Please be easy on me.
I have two bikes, a Suzuki and this 900RR.
I replaced the front on my Suzuki because it was cupped bad.
I have not replaced any of the rear tires and I don't know how to check them and when to replace.
Do you need tires when there is no more grooves in the center? Is there a wear indicator?
I don't have any cords showing, I'm not that ignorant.
I just need some good advice on tires.
Brian

 

I thought I would add a couple pics.
This is my rear tire on the 900RR

This is the front. It has some slight cupping and the center seems to come to more of a point and not the even curve of a tire profile.

And this is the rear on my cruiser.
I couple use some input here.
Brian

 

i wouldn't yet.. i would buy another at this stage its still got plenty thread

 

There should be wear bars in your tires close to the centerto help you know when to replace them. I can see a wear bar in the pic of your suzuki tire. Its in the 2nd tread from the bottom on the left side. It looks like it pretty low but I can't really tell from the picture.

 

The Suzuki should be fine for this season, but the Honda came that way didn't it? They're definitely past their peak service life (especially the front), and you never know if someone patched a nail hole or something. It's cheap insurance to get new tires. I would do everything you can to up the odds of staying upright...no reason to risk all your time, effort, and life...

I just got a set of sticky, long-lasting Diablo Supersports for a little over two bills...

130/70ZR-16...$105
180/55ZR-17...$133

Whenever you get new ones, you'll see a little trio of letters that says TWI, meaning Tire Wear Indicator, so if you can't find them on the old tires anywhere...please just get new ones when you're ready to ride...