Tire size question?

Tiny
KATVERNON
  • MEMBER
  • 2006 TOYOTA CAMRY SOLARA
  • 2WD
  • AUTOMATIC
  • 144,408 MILES
Hello! This is an extremely long story of how I got to this point but I will just get to the gist of it - I got a flat tire on my front left (drivers side) tire. The tire was completely damaged (at my fault for driving on it with low tire pressure) so I needed to get a new tire. The rest of my tires have good tread and were replaced 1-1.5 years ago, and I don’t do that much driving so they are in good condition. My current tires are 215 55 R17. I ended up with a 215 50 R17 tire to replace my flat tire. I took it into pep boys and asked if it would be a bad idea to have that tire installed, since the other three are 55s and this one is 50. They explained to me in detail (with pictures drawn!) Why this would be okay, that it was barely a difference and there was no need to worry, this tire is okay to have on my car. Three different mechanics agreed with him, saying the slightly smaller tire was fine. I am wondering what you think? My boyfriend claims they were trying to take advantage of me but I don’t see any reason why they would do that, it’s not like they made more money by installing this tire for me, is it was purchased separately, at a different establishment. What do you think? Is it okay to have one tire sized 215 55 R17 and three others 215 50 R17? Thank you so much in advance!
Thursday, December 29th, 2022 AT 10:25 AM

3 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,119 POSTS
Hi,

Interestingly, the 55 series tire is nearly an inch taller than the 50 series tire. That doesn't sound like much, but it does make a difference.

If you look below, I attached a pic. Whenever I have questions about tire sizes and want to compare them, I go to tiresize. Com. That is where the pic is from. We are not affiliated with them, but they do a great job, and I want them to get the recognition they deserve.

The replacement tire is nearly an inch smaller in outside diameter. What that does is make the new tire turn faster than the original tire. Over the course of a mile, the new tire size will spin 767 revolutions and the original size will spin 792 revolutions. Can that affect the vehicle?

Here is what can happen: If these are on the front, it is adding additional stress on the transmission because one side is always turning faster than the other. Yes, the transaxle is designed to handle different speeds when turning, but not when driving in a straight line for extended periods of time.

Additionally, when you have two different tire sizes, regardless of the amount of variation, it will always have an adverse effect on vehicle handling.

If they would have installed that tire on the rear of the vehicle, I wouldn't be as concerned about mechanical damage, but again the handling would be affected. However, since it is on the front, personally, I wouldn't want it there. I would move it to the rear and find the correct size tire.

I'm sorry. I wish I had a better answer, but those are the facts. After nearly 40 years of working on cars, this is what I would have told you when you got the tire. In an emergency, it would work, but shouldn't be used long-term.

I hope this helps. Let me know if you have other questions.

Take care,

Joe

See pic below.
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Thursday, December 29th, 2022 AT 10:49 PM
Tiny
KATVERNON
  • MEMBER
  • 2 POSTS
Hi Joe, thank you so much for your response and your input! I really appreciate it. The tire size visual was extremely helpful and it all makes more sense to me now. I see that I definitely need to get a new tire, the correct size. Thank you so much!
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Friday, December 30th, 2022 AT 3:06 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,119 POSTS
Hi,

You are very welcome. I'm glad it helped. The tire size site I sent you to is helpful. I've used it several times myself.

Regardless, I hope you have a great new year, and feel free to come back anytime in the future. You are always welcome here.

Take care,

Joe
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Friday, December 30th, 2022 AT 10:07 PM

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