Mis-matched spare?

[FatTiresRollin]

Found a couple threads on Tacoma world and some other places, but wanted to get the opinion of my trusted 5th Gen crowd. I am upsizing to 285/70/17 as soon as I make up my mind on which tires to buy. I am leaning hard toward Duratracs if I don't have to put out the cash for a full size spare. What is your opinion about running the stock 265 spare (not permanently of course) with something like a 285 Duratrac?

Also, maybe a 285 spare, but just a REALLY cheap...possibly almost bald used tire I find on Craig's List or Ebay?

As always, thanks for the input!

 

[cbielat]

I've read on here that a 285 will fit in the stock spare location. I've also been told that it wouldn't be a good idea to run a 265 as a spare while running 285's. I question this as well and will follow your post.

 

[cbreze]

This is my current set up. I thought rim size was more critical than width of tire. Look at the donut spares on cars today.
FWIW, I asked my dealer this question as they put the duratracs and new wheels on for me and that was what they said. I'll be following this thread also for some expert comments.
EDIT: is the concern having the duratrac fit in the spare space? Maybe I misunderstand after rereading above post.

 

[Okki]

I replaced all my rims/tires to be the same size. Any difference greater than a worn vs a new tire is a concern. A larger tire might drag while a smaller tire might skip trying to catch up the to the tires with the larger circumference. In all cases you are putting undue stress on the axle, diff and possibly drive-line.

I would change everything out. JM2C

Okki

Edit: it's the outer diameter comparison between all wheels; i.e. the outer diameter of the tires needs to be as identical as possible. The rim size plays no role aside from a weight standpoint. I'll gladly be corrected, but I believe a donuts is a narrower tire; not a smaller diameter compared to the other drive wheels.

 

[4Run4YourLife]

Look at the donut spares on cars today.

Bingo. As long as it is just temporary, there won't be any devastating results.

 

[4Run4YourLife]

Bingo. As long as it is just temporary, there won't be any devastating results.

Additionally, why would someone want to waste the cash to wrap an ugly yellow spare rim with a new tire? (I am assuming the SR5 spare is yellow like the Limited) It will never stay on my 4runner for more that a few miles anyways. I still don't know why Toyota did that on the 5th Gen.

 

[FatTiresRollin]

I am not concerned about it fitting in the stock location as several members have posted that this is not an issue. Just wondering that if in an emergency situation, would it be ok to possibly drive a couple hours if needed on the mismatched size spare. I am not talking about blowing a tire while rock crawling...just driving on road trips. I am going to Hilton Head, SC in June and just want to make sure I have a safe set-up. I had the same thoughts about the donut spares...which is why I initially thought it would be fine. That being said....found this add on CL today 285/70/17 Duratracs Goodyear 33s Jeep Price Reduced . Thoughts on buying used tires? I have no experience with used tires...what would a fair price be?

 

[Intruder]

A 285 Duratrac spare fits with a little wiggling, but you don't have to force it in there. If you're getting 285 Duratracs just for looks then an emergency spare to get you to a service station or tire shop might be ok. If you're going off road and shred a tire in the middle of a challenging trail you'll regret having a bald or mismatched spare.

 

[1engineer]

Found a couple threads on Tacoma world and some other places, but wanted to get the opinion of my trusted 5th Gen crowd. I am upsizing to 285/70/17 as soon as I make up my mind on which tires to buy. I am leaning hard toward Duratracs if I don't have to put out the cash for a full size spare. What is your opinion about running the stock 265 spare (not permanently of course) with something like a 285 Duratrac?

Also, maybe a 285 spare, but just a REALLY cheap...possibly almost bald used tire I find on Craig's List or Ebay?

As always, thanks for the input!

There are several reasons not to run a mismatched spare and I will get into that in a bit. First, a little math: A 265/70/17 generic tire has a diameter of 31.6" and a 285/70/17 has a diameter of 32.7", which equates to 1.1" difference, or a little over 1/2 inch radius difference. The circumference difference is of course greater, being 99.73" and 102.8" respectively. The difference of 3.5" means one tire rolls 3.5" farther every rotation. I won't bore you with the math but the 265 tire will try to travel over six feet farther every mile. Why does this matter? Here's why:

What do anti lock brakes, vehicle stability control, transmission, down hill ascent, transfer case and front and rear differentials and other systems all have in common? Answer: They all use tire rotation speed either electronically or mechanically in order to do their job!
The 4Runner uses tire rotational speed to determine if the vehicle is operating at normal performance. Let's say you are pulling out onto a busy highway and there is fine gravel underneath the rear wheels. You step on the accelerator pedal, you start to spin and you hear a "chatter." That is the vehicle sensing wheel slip on one tire or the other and braking the spinning one to keep it's rpm the same as the one with traction. Same for all the other systems.
Now, what happens when you throw a tire on that will automatically, because of it's decreased radius, be turning at a different rpm? The answer is the truck will try to compensate for the spin by activating whatever electronics that are needed. Now this is in two wheel drive. In four wheel drive, you will have one tire turning faster than the others which will very shortly start to bind up the driveline. Your tire will of course spin but it will put undue stress on the differentials and transfer case. Even if you decide all this is still OK, do you want to go into an unexpected skid around a turn and let VSC be confused on what to do because of you saving a few bucks? No, me either.
Now, while I don't know what tolerances Toyota engineers put into their algorithms for speed sensors, I do know they are there. It is common for a tire to have more wear than others, such as having a flat on tires that have 50K miles and putting a spare with no miles and new tread. Also going around a sharp corner the front and outside tires travel a farther distance than the rear and inner tires. For this reason Toyota has built in rpm tolerances to allow for each of these conditions. Now, if you put a new 265 with a completely worn out 285 you maybe could be OK. What are the chances of that though? Your choice and I hope this helps.

 

[1engineer]

Bingo. As long as it is just temporary, there won't be any devastating results.

Please read my above post and justify your statement as quoted. Otherwise, make sure you know what you are talking about before giving out advice.

 

[FatTiresRollin]

I should have known 1Engineer would chime in with some calculations. I actually like the math...and have done the math (BS in Aerospace Engineering), just not sure of the real worl effect it has. I have read that if the mismatched spare is to be used, that it should be put on the front (for a rear wheel drive truck). So everything 1Engineer is saying definitely makes sense. I am only talking about enough time to get to a service station that can fix me up or where I can buy a new tire if needed. I also carry roadside assistance on my insurance for a real extreme case. Just out of pure common sense I will most like get a 285 spare, just maybe not a Duratrac. Hypothetical references and physics calculations are gladly accepted, but If anyone has any real world experience with the situation I would love to hear from you.

 

[1engineer]

I should have known 1Engineer would chime in with some calculations. I actually like the math...and have done the math (BS in Aerospace Engineering), just not sure of the real worl effect it has. I have read that if the mismatched spare is to be used, that it should be put on the front (for a rear wheel drive truck). So everything 1Engineer is saying definitely makes sense. I am only talking about enough time to get to a service station that can fix me up or where I can buy a new tire if needed. I also carry roadside assistance on my insurance for a real extreme case. Just out of pure common sense I will most like get a 285 spare, just maybe not a Duratrac. Hypothetical references and physics calculations are gladly accepted, but If anyone has any real world experience with the situation I would love to hear from you.

Mr. Murphy states that if you use a 265 spare you will have a flat at 2:00am on Sunday morning on a deserted strip of interstate with nothing open and have to drive for hours on that 265 spare. You know the drill. Every engineer does.

 

[GrantK]

Mr. Murphy states that if you use a 265 spare you will have a flat at 2:00am on Sunday morning on a deserted strip of interstate with nothing open and have to drive for hours on that 265 spare. You know the drill. Every engineer does.

You will also have to use the spare in 4wd where mismatched size puts extra stress on parts, even with wheel slip.

 

[cbielat]

Thanks 1E. That's what I was figuring as well.

 

[4Run4YourLife]

Please read my above post and justify your statement as quoted. Otherwise, make sure you know what you are talking about before giving out advice.

First of all, I don't disagree with anything you posted. Second of all, I am not incorrect. As a fellow engineer, I appreciate your overly analytical responses, but sometimes a simple answer will suffice. Treating the original full-size spare similar to a temporary donut is acceptable. The fact that he has an SR5 (no full time 4wd) only strengthens that opinion.

Using the original spare TEMPORARILY in his situation will not have devastating results. I never claimed it as ideal, nor did I advise using it in any manner other than as a temporary solution.

Spares tires do not always have equivalent diameters to the full-size tire. These smaller diameter spares have speed and distance ratings because the do in fact put strain on the vehicle differential and drivetrain. If driven at high speeds or long distances, then damage can and will occur. My response did not suggest otherwise.

 

[4ShoreRunner]

For what its worth I found a used 285 to run as my spare....price of tire+mounting+balancing was a total of $50. I would just find a used 285 and call it a day.

 

[FatTiresRollin]

For what its worth I found a used 285 to run as my spare....price of tire+mounting+balancing was a total of $50. I would just find a used 285 and call it a day.

My thoughts exactly. I actually found a used Nitto Terra Grappler for $20 on my local CL.

Now I just need to land myself a deal on some Duratracs!

 

[eddiebx]

First of all, I don't disagree with anything you posted. Second of all, I am not incorrect. As a fellow engineer, I appreciate your overly analytical responses, but sometimes a simple answer will suffice. Treating the original full-size spare similar to a temporary donut is acceptable. The fact that he has an SR5 (no full time 4wd) only strengthens that opinion.

Using the original spare TEMPORARILY in his situation will not have devastating results. I never claimed it as ideal, nor did I advise using it in any manner other than as a temporary solution.

Spares tires do not always have equivalent diameters to the full-size tire. These smaller diameter spares have speed and distance ratings because the do in fact put strain on the vehicle differential and drivetrain. If driven at high speeds or long distances, then damage can and will occur. My response did not suggest otherwise.

I get where you are coming from but when you step back and look at this situation, would you rather hear, "yeah it's fine"/"no it's not", or an actual reason as to why one advises one way or the other?

Everyone's idea of temporary is different, just telling a guy "yeah run on it temporarily,you'll be fine" without explaining to him the repercussions could lead to no good in a hurry. Besides, when it comes to using a spare tire, we don't exactly get to pick and choose where and when we want to blowout a tire and need a spare, ie. someone can be a long distance away from the next tire shop and on a higher speed interstate, then what is one to do while driving on a smaller spare tire? Considering that even you have admitted, you shouldn't drive long distances, nor at high speeds.

Another thing you have to consider is, while yes not all manufacturers/cars come with a full sized spare, Toyota decided that our 4runner needs a full sized spare; and I'd like to think they probably have a reasoning behind it other than convenience for the end user. So just because there are other cars out there with donuts as spares does not automatically mean it's a great idea for our 4runners as well.

 

[4Run4YourLife]

I get where you are coming from but when you step back and look at this situation, would you rather hear, "yeah it's fine"/"no it's not", or an actual reason as to why one advises one way or the other?

Everyone's idea of temporary is different, just telling a guy "yeah run on it temporarily,you'll be fine" without explaining to him the repercussions could lead to no good in a hurry. Besides, when it comes to using a spare tire, we don't exactly get to pick and choose where and when we want to blowout a tire and need a spare, ie. someone can be a long distance away from the next tire shop and on a higher speed interstate, then what is one to do while driving on a smaller spare tire? Considering that even you have admitted, you shouldn't drive long distances, nor at high speeds.

Another thing you have to consider is, while yes not all manufacturers/cars come with a full sized spare, Toyota decided that our 4runner needs a full sized spare; and I'd like to think they probably have a reasoning behind it other than convenience for the end user. So just because there are other cars out there with donuts as spares does not automatically mean it's a great idea for our 4runners as well.

Boy oh boy. I didn't just say "Yeah, it's fine". I said "As long as it is just temporary, there won't be any devastating results." Am I wrong?

I mentioned temporary use after quoting a comment about a donut. I will admit that I assumed a certain level of common sense from the OP. I didn't think it was necessary to explain the limitations of a donut spare.

Toyota uses donuts for a number of vehicles. Having a full-size spare is obviously ideal and is considered a premium. I can assure you that the price for that full-size spare is well compesated for by the consumer. I didn't in any way insinuate that using a donut or mismatched tire (minimal in the op's case) as a great idea.

Again, it is fine in a temporary (less than 50 miles, under 50mph) type of situation (on surface streets, not rock crawling). Just ask Toyota.hwell:

 

[NorthWest 4R]

When I was concerned about this same question when I bought my AWD Limited 4R and went aftermarket wheels/tires.

From the information I have gathered (independently) as well as talking to a Toyota technician, the consensus is the 4R's Torsen center diff and computer has a tolerance of 3% of tire difference from front to rear.


You have an SR5, so this is even less critical as you are not 4wd all of the time.