Front Disc Brake Problem

[veeeight]

Hi All,

Fairly new to 993 ownership.
The question I have is concerning front brake discs. I am getting a bad vibration through the steering column when I brake (more than likely warped discs)
I have been told that it is fairly common on the 993. The discs were replaced in 2016 by an independent Porsche dealer at 55,000 miles and then replaced in my ownership by the same dealer 4,500 miles later because of the bad vibration through the steering column. I have driven 4,000 miles since then and now the bad vibration has returned.
I would expect new discs to last at least 30 to 40 thousand miles so I am at a bit of a loss to understand why this is happening after a few thousand miles.
Any thoughts or experiences with the same problem?
Thanks Phil

 

[Graham-S]

My OEM discs have been on the car 14 years and done 27k miles including 4 trips to the Isle of Man
What discs and pad have been used?
Graham

 

[les richards]

Hi Phil, yes, been there and got the t-shirt!
Had the calipers sorted due to plate lift corrosion. Then new disks and pads and eventually got the shakes. Indy checked front suspension but found nothing amiss suggesting warped disks although run-out was in spec. I had them skimmed and they were immeadiately great but it didn't last. Tyres were needing replacing (coming up to ten years - oops) so had four new Michelins fitted hoping it would do the trick. It didn't. This has been going on over 3/4 years now, never failed an MOT on steering faults but vibrates under braking at about 70mph or so. I check tyre pressures every trip - it's a garage queen so not used often - have tried different pressures but no improvement. Cadence braking seems to diminish the effect, mimicking the ABS I guess.
Brake pressure is good and performance is up to the mark, vibration excepted.
There's a guy on 911UK who has the same issue but haven't heard from him for ages so presume he's not fixed it yet. There are some who say it's not possible to warp disks so opinion is divided.
Haven't got an answer for you but thought it might help for you to know what has been tried but, sadly, without success. If you do fix it please post the solution.

 

[PORKA]

Hi Phil, yes, been there and got the t-shirt!
Had the calipers sorted due to plate lift corrosion. Then new disks and pads and eventually got the shakes. Indy checked front suspension but found nothing amiss suggesting warped disks although run-out was in spec. I had them skimmed and they were immeadiately great but it didn't last. Tyres were needing replacing (coming up to ten years - oops) so had four new Michelins fitted hoping it would do the trick. It didn't. This has been going on over 3/4 years now, never failed an MOT on steering faults but vibrates under braking at about 70mph or so. I check tyre pressures every trip - it's a garage queen so not used often - have tried different pressures but no improvement. Cadence braking seems to diminish the effect, mimicking the ABS I guess.
Brake pressure is good and performance is up to the mark, vibration excepted.
There's a guy on 911UK who has the same issue but haven't heard from him for ages so presume he's not fixed it yet. There are some who say it's not possible to warp disks so opinion is divided.
Haven't got an answer for you but thought it might help for you to know what has been tried but, sadly, without success. If you do fix it please post the solution.

Hi Les glad to see you still have the car[] Tony does let me know when he sees it. My 996C4S had the same problems but does not have the caliper plates but replaced the front discs and pads plus the dampers with Pagid discs and Pads which lasted about 3000 miles after which it got the shakes on braking, that was after it came with me to OZ. At first I thought it was the heat here but it just got worse until you had to hold onto the steering wheel really hard under braking. My Indy here had a look and the front discs where warped so had them machined and refitted and was great for a while but after about 1000 miles started again. My Indy did say the pads were very hard! So out they came and replaced with Sebro discs and Porsche supplied pads (ATE) and this has now fixed it by all appearances after some 1000 miles. The original pads were in a Pagid box but are in fact ATE (same Part no as the new ones) but the new ones seem better and you get more dust with them. Our conclusion is the pads that were fitted in the UK were either knock offs or not original Pagid, I bought them and had them fitted. My Indy here uses this combo all the time, unless the customer requires OEM Porsche - bloody expensive here - and has never had a problem. Its the second time I have had problems with Pagid discs, my 994 Turbo, bought from the same place and replaced those with Sebro and no problems after.

 

[T911UK]

Have you had the front wishbone bushes replaced? If not this is not helping and may well be the problem

 

[T911UK]

As luck would have it!

https://rennlist.com/forums/993-forum/1144909-installed-new-control-arms-today.html

 

[matthewb]

I don't suppose you've got turbo wheels (hollow spoke), have you?

My front wheels are hollow (long story) - and I had them refurbished. Any amount of braking was painful - the harder the braking the more the steering wheel tried to break my hands off.

I chanced across an article on the blasting media used to clean wheels getting inside the wheel if you didn't bung-up the valve hole (hollow spoke wheels need metal valves). Turned out one wheel had 70g of 'powder' flapping around inside. Perfect now.

HTH

 

[veeeight]

Thanks guys for your replies to my post.

I am investigating which discs and pads were used on the car.

Les thanks for you feedback. It seems you have a similar problem. I have a feeling it might be something to do with the steering and suspension so I am going to have a look to see if anything can be found including the front wishbone bushes.

Not got turbo wheels.

I also noticed that I have some wheel wobble at above 60mph. This might mean that the wheels need balancing or could be linked to the braking problem.

Any more help would be appreciated.
Phil

 

[pse_SC]

I also noticed that I have some wheel wobble at above 60mph. This might mean that the wheels need balancing...

Definitely won’t help - together with worn bushes on the arms would compound the effect []
Good luck with sorting it.

 

[T911UK]

Oh, discs dont warp by the way

https://youtu.be/LVRVe1cEBDI

 

[38F3E1]

Hi Phil, yes, been there and got the t-shirt!
Had the calipers sorted due to plate lift corrosion. Then new disks and pads and eventually got the shakes. Indy checked front suspension but found nothing amiss suggesting warped disks although run-out was in spec. I had them skimmed and they were immeadiately great but it didn't last. Tyres were needing replacing (coming up to ten years - oops) so had four new Michelins fitted hoping it would do the trick. It didn't. This has been going on over 3/4 years now, never failed an MOT on steering faults but vibrates under braking at about 70mph or so. I check tyre pressures every trip - it's a garage queen so not used often - have tried different pressures but no improvement. Cadence braking seems to diminish the effect, mimicking the ABS I guess.
Brake pressure is good and performance is up to the mark, vibration excepted.
There's a guy on 911UK who has the same issue but haven't heard from him for ages so presume he's not fixed it yet. There are some who say it's not possible to warp disks so opinion is divided.
Haven't got an answer for you but thought it might help for you to know what has been tried but, sadly, without success. If you do fix it please post the solution.

If the car is not being used much and is a garage queen it might be down to the rotors corroding (especially the inner surface). You are sort of always in a race between wearing the rotors down through use (which keeps the rust at bay) and them rusting. Also regardless of garage queen or not uneven transfer of friction material onto the rotors can cause vibration. My car can have periods of inactivity (mostly over the winter months) and I do sometimes get the vibration issue starting. I typically first notice it under light braking. When I do get it I know the brakes need some abuse to cure the problem. I will take the car out for a run when there is very little traffic about (6am works around here) and there is a stretch of dual carriage between two roundabouts I go back and forth on. Routine is accelerate up to 70MPH (because you want to remain legal right), gear into neutral (not strictly required) then hard (not violent) constant braking down to 30MPH (hence wanting no traffic following you as it scares the cr*p out of them). It is important you are braking all the way down to 30MPH or 20MPH in one go each time as it is a constant application of the brakes all the way down that gets the heat into the process. Short 70MPH to 50MPH braking does not have the same effect. Repeat a number of times. Gets the disks hot and cleans it all up and transfers a nice even layer friction onto to rotors. This cures the problem for me.

PS I have standard Porsche brake pads on my 993. Never found the need for anything else on a road car.

 

[veeeight]

Thanks Maurice for your reply.
I am beginning to feel that the problem is more towards the steering and suspension rather than the discs, although the vibration did go away for a short time when the last lot of new discs were fitted.
I am going to take the car to a different Indy and ask them to have a thorough look through everything that might be causing the problem.
Cheers Phil