Diff switch from 3.55 to 4.10

[Bullet]

7 hours ago, Evan said:

Man why am I even putting the effort in thinking about this

Agreed...save your brain cells for something that requires actual thought.

 

It's simple, the GPS does all the thinking for you.  GPS the truck and adjust the Smarty tire size so that the speedo matches the GPS perfectly at highway speed.  Whatever tire size matches the speedo and GPS together is your actual tire size...no thought required.

[Mopar1973Man]

2 hours ago, Bullet said:

GPS the truck and adjust the Smarty tire size so that the speedo matches the GPS perfectly at highway speed.

 

The only problem is you have to stop, shut down, plug in the programmer, key on, flash your change, then key off. Then unplug and fire up for a test run again. Same thing for CCD Network tool. 

[Bullet]

Just now, Mopar1973Man said:

 

The only problem is you have to stop, shut down, plug in the programmer, key on, flash your change, then key off. Then unplug and fire up for a test run again. Same thing for CCD Network tool. 

Yep...unfortunately that's part of it.  But also a good time to experiment with different Catcher and REVO settings as well so you can kill 2 birds...   

 

I just rip it down the highway about 5 exits down, pull in at the gas station and make adjustments.  Then head back the other way and do the same.  I've had 3 different tire sizes so I've had to do this 3 times in 20+ years of ownership.  Not hardly what I would call an inconvenience.

 

Cutting my truck in half, removing 2 feet of frame and welding it back together was a horrendous inconvenience...by comparison. 

[Mopar1973Man]

By chance what tire size? You can get close using this tool.

https://tiresize.com/calculator/

 

Revolutions per mile of a mounted tire under load will generally be about 3% more than the calculated number.

Individual tire specs may vary from the calculations. However, you can choose from the populated list of tires to view the manufacturer specs for each tire. Specs are based on an inflated tire mounted on the 'Measured Rim' size and NOT installed under the weight of a vehicle. (If you measure the tire on your vehicle from the ground up, it will be shorter than the manufacturer diameter spec.)

Tire widths will vary slightly depending on the rim width. Generally the tire width will change 2/10" for every 1/2" in rim width when mounted within the rim range. Tire diameter is not significantly affected by rim width.

Edited July 16, 2019 by Mopar1973Man

[Evan]

285x75x17

 

Just gps verified. Speedo set at 80mph cruise control on GPS reads 79.5 

For me the tape measure works great from alignment to setting tire size. It would be way off to plug in 35" off alittle to plug in what manufacturer says it is.

 

I'd screen shot it but it was a app on my phone no way to get speed and app reading at the same time. I'm sure the wrong one that I didnt calibrate or something and it was reading 5-10 mph off. Lol.

Close enough for me. 

 

I wonder if cruising done the rd the tires heat up and gain alittle pressure and height 

[Bullet]

3 minutes ago, Evan said:

285x75x17

I thought you said you had 35's?  285/75/17 is far from a 35.  My previous 305/75/16's were only 34.2 new and 34.0 after some wear.  285/75/17 is more like a 33...big difference.

[Evan]

https://www.deantires.com/tires/back-country-mt/specs

 

Heres the specs look it up yourself.

[Bullet]

Looks like our definitions of 35's differ slightly...no worries. 

[Evan]

By .5" lol

 

Heres a set of tires I have that say 35x12.5x17 on the sidewall same height as my 285x75x17 but look much bigger because they're wider.

 

The 33x12.5x15s i have on my jeep are noticably shorter than my other tires

Edited July 16, 2019 by Evan

[Bullet]

Lol...more like 2"s

[Evan]

Lol.

 

[Bullet]

Lol...very creative...awesome artwork!  Nice looking truck too!  On tires marked 33 or 35/12.50 you can take a full inch off of that after they get mounted and installed.  They are really 32's and 34's true size...or less.  What I'm saying is that tires will roll a full inch shorter than the manufacturer says on the truck.  So your 35's which are a manufacturer stated 34.06's are actually closer to 33.06 rolling on the truck...or even less. 

 

How else could you explain why you have your Smarty set to 32.75 and your speedo is gps correct?  Why don't you have your Smarty set to 34.06...or even 35?  Because the tire is actually 32.75 or very close to it.  Not even a true 33 inches.  

 

I don't have a problem with you believing you have 35's if that's what you want to do.  You can even call them 40's if it makes you feel good.  Cheers! 

 

 

 

 

 

 

[Haggar]

Not sure how to start this so gonna jump in.

 

You can't use the sidewall information, as that is a metric for catagorizing tires.   These dimensions change the moment a tire touches the ground.

 

The number you need (and it is rarely given up front, but most tire manufacturers list this data somewhere) is the number of revolutions per mile that tire will have (or they will give you the "loaded diameter" or "rolling radius").  The reason for this is our tires are not round when loaded.  How much they change is dependent on the inflation pressure, temperature and the amount of actual load.  This is where/how the tire manufacturers calculate the contact patch for a given tire.

 

So just be careful when looking at some of the charts.  Many of them are just the mathematical theoretical diameter converted to circumference and given.  The tire manufacturers have better numbers on their tires for approximate rolling radius.

 

HTH

 

Hag

[Evan]

Not sure what to think anymore.

32.75 works for my tape measure and me

[Bullet]

When I buy tires I buy for true size rather than what the manufacturer says.  I'm running what I call 33's now which are 305/55/20's and an actual rolling size of 33.2.  Some call them 35's cuz they are >1" taller than 33/12.50's.  My next tires will be what I call 35's which are 325/60/20's and an actual rolling size of 35.4.  Some call those 37's. 

[dripley]

I buy 265's and call them 265's. They came on the truck and I like them. No muss no fuss. 

[wil440]

I'm off to get 4 tyres this weekend as the BFG muds are cracking, truck has 285/75/16 now but what I'm after is a set of E rated which here is 126/123, I have the choice of 2 tyres here in the UK... Cooper STT Pro and something else which I can't remember, Coopers look ok but they have been downrated to 68mph or speed range K  Is this just here or what ? I did check and sellers in the USA are still listing this tyre as Q  99 mph,  68 is low and insurance would not pay if the truck was in an accident, there seems to be more remolds than new at E rated load here.

Will be staying with 285 75 or 305 70, my speedo is out with the 285's that are on it but it doesn't matter to me one bit as I have a big truck sat nav which warns me way before I'm at my trucks speed limits and I'm always driving Miss Daisy anyway cos I'm too old, trucks too big, roads too small, well the ones I drive on mostly are  

[dripley]

Pretty sure my Coopers are R rated at 106.

[Mopar1973Man]

The Hankook ATm 245/75 R16 are S speed rating (112 MPH).

 

[Bullet]

3 hours ago, wil440 said:

I have the choice of 2 tyres here in the UK...

You know it's really small things like this that we can easily take for granted in the USA...as our choices are almost endless...and not just pertaining to tires.  I greatly appreciate all the freedoms we have and those that made them possible.  Sorry off topic...I'm feeling extra patriotic today.  

 

On topic I would stay away from any tire rated that low.  Kinda gives you an idea of the quality of the tire.  I would look at other tire sizes if it meant that I had more choices.  There's not a tremendous difference in height, if any, between a 285/75/16 and a 305/70/16.  The 305 will be just slightly wider tread...that's all.  They will both go on the same wheel size.  Good luck with your purchase! 

 

 

Edited July 17, 2019 by Bullet