Excessive sway on Highway

[Cherokee]

Hello,

I am new to this site and I am looking to see if anyone has the same problem as me. I have a 2013 Mazda 3 GS-SKY with about 143,000kms... Yes I drive a lot.. mostly highway too and from work. Recently I have been having to fight to keep the car to stay straight in my lane... much worse on windy days or if a transport passes me. If there is not wind the car drives straight, no vibrations in the steering wheel. Any help or pointers as what is causing this instability while I am driving would be great. I have done a lot of reading on this subject and it seems to be a common enough problem.

[credential23]

If there is not wind the car drives straight, no vibrations in the steering wheel.

Lower your car or put a spoiler to reduce wind resistance and produce a downforce. Otherwise it should be normal cause mazda make cars using thin cans thus making it light :P

[r4BBiT]

Lower your car or put a spoiler to reduce wind resistance and produce a downforce. Otherwise it should be normal cause mazda make cars using thin cans thus making it light :P
Maybe some bags of sand in trunk?

[nigvlb_]

Time for some low .. needs moar downforce!

[Cherokee]

It wasn't this bad when the car was new and has gotten progressively worse with time... I still have my winter tires on 15"... Going to put my summer tires on this weekend 16" and see if that helps. While I am swapping tires gonna inspected sway bar end links and suspension components. Anything in particular I should check that would cause this sway?

[nigvlb_]

It wasn't this bad when the car was new and has gotten progressively worse with time... I still have my winter tires on 15"... Going to put my summer tires on this weekend 16" and see if that helps. While I am swapping tires gonna inspected sway bar end links and suspension components. Anything in particular I should check that would cause this sway?

I would make sure whoever is checking, check all the suspension components and control arms. Better to know if there is a flaw/issue, than not to. Not sure if this helps but i would get everything checked, especially if it has gotten worse over time.

[sarujo]

It wasn't this bad when the car was new and has gotten progressively worse with time... I still have my winter tires on 15"... Going to put my summer tires on this weekend 16" and see if that helps. While I am swapping tires gonna inspected sway bar end links and suspension components. Anything in particular I should check that would cause this sway?

15" tires are going to have very tall sidewalls and if not inflated properly will cause handling degradation. Winter tires are typically softer to begin with and then add the sidewalls....

When was the last time you had an alignment done? Are you still running your factory suspension (ie, struts and shocks)? Your mileage is getting up to potential shock/strut replacement, although your mainly highway driving may lessen the wear on these....

My 2010 with 16" wheels specifies 35 PSI (on the door sticker). I drop down to about 32/33 on my 17" summers.

[Cherokee]

I installed my 16" summer tires and still notice this wandering/swaying is the best way to describe it.. I haven't gotten a wheel alignment done on this car. When I installed my summer tires I check for play from top to bottom and frnot to back... evert hinges seemed tight. Could it just be a wheel alignment.

[nigvlb_]

Get an alignment and have everything checked out if it's still there.

[Dubcee]

Sounds like alignment, worn tires or improper tire pressure.