Need tips on how to change rotors/pads on 951?

brock · 09-26-2001, 06:09 PM

Hey guys, I have a Haynes but they dont cover the 4 piston brakes on install of pads etc. Is there a FAQ site or does anyone have a quick rundown on how to install new cross drilled rotors and metal master pads on my 951? What about sensors? Can I put these on later?
Thanks for the suggestions...
God Bless America!
Brock 86 951

T86951 · 09-26-2001, 06:41 PM

I don't know of a site but someone else might. The stock rotors on a 951 are very good rotors. Are you going to autocross or something? For street use I wouldn't spend 5 or 6 hundred on cross drilled rotors.

As for as the pads they really go on about the same as a 944. I have a 944 and 951 and changing the pads is no different except you have more pistons to pry back in on the 951 so you can get the new pads in. The hardest part of the job is jacking the car up, taking the wheels off and putting them back on.
My 951 is an '86 also.

[This message has been edited by T86951 (edited 09-26-2001).]

Pilot_951S · 09-26-2001, 07:00 PM

Brock,

First oif all changing the pads is totally easy, you simply open the spring clip that holds the pad in the caliper with a pair of plyers (squeeze and then it opens like a hatch) and then pull the pads out. The rotors are easy as well, you need to unbolt the caliper (19mm bolts I beleive) and then remove the screws that hold the rotor in place. The front is somewhat more complicated on an 86 than on an 87 or later car.

Now I'm going to say this only once DO NOT PUT CROSS DRILLED ROTORS ON YOUR CAR! Was that clear enough? The brake rotors do not have enough mass to handle being drilled, your performance will decrease due to decreased mass and surface area and rotor warpage will occur prematurely for the same reason.

From Baer Racing

Quote:

"In racing, crossdrilling was designed to alleviate a problem known as out-gassing. In some of the older pad compounds, when the pads reached elevated temperatures consistent with performance or racing use, the binder (that’s the material that holds the friction material in place) boiled off, producing a gas. This gas would build up between the rotor and the brake pad, effectively keeping the pad from directly contacting the rotor. The holes provide a relief path for these gasses, as do slots, so the pad can once again contact the rotor. Crossdrilling was NOT designed to facilitate cooling."

Anyway pads don't out gas anymore, at least a modern race pad doesn't and if you've got a crummy street pad you shouldn't be getting it that hot on the street anyway. At most you could get slotted rotors but again, there is no reason for it.

Lastly your pad choise isn't totally evil but I would spend the extra money for a real quality pad like the PFC Z rated street pad (Part number 345Z or 0345.10, they are the same front and rear on your car.)

-Drew

[This message has been edited by Pilot_951S (edited 09-26-2001).]

[This message has been edited by Pilot_951S (edited 09-26-2001).]

brock · 09-26-2001, 07:22 PM

Hey guys thanks for the tips! I actually spoke to Vertex and they told me that these rotors are excellent due to the casting they go thru.Thats right! The holes are actually cast during the making! He explained that there will be NO increase in warpage, NO decrease in performance! I understand the mass concept but we are talking minimal amounts (ounces?). So should I try these rotors or say Hell no and send them back? The guy I spoke to swears by them and stated that he promises I wll be happy with them!

?????
Brock

T86951 · 09-26-2001, 08:21 PM

You will spend all that money and see no difference at all!

Daedalus · 09-27-2001, 12:43 PM

I did the rotors and pads myself and it was pretty easy. Pop the hood, open the brake fluid resevoir, and jack up the car. Take the wheels off. Pop open the spring clip that holds the pads in. Remove the pads. Reach around the caliper and remove the two bolts. Remove the two screws that hold the rotor on. Be sure that the emergency brake is turned OFF. Use the old pads and a clamp to reset the pistons. Reassemble. Make sure to pump the brake petal before going for a test spin. You want to get that pressure back in the lines or you will be in for a nasty surprise.

Pilot_951S · 09-27-2001, 06:46 PM

For the benefit of the board I am posting this. This is my repsonse to a question posed earlier. I emailed it to someone else but I thought the information useful so I am posting it here.

I have a large number of customers that have stock Porsche rotors that
are cast with holes that experience premature rotor failure due to the holes
creating a stress riser in the metal. We are not talking about small rotors
either, we are talking 930 rotors, factory big reds, and also factory 993
rotors which are quite a bit larger (and have more mass) than the rotors on
your 86 951. Now admittedly these problems only surface on cars that are
used at the track but the question remains why spend extra for a performance
decrease? If you like the look that is your business. The factory rotors
are built the same way that Vertex is claiming they make theirs, the simple
truth is the factory rotors don't cut it when the car gets to the track. If
you drive only on the street then I agree you will probably not have any
problems (unless you drive like me) and you will have better water
evacuation in the rain, but personally I'd stay with the stock rotors. If
you want better performance get them cryo-treated. My 951 track car has
13.5" Alcon directional 48 vane rotors with 6 slots. No cross drilling at
all. Seen a modern race car with cross drilled rotors? Neither have I .

ninefiveone · 09-28-2001, 09:44 AM

On your '86 the rotor removal will be different than for the '87+ rides. I just went thru this on my own '86 951 and while different, it wasn't any harder than on an '87. Just more time consuming. On an '86 the rotor doesn't have 2 screws that hold it on to the hub. It actually bolts on with 5 bolts to the BACK of the hub. Hence, to change the rotors, you end up pulling the hub off as well. Which gives you a good opportunity to inspect the wheel bearings and repack them. If you need a more detailed set of instructions, http://porsche-944-garage.tripod.com/ and go to the garage shop manual.

Hugh
'86 951

944slide · 09-30-2001, 09:02 AM

I'm also planning a brake job (83 944), and I was wandering which brand of rotor(is zimmerman ok?) and brake pad would be the best for routine street use.

thanks

Lawrence Coppari · 09-30-2001, 10:44 AM

Metal Masters are good enough for street use. PBR is another name for them. They are inexpensive, too. Talking brake pads here. Don't know about rotor brands.

[This message has been edited by Lawrence Coppari (edited 09-30-2001).]

Pilot_951S · 09-30-2001, 07:43 PM

For your 83 PBR Metal Master will be fine, if you want something more exotic try Hawk or Porterfield. You can get Hawk from www.tirerack.com . Zimmerman is and OE manufacterer their rotors are quite good so that is a good choice, you could also get Brembo. If you plan on any track or heavy autocross go for cryo treatment of the brake rotors Diversified Cryogenics http://www.frozenrotors.com/ is one of the larger PCA proponents of this. Seems to provide a much bigger improvement on smaller brakes than on the larger ones. Of course stay away from any cross drilled garbage.