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Discussion Starter #1
Hey guys, i was wondering what needs to be changed to use a 180/55 back tires and 120/70 front tires. Do i need to change the rims too? and what would be the advantage of using these tires on a 250cc bikes. Or is it better to just change the swingarms and everything with that of a CBR600?

thanks :D
 

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Hey guys, i was wondering what needs to be changed to use a 180/55 back tires and 120/70 front tires. Do i need to change the rims too? and what would be the advantage of using these tires on a 250cc bikes. Or is it better to just change the swingarms and everything with that of a CBR600?

thanks :D
NO! and WHY WHY WHY?

A 140 rear tyre is already stretching it for a 250 single... probably better with a 130 for starters.

You would need a 5.5 or 6.0 inch rear rim to start with.
A 600 swingarm will never fit.

A wide tyre would make a slow bike slower...

And dont ask silly questions on the internet lol.
 

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Oh and welcome to the forum lol.
 

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Discussion Starter #4
sorry if its a silly question. well considering the road conditions over here in jakarta, i wouldn't be looking into speed but more into the looks. I'm considering facelifting the cbr 250 to look like a 600, well, more in the wheel department anyways.

i'm still a newbie on motorcycle world, so mind my poorly educated mind :D

Will the standard swingarm fit 5.5 rear rim? and what about the front rims, do i need to change that too? thanks
 

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Having a chopper, I can't make comments such as: 'why would you ruin a perfectly good motorcycle for appearances sake'...

That said, you can do all kinds of things to a bike platform that it was not intended for but the further you stray from the original the more it's going to cost you.. it might end up cheaper to just get the 600 to begin with :)

(the bike in the photo isn't mine. To the point, I don't want to try and guess how much money was put into that bike to modify it like that ! )
 

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it's a relatively low powered bike as it site, the addition of more rotational mass might make a more significant difference than on a bigger bike. it'd probably be more trouble than it's worth to make the 250 look like a drag 600. might be cheaper to just sell the 250 and get a 600
 

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i was also wanting to put a wider rear tire on my 250, not just for looks but for function. i track my 250 and i havent leaned it all the way over but i can see im almost at the very edge of the tire. a wider and taller tire in the back with less of a football shape and more of a arc shape would allow you to lean the bike over further before you reach the end of the tire. Although i dont think a 180 would fit in the rear i think a 150 or 160 could definitly be squeezed in there
 

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Before Doing any such mods, I would highly suggest doing lots of research. Regardless of what Pontiac Gran Prix commercials said a few years ago... wider is not always better. I would suggest contacting Honda (preferably beyond the dealership level... or at least an engineer or 2) to get an idea of how the bike would be affected. Personally, I would prefer adjustable suspension, but there are ways to achieve that too.

Good luck
Chad
 

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He's Indonesian they do things like that... You should see some of the stuff they have done to the Ninjette....
Op.. it is not really a desirable mod.. expensive and certainly only for looks... Here in Thailand they have used the single sided swing arms and rear wheels but still using a 150 rear tyre.. maybe look at the rear from the 250 hornet.
 

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A tyre feathered to the edges with no chicken strips has far more cred than than a wider tyre with more chicken strips than KFC. ..
and says more about the bike and rider.
 

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A tyre feathered to the edges with no chicken strips has far more cred than than a wider tyre with more chicken strips than KFC. ..
and says more about the bike and rider.
well on my first trip to the track on the 250 i almost got it all the way to the edge maybe 1/4 inch away from the edge. as i get more accustomed to the bike and track and as i start going faster and leaning more i am going to need more tire. I would much rather have alittle wider rear tire that has 1/2"-1" of sissy strips then to go past the edge of a tire that isnt wide enough and go down.
 

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well on my first trip to the track on the 250 i almost got it all the way to the edge maybe 1/4 inch away from the edge. as i get more accustomed to the bike and track and as i start going faster and leaning more i am going to need more tire. I would much rather have alittle wider rear tire that has 1/2"-1" of sissy strips then to go past the edge of a tire that isnt wide enough and go down.
Unless you go up a rim size as well ,that 150 tyre will just fall away at the edges and still land you on your ass as pegs & fairings ground out.
1/4" to go is still a long way at the edge of lean.

You dont need it.. Mr Honda has done his homework.
 

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I agree Aufitt... Tire sizes are specific to a bike for a reason. Not to say they can't be changed, but doing so will (usually negatively) affect the handling. And, unless you really know what you are doing when you start making such modifications, you are drastically increasing your chances of landing on your backside.
Not to say that Honda is perfect, but they have been building bikes since 1948... pretty likely to know what they're doing by now.
Also, if there are a lot of ruts and other such road hazards, you are actually better off with the narrower tire as it will track better. The appropriate changes to make there would be to the suspension. Pretty limited to preload adjustments on the 250R, but a good suspension person can get you correct springs and Racetech can definitely help (especially with the springs and potentially with damping characteristics.
 

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Industry Tire Sizing

Here is the industry tire sizing reference information:

DennisKirk.com - Tire Sizes Explained

The front rim on the CBR250R is 2.75" X 17".

The rear rim is 4.00" X 17".

The allowable tire width range for the front tire is 110 to 140.

That does NOT necessarily mean that a tire wider than 110 is better. There are many other considerations.

The allowable tire width range for the rear tire is 150 - 160.

I'm not sure why Honda paired the factory 4.00" rim with a 140 tire. I do know that there is less than .500" clearance between the factory IRC tire and the chain. A 150 tire is going to reduce that distance to .25" - .30". A 160 will probably rub the chain.

I'm planning on upgrading to a set of Michelin Pilot Road 3s in the future. I will stick with a 110/70 front because they offer that size, but I will have to go to a 150/70 rear as they don't make a 140/70.

I have to wonder if Honda decided to go with 140/70 in the rear based mainly on the extremely low pricing they set on the to compete with the Ninja 250?

Teakdust
 

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I agree Aufitt... Tire sizes are specific to a bike for a reason. Not to say they can't be changed, but doing so will (usually negatively) affect the handling. And, unless you really know what you are doing when you start making such modifications, you are drastically increasing your chances of landing on your backside.
Not to say that Honda is perfect, but they have been building bikes since 1948... pretty likely to know what they're doing by now.
Also, if there are a lot of ruts and other such road hazards, you are actually better off with the narrower tire as it will track better. The appropriate changes to make there would be to the suspension. Pretty limited to preload adjustments on the 250R, but a good suspension person can get you correct springs and Racetech can definitely help (especially with the springs and potentially with damping characteristics.
People told me that putting a rc51 front end on my VFR750 was stupid. They also told me that putting a rear wheel off a newer VFR800 that was 1/2" wider on the back with a 190/55 tire was stupid. I can honestly say that the combination of those two things have made that bike the most fun I have ever ridden. I take that thing way out of its comfort zone on the track and can honestly say that i can roll that 190/55 to the edge. I know there is no way i could ever go that big on the 250 and i dont want to. But measuring the width of the rim and the width of the inside of the tire i know i could get a 150 on the 250 with no problems. As a matter of fact the race-ready ninja 250's that they rent at the track run 150 width tires in the back and also a taller profile. They are less football shaped and more arced. Im not saying that the 140 is bad at all, but i believe a 150 can do nothing but help. Just because honda put that tire on there stock does not mean that it is the best tire for the bike and for its rider. They probably chose that tire because its cheap and fits in with the needs of most people and the most different type of riding conditions. For example i dont need a tire with so many rain grooves, as i will never ride my bike in the rain. Honda chose a well-rounded tire to meet the needs of many of its customers, many of which are new to the sport.
 

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Wheel size

As a matter of fact the race-ready ninja 250's that they rent at the track run 150 width tires in the back and also a taller profile. They are less football shaped and more arced. Im not saying that the 140 is bad at all, but i believe a 150 can do nothing but help.
Do you know what size tire and wheel the Ninja had? The stock wheels are even narrower than the Honda. What tread profile shape will we end up with if we go to 120/ 70/ 17 and 150/ 70/ 17 on our stock wheels for the CBR250R and how will it effect cornering as the tire will have a rounder profile than it was designed for. Most replacement tires aren't offered in our size. Maybe that will change by next spring due to the large number of these bikes Honda is selling world wide.
 

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Ive changed wheels b4 and its no easy task.

My ancient RZ500 needed it as it had a fat 16" front and a skinny 18" rear.
Mr Yamaha got is so wrong back in 1984 and managed to kill half the RZ pilots in the world.
Despite me wanting to keep originality it now has-
5.0x17 rim from a TRX850 with 160/60-17 tyre and underslung YZF750 caliper on the rear,
3.5x17 rim from an FZR1000 with 120/60-17 tyre and FZR dinnerplate brakes and 4 piston calipers.

Its turned a pig into a sweet sensation.
My point is that bike needed it.. a 2011 cbr250r does not.

A 140 rear on a 4.0 rim is already the upper limits.
If you put a 130 on it would not lose the edge.. it would actually flatten out the crossection and maybe even make it better.
A 150 will curve round the edges and without a 4.5 rim will make it worse.

(plus they dont 'look' wider for the squids out there.. measure a fitted one you'll see NO diff)

A Whosang 250 has a 150 but thats marketing and the fact it shares componetry with the 650 model.

Best thing I did to my Triumph 955 Daytona was put a 180 on the 6.0 rim.. made it work the tyre better, use all of it, and a better cross section..
Many trackdays on that bike.
Its just marketing for squids that determines wider tyres than GP and superbikes of the day used.

If you think Mr Honda got it wrong well yoyu're a better engineer than him.
Talk to a knowledgable tyre technician at the dealer or a race mech at the track.

You do not have to reinvent the wheel..why change it???
All I'd do is look into a 110/60 profile for the front instead of the 70.

Aside from all that ...the IRC's are getting a great write up for a budget oem tyre and I'm sure Bridgestone will have some sticky stuff (for the few that actually need it) within the year.
 

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Whats against replacing with an IRC till then?

Surely these tyres last 12,000km or one year?
 
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