I'm not sure if I'm being paranoid or not but I'm sure my tyres have had it. They still seem to have plenty of grip but those cracks don't look so good to me!









If they do need replacing, What is the widest rear tyre you can put on the stock rear rim and what are the benefits?

If you are concerned about its condition.......change it!

Or you can take the other option and wait for someone who you think is competent and knowledgeable enough to make the call based just on a few photos come along, say "its ok" and make all your worries go away.

Your call 

I See the point you are making, though I just wasn't sure if I was being paranoid.

To be honest I'm not sure what the average lifespan of a Tyre is - They still grip fine and I havn't noticed anything odd with them but the cracks don't look too good. I Think i'll get them replaced.

Though my question still stands about the tyre width though.

That tyre is too old. It is time to go. It may be OK at low speed but could "separate" at speed in hot weather.

I'd consider the date of manufacture as noted on the tire as a factor in deciding how old a tire is and how long to use it.  Some say life of motorcycle tires is about 5 years and some say about 7 years, depends a lot on how they've been stored after manufacture and after use.  I bought a 97 GS new in 99 that had sat on the showroom floor for 2 years and the B'stone tires were cracked worse than your pics show with only a couple miles on the clock.  Never hurts to be conservative on motorcycle tire decisions. 

A 150/70 rear tire will fit on the stock rim and have clearance all around except it might touch the brake brace bar requiring it to be bent a little.  The 140/70 and 140/80 will fit without mods.  All of the 10 different size tires I've used on my GSs have been approved by the tires maker for fitment on a 3.5" wide rear rim except the 150/60:

http://img.photobucket.com/albums/v443/jcp8832/GS500tirelogs_zpse04c1f44.jpg

A couple of 150s I've used:

Wow, Thanks for that graph jack! Very helpful!

Do you notice any benefits with a wider tyre or is it more of a look thing?

I just want to point out: ultimately, it is up to the tire manufacturer to determine their recommended rim width. Find a tire you like / can afford, and see if the manufacturer says it will fit.

Hey Jack, you have probably answered this question before but what did you think of the Shinkos? Some people don't like them and others say "they are OK". Not too many rave about them. 

Macka

I think the Shinko 006 I have is a decent tire but it has a very average compound and is not a performance tire like most that come in the 150/60 size.  I had tried a lot of tires in all the sizes I would consider practical for a GS500 except a 150/60 and when I wanted a lower rear tire a couple years ago and my local place had that Shinko I tried it.  The 150/60 is the same diameter as the 130/70 stock size.

I currently have a 140/70 Roadrider and the 150/60 Shinko mounted, I have an extra sets of wheels, and I think the Roadrider is the better all around handler of the two.  Still think the bias Lasertec front and radial RoadAttack rear I had on a few years ago were the best all around handling tires I've had on my GSs.  The stability of the Lasertec on all types of surfaces and the performance of the RoadAttack which was stickier than most sport touring type radial tires.