I have a set of 4 bolt rear discs which I need to re-drill for 5 stud. How do I go about doing this? is there a technical 'How to' somewhere I can follow. It seems simple but to get it right and accurate seems like I need to get a professional precision engineering company to do it. Who has done this before themselves and what's involved, lessons learnt etc
Cheers
Moggy
Full Version: How do I re-drill the rear discs for 5 stud?
QUOTE(moggy @ Oct 21 2009, 08:57 AM) 
I have a set of 4 bolt rear discs which I need to re-drill for 5 stud. How do I go about doing this? is there a technical 'How to' somewhere I can follow. It seems simple but to get it right and accurate seems like I need to get a professional precision engineering company to do it. Who has done this before themselves and what's involved, lessons learnt etc
Cheers
Moggy
I would buy six rear rotors instead brand new. They will fit perfectly and you will get new rotors at the same time. About 100 bucks each
It's hard to argue against advice from George, BUT...there are some of us who just can't resist the temptation to DIY and save a couple of bucks (they don't call me Cheapsnake for nothing).
I'm going to assume you also have to drill and stud your hubs so I'll start there. Here's how I did it:
1. Machine a hardened piece of round bar into a center punch for a slight interference fit with the bolt holes in your 5-lug wheel.
2. Bolt the hub into your wheel through one of the existing 4-lug bolt holes.
3. Cut a piece of scrap metal for a snug fit between the hub and the inside of the rim nearest the bolt that you just put in.
4. Now, take that metal spacer and place it at 90* intervals around the hub/rim and bump the hub into place so the spacer has the same snug fit all the way around the hub as it did at the bolt hole. This will take a bit of patience, but it's absolutely critical to getting the hub centered on the wheel. When you're satisfied it's centered, lock the hub down tight.
5. Fit the center punch you previously made up into each bolt hole in the wheel (make sure it's perpendicular to the hub surface) and whack it. You'll want to make sure the hub is supported from below, not just hanging off the wheel when you do this.
6. Now you have your center punches for drilling. I started with a 1/4" pilot bit and finished with 9/16". 9/16" was just a tad tight so I just took a RCH off with a round file. Again, make sure your drill press is set up for perfectly perpendicular holes.
6. Spotface the holes on the backside of the hubs where the surface is rounded. I just used a handheld high speed rotary tool with a 3/4" abrasive bit. All you want to do is provide a flat surface for the stud head to land on.
(At this point you'll want to drill your rotors before the studs are in so jump ahead to Step #6a.)
7. Drive the studs in. If you don't have a shop press a 5" vise works just fine. Simply cut a 1 1/2" length of 1/2" pipe, slip it over the threaded end of the stud, clamp the whole thing into the vise and crank it down until the head is snug against the backside.
Drilling the rotors:
6a. You've got the hard (critical) part done once your hubs are drilled. Now is the time to drill your rotors, before the studs go in. Start by bolting the 4-lug rotor onto the newly drilled 5-lug hub through one of the bolt holes and center it in just the same way you centered the hub to the wheel.
6b. Center punch the boltholes onto the rotor from the backside of the hub.
6c. Drill the rotor for the new boltholes, 5/8" I think.
8. Go get yourself a beer and admire your work.
Good luck.
Tom
Here's how I did it:
I'm going to assume you also have to drill and stud your hubs so I'll start there. Here's how I did it:
1. Machine a hardened piece of round bar into a center punch for a slight interference fit with the bolt holes in your 5-lug wheel.
2. Bolt the hub into your wheel through one of the existing 4-lug bolt holes.
3. Cut a piece of scrap metal for a snug fit between the hub and the inside of the rim nearest the bolt that you just put in.
4. Now, take that metal spacer and place it at 90* intervals around the hub/rim and bump the hub into place so the spacer has the same snug fit all the way around the hub as it did at the bolt hole. This will take a bit of patience, but it's absolutely critical to getting the hub centered on the wheel. When you're satisfied it's centered, lock the hub down tight.
5. Fit the center punch you previously made up into each bolt hole in the wheel (make sure it's perpendicular to the hub surface) and whack it. You'll want to make sure the hub is supported from below, not just hanging off the wheel when you do this.
6. Now you have your center punches for drilling. I started with a 1/4" pilot bit and finished with 9/16". 9/16" was just a tad tight so I just took a RCH off with a round file. Again, make sure your drill press is set up for perfectly perpendicular holes.
6. Spotface the holes on the backside of the hubs where the surface is rounded. I just used a handheld high speed rotary tool with a 3/4" abrasive bit. All you want to do is provide a flat surface for the stud head to land on.
(At this point you'll want to drill your rotors before the studs are in so jump ahead to Step #6a.)
7. Drive the studs in. If you don't have a shop press a 5" vise works just fine. Simply cut a 1 1/2" length of 1/2" pipe, slip it over the threaded end of the stud, clamp the whole thing into the vise and crank it down until the head is snug against the backside.
Drilling the rotors:
6a. You've got the hard (critical) part done once your hubs are drilled. Now is the time to drill your rotors, before the studs go in. Start by bolting the 4-lug rotor onto the newly drilled 5-lug hub through one of the bolt holes and center it in just the same way you centered the hub to the wheel.
6b. Center punch the boltholes onto the rotor from the backside of the hub.
6c. Drill the rotor for the new boltholes, 5/8" I think.
8. Go get yourself a beer and admire your work.
Good luck.
Tom
Here's how I did it:
Essentially, you need to set them up on a dividing head secured to the table on a vertical mill. Any other way is second rate or less. Given the setup time and the cost of new /4 rotors, it'd be cheaper to go with new /6 rotors. The Cap'n
QUOTE(Cap'n Krusty @ Oct 21 2009, 01:25 PM)
Essentially, you need to set them up on a dividing head secured to the table on a vertical mill. Any other way is second rate or less. Given the setup time and the cost of new /4 rotors, it'd be cheaper to go with new /6 rotors. The Cap'n
![popcorn[1].gif](http://www.914world.com/bbs2/style_emoticons/default/popcorn[1].gif)
considering the cost of quality machine shop time now-a-days george and the capt. gotta be right on this.
Ahhh... just noticed this is for rotors only.
Thoughts:
914-6 rotors will work. They are expensive and they will need 2mm milled off the edge. It will cost you around $40.00 in addition to the cost of the rotors.
Take a new set of -4 rotors over to a machine shop and have them drilled with a 5x130 pattern. Again, it should run around $40.00. Probably a less expensive proposition.
Bonus Using the -4 Rotors: The rotor attachment screws will line up on your hubs (if your 5 hubs were converted/indexed properly). This allows you to fix your rotor to the hub while setting the venting clearance. The 914-6 rotor has a different pattern for the attachment screws and they will only bolt up to a 911 hub.
Thoughts:
914-6 rotors will work. They are expensive and they will need 2mm milled off the edge. It will cost you around $40.00 in addition to the cost of the rotors.
Take a new set of -4 rotors over to a machine shop and have them drilled with a 5x130 pattern. Again, it should run around $40.00. Probably a less expensive proposition.
Bonus Using the -4 Rotors: The rotor attachment screws will line up on your hubs (if your 5 hubs were converted/indexed properly). This allows you to fix your rotor to the hub while setting the venting clearance. The 914-6 rotor has a different pattern for the attachment screws and they will only bolt up to a 911 hub.
Good info, thanks Eric!
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