Wheelbase is a measurement from the center of the front tire to the center of the rear tire, therefore, axle to axle. If I'm wrong let me know, but that's why I don't think the size of the tire would make a difference, because wheelbase measurement only takes into consideration the center of the tire, not the front (or rear) edge.

 

I'm sure you are measuring it correctly, as am i, but you are forgetting that the it is measured with an imaginary line down to the floor. the extra 2 inches in diameter is pushing the "rake" out that roughly half inch difference in wheelbase. I have been known to be wrong, but I think this is the way it is done.

 

More rake will push the front axle farther away from the rear axle. And we're talking less than 1/2" in wheelbase between the XL883 and the XL1200C.

 

883 and 1200 are same frame, wheel base on all like families XL, XLR, XLC and Low models is the same from 883 to 1200, the one difference is the Customs and they are the same from 883 to 1200, larger front tire would if anything shorten wheel base.

 

Back in the 70's, when my brothers and I were into choppers there was three things people would do to modify the front ends:

1. Cheapest method: Install longer fork tubes. This would extend the front end but lift the front of the bike up so that you'd damn near slide off the seat.

2. Next best method: Install longer forks combined with raked triple trees. The 3-5 degree trees would lower the front while kicking the wheel out there. Downside - it would mess with your front-end geometry making turning at slower speeds kind of freaky if you put in more then a few degrees.

3. The best method: Cut a chunk out of the upper frame rail and then heat the down tubes, shove a pipe into the neck and bend it back allowing you to change the neck angle. Results: long, low riding machine, awesome frontend kicked out as far as you were willing to go (and some of them definitely went out there) outstanding highway riding due to all that caster and, finally, absolutely terrible low-speed handling (they were a beast in parking lots) - CWO

 

The front end shortening kit for XL's is the stock length for 96-98 XLC's. The `99's have more rake than the `98 via visual comparison -the 99`s appear to be a couple of degrees as a rough guess. My guess is that the gooseneck rakes are the same, with the difference between the `99 and `98 being the rear shock length and the fork springs -spacer. My `99 has a 19" wheel and the rake matches that of the `98. Can anyone confirm the length of the stock `98 XLC shocks? Mine are at 11.5". Anyone out there w/11.0" shocks on their XLC? I was wondering about belt guard clearance