Truck tire question re replacing

[John Fitzgerald]

That is the same thing I am being told re that size. I could certainly live with the size but have some concern finding a replacement if have a blow out somewhere far from home - I want to be able to buy a tire that matches. I found the 245/70/R17 tires in the Michelin Defender so may order those. I don't have a 4x4, and I don't think I would have major issues if my spare would remain a 235/75/R17 as it would be only a temporary use.

As I said: The 245/70/R17 is very close in diameter to the originals. I was thinking of getting a matching rim for the spare and rotate that one in every 6k miles or so, but the Tire Pressure Monitoring System makes that impractical. Even if a sensor was in the spare, the system can only remember 4 tires, so every rotation would require a trip to an authorized dealer, or the TPMS light would be on, and the vehicle performance might possibly be reduced by the TPMS.

 

[Egon]

I'm of the impression the narrow tire's give better service and are easier on the front suspension - steering components. No data to support these thoughs other than seeing wide tires in mud or snow.

 

[Rock Crawler]

235-75-17s =

235mm divided by 25.4mm in an inch = 9.25" wide
75% aspect ratio, or the tire is 75% as high from bead to tread as it is wide. It is 9.25" wide.
9.25" wide times 0.75 aspect ratio is 6.94" bead to tread.
You have bead to tread 2 times, ground to wheel and then again top of wheel to top of tire... so 6.94" times 2, then add the rim bead diameter to get overall height.
6.94"+6.94"+17" = 30.88" tall
So it is a 30.88"x9.25"-17".

Now rinse and repeat for any metric size that you want to convert to inches... a dimension we Americans can understand!

Stock tire 30.88"x9.25"-17

235-70-17s is 29.95"x9.25"-17

245-75-17s is 31.47"x9.65"-17"

245-70-17s is 30.5"x9.65"-17" (Closest to factory)

 

[John Fitzgerald]

I am getting another OEM rim with TPMS monitor and go with 5 tire rotations on my F150 4x4. Probably get five AT 265/70/R17's. If the TPMS lights up, that's ok. We didn't have it with our last truck. I check my pressure often anyway, and can easily adjust at home.

 

[scdeerslayer]

As I said: The 245/70/R17 is very close in diameter to the originals. I was thinking of getting a matching rim for the spare and rotate that one in every 6k miles or so, but the Tire Pressure Monitoring System makes that impractical. Even if a sensor was in the spare, the system can only remember 4 tires, so every rotation would require a trip to an authorized dealer, or the TPMS light would be on, and the vehicle performance might possibly be reduced by the TPMS.

You can get a TPMS reset tool for not very much money, and any place that sells and/or rotates tires should also be able to reset them, so if you get other service done you could rotate your tires before going there and ask them to reset them for you. Not sure what kind of truck you're talking about but on mine you can reset them without the tool by adding or letting out air for so many seconds when you're in the reset mode, but I think they did away with that feature after the first few years.

I don't know how old your TPMS sensors are, but you may want to replace them when getting new tires, they only seem to last 8 or 9 years.

 

[John Fitzgerald]

You can get a TPMS reset tool for not very much money, and any place that sells and/or rotates tires should also be able to reset them, so if you get other service done you could rotate your tires before going there and ask them to reset them for you. Not sure what kind of truck you're talking about but on mine you can reset them without the tool by adding or letting out air for so many seconds when you're in the reset mode, but I think they did away with that feature after the first few years.

I don't know how old your TPMS sensors are, but you may want to replace them when getting new tires, they only seem to last 8 or 9 years.

2010 F150 4x4 extended cab 4.6 V8. I wish it didn't have TPMS. To me, it's a nuisance, because I check my tires often anyway, and have compressed air at home.

 

[IvanS]

John Fitzgerald: Why do you want to have 5 tires to deal with? Are you of the mindset that it will add to the total mileage you get from the tires? If you rotate every 5k and maintain alignment and appropriate air pressure you will get the maximum life out of the tires and they should all (4) be due for replacement at the same time. You need to do the math on this, but I think it's economically a disadvantage to have a 5 tire setup. Not to mention the hassle of retrieving and stowing a wheel/tire from the spare location at every rotation.

Also, unless the tire size difference is significant, driving with a spare of a different size for a limited time won't damage the drive train. A spare tires only mission in life is to get you to a tire shop to repair/replace the damaged tire, not to permanently replace the road tire. I run much larger tires than my spare, if I have a flat I'll call someone for assistance. No more often than I've had tire failures (knock on wood) I'm money ahead by not purchasing the 5th tire for a spare. The tires on my truck are $250 each, by not spending that money on a spare, I feel like that's my repair budget.

Increasing tire size can effect performance and mileage, it will impact the speedometer / odometer. Today there are aftermarket interfaces that you can install to calibrate the speed/odometer readings to be correct.

By the way, if the need arises to compare tire sizes, you can use this nice calculator at: Tire Size Calculator - Tire & Wheel Plus Sizing

 

[robertsa]

I'm of the impression the narrow tire's give better service and are easier on the front suspension - steering components. No data to support these thoughs other than seeing wide tires in mud or snow.

The width doesn't have any effect on front end parts unless you're talking about the doofuses that mess with the backspacing to make their wheels stick out past the fenders because they think it looks cool.

An advantage to a narrow tire is use in ice and snow; it places the weight of the vehicle on a smaller patch of land, making it bite.

 

[robertsa]

2010 F150 4x4 extended cab 4.6 V8. I wish it didn't have TPMS. To me, it's a nuisance, because I check my tires often anyway, and have compressed air at home.

TPMS is nice when you pick up a nail on a trip, causing a slow leak. You'll get the dash light that you've got a low tire before you start feeling the effects. On a slow leak, it can buy you enough time to get yourself somewhere safe.

If you get a different size tire that's close to the same diameter, don't bother with replacing your factory spare. The width doesn't matter.

 

[John Fitzgerald]

John Fitzgerald: Why do you want to have 5 tires to deal with?

I think it would be advantageous for the spare to always match perfectly, and be fairly new. I built a tool to allow me to get the spare down and up very quickly. It is carried in the truck tool box along with a real lug wrench and jack. Gravel roads around here occasionally have flint rocks, from creek gravel still used by some entities, which are like knives when broken. If I only buy four tires, at my next tire change, the spare would be about fourteen years old. I don't put a lot of miles on per year, maybe 5-6k. I don't need to buy high mileage tires, 50k tires would be plenty.