Keith SuperDork
12/10/08 11:20 p.m.

Just askin' I'm making a basta...a hybrid braking system, and I need rotors with a 71mm bore and a 4x100 bolt pattern. I could always get the rotors machined, but I'd prefer off-the-shelf for future ease if possible.

oldopelguy HalfDork
12/11/08 12:09 a.m.

That's huge Keith. I would start with the '95 Neon 4-lug or the Saturn SL1, they had the biggest center holes I could find when looking for rotors to use on the back of my Opel.

John Brown
John Brown SuperDork
12/11/08 6:05 a.m.

Try Saturn Ion or Chevrolet Cobalt maybe? GM usually has the largest hub bores around.

mw New Reader
12/11/08 6:43 a.m.

I'm pretty sure nothing has that combo. Just buy which ever 4x100 rotors are cheapest or have the most good replacment options available.

John Brown
John Brown SuperDork
12/11/08 6:47 a.m.

Or turn the hub lip down a little, seeing how under normal circumstance you will use 5 rotors to 1 hub.

jrw1621 Reader
12/11/08 7:03 a.m.

Here is reference tool

BMW 320i

4x100 and a CB of 72.56


walterj HalfDork
12/11/08 7:35 a.m.

Wilwood will sell you rotors with no holes if you have the means to machine them

jstein77 HalfDork
12/11/08 7:40 a.m.

First gen RX-7?

minimac Dork
12/11/08 9:13 a.m.

I use or

linky sucky try this instead or

belteshazzar Dork
12/11/08 9:45 a.m.
jstein77 wrote: First gen RX-7?


Keith SuperDork
12/11/08 10:06 a.m.

Great reference John, thanks.The 320i has drums on the back as far as I can tell, so unless it has non-vented front rotors that's not going to work.

I'll take a closer look and see if the hubs can be turned down. Honestly, at the rate that this car will use rear brakes, having to machine the rotors isn't really that big a deal when I think about it.

Tim Baxter
Tim Baxter Online Editor
12/11/08 10:11 a.m.

Keith, I don't know if it'll help, but according to this the E21 323i used the same rear rotors as the E30. All other E21s were (as you suspected) drums in the rear.

Keith SuperDork
12/11/08 10:33 a.m.

According to the A-Dapt-It website, the E30 has a 57mm bore. Hmm, more research to do...

John Brown
John Brown SuperDork
12/11/08 11:53 a.m.
Line Code UP Part Number 85898 Description Brake Rotor Only - Rear - Ultra Premium Attribute Features & Benefits:NAPA Ultra Premium Rotors Are Precision Machined For Smooth Brake Operation.,Product Features:Out Of The Box "No Turn Guarantee",Brake Rotor Type:Disc Brake Rotor Only-dih Parking Brake,Mounting Type:Type K - Rotor Only. Wheel Studs Are Pressed Into The Hub Only. The Rotor Is A Loose Fit On The Hub & Is Retained By Either Machine Screws Or The Wheel Nuts. See Diagram For More Information.,# of Bolt Holes:4,Bolt Circle Diameter:100 mm, Diameter:10.15", Height:2.36", Thickness When New:.395", Maximum Lateral Runout:.002", Discard Thickness:.331", Vented / Solid:Solid, Center Hole Diameter:2.444"
Keith SuperDork
12/11/08 12:14 p.m.

John Brown is the man. 2.444" (aka 62mm) is not a big enough hole, but now I know.

fiat22turbo SuperDork
12/11/08 12:57 p.m.

Why can't you use vented rotors on the rear?

Keith SuperDork
12/11/08 12:59 p.m.

Because my calipers aren't wide enough to cover them, and I don't want to lose parking brake functionality by using front calipers. I'm trying to retain Miata calipers so I have commonality with the other three cars in the garage that run them.

Jensenman SuperDork
12/11/08 1:08 p.m.
John Brown wrote: Or turn the hub lip down a little, seeing how under normal circumstance you will use 5 rotors to 1 hub.

+1. This way if something goes bad at a track day etc you have a reasonable chance of finding something at PepZone etc.

Why not turn the axle snout and the flange OD to the same as a Miata and have anyone but Dutchman Motorsports redrill them for 4x100? Then you can use readily available proven stuff.

Keith SuperDork
12/11/08 1:36 p.m.

I'm going to disassemble this axle to figure out what can and can't be resized. Looks like finding off-the-shelf rotors that are readily available isn't going to happen, so it's time for plan B.

Type Q
Type Q HalfDork
12/11/08 6:18 p.m.

John's link didn't specify whether the "CB" dimentions were front or rear. The rear hubs for a 90's vintage Civics and Integra's are larger in diameter than the fronts. It still may not be big enough for what you need.

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