997 GT3 pad choice - Porsche sport or RS29
Discussion
Hi,
I need to replace the front disks and pads on my GT3 which currently has standard disks and RS29s.
I've done a few trackdays and like the feel of the pads on road and track but obviously can't get these through an OPC. My local OPC has suggested standard disks with Porsches hardest (sport) pad for track use. Has anyone had any experience of these, how do these compare to the RS29s?
My disks need replacing because of lots of cracking round the drilled holes, can pads like RS29s cause this or contribute towards it? I know there are alternatives like Alcon but I'm looking to renew the warranty and believe having the Alcons on would prevent this.
Thanks
I need to replace the front disks and pads on my GT3 which currently has standard disks and RS29s.
I've done a few trackdays and like the feel of the pads on road and track but obviously can't get these through an OPC. My local OPC has suggested standard disks with Porsches hardest (sport) pad for track use. Has anyone had any experience of these, how do these compare to the RS29s?
My disks need replacing because of lots of cracking round the drilled holes, can pads like RS29s cause this or contribute towards it? I know there are alternatives like Alcon but I'm looking to renew the warranty and believe having the Alcons on would prevent this.
Thanks
The RS29s are able to operate at higher temperatures for a longer duration than the standard pads, that in turn means the discs operate at elevated temperatures too.As a result they'll crack. The standard pads form a "safety valve" insofar as they're unable to operate for long periods of time at elevated temperatures. So yes, the fitment of the RS29s will make the discs crack more quickly than when running the standard pads.
As for using the hardest OPC suplied pad. How much are they ? I imagine they'll not be cheap once you've factored Porsche Tax into the equation. You're money would be better spent on a set of RS29s IMHO. This is classic case of not being able to have your cake and eat it. If you want improved brake performance, you'll need better quality discs and pads. If you want to retain your warranty, you have to forego the improved brakes (unless you're prepared to remove them every time you visit your OPC . . . .)
As for using the hardest OPC suplied pad. How much are they ? I imagine they'll not be cheap once you've factored Porsche Tax into the equation. You're money would be better spent on a set of RS29s IMHO. This is classic case of not being able to have your cake and eat it. If you want improved brake performance, you'll need better quality discs and pads. If you want to retain your warranty, you have to forego the improved brakes (unless you're prepared to remove them every time you visit your OPC . . . .)
Not my verbage, but a very nice little excerpt that everyone should read on rotor cracks.
Energy is conserved, always. During a braking event, the brakes convert the kinetic energy of the car into thermal energy in the brakes, which we then waste by slowly dumping it overboard into the airstream. The majority of the braking heat is stored in the rotor while we are decelerating. Every pad compound is designed to be a good insulator, so only a small percentage of the heat ends up in the pads. Also, the rate of air cooling of brakes is far smaller than the rate of energy input during hard braking, so the brake heat is transferred to the air gradually during the following straight.
We have to respect the limitations of iron rotors. Iron is very good at both storing and conducting heat, but there is a limit to the rate that iron can conduct heat through itself. That is important for us to understand because although all of the heat is generated at the rotor faces, the thermal mass of the rotor is almost uniformly distributed all the way through its thickness. Because iron has a relatively high coefficient of thermal expansion, the heat conduction rate limit causes the iron at the faces of the rotor to try to expand more than the iron at the center of the rotor thickness while the brakes are in use. That difference in thermal expansion causes stress in the rotor, which can cause the rotors to warp or crack. Its the almost uniform distribution of thermal mass that makes rotors vulnerable to warping and cracking. There is a small variation of material composition and material properties within every casting, and also a variation of wall thickness of ventilated rotors because no casting is perfect.
All of this is particularly relevant for race cars because the rate of heat input during hard braking with sticky tires vastly exceeds the conduction rate limit of iron. So, the way to deal with this issue is to gradually warm up the brakes during the out lap so that the middle of the thickness of each rotor is already somewhat warm when the first hard braking zone arrives. That reduces thermal stress, which reduces the risk of warping or cracking the rotors.
Cryogenic rotor treatment does a very good job of reducing internal stress that was caused during the casting solidification process. That reduces the risk of warped rotors by creating a more uniform stress field. So, it reduces the risk of rotor warping, but it does not eliminate it.
In circumstances where pre-warming the brakes is not possible, you have to limit the rate of heat input when the brakes are cold. The first stop is a lot harder on the rotors than the second one.
Energy is conserved, always. During a braking event, the brakes convert the kinetic energy of the car into thermal energy in the brakes, which we then waste by slowly dumping it overboard into the airstream. The majority of the braking heat is stored in the rotor while we are decelerating. Every pad compound is designed to be a good insulator, so only a small percentage of the heat ends up in the pads. Also, the rate of air cooling of brakes is far smaller than the rate of energy input during hard braking, so the brake heat is transferred to the air gradually during the following straight.
We have to respect the limitations of iron rotors. Iron is very good at both storing and conducting heat, but there is a limit to the rate that iron can conduct heat through itself. That is important for us to understand because although all of the heat is generated at the rotor faces, the thermal mass of the rotor is almost uniformly distributed all the way through its thickness. Because iron has a relatively high coefficient of thermal expansion, the heat conduction rate limit causes the iron at the faces of the rotor to try to expand more than the iron at the center of the rotor thickness while the brakes are in use. That difference in thermal expansion causes stress in the rotor, which can cause the rotors to warp or crack. Its the almost uniform distribution of thermal mass that makes rotors vulnerable to warping and cracking. There is a small variation of material composition and material properties within every casting, and also a variation of wall thickness of ventilated rotors because no casting is perfect.
All of this is particularly relevant for race cars because the rate of heat input during hard braking with sticky tires vastly exceeds the conduction rate limit of iron. So, the way to deal with this issue is to gradually warm up the brakes during the out lap so that the middle of the thickness of each rotor is already somewhat warm when the first hard braking zone arrives. That reduces thermal stress, which reduces the risk of warping or cracking the rotors.
Cryogenic rotor treatment does a very good job of reducing internal stress that was caused during the casting solidification process. That reduces the risk of warped rotors by creating a more uniform stress field. So, it reduces the risk of rotor warping, but it does not eliminate it.
In circumstances where pre-warming the brakes is not possible, you have to limit the rate of heat input when the brakes are cold. The first stop is a lot harder on the rotors than the second one.
Edited by fioran0 on Wednesday 19th September 22:41
On a track you will create cracks from the holes on the standard disc regardless, it will just happen faster with "race" type disc compound like RS29. Personally I would stay away from the OE stuff if tracking the car, go for an Alcon/pagid or a Performance Friction set. Both will last a lot longer that standard, perform better and cost less.
I have seen alcon crack
And at >4x the price they don't last 4 times as long.
I would stay oem disk and rs 29
Rs29 does NOT make the disk crack faster as a poster has said. And they do work better them oem.
The only way they will crack faster is if you do longer stints on track because of less fade, if you do the same laps and use the straights as cool down they are fine.
But you see people vmax on straights on track days which I just fine odd and just puts heat into your disks.
And at >4x the price they don't last 4 times as long.
I would stay oem disk and rs 29
Rs29 does NOT make the disk crack faster as a poster has said. And they do work better them oem.
The only way they will crack faster is if you do longer stints on track because of less fade, if you do the same laps and use the straights as cool down they are fine.
But you see people vmax on straights on track days which I just fine odd and just puts heat into your disks.
mrdemon said:
And at >4x the price they don't last 4 times as long.
I don't know if the prices have changed a lot over the past couple of years, but when I fitted front Alcons they were around 1800 and it was looking like around 1100 for OEM ones (including labour and RS29s for both).This set of Alcons have already lasted more than double the amount of time/track days that I had out of OE discs and I believe that when they need replacing it will be less than I paid originally as the hubs will not need to be replaced this time.
I would chose Alcons every time over OEs.
(prices were for a 996 at the beginning of 2010)
Morning lads,
I don't want to go off topic but my alcons have lots of short hairline cracks in them and a bit of a flared lip on the outer edge.
Should I mic the thickness to check they are still in tol? That's if there are any minimum thickness specs available anyway.
Or is it simply a case of bin them and renew?
Never had Alcons before, what sort of cost are they £500 pair or something? Or more?
Thanks.
Eta - posted at same time as hendy. Thanks for posting prices Hendy.
I don't want to go off topic but my alcons have lots of short hairline cracks in them and a bit of a flared lip on the outer edge.
Should I mic the thickness to check they are still in tol? That's if there are any minimum thickness specs available anyway.
Or is it simply a case of bin them and renew?
Never had Alcons before, what sort of cost are they £500 pair or something? Or more?
Thanks.
Eta - posted at same time as hendy. Thanks for posting prices Hendy.
Edited by marky911 on Thursday 20th September 10:04
I used to use Alcon's and RS29's. Good but expensive and discs did crack. Now use the oem discs with Ferodo DS pads, the discs last a good year of track days the pads are similar wearing to the RS29's stop just as well (IMHO) and you dont get the horrible screeching, which is a real pain on the road.
Loads more info on the USA sites, people just tend to use the cheaper disks and replace more often at £600 the pair all in.
depends if you are doing a 24 hour race I guess ;-) or want to stay out for 30 laps and do 140mph on the straights lap after lap.
on the road oem disks will last you 20k+ miles easy.
I just think Alcon is not the easy fix as people make out , there are loads of pics of cracks disks on the net with them as people stay out longer.
people did ok on oem for years and mk1 GT3 owners have even less brake performace.
swings and roundabouts it seems regarding life and cost.
depends if you are doing a 24 hour race I guess ;-) or want to stay out for 30 laps and do 140mph on the straights lap after lap.
on the road oem disks will last you 20k+ miles easy.
I just think Alcon is not the easy fix as people make out , there are loads of pics of cracks disks on the net with them as people stay out longer.
people did ok on oem for years and mk1 GT3 owners have even less brake performace.
swings and roundabouts it seems regarding life and cost.
I looked at Performance Friction discs for my Boxster: £300 per corner. I bought OEM discs from design911.com instead (turned out to be Pagid) at £50 each. I have to wonder if the PFs could really last 6 times as long. Unless you're racing I reckon on using the cheaper discs and simply binning them more often.
I did also change the air deflectors for larger ones - there is a massive Cup version available for the GT3 which might improve matters.
I did note that PF discs have dimples instead of holes but don't know of any low cost dimpled, one-piece discs currently available for Porsche.
I did also change the air deflectors for larger ones - there is a massive Cup version available for the GT3 which might improve matters.
I did note that PF discs have dimples instead of holes but don't know of any low cost dimpled, one-piece discs currently available for Porsche.
mrdemon said:
Rs29 does NOT make the disk crack faster as a poster has said. And they do work better them oem.
The only way they will crack faster is if you do longer stints on track because of less fade, if you do the same laps and use the straights as cool down they are fine.
The only way they will crack faster is if you do longer stints on track because of less fade, if you do the same laps and use the straights as cool down they are fine.
So we're agreed, they will make the discs crack faster if used for their intended purpose . . . .)mrdemon said:
or want to stay out for 30 laps and do 140mph on the straights lap after lap
Indeed, how cretinous to attend a trackday and use your car to it's maximum potential . . . .mrdemon said:
I just think Alcon is not the easy fix as people make out , there are loads of pics of cracks disks on the net with them as people stay out longer.
Apparently not.mrdemon said:
people did ok on oem for years and mk1 GT3 owners have even less brake performace.
Do your homework. You'll find the Mk1 was the car that PF designed improved floating discs for, others companies followed. Logic would tend to indicate that the performance of the brakes (on track) of the earlier, lower powered cars was acceptable with just uprated pads. As the cars got more powerful and heavier and ran wider, sticker rubber, the performance of their brakes on track was found wanting. As a result, just upgrading pads, fluid and lines didn't provide sufficient long term durability. mrdemon said:
swings and roundabouts it seems regarding life and cost.
seriously ? ? Who'd have thought it ?PHOENIXUK said:
I used to use Alcon's and RS29's. Good but expensive and discs did crack. Now use the oem discs with Ferodo DS pads, the discs last a good year of track days the pads are similar wearing to the RS29's stop just as well (IMHO) and you dont get the horrible screeching, which is a real pain on the road.
What's the dust like with those? I've been using Hawk blues which I love the performance of but have a down side in that the dust is very nasty - has to cleaned off asap otherwise it will bake on to the rims if it gets wet. So looking for a more friendly alternative.boxsey said:
What's the dust like with those? I've been using Hawk blues which I love the performance of but have a down side in that the dust is very nasty - has to cleaned off asap otherwise it will bake on to the rims if it gets wet. So looking for a more friendly alternative.
Depends on which DS pads we're referring to. The DS2500 will produce dust but it's not damaging to wheels or bodywork. The dust from the DS3000 has the same effect as those you've described for the Hawk pads. The DS300 is a fantastic compound though. RS29s whilst not cheap, provide superb performance and the dust they produce (often a reddish/brown colour) is easy to remove and in my experience doesn't harm wheels or bodywork.
Output Flange said:
I trashed a set of powdercoated alloys with the dust from a set of RS29s.
Tell us more Dan 
How did attempt to clean them, how long had you left the dust on them, did it get wet, were the wheels decently powder coated etc, etc.
I ran them with PF discs on the front of my CSL in all weathers for three years and 30K miles without any issues. Whilst I accept there's always an exception to the rule, we need some more info before passing judgement.
Slippydiff said:
How did attempt to clean them
Tried all sorts, wouldn't budge.Slippydiff said:
how long had you left the dust on them
The day after a trackdaySlippydiff said:
did it get wet
Not until I washed them 
Slippydiff said:
were the wheels decently powder coated etc, etc.
Define "decently powdercoated" - certainly had no issues with the finish otherwise.Slippydiff said:
Whilst I accept there's always an exception to the rule, we need some more info before passing judgement.
Your comments are the first time I've seen someone say that the dust isn't an issue - they create a fair amount of it, and it needs regular cleaning. The wheels above would end up almost entirely black after a trackday, and that's as clean as they'd get. To be fair, they never got any worse than that for permanent marking.IMO the pads are worth it and I certainly wouldn't hesitate to get them again.
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