can anyone tell me wats the biggest tire I can put on a 2000 superglide without mods. thanks

 

You probably mean "on the stock rim".....I'd say a 150 maybe; I've got a 160/60R18 on the back of my '01 FXDXT; it's tight but it fits, all I did was shave down the strut bolt heads a bit to be sure of clearance; been 2 years (and a couple of tires) with no problems.