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Thread: Stoptech ST-40 kit failures?

  1. #1

    Stoptech ST-40 kit failures?

    I've been running the ST-40 kit for 4 full seasons and 45-50 race weekends. Swapped rotors but otherwise haven't done a thing other than fluid bleeds. I inquired about a piston rebuild kit and was asked "why". I'm not having any problems but with this much use I'm getting concerned about a failure. Has anyone had a failure or used them well past 50 weekends (100 days, 500 "sessions")?

  2. #2
    Senior Member Carroll Shelby michaelmosty's Avatar
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    I have had mine for about 8 years and average about 6 events / year so at about the same 50 race weekends as you are. I as well have done nothing except bleed fluid and swap rotors. I am on my 3rd set of rotors but have changed out all previous pairs for preventative reasons.

    The only issue I have seen others have is the hardware elongating the holes on the ring. I have seen this in a previous set of mine as well but did not have a failure.
    -Michael Mosty
    CMC2 #11 "Mosty Brothers' Racing"
    2011 TX Region - CMC2 Champion

  3. #3
    Senior Member Carroll Shelby
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    Who did you inquire with that said why?
    Bryan Leinart
    CMC #24

  4. #4
    Senior Member Grass-Passer Casey_SS's Avatar
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    Mine have been awesome. Got 'em used, raced them for two or three years, replaced the seals at some point after that which was at least 4 years ago, probably longer. I'll replace them again at some point just for peace of mind but I've had no issues to speak of...probably the most reliable part on the whole car.

    The closest thing to a "failure" I've seen was Mike P. and Marshall each had a caliper start leaking a few years apart from each other. Mike's was from a piston seal which he replaced at the track and carried on, I don't remember what the source of Marshall's leak was. They can chime in with the details but I don't recall either situation being very dramatic.

    That being said, the piston seals are like $10 each and fairly easy to swap out. There's no harm in replacing them periodically. Don't bother with the dust boots though. They just disintegrate by the 2nd or 3rd race.
    2012 NASA-TX American Iron Champ
    AI #29

  5. #5
    Senior Member Grass-Passer MikeP99Z's Avatar
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    I had 2 different sets of ST-40s on my car from 2005 through 2017. The first set lost a piston seal, was replaced, no issues. That same set took damage during an accident, hence I purchased a new pair of calipers and a bracket. The second set had a replacement seal after a few years (track fix referenced above), and had a leaking bridge line - suspected to have been damaged from the wheel contacting the caliper following a broken ball joint. All repaired, but lost another seal a year later.

    I moved to an AP Racing kit in 2017 when I upgraded to 14" rotors.

  6. #6
    Senior Member Carroll Shelby
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    When I got a used set from Matt he provided fresh seals/boots, so I immediately re sealed them

    I would invest in a spare bridge line and ditch the bleeder screws for the two piece wilwood units so you don't wear out the screw holes in the calipers over time.

    I think doing fresh seals and inspecting your pistons and bores is a good move but other than the bridge line, seals, and bleed screws, I don't imagine anything else being a long term issue on the calipers themselves

    I made the investment in a spare hat and hardware, and keep some old rotor rings in case those break/crack or something.

    Zeckhausen is a great source for the stop tech parts, he will get you set up
    Last edited by Pranav; 02-09-2019 at 12:48 PM.

  7. #7
    Glad to hear how stable these things have been. I haven't done a thing, not seals, nothing.

    There's a shop in NC that stocks/sells alot of kits and when I called him months ago asking about rebuild kits he said he'd never sold a rebuild kit/seals before. It was mid-season so I just forgot about it.......now I'm thinking I need to do something with these calipers.

  8. #8
    Senior Member Carroll Shelby
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    Quote Originally Posted by t500hps View Post
    Glad to hear how stable these things have been. I haven't done a thing, not seals, nothing.

    There's a shop in NC that stocks/sells alot of kits and when I called him months ago asking about rebuild kits he said he'd never sold a rebuild kit/seals before. It was mid-season so I just forgot about it.......now I'm thinking I need to do something with these calipers.
    Dave Zeckhausen has all the Stoptech replacment parts you need and is one top notch seller. We typically do seal kits every 3 or 4 seasons which for Misty, myself and Martin Cain typically included 4 to 6 race weekends and 10 to 15 DE weekends per year. Main issue is to make sure pistons still move freely and don't bind up in the seal from dirt. Calipers if not damaged by accidents are bomb proof. rotor hats can wear due to faulty hardware but not common. Have used many sets over the years. would buy again.
    To hell with the rules, the guidelines and the politics....built the car to my wishes and having fun being the underdog running with the Wolves!

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