Different spiked winter tires in front and back, Subaru Loyale 4x4

[Tremmor]

Is it a good idea or safe to put lets say 165 80r13 tires in back and 175 70r13 in Subaru Loyale 4x4? Or should I get a pair of new tires of same size but different tread pattern since I can't get exact same tires anymore to replace one broken tire to get set of four. Thanks for help =)

[djellum]

you can mix tires in a selectable 4x4 subaru, but you should keep them in pairs.  A pair on the front and a pair in the back.  its the all wheel drive ones that are real sensitive to differing sizes.

 

that said if you have it in 4wd and have sever differences in overall diameter it can cause problems as one tire will need to slip to keep pace with the other.  you should only use the 4wd on soft terrain like dirt or gravel to keep your trans from binding so this is not usually and issue if the tires are close.

[wagonist]

you can mix tires in a selectable 4x4 subaru, but you should keep them in pairs.  A pair on the front and a pair in the back.  its the all wheel drive ones that are real sensitive to differing sizes.

 

that said if you have it in 4wd and have sever differences in overall diameter it can cause problems as one tire will need to slip to keep pace with the other.  you should only use the 4wd on soft terrain like dirt or gravel to keep your trans from binding so this is not usually and issue if the tires are close.

You have this the wrong way around.

All wheel drive models have a centre diff which can cope a little bit with different tyres sizes, but its not good as its loading up this diff. But will get you out of trouble in the short term.

 

Part time 4wds lock the front & rear diffs together, so if you have different tyre sizes, 1 end will be trying to spin faster than the other. Definitely not good.

If you're really stuck and have no option, put the bigger tyres on the front so they pull the rear. If the bigger ones are on the back, they will be pushing and so the back of the car will try to pass the front (ie car spinning)

 

Realistically, get 4 tyres the same is the best no matter what.

[djellum]

the difference is where you have the front and rear engaged.  the AWD cars will be running dry pavement with good traction and running different sized tires can cause some problems depending on the amount of difference.

 

the 4wd selectables are only supposed to have the rear engaged on "slippery" surfaces, grass, gravel, mud, snow, etc.  if you try to drive on pavement in 4wd you will bind up the trans even with 4 perfect sized tires (once you make a turn anyway).  in 2wd it won't notice at all just like any other FWD car wouldn't, and since you should be on terrain that gives easy to engage the 4wd its not a huge deal to have some tire difference.

 

Not saying its good, tires and brakes are the 2 things on your car you should never skimp on.  But if your just commuting to work and don't need the 4wd or you don't mind a little extra tire wear when your off road, then you can get away with it on a  selectable.

 

this is assuming were talking small differences not measured in inches of course.

[djellum]

for the OP, since I didn't really say it right.  best bet is to buy 2 tires the same size but different brand or pattern.  they won't be exactly the same but will be plenty close.  if you mix the sizes like you listed you should actually measure and see if they are close to the same actual diameter.  they may be very close depending on the brand or way out of whack.

 

your goal should be to have tires that are the closest in actual diameter.  the normal size rating system is only a ball park, look up each tire and get its actual diameter from the makers website so you know.  width and tread pattern matter little compared to the diameter.

[Tremmor]

Thank you for explanation! I found numerous tire size calculators and

http://www.miata.net/garage/tirecalc.html is one of them.

Would this 3.2% size difference be too much? I think it might be actually more than that if tread is more worn as these are older tires, gonna check missing spikes as well.

 

Tire Size Comparison
metric

Specification  Sidewall  Radius  Diameter  Circumference    Revs/km  Difference165/80-13         132mm   297mm     594mm         1867mm        536        0.0%175/70-13         122mm   288mm     575mm         1807mm        553       -3.2%

inches

Specification  Sidewall  Radius  Diameter  Circumference  Revs/Mile  Difference165/80-13         5.2in  11.7in    23.4in         73.5in        862        0.0%175/70-13         4.8in  11.3in    22.6in         71.1in        891       -3.2%

[djellum]

those designations of tire are generic ranges.  they can be off by a staggering amount sometimes.  you want to go to the actual specs on the manufacturers website and see what the true diameter of the tires your looking for are.

 

pick a few available brands and look them up.  you have to take into account the tread wear but normally treads arent really that deep anyway.  

 

rim width changes things as well as other variables.  its not the end of the world but you should get as reasonably close as you can.

[wagonist]

Agree with this. I've had the same sized tyres from 2 different manufacturers together & they were nowhere near the same diameter....