Hey guys does anyone know what the rollling diameter is for stock is250 AWD, my diff got fu***d and i think that's what cost it currently getting if fixed don't want it to happen again... Im currently rinning 19x8.5 + 30 225/40 & 19x9.5 + 30 255/35 ....Thanks

 

What size wheels and tires were you running?

 

Rolling diameter should be 25.

 

19x8.5 + 30 225/40
19x9.5 + 30 255/35

 

[QUOTE=laobo979;8793228]Rolling diameter should be 25.[/QU


i have no idea how this works or how to get it to 25 was hoping for some explanation
with my current set up what do i need to do
19x8.5 + 30 225/40
19x9.5 + 30 255/35

 

634.3mm (25.0in)

Jeff

 

think i know what u mean eg, if front tire is 225+30 just add 25 mm to front which gives you rear tire like this 225+25=50 so rear would be 255 is hat it ?

 

ok scientist can u translate into regular language lol JK
but can u explain how you get that measurement or what i need to do with my current set up to get to that

 

Stock rolling diameter is 25 inches but for AWD, it doesn't always have to be 25 inches, it can be 26, 27, etc as long as all 4 wheels are the same. The AWD is forgiving as long as front and rear are within <2% change. Looking at your set up along side some rolling diameter, you were less than 2mm off which shouldn't cause diff damage

Did you have 2 different set of tires? on front/rear? Some tires have taller side walls which makes putting two different types of tires have a larger rolling diameter.

did you ever change the oil in your diff? I don't thing rolling diameter was the cause of your diff issues

 

all 4 tires are the same and i never changer the oil can that damage it, only have to care for two years so most of these things are new to me.
and understand but no 100%, where do i measure to get 25 inch ?

 

To measure the diameter of the tire you would take the rim size and multiply it by 25.4 to measure everything in mm. Then take the width and multiply it by the smaller number with a decimal point in front of it, then multiply it by 2. Take all those numbers, add them together and the divide by 25.4.

Example:
My tire size on my awd is 225/45 17
17x25.4 = 431.8 (rim size in mm)
225 x .45 = 101.25 (one side of the height of the tire in mm)
431.8 + 101.25 x 2 = 634.3
634.3 / 25.4 = 24.97244"

Thus a 25" tire

 

Using your current tire sizes:

(f) 225/40r19 = 26.08"
(r) 255/35r19 = 26.02"

As nynick stated, as long as the front and rear are the same height, as yours are, everything should be fine.

 

Just use this calculator to do that math for you

http://www.csgnetwork.com/tiresizescalc.html

Like I said, your tire sizes, they seem to be with in spec to not have any issues. Your diff oil should be replaced every 15k miles (I've seen up to 30k with some oils). If you haven't EVER changed your diff oil in 2 years and god knows what interval the person before did it in (if you bought used), then I bet that's the reason why your diff blew up. The Diff oil viscosity can only last so long before it becomes like water. When that happens after 100k miles or so, its going to be gear metal griding on gear metal with no lubricant. The gears heat up and flex, break, chip, or gear shards build up and get caught

 

Thanks a lot you guys are the best