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Discussion Starter #1
Hey guys, local Harley Shop 50 miles away only has a Dunlop 90/90/19 handy that I could put on my bike...well, they do have a 100/90/19 Maxxis but I don't like it.

Okay, so stopping power and rubber on the road for cornering would be reduced somewhat. Any real problem I should consider if I go with the 90/90/19?

I'm thinking I'd like to find a car tire for the rear when the time comes and when the power is churning the narrower front might be more agreeing...and find an easy groove to slice.

Boy, gotta be a rear car tire out there somewhere. What about the old "English Fords," anyone know of any car that used a 3 1/2 or 4 in. rim? Anyhow, east coast, west coast, overseas, Timbuktu, and then I still have the Southern hemisphere, after that...I can go see the Gods about it. :)

Oh yeah, back, if I go with a 90/90/19 front tire is it a sure fire death wish or not much of a problem?
 

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With a 100/90-19 our speedometer are about 5-10% off on the low side. A 110/80-19 makes them pretty accurate. With a 90/90-19 your speedometer is going to be even more off

As far as handling, that can vary by tire so it's hard to tell 100/90-19 by different manufacturers will corner and grip differentlt based on composition.

As far as the rear tire and using a car tire.. IF you do go with one look for something along the lines of a volkswagon tire. Bear in mind that car tires handle different then motorcycle tires especially in the area concerning the sidewall. They usually do not flex as much on cornering but do have more surface contact on the straights
 

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Discussion Starter #3 (Edited)
Cool! Unless I can uncover any overwhelming concern I think I will go with the smaller front tire. Always been more of a chopper type guy anyway. Hopefully, a 90/90/19 will also be on the low, low side since tickets are rather expensive.

On using a car tire for the rear...google found a 165R15 will fit a 4" to 5.5" Rim...I'll start checking around at some old salvage yards, some of those guys probably have seen a lot of car rims in their lifetime.
 

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Mounting a car tire on the rear and mounting a car rim on the rear are two completely different animals, unless you know some trick to hooking up the rear brake and the final drive to just any rim..
Plus you can't go too wide or you run the risk of the tire rubbing against your swingarm.
I would think you would be looking for a tire that would fit on your existing rear end and rim
 

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so, on our bikes with the 100/90, the speedometer will read 50 but we are really going about 45-47 mph? or do I have that backwards? it will read 50 and we wille be traveling at 52-55 mph? and it will be more accurate with the 110/90? hmm.. I may have to borrow my buddy's gps for a short ride...
 

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with the 100/90 if the speedo is saying 50 you are probably closer to 45-47. with a 110, if the speedo says 50, you are probably doing 50 or darn close to it
 

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Discussion Starter #7
I would think you would be looking for a tire that would fit on your existing rear end and rim
Yes, that's what I meant. I'm thinking there are a lot of different cars in the world, and if an old, old salvage yard guy ever remembered seeing any extra narrow (3 1/2 - 4" wide) Rims on any car I could start looking at tires that would fit such a vehicle, if there is one. When I go back to the bike shop I'll take some measurements of the rear tire and see how close it can be gotten to in car size.
 

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Discussion Starter #8 (Edited)
Maybe if I keep searching "Darkside Tires" I might run across a VN750 owner that has already converted the rear tire...or at least tried to do so. 165R15 will fit a 4" Rim...but a 3 1/2" Rim...Problem?

Tire Size Comparison

Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
165/80-15 5.2in 12.7in 25.4in 79.8in 794 0.0%
150/80-15 4.7in 12.2in 24.4in 76.8in 825 -3.7%

And since I've read a 170/80-15 will fit the VN700:

Tire Size Comparison

Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
165/80-15 5.2in 12.7in 25.4in 79.8in 794 0.0%
170/80-15 5.4in 12.9in 25.7in 80.8in 784 1.2%

http://www.miata.net/garage/tirecalc.html
 

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<snipped>
And since I've read a 170/80-15 will fit the VN700:

<end snip>
I've been running a 170/80-15 on my 750 for something over 10K miles now; just replaced the first one, a Dunlop 404, with a Metzler ME880. I like the Metzler much better than the Dunlop; doesn't try to hang up in the parallel-to-the-road expansion joints like the Dunlop did.

A 170 is about the max that will fit a 3½" rim safely; Honda switched to a 170 from the original 160 on the Shadow Spirit, I think it was, a few years back. Several BUBF riders went to a 170 a few years ago; that's how I knew it would fit, the only holdback being whether or not it would rub on the VN750 swingarm (it doesn't). The BUBF (VN1500A) uses the same tire sizes and rim widths as the VN750.

Jim
 

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Discussion Starter #10
Comparing the two sizes the car 165/80-15 seems smaller all around than the motorcycle 170/80-15 tire. Would be interested to find out if this is true in an actual comparison. Maybe the mid-girth and Rim to Rim lip distance would make it unsuitable for replacing the 170 with a car 165 on a 3 1/2 Rim.


Specification***Sidewall****Radius**Diameter**Circumference***Revs/Mile

165/80-15******5.2in*****12.7in****25.4in****79.8in*******794 0.0%
170/80-15******5.4in*****12.9in****25.7in****80.8in*******784

Difference: 170/80-15 is 1.2% bigger than 165/80-15.
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Also, found I can order a 100/90-19 ME 880 online and shipped cheaper than the Dunlop 90/90-19 at the local Harley shop. Being a cheap-o, I'll probable order the better tire at a better price online. I've probably got a couple of seasons before I will need to replace the rear, so no hurry there, and I should know a little more of Darksiding the VN700 by then.

Noticed I was low on oil (Unknown brand in bike) yesterday while out riding. Came home and installed new filter and went with Shell's Rotella T 15W-40...for diesels they think...read some good stuff about this new "Triple Protection" oil though. :)
 

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Discussion Starter #11
The BUBF (VN1500A) uses the same tire sizes and rim widths as the VN750.

Jim
I just picked up on this, that's good news...I think. For some reason I believe there are some VN1500 Darksiders out there.
 

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Discussion Starter #14 (Edited)
I also bought a 90/19 tire for the front. How much off will the spedometer be?
I know there are posts here that the speedo will read less...I'm not saying they are wrong...and are probably right...but I just don't get it. A 90/90-19, 100/90-19, and 110/90-19 are all the same size except in the width. Correct?
Then how can a wider or narrower tire change the speedometer reading if they are otherwise the same size? If they are the same diameter I don't see how it would change the reading, they would still spin the same revs.

The online ME 880 at Superstore for cheap only has 100 & 110, but I think the slimmer 90 would look better...but yeah, less rubber on the road or a fat tire on front.
 

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I know there are posts here that the speedo will read less...I'm not saying they are wrong...and are probably right...but I just don't get it. A 90/90-19, 100/90-19, and 110/90-19 are all the same size except in the width. Correct?.


NOPE...tires differ in diameter. Not by much but enough to make a diffrence. The inside diameter is the same..but the outside diameter will be diffrent from brand to brand. Width has nothing to do with it.

Go back in this thread and look at your own posts showing diffrences in circumfrence on rear tires. Same hold true for fronts.

A bigger circumfrence means the tire will travel farther on each full revolution...this obviously would effect your speedometer as it counts revolutions of the tire.....


KM
 

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Discussion Starter #16 (Edited)
Yeah, I get that. But we're talking about a 19" front tire of equal brands.

The 90/90-19 = First 90 is width, right? Second 90 would be the hight profile from rim lip to top of tire, right? or maybe not...maybe this is my error. And 19" Rim size is 19" Rim size. The only difference I see here is the width of the tire.

90/90-19 is a little narrower than 100/90-19 (Equal tire brand), is there any other difference? I'm not a tire expert but I don't see any circumference difference or profile difference here. Only little a difference of width. That shouldn't affect the revs...

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Well, wait a minute, I think I see where I have gone wrong. 100/90-19 is not a wider tire than 90/90-19, right? It is a taller tire. I had to think in car tire terms like a 255 is taller than a 235 which is the first number. So a 90, 100, and 110 are all the same width of 90 but different (higher) profiles...different circumference equals different revs.

But now I'm not really sure since I thought 170/80-15 rear was a wider tire than 150/80-15 rear tire. Not a taller tire. Hope somebody can straighten me out on this. Just bigger all the way around? Then what about the 80 part, it wouldn't be 80 then. Oh heck, just forget about it. If the tire fits use it. :)
 

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Given a 90/90-19 tire
The first 90 represents its section width (tire width in mm). The second 90 is the tires Aspect Ratio (the ratio of the sidewall height to the tread width). The 19 represents the rim/wheel size.
So given the width on either. 90% of 100 is going to be more than 90% of 90 and less than 90% of 110. Taller sidewall height means greater actual circumference and therefore given the same revolutions on a rim, more or less actual travel down the road for a tire. It's the complete revolution of the tire that drives the speedometer sending unit that in turn feeds the speedometer.
True that a 19" rim is a 19" rim, (inner) but sidewall height will determine the circumference (outer)
 

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Discussion Starter #18
If I understand this right then a 100 is wider than a 90, all else equal. But since a 100 is wider than a 90 and goes on the same 3 1/2" Rim, it causes it to bow a little higher since it is wider and has to go somewhere.

I don't know if my thinking here is right or not, but I can understand that making the revs different.
 

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Dianna is correct, as usual. However I work for a sears auto center, and I really don't think the speedo change will be more than 1 or two miles an hour,with those tires however I have been known to be wrong before.
 

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Discussion Starter #20
Yeah, I think I get it now. Even if everything is equal except for the width of the tire, mounting a wider tire on the same rim as a narrower tire will put a slight bow at the crown increasing the diameter. Just as if you mount the narrower tire on a wider rim will decrease the diameter.

I have to look at it from a 4-wheel point of view. If you are shopping for wide tires it would help to have wide rims. Mounting a wider tire on a narrow rim will increase the diameter, same tire on a wider rim will decrease it.

Anyhow, anyone got any thoughts on this car tire for the rear of a VN700:

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Specification***Sidewall****Radius**Diameter**Circumference***Revs/Mile

165/80-15******5.2in*****12.7in****25.4in****79.8in****** *794 0.0%
170/80-15******5.4in*****12.9in****25.7in****80.8in****** *784

Difference: 170/80-15 is 1.2% bigger than 165/80-15.
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Looks to me since the 170/80-15 is bigger all around than the 165/80-15 it would be just a matter of finding the right brand of tire. I read of one person mounting this same tire on a Honda Shadow 600. I'm thinking it might work.
 
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