hey im with frosty here,use the stock width though,all you do with a wider tyre on a stock rim is wear out the centre faster,and comprimise your lean angles,im running a bt45 on the front and a spitfire on the rear,if im keen i scrape both pegs,i did have a bt45 rear but went spitfire when it was changed,i like the solid centre tread,i also have alloy "sun rims"i like my skinny rear tyre.