140/80-15 is the stock rear tire size. It is a weird size so a lot of people get a 140/90-15 when they need a new tire, that's what I did. Then again, there's a few different tire sizes that will fit, I can't remember off hand how big you can go before having to modify the swingarm. You can get a Shinko 712 for relatively cheap, but be sure to check that you or somebody local can put it on for you. A lot of places won't put a tire on if you don't buy it from them. Back to your question, it all depends on the person. Some stick with stock, some go up in size, some get a bigger wheel size, and some put knobbies on there.

I only have 50 or so miles on mine, but it seems to handle just fine. I had no problem with clearance, but I don't know what the PO did to my motorcycle. I've heard if you hit a nice sized bump, you'll scrub. Somebody will come along after while who has had a 140/90-15 far longer than I have that can more accurately answer your question.

Thank you for the reply's.

Well, I chose the 130/90-15, Because:

 It was easier to find, and get a, ’set’, (front & rear)
Measuring the, ‘140’, vs the, ‘150’, the, ‘150’, in a, ’90’, (Could, hit the inside of fender bolts)
Different manufactures, have different, ‘actual’, withs of a, ‘140’, going, ’taller’, to a ’90’.
Which, (Might) have, required changing the bolts inside the rear fender.

So after putting on the 130/90   Found out:
Changing the, ’80’ to a ’90’, made the speed meter read closer to my GPS.
And  changing the, ‘140’ to a '130’,  it seemed just a bit ’nimbler’,  
(however that could be the result of new rubber, not, 7 year old rubber)

But Lots of people put on 140/90, and have no problems.
(Some), need to change out the ’nuts’, inside the rear fender,
for, ‘button’, head ones.

I'm quite happy with my 140/90 Michelin Commander, however a recent thread stated that some 140/90's add about 6lbs to the unsprung weight compared to a 130/90. Some advocated that the 130/90 might add to the bikes manouverabilty, others stated that the 140/90 might give greater straight line stability.

As the guy that weighed my tires, the 6 lbs increase is over the 140/80-15. If I were to do it over, I would go for the 130/90-15.  More unsprung weight is not a good idea, but now I'm stuck.  google 'unsprung weight' for an explanation.  

I think someone posted the old Norton Commando tire size as being a 110/??. 130 is plenty for a Savage.