kz1000p rear tire size query

Wookie58 wrote:

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

The offset is about 50mm for the cop bike and 30mm for the csr!

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? 


 

I apologize. I sometimes forget that most folks do not enjoy trips down a rabbit hole nearly as much as I do.
I reckon there were three main points in all that.

1. There are quite a few variables involved in such modifications, and there are a few that have not yet been mentioned.
2. Tire diameter is more important than wheel diameter.
3. It is important to measure the actual parts you use, especially when it comes to things like tires. Their actual width and diameter can vary significantly from the measurements stamped on the sidewall.

A 1.2% difference in diameter may not be significant by itself, but when you toss in 30 or 40 mm shorter forks, and a slight difference in offset, plus a small difference in the angle of the forks relative to the steering stem, plus a little less drop in the top clamp, plus a small change in rear height, you can end up with a total that is problematic.

And then there are things like brake alignment, speedometer drive, chain alignment and such.

Some of the members here have been down this road multiple times and can give you good advice. Be patient, ask a lot of questions. Digest the advice. At the end of the day, you can put together an interesting and fun ride that will not pitch you off into the ditch.

TexasKZ please never change! I love the rabbit holes, this one was just a lot more involved

bound wrote:

Wookie58 wrote:

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

The offset is about 50mm for the cop bike and 30mm for the csr!

You can see now why I said change the trees, the difference in off set balances out the leading axle. All we need now is the fork angle in the straight ahead position when it is sitting on both wheels (angle gauges aren’t expensive on Amazon)

It's all starting to make sense now! I need to get the police axle bolt before I do any moving of the bike because the police forks are spaced apart a lot more than the csr forks and they clamp on differently. I'll make sure to get that info for you in a couple days!

I think this guy does a pretty good job of explaining the basics.

Alright Mr. Wookie, I finally have the fork angle! I measured 28.25 degrees from straight down to the front. This was measured with the 19 inch wheel.

Also, out of curiosity, what are you measuring for the forks and how? It would be fun to mess with values to see how that affects other numbers.

OK so the below gives the figures for stock, and then the Cop front end with both 18" and 19" front wheels (link below to the calculator) the 18" wheel will give a trail figure pretty close to stock where the 19" inch extends the trail so will make it steer slower but increase high speed stability
RB Racing Rake and Trail Calculator