Uneven contact wheel wear?

[Dave Armour 38]

Built a 2x72 grinder a couple years ago. I just noticed that the contact wheels are wearing unevenly. The top wheel (3” diameter) is the worst. It is basically square for the first inch. Then it has worn down just over 1/8”. The bottom wheel (8”) is about half of that. The wear is on side closer to the frame. Trying to figure out the cause. I will say due to work picking up I’ve ground more in the last 4 months than I did probably in the previous year+. Attaching a couple of pics. 

[Larry Pyne 49]

I don't have a 2x72 yet so this may not apply but on my little 1x30 I was using the small wheel at the top to grind directly on.  It has a rubber coating like your wheel and I think that the heat from the blade during the grind damaged the wheel.  I don't know if you have ground directly on those wheels but if you have then maybe that's what happened?  If not then I have no idea other than the belts may have more tension on one side than the other but I think that may be unlikely since there are 5 wheels on your sander and I'm sure you would see one side flopping around versus the other. 

[Jeremy Blohm 511]

The only thing I can think of that might cause any issues is the C-clamp. I understand work arounds. I had to do a lot of tweaking to get mine to run right. What I am thinking it the C-clamp looks like it may have slid up a little and and is causing a little twisting action to happen.can we get a picture of the other side to maybe help do a further inspection?

[Dave Armour 38]

Thanks. Here’s a pic of the other side. 
 

For some reason the pic keeps loading upside down. Not sure how to fix that. 

[Alan Longmire 2,750]

Definitely an alignment issue, as in the small wheel axle is not parallel with the belt under tension.  How's the tracking?   I'm going to guess that it was fiddly when you first built it, but now holds pretty steady once the small wheel wore in?  

[Jerrod Miller 445]

Being a contact wheel, I have to ask:  Do you often use one side more than the other when shaping?  

[Dave Armour 38]

3 hours ago, Alan Longmire said:

Definitely an alignment issue, as in the small wheel axle is not parallel with the belt under tension.  How's the tracking?   I'm going to guess that it was fiddly when you first built it, but now holds pretty steady once the small wheel wore in?  

It was never really touchy tracking wise, but it definitely is less sensitive than it was. I’ll recheck things. Thanks