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Discussion Starter · #1 ·
Currently I'm running a 20x9 Incubus Alloy wheel that has a +25mm offset. I am going to another 20x9 wheel with a zero offset. My wheels rub on the upper-control arm on sharp turns. With the new wheel having a zero-offset how will this affect the tires rubbing? Going to be running the same tires. (Nitto-Terra Grapplers 305/55/20)

Thanks!
 

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Discussion Starter · #3 ·

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do you think going to 0 offset is going to cause rubbing problems in wheelwells and bumper area?
 

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do you think going to 0 offset is going to cause rubbing problems in wheelwells and bumper area?
That is a possibility. Going from +25 to ZERO will move the tire/wheel OUT almost ONE inch. There is only so much room in there. The huge tires eat up a lot of real estate inside the fender well.

If possible, I would see if the wheel vendor would allow me to try them out before I bought them, to make sure I'm not trading one problem for another.
 

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SalMan - I agree. You need to mount up a front and test the fit. I had the exact tire and wheel (Ion 137) you are going to (you PM'ed me) and it rubbed BAD on the rear edge of fender/rocker panel. That 305 really swings out a bunch and stays there when you turn.

I WISH I had a positive offset wheel.
 

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Discussion Starter · #7 ·
SalMan - I agree. You need to mount up a front and test the fit. I had the exact tire and wheel (Ion 137) you are going to (you PM'ed me) and it rubbed BAD on the rear edge of fender/rocker panel. That 305 really swings out a bunch and stays there when you turn.

I WISH I had a positive offset wheel.

Dlewis the part that you said rubbed real bad was on the rear fender which is a small piece of sheet metal. That is gone compliments of the sawzall. My ONLY concern is the upper control arm up front. Thats the only rubbing that takes place. So with tire sticking out more, shouldn't this move it away from the UCA?

Thanks!
 

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Discussion Starter · #8 ·
Wheels are on.

No rubbing at all. I guess the '0' offset move the tire out an inch!
 

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No rubbing at all. I guess the '0' offset move the tire out an inch!
Moving the wheels outboard by one inch will add some heavy loads to the steering system and wheel bearings. So, now that you "fixed" your rubbing problem, you may want to invest in tie-rod sleeves or Cognito HD tie-rods along with idler arm and pitman arm braces to beef up your steering system. You can also expect shorter wheel bearing life. :D
 

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Salman - Glad it worked out. I had a buger of time getting them to fit my rig & they still hit the rear edge of front fender on occasion.

Now you need to post new pics in that garage, be sure to include one of your sawzall cut and update your signature !!
 

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Discussion Starter · #11 ·
Salman - Glad it worked out. I had a buger of time getting them to fit my rig & they still hit the rear edge of front fender on occasion.

Now you need to post new pics in that garage, be sure to include one of your sawzall cut and update your signature !!

Will do. That's the main thing. The cutting of the sheet-metal in the rear is the ley to get the tires to fit.
 

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Discussion Starter · #12 ·
Moving the wheels outboard by one inch will add some heavy loads to the steering system and wheel bearings. So, now that you "fixed" your rubbing problem, you may want to invest in tie-rod sleeves or Cognito HD tie-rods along with idler arm and pitman arm braces to beef up your steering system. You can also expect shorter wheel bearing life. :D

Go figure! Unfortunately we gota PAY to PLAY! :D
 

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I have the cognito pitman/idler kit. I plan on Cognito HD tie rod ends and wheel bearings in about two years.

Just part of the admission price !! It is worth it when your truck gets you more tail than a park bench.
 

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Discussion Starter · #14 ·
I have the cognito pitman/idler kit. I plan on Cognito HD tie rod ends and wheel bearings in about two years.

Just part of the admission price !! It is worth it when your truck gets you more tail than a park bench.
LOL!!!!! What am I expected to pay for all this??
 

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Do you think that it is more the highth or the width that is more of a issue with rubbing. If i were to go with a similar backspacing and with a tire that was the same width but a half inch smaller would i have less rubbing
 

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Discussion Starter · #16 ·
Do you think that it is more the highth or the width that is more of a issue with rubbing. If i were to go with a similar backspacing and with a tire that was the same width but a half inch smaller would i have less rubbing
Definetly the width. What kinda truck u have? With Ion 137's that I have now. Its a zero offset, 5.8 backspacing and I am running 305/55/20. After some minimal trimming, the tires do not rub at all at all turns. The reason my previous wheels were rubbing so much was the +25 offset which were too close to the sway-bar.
 

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I have an LMM and want to run 20' inch with minimal rubbing......If i went with a -18 offset would that be even better than the 0 offset
 

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I have an LMM and want to run 20' inch with minimal rubbing......If i went with a -18 offset would that be even better than the 0 offset
I believe that if you get 20 inch wheels with -18 mm offset and 305 tires, they will rub on the fender unless you get a lift kit.

Wheels with -18 mm offset are 1.81 inch further out compared to the stock wheels. Compounding that with the 305 tires is going to get them awfully close to the fenders. They will also overload the wheel bearings and tie-rods a lot worse that the wheels with ZERO offset.

As posted earlier, Try this website.
http://www.rims-n-tires.com/rt_specs.jsp

You can play around with numbers to see what happens when you make changes.

The stock 16 inch wheels are 16" x 6.5" [Offset: +28 mm ]
The stock tires are LT245/75R-16

The optional 17 inch wheels are 17" x 7.5" [Offset: +28 mm ]
The optional size tires are LT265/70R-17
 

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Discussion Starter · #19 ·
I have an LMM and want to run 20' inch with minimal rubbing......If i went with a -18 offset would that be even better than the 0 offset

Exactly what RayMich said. The perfect off-set is probably a +10. Nevertheless, if you want to put 20's and the 305's on the truck you are going to have to do some trimming of the plastic fender and actually cut a small piece of sheet metal with a sawzall to make the fit. My 305/55/20 with Ion 137's with zero do not rub at all. But this wouldnt have been possible without cutting. You may want to crank the torsion bars a bit. I took RayMich's advise an ordered a cognito pitman idler system. Its worth the 216 bucks to save your steering. Don't forget to get an alignment once this is all done.
 

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I don't think the formula is nearly so simple as just described. I have the identical Incubus wheels that Salman just pulled off, the identical offset +25, and nearly identical 305/55x20 tires (Pirelli instead of Nitto). I have no lift other than about 1.5 inches on the T-bars, while I've lowered the rear by 2 inches. Yet my Pirellis don't rub in forward motion at all, either the fender or the sway bar.

True enough that reducing offset moves the tire outboard to clear any the suspension pieces. However, mine aren't hitting there anyway. Offset and wheel width together determine clearances under the fender. As RayMich observed (7.5 rims, +28 offset) the optional factory wheels have ~5.5 inches of backspace, obviously clearing the suspension pieces. My 10-inch wheels are 11" wide overall. That means backspace is 5.5 inches at zero offset, or ~6.5 inches with +25 offset. My Pirellis clear totally, while Salman's Nittos were rubbing the sway bar ... go figure~!

Minor sidebar: my new Incubus wheels (model 505) are 20x10, while Salman's are 20x9 (??) though they appear identical in the pix (see garages). Maybe Incubus changed the spec in the year or so between our purchases. Even so, his narrower 9-inchers should have made suspension clearance easier ... go figure~!

Meanwhile, reducing offset moves the tire outboard and leaves tread exposed beyond the fender, washing the body with tirespray. Ergo, I'd be loathe to reduce my offset with 305/55x20 tires, a full 12 inches of tread width. I also don't see how a zero-offset should help with fender clearance. Mine rub the inside undercurled fender lips, but only in reverse gear. The tire's outside shoulder just barely touches the innermost corner of that fender lip at full reversing steering lock. After 1,000 miles the inside plastic pin holding the wheelhouse liner is taking a beating. Shifting the wheel outboard would simply make my tire-shoulders contact the fender lip "an inch sooner" probably hitting the outside plastic pin, rather than the inside pin.

Since Salman and I have identical NBS trucks with the identical wheel/tire sizing (before his upgrade to the new wheels) ... I'm just saying it's perhaps more complicated than we're assuming. Seems to me that some better rules-of-thumb might be:
  • You can fit 33-inchers under the NBS fenders with no lift, deminimus cutting, and minor rubbing, if any;
  • However, it's not an automatic fit and might require some intelligent manipulation;
  • A +25 offset on a 10-inch wheel is right at the limit of available steering space;
  • A 305/55x20 is at the limit of height (33.2") and width (12.0") for the NBS fenders;
  • Choosing different offset/backspacing isn't any panacea, since the WxH of tire is also determinant;
  • Choosing a 32-incher of average width (11" max) will probably be easier, almost automatic.

Edit to add: I also added the Cognito pitman braces (on Nor-Cal Nick's advice) and have only a minor lift of the T-bars. With a 2-inch drop at the rear, the front lift just about brings the truck to level. I needed zero trimming of plastic liners, but the inside undercurl of fender barely touches in reverse.
 
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