Anyone increased backspace via machining rims

[ktmorangedart]

'72 Dodge Dart has American Racing Boulevard 17" x 8" front rims. Tires are Nitto NT 555, 245/45 ZR17 95W

The tires rub at dips and hard cornering.

I am considering machining the rims to increase back-spacing by about half an inch in order to move the tires inward and clear the fenders.

I anticipate that because of liability issues the manufacturer would not recommend this procedure.

But I brought a wheel to a veteran machinist who said it might be possible. There is ample material to remove 3/8 " from the inside face of the rim, but that will also remove the half inch or so of space at the bottom of the lug holes that there is for the lug nuts to clamp on to to hold the rim in place. He said it could be possible to bore out the lug holes, thread them, and screw and glue inserts which have the proper step at the bottoms to resume the configuration necessary to bolt the wheels down.

Has anyone ever had any experiece in increasing backspace this way? Or any other way?

The machinist said it would be roughly $ 100.00 per wheel, which is better than $ 500.00 per new wheels and tires.

 

[67Dart273]

???????

I'm jus gonna say................

 

[daredevil]

You said they rub on hard cornering. If you corner hard I wouldnt do it.

 

[swingin408]

Have you cut the fenders ?
I considered this before . then i cut about 1/4-3/8 off my inside fender lip .
For $400 i wouldn't do it .

 

[ktmorangedart]

I can't get enough clearance by rolling or cutting, since the rubber is maybe 1/8 " proud of the fender lip. So a portapower jack could go inside there and swell the fender line a bit, but that might ruin the lines of the car. So I quess I have to eat my mistake of buying the wrong set up front. Note: just because Wheelsforless has a website and people on the phone to say the combination will fit your car, it may not be true. But I will consult an engineer on the machining option in case it actually works, before trying it. I only need two done, so maybe it's the best cost effective option. But thanks everyone (especially Mr. No) for the advice! Unless I get a clear endorsement from a professional, It's new rims and rubber up front, I guess. Or I could cut all four wells and install fender flares, changing the lines and look of the car, taking a chance that would look fine. Plus filling, smoothing, paint, $$$. Looks like I'm cornered, ha ha.

 

[dgibby]

How about a narrower tire? I run 225/45R17 on my 68 dart torsion bars cranked down with no rubbing .

 

[67Dart273]

(especially Mr. No) . Looks like I'm cornered, ha ha.

Sometimes I try to be funny. But I really do feel that machining material off alloy wheels (or any wheel "generally") is a very bad idea

I feel incredibly lucky. I simply lucked out. A Versailles rear axle + early Bullitt wheels fit right in there.

 

[72BBSwinger]

Simply give the alignment a degree of negative camber and as much positive caster as possible.

 

[Daves69]

............. Unless I get a clear endorsement from a professional.....................

You might want to think of your potential liability should a rim fail. Will your insurance cover you? You might seek "clear endorsement" from your carrier as well since I'm sure you will void any manufacture liability.

 

[mguner]

Well, I did cut the welds on some 15X10 white spokes once and move the centers out for a 6.5" back space. Alloy wheels using tapered seat lugs sounds dangerous. If it were the standard old school wheel that used the sleeve type nut and washer I wouldn't worry but this sounds a bit sketchy.

 

[Revhendo]

Are these cast or actual billet wheels? With a billet, you might be able to get away with some depending on the pad thickness. Cast wheels, no way. You would be better off with the proper wheels. Although as suggested, look into adding more camber and caster into your alignment, first.

 

[dano]

This is why I bought custom offset wheels. I agree with the others, your safer not machining them. When you look at custom offset wheels they actually move the center relative to the rim. Hence why a 17x7 would have less "dish" than a 17x9 for example. My car below is on 17x7 front and 17x8 rear. Notice the dish is deeper on the rear? I have LBP fronts and a stock A-body axle and 11" rear drums.

Is your rubbing in the front, rear, both? What is your current brake setup? If you swapped to LBP, then your front offset has changed increasing around 3/8". Same with the rear if you went to wider drums on an 8-3/4 or used a b-body axle.

 

[RedFish]

I can't get enough clearance by rolling or cutting, since the rubber is maybe 1/8 " proud of the fender lip. So a portapower jack could go inside there and swell the fender line a bit, but that might ruin the lines of the car.

To break a wheel would ruin the lines of the car and possibly a whole lot of more valuable stuff.

 

[tomswheels]

Is your hub preventing the wheel from moving in further? I simply used a wood lathe to turn my hub down so the wheel fits further in. Much safer and cheaper?

 

[ktmorangedart]

First of all, I want to thank everyone for all the excellent advice in response to my post. I fully agree that my initial inclination of milling the backspace was trashbin material.

And I especially admired the suggestion of turning down of the hub on the wood lathe, unfortunately I am woefully unskilled in such an operation.

However I have had great experience with the common crowbar, an under-rated implement, in my opinion. And only one minor fender malformation to report too!

Here's what happened.

First, I braced the outer fender lips, respectively in turn, against solid wood, anchored against my concrete carport walls. Then I hacksawed several vertical slits six inches apart or so along the inside beveled edges. I heatgunned and rubber malletted them down in no time flat, really flat, then I took my trusty grinder and shaved them down further, and cheated a few milimeters off the inside redius edges too. Self etching primer from the inside out, finished it off.

Then I went crowbar on them from the outside. I swelled them out gradually with a multitude of measured quarter inch apart pulls, using a wooden bock against the inner fender as a fulcrum. The driver side went perfect, but, inflated with arrogance, I kind of overdid the passenger side and put a small wow above the wheel, plus a bit of a ripple on the lip.

But I don't care, I fixed it myself, and all it cost me was three days after work underneath and over the car. Besides, the fenders needed repainting anyway, and good fibreglass filler is made right here in North America, so it will stay authentic.

Finally, I took the car down the worst bumpy, dippy, and twisty (good) roads and met with Great Success! Zero rubbing. Now the car handles like an Italian sportscar with those four sticky low profile Nittos riding on seventeen by eights all round. And I keep my fifth for a spare.

Though I don't think anyone would want to see the start of a crowbar thread.

I'm not saying that I did it right or the best way, intellectually speaking, but it sure felt good pounding, grinding and bending with my hands and basic tools into submission the steel that was trying to eat my tires. Now I can rip around in this awsome Dart and I'm happy about that.