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Modifying 84-87 front rotors into hubs for brake upgrade by fieroguru
Started on: 01-15-2013 07:39 PM
Replies: 14 (22 views)
Last post by: jaredmurray88 on 03-31-2013 10:16 PM
fieroguru
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Report this Post01-15-2013 07:39 PM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
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.
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FIEROSMIGLA
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Report this Post01-15-2013 08:20 PM Click Here to See the Profile for FIEROSMIGLAClick Here to Email FIEROSMIGLASend a Private Message to FIEROSMIGLAEdit/Delete MessageReply w/QuoteDirect Link to This Post
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 .

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1988 FIERO GT RED 5 Spd
1988 FIERO GT BLACK 5 Spd working project

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ericjon262
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Report this Post01-15-2013 08:28 PM Click Here to See the Profile for ericjon262Send a Private Message to ericjon262Edit/Delete MessageReply w/QuoteDirect Link to This Post
WHY DOESN'T THIS FORUM HAVE STICKIES!!!
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RCR
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Report this Post01-16-2013 07:35 AM Click Here to See the Profile for RCRClick Here to Email RCRSend a Private Message to RCREdit/Delete MessageReply w/QuoteDirect Link to This Post
There is a Fq/How-to section, and that is where this belongs.

Thanx Fieroguru for the write-up.

Bob
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fieroguru
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Report this Post01-16-2013 06:23 PM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
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.

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fieroguru
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Report this Post03-30-2013 01:28 PM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
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:
http://www.fiero.nl/forum/F.../HTML/065345.html#p0

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

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Arns85GT
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Report this Post03-30-2013 02:10 PM Click Here to See the Profile for Arns85GTClick Here to Email Arns85GTSend a Private Message to Arns85GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
Excellent writeup Fieroguru. Thank you

Arn
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babyboy761
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Report this Post03-30-2013 08:46 PM Click Here to See the Profile for babyboy761Send a Private Message to babyboy761Edit/Delete MessageReply w/QuoteDirect Link to This Post
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.
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mmeyer86gt/gtp
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Report this Post03-31-2013 03:29 PM Click Here to See the Profile for mmeyer86gt/gtpClick Here to Email mmeyer86gt/gtpSend a Private Message to mmeyer86gt/gtpEdit/Delete MessageReply w/QuoteDirect Link to This Post
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.
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fieroguru
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Report this Post03-31-2013 04:07 PM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
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).]

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Will
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Report this Post03-31-2013 04:13 PM Click Here to See the Profile for WillClick Here to Email WillSend a Private Message to WillEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by fieroguru:

A quick/crude method for removal of the rotor portion is to use an angle grinder with a 4 1/2" cut off disk:
http://i152.photobucket.com...Upgrade/IMG_0019.jpg

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)
http://i152.photobucket.com...Upgrade/IMG_0024.jpg



Do you not have a part-off tool for your lathe?
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fieroguru
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Report this Post03-31-2013 06:14 PM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Will:


Do you not have a part-off tool for your lathe?


I have a few, but they don't like being used when the circular path is perpendicular to the body of the tool. The body tends to rub the side of the cutout. What I need is a heavy duty plasma cutter so I can just them off, then to the lathe work.

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

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Report this Post03-31-2013 08:20 PM Click Here to See the Profile for WillClick Here to Email WillSend a Private Message to WillEdit/Delete MessageReply w/QuoteDirect Link to This Post
No, the direction of tool motion should be radial, not axial.
Basically, making exactly the same cut with the part off tool that you demonstrated with the angle grinder.
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fieroguru
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Report this Post03-31-2013 08:48 PM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Will:

No, the direction of tool motion should be radial, not axial.
Basically, making exactly the same cut with the part off tool that you demonstrated with the angle grinder.


Now I see... might have to try that way.
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Report this Post03-31-2013 10:16 PM Click Here to See the Profile for jaredmurray88Click Here to Email jaredmurray88Send a Private Message to jaredmurray88Edit/Delete MessageReply w/QuoteDirect Link to This Post
I thought about something like that but clamping a spindle for a trailer or the like in a vise and holding a grinder to it while spinning around the rotor to get a nice even cut if that makes sense..
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