How Hard Is It To Change The Brake Rotors?

[b-man]

I'm curious, how hard is it to change the brake rotors on a '02 c2 coupe? On some cars it is *very* easy and on others, it's difficult. I know that it's not part of the routine brake pad change but, has anyone done this?

b-man

[Loren]

Once you have the caliper off their are only two phillips head screws. Fronts take about 30 seconds each. The rears take a little longer because you need to release the parking brake tension on the inside (drum/shoes). Replace the rotor and then re-adjust it. Maybe 10 minutes each?

[b-man]

That's great. Thanks for the information Loren. My brake pad warning light came on but, I am taking a long trip before I can change them. I'm really nursing the brakes but, just in case I end up scoring the rotors, I want to know what the worse case scenario is.

b-man

[Loren]

If the sensor light came on then you will need new sensors also. The light activation means the sensor has worn through. If you are lucky and change your pads before the light comes on you can usually reuse the sensors.

[b-man]

Thanks Loren. I have those sensors on order too.

One additional item I ordered was the caliper bolts. I think the vendor called them "cheesehead bolts" and said that they are normally changed. I didn't see them in you DIY section but, I ordered them anyway. I thought it would be better to have them and not need them, then the other way around.

Do you normally change them? What torque setting do use use, and do they require a special tool? Do you use any antiseize compound? I haven't even looked at my brakes up close so, I don't know anything about the setup. But, I figure it can't be too difficult.

b-man

[Loren]

One additional item I ordered was the caliper bolts. I think the vendor called them "cheesehead bolts" and said that they are normally changed. I didn't see them in you DIY section but, I ordered them anyway. I thought it would be better to have them and not need them, then the other way around.

Do you normally change them? What torque setting do use use, and do they require a special tool? Do you use any antiseize compound?

First the calipers do not need to come off unless you need to change the rotors. If you do, Porsche recommends that you change the caliper bolts each time. I usually don't unless they show signs of wear. Torque is 63 ft-lb and they are a large allen head bolt (sorry, can't remember the size).

I would recommend NOT using any type of grease or antiseize anywhere near the brakes. The new vibration dampeners should have adhesive to hold them in place and that is all you need.

[KarlS]

The cheesehead bolts are 12mm allen heads. I recommend springing for a Snap-On 12mm socket for a 1/2" drive so that you can use it with a torque wrench. I snapped several Craftsman 12mm 3/8 drive sockets trying to free up stuck caliper bolts before I finally spent the money for the Snap-On and haven't had any problems since.

Porsche recommends applying Optimoly TA on the wheel centering hub before installing a new rotor. They are silent on the use of anti-seize but I always use it as the bolts from the factory seem to have an anti-seize compound on them.

Changing the front brake pads takes less than half an hour start to finish, even if you are doing it for the first time. I'd highly recommend changing your front pads before driving the car on a long trip.

Karl

[b-man]

KarlS, do you change the caliper bolts when you are doing a standard pad change? I know Loren says they don't need to be changed and that he normally doesn't. But, I'm just trying to get more information and am curious what others are doing, or if it's a good idea to do it even though they don't need to be changed?

Also, how can you tell if the caliper bolts are "worn" (as Loren said)?

b-man

[umn]

KarlS, do you change the caliper bolts when you are doing a standard pad change?

I'm sure he won't, because as Loren pointed out, you do not need to remove the calipers to change pads.

If you have to remove the calipers for some other reason such as changing rotors, that's a different story. In answer to your question, it is not always possible to tell from visual inspection if a bolt needs changing or not.

I am a little surprised to hear that Porsche recommend changing them, because other manufacturers don't.

One reason would be if the bolt was to be tightened into the plastic range. However, the bolt is M12x1.5x72. Under the conservative and most likely assumption of bolt grade 8.8 and a coefficient of friction of mu=0.125, the recommended torque would be 83 Nm, which is pretty much the 63 ft-lb that Loren mentioned.

I can therefore only assume that they are concerned about progressive crack growth during cyclic loading, which could occur due to loss of preload (or because someone hasn't tightened them properly in the first place).

Anyway, I don't think there is anybody in this forum who can answer this question. Considering the low price of the bolts and the importance of the part in question, I would probably go with Porsche's recommendation.

Cheers

Uwe

Edited March 29, 2004 by umn

[b-man]

Just FYI, I checked yesterday and the cheesehead bolts (caliper bolts) take a 10mm hex tool, not 12mm. I'm just bring this up so someone doesn't order the wrong tool (like I did!).

b-man

Edited April 11, 2004 by b-man

[danjen]

Did you end up changing the rotors out? If so, was there anything else that you ran into. I know that I need to change the pads and I need to measure the rotors. Hopefully they are o.k.

If not, any learnings that you coud share ... parts, tools, watchouts ...etc would be much appreciated.

Thanks in advance.

[umn]

I'd just recommend a few things:

1) Get yourself a hand impact driver (should cost you less than 20$) to open the two little sunk cross-head screws that hold the discs in place. With an impact driver they come out no problem, but with a screw driver (possibly even the wrong one) you'll damage the head and you'll have one hell of a job getting them out.

When fitting the new discs, put in two new screws. Don't tighten them much, b/c all they do is hold the disc in place if the wheel is taken off.

2) De-grease the new discs ***everywhere and very carefully*** before fitting them. They are usually covered with some sort of oil to prevent corrosion during transport. Use brake-cleaner to get the stuff off.

3) Clean the surface of the wheel hub where the disc fits *very carefully* such that it is clean of any rust or corrosion and *do not grease* this surface.

- If you don't clean it properly, the disc will not be absolutely level with the wheel hub and start vibrating or wear unevenly.

- If you have grease between disc and wheel hub, there will be no frictional connection between disc and wheel hub, and most of the brake force will be transferred through the wheel bolts. Not very good. The same holds true between wheel and disc.

4) At the front, there is a left disc and a right disc, which can be distinguished by the cross-drill pattern.

Cheers,

Uwe

Edited July 7, 2004 by umn

[b-man]

Did you end up changing the rotors out? If so, was there anything else that you ran into. I know that I need to change the pads and I need to measure the rotors. Hopefully they are o.k.

If not, any learnings that you coud share ... parts, tools, watchouts ...etc would be much appreciated.

Thanks in advance.

danjen, I did not change my rotors. Actually, I didn't even measure them to see if they were in spec. I have confidence in the brakes being over engineered so I think they are fine for another set of pads. I never track my car. I'll just change the rotors the next time I change the pads.

The only problem I had was not removing the adhesive backing from the silencers. It's not difficult or tricky, I was just being stupid. I described this in my first post here:

http://www.renntech.org/forums/index.php?showtopic=1708

Also, I was fortunate that I had a good knife to use to slide between the silencers and pads (actually the back of the pads) when I was removing the old pads. I think a putty knife may be too dull. I slid my knife into place (between the silencers and pads) and then twisted it to separate them.

I also used a pair of pliers that looked like the "channel lock" style, similar to http://www.channellock.com/acb/stores/2/pr...&Product_ID=117. These were very handy when I retracted the pistons back into the caliper. I would just squeeze the old pads back away from the surface of the brake disc. I used a scrap piece of pretty thick leather (about 2" x4") to cover the brake caliper to avoid scratching it.

Good luck and let me know if you have any other questions.

b-man

[danjen]

Thanks for the quick feedback. I measured the rotors last night on all the wheels and all were 0.5 - 1 mm thicker than what I read is recommended before replacing. Looks like just a brake job and i'll be set for now. Thanks again!

Dan

[alter_schwede]

changed both the rotors and pads for the front axel today with a very good friend, took us approx. 1hour pro wheel, pretty smooth actually no major problem even though the discs where pretty rosty.

one thing which created a small problem were the vibration absorber pads were still glued to the brakepads, a bit odd I think due to the heat generate by braking and the glue still holds, so that was a bit tricky to separate them a part.

so I'm pretty happy and even enjoy braking now :D

Edited July 9, 2004 by alter_schwede

[b-man]

changed both the rotors and pads for the front axel today with a very good friend, took us approx. 1hour pro wheel, pretty smooth actually no major problem even though the discs where pretty rosty.

one thing which created a small problem were the vibration absorber pads were still glued to the brakepads, a bit odd I think due to the heat generate by braking and the glue still holds, so that was a bit tricky to separate them a part.

so I'm pretty happy and even enjoy braking now  :D

Are you going to change the rear rotors too? If so, please let me know how how it goes (with any tips or tricks) after you're done. I haven't changed mine yet but, I would appreciate any information that could help me when I do change them. Thanks.

b-man

Edited July 10, 2004 by b-man