What tire size?

Chillbilly · 10-04-2011, 10:57 AM

I want to move from a P classification to an LT tire for the stronger sidewalls. I'm pulling a Flagstaff 829FKSS with a 2010 Ford F150 Supercab. It has the 255 rear end. Was wondering what tire size you all are using. I've considered the LT265/70/R17 but have been told I should stay with the LT245s. Any input will be greatly appreciated.

fajitas21 · 10-04-2011, 11:23 AM

What's OEM spec for your truck?

Keep in mind going too much larger than OEM spec will raise the truck higher into the air, and also might cause fender rub when locking the wheel from side to side.

Tires are a complicated mess of a subject, especially what PSI to run them at. I'm not really super familiar so I'll just start off this conversation and then back out to let the pros have at it.

Chillbilly · 10-04-2011, 12:18 PM

The truck came with P235/70/R17 tires, so I know the correct P series size. I just don't know which LT tires to use. I want the LT series for the stronger sidewalls. Maybe I should go with LT235s, but some have suggested I go with a larger tire, such as a LT245 or LT265. I thought maybe someone had already gone through this exercise.

TURBS · 10-04-2011, 12:39 PM

I would call your tire dealer and ask them for the correct conversion from p to lt . It would be in your best interest since it is there fortay .

Dave_Monica · 10-04-2011, 12:54 PM

Quote:

Originally Posted by Chillbilly

The truck came with P235/70/R17 tires, so I know the correct P series size. I just don't know which LT tires to use. I want the LT series for the stronger sidewalls. Maybe I should go with LT235s, but some have suggested I go with a larger tire, such as a LT245 or LT265. I thought maybe someone had already gone through this exercise.

What you want is 17" LT tires that have the same circumferences as your P metric tires otherwise your changing the rear end ratio and creating a speedometer error.

As you're towing you DO NOT want to increase the tire diameter/circumference as it will have the same effect as lowering (numerically) your rear end ratio. This would make acceleration and hill climbing worse.

Dave

MtnGuy · 10-04-2011, 01:30 PM

Chillbilly, keep us posted with what you find out. I want to do the same with my F150 when the time comes.

acadianbob · 10-05-2011, 09:43 AM

Quote:

Originally Posted by Chillbilly

The truck came with P235/70/R17 tires, so I know the correct P series size. I just don't know which LT tires to use. I want the LT series for the stronger sidewalls. Maybe I should go with LT235s, but some have suggested I go with a larger tire, such as a LT245 or LT265. I thought maybe someone had already gone through this exercise.

I agree with Dave entirely. What is the goal that you are trying to accomplish? A wider tire will not increase the towing capacity of your truck. And there are negatives. As Dave pointed out, you do not want to increase the circumference of your tire. It affects towing capacity, odometer, speedometer, handling characteristics; rolling friction, directional tracking on uneven surfaces, more pressure on steering components, . . . . So, you would need to go to a lower profile tire (eg 70 to 60) to compensate for a wider tire cross section. (70% of 235 is about the same sidewall height as 60% of 265)

Many people think that Bigger is Better whether it is tires, WD bars, springs, etc. That is often (perhaps mostly) not true. I would stick with the stock size tire. If you do go wider (eg. 235 to 265) you definitely need to go lower profile. But I think you might be disappointed.

By the way, I've changed cross section and aspect ratio for winter tires, racing, etc so I have quite a bit of first hand experience with this subject. Sometimes I've gone wider for racing and sometimes narrower for winter traction. Always, always I stick to the same overall diameter. IMO you should proceed cautiously and be aware of the ramifications of your choices. Good Luck!

acadianbob · 10-05-2011, 10:32 PM

P.S. Going from P to LT in the same size tire shouldn't be an issue. LT load range C (50 psi) is probably plenty though. Ford F150 LT factory tires are Range C. Many tire dealers do not recommend Range E (80 psi) for 1/2 ton trucks. A major tire dealer here in MN refused to put Range E on my 1/2 ton truck. I know that some people swear that is the way to go though.

donn · 10-05-2011, 11:00 PM

Go to the OEM tire manufacturers web site and do some research. Look for the overall diameter of the tires you have. Now go to the manufacturers web site for the new tires you are considering and find a LT tire that has the same or nearly same diameter. that is the size you want to buy.

acadianbob · 10-06-2011, 05:29 AM

Donn said it in a sentence. Go to tirerack.com and look at your OEM tire and then the tires in which you are interested. Go to the specifications tab. It will tell you diameter, revs/mile, etc. As Donn says, this is what you want to match. Or if you PM me with your email, I could also send you an Excel spreadsheet that calculates diameter. You enter cross section size, aspect ratio, and rim size. then it calculates for you. It is an easy way to compare tires.

SaskCampers · 10-06-2011, 07:43 AM

Quote:

Originally Posted by acadianbob

P.S. Going from P to LT in the same size tire shouldn't be an issue. LT load range C (50 psi) is probably plenty though. Ford F150 LT factory tires are Range C. Many tire dealers do not recommend Range E (80 psi) for 1/2 ton trucks. A major tire dealer here in MN refused to put Range E on my 1/2 ton truck. I know that some people swear that is the way to go though.

People in farm country put LR E tires on for the 10 ply rating when out in the fields to prevent flats on 1/2 tons not for the load carrying. I ran them on our 04 Ram 1500 at 40psi and they were fine as many farmers do. As to the OP's question, I would check with his Ford dealer as to what was the stock size LT tire option for his truck and put that size on. Also on tireracks site as was mentioned it will show what was the oem LT tire size.

245/75-17
Load Range E was oem tire size for the heavy duty F150 according to tire rack.

acadianbob · 10-06-2011, 03:59 PM

Quote:

Originally Posted by TheSasks

People in farm country put LR E tires on for the 10 ply rating when out in the fields to prevent flats on 1/2 tons not for the load carrying. I ran them on our 04 Ram 1500 at 40psi and they were fine as many farmers do.

Yes, more resistant to sidewall issues. The tire dealer here refused to put an 80 psi tire on my factory wheels. Running less PSI probably OK but then you wouldn't get the full capacity of the tire. The current 2012 ordering guide for F150 shows an LT option but it is Load Range C; 50 psi. I have the dealer document. You could put on a LR E and run 50psi I would think. Well, these discussions are endless as we all know . . .

**Herk7769** · 10-06-2011, 04:21 PM

There are MANY threads here about tires.

Just make sure if you "up" the load range that your rims can take the increased pressure. Somewhere on the rim (not the tire) the max PSI of the rim is stamped in the metal.

acadianbob · 10-07-2011, 12:50 PM

Quote:

Originally Posted by herk7769

There are MANY threads here about tires.

Just make sure if you "up" the load range that your rims can take the increased pressure. Somewhere on the rim (not the tire) the max PSI of the rim is stamped in the metal.

Yep, that's why the tire dealer wouldn't put LR E's on my F150.

smithmdsmith · 10-07-2011, 01:39 PM

Unless you want a bigger tire for looks, stick with the stock size. Even a slightly larger diameter tire can have a noticible effect on towing.

I went from a C load tire to an E load tire on my Titan for the stiffer sidewall. Towing is much more stable. I do not know the pressure my wheels are rated for. I will look into that tonight. I run 44 psi when the truck is empty and 55 when the truck is loaded or towing.

boubou · 10-07-2011, 08:51 PM

Quote:

Originally Posted by smithmdsmith

Unless you want a bigger tire for looks, stick with the stock size. Even a slightly larger diameter tire can have a noticible effect on towing.

I went from a C load tire to an E load tire on my Titan for the stiffer sidewall. Towing is much more stable. I do not know the pressure my wheels are rated for. I will look into that tonight. I run 44 psi when the truck is empty and 55 when the truck is loaded or towing.

I will be getting new tires next spring (upgrade from hP tires). How do you mean towimg is much more stable? What improvment do you feel?

**wmtire** · 10-08-2011, 09:37 AM

Quote:

Originally Posted by herk7769

There are MANY threads here about tires.

Just make sure if you "up" the load range that your rims can take the increased pressure. Somewhere on the rim (not the tire) the max PSI of the rim is stamped in the metal.

And it hasn't been mentioned, if the vehicles/wheels have TPMS (Tire Pressure Monitoring Systems) installed.......which are set for a specific tire p.s.i.

And on another note, excluding some TPMS systems, tires that run over 60-65 psi, need what is called a high pressure valve stem installed to safely run the 80 psi of a Load range E tire.

A lot of people don't know, that the regular ole, black rubber valve stem that everyone is used to seeing in their vehicle or camper wheels.....is rated for 60-65 psi max.

**Herk7769** · 10-08-2011, 10:48 AM

About stems, if you do used a TPMS that involves a replacement cap on the stem, DO NOT use a rubber stem even if it is rated for 100PSI.

Centrifugal force will bend the stem over until the TPMS monitor contacts the rim. This will eventually cause a stem leak. Get the stiffer all metal or metal shank ones. They are worth the special order at most tire places.

boubou · 10-08-2011, 08:35 PM

Wow! So much to think about just for changing tires. Glad I joined this site, you guys and gals are most helpful.

smithmdsmith · 10-10-2011, 08:46 PM

Quote:

Originally Posted by boubou

I will be getting new tires next spring (upgrade from hP tires). How do you mean towimg is much more stable? What improvment do you feel?

With the original tires, the truck would feel like it was squirming when I would hit uneven pavement or other less than perfect driving situations. With the heavier duty tires, the truck feels much more sure-footed.

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