Do 911's use more rear brake than front for stopping?

[cabmandone]

I was checking my rotor temps the other day because I have a humming noise when I slow down or come to a slow rolling stop that I thought might be a brake that was grabbing. My front temps were 116 and my rear were 126 which made me wonder if Porsche used more rear brake than front or if I have a problem I should be looking for.
BTW, I'm thinking wheel bearing installation is on my short list of things I'll be replacing. I think I have the humming sound narrowed down to that. You hear a hum and feel a very slight vibration when it occurs.

Thanks in advance for any input.

[Mick_D]

pretty sure any vehicle moving forward will use more front brake than rear brake. If your rear brake temp is higher it could be due to less efficient cooling or grabbing or any number of reasons. If your brakes are properly adjusted, they should grab evenly front and back

[tobluforu]

Make sure parking brake isn't dragging to much.

[chris_seven]

The bias is around 62/38 front the rear on a standard set up

116 - I assume Degrees Fahrenheit isn't very hot and the difference between front and rear is likely to be affected by airflow.

At higher temperatures you may see a different result and a hard driven car I would expect rotor temps to be at least 3-400 degF.

In the extreme on a hard driven rally car with the right pads discs will glow red hot.

[Steve@Rennsport]

I would also check for sticking caliper pistons as this causes the pads to drag on the rotors and THAT will account for higher rotor temps.

[DanielDudley]

Originally Posted by Steve@Rennsport

I would also check for sticking caliper pistons as this causes the pads to drag on the rotors and THAT will account for higher rotor temps.

And swollen hoses. Same result.

[DRACO A5OG]

What year is your car?

[cabmandone]

Originally Posted by DRACO A5OG

What year is your car?

Sorry, I have been out and hadn't been checking this thread. My car is an 85.

For those implying stuck calipers, they would have to be stuck very evenly since both fronts were the exact same temp and both rears were the exact same temp. I think the brakes are likely working as they should. My lines are SS braided.

[DRACO A5OG]

Us 3.2's have a proportioning valve in the frunk inline to the the rears. If anything, if that leaks, you will have less braking all around.



You may want to consider rebuilding the caliper seals and check condition of the pistons, if pitted it could be sticking. BTW they are 42MM and NLA in the US. Must get from UK, a member here Chris Seven makes titanium coated ones or SS from Bigg Reds. Very reasonable including shipping.

Mine are pitted and not holding pressure well at all, Swapped front pistons, totally changed my braking. 3 out of 4 were pitted and leaking.



Lesson here is changed brake fluid regularly.

[Bill Verburg]

Originally Posted by cabmando

I was checking my rotor temps the other day because I have a humming noise when I slow down or come to a slow rolling stop that I thought might be a brake that was grabbing. My front temps were 116 and my rear were 126 which made me wonder if Porsche used more rear brake than front or if I have a problem I should be looking for.
BTW, I'm thinking wheel bearing installation is on my short list of things I'll be replacing. I think I have the humming sound narrowed down to that. You hear a hum and feel a very slight vibration when it occurs.

Thanks in advance for any input.

My car is an 85

the 3.2 Carreras( ie '84-89 911) have the most rear bias of any Porsche street car below 33 bar line pressures, you would still expect the fronts to be warmer than the rears but not by much, in relatively light braking.

Things that can cause any rotor to run warmer than usual are frozen pistons, internally swollen lines, different pads, time related heating/cooling curves for different rotor sizes

[chrisbruck]

My rear pads definitely wear out faster if that means anything...

[Conekiller]

I go through the rears at almost a 2 to 1 ratio on my 87 911 track car. It seems that the Carreras wear our rears faster especially on the track for most people I've talked to

[chris_seven]

Originally Posted by chrisbruck

My rear pads definitely wear out faster if that means anything...

I think it just means that the rear pads wear more quickly than the front

The pad area will have a significant impact on wear rates and you can be certain that any road car has a front brake bias as this will provide much more stability than a rear bias.

[Sboxin]

Originally Posted by Conekiller

I go through the rears at almost a 2 to 1 ratio on my 87 911 track car. It seems that the Carreras wear our rears faster especially on the track for most people I've talked to

If you are doing a lot of track days you might consider different pads . . .

We have been using Pagid Black on the rear for a few years now and they wear and stop just fine.
Also, we use Raybestos 43 on the front . . . along with slotted rotors.

Regards,

[Conekiller]

Originally Posted by Sboxin

If you are doing a lot of track days you might consider different pads . . .

We have been using Pagid Black on the rear for a few years now and they wear and stop just fine.
Also, we use Raybestos 43 on the front . . . along with slotted rotors.

Regards,

I'm using pfc08 front and rear. Are you suggesting switching to a different compound for the front and rear?

[DRACO A5OG]

^^^ if you do not mind the race car squeel.

[Sboxin]

Originally Posted by Conekiller

I'm using pfc08 front and rear. Are you suggesting switching to a different compound for the front and rear?

That will be up to you - - I was just sharing what works for us . . . a harder compound (I think) on the rear - - but the previous owner went thru a lot of pads to arrive at the ones we have used for 8 years on the track.

I thought you might be using stock pads . . . and my thought was that you will need to test some different pads to see what works for you . . .

Regards,

[Sboxin]

Originally Posted by DRACO A5OG

^^^ if you do not mind the race car squeel.

? ? ? What squeal . . . the exhaust is 108 dBa . . .

Regards,

[winders]

Originally Posted by Sboxin

? ? ? What squeal . . . the exhaust is 108 dBa . . .

Now I know one reason why you don't run here is Northern California!

[Conekiller]

Originally Posted by Sboxin

That will be up to you - - I was just sharing what works for us . . . a harder compound (I think) on the rear - - but the previous owner went thru a lot of pads to arrive at the ones we have used for 8 years on the track.

I thought you might be using stock pads . . . and my thought was that you will need to test some different pads to see what works for you . . .

Regards,

Gotcha. I've always run pfc 97 and now 08. Overall I like them as they are good on the track and street with only minor squeal. I just wish they didn't chew through rotors.

How do the raybestos compare to PFC? I just bought this set of 08 but I might give those a try as they are priced better next time around