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There's been a lot of discussion on forums about the factory speedometer and odometer error on the VN900 bikes ever since they were introduced.

After some quick math, I decided to change my 900LT to a 170/80-15 instead of the stock 180/70, because the 170/80 is about a centimeter (.4 inches, 3%) taller in radius, and the bike sits that much higher.

With the new 170/80 rear tire, the odometer reads 2% under, that is, 100 mile post miles clocked 98.1 on the odo.

With the new tire, the speedo reads 4% high, that is, 50 mph true reads 52 on the dial.

Handling is fine. Bonus is that, for the MT66, the 170/80 was $20 cheaper, and a better match to the gauges.

Methinks that the 170/80 may be the tire the gauges were designed to, but that marketing, "widest tire in its class" and an objective of low seat heighth, trumped engineering.

I actually realized about a 5-6% change instead of the calculated 3% because I was going from a tire with 20% tread to a new tire.
 

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That's pretty much the same as the sprocket. It will vary as the tire wears out but not much. Just got back from Eureka Springs, AR. 4-5 hours one way trip, lots of nice curvy riding while there. Really glad I had the bikes rpm down for the 70-80 mph sections.
 

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Somehow we all glossed over this post. SAME RESULT AS A PULLEY CHANGE, AND A TIRE REPLACEMENT TOO!
HMNNNNN.
 

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Don't get your point. Can you change gearing by changing the size of your rear tire? Yes. Does it change the way your bike sits, ground clearance and such. Yes. Is that better or worse? Depends on the user. Heck, I'm running the Darkside I'll not criticize someone else's tire desires.

I hadn't researched a likewise sized car tire for the use on my bike. Heck, I was looking for Narrower but in the end I'm happy with whats running. But if you want to fix your Speedo by changing tires, go for it.

And as far as engineered around the different tire, no, the speedo is off because they wanted it off.
 

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Don't get your point. Can you change gearing by changing the size of your rear tire? Yes. Does it change the way your bike sits, ground clearance and such. Yes. Is that better or worse? Depends on the user. Heck, I'm running the Darkside I'll not criticize someone else's tire desires.

I hadn't researched a likewise sized car tire for the use on my bike. Heck, I was looking for Narrower but in the end I'm happy with whats running. But if you want to fix your Speedo by changing tires, go for it.

And as far as engineered around the different tire, no, the speedo is off because they wanted it off.
Maybe it's me that's missing something,
If one was considering the scootworks front pulley for instance, wouldn't it be advantages to just replace your tire( assuming it's worn out) with the aforementioned tire, and achieve the same results? Thus, saving a tremendous amount of money in the process?
It's not just a speedo fix, but would drop your rpm's damn near equivalent to the pulley. (I personally don't care if my rear tire is the "widest in it's class")

Btw, the speedo error never concerned me, nor has it ever baffled me. Every vehicle reads high, it is, and always has been a typical manufacturers embellishment, hence the unofficial 10 mph radar "forgiveness" by the cops. Yes, even law enforcement is in on the conspiracy...lmao.
 

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Yes, you could go to a different tire and just remember to use the same size the next time you replace. Probably won't even notice the difference in handling of the bike. The pulley is an expense that can be avoided that way. However, you may not be able to get your dealer to go to a non-listed tire, but then again, my dealer put my CT on for me last time so even that may not be a deterrent.

It is definitely an option, one I didn't think about before I had bought and mounted the pulley. I think the most important thing is to get the highway RPMs down regardless how you do it.
 

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My dealer installed the Metz 200/70-15 for me, and I get a noticeable decrease in RPM vs. speed. I'm not sure how true the speedo reading is now, as I haven't checked myself with a GPS. Heck, I don't even own a GPS. I do know that I've enjoyed the slight performance change, and don't mind leaving ol' Redemption in 4th gear around town now. The MPG showed a slight increase, but that could be due to my riding style for that tank... :D As far as handling? I didn't notice anything different at all.

I'd be curious to see a list of before/after RPM and speed readings with the stock Dunny and a similar list with the bigger Metz, but it's too late for me to create the before list, and I don't wanna buy a tach and GPS just to create the after, LOL.

I do agree with MrClean though, in the important factor being decreasing those highway RPM's a bit, if for nothing more than rider enjoyment!
 

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Dude I Love my 200/70-15...I get a lot of complements too. If I get time I'll put out my GPS and see what the difference is and post the findings. It will be nice to know how fast i'm going....Although, i'm always speeding anyways.
 

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The thanks goes to MBWARNER.
I realized the significance of this post and resurrected it if you will.
We can save a lot of money bringing rpm's down just by a simple tire change. (read his first post).
 

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Ok, now Im confused. MBWARNER put on a 170/80-15 instead of stock 180/70-15 and reduced the rpm at speed, Then SKETSO said he put on 200/70-15 and had a noticable decrease in rpm vs speed.
I'm no tire expert and I just put on the size that came on the bike originally. Which size should I put on to reduce the RPM as stated??? both are different than original tire so I want to make sure.
I already have the Scootworks front pulley and it has made a big difference. I just wanting to be sure before I change the rear tire size as I need a new one now and was going to order one last week anyway.

I appreciate all the experience you guys have. This is a great forum.
 

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I'm not sure what Sketso is referring too, he simply put on a wider tire, mbwarner put on a taller tire, thus, it takes longer to revolve, ergo, dropping the rpm's.
 

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You can put a taller tire like a Metz 200/70 15 to lower the RPM's or you can go with a Scootworks pulley, but you cannot do both. I chose the tire mod for my 900.
I only changed the front pulley, so adding a taller rear tire cant be done? why not? what am I missing.

would it not be the same as adding the rear pulley? Kinda.
 

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Putting on the scoots pulley moves the rear tire forward. Putting on a taller tire would probably have you hitting on the front inner mud flap. You could work on that. but without modding I don't believe there would be enough clearance for the taller tire.
 

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Putting on the scoots pulley moves the rear tire forward. Putting on a taller tire would probably have you hitting on the front inner mud flap. You could work on that. but without modding I don't believe there would be enough clearance for the taller tire.
I believe the tire moves forward enough to interfere with the frame as well.
 

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Putting on the scoots pulley moves the rear tire forward. Putting on a taller tire would probably have you hitting on the front inner mud flap. You could work on that. but without modding I don't believe there would be enough clearance for the taller tire.
I did think of that and as writing this response I realize adjusting the shockabsorber would only raise the height an not the distance.
Is there another belt maybe that I'm not aware of?
 

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Tire____________170/80-15___180/70-15___200/70-15
Sidewall Height____5.35________4.96________5.51
Section Width_____6.69________7.09________7.87
Overall Diameter___25.71______24.92_______26.02
Circumference_____80.77______78.29_______81.76
Revs per mile_____784.49_____809.27_____774.99

Tire Comparator
 

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Tire____________170/80-15___180/70-15___200/70-15
Sidewall Height____5.35________4.96________5.51
Section Width_____6.69________7.09________7.87
Overall Diameter___25.71______24.92_______26.02
Circumference_____80.77______78.29_______81.76
Revs per mile_____784.49_____809.27_____774.99

Tire Comparator
It seems the middle number not only denotes height, but is a ratio between the width and the height. So, extrapolating from this data, one discerns that the wider tire DECREASES rpm's much the same as the thinner tire does. However, all that being said, I resurrected thid post so some could consider tire change as an alternative to the finicky and expensive scootworks pulley. When my oem Dunlop has run it's course, ahem, I'll change tires keeping an eye to decreased rpm's. Saving money in the process.
 

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Didn't mean to open that big a can of worms. But that is good information.

Looks like I will stay with the stock size tire for now. Thanks.
 
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