I have a stock 07 HHR, 2.4.. with stock struts.. need to replace so just thinking about if I change to a complete shock/strut with new coil.. if there were a coil that had a smaller diameter I would not have a problem putting a taller tire on the front... any thoughts with the HHR Guru's ??? maybe the after market 08 HHR SS struts ???

 

Misread your question, in addition to a spring with a smaller diameter, you'd also need a strut with a smaller lower spring perch.

Any tires bigger than about 26" in outside diameter will foul their inner sidewalls on the spring perch, changing spring diameters opens up a big can of worms...like spring rates etc.

 

Attachment 14664
Stock SS strut w/pedders spring

As Mike said, the taller tires will hit the spring perch.
To go to a smaller coil/spring perch, I think you would have to swap to coilovers.

 

THANKS guys.. I was out of town with the FIRE DEPT... I will be tearing down the front end next weekend found out not only were the struts worn but the lower control arm mount bushing were also wore out.. as in when I took off or stopped the whole tire would move about 1 - 2 inches.. and would sound like the whole front end was about to fall out when going over bumps in the road...

BUT JUST TO LET YOU KNOW YOUR WORDS OF WISDOM DID NOT FALL ON DEAF EARS ...

 

OP - Check the How-To section for a posting on replacing the lower control arms - not a fun job, but it's do-able. You can either replace just the bushings or replace the whole arm with a new one that comes complete with bushing and a new lower ball joint.