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Discussion Starter #1
73 hatchback
disc brake conversion pushed out the fronts 1/2" each side. I have ben having a %&&^% of a hard time getting fender clearance. Specifically the bump out / fender support directly above the tire. I was sure I had good clearance with some 205/55/17 tires but roadtest was unsat. When going over a speed bump at moderate speed both outer tires rub. when turning more then 20 degress with any down angle the outer tire rubs. It does not appear to rub on the fender, but at the top behind it.
All new steering and suspension, correct 350 springs.
In a panic stop the outer tires will rub on the sidewall/ edge of tread.

I am entertaining the Heat and beat method of creating some clearance, but before I do I thought about adding negative chamber. ( top of tire in) Maybe a combination of the two.

So ? is what's the MAX neg chamber One might explore in this situation. ? not what the specs are( 0.5N to 1.0 pos preferred is 0.75P) but how much before it becomes an actual problem.
some neg chamber would improve cornering without increasing inner tire wear.

A lot would look stupid and could lead to other steering issues.

I have the shims, I'm probably going to add an equal amount to all 4 positons, check tow in and go from there.

Anyone else have experience with this?

any advice / smart azz comments welcome.
 

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well i wouldn't try to fudge the alignment to fix the rub. i put disks on the front of my 66 an it moved the rims out a 1/2-5/8'' an it rubbed at every turn. the ralleys were 3 3/4'' bs so i found 4 3/8'' bs ralleys. problem solved. now i can turn lock to lock with no rub. final wheel an tire is 205 70 14 on a 14 x 6 with a BS of 4 3/8''.
 

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Mike - 74 Nova Baltimore, MD
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I know it might be a little late since you already have wheels... but I think your back spacing on your front wheels (or lack of it) is what is causing your tire clearance issues.

On my 74 Nova with front disc brakes & stock small block front springs, I run a 225/55/16 tire on 7" wide wheels with 4.25" back spacing. No rubbing to the inner or outer fenders at all (full turning, bumps, aggressive driving, etc).

Anyway... I have neg .5° camber on both front tires with excellent tire wear.
I have read that you can run up to neg 1° of camber on your front tires and still maintain fairly decent tire wear. Adding more neg camber is going to increase tire wear.
 

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Discussion Starter #5 (Edited)
I know it might be a little late since you already have wheels... but I think your back spacing on your front wheels (or lack of it) is what is causing your tire clearance issues.

On my 74 Nova with front disc brakes & stock small block front springs, I run a 225/55/16 tire on 7" wide wheels with 4.25" back spacing. No rubbing to the inner or outer fenders at all (full turning, bumps, aggressive driving, etc).

Anyway... I have neg .5° camber on both front tires with excellent tire wear.
I have read that you can run up to neg 1° of camber on your front tires and still maintain fairly decent tire wear. Adding more neg camber is going to increase tire wear.
Thanks to all who replied.

Rif,

Yep, 8" wheel, 0 backspacing. Lesson learned about trusting others.....Again.

Just trying to work with what I have . they sure look awesome.

I think Ill wipe some grease on the sidewalls, and some in the back of the wheel well in case the tread is rubbing there, go for a ride and see where its rubbing and go from there.
I think its only rubbing on the boss on the top of the fender well, not on the fender lip. Now I know why people want to cut out the extended portion (boss?).

Looking more and more like heat n beat and drop some shims in....some , but not to much of each. I have already replaced most of the bolts with screws to gain some clearance.

Shims are in the box they came in.

Fridge is stocked


BMFH is on standby.

Torch is ready to fire up, fire extinguisher is handy.
 

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Discussion Starter #6
Before I took out a hammer I might try a bat rolling between the tire and fender.:rolleyes:
Thanks for responding
I have access to a fender roller, but its not the fender, its the bump out behind the fender... but a bat may help.....
 

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Mike - 74 Nova Baltimore, MD
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Yep, 8" wheel, 0 backspacing.
I think you may have meant 0 "offset". An 8" wide wheel with 0 offset would equal about a 4.5" backspacing.

73 hatchback
disc brake conversion pushed out the fronts 1/2" each side.
After re-reading your first post, I'm starting to think that the current front wheels are not the problem... but it is the additional 1/2" pushed out due to the front disc brake conversion. A 1/2" of movement seems like a lot.

Based on what I am looking at on my 74 Nova with the original factory front disc brakes (with the original factory spindles) and stock lower control arms, an 8" wide wheel with a 4.5" backspace using a 205 wide tire should fit without rubbing the inner or outer portion of the front fender skirts (wheel wells).

What kind of kit (or types of parts) did you use for your front disc brake conversion?
Did you also change the front lower control arms from stock?... as that could also effect where the front spindles are located.
 

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Discussion Starter #8
I think you may have meant 0 "offset". An 8" wide wheel with 0 offset would equal about a 4.5" backspacing.



After re-reading your first post, I'm starting to think that the current front wheels are not the problem... but it is the additional 1/2" pushed out due to the front disc brake conversion. A 1/2" of movement seems like a lot.

Based on what I am looking at on my 74 Nova with the original factory front disc brakes (with the original factory spindles) and stock lower control arms, an 8" wide wheel with a 4.5" backspace using a 205 wide tire should fit without rubbing the inner or outer portion of the front fender skirts (wheel wells).

What kind of kit (or types of parts) did you use for your front disc brake conversion?
Did you also change the front lower control arms from stock?... as that could also effect where the front spindles are located.
Yes 0 offset.

right Stuff brakes. PO installed. I called them and they told me the fronts are from a 69 Chevelle and the spindles/ discs push out the wheel 1/2" per side.
I think the tire would clear with a 7" rim.

I replaced all the control arms with tubular last winter. Stock dimensions.

The tire appears to be rubbing on the sidewall when the tire goes up into the wheel well. I will rub grease on the sidewall and drive the car and see where it transfers to.

Thanks for taking the time to think about my issue!
 

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Mike - 74 Nova Baltimore, MD
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I just read some other posts about this same issue (tires rubbing) after converting front drum brakes to discs using an aftermarket kit.

I did read the article in the link below... but the narrower disc brake hubs can only be installed as part of a kit.
http://www.superchevy.com/how-to/brakes/1811-curing-tire-wheel-fitment-problems-narrow-disc-brakes/
I know this may not help you at this point, but this information could be useful to others thinking about performing a drum to disc brake conversion.

Hopefully, your tire rubbing issue is minor and can be solved with some slight "massaging" of the inner fenders.

Note: If you went to a 7" wide wheel that still had 0mm offset, it would not change the position/clearance of the same tire on your current 8" wide wheel with 0mm offset when mounted onto the disc brake hub. You would need to find a wheel that provided you with some positive offset to gain tire clearance from the outer portion of the wheel well.
 

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Discussion Starter #11 (Edited)
I just read some other posts about this same issue (tires rubbing) after converting front drum brakes to discs using an aftermarket kit.

I did read the article in the link below... but the narrower disc brake hubs can only be installed as part of a kit.
http://www.superchevy.com/how-to/brakes/1811-curing-tire-wheel-fitment-problems-narrow-disc-brakes/
I know this may not help you at this point, but this information could be useful to others thinking about performing a drum to disc brake conversion.

Hopefully, your tire rubbing issue is minor and can be solved with some slight "massaging" of the inner fenders.

Note: If you went to a 7" wide wheel that still had 0mm offset, it would not change the position/clearance of the same tire on your current 8" wide wheel with 0mm offset when mounted onto the disc brake hub. You would need to find a wheel that provided you with some positive offset to gain tire clearance from the outer portion of the wheel well.
I think a 7" wheel with 0 offset actually would work, although offset would be desired:
This 205 MM tire ( as measured at its widest point- the sidewall, which is whre its rubbing, not the contract patch) is stretched out to be mounted on the 8" rim. With a 7" rim 0 offset It would actually mount 1/2" narrower.
Of coarse am trying to work with the 8" rim I have, a 205mm is right at the edge of what can be mounted.
I actually just ordered tire calipers and a camber measuring tool as tie issues come up in my other fun vehicles.

I should be all set by Monday..... Sure
 

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Mike - 74 Nova Baltimore, MD
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Yes. A 7" wide wheel with 0 offset is going to sit 1/2" narrower to the outside of the fender and also 1/2" narrower to the inside of the frame... but I think the tire will be sitting in the exact same position.

I believe that all you would be doing is narrowing the portion of the tire that mounts to the wheel and I think the tire's sidewall and tread width would remain the same width.

I understand what you are trying to say. I'm just not sure that your current tire's section width is going to narrow by mounting them on a 7" wide wheel with the same offset... but I could be wrong.

Try out the "Wheel & Tire Calculators" shown in the links below.
https://www.wheel-size.com/calc/
https://www.rimsntires.com/specspro.jsp

You would need about 12-13mm of positive offset to gain 1/2" of Tire to Fender clearance.
 

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Discussion Starter #13
Yes. A 7" wide wheel with 0 offset is going to sit 1/2" narrower to the outside of the fender and also 1/2" narrower to the inside of the frame... but I think the tire will be sitting in the exact same position.

I believe that all you would be doing is narrowing the portion of the tire that mounts to the wheel and I think the tire's sidewall and tread width would remain the same width.

I understand what you are trying to say. I'm just not sure that your current tire's section width is going to narrow by mounting them on a 7" wide wheel with the same offset... but I could be wrong.

Try out the "Wheel & Tire Calculators" shown in the links below.
https://www.wheel-size.com/calc/
https://www.rimsntires.com/specspro.jsp

You would need about 12-13mm of positive offset to gain 1/2" of Tire to Fender clearance.
If I had to purchase new wheels, which I was prepared to do before we decided to try the 205 tire, I defiantly would get them made to fit, with proper offset. That was what I was resigned to doing($$$) when I went to carworx. In fact I was just hoping to get front wheels that would closely match the rears.

I didn't mean to state that a 7" wheel with 0 offset was the fix, I just think, in this case, when I look at how the 205 is stretched out to the 8" rim, It would "work."

I had fun yesterday with shims and hammers and chisels. Ill post up in a bit.
 

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Discussion Starter #14 (Edited)
In order to see where the tires were rubbing I needed something that would transfer from the tire to the metal. Something that would clean up well and not mess up the tire. I wanted to use some latex paint but didn't have any handy so I used some bearing grease. I smeared a bunch on the sidewall only, none on tread. I did smear some on the back of the wheel well, JIC it was rubbing there. Then drove the car in a local area that has speed bumps corners, downhill sharp corners etc.

Upon return I could see where the grease had ben removed from the tires. I removed the front tires and then could see up inside the wheel well exactly where the grease had transferred.
4th pic is from the inside top of the wheel well. I had previously replaced the big bolt head 5/16 NC screw with the counter sunk SS one. the tire was rubbing on the edge of the bolt and the two raised areas inherent in the sheet metal.
Long term plan when the fenders get replaced Ill have them make adjustments to allow fro more clearance in this area.
 

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Discussion Starter #15 (Edited)
By looking at the two indicators, ( none of the grease in the wheel well back transferred so no issue there) where the grease went and where it was removed from the tires I figured needed about 5/16" additional clearance.
As I had stated earlier I had loose plan to add some neg camber and heat n beat the wheel well. Heat and beat the wheel well is going to be difficult with the wheel well in place, I would really to remove the wheel well and need a weighted lead bag and some rounded hammers to stretch the metal out. But I may be able to gain just a bit should I need to.
so how much camber to add? and how to keep track? Here's what I came up with:
I lifted the car up 2 feet and lowered it onto the first mechanical stops.
I measured from the center of the wheel (bearing cap as tired were off) to the floor= 19"
with a 26" tire its 13" to the floor from center. Next I used a straight edge and marked the floor in two points then drew a line connecting the two for a starting point.

The tire was rubbing at about 12" from the center, so I knew that whatever movement I got at 19" from center( as measured on the floor) would be more than what was actually at the tire. about 65%. 12 divided by 19=63(%)

Hmmm..... work list item added: clean up and paint the rotors.
 

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Discussion Starter #16 (Edited)
Next I used my floor jack to push up on the LCA to help push the UCA in.
Then I loosened the two connectors using a 11/16 wrench. PITA as I couldn't get a socket in there. I obviously NEED a hollow ratchet and sockets.
Then I used a two lb sledge and a wide mortar chisel with a thin blade to separate the UCA from the mount. It was the only thing I had thin enough to get the UCA started. Unfortunately this messed up the mount some. I should have inspected the chisel and cleaned it up before using it.
Then I dropped a 1/8" shim at both points.
 

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Discussion Starter #17 (Edited)
I removed the floor jack and used the straight edge from the rotor to the floor mark the floor again. Keeping track as I did may have ben completely unnecessary for what I was trying to accomplish, but I do try to be methodical and wanted some type of gauge to keep track. I also placed a block against the top of the tire and the fender flare to compare the movement. Both showed about the same before and after difference, about 5/16". Pretty close to the estimated 1/4" I thought was needed. I also compared the PS fender measurement to the DS( before any adjustments were made to the DS) , not that that was particularly accurate, but it showed a significant and encouraging difference as well.

Pictures 3 and 4 are of the tires after the test drive.
 

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Discussion Starter #18 (Edited)
Repeat for DS wheel.

I ordered a camber gauge so I can present the actual amount of Neg camber.

Test drive sat: Very light rubbing while turning at down angle, or when hitting a bump while doing the same. less rubbing then I had with the 15" wheels. No rubbing when going rapidly from L-R .
Car handled great, no over/ under steer, nor did it feel like it was being pulled into road moguls, depressions etc. Steering is great. no rubbing when going over speed hump at 25 MPH.

Went on highway handled fine.

Again, I'm not advertising this as the correct way to overcome tire rub, nor am I stating this is the best way to go. The best way t go is with proper fitting wheels and tires. I chose to do this based on my particular circumstance. Although I have added a minimum amount of Neg camber( and may possibly add bit more if conditions change), one of the distractors is premature tire wear.

Came home washed car and started planning the next five or so items on the worklist.

Well, 6 actually...I neglected to check the toe in after I messed with the camber.... Its probably not effected, I just want to be sure.
 

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What spindles do you have.. Right Stuff, stock, dropped..?
Is the disc rotor causing the problem or are the spindles part of the kit contributing to the problem..?
Is your car lowered or stock height..?
Do you have a picture of the car as it sits with its current wheels, tires, brakes, and suspension setup?

If the Right Stuff is really the Wrong Stuff why would you want to sacrifice your other aspects of the car like sheet metal and alignment to accommodate the WRONG disc brake kit..?

Something to keep in mind regarding the suspension geometry of this era with GM suspensions is the poor camber characteristic that GM purposefully designed into the suspensions..

When the suspension compresses the top of the wheel cambers out positive towards the fender.. This problem can be addressed in a couple of different ways which will improve the handling of the car overall..

The Guldstrand modification is one method to address the problem. Tall camber correcting spindles are another way to get better negative camber gain..

Stacks of shims is really not the proper solution here.. At a stationary static ride height with stacks of additional shims you might be able to achieve a couple of degrees of negative camber but once the vehicle is in motion and the suspension cycles up the top of the wheel will camber outward towards the fender...
 

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Mike - 74 Nova Baltimore, MD
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I know that you are trying to fix the tire rubbing issue on a budget, but I agree with what Nova Thug has stated.
Something to keep in mind regarding the suspension geometry of this era with GM suspensions is the poor camber characteristic that GM purposefully designed into the suspensions..

When the suspension compresses the top of the wheel cambers out positive towards the fender.. This problem can be addressed in a couple of different ways which will improve the handling of the car overall..

The Guldstrand modification is one method to address the problem. Tall camber correcting spindles are another way to get better negative camber gain.
... And one other additional way to gain negative camber curve with this era of GM suspensions is to remove the standard upper ball joints and replace them with taller upper ball joints. That's what I did when I rebuilt my front suspension. I used the Proforged 1/2" taller upper ball joints.

I also noticed in your photos that you did not have any shims installed between the upper control arm cross shafts and the sub frame mounts prior to adding the 1/8" shims. That seemed strange.
Here is a quick way to see what type of camber you may have on your front wheels.

Position your car on a level surface. While your tires are on the ground, roll the car forward about 10 feet and stop. This will "normalize" your front suspension components.

Take a straight edge (or any known piece of straight metal) and place it onto the outer lip of the front wheel so it is 90° perpendicular to the floor/ground. Place a level on the straight edge. Look at the level's horizontal bubble.

If the bubble is centered between the two "level" lines, car has zero camber.
If the bubble is sitting about 1/2 way into the inside line of the level, you will have aprox .5° positive camber.
If the bubble is sitting about 1/2 way into the outside line of the level, you will have aprox .5° negative camber.
If the bubble passes either the inner or outer "level" line, you probably have too much positive or negative camber.

I remember these references from when I was doing my own front end alignment in my garage. I used a digital level and some homemade turn plates to accomplish this. Note: In the photo below, the digital level is what was used to adjust the camber and caster. The regular level was used to confirm that the straight edge on wheel was 90° perpendicular to the floor when both wheels were facing forward.


P.S. It looks like you have Torq Thrust II wheels.
 
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