How would one find out if a tire is cupping because of a defective strut/shock or if its from a broken steel cord inside the tire itself from hitting a pothole or something.

 

Usually cupping on the tires are bad shocks/struts. Have someone follow you in another car and see if yours tires are bouncing around on a semi bumpy road.

 

Out of balance tires check that

 

to check the struts, go to each corner of the car and "bounce" the car up and down it should only bounce once and stop if it bounces 2 or more times that strut is dead

 

if the steel belts inside of the tire to seperate..it would cause the tire to create a lump/hump in it..sometimes its noticeable and sometimes its not just by looking at it...

tire cupping is more likely a mechanical issue with the cars suspension or misalignment

i know about these things cuz im a tire tech.

 

I have never heard that cupping could be bad shocks?

Always thought it was alignment or twisted frame issues?

 

Well I did the bounce trick and it still seems quite firm. Is that a good sign that the strut is fine? Would a bad strut be very noticeable? Ride quality also seems fine.

 

What do you mean by cupping? Post pics.

I've always thought of cupping as a classic example of bad toe alignment. By cupping, do you mean that some blocks are shorter than others on the tread pattern? Like some of the blocks are being worn more? If so, that's toe.

As shown here, although this diagram makes it look a lot worse than it usually does:


Is it on the inside of the tire? If so, that's toe out, as shown here:


If it's on the outside, that's toe in.

Do you mean that your tire has a bulge in it? If so, that's a broken belt.

I'd always start with checking alignment on any tire wear issues.

 

Yes it was as in that picture of the tire and it was on the inner side of the tire.

I went ahead and got new tires and alignment, so I guess if the problem persists again then it means the strut is bad. (Although ride handling is still fine, even if it is a bad strut)

 

i had a bad ball joint that caused my rear tire to cup very badly

 

Tire cupping is caused by worn out or improper functioning suspension parts. It is typically the struts that are blown allowing the tire to bounce too much, cupping the tire. The ball joints which are attached to the suspension going out will produce the same problem just usually as a slower rate.

A tire/wheel being out of balance will not typically cause the tire to cup, it will make the tire out of round and lop-sided.