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Saggy Rear End...

Greggers

SAOCA Vice President
Platinum Level Sponsor
...Not just me, but my car as well. I've got a conversion outfitted with an 89 Mustang rear end fitted with 89 Mustang 15" wheels. Either the previous owner didn't narrow it or didn't narrow it enough, so on big bumps, the tires rub on the inner lip of the wheel well.

It hasn't been a huge deal, just an occasional fssssht, but things changed recently. Last weekend, the wife and I drove the car and it was all sunshine and roses. But this weekend, I couldn't drive over an expansion joint (or accelerate or go over speed bumps or turn) without getting some sometimes-significant rub. I realized that the difference was that since last weekend, I filled up the tanks. I figure the extra 60lbs. of fuel hanging over the rear end lowered the car enough to make it rub almost constantly (or perhaps the wife needs to lay off the bon bons).

Since it's most likely the fuel thing, what's the best way to get rid of the rub? I figure I've got a few options:

1. Roll the rear quarter's lip
2. Trim 1/8" or so off the lip
3. Have the springs re-arced (where?)
4. Install spring-assisted load-adjusting shocks.

Thoughts from those who've been there?
 

RootesRacer

Donation Time
You missed the easiest option which is to add a helper leaf.

This assumes that there isnt some more ominous reason that you are now dragging your rear.
 

V6 JOSE

Donation Time
Hi Greg,

I recommend number 1 option. I rolled up the inner lip of the fender well and solved all my problems. I took a good sized set of vice pliers, clamped it to the inner lip that sticks into the fender well, then bent up the lip. you only need to do about 8"across the top of the fender arch. Since the inner frnder and outer fender are welded together there, it won't affect or bend the outer fender metal. Do not, and I mean DO NOT do this procedure on the front fender. You will bend the sheet metal of the outer fender.

I don't recommend cutting the lip out, because you will leave a sharp edge still sticking out toward the tire, and it will cut the tire. when you bend it up, and if the tire does touch the fender, it will not cut the tire, just rub against it with no damage, although if you bend it up enough, it will never touch.


...Not just me, but my car as well. I've got a conversion outfitted with an 89 Mustang rear end fitted with 89 Mustang 15" wheels. Either the previous owner didn't narrow it or didn't narrow it enough, so on big bumps, the tires rub on the inner lip of the wheel well.

It hasn't been a huge deal, just an occasional fssssht, but things changed recently. Last weekend, the wife and I drove the car and it was all sunshine and roses. But this weekend, I couldn't drive over an expansion joint (or accelerate or go over speed bumps or turn) without getting some sometimes-significant rub. I realized that the difference was that since last weekend, I filled up the tanks. I figure the extra 60lbs. of fuel hanging over the rear end lowered the car enough to make it rub almost constantly (or perhaps the wife needs to lay off the bon bons).

Since it's most likely the fuel thing, what's the best way to get rid of the rub? I figure I've got a few options:

1. Roll the rear quarter's lip
2. Trim 1/8" or so off the lip
3. Have the springs re-arced (where?)
4. Install spring-assisted load-adjusting shocks.

Thoughts from those who've been there?
 

alpine_64

Donation Time
What width wheels are you running on the rear? I'm guessing 7" and what width and aspect tyres? Both of these add to the issue before we even consider the offset which may have the wheels sitting further to the outside.

I agree with rolling the lip as a good idea, I'd also recommend once done clean it and dry the the valley it leaves and fill with silicone so that dirt and mud can't sit up in there and cause rust.

All that said... It does seem your springs are tired and all these are bandaid solutions that may not be needed if the springs are sorted. If you had good springs and rubbing then rolling is a given.

As a side note there are several suppliers for new and uprated springs for the sunbeam. Mid tiger engineering, dales restos, iirc maybe even vb do stock spec.
 

Greggers

SAOCA Vice President
Platinum Level Sponsor
Just went out to get a better look at things. There appears to be nothing catastrophic going on with the mounts or all that. Also, if the tires weren't there (and I put a ton of weight on the back end), the rear wheel rims would overlap about 1/4" with the rear quarter lip. That's how wide we're talking. The 195/65R15 tires are 15x7 with a 22.4mm offset. The tires have been gouged/scraped/rubbed as low as about halfway down the sidewall.

One thing worth noting is that my rear springs are virtually horizontal, almost no curve whatsoever. The 8.8" rear axle is mounted above the springs. Of course, the axle itself is so huge at the mounting point, I'd have a 1970s rake if they were mounted under the springs.

Attached are some fun photos. They don't tell you a ton, but they're worth looking at, I suppose. In the one I marked "leaning on fin," you can see one of the gouges.
 

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Bill Blue

Platinum Level Sponsor
Greg, step back (literally) and look at the car. Are you happy with the ride level? If you are, I think your problem could best be addressed by changing wheels. Your wheels have 22.4 mm offset, stock Alpine is 32 mm. That pushes the wheels out about 3/8". Your wheels are 7" wide, stock is something like 4 1/2". That moves the sidewalls out over 1" All of this means each tire is sticking out 1 1/2" farther than stock. I'm not saying that stock wheels are the answer, just that the wheel/tire combination could be the problem.

Your wheel/tire combination is also making it hard to steer at low (especially at zero) speed.

Bill
 

alpine_64

Donation Time
As mentioned before and by bill... Your offset is part of the issue... But so are the 195/65/15.... That's a very tall tyre and wheel diameter combo... Combined with your offset.. you would either be narrowing the rear end or flaring lots to stop the rubbing.... Lifting the car to clear will look funny and raise the weight at the rear and likely adversely effect handling.
 

DanR

Diamond Level Sponsor
When I come that way....

Greggers, I can bring one of my Wheels ( 195 55 15's) mounts on the 4 4.25x108 offset from my (Spare) SV Commodore Blue V6 if you want to try....?
 

Greggers

SAOCA Vice President
Platinum Level Sponsor
I don't know about the ride height. Those bigger tires do a better job of filling the wheel wells than the 13" stock-ish combo on my other car. But the idea that adding 60lbs to the boot drops the back end an inch sounds like I have more than a ride height problem.

The other bad news is that the PO ran the exhaust under the x-frame, so there's about 2.5-3" (AKA "some portion of a speed bump") clearance. So if I put on stock wheels and tires, that clearance goes to bottoms-out-when-driving-over-a-nickel.

So it looks like instead of "stick on some new springs," my answer is gonna be:

1. Get new headers
2. Drill holes in the x-frame then weld in pipe
3. Run new exhaust through the holes
4. Stick on some new springs
5. Switch to stock wheels and tires

Or

1. Narrow the rear end (possibly again)

That annoying (and admittedly dangerous) tire rub just got expensive.
 

Chuck Ingram

Donation Time
If the car has headers now I don't see why you would need new ones. Maybe a new collector end. I agree through the frame is the way to,go. Springs can be
Re arched . Possible to,add an extra leaf. Good shop can take care of the springs
Make sure your shocks are good or replaced.
This still,does not take care of tire back spacing or offset. There are lots wheels that fit out there
 

alpine_64

Donation Time
You don't need stock wheels and tyres, you need wheels with appropriate backspacing and more appropriate tyre size. Heaps of guys run 15x7 rears on the cars, most with 195/55/15 or 205/50... Your issue is a combination of wrong offset and tyres ... Perhaps track width... But definitely offset issue.
 

260Alpine

Silver Level Sponsor
I wonder if your axle is wider than stock too. I've seen those wheels on Tigers and Alpines before, and yours seem to stick out more. Tires are too tall.
 

Greggers

SAOCA Vice President
Platinum Level Sponsor
I wonder if your axle is wider than stock too. I've seen those wheels on Tigers and Alpines before, and yours seem to stick out more. Tires are too tall.

I don't know what the track is on an 89 Mustang to know if the previous owner had the axle cut down before installing it (or if it was cut down, by how much). The rear tires are definitely too tall. The front are slightly shorter (which I learned the hard way when I installed the rears on the front and the tires nearly ripped the front valance off).

One thing I've noticed is that though the wheels are 7", they look like the tires would be more comfortable on a 6.5" wheel. So I might be able to go with a lower profile, just not a narrower tire. But again, I can't really explore different wheels and tires until I replace that exhaust.
 

Greggers

SAOCA Vice President
Platinum Level Sponsor
If the car has headers now I don't see why you would need new ones. Maybe a new collector end. I agree through the frame is the way to,go. Springs can be
Re arched . Possible to,add an extra leaf. Good shop can take care of the springs
Make sure your shocks are good or replaced.
This still,does not take care of tire back spacing or offset. There are lots wheels that fit out there

Previous owner (or previous previous owner) just drilled a hole in the side of the greater collector region to change the Jose splayed-out headers into goitered straight-back headers. Exhaust gases have to make a 60* turn. The system is welded front to back, so I'll need to cut the goiters off, then pie cut them to make them straight back, probably having to fill some of the oval hole.
 

Alpine66

Donation Time
Can't find anybody around here that narrows axles. Know of anybody in the ATL who can rearch leaf springs?

I don't know unfortunately, but my guess is the drive shaft place on 41 near mayretta may be able to provide a contact. They've done my last 3 drive shafts.
Come to think of it, that should work for the rear axle contact info too.

Here's the number 770-427-4898
 
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