AWD vehicles & tires (1 Viewer)

[STEADYMOBBIN 22]

So I’m fairly knowledgeable about vehicles but I learned something new with my wife’s AWD Ford Edge...

So apparently you have to replace all 4 tires as opposed to just replacing 2 at a time. If you tires are as little as a half inch difference it can wreck havoc on your drivetrain. 

The Ford edges also have a notoriously stupidly small transfer case which is pretty much a given that will fail and that you have to replace.

 So besides my public service announcement about that, my question for you smarter car nerds is what the effects of slightly smaller tires will do? If the stock truck tire is a 245, can I cause damage by putting on 235? 

 

[[scooter]]

You won't cause any damage by switching to 235 tires, but it will have a slight effect on your MPG and your odometer/speedometer reading, and you may notice a slightly stiffer ride.

Also, the "4 new tires" thing is a bit of a myth. You can get away with replacing 2 at a time as long as the treads are a close match. You can even get some tire shops to "shave" a new tire to make it match the other tires on the car.

 

[belljr]

You won't cause any damage by switching to 235 tires, but it will have a slight effect on your MPG and your odometer/speedometer reading, and you may notice a slightly stiffer ride.

Also, the "4 new tires" thing is a bit of a myth. You can get away with replacing 2 at a time as long as the treads are a close match. You can even get some tire shops to "shave" a new tire to make it match the other tires on the car.

Yep. Recommend no more difference than 3/32. Some places will shave.  And some makes and models don't require all 4

 

[Dragons]

You can also buy many tire models "used" at a specified tread thickness, so you can replace 1 tire instead of 3.

 

[Bossman]

So I’m fairly knowledgeable about vehicles but I learned something new with my wife’s AWD Ford Edge...

So apparently you have to replace all 4 tires as opposed to just replacing 2 at a time. If you tires are as little as a half inch difference it can wreck havoc on your drivetrain. 

The Ford edges also have a notoriously stupidly small transfer case which is pretty much a given that will fail and that you have to replace.

 So besides my public service announcement about that, my question for you smarter car nerds is what the effects of slightly smaller tires will do? If the stock truck tire is a 245, can I cause damage by putting on 235? 

This is hard to follow ...

Tire shops will have you believe that because the front and rear wheels are "linked" due to the AWD, they must turn at the same rate or it will cause binding.

I believe this to be mostly bs ...  and a nice tactic to sell you 2 tires that you don't need.

.... unless the tires are severely different. Front and rear differentials provide "slip", for taking corners and such, that allow one wheel to turn at a different speed than the other.

I have read that Ford and Subaru are more sensitive than most in this regard though.  

Not sure why you're considering smaller tires on your wifes Ford Edge?

Is she having a hard time getting into it and you want the car lower to the ground?

... or do you feel that the smaller tires would be less stress on the weak Ford transfer case?

... or are you trying to match 245's that are worn out???  235's on sale????

 

[STEADYMOBBIN 22]

... or are you trying to match 245's that are worn out???  235's on sale????

Yes, they were on sale and in stock. 

We replaced all four yesterday.  Her transfer case was already a little jacked up and made some noise, but with the new tires on it makes significantly more noise. 

 We haven’t replaced the transfer case because everything I’ve read says that they go bad inevitably anyway. So if it’s working, we’re just gonna leave it alone until he gets worse. 

 

[STEADYMOBBIN 22]

You won't cause any damage by switching to 235 tires, but it will have a slight effect on your MPG and your odometer/speedometer reading, and you may notice a slightly stiffer ride.

Also, the "4 new tires" thing is a bit of a myth. You can get away with replacing 2 at a time as long as the treads are a close match. You can even get some tire shops to "shave" a new tire to make it match the other tires on the car.

Thanks, yeah she needed all four new anyway so...

 

[STEADYMOBBIN 22]

You can also buy many tire models "used" at a specified tread thickness, so you can replace 1 tire instead of 3.

The four tire thing might be a myth but I’m sure you should never replace just one tire. 

 

[Dragons]

The four tire thing might be a myth but I’m sure you should never replace just one tire. 

If you're replacing it with the same model tire with the same tread, why not? And how is it different than "shaving" a new tire?

 

[[scooter]]

... or are you trying to match 245's that are worn out???  235's on sale????

Yes, they were on sale and in stock. 

This is a common tactic with tire stores. They don't want to lose your business because 245s are out of stock, so they give you a slight discount on the 235s to get you to stay. Usually it's not a big deal, although I had a tire store put significantly larger tires on my car once (without authorization). I came back the next day and told them that they needed to give me the correct tires or they needed to give me a refund. They wouldn't agree to either condition, and they claimed that the larger tires were "no big deal". (Yeah right -- no big deal except when I hit a bump and the tires rub into the fenders.)

I informed the manager that I would be disputing the charge with my credit card company (since the receipt clearly showed the smaller size). The manager promptly agreed to give me the correct size, but since the smaller tires weren't in stock, I'd have to wait a week. I told him that the offer wasn't acceptable. Then he finally agreed to upgrade me to the all-weather tires in the correct size, at no additional cost. I agreed.

 

[Bossman]

Yes, they were on sale and in stock. 

We replaced all four yesterday.  Her transfer case was already a little jacked up and made some noise, but with the new tires on it makes significantly more noise. 

 We haven’t replaced the transfer case because everything I’ve read says that they go bad inevitably anyway. So if it’s working, we’re just gonna leave it alone until he gets worse. 

OK, wasn't getting that part in the op.

Like others stated, shouldn't damage anything if they are all 235.

... but the 235's, being slightly smaller, will have the tire spinning faster to achieve the same speed as the 245's.

which will also have the jacked up transfer case spinning faster. Probably not a good thing.

Your engine RPM's will be slightly higher (less fuel economy but very slight) and your speedometer will be off maybe 3 mph at highway speed 

(spedo will show faster than what you are actually going. So maybe less speeding tickets for the misses if she thinks she's doing 75 and radar gun reads 72)

Some navigation (Google Maps?) will show your speed and you can compare to the spedo to confirm the difference. 

eta: The one positive about a smaller tire is more torque = faster takeoff. Not sure if one tire size would be very noticeable though.

 

[STEADYMOBBIN 22]

This is a common tactic with tire stores. They don't want to lose your business because 245s are out of stock, so they give you a slight discount on the 235s to get you to stay. Usually it's not a big deal, although I had a tire store put significantly larger tires on my car once (without authorization). I came back the next day and told them that they needed to give me the correct tires or they needed to give me a refund. They wouldn't agree to either condition, and they claimed that the larger tires were "no big deal". (Yeah right -- no big deal except when I hit a bump and the tires rub into the fenders.)

I informed the manager that I would be disputing the charge with my credit card company (since the receipt clearly showed the smaller size). The manager promptly agreed to give me the correct size, but since the smaller tires weren't in stock, I'd have to wait a week. I told him that the offer wasn't acceptable. Then he finally agreed to upgrade me to the all-weather tires in the correct size, at no additional cost. I agreed.

I didn’t feel like opening this can of worms but I buy all my tires at a used tire place. Essentially I have been buying the same tires which run $350 for $50 each. I’ve done this for my wife’s car since she’s had it and I’ve been going to this place for the past 15 years and never had a problem.

I squally call ahead about a week in advance so they have what I want ready when I come in. I just forgot this time and I had already put it off for too long. 

 

[Bossman]

I didn’t feel like opening this can of worms but I buy all my tires at a used tire place. Essentially I have been buying the same tires which run $350 for $50 each. I’ve done this for my wife’s car since she’s had it and I’ve been going to this place for the past 15 years and never had a problem.

I squally call ahead about a week in advance so they have what I want ready when I come in. I just forgot this time and I had already put it off for too long. 

LOL ... and they get these $50 tires for free when they talk AWD owners into changing all 4 tires when they only need 2.

Nobody asks for their used tires back even if they have a good amount of tread left on them.

In fact, most tire places will charge a couple buck to "dispose" of them.

 

[STEADYMOBBIN 22]

LOL ... and they get these $50 tires for free when they talk AWD owners into changing all 4 tires when they only need 2.

Nobody asks for their used tires back even if they have a good amount of tread left on them.

In fact, most tire places will charge a couple buck to "dispose" of them.

I don’t know where they come from. I’ve seen stories of tires being “remade” but I’ve never had a problem with them. 

I rotate my tires every other oil change ( and I still change my oil with fully synthetic every 3k miles) so they aren’t getting them from me. 

 

[snellman]

This is hard to follow ...

Tire shops will have you believe that because the front and rear wheels are "linked" due to the AWD, they must turn at the same rate or it will cause binding.

I believe this to be mostly bs ...  and a nice tactic to sell you 2 tires that you don't need.

.... unless the tires are severely different. Front and rear differentials provide "slip", for taking corners and such, that allow one wheel to turn at a different speed than the other.

I have read that Ford and Subaru are more sensitive than most in this regard though.  

Not sure why you're considering smaller tires on your wifes Ford Edge?

Is she having a hard time getting into it and you want the car lower to the ground?

... or do you feel that the smaller tires would be less stress on the weak Ford transfer case?

... or are you trying to match 245's that are worn out???  235's on sale????

I have worked at an auto dealership for 20 years and I can tell you with certainty and from experience that if you do not replace all 4 tires on an AWD or 4WD vehicle that it will do damage to a drive line if there is enough difference in the tread depth between the tires.

We have had to put transfer cases and rear differentials in vehicles due to customers only replacing 2 tires at at time on an AWD or 4WD.  What started as your attempt to save a few hundred could end up costing you thousands in the long run.  

We will gladly put on only 2 tires, but you will sign a waiver that we are not responsible for any damage that may happen due to you only putting 2 tires on your vehicle.  Let's face it, the majority of the time, if you need 2 tires, your tires are worn enough that you are going to need all 4 anyway.

 

[Bossman]

How's their theory on AWD cars having all the EXACT same tire diameter ...

when my wifes 2015 Lexus IS350 AWD comes with different size tires front to back.

Yeah, first time I went to rotate the tires I was like.... aaaah     ... well this isn't going to work.

 

[Bossman]

I have worked at an auto dealership for 20 years and I can tell you with certainty and from experience that if you do not replace all 4 tires on an AWD or 4WD vehicle that it will do damage to a drive line if there is enough difference in the tread depth between the tires.

We have had to put transfer cases and rear differentials in vehicles due to customers only replacing 2 tires at at time on an AWD or 4WD.  What started as your attempt to save a few hundred could end up costing you thousands in the long run.  

We will gladly put on only 2 tires, but you will sign a waiver that we are not responsible for any damage that may happen due to you only putting 2 tires on your vehicle.  Let's face it, the majority of the time, if you need 2 tires, your tires are worn enough that you are going to need all 4 anyway.

How's their theory on AWD cars having all the EXACT same tire diameter ...

when my wifes 2015 Lexus IS350 AWD comes with different size tires front to back.

Yeah, first time I went to rotate the tires I was like.... aaaah     ... well this isn't going to work.

Lexus IS specs

225/40YR18 Front 

638mm Tall // 2002mm circumference // 804 revs per mile

255/35YR18 Rear

635mm Tall // 1996mm circumference // 806 revs per mile 

 

[Bossman]

I don’t know where they come from. I’ve seen stories of tires being “remade” but I’ve never had a problem with them. 

I rotate my tires every other oil change ( and I still change my oil with fully synthetic every 3k miles) so they aren’t getting them from me. 

You should get 7k out of full synthetic. You're draining good oil! (and expensive oil too)

What kind of car still recommends oil changes at 3k? Saving on tires, don't waste it on oil.

 

[Charlie Harper]

If you rotate your tires this shouldn't be a problem right? 

 

[dkp993]

So I’m fairly knowledgeable about vehicles but I learned something new with my wife’s AWD Ford Edge...

So apparently you have to replace all 4 tires as opposed to just replacing 2 at a time. If you tires are as little as a half inch difference it can wreck havoc on your drivetrain. 

The Ford edges also have a notoriously stupidly small transfer case which is pretty much a given that will fail and that you have to replace.

 So besides my public service announcement about that, my question for you smarter car nerds is what the effects of slightly smaller tires will do? If the stock truck tire is a 245, can I cause damage by putting on 235? 

Others have addressed the all 4 tires thing here (and bossman is correct) .  But your 245 vs 235 question the responses haven’t been totally accurate.  The difference between those two tires Is width not height. So the tire wouldn’t be smaller it would be narrower.  Now it could be smaller if it was of equal aspect ratio, which is the other number.  So a 245/50 would be wider and taller then a 235/50.  But a 235/55 would be similar in height.  

 

[irish eyes]

You should get 7k out of full synthetic. You're draining good oil! (and expensive oil too)

What kind of car still recommends oil changes at 3k? Saving on tires, don't waste it on oil.

Exactly, no way you should be changing every 3000 on full synthetic. Double the miles on synthetic at minimum.

 

[STEADYMOBBIN 22]

You should get 7k out of full synthetic. You're draining good oil! (and expensive oil too)

What kind of car still recommends oil changes at 3k? Saving on tires, don't waste it on oil.

Exactly, no way you should be changing every 3000 on full synthetic. Double the miles on synthetic at minimum.

Habit I guess. Maybe I should stretch it out to 5k but no way I’m going 7. 

 

[Slider]

You could easily go 10k with synthetic. The filter would be the weak link if anything. 

When was the last time you heard of an engine going bad? Mostly it's no oil or something breaks. Never is it old oil.

 

[Bossman]

Habit I guess. Maybe I should stretch it out to 5k but no way I’m going 7. 

Use cheap oil if your going to change it that often. No point wasting money on full synthetic.

Check your owners manual and see what it recommends. Many newer cars say 7k.

I go 10k with full synthetic. 230k miles on a 2005 Honda Pilot and 120k on a 2009 Tundra ... buy maybe you drive a Chrysler product? :azingaa:

 

[matttyl]

I just change (with full synthetic) every fall and spring, that way I don't have to track miles - and I don't have to get under my cars in the garage when it's below freezing or 90+ degrees.  Also will do tranny fluids in the spring, and t-case/diff. fluids every even year in 4wd vehicles.

Anyway, on the OP - my RAV4 is AWD at low speeds and then 2WD once over like 15 mph (unless locked in by button on dash) - not sure if that's technically AWD or 4wd.  Anyway, since it's 2wd the majority of the time, I shouldn't have any issue with tire differences (even though I rotate and try to change all 4 at a time if possible).  Thanks, I'll hang up and listen.

 

[dkp993]

Habit I guess. Maybe I should stretch it out to 5k but no way I’m going 7. 

Yeah the 3k thing is a very old school habit.  2 things have changed dramatically since that line of thinking.  Oil technology and the general quality of engine building.  Both have improved so much that the need has changed, but the “rule” hasn’t.  Newer oil (especially synthetic) simply doesn’t break down as quickly as before and the tighter tolerance’s of modern engine’s extend the life of both.  It’s also the reason 150k miles (200k for some auto manufactures) is the new 100k.  It use to be that you felt good if you got 100,000 miles, everything after that was gravy. Now every manufacture on the planet you can feel pretty comfortable getting 150 out of your car with relative ease.