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Brake pedal travel and feel - 997.1 GT3RS

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Old 05-15-2024 | 01:30 PM
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Default Brake pedal travel and feel - 997.1 GT3RS

I am noticing greater pedal travel before engagement than I remember feeling.

Brake system is stock steel rotors, rubber brake lines, currently running Ferodo DS 3.12 which have plenty of meat left on them. Brake fluid is fresh ATE Typ 200 (I am OCD about the fluids in general).

At the top of the stroke the travel appears to have increased. Once I encounter resistance while pressing the brake pedal the response is the same linear feel I've always appreciated, all the way to the pedal stop.

Highly subjective, I know, but how would you describe the brake pedal feel on your 997.1 GT3 (RS).

Also if anyone is coming to my GT-car GTG on Sunday would you let me try out how your brake pedal feels?

Thanks,

/alex
Old 05-15-2024 | 01:53 PM
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Have you tried to pump your brakes one time before you lay into them? If not try that and see if the pedal firms up on second initial descent. If so, you could have the teeeniest bit of air in the system. Also, who bleeds the system? You? Shop?

Always remember to bleed the outer bleeder valves first.
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Old 05-15-2024 | 02:07 PM
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bleed brakes. inspect for leaks at calipers. inspect master for leaks. Get your head up in the pedal well and pull the panel covers in the frunk and check.

997 probably has one of the best brake pedal feels, assuming you're using a good pad (I have not use the ferodo ds 3.12 before) you should have a very firm and progressive pedal.

It could be some air.

Type 200 isn't a really great high temp fluid (I use it on my older cars). you could try endless or the castrol one or the high temp motul.
Old 05-15-2024 | 02:28 PM
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Originally Posted by RAudi Driver
Have you tried to pump your brakes one time before you lay into them? If not try that and see if the pedal firms up on second initial descent. If so, you could have the teeeniest bit of air in the system. Also, who bleeds the system? You? Shop?

Always remember to bleed the outer bleeder valves first.
I have not tried but I will. I bleed the brakes myself the old-fashioned way (pumping the pedal but only about 1/2 stroke) with a tube with 1-way valve attached to the bleeder nipple. I do tap the calipers with a rubber mallet before opening the bleed nipples just to dislodge any errant bubbles. I have been doing it the same way for a long time. My reference comparison is my 993 with the non-turbo brakes and stainless steel lines which has an awesome, confidence-inspiring pedal feel - very firm.

What is the basis for your statement that the outboard sections on each caliper should be bled first?

Originally Posted by Spyerx
bleed brakes. inspect for leaks at calipers. inspect master for leaks. Get your head up in the pedal well and pull the panel covers in the frunk and check.

997 probably has one of the best brake pedal feels, assuming you're using a good pad (I have not use the ferodo ds 3.12 before) you should have a very firm and progressive pedal.

It could be some air.

Type 200 isn't a really great high temp fluid (I use it on my older cars). you could try endless or the castrol one or the high temp motul.
Thanks, I am pretty sure no air and no leaks around the calipers - I take it you are referring to the areas around the bleeder nipples not around the pistons themselves? I haven't checked the MC; are you saying that is upper reaches of the footwell?
Old 05-15-2024 | 02:46 PM
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Also re. Typ 200 - I don't think this is the culprit as it is pretty fresh, hasn't seen any really elevated temps on a sustained basis and the behavior I am describing occurs when the brakes are relatively cold, as opposed to the pedal softening when the brakes are very hot.
Old 05-15-2024 | 04:32 PM
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Alex, top of the stroke travel means the pistons have to travel further to contact the rotor surface. I would check for runout (either rotor or bearing related). If that isn’t the case perhaps the seals are wearing and drawing the pistons further back into the caliper.
does this happen for every pedal stroke or only after some cornering/bumps?
Old 05-15-2024 | 05:02 PM
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Originally Posted by 00 Scrub
Alex, top of the stroke travel means the pistons have to travel further to contact the rotor surface. I would check for runout (either rotor or bearing related). If that isn’t the case perhaps the seals are wearing and drawing the pistons further back into the caliper.
does this happen for every pedal stroke or only after some cornering/bumps?
Thanks for the insights Nehal, This behavior happens on every stroke
Old 05-15-2024 | 05:10 PM
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Originally Posted by ard

What is the basis for your statement that the outboard sections on each caliper should be bled first?
The Manual.



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Old 05-15-2024 | 06:08 PM
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I highly recommend using a Motive Pressure bleeder (I like the dry method) for a one man brake bleed job. In addition to what @RAudi Driver instructions mention, make sure to bleed in the following sequence:
  1. rear right (pass)
  2. rear left (driver)
  3. front right (pass)
  4. front left (driver)
Add the Image below for additional tips in BLUE



Last edited by Clifton; 05-15-2024 at 06:29 PM. Reason: added content
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Old 05-15-2024 | 06:28 PM
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Alex, one other thing to consider. If you are comparing this to the dead zone of a 993 do they have the same ratio of MC area to caliper piston area? If that changes you will get a different amount of pedal stroke to achieve initial pad contact since the required volume displacement will change.
Old 05-15-2024 | 07:34 PM
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The brake pedal in my 997.1 GT3 RS is very stiff with minimal travel - and this is with stock pads and fluid. By far the stiffest brake pedal I've used, if there's a noticeable amount of travel it's definitely deserving of investigation and bleeding the system. I believe there is a 'thorough' bleed process using PIWIS to actuate the ABS system, which cannot be done with your typical Motiv brake bleeding exercise. You may consider taking to the dealer or indy with PIWIS if you've recently bled the brakes and still having soft pedal.

Last edited by cstyles; 05-15-2024 at 07:36 PM.
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ard (05-15-2024)
Old 05-16-2024 | 01:15 AM
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Always bleed outer nipple first. Fluid enters the caliper from the inner side and transfers to the outer side via the bridge line. Thus, any air that enters the caliper during the bleeding process will rise and stay on the inner side, hence you wanna bleed the inner nipple last.

Also check your MC. I have had a MC seal on one go bad after several yeas of heavy track use which resulted in a soft pedal. This is easy to check. Apply pressure to the brake pedal and you should come to a firm stop. Keep pressure applied. If the pedal begins to sink lower than fluid is bypassing the seal. If the seal is good, your brake pedal will not sink lower.
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Old 05-16-2024 | 11:21 AM
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if the issue was pad knock back the pedal would only be soft after driving a bit. I've never experienced this on my 997. I have experienced it with the factory uprights on my 964.
Old 05-23-2024 | 02:01 PM
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Alex, were you able to compare your pedal free play to another car at last weekends meet? Let me know if you want to borrow my Motiv and try bleeding the system that way.



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