Modifying 84-87 front rotors into hubs for brake upgrade (Page 1/2)
fieroguru JAN 15, 07:39 PM
If you want to put any brake upgrade onto the front of the 84-87's, you must first convert the front rotors to hubs. In the picture below are two new rotors, one has been modified, the other has not. It the following pictures I will walk through the process of modifying the second one.

A quick/crude method for removal of the rotor portion is to use an angle grinder with a 4 1/2" cut off disk:

Cut the rotor off at the corner with the cutoff disk making sure you can see daylight through the cut, then rotate and cut some more.

Once the perimeter is cut, the rotor is still attached by the ribs on the rear, cut these as shown, but be careful not to cut too deep.

If the rotor hasn't came off yet, flip it over and smack the rotor with a large hammer and it should come free:

Like I said this is a simple/crude method of removing the rotor and faster than doing this part on the lathe (or at least in my lathe)

Then chuck it up in the lathe and clean up the crudeness and taper the ribs back at a 45 toward the center.

Now if you installing the GrandAm rotors, then you also have to cut the OD of the hub down so the rotor will slide over it. Since these are for a 12" brake upgrade, there isn't any need to turn down the OD unless you really wanted to to reduce weight.

Here is the matched set:

The last order of business is to install the longer wheel studs since these hubs will now be used with removable rotors. A good indication of the needed stud length is to ckeck a rear wheel bearing since they all had removable rotors from the factory. About 1 3/8":

If you are converting OEM rotors to hubs, then the longer stud is Dorman PN 610-323 Qty:10

However, if you are using new aftermarket hubs, then the holes for the wheel studs are often larger and you need another stud option (which was the case with these hubs). Here is a side by side of the stock fiero wheel stud and the one from the aftermarket hubs with the larger shank:

So if stock fiero wheel studs don't fit the hub hole, then use this part number: Dorman 610-427. It has a stepped shank and will fit the hole in the rotor while still retaining the M12-1.5 thread pitch.
Here is what these studs look like installed. Notice it has slightly more than 1 7/16" threaded length, but more importantly notice the protruding shank:

To use these wheel studs you will need to bevel or enlarge the backside of your brake rotor holes so they slide over the enlarged shank. Your concentric rings between the hubs and the rotors will keep them centered, so you don't need a tight fit to the studs. Also, this enlarged shank will not protrude past the rotor.

I am still waiting for all the studs to arrive for this set of rotors, then I will show some better pictures of the studs and the installation process.

By using this process above, it takes me about 1 hr per hub to perform the modification and I charge $175 shipped (lower 48) for 2 new hubs, 10 new/longer wheel studs installed, and all machine work necessary for the conversion. PM me if you are interested in having me supply these parts for your brake conversion.
Can't wait to get my hubs , great work , this is a A+ Forum member , great communication and outstanding work. This is for my chop top Fiero .

1987 FIERO GT WHITE 5spd
1988 FIERO GT RED 5 Spd
1988 FIERO GT BLACK 5 Spd working project

2012 Nissan 370z Nismo

ericjon262 JAN 15, 08:28 PM
RCR JAN 16, 07:35 AM
There is a Fq/How-to section, and that is where this belongs.

Thanx Fieroguru for the write-up.

fieroguru JAN 16, 06:23 PM
The studs came in today!

To install them, I clamp the hub in the vise and slide the stud into place, lube the threads with some oil, slide on a few washers and use an old lug nut for installation. The lug nut will get the end of it worn down on the washers, so make sure it is a junk spare not a nice one from a set.

All done and ready to box up and ship out:

Since these hubs went through a machining process, I took them in the house and rinsed them inside and out with hot water to remove any debris. Then dried them, sprayed them down with WD40, wiped off the excess and placed each of them in a 1 gallon zip lock bag.

fieroguru MAR 30, 01:28 PM
I have been doing a few of these lately and have switched to turning off the rotors on my brake lathe (creates less mess in the shop).

New Hubs:

Knock out the stock wheel studs:

Turing off the rotor from the backside:

Rotor removed - rough condition:

Chucked up in the other lathe to clean up the cut and put a 45 degree taper to the modified area:

About 6 lbs 1oz is removed per hub as part of this modification, so to calculate the increased weight for the larger rotors, subtract 6 lbs from the rotor weight.

Stock 12lbs 12oz (13.5 lbs is the nominal advertized weight, but it will vary slightly depending on brand)

Modified 6 lbs 11oz:

The longer wheel studs are 1.8oz heaver per wheel.

I will supply you with 2 new hubs, machined for your brake upgrade with longer wheel studs installed for $175 shipped to US and $200 shipped to Canada (shipping is about $50 vs. $15 in the US).

It normally takes 7-10 days from time of purchase to shipment as the rotors normally take 3-7 days to arrive. PM me or see the thread in the mall if interested.

Mall thread:

[This message has been edited by fieroguru (edited 03-30-2013).]

Arns85GT MAR 30, 02:10 PM
Excellent writeup Fieroguru. Thank you

babyboy761 MAR 30, 08:46 PM
Wish the setup was available a few weeks ago. Countless hours on the phone calling around DFW. Finally found a shop 15 miles up the road to do it for me. A few days later and $200 out my wallet. I think that you are doing a great service for the community here.
mmeyer86gt/gtp MAR 31, 03:29 PM
i have done 2 sets of these and the problem i am having is that i cannot get the rotor to be centered on the hub so when you go down the road you dont have vibration. any thought on this problem? I have cut down those plastic hub rings to go in between the new rotor and the hub to center it before the tires go on but still get a little shimmy.
fieroguru MAR 31, 04:07 PM

Originally posted by mmeyer86gt/gtp:

i have done 2 sets of these and the problem i am having is that i cannot get the rotor to be centered on the hub so when you go down the road you dont have vibration. any thought on this problem? I have cut down those plastic hub rings to go in between the new rotor and the hub to center it before the tires go on but still get a little shimmy.

What rotor are you running? Did your kit supplier send you 2 sizes of concentric rings (the fronts need to have a smaller ID)? The larger the rotor, the tighter the rings need to be. Have you tried wrapping some electrical tape around the rings to tighten them up?

[This message has been edited by fieroguru (edited 03-31-2013).]