Help with a front rotor issue

[ADrewzki]

I was replacing my stock front rotors today and after breaking off the grade 10 bolt and having to hammer the rotor off, I finally got my new ones on. They new rotors are TPM (drilled and slotted) from SBR with new Hawk pads. I got them all bolted up and took them for a drive. I noticed a loud scraping sound coming from the passenger side. When I had my rear ones done a few weeks ago, they scraped and were loud for about a week before calming down so I didn't pay too much attention to the fronts. I got about a block down the road I decided that something was definitely wrong. I stopped and took a quick look and for some reason the rotor was scraping on the caliper mount. It had scraped a small portion of the outer edge off. Mind you, the stock rotor rotated perfectly and didn't scrape or anything so I'm thinking what the? The thickness of the stock rotor and the new TPM is virtually identical on a side by side comparison. I took it apart again and ground away the rust on the hub thinking it would help. For some reason, it's still scraping. I finally ended up putting my stockers back on and calling it a day. Tomorrow I will put my drivers side rotor on that side just to see if it is maybe a rotor that is untrue but in the meantime, does anyone have other suggestions as I what the issue might be? Thanks guys.

-Drew

 

[steve]

I assume you mean it rubbing on the caliper bracket, the one that holds the pads.
I'm not sure what you ment by outer edge. Is it rubbing on the inside edge, outside edge, top of the rotor, or someplace else?

Does it feel like the rotor hat is seating flat on the hub?

Steve

 

[ADrewzki]

The rotor is rubbing on the caliper mount. The piece that mounts onto the wheel hub which in turn the caliper mounts to. It's rubbing on the outer portion of the surface facing out. In other words, if you were looking at the rotor from the side of the car, you can see where it's fubared. The rotor is flat as far as I can tell. You can usually just torque your wheels on there and it'll flatten out pretty good. At this point I am thinking that maybe the rotor itself is not as true as it should be.

 

[steve]

The rotor is flat as far as I can tell. You can usually just torque your wheels on there and it'll flatten out pretty good. At this point I am thinking that maybe the rotor itself is not as true as it should be.

Does the rotor rub continously or pulsate?

You shouldn't have to bolt the wheel on to get the rotor to seat on the hub. I reason I'm asking is, I remember people having problems with rotors that were missing the radius on the inside edge of the hub hole. They wouldn't really seat flat against the hub, so the rotor could be true but not mounting true.

What happens if you swap the rotors from side to side?

Steve

 

[ADrewzki]

Rotor does not rub continuously. Probably about 3/4 of the way. I haven't had a chance to swap the TPM rotor from the drivers side because I was so disgusted with it today but definitely give it a go tomorrow. It seats flat relatively speaking. I'll try and take some pictures tomorrow. Hopefully it is just a rotor issue that can be resolved pretty easily. Not sure what you mean by "missing the radius on the inside edge."

Drew

 

[steve]

Not sure what you mean by "missing the radius on the inside edge."

If you look at the hub the center part doesn't meet the hub face as a 90 degree angle it's radiused where the two meet. The inside of the rotor hat needs a matching radius or it won't go all the way on.

Steve

 

[ADrewzki]

I swapped the driver's side rotor over this morning and it fit like a champ which made me think of what would cause this. I took a second look at the rotor hat and the driver's side had a much better step to it where it fits around the hub as opposed to the passenger side. The radius was perfect though. I'm going to see if I can find a shop that will grind it down to match and hopefully that'll fix the problem. Thanks for the help.

Drew

 

[ADrewzki]

Here's some pictures of what's going on.

 

[steve]

That step as you call it is the radius I was talking about. Rather than cutting it rounded, they just cut it at an angle. Make sure you let SB know that the rotor was defective.

Steve

 

[ADrewzki]

Yep. I already emailed them so I'm awaiting word from them. Thanks a lot for your help Steve. You are worthy of your wiseman status.

 

[jtmcinder]

Before you mail the rotors back, measure a few more things.

1) The thickness of the center part of the rotor -- the part that mounts to the hub.

2) The backspacing of the rotor, as in the depth from the inside face of the rotor to the face of the center part that is in contact with the hub.

3) The thickness of the rotor, itself.

Compare these to the stock rotors. If any of these are radically different from stock, then the rotor can rub the bracket.

- Jtoby

 

[Todd TCE]

You or someone replace a wheel bearing some time ago?

The larger radius is there to clear the second step put on the later bearing. For some reason you can only get the 3G bearing now which has the second slightly smaller radius in it as well as the larger one. The difference pops up on brake kits for me from time to time.

One hub measures 3.640 the other 3.712 or about a .030" second step. My guess is that the maker simply doesn't know there are different parts or they should ask which bearings you have.

'least that's my take on what I see based on similar issues.

 

[ADrewzki]

I haven't replaced the bearing in the year and half that I've had the car. What you say might be true, but the stock rotors have that same step in them so either all rotors are stepped or my rotors were replaced not too long ago. Thanks for the info though.

 

[steve]

Todd,

I scratching my head trying to figure out what your talking about. The only thing I've come up with is that your saying that you can only get 3g hubs now and that it's got a different profile.
The bearings fit in the spindle not the hub and that's why I'm lost by what you wrote.

Steve

 

[Todd TCE]

I figured this would open a can of worms....

The 2G bearing is 'replaced by' the 3G part when purchased from the dealer. I know this to be so as I've had a few customers who's brake hats did not fit their hubs. I went to the dealer to get a bearing and found they were shipping out 3G parts with a slightly larger center bore. I think my numbers are correct above. The differnece was small but no way were the alum hats going to fit the hub. In fact the late 99 came with these larger steps! Bastards...!

Mits seemed to get around this via either the chamfer put on the rotor ro the rotors being larger and 'located' by a set screw. I'm not up on stock parts fully so that one I'll leave to you.

However...if you ever buy a BBK you might want to review your hubs before you order.

Look close at the hubs 90* step. If it has ONE step it's a 2G if it has TWO steps it's a later replacement or 3G part. Sort of a step and then a step. And only .030" or so high!