- Jan 25, 2013
- 9,332
Ok figured i would ask this since im looking at wheels again. I am looking at wheels with a 25 mm offset. Would i require spacers to run a tire taller then 30.5 on these wheels?
the roadie said:You still have to do the math, and also realize every tire is slightly different in terms of diameter (nominals aren't exact) and the edge roundness. Offset isn't enough to fully define the geometry of the relationship of the tire to the upper ball joint. You also have to know the rim width compared to stock. See if you can find out more about the rim width of the proposed wheel, and while you're doing that research, find out what the OEM wheel rim width and offset is. I haven't led anybody through this in quite a while so it will be useful to do it again for the archives here on GMTN.
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You got it in one!Darkrider_LS said:Great info thanks! The planned wheels are 17x8 with a 25 mm offset. From what I have read the oe wheels are 17x7 with 6" backspacing.
Darkrider_LS said:Awesome info Roadie! If i am following the chart correctly the new wheels have a 5.5" backspacing. But due to the fact that said rims are also an inch wider then stock and since half of said added width would be on each side of the center line of the rims. The new 17x8 rims would have the inner edge roughly at the same point as the OE 7". Thus answering my question about relation to the ubj. All i really did was gain a wider rim but no outward movement towards the outside of the truck. Thus if i want to go taller then that max 30.5-30.6 tire height i will need to run spacers.
Yep.Darkrider_LS said:Oh really??
I need to show my work as well?the roadie said:That's why I advised everybody show your work. If you can explain it adequately, it's likely right.
Darkrider_LS said:Please do so!
djthumper said:16X8 with 25mm offset 265 70R16 presently mounted but have tested with 265 75R16's for clearance.
New Wheels Photos by kc7qjo | Photobucket
I'd like my seabass served with a nice mango chutney, thank youthe roadie said:I'm not so much into just handing over a fish, nowadays.
Apparently my math was correct because it worked on my truck.navigator said:that's cheating, you have to show your math work to get full credit
The_Roadie said:You still have to do the math, and also realize every tire is slightly different in terms of diameter (nominals aren't exact) and the edge roundness. Offset isn't enough to fully define the geometry of the relationship of the tire to the upper ball joint. You also have to know the rim width compared to stock. See if you can find out more about the rim width of the proposed wheel, and while you're doing that research, find out what the OEM wheel rim width and offset is. I haven't led anybody through this in quite a while so it will be useful to do it again for the archives here on GMTN.
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nieman88 said:....you lost me (but thats not hard to do). And I searched here and other sites. Im just very confused.
im actually face palming trying to understand offset and backspacing...still.
Dumb it down for me. ...im going nuckin futz
What are you looking for?nieman88 said:
thanks muchly =)
Now I can start shopping around.
Depends on the specs of the proposed new rims. Let's take the wheels I was looking at for example with their 5.5" back space. With adapters they go down to 4" backspace which as you stated gives you around 2" of clearance. Which seems to be where most of us are after changing rims to aftermarket fsc application wheels. Iirc kyle aka Hardtrailz runs a set up that has him around 3.5" backspace on his wheels. The wheels I'm looking at start at 6 3/16" backspace which with adapters puts me between 4.5 and 4.75 backspace. Or around 1.25" clearance at minimum.Pittdawg said:What about a 25 mm offset wheel with 6x5 to 6x5.5 adapters? If the adapters are 1.5 inches thick, does that mean I would gain 2 inches of offset (that's too much!)?
1.5 inch adaptors need no grinding....paul2005tb said:question: can I purchase shorter lug bolts to mount to the hub so that when I install my 1.5in adapters there will be no need to grind down my existing lugs ?
Great news ! Thanks. I assume that adaptors less than 1.5 would come with lug bolts to replace the existing lugs.HARDTRAILZ said:1.5 inch adaptors need no grinding....
Slip on spacers are not recommeneded due to you would not have the studs sticking through the lug nuts.paul2005tb said:Im considering a low budget spacer solution:
1) 1/4 in slip-on spacers
2) Grind 1/8in off of the upper ball joint knuckle/seat .
That should get me to almost a 31.0in dia. at 245 with a tame tread pattern .