My 98 FXSTC has a 150 on it, factory. The guy who sold it to me its a HD wide tire kit, even though there is no mod to the swing arm. I asked what makes it a kit, he didn't know.
Not to mention the belt guard has been modified, (a chunk cut out), to accept the wider tire and it looks like the final belt rubs on the rear tire a bit too. I think its not a HD wide tire kit as I was told, I think someone put a 150 on it and they had to make a couple of minor mods so the tire wouldn't rub.
I digress, sorry....the 150 is the widest tire my 98 will accept without making mods to the swing arm.
1998 FXSTC Softail Custom
1981 FXS Low Rider
1979 Honda CBX inline 6