turbogrill Posted October 8, 2021 Report Share Posted October 8, 2021 (edited) Hi, Our throwout bearing failed completely with 1 hour to go. Besides shifting less is there anything we can do to avoid this happening again? Or is there anything a driver might be doing wrong? Or some other part causing it to fail? Is it the pressing/depressing causing wear or is it keep the clutch pedal floored that causes wear? It has maybe 7 races and a bunch of track days on it. Car is NC Miata. Do you replace yours as a maintenance items? Edited October 8, 2021 by turbogrill Quote Link to comment Share on other sites More sharing options...
Rodger Coan-Burningham Posted October 8, 2021 Report Share Posted October 8, 2021 I usually replace it when I have the transmission out. One thing you can do on a new bearing is pop the shield out of one side and put good grease in it and put the shield back on. There really shouldn’t be a lot of stress on that bearing in most cases. 1 Quote Link to comment Share on other sites More sharing options...
TKRiggs Posted October 8, 2021 Report Share Posted October 8, 2021 Similar to Rodger...we replace ours every 3 - 4 races. We also use a dry lubricant on the pivot points of the throw out and lever arm as well as the "shaft" the bearing rides/slides on. Quote Link to comment Share on other sites More sharing options...
TiredBirds Posted October 8, 2021 Report Share Posted October 8, 2021 We went with a hydraulic unit. (T5 behind a 305) Quote Link to comment Share on other sites More sharing options...
turbogrill Posted October 8, 2021 Author Report Share Posted October 8, 2021 (edited) Thanks! I also heard it could be due to a driver riding the clutch. How does a hydraulic help? Still a bearing that wears out? Maybe some clever cooling? Airflow thru that "clutch" compartment? PC fans? Edited October 8, 2021 by turbogrill Quote Link to comment Share on other sites More sharing options...
Grant Posted October 8, 2021 Report Share Posted October 8, 2021 (edited) We haven't had a problem with ours in ~100 hours of track use. We of course replaced the bearing with the OE unit when we first prepped the car, but haven't had the transmission out since. I can't recall if I put higher temp grease in it or not, but I sometimes do. On most cars I replace the throwout and pilot bearings with OE units every time I do a clutch. Any hydraulic pressure in the clutch line at high RPMs will absolutely kill a throwout bearing. Edited October 8, 2021 by Grant 3 Quote Link to comment Share on other sites More sharing options...
turbogrill Posted October 8, 2021 Author Report Share Posted October 8, 2021 37 minutes ago, Grant said: We haven't had a problem with ours in ~100 hours of track use. We of course replaced the bearing with the OE unit when we first prepped the car, but haven't had the transmission out since. I can't recall if I put higher temp grease in it or not, but I sometimes do. On most cars I replace the throwout and pilot bearings with OE units every time I do a clutch. Any hydraulic pressure in the clutch line at high RPMs will absolutely kill a throwout bearing. Thanks! Can there somehow be pressure in the clutch line without touching the pedal? Would a failed master/slave cause it? Or should I connect a pressure sensor in the clutch line to a device that sprays fartgas into their firesuits? Quote Link to comment Share on other sites More sharing options...
Team Infiniti Posted October 8, 2021 Report Share Posted October 8, 2021 15 minutes ago, turbogrill said: should I connect a pressure sensor in the clutch line to a device that sprays fartgas into their firesuits? Absolutely or a foot cam. Seriously, any residual pressure or aftermarket stuff (tolerance stack up) could be at fault. Quote Link to comment Share on other sites More sharing options...
turbogrill Posted October 8, 2021 Author Report Share Posted October 8, 2021 18 minutes ago, Team Infiniti said: Absolutely or a foot cam. Seriously, any residual pressure or aftermarket stuff (tolerance stack up) could be at fault. sometimes I want to add sensors EVERYWHERE 1 Quote Link to comment Share on other sites More sharing options...
MMiskoe Posted October 8, 2021 Report Share Posted October 8, 2021 NB Miata always seems to have a noisy throwout bearing so it gets replaced when the motor/trans are apart (which in that car is an aggravating frequency). NA Miata hasn't been apart in many hours of racing and hasn't been an issue. The only thing different between the two Miatas is the type of clutch, so I suspect that the NB clutch fingers are just slightly closer to the T-O bearing. There is also wear on the fingers of the NB car. Is this a clutch issue? Flywheel? Fork? Bellhousing? Could be any of those options. For what it's worth, we've never had a failure in either of the two tag karts that share the shop with the two Miatas. 2 Quote Link to comment Share on other sites More sharing options...
ETR Posted October 9, 2021 Report Share Posted October 9, 2021 Has the flywheel been resurfaced? If the same amount wasn’t removed from the pressure plate mounting surfaces it can have those fingers closer to the throw out bearing than they should be. Quote Link to comment Share on other sites More sharing options...
turbogrill Posted October 9, 2021 Author Report Share Posted October 9, 2021 1 hour ago, ETR said: Has the flywheel been resurfaced? If the same amount wasn’t removed from the pressure plate mounting surfaces it can have those fingers closer to the throw out bearing than they should be. hmm...I don't think so! Got a new one in and will hope for the best. Quote Link to comment Share on other sites More sharing options...
gundy Posted October 9, 2021 Report Share Posted October 9, 2021 is any part of that bearing plastic? Quote Link to comment Share on other sites More sharing options...
turbogrill Posted October 9, 2021 Author Report Share Posted October 9, 2021 58 minutes ago, gundy said: is any part of that bearing plastic? The inner side is, the one that slides back and forth Quote Link to comment Share on other sites More sharing options...
Wheelman_99 - C Rallo Posted October 9, 2021 Report Share Posted October 9, 2021 Do you have a clutch stop and is it adjusted properly? If you don't you might need one. 2 Quote Link to comment Share on other sites More sharing options...
TimS Posted October 11, 2021 Report Share Posted October 11, 2021 On 10/8/2021 at 2:05 PM, turbogrill said: Hi, Our throwout bearing failed completely with 1 hour to go. Besides shifting less is there anything we can do to avoid this happening again? Or is there anything a driver might be doing wrong? Or some other part causing it to fail? Is it the pressing/depressing causing wear or is it keep the clutch pedal floored that causes wear? It has maybe 7 races and a bunch of track days on it. Car is NC Miata. Do you replace yours as a maintenance items? Be sure no one is using clutch pedal as a foot rest. 2 Quote Link to comment Share on other sites More sharing options...
turbogrill Posted October 11, 2021 Author Report Share Posted October 11, 2021 4 minutes ago, TimS said: Be sure no one is using clutch pedal as a foot rest. I have heard this from 10 people now Sounds like a likely issue.. 1 Quote Link to comment Share on other sites More sharing options...
mender Posted October 11, 2021 Report Share Posted October 11, 2021 Make sure you have a dead pedal that is well placed. 1 Quote Link to comment Share on other sites More sharing options...
ManhattanMcC Posted October 11, 2021 Report Share Posted October 11, 2021 2 hours ago, TimS said: Be sure no one is using clutch pedal as a foot rest. Oh! Oh! I resemble that comment... (Lessons learned when you wear size 14's...) 1 Quote Link to comment Share on other sites More sharing options...
turbogrill Posted October 11, 2021 Author Report Share Posted October 11, 2021 I like the fart gas into driver suit alarm better 2 Quote Link to comment Share on other sites More sharing options...
TiredBirds Posted October 13, 2021 Report Share Posted October 13, 2021 On 10/8/2021 at 3:02 PM, turbogrill said: Thanks! I also heard it could be due to a driver riding the clutch. How does a hydraulic help? Still a bearing that wears out? Maybe some clever cooling? Airflow thru that "clutch" compartment? PC fans? No idea how it helps, the guy on our team that knows racing said to get one, so we did.... 2 Quote Link to comment Share on other sites More sharing options...
mender Posted October 16, 2021 Report Share Posted October 16, 2021 On 10/13/2021 at 9:20 AM, TiredBirds said: No idea how it helps, the guy on our team that knows racing said to get one, so we did.... "High performance hydraulic release bearings are “constant contact” types that provide quick clutch response. You will need to set a small operating clearance between the bearing and the pressure plate. Once you have the bearing properly adjusted for clearance, it will self-adjust for wear. That’s because there is no return spring required to pull the bearing’s piston back to the bottomed position. The piston within the assembly functions much like the piston in a brake caliper. Clutch pedal feel remains the same as the bearing wears, too." Quote Link to comment Share on other sites More sharing options...
TiredBirds Posted October 16, 2021 Report Share Posted October 16, 2021 1 hour ago, mender said: "High performance hydraulic release bearings are “constant contact” types that provide quick clutch response. You will need to set a small operating clearance between the bearing and the pressure plate. Once you have the bearing properly adjusted for clearance, it will self-adjust for wear. That’s because there is no return spring required to pull the bearing’s piston back to the bottomed position. The piston within the assembly functions much like the piston in a brake caliper. Clutch pedal feel remains the same as the bearing wears, too." lol thanks...All I know it works. Quote Link to comment Share on other sites More sharing options...
Wheelman_99 - C Rallo Posted October 16, 2021 Report Share Posted October 16, 2021 Oh and check for free okay in the clutch actuation system. Quote Link to comment Share on other sites More sharing options...
turbogrill Posted October 17, 2021 Author Report Share Posted October 17, 2021 As far as I know there is no off the shelf hydraulic bearing for the Miatas. It's probably not needed unless you happened to be a part of a endurance racing team consisting of neanderthals. Are these typically aftermarket units that can easily be adapted? One less thing that can fail is a good thing. Quote Link to comment Share on other sites More sharing options...
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