Rear Disc and Rims Offsets

TripleYellow · Nov 11, 2025

I'm looking for some advice on a rear disc conversion and wheels. The car isn't a race car or a powerhouse. I only beat around town and drive it to shows. The mantra of this build is I think it looks good, sounds good, and drives well. I drive it like an old lady. With that in mind, I want to convert the rear to disc brakes. I only want to do it because I love the look of a yellow car with some big red calipers and the cross drilled and slotted rotors.

Currently the car has the LMR 5 lug kit. It's got some American Muscle Bullitt style wheels. There are spacers on the front to keep the center caps from popping out. The wheels are over 10 years old and show it. I need new rims.

I know the rear disc conversion is intertwined with the wheel selection. Offsets, backspacing, SN95 vs Fox length axels, cobra vs SN95 brakes, etc. I've read a bunch of threads but I'm still not sure exactly what I should do. So, what do you think? What would you do? I'm not too concerned with budget. I could buy it all new. I know LMR makes some kits. The only parts I currently have are a set of 94-95 spindles and a 93 cobra MC and booster. I got a good deal on both.

For the rims I'll probably buy the same ones again, but I'm curious what other wheels you guys think might look good?

AeroCoupe · Nov 11, 2025

Cobra or Mach 1 brakes.

nickyb · Nov 11, 2025

Ditto on the cobra brakes, I did them and I drive the outta mine.
Rims are up to your taste not mine. I went with a used set of 2000 GT premium 17 inch rims as they were the closest to Pony rims at that time and price was right.

Mustang5L5 · Nov 11, 2025

Ditto on the Cobra brakes. Plentiful parts, and you can grab replacement rotors and hardware at pretty much any local parts store. More than enough brake for the average Foxbody driver, especially on a cruiser/daily type setup.

Out back, you will likely want to do fox offset axles with the offset caliper brackets, but ultimately that depends on what wheel you pick.

See this thread for more info/questions

Thread 'Ultimate 5-lug swap thread - new/updated'

Jul 21, 2022

This thread is a work in progress. I've unlocked the thread for feedback and questions and if i've missed something or need to correct. I'm still adding/editing.

Wanted to make a new thread to replace the old thread which has info scattered around in many posts. Hoping to consolidate this down and make it more simple. Please limit this thread to discussion on the 5-lug swap, and any issues due to the swap, and not mechanical issues concerning brakes.

Table of Contents

Post#/Topic

General Overview/contents (this post)
Fox spindle 5-lug swap rotors...

But if you are into just looks, slap some X-drilled rotors on, paint the calipers red and call it a day. Car stops pretty good too

TripleYellow · Nov 12, 2025

Cool, so follow the 94-98/99-04 Cobra brakes section of the Ultimate 5 Lug swap. I had seen the thread just wasn't sure which direction to go. For the axles how do you know which you should use based on the offset and backspacing of the rim? Right now, the front stick out farther than the back but I have the spacers on the front. I don't know what happens when I switch the front spindle.

Let's, assume I go with the same wheel. Should it be 17x8. or 17x9 I'm not sure what I got because I bought them off of my brother's car 10 years ago.

AeroCoupe · Nov 12, 2025

I run 17x8 up front and 17x9 in the rear. 245/40 up front and 275/40 in the rear. Offset on my rear wheels is for the SN95 axles but I have ABS so I need the SN95 axles with exciter rings.

Mustang5L5 · Nov 12, 2025

You'll have to find out the specs. There is likely an offset stamped on the back of one of those spokes.

If it's a 17x8 it's likely +30 and would work well with the SN95 axles. If they are 9" wide wheels they are likely +22-24 so would work better with fox offset axles.

I actually had 18x9 +35 offset wheels and needed to run the SN95 axles for that to work. +30-35 offset the more you'll want to lean towards SN95 axles. 20-25 offset and you'll want fox lenght axles.

nickyb · Nov 12, 2025

I used 95 front spindles , 17x8 rims 245/45 on all four corners.
I use fox length five lug axles that fit the cobra rear rotors hole.
Nothing sticks out.

TripleYellow · Nov 13, 2025

nickyb said:
I used 95 front spindles , 17x8 rims 245/45 on all four corners.
I use fox length five lug axles that fit the cobra rear rotors hole.
Nothing sticks out.

This was my original thought too. But I am wondering how big I can go in back without having to change anything?

AeroCoupe said:
I run 17x8 up front and 17x9 in the rear. 245/40 up front and 275/40 in the rear. Offset on my rear wheels is for the SN95 axles but I have ABS so I need the SN95 axles with exciter rings.

Any reason you went with 245/40's up front instead of 45's? Any rubbing? I ask because I have an 88 and I know at some point the front fenders changed. I don't know if that will cause me any issues.

Mustang5L5 · Nov 13, 2025

I did 235/45/17 up front on mine. Slightly smaller diameter. Same with the 245/40/17. Even more reduced diameter, but more rubber on the ground. With larger brakes more contact patch is better. But, you may need to put some rack limiters on as you may rub on the inner fenders

AeroCoupe · Nov 13, 2025

Because my cars are in the weeds. Full coil overs and I like them low.

TripleYellow · Nov 17, 2025

So, I talked to my cousin who also has an 88'. He's running 17x9 all around with 255/40 in the front and 275/40 on the rear. No rubbing, no fender modifications.

TripleYellow · Nov 17, 2025

I also got the AI to work up some alternative wheels. I thought it was pretty cool this could even be done. By the end, it turned my headlights on and made my grille look like an LX

FR500

Ponies

Saleen SC black and yellow

TripleYellow · Dec 20, 2025

Mustang5L5 said:
If it's a 17x8 it's likely +30 and would work well with the SN95 axles. If they are 9" wide wheels they are likely +22-24 so would work better with fox offset axles.

I think I'm missing something. If the 94-95 spindles don't increase the front track width and I have fox length rear axles, then put 17x8 all around with a 30 mm offset, why would the back wheels appear tucked in?

I would think the same would be true if I went with a 17x9 all around with a 24mm offset. The back would still appear tucked in?

What would happen with 17x8 30mm up front and 17x9 24mm in the back?

AeroCoupe · Dec 20, 2025

1979-93 Mustang: Swapping to the 1994-04 Spindles

1994-95 spindles will increase the front track width by 0.120" (3.1mm) per side.
1996-04 spindles will increase the front track width by 0.320" (8.1mm) per side.

Mustang5L5 · Dec 20, 2025

TripleYellow said:
I think I'm missing something. If the 94-95 spindles don't increase the front track width and I have fox length rear axles, then put 17x8 all around with a 30 mm offset, why would the back wheels appear tucked in?

I would think the same would be true if I went with a 17x9 all around with a 24mm offset. The back would still appear tucked in?

What would happen with 17x8 30mm up front and 17x9 24mm in the back?

I was talking specifically in the rear. But front track width did change due to different k-members and such, but I’d don’t have the numbers off hand.

SN95 spindles up front do push the front wheels up as shown above.

But in the rear…

17x8 +30 on fox lenght axles 255/45/17 tires. It’s a very noticable sunken in look

Same wheels on SN95 axles. Wheel fills out the rear better, but with 255 it’s pretty close to fender lips when suspension articulates so could need to roll depending on tire width.

TripleYellow · Dec 20, 2025

So I did a little bit of math. Using 17x8 +30 as a base line, with SN95 axles it's .75" ~ 19mm wider than a fox.

Then using this calculator: https://www.1010tires.com/Tools/Wheel-Offset-Calculator#
it says that going from 17x8 +30 to 17x9 +24 equates to a +19mm change of the outside edge of the wheel. So, running 17x9 +24 with fox axles should look the same as running 17x8 +30 with SN95 axles. Does that sound about right to you guys?

KRUISR · Dec 21, 2025

18x9 with a +24 offset, 275 tire with a 8mm spacer on fox length axles and rolled fenders

Not related to your specific query but I was playing around with an extra set of rims I have ...

Torq Thrust II - 17x11, +27 offset. Same axle and spacer (spacer needed to clear inside of wheel well).

Without spacer

I have a pair of matching 17x9.5 for the front as well. To be used on a future project.

AeroCoupe · Dec 21, 2025

Rear wheels on my Coupe are 17x9 with a +45mm offset. Used a 1/4" spacer to keep them from rubbing on the inside frame rail when cornering hard. I don't think I would need it if I did not have a panhard bar as the body rolls different with it. Car has a Fox 8.8 housing with SN95 length axles, Cobra brakes, and 275/40R17 Nitto 555R II's.

Fronts are 17x8 with a +35mm offset no spacers and have zero rub. Tires are 245/40R17 Dunlop Direzza ZIII's and I am running 96+ spindles with a Maximum Motorsports k-member, zero offset Fox control arms, MM caster camber plates and coil overs. I don't think I would try any wider of a tire as its pretty close to the inner frame rail and I do not want to run rack limiters.

TripleYellow · Jan 9, 2026

I managed to snag a 17" cobra spare. $100 at a local-ish junk yard. That's one problem down. I was still rocking the factory 4 lug.

It's a very tight fit with all the sound deadening. The insulation ripped a bit while pushing it down, but it looks flush.

Rear Disc and Rims Offsets

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I gotta say i never painted my nuts, Never Ever

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Attachments

lube between the nut and the face. I know my lubes

That is…until I whipped out my Bissell

I gotta say i never painted my nuts, Never Ever

Active Member

That is…until I whipped out my Bissell

lube between the nut and the face. I know my lubes

Active Member

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lube between the nut and the face. I know my lubes

That is…until I whipped out my Bissell

Active Member

lube between the nut and the face. I know my lubes

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