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Front & rear tires are same size as the CBR250R, which are also the same sizes as the tires supplied on the Ninja 300. Not sure why you consider this rear tire size to be "dinky", as it is the appropriate tire size for all these bikes. When motorcycle manufacturers specify tire sizes for a given bike, it has nothing to do with how it "looks" on the bike. Manufacturer specified tire sizes are based on the performance parameters of the motorcycle, nothing more.
 

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Front & rear tires are same size as the CBR250R, which are also the same sizes as the tires supplied on the Ninja 300. Not sure why you consider this rear tire size to be "dinky", as it is the appropriate tire size for all these bikes. When motorcycle manufacturers specify tire sizes for a given bike, it has nothing to do with how it "looks" on the bike. Manufacturer specified tire sizes are based on the performance parameters of the motorcycle, nothing more.
Correct, they do optimize the tires for how well it suits the bike, it basically NEEDS to complement the bikes performance while still staying within a price range suitable for a bike like this. But of course some people will need to 'upgrade' the tires to their liking over time.

Any tires you think would be great for the CBR300?
 

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Any tires you think would be great for the CBR300?
Depends on what kind of riding you plan on doing.

For all around street use, the stock IRC Road Winners are decent tires for the money. I managed to get 9000 miles from the original IRC's, which are bias-ply construction, on my 250R before they were worn out. Based on the 300R photos from the motorcycle show in China, it looks like Honda will be fitting the bike with the IRC Road Winners as well. Of course that could change by the time actual production begins, assuming they haven't already started building the 300R's.

Michelin is due to release their new (and highly anticipated) Pilot Street Radials in the U.S. soon. These tires are being made in sizes specifically for the Honda CBR250R, CBR300R, and Kawasaki Ninja 250 & 300. I'm planning on fitting a set of these Pilot Street Radials on my CBR250R next season.

There are a number of other performance tire options from Bridgestone and Pirelli that are well suited to track use for these bikes. The trade off with these "sticky" tires is that they do not last very long, so their cost per mile for street use is fairly high compared to other aftermarket tires that are intended for street/touring use.
 

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Discussion Starter #5
Front & rear tires are same size as the CBR250R, which are also the same sizes as the tires supplied on the Ninja 300. Not sure why you consider this rear tire size to be "dinky", as it is the appropriate tire size for all these bikes. When motorcycle manufacturers specify tire sizes for a given bike, it has nothing to do with how it "looks" on the bike. Manufacturer specified tire sizes are based on the performance parameters of the motorcycle, nothing more.
good to know. just wondering if its any larger because of the extra displacement.
 

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My guess is that the nominal width and aspect ratio coming from factory is already the optimal size for how the bike comes. It's not until you start making enough changes to the performance where a plus size would make a difference.
 

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My guess is that the nominal width and aspect ratio coming from factory is already the optimal size for how the bike comes. It's not until you start making enough changes to the performance where a plus size would make a difference.
Exactly. From the factory it's already configured as best as it can be for what the bike is and what it's pricing is, only so much they can do.
 

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do people who heavily modify their 250s keep the stock tire width?
I don't believe there is such a thing as a "heavily modified" CBR250R. That said, there are a few misguided owners who for whatever crazy reason think that bigger is better when it comes to tire sizes on the 250R. What those guys fail to understand is that the rim width of the front & rear wheels are designed for the stock tire sizes. Bigger tires on a small bike like the CBR will actually result in slower turn in, as well as an overall feeling of sluggish handling.

A side note regarding tires: Michelin has just released their new Pilot Street Radial tires, which are being made in stock replacement sizes specifically for the Honda CBR250R & 300R, and the Kawasaki Ninja 250 & 300. Prior to these new Michelins, no tire manufacturer has made radial tires for this small sportbike market segment.
 

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Discussion Starter #12
What about those who dedicate their 250 to pure track duty? Is the OEM size usually kept?

(just trying to learn here)
 

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What about those who dedicate their 250 to pure track duty? Is the OEM size usually kept?

(just trying to learn here)
Those who know what they are doing will stay with stock sizes (of course using tires with stickier compounds). Some racers will even go one size smaller on their "track only" 250's. It's still a low horsepower bike. Bigger tires on a 25 HP bike are not going to make it faster. The opposite is true, it would be slower on a race track with larger than stock size tires.
 
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Those who know what they are doing will stay with stock sizes (of course using tires with stickier compounds). Some racers will even go one size smaller on their "track only" 250's. It's still a low horsepower bike. Bigger tires on a 25 HP bike are not going to make it faster. The opposite is true, it would be slower on a race track with larger than stock size tires.
I guess going upsize on such a low displacement bike would make it slower and possibly make it harder to flick around turns.

Interesting how soem guys go one size smaller, I would be afraid for taking away from the traction/contact patch. I guess for track only it makes sense though, you wouldn't have to deal with loose gravel or even rain.
 

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I guess going upsize on such a low displacement bike would make it slower and possibly make it harder to flick around turns.

Interesting how soem guys go one size smaller, I would be afraid for taking away from the traction/contact patch. I guess for track only it makes sense though, you wouldn't have to deal with loose gravel or even rain.
That would be scary rather have more contact but obviously not to much that you're going slower than you need to be, just have to find that magic size.
 

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... just have to find that magic size.
Which for CBR250R's and CBR300R's operated on streets & public roads, the ideal tire sizes are the very same sizes that Honda specifies and supplies as OEM from the factory.
 
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Discussion Starter #17
so I'm going to continue to extract as much knowledge from you as I can while I can :p

how do manufacturers determine tire size and width?
as the horsepower goes up would it be safe to say the tire width usually goes up as well?
 

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so I'm going to continue to extract as much knowledge from you as I can while I can :p

how do manufacturers determine tire size and width?
as the horsepower goes up would it be safe to say the tire width usually goes up as well?
The tire sizes for a given motorcycle are determined by a number of factors, including curb weight, horsepower, type of use, frame geometry, etc... it's safe to say that quite a lot of R&D testing goes into what a manufacturer will ultimately choose in the way of tire sizes, rubber compounds, construction (Radial or Bias Ply), and tread design for a particular motorcycle.

Rear tire sizes do increase significantly on sport bikes with higher horsepower and overall performance, while front tire sizes will typically only vary slightly.
 
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Which for CBR250R's and CBR300R's operated on streets & public roads, the ideal tire sizes are the very same sizes that Honda specifies and supplies as OEM from the factory.
Yeah thats basically what i was trying to get at. Of course someone can go about doing their research to find out what is better but nothing beats what the manufacture that made the bike recommends. They did put in a lot of money into things like that after all.
 

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I heard that skinnier rear tires improve your ability to tip into turns, but i suppose you dont get as much of a lean angle? could anyone clear that up?

too much internet reading....
 
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