I'm fix'in to lace up a 21 inch rim to my 1987FLT which had a 16 inch front and was wondering if my speedo drive needed to be changed also. It's cable driven off the front wheel an all, dose a bigger diameter wheel change calibration?? Has anybody out there done this to their ol evo? Killer

 

I haven't done it to mine but you will definitely have to change your speedo drive.

 

I've always been told that it can't be done. The 16" hub has a different spoke pitch than the 21" if your talking about lacing your stock hub to a 21" rim. to answer your other question. The tire height remains the same so no you do not need to re calibrate

 

I am very interested in this so I have done a little googling here and there. The angle of the 21" wheel's spoke may on fact be different. I have not confirmed this but I see many upgrades on the sixteen to twenty one incher go from a 16x3 to the 21x2.15. This may lead credence to the angles of the spokes that the previous poster mentioned, again I don't flipping know. On the fleabay you can get a 21x3.5 48-fat spoke delivered to your door for$299.99. Panhead Rich has an excellent ongoing thread about these high value wheels. His is on a FLSTS. I'm interested in a 1998 FLTR that has a 16x3.00 double disc. This makes me nervous to lose the large...... I'll spend your money all day if you'd allow me to.

Summing it up is I know I can properly space a 2.15" width wheel to FILL my forks. How can you shrink one is what I'd like to learn.
Tom

 

Speedo drive will need to be swapped. 16"x pi vs 21"x pi. What does that give you? Less than 10% off??? You'll be measuring slower. Your defence would be: but officer it ain't the stock rim. Lol

 

Form over function or function over form. Maybe your riding style and mileage is different than mine, but I would never swap a 16" for a 21". My 16 has saved me numerous times that a 21" wouldn't have handled as well.
But, whatever.

 

While your rim size is different, the height of the two tires that are turning are the same height. Look at the difference in sidewall.

 

You are making calculations based on the rim diameter, not the tire diameter, so your logic fails.

 

Thank you

 

Just tell the officer that you travel faster than everyone else so that you don't get stuck in a blind spot.

Works down here!!!!