Need help with offset/backspacing

[Bachert24]

Apparently my truck has a 4-6" RCD suspension lift in addition to a 3" body lift. RCD says 4.75" backspacing with 18s I believe. The tires were junk when I bought the truck so I grabbed some cheap 04 Silverado wheels with low tread tires to get the truck home. Decided to stick with the 17s and throw on some 285/70/17 tires and of course they rub the control arms. Can someone educate me as to why? Is this related to the stock 04 17 back spacing or offset? I had to buy 2" spacers to get the truck home, which RCD does not recommend. For driving 1 block I'm ok with it. But I need to understand what offset wheels i need to buy to not rub. Likely going to buy 18s later on but was hoping to keep the 17s for the upcoming camping season but the new tires rub the control arms bad! Please help me! I read online what it all means but I'm still not understanding what I need specifically for my truck. I want them to stick out 2-4" so I'm thinking -44 offset but apparently the offset needed depends on the wheels size. On a 17 backspacing for 4.5" is like a plus 12 offset I guess?

 

[Bachert24]

Is the 4.75 baxkspacing the max or min? So lost lol

 

[b454rat]

Never heard of HAVING to run a min/max diameter wheel on a lifted truck. Does this have a knuckle lift? I never had or seen an RCD lift so not sure. i'd get some old school wheels, they will push the wheel out away from any suspension parts.

 

[Bachert24]

Never heard of HAVING to run a min/max diameter wheel on a lifted truck. Does this have a knuckle lift? I never had or seen an RCD lift so not sure. i'd get some old school wheels, they will push the wheel out away from any suspension parts.

This does have a knuckle lift. I currently have 17s from an 04 Silverado and the control is rubbing on the 285 tires so much so that I cannot drive the truck. I need to figure out what offset I need. I know nothing about backspacing or offset so I'm not sure wjere to start

 

[Sean Buick 76]

Okay so the stock 17x8 GM wheels have a +24 mm offset which means that from the Center of the face of the trucks hub the wheel sticks in towards the truck 24 mm further than centered. A -24 mm offset would stick the wheel out 24 mm vs Centered on the hub face.

For the backspace add 1/2” per side for the width of the rim as they are measured on the inside of the rim for width. So a 8” wide wheel is 9” total. Half of that is 4.5” subtract the +24 mm (0.945”) Offset and you get a 3.555” backspacing. Backspacing is the measurement from the back of the rim lip to the inside wheel hub mounting surface. Use a straight edge across the back of the wheel and then a tape measure to see how deep it is to the straight edge.

If it was a -24mm offset then it would be a 5.445” backspace (4.5+ 0.945”).

From the rough country website if you use a 9” wide wheel wheel then you need a 0 offset. Using a 10” wide wheel wheel you need a -19 mm offset.

The min rim diameter is related to clearing the knuckle.

 

[Bachert24]

Okay so the stock 17x8 GM wheels have a +24 mm offset which means that from the Center of the face of the trucks hub the wheel sticks in towards the truck 24 mm further than centered. A -24 mm offset would stick the wheel out 24 mm vs Centered on the hub face.

For the backspace add 1/2” per side for the width of the rim as they are measured on the inside of the rim for width. So a 8” wide wheel is 9” total. Half of that is 4.5” subtract the +24 mm (0.945”) Offset and you get a 3.555” backspacing. Backspacing is the measurement from the back of the rim lip to the inside wheel hub mounting surface. Use a straight edge across the back of the wheel and then a tape measure to see how deep it is to the straight edge.

If it was a -24mm offset then it would be a 5.445” backspace (4.5+ 0.945”).

From the rough country website if you use a 9” wide wheel wheel then you need a 0 offset. Using a 10” wide wheel wheel you need a -19 mm offset.

The min rim diameter is related to clearing the knuckle.

Thank you! Looks like the backspacing on the 04 17" wheel is 5.5" which explains the rubbing on the control arms. RCD says no more than 4.75 with 17s as well. Had I known I had the RCD lift I would have better prepared. Now I have to find cheap 17s with better backspacing or offset. Ugh!

 

[b454rat]

Too bad not closer, I have a brand set of 35s on 17x9 wheels. Debating on getting some fat 35" swampers for the 12" wide wheels I have....

 

[Sean Buick 76]

If it helps at all I don’t mind using spacers. If they are properly torqued I’ve never had an issue with them. I avoid them if I can but I’m not scared of them.

 

[DoubleC96]

@Bachert24 what wheel pattern do you have? I have 20 x 10 with zero offset and no spacers on a 1992 C1500. 2in front lift is via springs only. The 285/50 tires rub slightly on the frame at full lock left turn. Right turn it does not rub.

 

[Bachert24]

@Bachert24 what wheel pattern do you have? I have 20 x 10 with zero offset and no spacers on a 1992 C1500. 2in front lift is via springs only. The 285/50 tires rub slightly on the frame at full lock left turn. Right turn it does not rub.

I have 8x6.5. Only running 17x7.5 stockers off an 08 sierra apparently. O offset on 285 tires with 5.5 backspacing on a knuckle lift means my tires are 1" inside the control arms lol