Tire and Wheel Combo Question

[Super_Dave]

I am looking at some 18x9 eight lug wheels for my BABA YAGA! project.

I am looking to run 245/45/18's in the front (9.6" tread width) and 285/45/18's in the back (11.2" tread width).

Am I going to have trouble running the 285/45's on a 9" rim in the back? I know the 245/45's in the front will be fine.

[Super_Dave]

No Opinions?

Okay, how about this question in conjunction with the previous one:

How much static drop can I expect on a C20 axle flip? (with/without removing the overloads)

I am going to install a 2.5"-3" drop spindle setup and I am trying to determine if I need 1" drop springs after the static flip. Here is how I am calculating my static rear drop:

1. Leaf pack is 3.375" tall
2. Axle diameter is 3.375"

(A) Move axle to the top of the leaf pack nets a 3.375" drop
(B) Add the radius of the axle tube (1.6875) to the leaf pack for a 5.4375" total drop.

With a 3" C30 drop spindle, I would end up with a 3/5.5 combo....? Am I calculating it right? Will I most likely be level, a slight front rake or dragging my tail?

I don't want a lot of front rake nor do I want to motor boat the rear end. I need to make a decision on the flip/front static drop needs, before installing the transmission, so I can get the pinion angle set at the same time.

The trans is going in mid-week next week, so I have a very small window of time and would like to order parts ASAP as needed.

Thanks!

[SCOTI]

Your math is correct for the rear. I would guess about 6" rear drop @ least.

[Super_Dave]

Originally Posted by SCOTI

Your math is correct for the rear. I would guess about 6" rear drop @ least.

Scoti,

Thanks for the reply.

So, it looks like I would need a C-Notch if I am approaching the 6" threshold, correct?

With the C30 3" drop spindles, do you think I will be motor boating the rear? Will I need additional help in the front, like drop springs... 1", 2"?

Lastly, I was hoping to stay in the 4-5" range and avoid a frame notch. if I want to stay in the 4" rear drop area, are there other alternatives that will work, other than an axle flip, that will keep it level or a slight front rake... given my wheel and tire combo?

Thanks!

[SCOTI]

4" rear drop would be shackle & hanger combo (2" drop each). 6" rear drop on leaf trucks can get by w/o a notch (approx. 2" of travel) but your better off w/more clearance. The factory bump-stops will make contact & will need to be removed and/or replaced w/something shorter.

I do think you'll need to go w/shorter springs in the front in addition to the spindles if targeting the 6" rear drop.

[wilkin250r]

Wait, back to the original question. Are you SURE a 245/45/18 will fit on a 18x9 rim? A 9.6" width on a 9 inch rim?

I'll be honest, I haven't dealt with low-profile tires much, but I know that a standard 33x12.5R15 will NOT fit on a 12" rim, the manufacturer specifies 8-10" width.

Unless low-profile tires work radically different, I think your front tires are too narrow (or your wheels are too wide).

[Super_Dave]

Originally Posted by SCOTI

4" rear drop would be shackle & hanger combo (2" drop each). 6" rear drop on leaf trucks can get by w/o a notch (approx. 2" of travel) but your better off w/more clearance. The factory bump-stops will make contact & will need to be removed and/or replaced w/something shorter.

I do think you'll need to go w/shorter springs in the front in addition to the spindles if targeting the 6" rear drop.

Scoti,

Thanks.

I might start with the flip and spindles initially, to see just how radical the rake is and adjust with springs accordingly. I will have the body and paint guy box in a small c-notch, as I don't foresee needing the Full Monte from the after market kits.


On the drop springs, what do you think I might need in conjunction with my wheel/tire setup above and 3" spindles... 1" or 2"? Some rake is fine, just want to avoid the 70's Hijacker Air Shock look

I appreciate it! Now I have some working numbers so I can order parts.

[Super_Dave]

Originally Posted by wilkin250r

Wait, back to the original question. Are you SURE a 245/45/18 will fit on a 18x9 rim? A 9.6" width on a 9 inch rim?

I'll be honest, I haven't dealt with low-profile tires much, but I know that a standard 33x12.5R15 will NOT fit on a 12" rim, the manufacturer specifies 8-10" width.

Unless low-profile tires work radically different, I think your front tires are too narrow (or your wheels are too wide).

Great, complicate my life even more!

Nice catch.

I checked online and the recommended tire is a 295/65 (33"... almost 2" taller than what I have now) yielding an 11.6 width. I think I can squeeze in a 305 @ 12" but will most likely have rubbing issues, so the 285-295 rear tire will probably find their way on the back.

The fronts could go 255-265 bumping the width to 10.4... I will verify with my wheel and tire people tomorrow before heading North to meet with the body and paint people to finalize our dates. Maybe I can cajole them into a test fit to see how it looks and fits. It might even influence my flip and spindle purchase...

[wilkin250r]

Actually, I just looked up the specs on some general 245/45/18 and 285/45/18 tires. I think you're good on both counts, the 245 had a recommended rim width of 7.5-9", and the 285 had a recomended width of 9-10.5", so I think you're at the minimum and maximum of each.

I'd still verify with your tire people, though.