I know you are all going to hate me for asking these questions, but as I said in my last thread, I am a complete newby to the world of trucks, coming from the U.K. and all! I have read through all 11 pages of posts and my head is now spinning! My first question is related to tire size, at the mo, I am running 245/75-16, I have a 2003, 7700, 5.4, XLT ext cab, 2x4 (I think I read somewhere the fact it is a 7700 can make a bit of difference? As I said my head is spinning!) I will be looking to get some new rubber in the next few months, and I am wanting to improve the look of my truck, is the largest tire I can fit on there with no mods (not enough $$$ for that at the mo :-( ) a 275/75-16? and what difference would it make to the look? and what difference would it make to the ride? I understand that if you go a little bigger then the MPG suffers a little. I am looking to get A/T's or similar (after all it is only a 4x2, so my off road capabilities are limited!) I also gather that BFG seem to be a popular tire too.

My second question is realted to PSI, at the mo, I have the front running at 45 and the rear at 60, this what was stated indside the fuel door (I am now under the impression that this is for max load really?) if that is the case what should I have in there really? what is safe, the best on MPG, tire wear and ride comfort? 90% of my driving (at the moment!) is road driving with only 1 (70% of the time)-3 passengers, and maybe some shopping! sorry if these all seem really dumb, second grade type questions but as I said I am soooo new to all this!
As always, thankyou in advance for any assistance!
Appreciate the help!
Rik

 

If you've got no load on the rear, your rears should be at less PSI than your fronts. Let me just ask you to think about the stresses on the front vs. rear on a non-loaded truck, then consider if your current set-up makes any sense..

Fill the rears to 55 or 60 psi if you do end up with a 1/2 to 3/4 ton load back there - when done, let some out. Otherwise, you've got your handling AND tire wear all kinds of screwed up.

 

Before doing anything with air pressure check the sidewall of your tire. The sticker on your truck was intended for the factory tire. A different tire brand or different style of tire will require different air pressure. Always keep in mind the max psi for a tire according to the tire's sidewall. If the tire says its max is 35. That is the max. If your truck sits all day with out you driving it and its not in the sun all day and you fill your tires up to 35 at 11 o'clock at night. Your tire is gonna have 40+ psi in it when the sun shines on it for a few hours and you drive down the interstate at 70mph for 20 minutes and you excede your max psi by 5 or more pounds, and this is very dangerous. My 4x4 f-150 calls for 28 psi in the front and 32 in the rear. This is designed for comfort and the factory tires were very soft A/T. There are current Michellin LTX/MS on the truck and these tires would be destroyed after 10k miles if I tried to run them like that.

 

I would just like to talk about the experience I have had. My 4x4 F-150 now has over 157k miles on it. I am on my second set of 295.75.16's. I keep 65psi in both front and back tires. Which is max tire pressure for these tires. I would agree that in the summer you will gain up to 4psi in the tires if you run in hot wx at high speed. I got 65k miles out of my first set and my son put another 10k on them. I attribute that to tire pressure alone. On this set I have over 50k already without a hint of tire wear. I know for me max is right...

 

Thats awesome that you are getting great mileage out of those tires by running them at their max. But the facts are still the facts. The max pressure is the max pressure and if you max the tires out when they are cold and run 20 miles down the interstate the pressure increases dramatically. And even 1 psi over the max could result in a tire failure.

 

That might be true, however I have not found that to be so... I have put over 100k on these tires. I don't think the pressures increase as much. I listen to NASCAR and they talk about increasing 3 to 4 PSI. When you are running 65PSI 4 PSI is not that much. But like I say, that has been my experience, I do not want to tell anyone to do what I do... lol

 

According to Michelin......

[quote]
Our recommendation is to always check the air pressure of your tires when
they are cold. In addition, you should inflate the tires to the door
placard specification even if this means inflating the tires to their
maximum. As long as the tires are not inflated over the max on the sidewall
when they are cold, it will be safe. [end quote]

So even if you inflate them to the maximum pressure stated on the sidewall they will still be safe after they have heated up and the pressure is above what it's supposed to be. A few of the fleets whose trucks I work on specify that they want all their tires inflated to the max on the sidewall. It's a bit scary pumping them up to 110 psi but that's what they want and they don't have problems because of it.

 

Thanks Dave, I thought I was doing right but the other folks put a smidge of doubt into my teny tiny little head... lol

 

[QUOTE=Racerguy]According to Michelin......

No, this is wrong.

The data supplied on the door is for the specific tires that were sold with the vehicle when new.

A tire manufacturer knows what they're designing - truck tire, car tire, load-bearing tire, trailer tire, etc. They also know - and state - the rim widths appropriate for each size of tire they sell, as well as the load capacity.

The range you will use IS the range on the sidewall of the tires. If the tires are made for a higher range, then so be it - but as with all tires, only pump to max pressure for max load. Adjust accordingly if lower than max load (well, you don't have to, but you'll often get premature wear in the middle of your tread). Accordingly, if the capacity is lower than what your truck was designed for, you can't carry as much of a load.

My god, what else will the nit-wits come up with - that we have to use SG (or whichever level was the commonly available level) rated oil in our crankcases just because that was the oil recommended at the time of manufacture, and is the grade of oil listed in our owner's manuals?

It' simple: you change the truck - or any vehicle - past the way it came stock, you become the person responsible for adjusting whatever it is that the new parts affect.

 

I guess Michelin figured that the tires being put on the vehicle were the correct ones when they wrote that.

 

Some Fords come with Michelins - but only certain models of their tires.

But no Fords come with Mickey Thompsons, for example (to use an extreme case), which have completely different characteristics, and thus can't be expected to hold the the original specs of the original tires for the new ones.

They could have assumed it, though, as many people go in to tire dealerships and ask for direct replacements, if not exact models, of the tires that came on their vehicle. An exact model, however, would be built the same, have the same load carrying capacity, the same sidewalls, and thus the same max p.s.i. under load.

 

The orignial tire on my 97 4x4 where the 265x70R17 GoodYear ATS. When I bought the truck the previous owner had the Michelin LTX M/S on it. I tried running the recommended pressure which was 28 front 32 rear. The truck drove horribly!! The tires squealed going 3 mph while parking the truck. The front of the truck was soft and un-safe to drive. Now why would Michelin want me to use my tire like this? Oh wait they don't that is for the GoodYear tire.

 

I know you guys get these posts all the time because I just read a million of them but hardly any with 18in stock rims. I just bought a used 04 F-150 FX4 with 275/65-18 stock tires on it, but I'm interested in getting bigger tires (taller & maybe wider) to make my truck look more like an off-road type vehicle. I would like to do minimal adjustments such as gear ratio, speedo, etc., but I would like slightly bigger tires. I think my truck also has a lift, but I'm not sure how much. Can anyone help with info? I have a link to pictures below if that helps.

http://pg.photos.yahoo.com/ph/dustin...dg/truck02.jpg

 

Rim size doesnt really effect how big of a tire you can run (well assuming you can afford it and find tires avaialble in those sizes)... I mean its the deminsions of the tire that determines if it will fit. The backspacing is what you want to pay attention to on rim. Also remember the same size tire measured metrically will be listed different for different rims. Like a 285/75 on a 16" rim is the same physical size as a 285/70 on a 17" rim, just that the hole in the middle is bigger. I wasnt aware that there was a stock 18" rim for an f150, I guess ford is jumping on the big rim bandwagon!

 

Yeah, but Ford's wheels suck.

Case in point: I was at a very large Ford dealership waiting for parts, and there was a 2006 Shelby Mustang with OEM 20" wheels sitting outside (to be checked in for some kind of service).

I got to looking at the car, then went in and had a conversation about it with some of the service guys who work there. I mentioned how the wheels seemed to look extremely heavy - yeah, they were big rims, but these suckers had a ton of metal on 'em, too. The service guys said not only did they look overly heavy, but they were overly heavy, and said it was an aboniation that a car of that price range - supposedly a sports car - came with those wheels on it. I felt the same way.

Ford, or supposedly even better, Shelby, isn't designing cars for performance as much as he is (or they are) following the trends, and doing so in the worst possible way.