# Mixing Tire Sizes?



## moonspinner (Jul 2, 2002)

Can you have two different tire sizes on a vehicle? I have 225 75 15 and 225 70 15.


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## farmrbrown (Jun 25, 2012)

Yes.
You _can_, front to back, not side to side. Not the best thing, but sometimes you have to do the next best thing instead of the best thing, lol.


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## moonspinner (Jul 2, 2002)

Sorry for misunderstanding, do you mean two same sizes on the same side or two same sizes on front and two same ones on rear? Will 4 wheel drive affect it? 
Also, if I do this will it jeopardize passing inspection? 
I have four excellent tires - just two different sizes.


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## nosqrls (Jun 9, 2012)

Do not do it on awd or 4wd. You can destroy a transfer case. 2wd 2 same size on front, 2 same size on the rear.


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## GREENCOUNTYPETE (Jul 25, 2006)

225/75 R15 is a very popular size for trailers right now , i blew one on my trailer about 3 weeks ago , couldn't find a used 15r tire anywhere right now one guy had 2 and he sold them before i could get there the next day every shop had the same story every where all cleaned out

I did end up buying 2 new trailer tires at 80 dollars each mounted , they wanted 40 for the used ones so 80 didn't sound so bad considering my last set uf used tires only made it 3 years the new set should hopefully last 10+ as long as i can stop fining fence posts the hard way

so if you do buy 2 new ones to match your best 2 sell your old ones for 30 each on Craig's list to help with the cost of new


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## moonspinner (Jul 2, 2002)

Still looking to find out if mismatched tires (in legal shape) will pass vehicle inspection. I've checked the regulations and they mention nothing about tire size, only tread wear and any obvious cracks/cuts/etc. I only want to put on the two different sizes temporarily until I can save up for a new matching pair. And yes, the 75s are very hard to find used.


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## Nimrod (Jun 8, 2010)

Both the tires you mention have a 225 mm width. One has a sidewall height that is 75% of the width while the other one had a sidewall height that is 70% of the width. One is slightly bigger in height and diameter than the other one. Be sure the one on the rear (of a rear wheel drive car) is the one specified or the speedometer will be off. The cop probably won't buy that excuse.

Otherwise, it will work as long as you don't have 4 wheel drive.

Come on, do you really think some minimum wage flunky at the inspection station will even notice that one tire is a different size??


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## moonspinner (Jul 2, 2002)

I do have 4 wheel drive and everything I've read indicates you should never mix sizes. I just didn't know whether the 70/75 difference could get me by. Guess I'm stuck getting two more 75s which are so hard to find used.


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## Sawmill Jim (Dec 5, 2008)

moonspinner said:


> I do have 4 wheel drive and everything I've read indicates you should never mix sizes. I just didn't know whether the 70/75 difference could get me by. Guess I'm stuck getting two more 75s which are so hard to find used.


Even running different brands and or any difference can put stress on a 4 wheel drive . I have all four same size and brand on a 4x4 I keep for winter driving . If you have the option of staying out of 4x4 mode all would be good then never engage the 4x4 on pavement or things will get interesting ,ask how I know :Bawling:


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## MichaelZ (May 21, 2013)

A friend of mine did that - and when in 4wd, his car would periodically buck and jerk. Then he matched tires and the problem went away.


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## moonspinner (Jul 2, 2002)

So if I stayed in 2wd mode (I have a Ranger) I'd be okay with putting 2 70s on? I wouldn't need 4 wheel obviously til winter and that would give me time to purchase two new 75s.
Okay Sawmill Jim, how do you know?


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## Micheal (Jan 28, 2009)

Living in NYS and over the years have had many cars, and trucks inspected. I've never had anyone question the tire size or even look for it. As you mentioned they do check for wear and checking but never looked for proper size!
Although they will not pass a car if'n one of those tires is one of those "emergency" type tires.


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## backwoodsman7 (Mar 22, 2007)

moonspinner said:


> So if I stayed in 2wd mode (I have a Ranger) I'd be okay with putting 2 70s on? I wouldn't need 4 wheel obviously til winter and that would give me time to purchase two new 75s.


Yes. You could still use 4wd if you get stuck, but disengage it as soon as the rear wheels have traction, and don't use it any other time unless at least one wheel is on something slick enough that it doesn't have much traction.


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## moonspinner (Jul 2, 2002)

Thanks so much everyone for the input. It's why I love this website.


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## Sawmill Jim (Dec 5, 2008)

moonspinner said:


> So if I stayed in 2wd mode (I have a Ranger) I'd be okay with putting 2 70s on? I wouldn't need 4 wheel obviously til winter and that would give me time to purchase two new 75s.
> Okay Sawmill Jim, how do you know?


Seen it done once on pavement .Any size difference the front will try to out run the rear or vice versa ,makes a interesting noise also won't let the four wheel drive disengage :sob: . As backwoodsman7 said if you are in mud you will never know it as the tires will be spinning which relieves the stress. 

While you are there just get four .:cowboy:


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## moonspinner (Jul 2, 2002)

Update:
I got the tires on and inspection at the same time. For all my worries the mechanic inspected nothing! Obviously when he took the old tires off he saw the brakes had just been done, but did nothing else -no checking lights, steering etc. All he did was a brief emissions hookup, stuck on a new sticker and I was good to go.


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## Pat32rf (May 5, 2014)

When the size difference is that close on a 4x4, you can often get by if you run the larger tires a little softer than the smaller ones. A lot depends on the road surface (slippery), speed, and type of driving. Running into town is different than a daily 60 mile commute...


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## backwoodsman7 (Mar 22, 2007)

Pat32rf said:


> When the size difference is that close on a 4x4, you can often get by if you run the larger tires a little softer than the smaller ones.


Do you mean, run them softer so they're closer to the height of the smaller tires? If so, then no, you can't get by with that. The rolling diameter of a tire is determined by the length of the tread around the circumference, which is determined by belts of steel or something else that stays exactly the same size regardless of inflation pressure. If you let out enough air to lower it a half inch, which is about the difference in radius between those two sizes, all you've done is create a whole lot of flexing in the tire, and make the slippage more likely to happen on the higher pressure tires, which will usually have less traction. Two tires still have to slip a little over 3%, or one tire has to slip over 6% (given those two sizes), or something is going to break.


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## moonspinner (Jul 2, 2002)

I've been driving the mismatched tires for three months now and no issues.


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## GoldenCityMuse (Apr 15, 2009)

Good update.

A part time 4WD vehicle like your Ranger should never be driven w/ the 4WD engaged on hard, dry pavement anyway. But if you are on snowpacked ,icy roads, you will be fine.


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## moonspinner (Jul 2, 2002)

That is interesting. I had never heard this before.


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## moonspinner (Jul 2, 2002)

I was talking to a couple guys who know and work on vehicles and they told me I would be ok locking in 4WD on unmatched tires only on slippery surfaces for a brief distance and driving very slowly.
BTW, how would you know if you damaged the transfer case and how would it affect driving?


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## nosqrls (Jun 9, 2012)

It depends on what part breaks. Case big puddle of oil on the ground and truck won't move. it is toast. chain you lose 4wd or locks up and breaks case. input shaft shears truck don't move. gears break, locks up, case breaks get's real ugly.


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