Spoked Rims on a Ninja

[Retro Ninja]

Hello all, new here and I am in the process of building a 07 Ninja 250 into a cafe racer style bike.

I see on the web it is popular for the Kawaski KLR 650 guys to swap our ninja rims on for a supermoto look. And the swap is pretty much a direct swap over, only thing needed is correct tooth sprocket and axle spacers.

I am thinking it should swap the other way around as well. I want 17" front and back spoke rims with street tires to help the vintage look.

Has anyone done this sort of swap here?

Here is ninja 250 rims on a KLR 650

[Retro Ninja]

Just for reference, these are a few that inspired me to go this route with a Ninja 250. And the last one is the spoked look I'm going for.

[fry1024]

Those spoke rims really complete the cafe racer look. Definitely the way to go.

[quicklooker]

Those spoked rims are HOT.

[StephenA]

nice! keep us posted.

[Yasko]

Dang that looks hottttt spoked.

[psych0hans]

Looks good... I doubt you'll find anyone here who's done it. Why don't you lead by example? I'm sure someone will follow. Good luck!

[CZroe]

FWIW, you should look into what it takes to run the 17" J wheels on the F bike. Other than spacers and grinding on the caliper mount, the brake caliper torque arm needs to be broken and re-welded. Good luck!

[joshuajcrouch]

Hey Retro Ninja... keep us posted on your progress. Have you considered starting a build thread? Any pictures of your bike so far?

[StephenA]

Build thread build thread build thread build thread!...
Posted via Mobile Device

[Retro Ninja]

Originally Posted by StephenA

Build thread build thread build thread build thread!...
Posted via Mobile Device

Here is a small thread on what I previously did. The bike is now just stripped so not much to post on current, but I will when the time comes .

http://www.ninjette.org/forums/showthread.php?t=130030

[caps]

Originally Posted by StephenA

Build thread build thread build thread build thread!...
Posted via Mobile Device

Originally Posted by Retro Ninja

Here is a small thread on what I previously did. The bike is now just stripped so not much to post on current, but I will when the time comes .

http://www.ninjette.org/forums/showthread.php?t=130030

We need more pictures...

[StephenA]

Originally Posted by caps

We need more pictures...

[Retro Ninja]

Going to get a closer look at a klr 650 this weekend to verify and see if this is doable before I order parts. I am also thinking instead and doing a 17" rear and 21" front and lower the front so it sits level, with black spokes and polished rims.

[coughing skunk]

totally not trying to hate right now, but why cafe the ninja? One thing to think about if trying to run larger wheels on the ninja is rotational inertia and the energy required to turn the wheel.

I'll try not to get too science-y..

Angular Kinetic Energy (KE) = 1/2 * I * w^2
where I is the moment of inertia for an object and w is the angular velocity

I for a hollow cylinder, which we can approximate our wheels to be for simplicity, is 1/2 * m * r^2
where m is mass of the wheel and r is the radius of the wheel

This means that for the 16 inch wheels, r is .2032 (meters, SI units), and KE equals 1/2 * 1/2 * m * .2032^2 * w^2
= 1/4 * m * w^2 * .041

For the 21 inch wheel, r is .2667, and the resulting KE is
= 1/4 * m * w^2 * .071

Assuming everything else equal (which really isn't, the 21 inch wheel will likely be heavier), if we divide the KE required for the 21 inch wheel by the KE required for the 16 inch wheel we get .071/.041 = 1.7. That means to turn both wheels at the same speed, the energy required to turn the 21 inch wheel is ~1.7 times the amount needed for the 16 inch wheel!

Moreover, how will this affect the overall acceleration of you and your bike?

Well, if you can believe some hand waving in lieu of trying to type of the derivation of how angular velocity relates to a constant linear acceleration then we get:
w^2 = 2*a*theta/r
where a is linear acceleration, theta is how far the wheel has rotated and r is the radius of the wheel

Plugging this into our equation for KE, we get KE = 1/4*m*r*a*theta
We want to know how fast you'd accelerate with the larger wheels, so we'll solve that KE equation for a:
a = 2*KE/(m*r*theta)

Since the energy output of your motor won't change by swapping wheels, KE will be the constant, along with m and theta at any given time during acceleration. Note, this means at any 'snapshot' in time, not that your engine doesn't change its energy output based on revs.

So, to find the relative acceleration difference, we divide the acceleration from the 21 inch wheel, a21, but the acceleration of the 16 inch wheel, a16.
a21/a16 = (1/r21)/(1/r16)=r16/r21 = .76

With the larger wheels, in an ideal world (real world would be worse), you are effectively accelerating %24 slower than with the 16 inch wheels! The same effect happens when kids put 18's on their civics with the 90hp 1.5L motors..

Anyways, enough of that. Not trying to kill a dream just spread some knowledge.

One of my other bikes is an early model XS650 with 19" in front and 18" in rear spoked wheels and more than twice the cc's of the ninja. Not that a small, light, high-revving spoked wheel bike wouldnt be cool.. Just sayin, I got my XS for $1000 running with good chrome. I know there are older larger displacement KZ's for just as cheap or cheaper.

[tooblekain]

[caps]

^lol, it's not that complicated bud.




And OP acceleration difference be damned, I wanna see a cafe ninja

[tooblekain]

When read slowly yes, but at first glance, brain melted

[Motofool]

Originally Posted by Retro Ninja

........I am thinking it should swap the other way around as well. I want 17" front and back spoke rims with street tires to help the vintage look.

Just in case you have to repair or rebuild some rims:

http://www.webbikeworld.com/motorcyc.../spoke-wheels/

[Motofool]

Originally Posted by coughing skunk

..........With the larger wheels, in an ideal world (real world would be worse), you are effectively accelerating %24 slower than with the 16 inch wheels!......

As far as I know, spoke wheels have been much lighter and stronger than cast wheels.

Cast wheels are simply cheaper to produce in mass and go well with the tubeless tires.

So, why the new-gens and the 300s' abandoned the 16" wheels?

Why not going to 15"~14" rims instead?

It seems that engineers considered something else than angular inertia for specifying those changes.

[choneofakind]

Originally Posted by Motofool

It seems that engineers considered something else than angular inertia for specifying those changes.

Yeah, tire choice. Many many more tire options are available in 17" sizes. It seems to be the standard among sport bikes.

I wouldn't be worried about the inertia of larger wheels on the ninjette. It's a slow bike anyways. I personally would rather go with a matched set of 17's than go for funky street fighter sizes, but that's just my preference.

[Motofool]

Originally Posted by choneofakind

...........It's a slow bike anyways......

[choneofakind]

[JohnnyBravo]

Originally Posted by choneofakind

I personally would rather go with a matched set of 17's than go for funky street fighter sizes, but that's just my preference.

What he said

[alex.s]

Originally Posted by coughing skunk

totally not trying to hate right now, but why cafe the ninja? One thing to think about if trying to run larger wheels on the ninja is rotational inertia and the energy required to turn the wheel.

I'll try not to get too science-y..

Angular Kinetic Energy (KE) = 1/2 * I * w^2
where I is the moment of inertia for an object and w is the angular velocity

I for a hollow cylinder, which we can approximate our wheels to be for simplicity, is 1/2 * m * r^2
where m is mass of the wheel and r is the radius of the wheel

This means that for the 16 inch wheels, r is .2032 (meters, SI units), and KE equals 1/2 * 1/2 * m * .2032^2 * w^2
= 1/4 * m * w^2 * .041

For the 21 inch wheel, r is .2667, and the resulting KE is
= 1/4 * m * w^2 * .071

Assuming everything else equal (which really isn't, the 21 inch wheel will likely be heavier), if we divide the KE required for the 21 inch wheel by the KE required for the 16 inch wheel we get .071/.041 = 1.7. That means to turn both wheels at the same speed, the energy required to turn the 21 inch wheel is ~1.7 times the amount needed for the 16 inch wheel!

Moreover, how will this affect the overall acceleration of you and your bike?

Well, if you can believe some hand waving in lieu of trying to type of the derivation of how angular velocity relates to a constant linear acceleration then we get:
w^2 = 2*a*theta/r
where a is linear acceleration, theta is how far the wheel has rotated and r is the radius of the wheel

Plugging this into our equation for KE, we get KE = 1/4*m*r*a*theta
We want to know how fast you'd accelerate with the larger wheels, so we'll solve that KE equation for a:
a = 2*KE/(m*r*theta)

Since the energy output of your motor won't change by swapping wheels, KE will be the constant, along with m and theta at any given time during acceleration. Note, this means at any 'snapshot' in time, not that your engine doesn't change its energy output based on revs.

So, to find the relative acceleration difference, we divide the acceleration from the 21 inch wheel, a21, but the acceleration of the 16 inch wheel, a16.
a21/a16 = (1/r21)/(1/r16)=r16/r21 = .76

With the larger wheels, in an ideal world (real world would be worse), you are effectively accelerating %24 slower than with the 16 inch wheels! The same effect happens when kids put 18's on their civics with the 90hp 1.5L motors..

Anyways, enough of that. Not trying to kill a dream just spread some knowledge.

One of my other bikes is an early model XS650 with 19" in front and 18" in rear spoked wheels and more than twice the cc's of the ninja. Not that a small, light, high-revving spoked wheel bike wouldnt be cool.. Just sayin, I got my XS for $1000 running with good chrome. I know there are older larger displacement KZ's for just as cheap or cheaper.

i believe you forgot to consider... everything else on the bike that isn't the wheels. so when you say 24% slower... its actually 24% of the energy needed to spin up the wheel, not move the bike. the energy required to spin up the wheel compared to the energy required to actually move the bike is magnitudes different. so in actuality, the difference in perceived power would likely be less than 1%.

[alex.s]

its about 0.2% (one fifth of one percent, or about 0.6hp) difference in end accelleration between the two wheels when you consider the rest of the bike. this is using the assumed weights/measurements from the quote above. which themselves are pretty questionable (like motofool said, the spoked wheels should be lighter)

[lowdown112]

Idk all that science-y stuff yall are talking about. But will the rims swap out or no? Cuz i like spoked wheels. Even my bike isnt a cafe racer

[CynicalC]

ITT First year engineers jerking each other off.

[Snake]

I love the idea of spoked rims on the Ninja. I can't wait to see the final product.

[gustav129]

The energy loss by putting bigger yires can be overcome by gearing.

It's the same with trucks. If you are stock with 235/75r15's and go to 33's, it throws everything off the torque curve. But regearing axles to 3.73 or 4.10's, it balances out and there is no power loss.

I too am interested in spoke wheels.

[CZroe]

Regarding the KLR650 bikes with EX250F and EX250J rims: Can I get some links? I'm wondering what sort of modifications were required. Because they aren't a direct swap between the F and the J Ninjas, at least one of those must require modifications and I can already tell that the front rims are both mounted backwards for the brake rotor to be on the correct side.

[Chicagobob]

It worked for this guy (different fork, though):

[Singh2jz]

Originally Posted by Chicagobob

It worked for this guy (different fork, though):

Now that's a bike done right! Ninja no more..

[ironcitybikes]

did you ever get your spoked wheel conversion done?

[CZroe]

When my brother brought his KLR650 down I noticed just how similar the swing arms were between the 250J and the pre-2008 KLR650. He even wanted some spare parts from mine!

[jbrown243]

Im looking to do the BCB Cafe kit mo my bike. Id like to know more about the Spoked wheels, if you ever did it?

[csmith12]

Welcome Jason!

I would like to see also.

[verboten1]

It's ridiculously easy to put whatever wheels you want on these bikes, they are chain drive.


In the last couple of weeks. I've fit a yamaha rear wheel on the forks from a Suzuki, and figured out how to put the rear wheel from a ninja 650 onto my 250. You just have to either find wheels that use the same size axle, or find bearings that fit your existing axle. Then you make spacers to line up the chain and/or brake rotors.

[sharky nrk]

Originally Posted by Chicagobob

It worked for this guy (different fork, though):

That right there is the ****

[Ghostt]

Wow good thread, like the response to the engineering.

As far as the above bike, those rims are the ticket, but it looks like an entire different front end set-up for sure

I'm sure somewhere out there something will bolt up with minimum effort, knowing how Kawasaki loves to use the same part for multiple bikes.

Research is the key to this one .