Can I go on driving a bit longer with worn and worn a bit more tires or will I damage my AWD?

[AylmerQc]

I bought an 07 XC 70 5 weeks ago.
The front tires are good for another year or two but the rear should be replaced, as the thread indicator on these General branded tires tell me literally.
As I'm not sure how long I'll keep the car, I thought of just replacing the two rear tires with good used ones or even go with new ones but I've been told that driving with tires that have different sizes will damage my AWD. Costco for example will not install just two tires in case of liability.
As it is, am I at risk of damaging the AWD unit by driving with the tires as they are?

[jonesg]

that was a problem on previous versions of awd, not yours.
i would guess the rears were on the front and got shipped to the rear.
does it pull to one side ?

front end is more likely to go out of alignment due to the moving parts and configuration.
check the front with string and tape measure.

[AylmerQc]

Thanks. I'm the one who put the bad ones at the back and the good ones at the front after I bought the car. I can't recall where they were before that but the previous owner had just switched his winter tires and put on these summer ones. I believe he kept track of where each one was removed the previous year as he had written FR, FL, RR, and RL on each to indicate where they were removed from last fall so I could look at those markings and figure out where they were when driven last spring summer and fall....

[MoVolvos]

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The video left out one parameter which MUST be met in order to get a correct alignment. I have attached a diagram to explain. Most cars do not have the same Track Width front and back. Assuming you don't have any suspension damage. You must establish that the Red strings are parallel so the Green lines are equal. Then you have to make sure the distance of the Red/Orange arrows in the front left and right are equal. Next the rear Yellow/Orange arrow distances must also be equal while keeping the red lines parallel, meaning green lines front and rear are still equal. You do the math.

Some cars the front track is wider whereas others it's the rear. The diagram shows the front track Blue line being wider like the 03 XC70 which should be the same as my 02 V70 XC. If you use the method in the video making the front Red/Orange and rear Yellow/Orange distance the same then measuring the front and back edge of each rim the car will be Toe Out at each wheel.

I have done enough of these over the years and can visualize the diagram so don't have to use the strings. If the rear Toe is close I just set the front Toe while centering the steering to get the alignment close so it doesn't drift or have uneven tire wear.

Then only time I've have use the string is on the 08 C30 T5 and 09 S60 AWD. The C30 as I replaced the rear camber arms with the adjustable so I had to reset the Toe and Camber. The S60 was due to replacing the driver's side rear adjustable toe arm.

2003 XC70
Wheelbase 2760 mm 108.7 inches
Track/tread (front) 1610 mm 63.4 inches
Track/tread (rear) 1550 mm 61 inches
https://www.carfolio.com/volvo-xc70-106062

This website give many spec including Wheelbase but fall short on front and rear Track Width so can mislead those trying to do a proper alignment.
https://www.ultimatespecs.com/car-specs ... T-AWD.html

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[jonesg]

Thanks. I'm the one who put the bad ones at the back and the good ones at the front after I bought the car. I can't recall where they were before that but the previous owner had just switched his winter tires and put on these summer ones. I believe he kept track of where each one was removed the previous year as he had written FR, FL, RR, and RL on each to indicate where they were removed from last fall so I could look at those markings and figure out where they were when driven last spring summer and fall....

in that case ... are they worn unevenly or even, if even they're just worn out normal.

..2 weeks ago, I found my front pass side tire was bald on the inside, I measured 1 1/2 inch toe out. ! yikes.
It scrubbed itself bald in less than 1000 miles. I adjusted the tie rod and now it has 1/16 toe in, close enough for me.
If the car tracks straight I wouldn't worry about it.
I had a bent drop link which threw it out.

[AylmerQc]

Thanks again.
I know there's a worn component, either a ball joint of tie rod end. I'll have to get that seen to, or see to it before checking the alignment.
You wrote earlier that my particular model doesn't have the same issue re needing exact same size tires as previous generations did. What changed between one genaration or year model to the next? When did the change occur?

[Krons]

I’ve had decent luck with used tires on eBay. Gotten some clearance sets on tire rack for cheap too, and they will ship free to a Discount Tire if you have one near you.

[jonesg]

Thanks again.
I know there's a worn component, either a ball joint of tie rod end. I'll have to get that seen to, or see to it before checking the alignment.
You wrote earlier that my particular model doesn't have the same issue re needing exact same size tires as previous generations did. What changed between one genaration or year model to the next? When did the change occur?

early awd would remain engaged if there was any difference in tires and blow the rear drive,
newer haldex are less prone to that.

[Krons]

exact same size tires

I should have noted many eBay sellers will indicate tread depth and tire date code to get you a ‘matched’ set of same brand/model and make sure they aren’t too old. I’ve done this when a relatively new tire was damaged beyond repair and didn’t want a mid-matched set.

[AylmerQc]

That is quite something. Most tire sellers on Facebook Market place for example, you need to ask for those specs and information...then you're lucky if they reply at all after that.