Tire (and a few wheel) options spreadsheet
- Thread starter Markarian421
- Start date
The pic below shows calculations to determine how the offset and rim width change the overall position of the wheel relative to the suspension (for a 285/70R17 +35 on 8.5" width rim). The additional poke is 37.7 mm (or 1.48") when compared to the stock 20" wheel. So, the new tire will still be under the fender. The only thing that changes if I go to the 285/75R17 is the overall diameter of the wheel.
If I would've chosen the Method 708 (+40 offset, 9" wide rim), the actual poke would be 39.1 mm which is more than I'd see with the +35 offset/8.5" rim on the 703s. The calculated values are shown in the second picture.
Here is a link to the offset calculator and wheel comparison: Alloy Wheel & Tyre Fitment Calculator. Offset, Tyre Stretch and Speedo Error | Will They Fit
Here is the formula to calculate the difference in Poke (width of wheel in inches, offset in mm):
(width of new wheel - width of old wheel)/2*25.4 + (offset of old wheel - offset of new wheel)=change in poke
For the 703:
(8.5-7.5)/2*25.4 + (60-35) = +37.7 mm (1.48") additional poke
For the 708:
(9.0-7.5)/2*25.4 + (60-40) = +39.05 mm (1.54") additional poke
I think the 285/75R17 will fit under static loads, but may deform enough during dynamic loading to rub a little bit. So, if I go with the larger diameter, I'll be looking at doing a proper suspension upgrade with just enough lift to give me a comfortable clearance. Radflo already has something out, but I'm wondering if Bilstein will also come out with an LC tuned suspension package. I'm just not sure the juice is worth the squeeze to get an extra 0.5" to 1.5" clearance for the type of off-roading I'm going to do in the LC. I may wait and see how the LC performs with the new boots and stock suspension on the trails before trying something new. Plus, with more time, we'll probably have more options and I'll be able to find the right suspension for my off-roading.
I was looking the 708 HD as well. I wanted to get the Bead Grip (I don't think they offer any bead lock to fit). Sorry, but I don't know what vehicle you are using as a baseline for poke - I'm guessing you have a Premium, since you use 20". I don't have a 1958, so I think we have same poke. I'm also looking at rub at full turn when flexed. I'm looking at Dobinson's IMS kit. Too bad the wheel well isn't in their calculator!!
Thank-you for sharing your insight. I'm still thinking to get 18s though (708) and I will get a ~2" lift in the spring.
The wheel on the 1958 is a 7" width and +50 offset on an 18" rim. The 708 HD is a good look and will look really nice on the LC. The calculation for the comparison of the 1958 wheel to the 708 is...
(9"-7")/2 *25.4 + (50-40) = 35.4 mm extra poke
That's actually a little bit less than the poke I'd see when comparing the 703 to the standard wheel on the LC 20" wheel.
One more thing to think about...the weight of the 708 HD is 36.43 lbs (18") and the weight of the 703 is just 27.84 lbs (17"). So, not only does the 708 HD weigh substantially more (31% more), the amount of rotational inertia it has will also be magnified because it is a larger diameter (rough estimate would be that the heavier wheel will have more than 45% rotational inertia than the lighter and smaller 17" wheel). Rotational inertia is only important when you are speeding up or slowing down.
