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I will measure when I get home tonight. The diameter difference is 2.76 inches but Ill get a true pavement to top of tire measurement tonight
Holy! I saw your truck at Rucki's today getting your tires installed! Too funny. I was down with my 6 RV tire/wheels getting the Ford OE TPMS sensors installed. Small world...
Holy! I saw your truck at Rucki's today getting your tires installed! Too funny. I was down with my 6 RV tire/wheels getting the Ford OE TPMS sensors installed. Small world...
wow That's cool. It was there from about 530am until 1130am. Dropped it off before work and picked it up at lunch. I didn't think anyone around here was on the forum. Steve gave me $425 for my Contitracs towards the Coopers. The second set of tires I bought there. Good experience with Steve.
Yeah, Steve and Alex know their stuff for sure and are always very fair on pricing. I've bought 4 sets of tires there in the last few years plus the 6 GY G614's on my RV. The only tires I didn't buy from them are my current ones on my 2017 as they couldn't get what I wanted from their regular supplier and were way too expensive. It's funny, not only did I notice your 17 but said, wow, good choice getting the Cooper's. Anyways, sorry for the thread hijack...
Yeah, Steve and Alex know their stuff for sure and are always very fair on pricing. I've bought 4 sets of tires there in the last few years plus the 6 GY G614's on my RV. The only tires I didn't buy from them are my current ones on my 2017 as they couldn't get what I wanted from their regular supplier and were way too expensive. It's funny, not only did I notice your 17 but said, wow, good choice getting the Cooper's. Anyways, sorry for the thread hijack...
No worries and Thanks. A coworker of mine has 2013 Titan and is running the Cooper AT/3's. That's where I first noticed them.
if you're looking at increasing your truck's tire size, then that will reduce the effective axle ratio. If you stay with the 3.73, then you may not be happy with the resulting performance.
Based on this, I can still stuff 34" tires (285/75R 18) in there and get comparable mileage. I believe the bigger tire makes for lower RPM which is better for gas mileage. I guess the caveat here is your speedo is off by 5mph unless you get that adjusted somehow. I'm really surprised FORD used this small of a tire on a Super Duty truck in the first place. I'm going to have to keep my eyes open for other similar trucks/tire sizes.
Based on this, I can still stuff 34" tires (285/75R 18) in there and get comparable mileage. I believe the bigger tire makes for lower RPM which is better for gas mileage. I guess the caveat here is your speedo is off by 5mph unless you get that adjusted somehow. I'm really surprised FORD used this small of a tire on a Super Duty truck in the first place. I'm going to have to keep my eyes open for other similar trucks/tire sizes.
Usually every inch taller a tire is it throws the speedometer off by 2 mph roughly lower then what you're actually going. Some programmers can correct this and yes taller tires almost act like a double overdrive by lowering your rpm's. Bad part the gearing will be affected also. A one inch height gain may drop the 3.73 gears in the 3.60 range so pulling performance won't be as good. Not as bad with the newer tranny's vs a few years back. Truck's look so much better with larger tires it's worth the hit!
So I got a chance to measure the Cooper 285/75r18's tonight. I'll post a picture of the TPMS to show the reason for the difference. Also I know this has been gone over many times but does anyone know the precise number I can lower the air pressure to and not have a TPMS Error code?
TPMS as left by the tire shop. How much lower can I go without an error code?
Front tire. (34.83) actual 34 1/8
Rear tire. Looks to be at 34 3/8 but it's at 78-79psi and no engine weight.
Read up on Forscan and you can lower your air pressure to any level you want. Running 80 in the rears when unloaded causes an unnecessarily rough ride and premature wear. I run 60 in the rear unloaded now but may drop it further...
Smaller tires yield quicker acceleration. I have the smallest tire size offered and I'm OK with it.
Troverman - Not for nothing but I didn't buy my HD truck to race down the road. If that were the case, I'd have kept my 2015 F150 3.5EB because it put out 365HP and 410TQ and was 2K lbs. lighter. I want bigger tires for more ground clearance and better off-road traction. Plus the bigger tires LOOK so much better on a full size truck than the stock tires - especially on a 4X4 model.
Troverman - Not for nothing but I didn't buy my HD truck to race down the road. If that were the case, I'd have kept my 2015 F150 3.5EB because it put out 365HP and 410TQ and was 2K lbs. lighter. I want bigger tires for more ground clearance and better off-road traction. Plus the bigger tires LOOK so much better on a full size truck than the stock tires - especially on a 4X4 model.
My point wasn't racing. It was that larger tires make the truck accelerate more slowly...you know, like when pulling a heavy trailer up an on ramp, etc. When I put 35x12x18 BFG KO2 tires on my 2016 diesel King Ranch, I noticed a definite loss in acceleration. Tires sure looked great though.
Ah. I thought you had the AT tires. The AS tires were smaller. 275/65/18 which are 32" tall. The new tires look great!
Originally Posted by LiquidSteam
Also that diameter measurement is taken with the tire laying on its side on a flat surface. Once you split 6-7k lbs on four on them in the vertical position the location where the rubber meets the road so to speak flattens out. My stock tire was 275/65r18 and is 32.07 inches in diameter but once mounted on the truck it only measured 31.5 inches from pavement to the top of the tire.
my new tires are 34.83 diameter. Ill measure them tonight from the pavement and give you the actual "height" number.
truck looks much much better!!! notice an improvement in ride?
my 17' came with 275-70'r18's and I immediately changed to 285-75-18 toyo's, 21,000 miles on them now and i have no regrets except that i want to go bigger next time around but they arent wearing fast enough! haha
I was able to get my speedo corrected with forscan to within 1%. check the spreadsheet for my #'s.
The power loss was noticeable, but not enough to worry over, i do wish they offered 3.73's in the diesel
06-29-2017, 03:37 PM
