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13" cobra rotors + hub rings, need clarification

Old 03-26-2015, 11:53 AM
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13" cobra rotors + hub rings, need clarification

Hate to beat the dead horse here, but could someone assist me in getting the proper stuff for this BBK swap?

I need to grab the rotors and the rings. Rotors are a no brainer, rockauto, etc. However, im seeing conflicting info on the hub rings needed to center the cobra rotors.

Nissan hub has a 66.1 (66.06 technically) outer diameter, thats a given. So obviously the inner diameter of my hub rings need to be 66.06mm. However im seeing conflicting info on what the outer diameter of the rings should be. Most info im finding is showing the inner diameter of the cobra rotors as 2.8", which comes out to 71.12mm. However - i found at least one thread saying this is not correct (the author bought rings with these dimensions and said he "learned the hard way). I also noted that some rotor brands list the inner diameter of the rotor as being 2.79", which comes out to 70.87mm.

Is this a fluke? Is the author of that thread a dumbass? Are there certain rotor brands to avoid/brands to stick to? I want to make sure i am buying the correct stuff here.

Any help and clarification is appreciated. It seems that 66.06/71.12mm rings are what i need, but i just want to be 100% sure.
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Old 04-03-2015, 04:23 PM
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Have you thought about 6th gen Brakes? 12.6" rotors and calipers for ~$200, no dogbones or rings to mess with. Works really well.
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Old 04-03-2015, 08:25 PM
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Old 04-04-2015, 12:42 AM
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Old 04-04-2015, 09:06 AM
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I actually looked a lot into that setup (aka i studied your thread lol) but i ended up opting to buy a 300zx 13" setup. The problem is that the rings that came with that kit are off by about 1mm in the inner diameter, so they arnt snug on the nissan hub.

Ive been reading everywhere, and have even resorted to sending random PMs to people who have the kit installed or are selling it with the hope that someone can get me the exact measurements of the rings. I still think they are 66.06x71.12mm, but because theres a thread floating around that says those measurements are not correct im no longer certain. Could be possible that the author is an idiot and bought the wrong rings; nissan hub is 100% 66.06mm and cobra rotors should have a 2.8 inch hub bore which comes out to 71.12mm. However ive seen at least one brand advertised as 2.79" hub bore, thus the added confusion..

Had i known id be dealing with this silly stuff for so long i probably would have just went with the 12.6" 6th gens lol. But since i have the 300zx calipers and dogbones already, i really wanna complete the kit to get that 13" overkill
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Old 04-04-2015, 07:45 PM
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So the rings fit loosely on the hubs? What is the actual difference in diameter? Ignore the wheel ID/ring OD, I think you're just confusing the issue. If its close enough you might be able to knurl the hub with a center punch.

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Old 04-04-2015, 07:48 PM
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What do those rings cost? I wouldn't mind having a set of 4 for my wheels.

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Old 04-05-2015, 08:53 AM
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Originally Posted by asand1 View Post
So the rings fit loosely on the hubs? What is the actual difference in diameter? Ignore the wheel ID/ring OD, I think you're just confusing the issue. If its close enough you might be able to knurl the hub with a center punch.

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I dont have the means of getting precise measurement, so i cant get exact. But using a ruler and measuring several times to be safe, it seems that the rings have a inner diam of 67-68mm. I actually fitted them against some brand new H&R hubcentric wheel spacers (not installed) since they were handy and have identical hub size as the nissan hub - theres too much play for them to do the job imo. Knurling out the hub might work, but id rather just have the correct rings for perfect fitment. That and the fact that id one day be parting out the BBK and going back go stock brakes - it would probably be a tough sell having rings that are off in size.

Originally Posted by asand1 View Post
What do those rings cost? I wouldn't mind having a set of 4 for my wheels.

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Im still shopping around, but the website that im probably going to use is charging $7.50 per ring. The catch is that they have a minimum order of $50, so any order below that gets hit with a fee that bumps it up to $50. All other sites either dont have the size or consider it "custom sizing" which costs $50+ for a set of 4.

That being said, i was actually planning to buy 6 rings for $45, and just eat the 5 dollar fee. Im only needing 2 rings, so if you need a set of 4 that would work out perfectly.

Im pretty sure you can mix and match sizes but thats something id have to double check. But yeah if you definetly interested in a set of 4, id be willing to shoot you the extra rings at cost + shipping. Let me know what you think.

Also, all of this would still depend on finding ot what the proper dimensions are to begin with. I would have taken the risk and bought the rings already if it wasnt for the fact that id have extras to resell.

Last edited by Slamrod; 04-05-2015 at 09:04 AM.
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Old 04-05-2015, 12:43 PM
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I have the original Cobra BBK stuff that Jeff92se designed back in the day including his hub rings. Here you go. Let me know if you need anything else

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Old 04-05-2015, 05:45 PM
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Originally Posted by Slamrod View Post
if you definetly interested in a set of 4, id be willing to shoot you the extra rings at cost + shipping. Let me know what you think.

Also, all of this would still depend on finding ot what the proper dimensions are to begin with. I would have taken the risk and bought the rings already if it wasnt for the fact that id have extras to resell.
I'm not in a position to buy rings right now, honestly the lug nuts center the wheels fine for now.

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Old 04-06-2015, 09:54 AM
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That was me I sold him the 300zx kit with the 'correct rings' sorry since I never installed the kit or even attempted the install for that matter, I figured that the rings were correct size. I hope you find a solution Slamrod.
Maybe you can ask these guys?:
http://www.ebay.com/sch/i.html?_odkw...+71mm&_sacat=0

Last edited by Maximeltman; 04-06-2015 at 09:58 AM.
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Old 04-07-2015, 04:34 PM
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Originally Posted by James92SE View Post
I have the original Cobra BBK stuff that Jeff92se designed back in the day including his hub rings. Here you go. Let me know if you need anything else
THANK YOU SO MUCH!!!

Now im REALLY confused lol. According to your measurements, the ring inner diameter is about 67.8mm, which is larger than what the nissan hubs are (66.06mm).

I went back and remeasured the rings i have, and lo and behold, the inner diameter measures about 67.8mm. Which means i do infact have the correct rings, since they are the same size as the jeff92se rings (which are tried and true).

Wtf am i missing here? Im not understanding this one bit. Are the hubs on our cars actually slightly larger than the 66.06mm they are classified as? Im completely and totally lost on how this makes sense; obviously it must work because its what people have used in the past successfully - but what is the logic behind it?

Clearly ill be needing to go and test fit the rings on the car itself, instead of just test fitting them on the H&R hubcentric spacers, because on the spacers the ring is too big. Which confuses me since the spacer "hub lip" measures out the same as what the nissan hub should be, 66.06mm...

Pic below shows the ring centered best i could on the spacer "hub", its hard to see in the picture but the shadow between the ring and spacer is a gap. The ring is not snug at all.



Can anyone help explain or rationalize how this makes sense? I feel like im missing something painfully obvious and im simply failing to see it. Any thoughts on this would be highly appreciated, thanks for the help so far everyone.

Last edited by Slamrod; 04-07-2015 at 05:06 PM.
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Old 04-07-2015, 07:35 PM
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Well, I think the difference is the position it's being measured on the hub. IIRC, the hub is a bit "tapered". Meaning the OUTSIDE "lip" of the hub (where the wheel would sit) is 66.1. However, the "base" (engine side) of the hub is a larger diameter. Therefore a ring you would use for the wheel vs a ring you would use for the rotor are not the same size. Wheel ring would be smaller diameter than the rotor ring.
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