Looking for confirmation before I narrow my 9 inch.

[KYBlueOval]

All the previous posts I've read on cutting a 9 inch rear end down say  they can be cut 3/4 " on each side to allow for wider wheels / larger tires. I have two questions for those of you that have been down this road and made this modification. Mine will be on a Ranchero, with Crown Vic Rear Disc Brakes, and 15 inch wheels IF, that makes a difference.
1) Is the  3/4 cut still the "right amount"  to cut for maximum wheel/tire clearance ?
2) With the 3/4 cut, what width and back spacing,  15 " wheels  can I use and what size 15" tires can I use?  I understand from previous posts that some wheel and tire combinations can be difficult to get in and out of the wheel well, and I can deal with that.
I'm open to any and all suggestions.........only want to do this once, and you y'all know what works and what doesn't.
Thanks
John

[rmk57]

It would depend on how wide of wheel and backspace your planning on using.
Mine has 15x7 steelies with a 4.25 b/s with a 245 m/t street radial and I have
about 3/4" on both sides of the tire. Section width of the tire is 10 1/4".
I did roll the fender lip but it wasn't really nessasary.

Forgot to mention, my rear end housing has not been narrowed.

[John Palmer]

I believe the 3/4" distance comes from not having to re-spline the original axles.  The axles have extra spline length, and the 3/4" comes off the end.  It's all about cost savings.

I would agree the "correct amount", should be determined by the wheel back space, the tire profile, spring clearance, fender clearance, and finally ride height.

[RICH MUISE]

I have to disagree on the cost savings theory. Many who narrow their housings also change the axles. I did when I added the trac-loc and went to new gears and 31 spline axles. Backspace on the wheels is the key. with a 4.25 backspace (7" wheels), I've got 3/4 clearance from the wheel to the springs.....that's why it would have been an issue for me if I went narrower. Also, if you're changing to disc brakes, getting closer to the springs would become an issue as well from an assembly standpoint. So, yes you could go to a 3.5 backspaced wheel on a housing narrowed, say 1 1/4 (I think, lol), but then you'd have the disc brake issue if you're going that route.
In a nutshell, it comes down to what RMK57 said...choose your wheels (and brake system)FIRST, then take their backspacing into consideration when doing the math.

My car has 7" wheels with a 4.25 backspace, and the housing has been narrowed 3/4". I have 3/4 clearance at the leaf springs, and 1 3/8 clearance at the unaltered fender lip. 235 wide tires.
If I'm figuring this correctly, if I changed to an 8" wheel with a 3.5 backspace (torquethrust), I'd now have 1 1/2 clearance at the springs, but the 1 3/8 at the fender lip is now a negative 3/8!! , and that doesn't include any added width tire. I don't know if you could narrow the case another 1" per side. My opinion is definetly not with a disc brake kit anyway.
An 8" wheel with a 4.25 backspace would be better, but I wasn't able to find any I would have considered for my car. Had I been able to find those, I would have considered going to a full inch per side on the narrowing.

[KYBlueOval]

rmk57, John and Rich........thanks for your replies and input.
I plan on using American Racing  15 inch,Torq Thrust "D" Wheels. The 7 inch has a B/S of 3.76  The 8 has a B/S of 4.5 inches. See if I'm thinking correctly......Based on the math that Rich has given ( rear end narrowed by 3/4' ), there is a total of 9 1/8 inches to play with. The width of the wheel, plus the clearances on either side, which change ,based on the Back Spacing of the wheel. The total is still 9 1/8 regardless of the Back Spacing.
rmk57 's math says he is dealing with a total of 8 1/2 inches. The difference between Rich and rmk57's measurements is 5/8", and Rich has his narrowed by 3/4 ".  A 1/8" difference. What's a 1/8 " among friends?
Tell me if in theory, I'm correct in my thinking here..........using the 7 inch wheel with a Back Spacing of 3.76 and a rear end narrowed 3/4 ", I should wind up with 1 1/4 " clearance to the springs and 7/8 clearance to the unaltered fender lip. Totals 9 1/8".
Using the 7 inch wheel with a stock width rear end, the 1 1/4 " clearance between the wheel and the spring, becomes 2.0" as the axle housing moves the wheel further"Out", leaving only 1/8 clearance between the wheel and the unaltered fender lip. Again, it all totals 9 1/8".
I should mention that my frame is on a rotisserie , So I can't measure anything relative to the body.
Am I looking at this correctly? Looks to me that if I want to use these wheels, and I do, it seems to me that the 8" is out and the 7", with the 3.76" Back Spacing, will work, provided, the axle housing is narrowed 3/4" per side.
What did I miss?
Thanks
John

   

[suede57ford]

3/4" per side is the correct amount.

You want to always be able to use off-the shelf offsets when buying wheels.

The common offset for an aftermarket Ford bolt pattern wheel is 8" with 4.5"BS or 7" with 4.25BS".

If you narrow 3/4"-5/8" per side it exactly centers wheels with common offsets in the fender well.

I always recommend rolling the fender-well lip when doing the body work, as every bit of extra width helps.   You never know what size tire/wheel you may want to use in the future.   To roll the lip, hold a bag of led shot(leather glove filled w/shot) on the outside lip and use a dolly or hammer and fold the lip a little each pass until it is flat with the inside fender-well.   This is really only necessary on the part of the fender lip that is closest to the tire which about 22" from the front of the arch and fold it for about 6"-8"after that. No need to fold the rest as that area is the closest part to the tire.

If you try to use the stock dimension, you will always be stuck ordering more expense custom offset wheels and run the risk of rubbing or a wheel you can't get off and on.

The 3/4"-5/8' per side does enable you to remove the wheel more easily.

3/4" to 5/8" is a lot to chop of a stock axle, but will work.  Keep in mind, stock '57 axles are very weak.

I have 20" x 9 1/2" with a 275 width tire on my RanchWagon, and have used 275/60/15 on 15x8 on several other Customs and Fairlanes with these mods.

Be careful with Explorer or other aftermarket brakes, as they can need the axle flange moved out some too. With Explorer brakes, put the Currie Ring on the axle before the bearing or it stick out more yet.

The step-out(Axle flange to hub width) is around 2 1/4" on the original '57 axle and often 2.5" on later ford axles and brakes.  Something to consider as well.

[RICH MUISE]

I think you've got it correct. The 1/8 difference, btw is probably in the fact that my wheel well lips are probably at least that much wider than oem. Both my lower rear quarters were replaced, and the wheel well flanges rebuilt.Since my replacement quarter's flanges were too narrow (less than 1/2"), I butt welded on a strip of metal all the way around the wheel opening, then just eyeballed a good width when I trimmed back.

[jvo]

Whew! Read this thread from the top, and my head was swimming half way through, but?? if 3/4 inch narrowing on each side is the right thing to do, that's all I need to know, as I just finished narrowing mine that amount, based on other posts on this site.  Thanks for the info regardless.

[KYBlueOval]

Thanks suede57ford............you and the others that replied, gave me a lot of very good, useful information. Exactly what I was hoping to get.
jvo........yes my head was swimming as well as  I did the math and pictured in my mind, the various scenarios.
Thanks again
John

[KYBlueOval]

3/4" per side is the correct amount.

You want to always be able to use off-the shelf offsets when buying wheels.

The common offset for an aftermarket Ford bolt pattern wheel is 8" with 4.5"BS or 7" with 4.25BS".

If you narrow 3/4"-5/8" per side it exactly centers wheels with common offsets in the fender well.

I always recommend rolling the fender-well lip when doing the body work, as every bit of extra width helps.   You never know what size tire/wheel you may want to use in the future.   To roll the lip, hold a bag of led shot(leather glove filled w/shot) on the outside lip and use a dolly or hammer and fold the lip a little each pass until it is flat with the inside fender-well.   This is really only necessary on the part of the fender lip that is closest to the tire which about 22" from the front of the arch and fold it for about 6"-8"after that. No need to fold the rest as that area is the closest part to the tire.

If you try to use the stock dimension, you will always be stuck ordering more expense custom offset wheels and run the risk of rubbing or a wheel you can't get off and on.

The 3/4"-5/8' per side does enable you to remove the wheel more easily.

3/4" to 5/8" is a lot to chop of a stock axle, but will work.  Keep in mind, stock '57 axles are very weak.

I have 20" x 9 1/2" with a 275 width tire on my RanchWagon, and have used 275/60/15 on 15x8 on several other Customs and Fairlanes with these mods.

Be careful with Explorer or other aftermarket brakes, as they can need the axle flange moved out some too. With Explorer brakes, put the Currie Ring on the axle before the bearing or it stick out more yet.

The step-out(Axle flange to hub width) is around 2 1/4" on the original '57 axle and often 2.5" on later ford axles and brakes.  Something to consider as well.

suede57ford..........based on your information, I went back to searching for the style wheel I want ( Five Spoke ) and the back spacing you quoted. American Racing does not have the desired Back Spacing. But Haibrand does ,  both 7 and 8  inch wheels with 4.25 BS.  You saved me from making a costly mistake..........thanks
 

[lalessi1]

John,
If you narrow the rear end 3/4" per side then the 15 x 8'" wheels with 4.25" B.S. will work. I have 15 x 7" with 4.25" B.S. on a stock rear end and have at least 1" of clearance using 225/60 tires. You would have 3/4" with the 8" wheels with the narrowed rear (stock brakes).

[KYBlueOval]

Thanks Lynn, exactly the information I'm looking for. But , I'd like to ask this question..........the 1 inch clearance.....is that to the spring side or to the fender side?
BTW Lynn, I installed the SW Thunderbird Sway bar recently on my frame, No body etc, 4 feet off the ground which admittedly makes it much easier to work with it. I welded studs in the "L" Shaped brackets, which in turn allowed me to move the bracket up. Re drilled the mounting holes, and welded up all of the remaining holes. As you pointed out, I had to get a 5 1/2 " bolt for the lower control arm mount. Looks pretty good to me.   
John

[hiball3985]

John, I'm glad the idea of using studs worked. I wish I had thought of that when I installed mine originally. Maybe some day I'll rework it..

[lalessi1]

The 1" clearance I have is to the fender lip. There is a more clearance to the spring. I will measure and take pics.  That clearance is to the tire itself. A change in tire section width changes the clearance clearance by half that change but a change in wheel width does not work that way. For example... if I go to a 235 section tire (from the 225) on my same wheel the fender lip clearance is reduced by 5mm or less than a 1/4".... no problem. If on the other hand the wheel is widened by 10mm.... the clearance at the tire is less than half of that. I am considering using a 15 x 8" wheels with a custom 4.75", maybe 5" B.S (or narrowing the rear end). I think to use tires wider than 235 you should go to a wheel wider than 7".

BTW I can change the rear tires without any changes (no mods) as it sits BUT IT IS TIGHT!

A while back JimNolan had 15 x 8 Wheel Vintiques made with a 5.125" B.S. He was using 10.5 x 26 slicks. That is a 265/50 street equivalent. I think he had a "stock" rear end arrangement.

http://57fordsforever.com/smf/index.php?topic=5645.msg44953#msg44953

[lalessi1]

Pictures of clearance....