JK Larger Wheel/Tire Analysis for Stock Fender Coverage
06-15-2013, 09:24 PM
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JK Larger Wheel/Tire Analysis for Stock Fender Coverage
Hi Everyone,
I’ve been looking to upgrade the stock look of my JK by adding some bigger tires and possibly new wheels. I would really love to run 35” tires but am somewhat worried about the treads extending past the stock JK fenders flares, to which I have been pulled over for before. The "crime fighters" in my area seem to be fairly strict and MN has laws on the books about this.
I did a little analysis on how the stock fenders would cover larger wider tires, and thought i would share it for those facing a similar situation. The below analysis looks at the stock JK wheels, 17”x7.5” with 6.25” backspacing and 2” of offset. As well as Mickey Thompson Classic III 17”x9”wheels with 4.5” backspacing and -0.5” offset. For the purpose of determining fender flare coverage of larger 285, 305 and 315mm wide tires.
link to M/T Classic III specs https://www.mickeythompsontires.com/...lassicIIIBlack
This post does not look at fit of tires/wheels i.e. - required backspacing or required lift for larger tires.
************************************************** ******
The stock tires are Goodyear Wrangler SRA tires are 255/17/75
I will also look at 285, 305 and 315 tire widths.
Please use Figure 1 for dimension reference.
Figure 1
A= Width of the wheel divided by 2
B= Backspacing of the wheel
C= Offset of the wheel
D= Width of the tire divided by 2
E= Distance between the outer edge of the tire and the outer edge of the stock JK fender.
************************************************** ********
First I will look at the stock configuration:
The stock JK wheel has the following measurements
A= 3.75” (7.5” divided by 2)
B= 6.25” (published backspacing of stock wheel)
C= 2” (Published Offset of stock wheel)
The tire width is 255mm, 255mm*0.0393” = 10.02” for my interest I will take 10.02”/2 which equals 5.01”
D = 5.01”
The outer most point of the stock tire will extend ((D-A)+(A-C)) 3.01” from the Hub and (D-A) 1.26” past the outer edge of the stock wheel.
For this analysis I took a” rough measurement” and will assume the stock fenders extend 0.5” past the widest part of the front tire and 1.0” past the widest part of the rear tire.
E= Front is 0.5” Rear is 1.0”
I will use these values as the baseline values for my comparative analysis to determine how much larger tires will extend past the stock wheel to determine if the stock fenders will cover the tread.
***
For 285 width tires on stock JK wheel:
A= 3.75”
B= 6.25”
C= 2”
D= 5.60” (a difference of 0.59”)
The outer most point of the 285 tire will extend ((D-A)+(A-C)) 3.60” from the Hub and (D-A) 1.85” past the outer edge of the stock wheel.
***
For 305 width tires on stock JK wheel:
A= 3.75”
B= 6.25”
C= 2”
D = 5.99” (a difference of 0.98”)
The outer most point of the 305 tire will extend ((D-A)+(A-C)) 3.99” from the Hub and (D-A) 2.24” past the outer edge of the stock wheel.
***
For 315 width tires on stock JK wheel:
A= 3.75”
B= 6.25”
C= 2”
D = 6.189” (a difference of 1.179”)
The outer most point of the 315 tire will extend ((D-A)+(A-C)) 4.189” from the Hub and (D-A) 2.43” past the outer edge of the stock wheel.
Conclusion for stock wheels, stock flares and wider tires- I took the distance calculated from the outer edge of the wheel hub to the widest part of the tire (3.01” for stock, which yields 0.5” fender coverage in the front and 1” in the rear ) and compare it against what I calculated for the wider tires.
285: (3.01” vs 3.60”) The front tires would extend 0.09” past the front fenders and the rear tires would still have 0.41” of room under the rear flares.
E= Front -0.09” Rear 0.41”
305: (3.01” vs 3.99”) the front tires would extend 0.48” past the front fenders and the rear tires would still have 0.02” of room under the rear flares.
E= Front -0.48” Rear 0.02”
315: (3.01” vs 4.189”) the front tires would extend 0.679” past the front fenders and the rear tires will extend 0.179” past the rear flares.
E= Front -0.679” Rear -0.179”
************************************************** ***********
************************************************** ***********
Now I will look as all 4 tires widths with the M/T Classic III 17”x9”wheels with 4.5” backspacing and -0.5” offset.
Stock 255/17/75 Goodyear Wrangler SRA tires
A= 4.5”
B= 4.5”
C= -12mm or -0.47” (12*0.0393)
D= 5.01”
The stock tire on the M/T Classic III wheel will extend ((D-A)+(A-C)) 4.54” from the Hub or (D-A) 0.51” past the outer edge of the stock wheel.
For 285 width tires on M/T Classic III wheel:
A= 4.5”
B= 4.5”
C= -12mm or -0.47” (12*0.0393)
D= 5.60”
The 285 tire on the M/T Classic III wheel will extend ((D-A)+(A-C)) 5.13” from the Hub or (D-A) 1.1” past the outer edge of the stock wheel.
For 305 width tires on M/T Classic III wheel:
A= 4.5”
B= 4.5”
C= -12mm or -0.47” (12*0.0393)
D= 5.99”
The stock tire on the M/T Classic III wheel will extend ((D-A)+(A-C)) 5.52” from the Hub or (D-A) 1.49” past the outer edge of the stock wheel.
For 315 width tires on M/T Classic III wheel:
A= 4.5”
B= 4.5”
C= -12mm or -0.47” (12*0.0393)
D= 6.189”
The stock tire on the M/T Classic III wheel will extend ((D-A)+(A-C)) 5.719” from the Hub or (D-A) 1.689” past the outer edge of the stock wheel.
Conclusion for M/T Classic III wheels stock flares and all tires- I took the distance calculated from the stock configuration of the outer edge of the wheel hub to the widest part of the tire (3.01” for stock, which yields 0.5” fender coverage in the front and 1” in the rear ) and compare it against what I calculated for the tires on the M/T Classic III wheel.
255 stock tire: (3.01” vs 4.54”) The front tires would extend 1.03” past the front fenders and the rear tires will extend 0.53” past the rear flares.
E= Front -1.03” Rear -0.53”
285: (3.01” vs 5.13”) The front tires would extend 1.62” past the front fenders and and the rear tires will extend 1.12” past the rear flares.
E= Front -1.62” Rear -1.12”
305: (3.01” vs 5.52”) the front tires would extend 2.01” past the front fenders and and the rear tires will extend 1.51” past the rear flares.
E= Front -2.01” Rear -1.51”
315: (3.01” vs 5.719”) the front tires would extend 2.209” past the front fenders and the rear tires will extend 1.719” past the rear flares.
E= Front -2.209” Rear -1.719”
here is the data in table format.
it looks like i could run 285's with no fender flare modifications, and could run 305's and possibly 315's with new fender flares. I'm not a fan of the big bushwacker "pocket" style flares and I believe trailmods offer an additional 1.5" but-damn, they are expensive!
I’ve been looking to upgrade the stock look of my JK by adding some bigger tires and possibly new wheels. I would really love to run 35” tires but am somewhat worried about the treads extending past the stock JK fenders flares, to which I have been pulled over for before. The "crime fighters" in my area seem to be fairly strict and MN has laws on the books about this.
I did a little analysis on how the stock fenders would cover larger wider tires, and thought i would share it for those facing a similar situation. The below analysis looks at the stock JK wheels, 17”x7.5” with 6.25” backspacing and 2” of offset. As well as Mickey Thompson Classic III 17”x9”wheels with 4.5” backspacing and -0.5” offset. For the purpose of determining fender flare coverage of larger 285, 305 and 315mm wide tires.
link to M/T Classic III specs https://www.mickeythompsontires.com/...lassicIIIBlack
This post does not look at fit of tires/wheels i.e. - required backspacing or required lift for larger tires.
************************************************** ******
The stock tires are Goodyear Wrangler SRA tires are 255/17/75
I will also look at 285, 305 and 315 tire widths.
Please use Figure 1 for dimension reference.
Figure 1
A= Width of the wheel divided by 2
B= Backspacing of the wheel
C= Offset of the wheel
D= Width of the tire divided by 2
E= Distance between the outer edge of the tire and the outer edge of the stock JK fender.
************************************************** ********
First I will look at the stock configuration:
The stock JK wheel has the following measurements
A= 3.75” (7.5” divided by 2)
B= 6.25” (published backspacing of stock wheel)
C= 2” (Published Offset of stock wheel)
The tire width is 255mm, 255mm*0.0393” = 10.02” for my interest I will take 10.02”/2 which equals 5.01”
D = 5.01”
The outer most point of the stock tire will extend ((D-A)+(A-C)) 3.01” from the Hub and (D-A) 1.26” past the outer edge of the stock wheel.
For this analysis I took a” rough measurement” and will assume the stock fenders extend 0.5” past the widest part of the front tire and 1.0” past the widest part of the rear tire.
E= Front is 0.5” Rear is 1.0”
I will use these values as the baseline values for my comparative analysis to determine how much larger tires will extend past the stock wheel to determine if the stock fenders will cover the tread.
***
For 285 width tires on stock JK wheel:
A= 3.75”
B= 6.25”
C= 2”
D= 5.60” (a difference of 0.59”)
The outer most point of the 285 tire will extend ((D-A)+(A-C)) 3.60” from the Hub and (D-A) 1.85” past the outer edge of the stock wheel.
***
For 305 width tires on stock JK wheel:
A= 3.75”
B= 6.25”
C= 2”
D = 5.99” (a difference of 0.98”)
The outer most point of the 305 tire will extend ((D-A)+(A-C)) 3.99” from the Hub and (D-A) 2.24” past the outer edge of the stock wheel.
***
For 315 width tires on stock JK wheel:
A= 3.75”
B= 6.25”
C= 2”
D = 6.189” (a difference of 1.179”)
The outer most point of the 315 tire will extend ((D-A)+(A-C)) 4.189” from the Hub and (D-A) 2.43” past the outer edge of the stock wheel.
Conclusion for stock wheels, stock flares and wider tires- I took the distance calculated from the outer edge of the wheel hub to the widest part of the tire (3.01” for stock, which yields 0.5” fender coverage in the front and 1” in the rear ) and compare it against what I calculated for the wider tires.
285: (3.01” vs 3.60”) The front tires would extend 0.09” past the front fenders and the rear tires would still have 0.41” of room under the rear flares.
E= Front -0.09” Rear 0.41”
305: (3.01” vs 3.99”) the front tires would extend 0.48” past the front fenders and the rear tires would still have 0.02” of room under the rear flares.
E= Front -0.48” Rear 0.02”
315: (3.01” vs 4.189”) the front tires would extend 0.679” past the front fenders and the rear tires will extend 0.179” past the rear flares.
E= Front -0.679” Rear -0.179”
************************************************** ***********
************************************************** ***********
Now I will look as all 4 tires widths with the M/T Classic III 17”x9”wheels with 4.5” backspacing and -0.5” offset.
Stock 255/17/75 Goodyear Wrangler SRA tires
A= 4.5”
B= 4.5”
C= -12mm or -0.47” (12*0.0393)
D= 5.01”
The stock tire on the M/T Classic III wheel will extend ((D-A)+(A-C)) 4.54” from the Hub or (D-A) 0.51” past the outer edge of the stock wheel.
For 285 width tires on M/T Classic III wheel:
A= 4.5”
B= 4.5”
C= -12mm or -0.47” (12*0.0393)
D= 5.60”
The 285 tire on the M/T Classic III wheel will extend ((D-A)+(A-C)) 5.13” from the Hub or (D-A) 1.1” past the outer edge of the stock wheel.
For 305 width tires on M/T Classic III wheel:
A= 4.5”
B= 4.5”
C= -12mm or -0.47” (12*0.0393)
D= 5.99”
The stock tire on the M/T Classic III wheel will extend ((D-A)+(A-C)) 5.52” from the Hub or (D-A) 1.49” past the outer edge of the stock wheel.
For 315 width tires on M/T Classic III wheel:
A= 4.5”
B= 4.5”
C= -12mm or -0.47” (12*0.0393)
D= 6.189”
The stock tire on the M/T Classic III wheel will extend ((D-A)+(A-C)) 5.719” from the Hub or (D-A) 1.689” past the outer edge of the stock wheel.
Conclusion for M/T Classic III wheels stock flares and all tires- I took the distance calculated from the stock configuration of the outer edge of the wheel hub to the widest part of the tire (3.01” for stock, which yields 0.5” fender coverage in the front and 1” in the rear ) and compare it against what I calculated for the tires on the M/T Classic III wheel.
255 stock tire: (3.01” vs 4.54”) The front tires would extend 1.03” past the front fenders and the rear tires will extend 0.53” past the rear flares.
E= Front -1.03” Rear -0.53”
285: (3.01” vs 5.13”) The front tires would extend 1.62” past the front fenders and and the rear tires will extend 1.12” past the rear flares.
E= Front -1.62” Rear -1.12”
305: (3.01” vs 5.52”) the front tires would extend 2.01” past the front fenders and and the rear tires will extend 1.51” past the rear flares.
E= Front -2.01” Rear -1.51”
315: (3.01” vs 5.719”) the front tires would extend 2.209” past the front fenders and the rear tires will extend 1.719” past the rear flares.
E= Front -2.209” Rear -1.719”
here is the data in table format.
it looks like i could run 285's with no fender flare modifications, and could run 305's and possibly 315's with new fender flares. I'm not a fan of the big bushwacker "pocket" style flares and I believe trailmods offer an additional 1.5" but-damn, they are expensive!
Last edited by CRV_05; 06-15-2013 at 09:38 PM.
06-15-2013, 09:44 PM
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....damn......did you get bored at home or what? It'll provide a straight answer and some easy calculations for people looking to stay legal though, that's for sure.
Thank you for putting in the time!
Sent from my DROID4
Thank you for putting in the time!
Sent from my DROID4
06-15-2013, 10:24 PM
#3
JK Freak
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I couldn't had figured all that out with a calculator, cell phone app, and a cheat sheet in front of me.
Killer job on that though if it's all accurate. I'd still give you an A for effort regardless.
Killer job on that though if it's all accurate. I'd still give you an A for effort regardless.
06-16-2013, 05:53 AM
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Question: What do the state laws reference as needing coverage by the fenders? The entire tire or just the treads?
In your post you indicated you are worried about the tread sticking out beyond the fender. I think what you calculated was possibly how far the overall tires sticks out??? (and there is roughly an inch in difference between the tread and the sidewall relative to the fender.) Something to think about.
In your post you indicated you are worried about the tread sticking out beyond the fender. I think what you calculated was possibly how far the overall tires sticks out??? (and there is roughly an inch in difference between the tread and the sidewall relative to the fender.) Something to think about.
Last edited by rdreng; 06-16-2013 at 06:20 AM.
06-16-2013, 05:56 AM
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Awesome analysis, I'm a data junkie.. love it.
I've been considering this same question. How about the impact to the inside side of the tire? How much clearance/running is there with 285s+? Did you look at that?
I've been considering this same question. How about the impact to the inside side of the tire? How much clearance/running is there with 285s+? Did you look at that?
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06-16-2013, 01:12 PM
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Question: What do the state laws reference as needing coverage by the fenders? The entire tire or just the treads?
In your post you indicated you are worried about the tread sticking out beyond the fender. I think what you calculated was possibly how far the overall tires sticks out??? (and there is roughly an inch in difference between the tread and the sidewall relative to the fender.) Something to think about.
In your post you indicated you are worried about the tread sticking out beyond the fender. I think what you calculated was possibly how far the overall tires sticks out??? (and there is roughly an inch in difference between the tread and the sidewall relative to the fender.) Something to think about.
It reads: 169.734 AUTOMOBILE FENDERS.
Every passenger automobile shall have fenders, or other devices, that are designed to prevent, as far as practicable, water, dirt, or other material being thrown up and to the rear by the wheels of the vehicle.
It is obviously open to interpretation but the definition of Practicable is - Adjective, 1) Able to be done or put into practice successfully. 2) Able to be used; useful.
Yes, what i calculated is the tire width, not tread width. that information is hard to obtain as the manufacture does not publish a tread width, only a sectional width. so in practicality the tread width would be less. my numbers would be on the conservative side.
Thanks for reading!
06-16-2013, 01:16 PM
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Thanks for taking the time to read through my "short" analysis...
