Anybody good at math...?

If you are, feel free to figure this one out for me, because it's giving me one hell of a headache :

Stock Explorer rim backspacing: 4.5"
Mustang Bullitt backspacing: 5.72"
New rims that I'm dying to put on: 6.1"

Bullitts: 17x8" wide
New rims: 20x8.5" wide

Once upon a time, I ran 285/60r17's on my Bullitts and they not only rubbed EVERYwhere, but were dangerously close to hitting the upper ball joints... so I had to step down a few tire sizes to a 255/60r17, which only rubbed a little on the swaybars (that I can live with!).

Bullitt tires: 285/60r17- 11.2" wide
30.5" tall
6.7" sidewall

New tires: 265/50r20- 10.4" wide
30.4" tall
5.2" sidewall

I HAVE to run spacers with the new rims as their center holes will not clear my 2wd spindles. The question is: How much of a spacer do I need?

 

[kabukie]

i went with 1.25 up front and 2 in the rears. this offset the front wheels enough to clear the spindles and prevent rubbing with 275/60/17.

 

[Dignan]

Ok, I'll take a shot, but keep in mind I've been wrong before. Its rare, but it happens, so seek a second opinion. Especially since I'm no tire expert, I'm just going to think through this as a math equation.

So, I am going to use the Bullitts with 255/60/17 as a baseline, as you said that rubbing you could deal with.

The 255/60/17s are 29"x10" so the new tires are not much taller and I assume you're not worried about that, just the width. That gives us an extra .4" based on what you said the new tire size will be. So assuming half of that falls on each side of the tire, we need to move it out .2" to put it at the same rubbing as before.

Now lets think about those rims. Bullets have .38" less of backspacing on a wheel that is .5" smaller. So, if we add half to each side again, that gives us and extra .63" (.38 + .25)

So, in my un-educated opinion, the wheel need to move out .63" and then to account for a wider tire, it needs to move out an additional .2" for a total of .83".

How far out did the Bullitts with 255s stick out? cause this is going to stick out a ways too, I can try to figure that out if you'd like.

Now, I didn't take into account the shorter side wall or anything else, so I might be totally off. Hope this has helped a little.

 

[Spas]

Ok, I'll take a shot, but keep in mind I've been wrong before. Its rare, but it happens, so seek a second opinion. Especially since I'm no tire expert, I'm just going to think through this as a math equation.

So, I am going to use the Bullitts with 255/60/17 as a baseline, as you said that rubbing you could deal with.

The 255/60/17s are 29"x10" so the new tires are not much taller and I assume you're not worried about that, just the width. That gives us an extra .4" based on what you said the new tire size will be. So assuming half of that falls on each side of the tire, we need to move it out .2" to put it at the same rubbing as before.

Now lets think about those rims. Bullets have .38" less of backspacing on a wheel that is .5" smaller. So, if we add half to each side again, that gives us and extra .63" (.38 + .25)

So, in my un-educated opinion, the wheel need to move out .63" and then to account for a wider tire, it needs to move out an additional .2" for a total of .83".

How far out did the Bullitts with 255s stick out? cause this is going to stick out a ways too, I can try to figure that out if you'd like.

Now, I didn't take into account the shorter side wall or anything else, so I might be totally off. Hope this has helped a little.

Thank you Dignan, that sounds pretty logical (to me at least... I flunked math a few times in High School, ask my checkbook ). The new rims won't fit over the 2wd spindles, so I put a cheap 1/2" spacer on just to see where they'd sit and wasn't happy with the results... Being that they're 20's, it's now the edge of the RIM that's close to the upper ball joint instead of the inner sidewall of the tire. So I really need to look into at very least a 3/4" (.75) spacer, but more realistically a 1"?

Anyone ever had issues with front spacers and weird steering?

Btw, when I realized my Bullitts would no longer clear the 2wd spindles after removing the 4wd, I ran 1.25" spacers up front. Not only was steering scary as hell, but it only brought the tires out to the very edge of the fender flares and it looked good, so I'm not worried about how far these new rims end up sticking out I will probably end up running the 1.25's in the rear to clear the 20x10's, though. Either that or hammer in the inner fenderwells )

 

[Dignan]

I don't know about the spacers and steering, perhaps you should just do a SAS with a full width Dana 44, and lift it about 6 inches and take it to moab.

 

[Spas]

I don't know about the spacers and steering, perhaps you should just do a SAS with a full width Dana 44, and lift it about 6 inches and take it to moab.

:

Naw, I've got a perfectly good one of those already... it just has a few dings and dents though

 

[Spas]

Okay, I put the new rims on today and did some mocking up... Granted, sidewall bulges out when under pressure from the truck's weight on it, but how much? 5.2" of sidewall is going to be about 1.2" too much, I think.

This is with the rim spaced 1/2" from the mounting surface on the rotor:

Pardon my dirtiness, I've been too preoccupied with Blackjack's older brother to give him a proper bath lately These pictures are with the front end jacked up by the A-Arms, so full weight is still on the suspension.

Top of the wheelwell:

front:

rear:

 

[Spas]

Anybody have the specs for an Explorer 2wd front lug stud? I know they're 1/2", but I don't know overall length or thread dimensions. It's kind of tough to find 10 extended ones without knowing that





Btw, I mounted my 255/50 & 294/45's today and put them on the truck to see how much spacer I need.. 1/2" for the front is perfect (gives me over an inch between the tire and the upper ball joint, woohoo!) and I'm going to use my old 1.25" ones for the back to A) clear the emergency brake cable and B) bring the edge of the rims flush with the fender flares. They look DAMN GOOD Anybody running 10" wide rear rims with semi-lo pro tires should definitely go with a 305 series, though: I'm wishing mine were even wider already

 

[FROADER]

YES!! Let's see the pics!!

 

[Spas]

YES!! Let's see the pics!!

I'll send them to you, dear, but I'm not putting them up for the rest of the world until Carlisle

Our computers tell me that a 2wd 98 Explorer's front wheel studs are 1/2" x 20mm x 1 29/32 (yes, that's how they measure ), with a .594 knurl. And they're press-in. Love my job

 

[FROADER]

I'll send them to you, dear, but I'm not putting them up for the rest of the world until Carlisle

FROADER ->

<- Spas

Those things look SAAWEEEEETT!! Perfect match!

 

[Spas]

FROADER ->

<- Spas

Those things look SAAWEEEEETT!! Perfect match!

Thanka yew

That's with the 1.25" spacers on the back, too. BLANG BLANG, son!!

 

[FROADER]

Oohh, that second pic is even better! I never realized you had a freckle there... :

 

[Spas]

Oohh, that second pic is even better! I never realized you had a freckle there... :

Oh wait.. which one did I send you? :shifty_ey


LMAO

 

[Spas]

Welp, I FINALLY got my 1/2" billet spacers from Meyers Machine on the RRORC boards.. For $30 I can't be too disappointed, but it's a letdown that the center hole is too small by something silly like 33,000th of an inch so I can't get them to sit perfectly flat on the rotor hats They're at a local machine shop right now, hopefully to be fixed by tomorrow. I still have to order lug studs, but the only size I can find are 3" long... I think, at most, I only need 2.5. Ah well, if they're too long I'll just have to cut them down :

Here's a pic of the upper ball joint clearance with the tires on, I'm pretty happy with how it's turning out!

Hard to see here, but the 1.25" rear spacers barely allow the tire to clear the E-brake cable

Gah! Just a few more days and I'll have these suckers on FINALLY!!!!!

 

[Premier]

Oh wait.. which one did I send you? :shifty_ey


LMAO

hahaha

 

[Dignan]

I'm still waiting for pictures. :scratch:

 

[Lt.Jim]

I'm still waiting for pictures. :scratch:

http://www.explorerforum.com/forums/showthread.php?t=49754&page=7

 

[Dignan]

Thanks for the link. That looks very nice. Good work.