Will fork legs from a 2014 Streetglide fit on a 2010 streetglide?

 

No I don't think so.

 

Different diameters

 

No. You would have to modify the entire front end. Different diameter. You can improve your 10 front end a lot just by changing the fork oil to a different weight, and even further by upgrading the fork leg internals if that's your goal

 

Yes - after you lighten your wallet by about $3k plus the forks

There are kits to do it. Search Howard and One Fast Harley.

 

I have changed the internals on every Harley I have ever owned. It makes a huge difference especially on a touring bike. I always go with Progressive Suspension internals and use Screamin Eagle performance fork oil.
Just did it on my 07 Streetglide can't wait to test ride it. Went 1 inch lower and really stiffened up the front. I have never been a fan of the front end dive while braking with the stock suspension.

 

Why would anyone be a fan of the front end dive when braking? Is there any benefit to it?

 

If you swap the trees as well you may be able to make it work, but I haven't seen anyone who has done it. Howard, previously mentioned and of HDF sponsor Motorcycle Metal, sells a kit that takes 49mm forks and adds Ohlins fully-adjustable cartridges to them and supplies new trees to fit your bike.

 

I believe Howard uses his own CNC triple trees. I don't think the OEM trees will swap over.

 

You're quite right, but his conversion predates the 2014 Touring bikes and he based his conversion on Dyna 49mm forks, before the MoCo updated the range with 49mm forks and their own new trees.