LS1 front brakes on G body spindle

BOXCARS

Master Mechanic
Apr 29, 2017
337
281
63
Could you fit 15" rims with the LS1 rear brakes?

Some 15" rims work. I had a set of 8" aluminum rims with drag radials on board and they fit. I couldn't tell you what rims work and what rims don't fit, but it certainly is possible.
 
  • Like
Reactions: 1 user

81cutlass

Comic Book Super Hero
Feb 16, 2009
4,639
13,542
113
Western MN
Great write up! Thank you for creating/posting this, it is much better and a lot more clear than a lot of threads out there. Question for you - do you happen to know or measure the width of the final hub assy? I’ve got the parts to do this but waiting to buy AL hubs (personal preference, plus I want .5” studs). Will definitely be using this for reference when mine is done.
Tony_ru thanks for the CAD drawing.
Turned down diameter of the stock hub is 5.85". I bought a pair on ebay for my conversion.
I couldn't find the outer diameter of the Willwood hubs on their site but I also wonder that since their hubs are designed to be used with their rotor adapters, whether they work with LS1 rotors and calipers. Could be the thickness of the abutment bracket needed will be different.



Btw in my mock-up, I found 5/16" to be the correct thickness needed. Not the 3/8" that the 81cutlass suggests. I made a 3/8 bracket for my first mock-up and rotor was not quite centered in the caliper.
He also has M12 X 1.5 listed for the bolts needed for the calipers. LS1 Calipers are M12 X 1.75 so he should correct that in his list.
I also opted for tapping the holes in the spindle to 7/16-20 instead of M10 X 1.5. The 7/16 is slightly bigger which I think is better here.[/QUOTE]


Width of the hub assembly, do you mean width of the hub and rotor to know how long of studs to purchase? I don't know off hand but the studs were 54mm and were a good length. 2" studs should work for your application for next closest standard size.


Yeah, M12x1.75 looks right, i fat fingered that one.

I am guessing the difference in 5/16 to 3/8 is a combo of tolerance stack. It's only 0.0625 and with the taper roller bearings, the hub, the rotor, the caliper bracket, the spindle, and the rough mill stock flat bar thats 6 parts right there, Even if the tolerances were +-.010" that could stack to about 1/16", plus I doubt aftermarket rotors are that tightly controlled.
 
  • Like
Reactions: 1 user

TexasT

Master Mechanic
Mar 20, 2008
411
94
28
Texas
I have seen this type of brake upgrade before and sadly I have heard of one downside. The stock hub is designed to be reinforced by the integral rotor, so cutting it off really weakens the stock hub casting due to the grain structure of the cast iron. This is why cracks are common with a hub with a cut off rotor. There are aftermarket rotorless hubs that are designed for such use but they are not cheap. Aonther issue is I think LS1 brakes require a 16 inch and larger rim. Stock 15 inch rims won't clear them which can be a problem for some of us.

I would be interested to see pix of these failed hubs. I have a hard time believing the hub with or without the rotor isn't up to the task of supporting its corner of the car no matter the situation.

This looks like an excellent way to upgrade on a budget.
 

BOXCARS

Master Mechanic
Apr 29, 2017
337
281
63
I would be interested to see pix of these failed hubs. I have a hard time believing the hub with or without the rotor isn't up to the task of supporting its corner of the car no matter the situation.

This looks like an excellent way to upgrade on a budget.

I'm fairly certain I've run the LS1 brake upgrade on my GN for close to 100K miles and also other installations on other G-body cars I've owned or still own with no issues. I also have an 86 El Camino with this upgrade I performed on it 7 years ago, and 35K miles. So, all in all, I'd say it's a safe upgrade.
 
  • Like
Reactions: 1 user

MC96

Master Mechanic
Dec 7, 2015
458
492
63
I had a friend that ran no RF caliper and machined the rotor off a hub on his dirt car with no issues. If it can survive a rutted track Im sure it can survive the street
 
  • Like
  • Agree
Reactions: 2 users

81cutlass

Comic Book Super Hero
Feb 16, 2009
4,639
13,542
113
Western MN
In terms of failure of the hub due to removing the part that reinforces it-

Something to remember here, the bolts don't hold the wheel on (I guess they sort of do) but not in the way most people think.

The bolts are there to provide clamp load. Think of a wheel stud or any bolt like a C clamp, your wheel is held on with 5 c clamps effectively. Bolting the brake rotor and wheel on creates a pretty strong sandwich and the clamp load is spread out from the entire face of the hub where the wheel is contacting. Yes, the forces in the hub will be high in the direction the stud sits directly around the stud, but any load from the actual weight of the car is supported by the friction.

If you see a car that is hit hard from the side in an accident the hub doesn't usually fail, it's usually the wheel itself or something in the spindle or control arm. If a hub fails or the studs break due to a situation like sliding into a curb and the wheel doesn't bend likely the studs were fatigued or not tight. Even if a car is in a situation where all the weight is on one tire and it's pulling say 1G in a turn, and the car weighs 3500lbs, there is only ever 3500 lbs pushing the wheel sideways at the tire to road contact patch. I can do the exact math but considering a good stud has probably 80,000 pounds per square inch of tensile strength and there are 5 of them, you are going to have to put a HUGE side load on a tire, one that would have blown the bead or bent something else somewhere else.

Yes, fatigue cracking is a area of concern, but both steel and cast iron are relatively resilient to fatigue and a street car situation large loads at the wheels aren't seen. Might be a different discussion if we were talking about building rock crawlers or a baja truck, but for a street strip street car there is enough success with this method, enough OE's doing it and math that generally backs it up for me to feel safe.

Any risk added by this setup is much more greatly offset by the safety of actually being able to stop your car.
 
  • Like
Reactions: 3 users

Clone TIE Pilot

Comic Book Super Hero
Aug 14, 2011
3,828
2,565
113
Galaxy far far away
I would be interested to see pix of these failed hubs. I have a hard time believing the hub with or without the rotor isn't up to the task of supporting its corner of the car no matter the situation.

This looks like an excellent way to upgrade on a budget.

Hairline cracks from the stud holes going down the entire side of the hub. The intregal rotor acts as a reinforcing band around the outside circumfluence. Generally that style hub has a thinner wall casting than hubs with a seperate rotor as the loads and stresses are displaced through the intregal rotor. The advantages of intregal rotor hubs are being cheaper to make, lighter, and stronger than seperate hub and rotor. Big disadvantage is they are harder and more expensive to service the brakes.

So when the rotor is machined off, the loads and stresses are no longer displaced. They just build up inside the hub casting with its thin walls that now lack reinforcing.
 
  • Like
Reactions: 1 user

roger1

G-Body Guru
Aug 23, 2010
537
767
93
San Angelo, TX
...So when the rotor is machined off, the loads and stresses are no longer displaced. They just build up inside the hub casting with its thin walls that now lack reinforcing.
This is the part that is not correct.
The hub gains the reinforcing back when it's clamped together with the new separate rotor. Properly torqued lug nuts stretch the lugs which applies a constant tension that makes all the forces act upon the entire unit as if it were one single structure. This structure includes the hub, rotor and wheel.
 
  • Like
Reactions: 1 user

Clone TIE Pilot

Comic Book Super Hero
Aug 14, 2011
3,828
2,565
113
Galaxy far far away
This is the part that is not correct.
The hub gains the reinforcing back when it's clamped together with the new separate rotor. Properly torqued lug nuts stretch the lugs which applies a constant tension that makes all the forces act upon the entire unit as if it were one single structure. This structure includes the hub, rotor and wheel.

Except the grain structure is screwed up from machining the rotor off and thd grains do not connect in two seperate pieces. With the rotor cut off, it exposes grain ends in the hub casting which acts similar to stress risers. The hub does not fully regain its full strength from bolting a seperate rotor back on, and there is still a slight airgap around the circumfluence, so you can center it with a dial gauge. It is not uncommon for these machined down hubs to crack from just pressing new studs in before they are even put into service.
 
  • Like
Reactions: 1 user

GBodyForum is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to amazon.com. Amazon, the Amazon logo, AmazonSupply, and the AmazonSupply logo are trademarks of Amazon.com, Inc. or its affiliates.

Please support GBodyForum Sponsors

Classic Truck Consoles Dixie Restoration Depot UMI Performance

Contact [email protected] for info on becoming a sponsor