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Linkmeister Supreme
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The speedometer is read off the front tire so the rear doesnt change it at all, just the engine rpm's per mph. On the tire size, the first number is the wideth is millimeters, second is the tire height is mm's, third is the wheel size in inches. The second number on the rear went lower which means you put a smaller diameter tire on, hence raising the rmp of the rear tire as the front stays the same. The wider the tire the lower the height is regardless if the wheel wideth stay the same. But as for the how far off is the speedometer, mine is 5 mph off at 55 acording to my GPS.
Close, but not quite right on reading what the tire size means Chuck A.
Second number is sidewall height expresed as the percentage of tread width.

Sidewall height of a 150/90-15 tire would be 150 mm X 90% = 135 mm
Move up one size to a 170/80-15 and the sidewall would be 170 mm X 80% = 136mm.

A 1 mm difference in sidewall height (2 mm difference in tire diameter) should be so small as to be impossible to tell a difference in RPM at a given speed.

The OEM front tire is 100/90-19. 100 mm X 90% = 90 mm sidewall height.
One size up is 110/90-19. 110 mm X 90% = 99 mm sidewall height.
The 9 mm increase in sidewall height is enough to notice a difference in speedo readings that most members report when changing up.
 
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My main issue here in moving to bigger tires is getting lower RPMs at the same speeds (better gas mileage),
I totally understand those thoughts, as Id like to myself.....to accomplish that, you'd need a rear of a larger OD...the front does nothing for gas milage, as it is not the drive wheel, unless you own a Rokon....

For the VN, you'd need to measure the space available with the rear shocks fully compressed....you could actually get away with a 16" rim if you replaced the shocks with non-compessable struts. Hurts my azz just to think about it...

And now, to decrese RPM at same speed, you'd need 1)to change final gearing...forget it, I looked into it. 2) add a higher 5th gear (possible, but cost not worth the result). 3) rigid out the rear and go to a 16" rear wheel...I'll pray for yer kidneys. 4) go with just a slightly larger diam rear tire, but you will have less "off the line" performance, and honestly, the result wouldnt be worth the expense IMO....if you mostly ride hiway, then ya...go for a higher profile rear tire....but you'll find out you may bog some from a stoplight (then you'll slip the clutch, and burn that out)...

For a VN to be more fuel efficient ?...go with an FI (fuel injection) system instead of the carbs, and update the antiquated ignition system for a guaranrteed good spark at all RPM ranges.

Ive gotten as much as 59 mpg with my 85, stripped and modded properly....
..a larger diam rear tire might raise me to 64 tops.
 

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Ive gotten as much as 59 mpg with my 85, stripped and modded properly....
Ok, so bottom line here is that the RPM's are essentially the same; when I noticed my RPM's higher than they were with the old tires, it really meant that I was actually rolling faster than the speedo was reading, correct?

Thank you
 

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Close, but not quite right on reading what the tire size means Chuck A.
Second number is sidewall height expresed as the percentage of tread width.
Yeh, you're right. Thought about that after I had left for work. Chaulk that one up to a brainfart. One other thing to concider on the width though is the wider the tire on the same width rim it will lower the diamter of the tire once aired up due to mushrooming the tire sidewall, not alowing it to stand up as intended. I've seen car tires at popped off the rim in a curve cause of the tire wider than the rim.
 

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when I noticed my RPM's higher than they were with the old tires, it really meant that I was actually rolling faster than the speedo was reading, correct?
If your RPMs were higher at the same indicated speed, the only thing that could cause that would have been a smaller OD rear tire. BUT....since you changed out the front too, the comparison wouldnt be visible.

Do yerself a favour...get clocked by a cop at 3 different speeds.

Your larger front, will show you going slower at same RPM....larger rear, should decrease RPM at same speed....shouldda done one at a time, lol....rear first...that'd tell ya the actual RPM drop at same speed. Then a larger front would correct the speedo error.

Sorry...I did a lot of acid back in the day....sometimes a lil tough to git the gist of what Im sayin. ;)
 

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If your RPMs were higher at the same indicated speed, the only thing that could cause that would have been a smaller OD rear tire. BUT....since you changed out the front too, the comparison wouldnt be visible.

Do yerself a favour...get clocked by a cop at 3 different speeds.

Your larger front, will show you going slower at same RPM....larger rear, should decrease RPM at same speed....shouldda done one at a time, lol....rear first...that'd tell ya the actual RPM drop at same speed. Then a larger front would correct the speedo error.

Sorry...I did a lot of acid back in the day....sometimes a lil tough to git the gist of what Im sayin. ;)
LOL - we are both saying the same thing, bro, just backward from each other. Maybe the pot got to me, too LOL :beerchug: YES, the same RPMs are now showing a slower speed. I was just curious if anyone knew exactly what the difference was. I'll have to get clocked, hopefully not in a bar. :blah:
 

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..... But as for the how far off is the speedometer, mine is 5 mph off at 55 according to my GPS.
This will have to do for now. Thanks, Chuck!
 

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According to Cycle World's road test they did on a new VN700...30 indicated was 29 actual....and 60 indicated was 55 actual. I suppose a math whiz could figure out the exponetial differences and apply a percent formula. But just a guess, 45 indicated would then show 42 actual, and inversely, 90 indicated would show 82 or 3 actual. I dunno, I did better in chemistry, lol.
 

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According to Cycle World's road test they did on a new VN700...30 indicated was 29 actual....and 60 indicated was 55 actual. I suppose a math whiz could figure out the exponetial differences and apply a percent formula. But just a guess, 45 indicated would then show 42 actual, and inversely, 90 indicated would show 82 or 3 actual. I dunno, I did better in chemistry, lol.
So, it is close to what an old post which "Diane" wrote....approx. 10 % over.

WilliamTech :smiley_th
 

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Not to be "untechnical" but if you just keep up with the flow of traffic you'll probably be fine and safer and not get a ticket. If you're all alone on the road, just don't get caught. :smiley_th

I always assumed my speedo was showing about 8-10% off but even when I would ride faster to do the real speed limit, cars were still flying past me. Now that I have the oversized shinkos, they still fly past me. So I just get in with the flow and try to stay out of their way.
 

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I have been running Dunlops for years. When I first got my Vulcan I almost slid out because of that Spitfire. It aint too round and the side edges get hard over time. Not much contacting the road. If anybody has them now I would advise getting rid of them.
 

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I dont think a 190/50 will fit between the forks...if youre talking rear, a 17 is WAY too big w/o major mods.
 

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Chasin' the blacktop
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Pirelli Night Dragon tire

Mounted a Pirelli Night Dragon 170/80/15 rear tire yesterday and took a 30 mi ride to check it out. Since they are a tad taller (and with thicker tread) than stock tires I'm showing about 2mph faster @ 5000 rpm. It makes the bike feel very light and agile on both turns and straight roads. Much more agile than the origional factory tires which I had before. I'm more confident on sharp curves but the bike seems almost too responsive on straight road, perhaps that will change after more miles.

No clearence problems once installed but since I'd heard reports of it being tough to get this wider tire past the final drive and I wanted to relube the splines I removed the final drive and mounted the wheel and final drive as an assymbly. 2 extra minutes to get it all lined up and it fits like a charm.

At this point I highly recomend this tire. If I think about it I'll update this review in a few months after a few thousand miles.
 

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Chasin' the blacktop
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Yea, Pirellis cost a bit more but a flat tire or lost traction could ruin my day so paying an extra $30 is worth it to me for giving my butt a little more safety. I'll just drink cheap beer for a few weeks to make the money back.
 

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Thanks for the post! I have 200's on my 900 and I always wanted to see a comparison between tire sizes since I'm a visual learner.
 

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Mechman53
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Clearance

Well, I purchase the Metzler ME 880 Marathon tires and since I had both stock and the upsized tires available I snapped a few shots for comparison.

Front - Upsize 110/90 - 19 on the left; Stock 100/90 - 19 on the right




Rear - Upsize 170/80 - 15 on the left; Stock 150/90 - 15 on the right


Did you have plenty of clearance.
 
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