have been led to think. I run 28mm tires. When I went from 15mm to 17mm rims, my 28mm tires expanded to 29mm. I expect that your 25mm tires will expand to 27mm at most.

Keep in mind that unless your clearance is extremely tight now, you probably won't have any problems. While the wider rims will tighten your clearance, the wider rims will also be stiffer, so they will be less likely to flex and cause rubbing against the stays.
 

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Just put the 25's that you are riding now on the new wheels and if they fit, ride 'em. You can always down size later, but you probably won't want to.
 

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Less aero? Not with a wider rim. If you can fit them, keep it at 25's. The better ride quality will help you get faster. Great choice on the wheels, by the way!
 

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I think you should be weighing 25 vs 28, not 23 with an internal width that wide. 23 sounds like danger to me, just begging for a pinch flat.
 

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Keep in mind that unless your clearance is extremely tight now, you probably won't have any problems. While the wider rims will tighten your clearance, the wider rims will also be stiffer, so they will be less likely to flex and cause rubbing against the stays.
My understanding is that stiffer rims are more likely to rub.

Debunking Wheel Stiffness - Slowtwitch.com

As you climb on an aluminum rim and rock the bike back and forth, the bottom half of the rim tends to follow the road. The rim bows to comply with your pedaling. The top half of the rim tends to stay relatively straight between the brake pads. If someone’s wheel does NOT rub their brakes, they often assume it’s because the wheel is stiff – or perhaps that the wheel and frame are both stiff. In reality, it’s likely that the rim is not very stiff, regardless of anything else.

https://www.bikeschool.com/blog/the-unbearable-stiffness-of-being-wheel-stiffness-explored/

3) A stiffer, deeper profile rim, especially when paired with bladed spokes, can give the rider the perception of flex, even though the laterally stiffness of the wheel is high. As the rest of the bicycle deflects under high lateral loads (such as out of the saddle sprinting), the wheel resists lateral deformation, resulting in contact between the brake pads and the wheels. This brake pad contact can be detrimental to efficiency.
 

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I think you should be weighing 25 vs 28, not 23 with an internal width that wide. 23 sounds like danger to me, just begging for a pinch flat.
An installed tire on a wider rim will be wider and slightly taller than if it were installed on a narrower rim. I am not sure why it would then somehow be more prone to pinch flats.
 

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Key word here is "rim". Wheel stiffness depends on the whole system: Rim, spokes and hub.
Yes, that's correct, and that is what I meant, a stiffer wheel is more likely to rub. Both those links explain things, and the explanations seem pretty factual to me.
 

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I I'm 145, so a 23 seems to bounce me around a lot more on rough pavement.
The only reason the 23s bounced you around is because you over-inflated them. At your weight they would not be a problem, though certainly the 25s will be more comfortable. The reported "feelings" of wider rims is (if anything) about making the tire wider, nothing more. If your frame will take a couple more mm of tire width, wider rims are fine. And 2 mm would be the most you would likely see.
 

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