What the berkeley is the propose of a single screw to hold a rotor on a hub? It's got lugs to keep it in place between the wheel and hub.
I'm doing the rear brakes on my '03 Cooper S, and the screws seized. I managed to round out the Torx head on one and twisted the head off the other. They seem to be Grade Eleventybillion, because drilling them isn't going so well. :(
Not much purpose, as far as I can tell, but eleventy billion Volvo 240s were built that way, so I'm used to it.
I think it's just there for assembly purposes. If you manage to get the bolt out, I wouldn't feel bad about leaving it out on reassembly.
I've heard assembly purposes as well.
Usually requires an Impact driver to remove here in Michigan
It holds the rotor to the hub during assembly.
Also holds the rotor to the hub when you're working on the car. If you don't hold the rotor to the hub, and your work jostles the rotor loose from the hub, rust will fall in between the two and you'll shortly have a heinous brake pulsation.
They keep rotor up against the hub for quicker caliper install thats all. Never try with out an impact screw driver.
They aren't that useful for holding the rotor on the FC RX-7's hub and they strip easily to boot. However, FC rotors have an extra hole that you can put the screw into to help pop a stuck rotor off the hub.
I just had to deal with that screw on a friend's MCS. The LF just would NOT break free. I pounded on it forever with my impact driver. Nothing.
With the torx starting to get buggered, I eventually decided to either drill it or give it one last shot with an air impact gun. The gun broke it free.
Slather the screw with antisieze upon reinstalling. Sometimes that helps.
It's main purpose is to keep the rotor in place on the hub and the lug bolt holes lined up. After dealing with another friend's car with aftermarket bbk rotors without a locator bolt, fitting the wheel can be a pita.
If you have an air hammer put a point tip on it and use that to start turning the screw. Finish with screw driver. The screw will end up mangled, but it will come out.
http://www.youtube.com/watch?v=YxQk7Pz_vfc
Or just drill into the screw with a 11/32 bit until the head breaks off, then forever use the lug nuts on the rotor whenever you're working on the car.
The holes in the rotors are generous for the stud/wheel bolts. I'm of the belief that the single locating bolt prevents the rotor from slipping so that it won't ovalize the bolt holes. I had a missing locator bolt on the RF rotor of my M3. Though I did not notice any loss in braking performance, I did notice that the road wheel bolt holes in the rotor were becoming increasingly oval when changing back and forth between road and track wheels. Now I'm sure they'll be howls that the road wheel bolts will clamp the wheel to the hub and that it won't move, but there you go.... Just my observation/experience.
m
Are you actually torquing the wheels?
The e30 has them. I always figured it was to hold the rotor in place when doing wheel installs, since the stock setup has the stupid lug bolts and no studs. Now that mine has studs I don't use the screw anymore....
if you have the caliper off and a completely stripped out holddown screw, and you dont need to reuse the rotor, position the screw opposite the caliper location and a good heavy whack (bigger=better) with a sledge hammer will often break the head off if all else fails. it'll generally leave enough of the screw to use heat and vice grips to remove completely. just throw on a lug bolt/nut so the rotor doesnt fly off.
7pilot wrote: The holes in the rotors are generous for the stud/wheel bolts. I'm of the belief that the single locating bolt prevents the rotor from slipping so that it won't ovalize the bolt holes. I had a missing locator bolt on the RF rotor of my M3. Though I did not notice any loss in braking performance, I did notice that the road wheel bolt holes in the rotor were becoming increasingly oval when changing back and forth between road and track wheels. Now I'm sure they'll be howls that the road wheel bolts will clamp the wheel to the hub and that it won't move, but there you go.... Just my observation/experience. m
There are lots of cars that have no such rotor screws.
I put it back together without the screws. It's got to be for assembly; it was a bitch lining everything up. Stupid lug bolts.
Most Volvos have them, but they're lug bolts, not studs. I've always put them back on when doing brakes. I'd imagine it'd be a little more frustrating lining everything back up without them. On the 850/70s the rotor screw also locates the factory wheel to further aid in aligning everything.
Volvo 850 Brake Rotor Guide Pin:
RexSeven wrote: They aren't that useful for holding the rotor on the FC RX-7's hub and they strip easily to boot. However, FC rotors have an extra hole that you can put the screw into to help pop a stuck rotor off the hub.
I remember getting into a fight on a hyundai forum about that. The hole the screw fits into on the older Tiburons and Elantras threaded for larger than the holding screw. You put a 13mm ( going by head size, I forget the pitch/thread) into it and thread it against the hub.. pops the rotor right off.
A lot of people called me a liar until I quoted the factory Repair Manual. (helps to own one)
I think most rotors with retaining screws also have a threaded hole for a jacking screw.
Had the same problem on the MINI. A mechanic friend used an impact screwdriver and a 4 lb engineer hammer on those screws. That did the trick. Installed rotors with coated top hats and new screws, and the screw heads still look new. Haven't touched them since I replaced them 60k. I now own an impact screwdriver. The hammer was mine to begin with.
In reply to bigdaddylee82:
Funny thing about that guide pin I noticed on our 850. With the factory wheels only one of the voids between the lug holes was open enough to clear the pin.
I'm staring at a stack of used MINI and VW rotors. None have threaded holes for jack screws. I have seen that on other brakes, though. Usually drums.
TreoWayne wrote: There are lots of cars that have no such rotor screws.
And they almost all have/had little clips that held the rotors or drums to the hubs. These got removed and thrown away the first time it needed to come off, of course.
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