centrifugal clutch VS. disc clutch

93notch408

New member
i never had a disc clutch and wanna switch on my drag bike...i was looking on like but cant find no comparison's i was just wanting to kno the pro's and cons of each...people say if i switch to a disc my bike will gain mph and get up in the rpms quicker is this true?
 

XXX#40

Member
i have a noram star clutch no disc
The Noram and a disc clutch are both Centrifugal clutches.
Not many 1 inch shaft size disc clutches.
The disc may be a little more adjustable, but my guess is you wont see a big difference between the 2 in your application, the disc will need more attention
 

W5R

New member
Both style clutches are centrifugal clutches, as they spin up and gain momentum, they lock up and engage. Bikes do not have disc clutches in them, bikes use a series of friction plates in them that are similar to a clutch disc but not the same. You wont gain mph by switching to a disc clutch, but you will gain some acceleration and your clutch wont get hot as easy or as much as it would with a shoe type clutch. A disc clutch works like this, you have the friction discs, springs, and levers....when the clutch is spinning the levers are thrown outwards which in turn compresses the springs equally, which in turn puts pressure on the discs and locks the discs to the pressure plates or floaters. When the clutch is slipping, the levers dont have enough pressure on the springs yet to compress the discs, so you adjust the engagement a little to make it engage sooner and slip less. When you get to the point where the discs are almost worn out, it will slip at lower rpm's than normal and wont lock up as good, which means its time for a rebuild/refresh of the clutch.

A shoe clutch sort of works the same way, except as the engine spins the clutch up, the shoes start pulling outwards toward the drum until they are locked up to the drum. The drum serves as your pressure plate and the shoes serve as your friction discs if you were to compare a shoe clutch to a disc clutch. With a shoe clutch, instead of turning a screw or adjusting spring height to raise or lower rpm engagement of the clutch, you would change the springs instead. Different spring tensions give you different rpm engagements, which is usually determined by the color of the springs, which varys by different clutch manufacturers.

Hope this helps tell you what your wanting to know, im no expert on clutches but i dont mind sharing what iv learned if it will help someone else learn a thing or two.
 

XXX#40

Member
Both style clutches are centrifugal clutches, as they spin up and gain momentum, they lock up and engage. Bikes do not have disc clutches in them, bikes use a series of friction plates in them that are similar to a clutch disc but not the same. You wont gain mph by switching to a disc clutch, but you will gain some acceleration and your clutch wont get hot as easy or as much as it would with a shoe type clutch. A disc clutch works like this, you have the friction discs, springs, and levers....when the clutch is spinning the levers are thrown outwards which in turn compresses the springs equally, which in turn puts pressure on the discs and locks the discs to the pressure plates or floaters. When the clutch is slipping, the levers dont have enough pressure on the springs yet to compress the discs, so you adjust the engagement a little to make it engage sooner and slip less. When you get to the point where the discs are almost worn out, it will slip at lower rpm's than normal and wont lock up as good, which means its time for a rebuild/refresh of the clutch.

A shoe clutch sort of works the same way, except as the engine spins the clutch up, the shoes start pulling outwards toward the drum until they are locked up to the drum. The drum serves as your pressure plate and the shoes serve as your friction discs if you were to compare a shoe clutch to a disc clutch. With a shoe clutch, instead of turning a screw or adjusting spring height to raise or lower rpm engagement of the clutch, you would change the springs instead. Different spring tensions give you different rpm engagements, which is usually determined by the color of the springs, which varys by different clutch manufacturers.

Hope this helps tell you what your wanting to know, im no expert on clutches but i dont mind sharing what iv learned if it will help someone else learn a thing or two.
Yeah must be an echo in here, yes bikes do have disc clutches
If both are set up properly there will be no difference between the two.
 

93notch408

New member
yea i kno all about the shoe clutchs i guess that what there called i had to tune mine to where i wanted it to stall at...thx for the info hopefully someone reads your post and learns about both...i wanna get a disc clutch im sick of my over slipping it sux ..
Both style clutches are centrifugal clutches, as they spin up and gain momentum, they lock up and engage. Bikes do not have disc clutches in them, bikes use a series of friction plates in them that are similar to a clutch disc but not the same. You wont gain mph by switching to a disc clutch, but you will gain some acceleration and your clutch wont get hot as easy or as much as it would with a shoe type clutch. A disc clutch works like this, you have the friction discs, springs, and levers....when the clutch is spinning the levers are thrown outwards which in turn compresses the springs equally, which in turn puts pressure on the discs and locks the discs to the pressure plates or floaters. When the clutch is slipping, the levers dont have enough pressure on the springs yet to compress the discs, so you adjust the engagement a little to make it engage sooner and slip less. When you get to the point where the discs are almost worn out, it will slip at lower rpm's than normal and wont lock up as good, which means its time for a rebuild/refresh of the clutch.

A shoe clutch sort of works the same way, except as the engine spins the clutch up, the shoes start pulling outwards toward the drum until they are locked up to the drum. The drum serves as your pressure plate and the shoes serve as your friction discs if you were to compare a shoe clutch to a disc clutch. With a shoe clutch, instead of turning a screw or adjusting spring height to raise or lower rpm engagement of the clutch, you would change the springs instead. Different spring tensions give you different rpm engagements, which is usually determined by the color of the springs, which varys by different clutch manufacturers.

Hope this helps tell you what your wanting to know, im no expert on clutches but i dont mind sharing what iv learned if it will help someone else learn a thing or two.
 

93notch408

New member
Yeah must be an echo in here, yes bikes do have disc clutches
If both are set up properly there will be no difference between the two.
my clutch is setup perfectly but the way the shoe clutchs work they slip too much and the dick clutchs grab and dont have that slip i seen a big diff in my friends bike from his shoe clutch to a disc felt like a whole diff bike and picked the tire up off the ground didn't do that before lol
 

XXX#40

Member
my clutch is setup perfectly but the way the shoe clutchs work they slip too much and the dick clutchs grab and dont have that slip i seen a big diff in my friends bike from his shoe clutch to a disc felt like a whole diff bike and picked the tire up off the ground didn't do that before lol
Has the drum been blueprinted?
If its slipping something is wrong, have the shoes been milled? how old is the drum? is the drum a stamped drum or a machined drum?
Are the springs matched? how new are the springs?
Remember a clutch that grabs and pulls the front tire up is wasting energy, there has to be a little slipping, if not it can and will kill rpm's when it engages
 
Too, in low HP applications I've seen disc clutches lock in so hard and quickly that they throw the engine rpm's below the engine's peak torque. Maintaining that range can often be found easier with a drum clutch or the Vortex disc. You may at times feel the clutch is slipping too long when in fact it is a benefit. JMHO. -Alan-
 

93notch408

New member
my motor is not a low power app tho it should be in the 40 hp range 95mm piston welded block big valve head high comp
 

W5R

New member
Yeah must be an echo in here, yes bikes do have disc clutches
If both are set up properly there will be no difference between the two.
Iv worked on motorcycles and atv's all my life, they do not have the same type of discs like a disc clutch for a kart uses, they have a series of friction plates not discs, and they are a wet type clutch instead of a dry clutch like karts use. It is a whole different type of setup, similar yes but not the same like you are saying it is. Not trying to argue with you, just dont want people thinking the disc clutchs in a bike is the same thing as the clutch on a kart. A clutch like the ones found in cars or trucks are more like the ones found on karts, same type of clutch and mechanics.
 

W5R

New member
my clutch is setup perfectly but the way the shoe clutchs work they slip too much and the dick clutchs grab and dont have that slip i seen a big diff in my friends bike from his shoe clutch to a disc felt like a whole diff bike and picked the tire up off the ground didn't do that before lol
If the clutch is over slipping then it is not set up perfectly, the shoe clutch should lock up just as good as a disc clutch would on your application, also when you upgrade the motor on your bike you also need to adjust the clutch to raise the rpm engagement so you can get the clutch to engage when the engine is at or close to peak torque. Your problem is probably that the clutch your using is trying to engage too soon and is engaging before the engine is at peak torque, meaning you arent in the powerband of the engine when the clutch locks up and it feels like you arent putting any power to the wheels or the ground. Shoe clutches can be set up to where they grab quick just like a disc clutch does, you might be able to use the bathroom scale trick to get your clutch set up for the right engagement for your engine. You can take a bathroom scale and place it between the front wheel of your minibike and a strong wall, and give short bursts of throttle for a few secs at a time but dont hold it wide open or you will burn up the clutch and overheat it. Do a pull, adjust the clutch some, then do another pull. Record how many pounds the scale reads after each adjustment you make, after you make a few adjustments you will start to get the picture. What your looking for is the adjustment that gives you the most pounds on the scale. Say your first pull that is your baseline gives you 20lbs, you tweak the engagement a little and then you get 15, that means you went the wrong way with the adjustment and you need to go the other direction with it, then you make another pull and its 25, so you make another adjustment and it drops to 22, your highest number was 25 so that was the setting where you made the most torque and thats where your clutch needs to be set. After doing the scale trick, take your clutch apart and clean it good, sand the shoes down good with sandpaper and remove any blueing or black you see on the shoes or inside the drum.

What i do is take my clutch apart after every night of racing and sand down the shoes and drum both, wipe both clean with wd40, then grease or oil the bearing or bushing in the clutch drum and reinstall the clutch on the engine. Your clutch could be slipping too much if it hasnt been cleaned in awhile also.
 

XXX#40

Member
Iv worked on motorcycles and atv's all my life, they do not have the same type of discs like a disc clutch for a kart uses, they have a series of friction plates not discs, and they are a wet type clutch instead of a dry clutch like karts use. It is a whole different type of setup, similar yes but not the same like you are saying it is. Not trying to argue with you, just dont want people thinking the disc clutchs in a bike is the same thing as the clutch on a kart. A clutch like the ones found in cars or trucks are more like the ones found on karts, same type of clutch and mechanics.
Yeah racing motorcross for many years, being involved in racing all my life, and my son raced a honda 400ex 4wheeler for a few years
Motorcycles have disc's
Look familiar?
http://www.motosport.com/dirtbike/WISECO-PERFORMANCE-CLUTCH-KIT
 
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