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new wheels coming. full lock clearance question

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doni10

new wheels coming. full lock clearance question

hello everyone,

a quick question for you helpful folk!

was wondering if anyone would be so kind as to please let me know how much clearance there is between the stock wheel/tire (81' F-250) and the suspension at full lock?

am about to order myself some new wheels. -i live in the UK and 16.5" tyres are almost impossible to get. changing to 16" wheels (am thinking 265/75/16 7.5") - and am trying to work out what offset i need.

can't do this myself as the truck currently has no gas tank/carb/battery/all that other good stuff that makes it run, and is parked with the wheels right up against the kurb. - pushing it out the question as well, as it's a 5000lb RV.

Thank you!

1981 F-250 camper, 4.9l inline 6, RWD

Gary Lewis

Re: new wheels coming. full lock clearance question

Administrator

Afternoon! Hope your weather is better than ours here in Okiehoma. It feels like we are on Old Blighty - it is 50F and rainy.

Anyway, let me see if I understand the question. You want to change to 16" wheels, but are planning to change to a larger tire? Otherwise why not go back with the stock offset?

As for measuring, I can't 'cause my F250 has a different front axle and different wheels from stock. But maybe someone else can?

Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

doni10

Re: new wheels coming. full lock clearance question

Hi Gary,
Yeah weather here's actually been pretty beautiful of late, which has been no small mercy, as I've had to put a new roof on the old girl, and have spent the sunshine time doing so!

Yeah, am going for wider tires 265/75 so will ask for the new wheels to be made a bit wider (7.5") to account for the extra rubber.
Have put the new dimensions in a tire calculator and it comes out as being 9.5mm further inboard/outboard, (keeping the original offset). Which i wouldn't imagine to be a problem. However just thought i'd check it's not already really tight in there as otherwise i'd feel like a bit of an idiot splashing out on some expensive rims that don't fit properly.

1981 F-250 camper, 4.9l inline 6, RWD

Gary Lewis

Re: new wheels coming. full lock clearance question

Administrator

It is a good question to ask, for sure. Hopefully someone will come along that knows, soon.

And the weather does look delightful. Glad you had it for that roofing job, which looks like you've done quite well.

Gary, AKA "Gary fellow": Profile

ArdWrknTrk

Re: new wheels coming. full lock clearance question

Administrator

I guess the question is what front axle is in the camper?

I have a D44 HD and the stock 235/85-R16 tires rub the spring savers at full lock.

I'm also really stupid and don't understand the difference between offset and backspacing.
So, maybe someone can dumb it down for me?

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Sac79

Re: new wheels coming. full lock clearance question

Here you go Jim, https://www.wheelfire.com/blog/whats-the-difference-between-offset-and-backspacing/

I still don't understand backspacing, but maybe you can make sense of the article...

Rob

Eddy Myrtle '84 F150 300-6, Offenhauser C series intake, Edelbrock 1404(500cfm manual choke), EFI exhaust manifold, HEI dizzy, custom Painless harness, NP 435, NP 208, D44, 8.8"/3.08, 1.5" leveling coils, 265/75/16 tires.
Toyopet (Daily driver) '86 Toyota Pickup

doni10

Re: new wheels coming. full lock clearance question

In reply to this post by ArdWrknTrk

Hi Jim,

It's a 2WD. So no front axle so to speak.

1981 F-250 camper, 4.9l inline 6, RWD

doni10

Re: new wheels coming. full lock clearance question

In reply to this post by Sac79

thanks. have spent the last two days reading 100 of these! still struggling!
as i understand it, when installing a wider wheel you may have to adjust the offset to push the wheel further out, so as not to foul the suspension when turning.
however what im still not clear on, is in the event that you the extra width doesn't foul anything, do you still need to adjust the offset or is the new setup ok just splitting the extra width 50/50?

-maybe this article will be the charm!

1981 F-250 camper, 4.9l inline 6, RWD

doni10

Re: new wheels coming. full lock clearance question

or maybe just pushing the increased width 'out' is preferable?

1981 F-250 camper, 4.9l inline 6, RWD

ArdWrknTrk

Re: new wheels coming. full lock clearance question

Administrator

In reply to this post by doni10

So you have coil springs.
I don't think you will hit the frame.

Reducing backspace will increase front track width.
With 4x4 it's already wider than the rear.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

ArdWrknTrk

Re: new wheels coming. full lock clearance question

Administrator

I ran the tire size you want for two years.
They rubbed my leaf springs, but never failed.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

ArdWrknTrk

Re: new wheels coming. full lock clearance question

Administrator

In reply to this post by Sac79

So, essentially if the backspacing remains the same, the inside clearance remains the same.
(Given you don't put a much wider tire than the rim is meant for.)

Offset is how far from center the hub face is.
We see extreme examples of this with duallies.

I think the current backspace of your wheels is what to go with (but I already qualify that by admitting my ignorance)

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

old55pete

Re: new wheels coming. full lock clearance question

In reply to this post by doni10

Take one of the wheels off, get the tire off of the rim, lay the rim on a flat surface with the part of the rim that would face out board, facing up. Measure the distance from the flat surface to the in board face of the rim, where it would be against the rotor or drum. That distance is your rim offset for the stock rim.

I hope that helps on one of your questions.

Steve
86 Bronco, XLT, 5.0 EFI, EEC IV, AOD, IFS, limited slip front and rear, 3.08 gears, Tilt steering, factory AC

ArdWrknTrk

Re: new wheels coming. full lock clearance question

Administrator

You don't really need to dismount the tire, if you have a straightedge that's actual rim diameter.
Even a piece of wood will do.

According to the linked tutorial you are measuring *backspace*

Offset is how far from the *center* of the rim the mounting face is.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

old55pete

Re: new wheels coming. full lock clearance question

Sorry Jim, I dident see the video. I was going by what I do to keep the same tire patch on my dirt cars. Like I need a 2 inch "offset in the right front and a 1 inch Offset on the right rear. both to still clear the finder and keep from rubbing the frame and keep the right side tires in line for weight transfure and handling.

Steve
86 Bronco, XLT, 5.0 EFI, EEC IV, AOD, IFS, limited slip front and rear, 3.08 gears, Tilt steering, factory AC

ArdWrknTrk

Re: new wheels coming. full lock clearance question

Administrator

Stagger is something I've never got a handle on.

I know how it works, but I'm not deep enough to have ever used it.

Hats off to dirt track guys!
That's entertainment

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

doni10

Re: new wheels coming. full lock clearance question

In reply to this post by ArdWrknTrk

thanks Jim.
I think you might just be onto something there!...

will be sure to put some pics up once its all done.

1981 F-250 camper, 4.9l inline 6, RWD

ArdWrknTrk

Re: new wheels coming. full lock clearance question

Administrator

The pictographic calculator you use is really intriguing.

By visualizing a section of the new superimposed over the old you could change your frame of reference from vertical to horizontal and then pivot it on the kingpin or ball joint.

If you knew the inclination of the pin or axis of the ball joints you could model it in something as simple as sketchup.
This would show you if it would hit or how close you get to the frame rail.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

old55pete

Re: new wheels coming. full lock clearance question

Jim, Steering axis inclination, now there is a term that is seldom used and even harder to explane to someone that does not have a clue about steering geometry. Good for you.

Steve
86 Bronco, XLT, 5.0 EFI, EEC IV, AOD, IFS, limited slip front and rear, 3.08 gears, Tilt steering, factory AC

ArdWrknTrk

Re: new wheels coming. full lock clearance question

Administrator

Now explain Ackerman and why it's so important on a vehicle driven on tarmac.....

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.