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> drilling 4 to 5 lug rotors...how accurate?
computers4kids
post Oct 3 2008, 09:01 AM
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I had a machine shop redrill my new zimmerman rear 4lug rotors to 5lug. The holes are slightly off and the rotors will not sit flush--they hang-up on the studs. I opened the holes up a bit and it is much better. Unfortunately, they need even more opening which I'm concerned because to do this will make some of the holes loose around the studs. Is this safe?

Choices, do I open the holes up so the rotor will slip around the studs even though some of the studs will be sloppy knowing the wheel studs once torqued will hold things correctly?
or
Do I just go out and buy a set of 914-6 rear rotors and cut my losses? If so does someone have a source near Visalia, CA that I can get fast...I want to put my 5 lug conversion together this weekend? Pelican won't ship for 5 days.
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Cap'n Krusty
post Oct 3 2008, 09:24 AM
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Positioning of the holes CAN be as accurate as you want, IF the machinist is up to it. There IS NO EXCUSE for misalignment, as the tools they would use for this are common to any good machine shop doing this kind of work.

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dbgriffith75
post Oct 3 2008, 11:34 AM
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QUOTE
Positioning of the holes CAN be as accurate as you want, IF the machinist is up to it. There IS NO EXCUSE for misalignment, as the tools they would use for this are common to any good machine shop doing this kind of work.

The Cap'n


(IMG:style_emoticons/default/agree.gif) Nothing more to it.
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davep
post Oct 3 2008, 11:44 AM
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You may be able to open up the interfering holes just enough. Make sure you use the screws to fasten the rotor to the hub; critical to try and center the rotor correctly. Bolt on the wheel as usual. Positioning of the rotor by use of the screws will go a long way in ensuring the rotor is centered, and the wheel bolts clamp it in place.
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MartyYeoman
post Oct 3 2008, 02:13 PM
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QUOTE(davep @ Oct 3 2008, 10:44 AM) *

Make sure you use the screws to fasten the rotor to the hub, critical to try and center the rotor correctly. Positioning of the rotor by use of the screws will go a long way in ensuring the rotor is centered.

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Spoke
post Oct 3 2008, 02:35 PM
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I thought the rotor was centered by the clearance of the inside of the rotor to the hub, not the bolt holes.
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MartyYeoman
post Oct 3 2008, 02:58 PM
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There are no centering features on the rear hubs, only the two flat-head screws.
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rick 918-S
post Oct 3 2008, 05:58 PM
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Jeeeze! what kind of machine shop were they? I did mine myself on my drill press. It was easy. (IMG:style_emoticons/default/confused24.gif)
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davep
post Oct 3 2008, 06:38 PM
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QUOTE(Spoke @ Oct 3 2008, 12:35 PM) *

I thought the rotor was centered by the clearance of the inside of the rotor to the hub, not the bolt holes.

It is very close, but I would trust the screws to double-check the positioning. Personally, I'd want to spin it and check the runout to triple-check.
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computers4kids
post Oct 3 2008, 08:23 PM
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Thanks for all the replies. I was going to go ahead and open them-up to fit and use the two little screws to ensure the rotor is centered...then bolt it all up. However, even though the fitment won't be seen and won't effect how the brakes work, I'll know it's there and bother the hell out of me. After thinking aout it at work today, I just went ahead and ordered some new 914-6 rotors...I'm kind of a perfectionist. Maybe I would of re-considered after reading all the replies when I got home....but oh well. It happens...I guess.

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Eric_Shea
post Oct 4 2008, 01:56 AM
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I would almost bet it's not the studs/holes.

Look for a ridge on the inside of the 914-6 or 914 rotors. This is something new in the Zimmermans and they don't like to sit on a 914 hub without grinding down that ridge.

It's inside the rotor on the wall of the hat right down where it would mate with the hub.
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melnyk
post Oct 4 2008, 08:14 AM
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QUOTE(Eric_Shea @ Oct 4 2008, 03:56 AM) *

I would almost bet it's not the studs/holes.

Look for a ridge on the inside of the 914-6 or 914 rotors. This is something new in the Zimmermans and they don't like to sit on a 914 hub without grinding down that ridge.

It's inside the rotor on the wall of the hat right down where it would mate with the hub.

i had this issue on my 4 lug rotors. i also couldnt get the grease cap fully on the fronts. the new cone they have on the fronts to hold the wheel is nice but it prevents the cap from going on enough and in turn i had to take off my center caps. (IMG:style_emoticons/default/headbang.gif)
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