Kosman Rear Wheel

[relliott]

Hello everyone,

I was looking at switching out my stock 15" rear for a Kosman 17". Any thoughts?

Thanks,

Rob

 

[Barry barker]

I assume you want to switch to radial tires? If you are having a new wheel made go for the 18", with a 180r/ 55 x18 tire you will have almost the same outer dia as the stock tire. Keeps your stock gear ratio and bike geometry. Going to a 17" rear with an 18" front changes the geo in a bad way.

 

[gamorg02]

barry. are you speaking from experience? I run a 17/18 combo and haven't had any ill efffects.

also a 190/60 rear in the 17" flavour brings it right about stock. 190/55 is pretty close too.

 

[m-cman]

I have a Kosman 18" with a 170/60-18 radial. Had to do the washer swap for it to fit. Don't know how anyone could get the 180/55 to fit. The swingarm narrows the closer you get to the pivot. A 180 on a 17" rim will usually fit as it does not go as far into the swingarm.

 

[Barry barker]

No Garrett I have no experience with Kosman wheels or riding a bike with 17" rear wheels. When I was modifing my bike the tire manufactures wanted me to keep the rear tire dia larger than the front on a street bike. Honestly, I can not remember the reason, must be that CRS disease. i do remember checking tire sizes on a few stock street bikes and found the rear tires in most cases are larger in diameter. If you have this set up and it works, I stand corrected.
i have a 180r/ 55 x18 on my Carrozzeria and it fits with about 1/8 to 3/16 clearance on the left side. I also checked my swing arm notch and it appears to be parrallel with the wheel and plenty long enough for a smaller or even larger dia tire. I suppose from this, we can conclude the Kosman offset is different from the Carr wheels. thanks for keeping me honest.

 

[gamorg02]

barry,

i apologize if my comments came off a 'little' harsh as it was late and i was tired haha. i was merely interested in what you had learned in your travels.

it very well could be true and i'm curious as i will be changing tires (both) soon and could probably change the profiles a bit if there was reason to.

 

[sdt354]

barry. are you speaking from experience? I run a 17/18 combo and haven't had any ill efffects.

also a 190/60 rear in the 17" flavour brings it right about stock. 190/55 is pretty close too.

Thanks for clarifying that Garrett. I calculate the 17" with a 190/50 to be very close to my 15" 170/80.
Steve-o

 

[gamorg02]

just for some quick numbers:

Tire size*****Overall Diameter (inches)
STOCK RIM
150/90-15****25.63
170/80-15****25.71

17" RIM:
190/50-17****24.48
180/55-17****24.8
190/55-17****25.23
180/60-17****25.5
190/60-17****25.98

18" RIM
180/60-18****25.09
190/50-18****25.48
180/55-18****25.8
190/55-18****26.23
180/60-18****26.5

 

[m-cman]

"I have a 180r/ 55 x18 on my Carrozzeria and it fits with about 1/8 to 3/16 clearance on the left side. I also checked my swing arm notch and it appears to be parrallel with the wheel and plenty long enough for a smaller or even larger dia tire. I suppose from this, we can conclude the Kosman offset is different from the Carr wheels."

Does this mean you have a notched swingarm? I have the stock swingarm which is why my 170/60-18 (26.03" diameter) required the washer swap. With the washer swap, I have about 1/8" clearance.

 

[Barry barker]

I have a stock swing arm. I have heard rumors that the stock wheel is offset 3/8 from center. Not sure if this is true, not sure which direction, but I thinK the offset is toward the notched side of the swing arm. If Carrozzeria corrected this offset and kosman did not that might explain the differance. Can anyone confirm the offset?

 

[gamorg02]

since cazz has their own rims its probably much easier to correct this, since kosman can't weld the hub offset from the new donor outter rim eh?

 

[[email protected]]

I have a stock swing arm. I have heard rumors that the stock wheel is offset 3/8 from center. Not sure if this is true, not sure which direction, but I thinK the offset is toward the notched side of the swing arm. If Carrozzeria corrected this offset and kosman did not that might explain the differance. Can anyone confirm the offset?

The stock wheel is offset to the right as viewed from behind the bike.
Seems like many aftermarket wheels are offset to the right even more than the OEM wheels.

 

[satariel666]

I have a stock swing arm. I have heard rumors that the stock wheel is offset 3/8 from center. Not sure if this is true, not sure which direction, but I thinK the offset is toward the notched side of the swing arm. If Carrozzeria corrected this offset and kosman did not that might explain the differance. Can anyone confirm the offset?

Correct. Stockers has some offset but this was made on purpose by yamaha.

My 17 inchers can run with 190 tyre and no offset at the same time - of course with nothced swingarm.

 

[gamorg02]

Correct. Stockers has some offset but this was made on purpose by yamaha.

My 17 inchers can run with 190 tyre and no offset at the same time - of course with nothced swingarm.

prez -> when you say offset what do you mean in reference to? the center of the swingarm? is the center of the swingarm centered perfectly in the frame?

if it isn't, that could be easily adjusted by getting 2 adjustable bolts and nuts to hold the swingarm on, yea?

 

[Barry barker]

I found some concurring info on the tire dia, firefly seems to have a much better handle on explaining the facts than I do, his article is in Technical 85 -07/ suspension/ logical order of mods. i have added a quote below. This is the same information the Avon rep gave me some 5 years ago when I was planning my suspension. This is a good article with lots of info. i have not lowered the forks, I have scraped hwy and foot pegs and really would perfer not to, some thing you just can not get used to.


4-If you need a radials pacifier then Go for it but its more $$$$ to spend, it?s a little complicated than slapping a rear fatter wheel and getting a radial front tire in the common sizes of 120/60x18 & a 180/55x17, this combination really messes up any gains from radials as it messes up with the bike geometry ( rack & trail) with a front 18 and a rear 17 the center of gravity is shifted backward due to not enough front lowering loosing the good effect of lowering the forks that was done earlier, now is the time to ask yourself whether to go with 17 front and rear or go with 18 front and match it with an 18 rear also how wide a wheel do you need? The wider the wheel/tire combo the less agile the bike gets in twisties but feels stable in straight riding the same effect also happens when the bike sits too low front and rear ( good for straights bad for canyons ). Radials come in shorter profiles 55/60 for the rear 60/70 front, there is a big size variation between tires of the same size with different manufacturers so paying attention to the tire size is like the icing on the cake ( fine tuning ) Metzler site provides a PDF listing of exact tire sizes in details like 1- permitted rim width, 2- max tire width, 3- max tire height, 4- max weight, 5- weight of the tire 6- tread depth ( important if looking for longer life tires) here is an example: you put a 180/55x17 rear and that lowers the bike by 3 cm ~ a little more than one inch while putting a radial 18 front say a size 120/70X18 or a 130/70X18 the bike is not lowered enough in the front and you will get a feeling as if you have a passenger ( light uncontrollable steering).) The front wheel 17 inch makes the radials worthwhile, leaving the front 18 is OK but a rear 18 is a must and you will have to deal with a VERY limited choice of tires, not only that but the 17 inch front makes the bike feel lighter and nimble in all situations by reducing the rake and trail. I think the 18 inch front defeats the purpose of the whole handling thing by lowering the rear and not much lowering in front, transferring the weight of the bike further backward instead of moving it forward.

 

[Barry barker]

The stock wheel is offset to the right as viewed from behind the bike.
Seems like many aftermarket wheels are offset to the right even more than the OEM wheels.[/QUOTE]

So the offset is away from the notch, I do not like hearing this, that means my offset is even more than stock. My bike rides and handles with the best of them, I wonder what fixing this offset would do? I have heard Sean talk about moving the swingarm a max 3/8 " anymore and it fouls with the drive shaft.

 

[satariel666]

prez -> when you say offset what do you mean in reference to? the center of the swingarm? is the center of the swingarm centered perfectly in the frame?

if it isn't, that could be easily adjusted by getting 2 adjustable bolts and nuts to hold the swingarm on, yea?

Swingarm on pivots as well rim at the hub has some offset.
As noted swigarm has some room to play with but rim dont.

Maximum tyre width that can be archived on notched and "pivoted" swingarm, still having rim close to the center is 190 fited onto 5,5" rim.

 

[satariel666]

So the offset is away from the notch, I do not like hearing this, that means my offset is even more than stock. My bike rides and handles with the best of them, I wonder what fixing this offset would do? I have heard Sean talk about moving the swingarm a max 3/8 " anymore and it fouls with the drive shaft.

Not necessarily a bad idea, it depends...

 

[gamorg02]

Heres something for thought:

stock: 150/90/15 - 25.63 inch diameter
110/90-18 - 25.8 inch diameter

difference = .17 inches

that equals a 0.6% difference

my setup:
190/50 -17 = 24.48
120/70 - 18 = 24.61

difference .13 inches = 0.5% difference. so my setup is closer to equal than stock, i can't imagine a 0.1% can be 'noticable' hell the tires probably 'grows' that much when riding if not more and could change cold or hot pressure. and if the tires are proportionally the same the rake and trail won't change, right?

 

[[email protected]]

Heres something for thought:

stock: 150/90/15 - 25.63 inch diameter
110/90-18 - 25.8 inch diameter

difference = .17 inches

that equals a 0.6% difference

my setup:
190/50 -17 = 24.48
120/70 - 18 = 24.61

difference .13 inches = 0.5% difference. so my setup is closer to equal than stock, i can't imagine a 0.1% can be 'noticable' hell the tires probably 'grows' that much when riding if not more and could change cold or hot pressure. and if the tires are proportionally the same the rake and trail won't change, right?

You forgot to calculate the 1.5" drop in the shocks and the 1" drop in the forks. :biglaugh: