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You all say a 170/80/15 rear tire fits. It does. BUT. Got my new oversize tires delivered yesterday and I had them mounted on the rims. To install the rear tire I had to deflate the tire, get the help of a 230 pound friend, use 2 crowbars, several blocks of wood and a 6 foot pry bar. It took over 1 hour to get the tire on the hub. I hope it's worth it. :doh:
 

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Yeah. That's why I just pop the wheel off the bike, toss it in the back of the car, drive to the service dept of my local dealer and let them deal with it.

I get to sip a cold beverage and look at all the new models on the showroom floor while they:

Pull off the old tire.
Clean the rim (that Ride On stuff comes off with water)
Mount the new tire. ( they have all the right tools )
Balance the tire (they have a machine that does this now) And
....Dispose of the old tire.

Much safer, much cleaner, and if they fkup the rim, they buy me a new one. (where as if you damage your rim, the bills in your pocket)

Easy. All for about 25 bucks.... ;)
 

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Hmmmm.... My Commander II took about 5 minutes with my wife helping me. What brand did you get?
 

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Discussion Starter #5
I got Kenda Kruz 673. A lot of guys here like the tire. I just took the bike out for a ride and it handles very well.
 

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A 170/80 tire is too big for the Vulcan. The stock 150/90 is too big for the Vulcan, but thats what it was designed for. Looks like a Hoosier drag slick to me. Yet the Vulcan looks nothing like a dragster. A 170/80 will go on the rim fairly easily, but getting the rim/tire back on the bike is another matter. The stock tire barely fits. I would suggest removing the final drive gearcase to give you more room.

I personally hate huge rear tires on bikes. A 130/90-16 wasn't too bad, and is what most early cruisers (and my '97 Road King ) use, but these huge 300 tires just look ridiculous. To me it's kind of like using 24" wheels with a thin coating of rubber on vehicles that came with 15"-16" wheels with real tires. Hopefully both are fads that will eventually go away.


As far as using a shop, no shop is touching my wheels. I had an expensive aftermarket car wheel chewed up by a tire shop once, the idiot that did it pointed out that it still held air. I almost had to sue them to get them to pay for the wheel. I just took it in for a flat repair.
 

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I'm sure I'm going to hell now, but my only response to that is:




A 170/80 tire is too big for the Vulcan. The stock 150/90 is too big for the Vulcan, but thats what it was designed for. Looks like a Hoosier drag slick to me. Yet the Vulcan looks nothing like a dragster. A 170/80 will go on the rim fairly easily, but getting the rim/tire back on the bike is another matter. The stock tire barely fits. I would suggest removing the final drive gearcase to give you more room.

I personally hate huge rear tires on bikes. A 130/90-16 wasn't too bad, and is what most early cruisers (and my '97 Road King ) use, but these huge 300 tires just look ridiculous. To me it's kind of like using 24" wheels with a thin coating of rubber on vehicles that came with 15"-16" wheels with real tires. Hopefully both are fads that will eventually go away.


As far as using a shop, no shop is touching my wheels. I had an expensive aftermarket car wheel chewed up by a tire shop once, the idiot that did it pointed out that it still held air. I almost had to sue them to get them to pay for the wheel. I just took it in for a flat repair.
 

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Discussion Starter #8

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@JM2001, did you notice an RPM drop with the 170/80-15?
 

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Discussion Starter #12
@JM2001, did you notice an RPM drop with the 170/80-15?
First, I went up to a 110/90/19 front tire. With the 2 new tires I went up in rpms . At 60 I used to be at 4000 rpms. Now I am at 4200. It may be because the speedo is more accurate now. The next set of tires I will go back to the 100/90/19 front. I think the bike looks better with the smaller tire.
 

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Discussion Starter #14
^ And looks are very important.;)

Most folks going to the 170 rear report at most a 200 rpm reduction from stock.


I read where they said they got lower rpms. The only way I see that happening is that their taller 150/90/15 tires had very little tread and the shorter 170/80/15 with new tread was taller to get a drop in rpms. A smaller diameter tire has to rotate more to cover the same distance that a larger diameter tire does.
 

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I read where they said they got lower rpms. The only way I see that happening is that their taller 150/90/15 tires had very little tread and the shorter 170/80/15 with new tread was taller to get a drop in rpms. A smaller diameter tire has to rotate more to cover the same distance that a larger diameter tire does.
Uh, which tire do you think is taller again???

My math shows 170/80 is bigger than 150/90. Thus, the 170/80 tire is taller than a 150/90 tire and would cover more ground per revolution. I miss something here?

170 divided by 80 is bigger than 150 divided by 90 right????

See Here:
http://www.vn750.com/forum/showthread.php?t=19864&highlight=Taller+tire
 

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A 170/80-15 tire is wider, and slightly smaller in tread diameter compared to a 150/90-15. By changing from a 90 to an 80, you are changing the aspect ratio between width and diameter. So it does appear like it is being done for looks. I would prefer a slightly narrower but larger diameter tire.
 

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A 170/80-15 tire is wider, and slightly smaller in tread diameter compared to a 150/90-15. By changing from a 90 to an 80, you are changing the aspect ratio between width and diameter. So it does appear like it is being done for looks. I would prefer a slightly narrower but larger diameter tire.

No it isn't. Look at the photos. Do the math. Tire bight is the result of the ratio. 170/80 = 2.125 cm. 150/90 = 1.666....

So the 170 tire is is taller or has a bigger diameter. Right????
 

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Discussion Starter #18

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No it isn't. Look at the photos. Do the math. Tire bight is the result of the ratio. 170/80 = 2.125 inches. 150/90 = 1.666....

So the 170 tire is is taller or has a bigger diameter. Right????
yes your math is correct to finish it out you have to multiply the sidewall height x2 and then add rim diameter, 2.225x2+15 for the 170 and 1.666 x2 +15 for the 150.Doing the math will not give the same results kenda gives for either tire.

I have never found tire sizing to be consistent between manufactures or been able to figure out exactly how big a tire will be b doing the math.But this one has me puzzled,kenda's chart seems to say one thing which the tach on this bike confirms.

My experience was the opposite,the Metzeler was talller than the 404 Dunlop oversize vs stock size.Obviously whatever the manufacturer of the tire calls it size wise,their own chart would be your best bet for figuring out the diameter of any given tire,Sort of mislabeling on the tire manufacturers part,seems to me.some may count from the bead out to where the tread begins sidewall and some may count only from the outer rim to the ground .I see no standards that the industry holds to on bike tires,IMHO.
 

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Well I kept asking "right??" because I myself was unsure. I was told the second number is the sidewall height expressed as the ratio of the tires width. The width being the first number.

Even redoing the math... Likely the right way....lol would say:

90 percent of 150 is 135
80 percent of 170 is 136

Still making the 170/80 taller.....

See here:https://www.denniskirk.com/help_center/tire-sizes.jsp

Yes a 150/80 would be shorter than a 150/90... But you have to start with the tires width first.


I do remember reading those switching to Metz 170/80's reporting a slight drop in rpm at a given speed.

And i do understand comparing a worn out tire size to a brand new one, regardless of sizing, would not be accurate....
 
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