LS1 front brakes on G body spindle

[roger1]

The grain structure of the hub is not "screwed up" and doesn't come into play when analyzing the forces applied across combined unit. The friction across the mating surfaces hold the unit together as strong as the grain structures in the individual castings themselves.

Cracking would only be caused by pressing in studs that are too large in diameter. Take a look at some of the aftermarket lug stud diameters. Some are a few thousandths larger than others. The Dorman long studs I used pressed in with relatively little effort.

 

[TexasT]

I'm not a metallurgist or engineer but I've taken a lot of stuff apart and put a bunch of it back together and I've not seen a hub fail. The hub, rotor and wheel sandwich together as stated above and make it a nifty sturdy unit. As long as the bearings and races are good and the lugs are torqued on properly, I'd run it.

As asked, pix or it didn't happen. It is just your theory or a story you have been told.

 

[Clone TIE Pilot]

Lots of the Turbo Buick guys used to machine down the hubs, but there were a lot of complaints that they cracked around the stud holes. Marcus used to sell them until he had too many cracked hubs, and has stopped selling them and recommends against it. One guy on the Buick boards even had one completely shatter without warning.

The friction across the mating surfaces does nothing to compensate for the lost strength in a radial and circumferential sense. Removing that much material from a casting causes a lot of problems, and yes the grain structure is screwed up as you would cut through many of the grains creating a weaken area. This image should help.

Another thing to remember is that most factory hubs that are seperate pieces from rotors are made of steel instead of weaker cast iron. G bodies can only get away with cast iron hubs because the integral rotor reinforces the otherwise very weak front wheel hub. In addition to this, the heat from removing that much material causes the casting to lose its temper, many machine shops refuse to do it even. Moreover, machining the rotor off, then machining the hub down to fit inside a LS1 rotor removes a lot of meat between the stud holes and the outside edge of the castings.

 

[roger1]

Can you please provide the links to the Turbo Buick forum reports that you mention. I can't find any of them.

 

[81cutlass]

Regardless the decision people go with hubs weather you cut down the stock cast iron drum or get a hub, the premise is the same.

It's still cheaper than the blazer setup in places where spindles are tough to locate, you end up with better bearings, and dont even have to pull off the spindles. The confidence the bigger brakes gain is totally worth it and

And for the people that dont do this setup because they want to keep availability to run 15" drag wheels, I have a home made pontiac rally 15x4.5 with a 165R15 and a 1.5" hubcentric spacer on mine. Wheels fit nicely in the fender and although it does mess up the scrub radius, if you have skinnies it doesnt matter anyways. If you care about handling or scrub radius you are going to have a 16" wheel minimum anyways that solves the clearance problem. Buy a 15" 4th gen spec skinny like a weld RTS, billet specialty, or race star, and it fits without a spacer.

 

[roger1]

I'm in the process of installing LS1 brakes on my stock machined hubs and ran into a glitch today.
The hubs are not fitting the LS1 rotors I bought correctly. The rotors are a brand new set of Raybestos.
There's no problem with the outer diameter the hubs were turned down to but it appears the problem is the fit at the center hole.
Take a look:

I sure am glad I noticed this as it would have caused a catastrophic failure if it was run.
I'm not sure how to go about dealing with this problem though and I'm puzzled why this issue hasn't been reported by others (that I've seen anyway).

 

[BOXCARS]

Are the hubs are rocking in the rotors? Could it be the rotors are warped? If that's the case, exchange them for a different set.

 

[roger1]

Are the hubs are rocking in the rotors? Could it be the rotors are warped? If that's the case, exchange them for a different set.

I'm not sure why it's rocking in there since it can't be seen. Both hubs in both rotors do the same thing. You wouldn't think they would be warped since they are a brand new set of Raybestos rotors. I got them from Rock Auto.
I was thinking I should take a hub to O'Reillys and have them pull a new rotor in another brand and see if it rocked in that or not.

One thing is for sure is I can't use what I've got now. There is a problem of some kind.

 

[roger1]

It appears that my problem is warpage in the hubs and not the rotors. Both hubs show a warp with a good straight edge on them. This surface wasn't even touched by the guy that machined the sides down. The only things I can think of that would cause this would either made that way or maybe by heat from usage.

I showed this to a friend of mine and he said take them to a machine shop and have them straightened up.

 

[81cutlass]

Odd, mine looked OK.

Are they GM factory turned down hubs or aftermarket new ones cut down? They look pretty new to me, if they are they were probably tuned offshore and if they are out of flat it doesnt surprise me.