I have 235/70/16 tires now. Does anybody see a problem with going to 235/60/16 other than speedometer error? This would up my gearing 6.4% due to a 1.85 difference in tire diameter. (28.9528 - 27.1024 = 1.8504/28.9528 = .0639)

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97 4.6 F150, 1/8 = 10.885 @ 64.10 mph, 88 5.0 Mustang 1/8 = 7.191 @ 94.76 mph

 

Also consider the load rating for the new tires if thats important to you and how you use the truck. You might lose some payload unless the load rating is the same. Intersting what you are doing. I am intersted in waht results you get.

Only other thing would be the shift points might change slightly too. These can be changed in a 97 by replacing the speedo gear on the tranny but I don't know if they make a gear for that to go down (more teeth I think?). I know they make one for correcting up-sizing tires.

 

cphilip,

Yes, they make just about any speedometer gear you need. I had an 18 tooth from the factory with my 3.08 gear. When I switched to the 3.27 it calculated that I needed a 19 tooth. Got one from a Mustang. With 60 series tires I will need a 20 tooth which I already have from my Mustang. I'm set with speedometer gears. All the AOD Mustang gears work in the trucks. All you have to do is calculate what tooth gear you will need.

As far as load rating. I don't carry heavy loads in my bed so standard rated tires will work fine for me. I am sure they make 60 series high load tires but I won't need them. I am more concerned about how the truck will look with shorter tires than anything else.

This change to 60 series tires would give my 3.27 gear the equivalent of a 3.50 gear.



[This message has been edited by LarryS (edited 06-13-2000).]

 

Since the tires are approx. 2" shorter, you're going to have 1" more clearance in the wheel well. It may look a little strange unless you lower it.

 

StrangeRanger,

That is what I am afraid of. Wish I could see the truck with the 60s on it before I decide. My 70s are still pretty good so I don't have to make a decision soon. I have 235/60/16s on my Camaro and it looks like it is pretty big but until it is on the truck who knows what it will look like.

 

It will also look like it has a lift kit -- prized by many on this board.

 

Y2K,

A lift kit? I guess I don't understand why. Because of addtional clearance from tire to fenderwell?

[This message has been edited by LarryS (edited 06-13-2000).]

 

I did the aspect ratio change on a Nissan PU a few years ago (no rice boy comments please.) Went from 185/75-14 to 185/60-14. It accelerated MUCH better but looked as strange as hell until I lowered it 1.5." Then it ran, handled and looked a whole lot better.

Just a thought, you can get 255/65-17 light truck tires from a lot of sources (Michelin, Dunlop, Bridgestone & Pirelli among others.)
They're the same diameter as your present tires and are 3/4" wider with a lower aspect ratio. Better traction, better handling and they won't look strange. The down side is that you don't get the increase in torque multiplication from the smaller dia.

 

StrangeRanger,

I don't want to lower my truck. It would be cheaper/easier to install a 3.55 gear verses lowering. I am not sure I really want a lower gear as my 3.27 did pretty good yesterday towing my trailer in OD. The converter stayed locked although I could not maintain speed over grades. I just allow it to slow on grades and ilt does ok. Maybe I will keep the 70 series tires on my next tire change. I would like a slightly lower gear and the tires would make my gearing perfect but what would the truck look like. I am almost afraid to take the chance.

 

If you're happy with the present gear, then there's no reason to change it, there's also precious little difference between a 3.27 ans a 3.55. I agree completely about not lowering if you tow or haul -- it just reduces your capacity too much. If you want the lower profile tires for looks and handling as well as increased load rating, then you could go to the 255/65-16 without lowering.

I'm about to change wheels on my '96 from the stock 15s to either 16 or 17 and I'm debating among three tire sizes: 255/55-17 (1" dia. less) 255/65-16 (same dia as stock) and 275/60-17 (1" dia. more than stock.) There are plusses and minuses all three, but costs sure favor the 16" option. Since you've already got the 16" wheels, your best, and cheapest, bet is to optimize the tire you're running on them. Please let us know what you decide

 

StrangeRanger,

I have decided to keep my 235 70s. These make for an excellent highway gear and I can pull my trailer in OD. Though a taller gear would be better. When I orginally made this post I was not sure it would pull it. It would be better for pulling with the smaller diameter tires but I am afraid of what it would look like. I still have pretty good rubber on these so I could still change to 60s at a later date if I need a little more pulling power.

 

I put 60's on my '98 last year... Yes, it looks a bit odd, but as far as I'm concerned , the handling improvement was worth it..also, the smaller diameter did help w/ pulling power.

 

Jerry,

Do you have a pic of your truck with the 60s tires that you could post?