Clutches: The Part, The Myth, The Legend
03-03-2009, 01:19 PM
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Clutches: The Part, The Myth, The Legend
After my latest clutch disaster, I have spent the better part of two days on the phone and the internet trying to find info on clutches. Specifically what clutch will hold up to a street/strip car making over 550-600ft*lbs. What I have found is very very few will. I will share what I have learned in case any of you start deciding to play in the 450-500ft*lbs range.
The modular motor guys talk about king cobras, centerforce, zoom, hays, spec, etc. Some of those guys are making good power, but not a bunch of torque, so their opinions are not very appropriate when finding a larger small block or even big block clutch.
Everyone I spoke with agrees that torque is what kills clutches, so a horsepower rating is useless in comparing clutches. You need to talk clamping force and torque.
There are three basic pressure plate styles. The long style (Ford), Borg & Beck (GM), and diaphragm. There are a ton of pressure plate different bolt patterns, so do not make the mistake I did and get a flywheel with just one bolt pattern. McLeod and several others make flywheels with various bolt patterns that will give you options.
Static clamping force is the measure of pressure plates. The largest long style most anyone makes is a 2400#. It requires a lot of leg, as this is what I drive. Some make a 2900# long style, but it is basically race only (pro-stock kind of stuff). The diaphragm pressure plate is easier to engage than the long style, so many companies make a streetable 2900# diaphragm. I cannot attest to the will it takes to push this pedal, but I have been told it is not bad. The long style pressure plate requires less pedal through to engage, so it is better for fast shifting. The two are a compromise. The Borg & Beck is basically a GM design and is very similar to the long style but has some rollers. Some pressure plates have weights that will aid in clamping force as rpms increase. Centerforce pressure plates are built on this design, but several other people make similar stuff. They are diaphragm pressure plates with some tricks.
What I have learned is there are a ton of different clutch discs out there. I relate them to spark plugs in that everyone has their gimmick that they push. Clutches basically have two surfaces (flywheel and pressure plate). Surface materials can be various things. Organic, Bronze, Kevlar, Iron, etc. In general, the organic discs are stock type discs that hold the least pressure. They are also a little more forgiving and will slip a little. The Bronze are generally more aggressive and bite hard. Iron is for high horsepower endurance type stuff. Kevlar is for high performance street applications. Clutches also have a hub. Street clutches have spring loaded hubs that allow for some give when the clutch bites, so there is not a shock to the drive train. Racing clutches often have solid hubs so they are more harsh and are basically on or off. There is a type of clutch system that uses two clutch discs with a floater plate in between. Top fuel drag cars use something similar and is a way to get some initial slip but still hold a bunch of power.
Now the legend part. I called Hays, Centerforce, and McLeod to see what their torque ratings were for the various clutches we all hear about. I have not heard back from McLeod, so I will have to post their stuff later, but here is what Centerforce and Hays said.
Centerforce
Centerforce I clutch systems are designed for 30% more force than stock applications. That puts these clutches in the 350-380ft*lbs range.
Centerforce II clutch systems are designed for 60% more force than stock applications. That puts these clutches in the 450ft*lbs range.
Centerforce Dual Friction is designed for up to 600ft*lbs.
Centerforce DFX is not available yet in many applications like Detroit V8 stuff.
Comments: Centerforce told me they target the street guys. They cannot handle big block and big torque stuff and do not try to, even though they do sell product that would fit. General impressions were that they are great for 5.0 guys, but much above that they are over their head in torque. They do have a centrifugal clamp pressure plate system that helps clamping at high rpms, so it is good for spinning, but not good for down low torque.
Hays
55 Series Street clutch is what I slipped so bad that I could barely get home. They are rated for stock applications up to 350 ft*lbs.
40 Series Street/Strip is what I just blew up. They are rated for lite performance up to 500ft*lbs and is generally pretty streetable.
49 Series Race clutch is still a spring hub clutch but it lacks the marcel spring. It is rated for 500-600ft*lbs but is not going to be very nice on the street because it is missing the marcel spring.
McLeod
Hopefully more to come soon.
I did not call Zoom or Spec, but based on their website info both fall in line with Centerforce on their ratings. Stage I is basically stock. Stage II is warmed up. Stage III is getting to be a real engine, Stage IV is street/strip. Neither appear to really make a big torque rated clutch.
My thoughts are that I am still with out a clutch, but I hope I have answered some questions for the the classic mustang performance guys. If I made any mistakes, but call me on it. I am still learning and just trying to relay info that I have found very hard to collect. The Centerforce DF might work for me, but if I improve anything at all, I will be under clutched again. Both the Centerforce and Hays guys were very nice and basically said we cannot really help you...I did get good feelings from them, so if you can make use of their product, I think you will find them very helpful in narrowing down a system for you.
Closing thoughts: Why do clutch guys not make clutches for torquer motors? What happened to the hotroders???
The modular motor guys talk about king cobras, centerforce, zoom, hays, spec, etc. Some of those guys are making good power, but not a bunch of torque, so their opinions are not very appropriate when finding a larger small block or even big block clutch.
Everyone I spoke with agrees that torque is what kills clutches, so a horsepower rating is useless in comparing clutches. You need to talk clamping force and torque.
There are three basic pressure plate styles. The long style (Ford), Borg & Beck (GM), and diaphragm. There are a ton of pressure plate different bolt patterns, so do not make the mistake I did and get a flywheel with just one bolt pattern. McLeod and several others make flywheels with various bolt patterns that will give you options.
Static clamping force is the measure of pressure plates. The largest long style most anyone makes is a 2400#. It requires a lot of leg, as this is what I drive. Some make a 2900# long style, but it is basically race only (pro-stock kind of stuff). The diaphragm pressure plate is easier to engage than the long style, so many companies make a streetable 2900# diaphragm. I cannot attest to the will it takes to push this pedal, but I have been told it is not bad. The long style pressure plate requires less pedal through to engage, so it is better for fast shifting. The two are a compromise. The Borg & Beck is basically a GM design and is very similar to the long style but has some rollers. Some pressure plates have weights that will aid in clamping force as rpms increase. Centerforce pressure plates are built on this design, but several other people make similar stuff. They are diaphragm pressure plates with some tricks.
What I have learned is there are a ton of different clutch discs out there. I relate them to spark plugs in that everyone has their gimmick that they push. Clutches basically have two surfaces (flywheel and pressure plate). Surface materials can be various things. Organic, Bronze, Kevlar, Iron, etc. In general, the organic discs are stock type discs that hold the least pressure. They are also a little more forgiving and will slip a little. The Bronze are generally more aggressive and bite hard. Iron is for high horsepower endurance type stuff. Kevlar is for high performance street applications. Clutches also have a hub. Street clutches have spring loaded hubs that allow for some give when the clutch bites, so there is not a shock to the drive train. Racing clutches often have solid hubs so they are more harsh and are basically on or off. There is a type of clutch system that uses two clutch discs with a floater plate in between. Top fuel drag cars use something similar and is a way to get some initial slip but still hold a bunch of power.
Now the legend part. I called Hays, Centerforce, and McLeod to see what their torque ratings were for the various clutches we all hear about. I have not heard back from McLeod, so I will have to post their stuff later, but here is what Centerforce and Hays said.
Centerforce
Centerforce I clutch systems are designed for 30% more force than stock applications. That puts these clutches in the 350-380ft*lbs range.
Centerforce II clutch systems are designed for 60% more force than stock applications. That puts these clutches in the 450ft*lbs range.
Centerforce Dual Friction is designed for up to 600ft*lbs.
Centerforce DFX is not available yet in many applications like Detroit V8 stuff.
Comments: Centerforce told me they target the street guys. They cannot handle big block and big torque stuff and do not try to, even though they do sell product that would fit. General impressions were that they are great for 5.0 guys, but much above that they are over their head in torque. They do have a centrifugal clamp pressure plate system that helps clamping at high rpms, so it is good for spinning, but not good for down low torque.
Hays
55 Series Street clutch is what I slipped so bad that I could barely get home. They are rated for stock applications up to 350 ft*lbs.
40 Series Street/Strip is what I just blew up. They are rated for lite performance up to 500ft*lbs and is generally pretty streetable.
49 Series Race clutch is still a spring hub clutch but it lacks the marcel spring. It is rated for 500-600ft*lbs but is not going to be very nice on the street because it is missing the marcel spring.
McLeod
Hopefully more to come soon.
I did not call Zoom or Spec, but based on their website info both fall in line with Centerforce on their ratings. Stage I is basically stock. Stage II is warmed up. Stage III is getting to be a real engine, Stage IV is street/strip. Neither appear to really make a big torque rated clutch.
My thoughts are that I am still with out a clutch, but I hope I have answered some questions for the the classic mustang performance guys. If I made any mistakes, but call me on it. I am still learning and just trying to relay info that I have found very hard to collect. The Centerforce DF might work for me, but if I improve anything at all, I will be under clutched again. Both the Centerforce and Hays guys were very nice and basically said we cannot really help you...I did get good feelings from them, so if you can make use of their product, I think you will find them very helpful in narrowing down a system for you.
Closing thoughts: Why do clutch guys not make clutches for torquer motors? What happened to the hotroders???
03-03-2009, 02:39 PM
#3
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700-800hp is not a big deal with relation to the clutch if you are spinning up to 8500rpm b/c you are not playing with that much torque. If you are going to aim for 700-800hp in the 5000rpm range, then you are definitely going to have clutch issues. Like I said above. Torque, not necessarily horsepower, kills clutches. Wheel pulling toque monsters eat clutches for breakfast. I am learning that is one reason why my drag buddies run torque converter automatics. I think they handle the low end toque a little easier.
03-03-2009, 03:45 PM
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I just spoke with McLeod. Also very very nice guys! Here is what they had to say:
All of their race clutches (with and without sprung hubs) are flat (no marcel spring), so they are unstreetable. Sounds like they are on or off and will chatter when engaging disengaging which is not a good thing on the u joints, rearend, etc.
Their street clutches are:
100 series Organic surface and are basically nicer stock clutches.
500 series Bronze Button and Organic surface will hold about 450ft*lbs
800 series Kevlar Organic will hold about 550ft*lbs in an 11" and 600ft*lbs in a 12"
RST dual clutch system (uses standard flywheel) with organic surface is rated for about 800ft*lbs and is intended for more street use
RXT dual clutch system (uses standard flywheel) with Bronze surface is rated for abut 1000ft*lbs and is intended to handle the strip abuse
Street Twin dual clutch system (includes flywheel) is intended for up to 1200ft*lbs with modifications available for even more!
Their RST/RXT pressure plates have multiple bolt patterns, so matching up a flywheel to them is easy, which is not the case in most manufacturers. I told the McLeod gentleman (he may have been McLeod) that no one makes a clutch that will work for me. He said that is why he made the RST/RXT. He said single clutch systems just top out in the 500ft*lbs range and race clutches are just too harsh. That is the perk of a dual clutch system.
He mentioned Ram as having something similar to the RST/RXT, but after all of his help I do not think I would buy a clutch from anyone else. I will check them out though and report back.
All of their race clutches (with and without sprung hubs) are flat (no marcel spring), so they are unstreetable. Sounds like they are on or off and will chatter when engaging disengaging which is not a good thing on the u joints, rearend, etc.
Their street clutches are:
100 series Organic surface and are basically nicer stock clutches.
500 series Bronze Button and Organic surface will hold about 450ft*lbs
800 series Kevlar Organic will hold about 550ft*lbs in an 11" and 600ft*lbs in a 12"
RST dual clutch system (uses standard flywheel) with organic surface is rated for about 800ft*lbs and is intended for more street use
RXT dual clutch system (uses standard flywheel) with Bronze surface is rated for abut 1000ft*lbs and is intended to handle the strip abuse
Street Twin dual clutch system (includes flywheel) is intended for up to 1200ft*lbs with modifications available for even more!
Their RST/RXT pressure plates have multiple bolt patterns, so matching up a flywheel to them is easy, which is not the case in most manufacturers. I told the McLeod gentleman (he may have been McLeod) that no one makes a clutch that will work for me. He said that is why he made the RST/RXT. He said single clutch systems just top out in the 500ft*lbs range and race clutches are just too harsh. That is the perk of a dual clutch system.
He mentioned Ram as having something similar to the RST/RXT, but after all of his help I do not think I would buy a clutch from anyone else. I will check them out though and report back.
Last edited by urban_cowboy; 03-03-2009 at 03:48 PM.
03-03-2009, 05:04 PM
#9
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Ram clutches break down like this
HDX 200 are basically warmed up stock clutches with surface meterial being organic that will handle around 450ft*lbs
Competition 300 are available in race and street hub (with and W/O marcel spring) and are capable of handling about 500ft*lbs
Powergrip 300/900 are mid range clutches with surface material being organic metallic that will handle around 550ft*lbs. They are a sprund hub with marcel, so are still very streetable.
Powergrip 900 HD are their full metallic clutches with surface material being sintered iron capable of handling around 650ft*lbs. They have a sprung hub and have a marcel, so they are streetable although the metallic surface material will chatter a little.
Rametallic 1000 and 6000 are 6 paddle discs available in sprung hubs w/o marcel and a flat hub config. They have a metallic surface material and are really race only clutches.
Street Dual is a dual clutch system with float plate (just like McLeod's street twin) with surface material with organic metal bonded (competition 300s w/o marcel) capable of handling 900 ft*lbs. The dual clutch configuration with floater plate helps with the harsh grabbing of the system, so marcel springs are not needed to be streetable. This package comes with aluminum flywheel and the entire package weighs 45lbs. Very nice. I believe you can upgrade to 900 series clutches if you need even more friction material.
It sounds like Ram matches up pretty well with McLeod. Ram may have a little more streetable high end single clutch system, where McLeod pushes you on to the dual system. They both have race clutches that are very similar that I did not talk about b/c they are solid hub on/off clutches that would be too harsh for the street.
Edit: Updated info after speaking with tech department.
HDX 200 are basically warmed up stock clutches with surface meterial being organic that will handle around 450ft*lbs
Competition 300 are available in race and street hub (with and W/O marcel spring) and are capable of handling about 500ft*lbs
Powergrip 300/900 are mid range clutches with surface material being organic metallic that will handle around 550ft*lbs. They are a sprund hub with marcel, so are still very streetable.
Powergrip 900 HD are their full metallic clutches with surface material being sintered iron capable of handling around 650ft*lbs. They have a sprung hub and have a marcel, so they are streetable although the metallic surface material will chatter a little.
Rametallic 1000 and 6000 are 6 paddle discs available in sprung hubs w/o marcel and a flat hub config. They have a metallic surface material and are really race only clutches.
Street Dual is a dual clutch system with float plate (just like McLeod's street twin) with surface material with organic metal bonded (competition 300s w/o marcel) capable of handling 900 ft*lbs. The dual clutch configuration with floater plate helps with the harsh grabbing of the system, so marcel springs are not needed to be streetable. This package comes with aluminum flywheel and the entire package weighs 45lbs. Very nice. I believe you can upgrade to 900 series clutches if you need even more friction material.
It sounds like Ram matches up pretty well with McLeod. Ram may have a little more streetable high end single clutch system, where McLeod pushes you on to the dual system. They both have race clutches that are very similar that I did not talk about b/c they are solid hub on/off clutches that would be too harsh for the street.
Edit: Updated info after speaking with tech department.
Last edited by urban_cowboy; 03-05-2009 at 09:15 AM.
03-03-2009, 05:10 PM
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Current thoughts:
Ram and McLeod are the real deal. I am not sure I would recommend anyone use anything else because they make something for everyone (stock to 900+ft*lbs)
There is a question in my mind as to how bad it would be to drive a clutch in traffic without a marcel spring but with a sprung hub...Something like the Ram 300 or 900 or McLeod Racing 300 or 400. They all have serious friction surface material, a sprung hub to help with engagement shock, but do not have a marcel spring for the complete streetability.
I will talk with David Kee later this week to see what he knows and report back.
Ram and McLeod are the real deal. I am not sure I would recommend anyone use anything else because they make something for everyone (stock to 900+ft*lbs)
There is a question in my mind as to how bad it would be to drive a clutch in traffic without a marcel spring but with a sprung hub...Something like the Ram 300 or 900 or McLeod Racing 300 or 400. They all have serious friction surface material, a sprung hub to help with engagement shock, but do not have a marcel spring for the complete streetability.
I will talk with David Kee later this week to see what he knows and report back.
