I found a 17 inch radial tire size

[BLKMAX]

Yes I changed the speedo gear after the 17 front convesion.
I tested again
70 mph = 4.1 in 5th
80 mph = 4.9 in 5th
But factors like the rider's weight and wind also play a role in speed/RPM
I am 180 Lb.

That's still better than stock.....I might have to look into upgrading to 17's.

 

[firefly]

That's still better than stock.....I might have to look into upgrading to 17's.

If you have a venture rear + a 160/70X17 you will get 80 MPH @ 3.8 or something like that. if your bike has good compression. go with the 17 WELDED kosman they are the same price as the bolted ones and might even look nicer.
Every day I ride the bike I feel very happy with my choice of that size tire
Vs the 180/55X17 that I replaced.

 

[ViciousCycle]

Another convert here to the 160/70-17 rear tire. Mine's a Bridgestone BAttleax 020. my rim is a UFO 17" by 6".
Previously had a 180/55-17. The 180 was stretched very thin on the wide rim, making the bike ride very low. New 160 tire feels like I've gained an inch in clearance and an extra gear in the transmission. Actually caught myself cruising at highway speed in 4th gear today because the rpms were where I had gotten used to them being with my old tire. Huge improvement to not have the bike turning 4000 rpm all the time.

 

[firefly]

Don't you love having the RPM lowered, much less strain on the engine, what size front wheels do you have?
Don't you think the benefits out way a fatter rear tire, do you feel the difference in tight curves?
some photos will be nice.

Another convert here to the 160/70-17 rear tire. Mine's a Bridgestone BAttleax 020. my rim is a UFO 17" by 6".
Previously had a 180/55-17. The 180 was stretched very thin on the wide rim, making the bike ride very low. New 160 tire feels like I've gained an inch in clearance and an extra gear in the transmission. Actually caught myself cruising at highway speed in 4th gear today because the rpms were where I had gotten used to them being with my old tire. Huge improvement to not have the bike turning 4000 rpm all the time.

 

[Rusty McNeil]

Yes I changed the speedo gear after the 17 front convesion.
I tested again
70 mph = 4.1 in 5th
80 mph = 4.9 in 5th
But factors like the rider's weight and wind also play a role in speed/RPM
I am 180 Lb.

But factors like the rider's weight and wind also play a role in speed/RPM

Really? Do they make the clutch slip or the rear tire spin??

Just curious.....

 

[firefly]

No the clutch never slipped or tire spin, the bike is near stock height, its only 9mm shorter than stock.

But factors like the rider's weight and wind also play a role in speed/RPM

Really? Do they make the clutch slip or the rear tire spin??

Just curious.....

 

[ViciousCycle]

Don't you love having the RPM lowered, much less strain on the engine, what size front wheels do you have?
Don't you think the benefits out way a fatter rear tire, do you feel the difference in tight curves?
some photos will be nice.

Front tire is 110/80-17 Avon Azaro AV45.
The taller rear tire is much more confidence inspiring, in part because I'm no longer grinding the front exhaust header on tight turns. I haven't really taken the tire close to its limits so far, as it's still in its break-in period. As for the fat tire look: yes, the better ride/lower rpm factor far outweighs the need to look cool.

I'll try to post some before and after pics this weekend.

Update: having trouble uploading pics. Not sure why, and really don't have time to work on it right now. I'll get to it later if time allows