kz1000p rear tire size query

So I swapped the forks on my kz1000 csr for kz1000p forks and now realize that I need the front police wheel to fit the rotors on. While I'm at it i might as well put a police rear wheel on too, right? Wouldn't the stock 3.00x16 rear wheel combined with the police 2.15x18 wheel could cause poor handling? Im kinda scared of poor handling now.... IYKYK

Now my question; for the rear police wheel (2.50x18) would it be too much to fit a 130 tire on? I hear that its possible that the tire could deform to fit the smaller wheel. Im asking because it is difficult to find matching tire sets for the stock police wheels.

If having the 16" wheel on wouldnt cause poor handling, I won't worry about it, but I am currently worried about it.

My opinion is that the stock rear wheel would be fine (and definitely better than squeezing a fat tyre on a narrow rim which would cause sidewall flex and probably make the bike weave) with the 18 front as long as you swopped the trees with the forks

I did swap the trees also. The lower triple was cooked so I almost had no choice.  Now I just have to figure out headlight accommodations. Well sounds to me like I'll be keeping the 16" rear wheel for now unless someone else has something to add. 

handling. what's the police front end geometry compared to the csr? are the police forks taller? then the police rear wheel might be the better option, since the police wheel is ~35mm taller. new quality fork springs would be good. and new quality rear shocks which might could address the wheel size difference. also worth mentioning. racetech fork emulators. but those require a bit of work to make the conversion. ps: for a 16" rear cast alloy wheel, the 1000k Ltd is probably a direct swap.

You also need to take into consideration the angle of the steering head (frame tube that the steering stem goes through), plus any angle designed into the clamps, plus any offset in the clamps, plus the side height of the tires. Yes, the tires. Just because you make a  two-inch change in the diameter of a wheel, does not automatically make a two-inch change in the diameter of the tire. Some have taller sidewalls than others. As H1Vindicator noted, changing the radius of the rear tire/wheel combo will alter the angles up front by raising or lowering the rear of the frame.

It is complicated. The simplest solution in this case would be to use CSR/LTD parts.

Welp, I just did some math using a conversion chart at weeksmotorcycle.com--

CSR/LTD
Front: 3.25 - 19 = radius 323.85 mm (very few made in this size today)
          110/90-19 = radius 340.3 mm
          100/90-19 = radius 331.3 mm

Rear: 130/90-16 = radius 320.2 mm

Copcycle
Front: MN90-18 (~110/90-18) = radius 327.6 mm (surprisingly close to the stock CSR/LTD measurement)

Rear: MR90-18 (~120/90-18) = 336.6 mm

If you put a 130/90 on the rear copcycle wheel, you would get a radius of 345.6, thus raising the back of the bike 25.4 mm over stock.

Keep in mind that tire sizes are not exact. A 110/90-19 from one manufacturer may be several mm wider or narrower than the same size from another manufacturer. Even more insidious are the letter designations. An MN90 tells us basically nothing about the actual size of the tire. M = motorcycle, and the second letter indicates the approved rim width. In this example, N is for use on rims between 2.15 and 2.75 inches in width. The 90 is the aspect ratio, but only the manufacturer knows the actual width, so this number is pretty useless for the consumer.

P.S.2

I calculated the radii based on the stated tire and rim sizes. HOWEVER, reality is often different.

I calculated a 110/90-19 tire to have a diameter of 680.6 mm. Metzeler says that their Cruistech tire in that size has an inflated diameter of 27.36 inches, or 694.44 mm!

I calculated a 130/90-16 tire to have a 640.4 mm diameter. Metzeler sez, 25.82 inches, or 685.828 mm.

ymmv

There is no substitute for measuring the exact tires, forks, clamps, et cetera that you will actually use.

Looks like I was on the money with the stock rear and 18 cop front. If you post the off-set and fork length I will put them into a calculator. The stock CSR/ltd forks are 840mm from top to axle centre, J are 810mm.

TexasKZ you're killing me.. I appreciate the help but a lot of that went over my head. Correct me if im wrong, but are you basically saying that there are a lot of variables at play but in general a cop front tire is really close, like a 1.2% difference so it shouldn't upset frame geometry but tire manufacturer specs upset the difference? 

H1V I have plans for the front and rear as of now

Wookie I measured the csr forks, which were lying on the ground, from a direct line of center axle to the middle of the top of the fork, not including the cap. They ran at about 850mm which isnt what you have. Maybe i measured wrong? The offset of the axle was about 30mm unless that's not what you're looking for. The police forks were the same length as the J forks at 810mm. 

bound wrote:

TexasKZ you're killing me.. I appreciate the help but a lot of that went over my head. Correct me if im wrong, but are you basically saying that there are a lot of variables at play but in general a cop front tire is really close, like a 1.2% difference so it shouldn't upset frame geometry but tire manufacturer specs upset the difference? 

H1V I have plans for the front and rear as of now

Wookie I measured the csr forks, which were lying on the ground, from a direct line of center axle to the middle of the top of the fork, not including the cap. They ran at about 850mm which isnt what you have. Maybe i measured wrong? The offset of the axle was about 30mm unless that's not what you're looking for. The police forks were the same length as the J forks at 810mm. 

It's the off set in the tree's that I meant - That is the distance from the centre of the stem to the centreline of the forks

NOT being critical of your transformation bound but wouldn't it just of been easier/cheaper to of just replaced the lower tree that had gotten bent? You've opened a whole other can of worms at this point. 

You're right. It would have been a lot easier and cheaper. I guess i just dont view it in that way. I made the decision long ago that this was MY bike and ill just mess around with it. For me it was a game of compromises and I really didnt want the leading axle forks and the same old forks that could have almost killed me, regardless of whether it was my fault or not. Id rather install the ~10 years newer forks with the center axle that I wanted. The "can of worms" that I opened up is the fact that doing this conversion could have potentially made my problems worse or better, I dont know yet  . In a way this is my version of fun!