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Just Some Dude in Jersey
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Discussion Starter · #201 ·
Boy, you guys can think of more stuff to complain about. I did the mod in 2013. 15,000 miles ago. They work just fine.
 

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Senior Contributor
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Boy, you guys can think of more stuff to complain about. I did the mod in 2013. 15,000 miles ago. They work just fine.
Not complaining, just discussing safety issues. Have at it since you are comfortable with it.
 
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Just Some Dude in Jersey
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Discussion Starter · #203 ·
As far as bolt-centric and hub-centric, hub-centric goes out the window whenever you add wheel spacers or slide a rotor over the hub flange and bolts. Now you are bolt-centric. Our oem stamped steel wheels had big lug nut holes, so needed to be centered on the hub........ideally, but the taper of the oem lug nuts pretty much made our wheels center on the bolts. Same situation with wider aftermarket wheels. Some of you are implying that any situation or set up that doesn't allow the hub center extrusion to stick out and enter an exactly matching recess in the wheel, the lug nuts will bend or snap off. Nonsense. This mod has been done many times by people smarter than me and it works just fine. Wider wheels and spacers have been used hundreds of times and you don't hear people saying their wheels snapped off their studs and fell off.

The only reasonable point you could complain about is my having to file the lug stud holes in the rotors to make them fit over the oem-spaced studs. I file all 4 holes slowly and carefully with a slightly undersized file and repeatedly test fit it onto the studs. 1/8". Even if I radically F'd up and filed one hole 1/16" too close to the hub, but the others were perfect, the other 3 would prevent the rotor from spinning eccentrically. I only file until the rotor just barely fits over the studs and I end up with no play or wiggle at all. The 4x100 rotors I got from Keith wiggle a tiny bit on the bolts, mine don't.
 

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Über Genius
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As far as bolt-centric and hub-centric, hub-centric goes out the window whenever you add wheel spacers or slide a rotor over the hub flange and bolts. Now you are bolt-centric. Our oem stamped steel wheels had big lug nut holes, so needed to be centered on the hub........ideally, but the taper of the oem lug nuts pretty much made our wheels center on the bolts. Same situation with wider aftermarket wheels. Some of you are implying that any situation or set up that doesn't allow the hub center extrusion to stick out and enter an exactly matching recess in the wheel, the lug nuts will bend or snap off. Nonsense. This mod has been done many times by people smarter than me and it works just fine. Wider wheels and spacers have been used hundreds of times and you don't hear people saying their wheels snapped off their studs and fell off.

The only reasonable point you could complain about is my having to file the lug stud holes in the rotors to make them fit over the oem-spaced studs. I file all 4 holes slowly and carefully with a slightly undersized file and repeatedly test fit it onto the studs. 1/8". Even if I radically F'd up and filed one hole 1/16" too close to the hub, but the others were perfect, the other 3 would prevent the rotor from spinning eccentrically. I only file until the rotor just barely fits over the studs and I end up with no play or wiggle at all. The 4x100 rotors I got from Keith wiggle a tiny bit on the bolts, mine don't.
Not me. I don't think it will be a problem at all.
The disk is hub centric. Even OEM will rotate a couple degrees when just sitting on the lugs. Wheels are lug centric.
 

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Senior Contributor
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As far as bolt-centric and hub-centric, hub-centric goes out the window whenever you add wheel spacers or slide a rotor over the hub flange and bolts. Now you are bolt-centric. Our oem stamped steel wheels had big lug nut holes, so needed to be centered on the hub........ideally, but the taper of the oem lug nuts pretty much made our wheels center on the bolts. Same situation with wider aftermarket wheels. Some of you are implying that any situation or set up that doesn't allow the hub center extrusion to stick out and enter an exactly matching recess in the wheel, the lug nuts will bend or snap off. Nonsense. This mod has been done many times by people smarter than me and it works just fine. Wider wheels and spacers have been used hundreds of times and you don't hear people saying their wheels snapped off their studs and fell off.

The only reasonable point you could complain about is my having to file the lug stud holes in the rotors to make them fit over the oem-spaced studs. I file all 4 holes slowly and carefully with a slightly undersized file and repeatedly test fit it onto the studs. 1/8". Even if I radically F'd up and filed one hole 1/16" too close to the hub, but the others were perfect, the other 3 would prevent the rotor from spinning eccentrically. I only file until the rotor just barely fits over the studs and I end up with no play or wiggle at all. The 4x100 rotors I got from Keith wiggle a tiny bit on the bolts, mine don't.
You're too sensitive to discussion. I never said you were nuts or suggested that you should not do it. Like I said, have at it.
 

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Just Some Dude in Jersey
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15,466 Posts
Discussion Starter · #207 ·
Early Style Axle Rear Disc Brakes Using the Gordo/Gary Formula

I couldn't adapt the later style rear disc brake kit to work with the brackets I had made for an early c-clip style axle and to the axle in general. I did this mod to my GTX car using the parts that Gary Farias had calculated that I would need. It was easy as pie to hook up that set up. The kit was off in almost every dimension. There's nothing wrong with the kit, it just wasn't designed to fit the early style axles. No spacer or shims needed, just some hole elongation of the rotors and the making of the brackets. So, I'm calling this the "Gordo/Gary C-clip Axle Rear Disc Brake Mod". Other guys have done this mod and used their own calculations and sourced parts and made brackets based on that.

I was headed down the road towards Modification Hell, so I decided to set the late axle kit aside and buy the rotors and calipers I used when I did this mod previously. Miraculously, the rotors fit without the need to ream out the holes to fit the 4x100mm axle bolt pattern. I have no explanation for this. The lug bolt holes seem larger and the rotor is loose on the bolts. I don't know if this will cause a problem, I'll probably have to make bushings to tighten and center things up. In the pics, "Previous" means the kit rotors/calipers and "New" means the Gordo/Gary Mod stuff. The "new" stuff uses larger rotors with taller "hats", but more minimally built calipers.

New vs. Previous rotor size comparisons
Rim Gas Automotive tire Composite material Automotive wheel system
Tire Wheel Automotive tire Bumper Rim
Helmet Automotive tire Wheel Gas Engineering
Tire Automotive tire Wheel Tread Alloy wheel
Gas Composite material Nickel Machine Metal
Automotive tire Gas Automotive wheel system Wood Auto part
Automotive tire Yellow Rim Audio equipment Automotive wheel system
Automotive tire Rim Vehicle brake Gas Audio equipment
Wheel Tire Automotive tire Tread Rim
Wheel Tire Automotive tire Rim Automotive wheel system
 

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If the center of the rotor fits clean to the axle hub then the size of the lug holes don't matter. You shouldn't have to do anything to them.
 

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Just Some Dude in Jersey
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15,466 Posts
Discussion Starter · #210 ·
It doesn't fit clean to the center hub, I can move the rotor 1/8". Not a problem, I have various tubing that I can cut little rings off of and slide over the bolts to shim the looseness at the bolt holes.

It's odd that the rotors have this measurement oddity. The measurements match the ones on the GTX in every dimension except the bolt holes. I'm not out of the woods yet, but I'm confident that I can mod my way through, if need be. As a last resort, Gary said that he never got around to installing the same assemblage of parts he got to do this mod and has offered them to me if I need them.
 

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Your Noble Friend ;-)
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4,449 Posts
It doesn't fit clean to the center hub, I can move the rotor 1/8". Not a problem, I have various tubing that I can cut little rings off of and slide over the bolts to shim the looseness at the bolt holes.
I would say, YES, a problem. It is way more important to have the disks centric (immovable) to the hub than the wheels being hub-centric. The force of the brake pads will pull the disks towards one side and it might be enough to overcome the clamping force of the wheel studs which clamp the disks and the wheels to the hub. In this case, they will immediately wobble back and forth for each revolution of the wheel and rip your wheel studs right off.

Dieter
 

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Über Genius
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I would say, YES, a problem. It is way more important to have the disks centric (immovable) to the hub than the wheels being hub-centric. The force of the brake pads will pull the disks towards one side and it might be enough to overcome the clamping force of the wheel studs which clamp the disks and the wheels to the hub. In this case, they will immediately wobble back and forth for each revolution of the wheel and rip your wheel studs right off.

Dieter
I disagree. I can show you factory disks that can move many degrees without being bolted on.
 

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Just Some Dude in Jersey
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15,466 Posts
Discussion Starter · #213 ·
I discovered a fortuitous fix for the too big stud holes in the rotors. The rotors ARE apparently drilled for 4x100mm spacing, but for much larger bolts, so I looked through my stuff for some sort of tubing that would shim away the bolt diameter difference. I tried a couple of ideas that failed or didn't work well until I spotted a piece of GT hood latch bar I had that fit the bolts and the holes. I cut 1/4" wide bits of it off and the fit the bolts tight and perfectly shimmed the bolt diameter gap in the rotor bolt holes. Nice tight fit, perfect solution!

I put things together and things were almost right, but then problems. The rotors seemed 1/2" too large in diameter and were hitting the tops of the calipers, the brake shoes and rotor pistons weren't aligned with the rotors' braking surface very accurately as a result. Also the rotor disc was too far inwards, which required shimming of the bracket on the axle housing, which ain't easy to do. I could redesign the bracket to place the caliper farther outwards to fix the pad alignment problem, but the shimming would still have been necessary. But I didn't have to do all this stuff the first time around! Clearly, either the rotor is wrong in several dimensions or the calipers are wrong in several dimensions. WTF?!!!! I made the same bracket and ordered the same parts, based on the part numbers on the boxes, and nothing is fitting like it did before! Aaaarrgghh!

So, Gary said that he never installed the rear disc brake stuff he bought at the time when I did this conversion the first time and offered them to me. I accepted. So, his parts might get here next week and I'll try again.
 
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