not trying to thread jack, but im looking at the same thing... i was considering 140/60/17 for rear and either getting 110/60/17 for front or leaving stock 110/70/17... has anyone put a shinko 006 140/60/17 on the rear ? any fitment issues a friend at a shop said he has had some people not be able to fit them without rubbing on swing arm...? seems weird that people are putting 150's on no issues, but a 140 would rub... also if you go to lower profile 60 in rear.. is it necessary to go to a 60 in the front or is 70 still ok?
When looking at tires, take a look at all of the dimensions as well. Not all tires in a particular size have the same dimensions. Make sure the tire is designed for the rim size.
You may loose approx 2 mph going to a lower profile rear tire. With a 140/70-17 you will gain 2 mph over the stock 130/70. When running a lower and wider tire it maybe necessary to slide the tire back on the swing arm a little bit. If the tire is slightly too wide, a reduction in rear sprocket size or longer chain is an option.
The Shinko Podium is a radial tire, so you should get a radial to match the front as well. Going to a 60 profile front tire means you would go up a to a 120/60 (most 120's are too big for the stock Ninja rim), so staying with a 110 front will be fine. Keep in mind that radial tires does not necessarily mean a much better improvement in handling on the Ninja 250. The bike was designed to be used with Bias-ply tires but, but people have found some radial types that do end up working OK on the Ninja 250, especially in track situations where a particularly sticky tire can be helpful.
Under no circumstances is it recommended to put a bias-ply on one end and radial on the other end for an extended period of time. Even mixing manufacturers of the same type isn't a great idea. However in extreme emergency
cases it may be necessary until a proper replacement can be had.