Clutch disengage linkage: Cable or hydraulic?

[RussMcB]

I'm pondering my new, yet to be designed clutch linkage. On the 2005 Kawasaki bike chassis, it was a single, simple cable arrangement. My f2000 race car had a clutch master/slave system.

I'm at a point where I can go either way. Anyone have any strong opinions about advantages or disadvantages of either?

TIA.

[Tom Sprecher]

I for one don't want to hear about it.

[rickjohnson356]

in ancient times (1968-70), my FVs used a cable for the clutch line. no real problems and less messy to maintain. don't have to bleed it etc.

having said that, all my other cars have had hydraulic. also with no problems

I would go with the easier method first, then change it if problems.

this kinda begs a question. there has been a lot of talk about only using the clutch to get going from a dead stop on the grid (or an off) with hewland/staffs/webster gearboxes

do the bike motors require using the clutch for each gear change?

[glenn cooper]

Well I will say this for cable op systems:
They tend to be there when you need them...

Countless times I have had hydraulic systems go soft, or go away.
I believe a lot of it has to do with the proper amount of slave cylinder travel (very small distance) needed for proper disengagement. Our car based mastercylinders pump way loads more fluid than a bike m/c. Trying to get this (small) travel (@ slave cylinder is critical.

Quite often it is a royal pain.

Cable systems are quite elegant in their simplicity, and less weight to boot.
A cable system never needs to be bled, never develops a leak, etc...

I've had a moment or 2 in hyd clutch cars where there was no pedal, when trying to engage 1st to leave the pre grid! By the time I shut down the engine, put it in 1st and hit the starter, 12 cars had gone by(e). Never woulda happened in a cable op'd sys.
(YEAH - I just said never. WHAT - You gonna do sumpthin' about it?)

So, to recap - Cable sys all the way. I have seen very nice cable systems made, utilizing the s/s clutch hydraulic line as a sheath. If it is made robust enough, it will give zero headaches. Properly limiting pedal travel (w/ a pedal stop) on either style can not be overlooked.

Recap II - If the bike motor came equiped w/ a cable system, take this as a sign from above to stay w/ that method of actuation.

G out

Recap III - Comment on above post.

And the answer is... NO.
No, you don't need the clutch for anything other than engaging first to leave the pre grid.
Bike gearbox's all have dog style engagement. Not exactly like a dog ring gearbox (Hewland, Staffs, etc...), but engagement dogs just the same.

Bottom Line? Non-synchro transmissions don't require the use of the clutch.
Synchro style (street car) does.

I was at Rd Atl earlier this year, (IMSA Lights, bike motor car) and a guy pulled in from the race and parked it. I walked over and asked him what/why he came in. He replied that the clutch went away. I asked him if it started slipping, to which he replied, No the clutch pedal went to the floor. I asked him if the clutch became dis-engaged, and he said no, the pedal just went dead.
Obviously this guy did not need to come in. The car was still quite driveable...

[RussMcB]

Thanks, Coop.

From all the opinions I've read about using the clutch during shifts, I had formed the opinion that clutching during downshifts might mean less wear & tear. When I'm riding my street bike, upshifts without the clutch are no problem, but downshifts seem better with the clutch. Perhaps that is because I stopped trying and never developed the skill to properly match revs.

[cparsons]

the drag racers actully kill the igniton for an umptheen of a second to upshift without clutch and without lifting off throttle. "they" say it will work for downshifting too but matching revs would still seem to be a problem. I haven't mastered downshifting without clutch either Russ!

[glenn cooper]

Better have that medical insurance paid up!

Yeah, I wouldn't recommend that on a motorcycle, but the fact is it's quite easy to change down w/o using the clutch in our cars.

Not to mention the slipper clutches now so prevalent will not allow upsetting the bike's rear grip while down changing.

Besides, your left foot is busy on the whoa pedal, while yer right one is mattin' the go pedal.

Yeah, I know, it's just me and my like footed fiends, to each his own, yadda...

Weeeeeeeee!

GC

[RussMcB]

Sounds good, Coop. My race car's engine does have the slipper clutch feature (and my street bike does not. I had forgotten about that.). I'll give clutchless downshifting a go when I drive the race car. I'd much prefer left foot braking if I can do it.

[carnut169]

I started out shifting w/o the clutch, ever. Like Coop says, it is possible. When asked by an engine guy how I shifted he suggested using the clutch for down shifting as the forks are very small and combined with the traction 2 large wheels (shed w/ sticky race rubber) offers it is possible to damage the shift forks with a single mistake. It also seemed difficult going from 6th to 2nd w/o the clutch.
I'm on my second year (knocking on wood) with the same clutch.

Your mileage may vary...

[glenn cooper]

Yes, the ability to skip shift on the down change is gone w/ the sequential.

I still miss that ability, especially at places like Turn 10 @ Rd Atl where, in a Hewland equipped car I'd slide it out of top gear into Neutral, lefty brake, blip throttle repeatedly to keep gear shafts spun up, and when road speed was reduced to proper entry speed, merely snick the thing into 2nd.

Now w/ sequential, it's blip shift, blip, shift, blip, shift, blip, shift, all the while braking.
Still fun, no doubt.

Interesting note on slipper clutches. I believe the plates will wear quicker than non-slipper style, due to their slipping nature on down changing. Non slipper clutches will perhaps have their clamping force be overpowered by the grip and traction patch of our rear tires.

BTW, AMA Superbike times at Rd Atl are now almost into the teens - 1:20.2 the other day at a test day (Yeah - Maladin!). Very hot as well. Perhaps we'll see some teen times at the race in a few weeks...

G (Yeah, I'm working on my car today, in my AIRCONDITIONED garage!!) C

Russ, my girlfriend is back in town, maybe we come by for a looky at the car, AND a dip in the pool. Can she still borrow your spare suit?

[formulasuper]

My Ralt/Hayabusa RT5 FS hydraulic clutch slave cylinder has given me & others problems. They leak air past the piston rubber seal after 2-4 laps & you find yourself pre-pumping the clutch pedal before every braking zone. I installed a brand new Suzuki factory slave cylinder & starting getting air after about 45 minutes of track time. When the bleed fitting is openned the air is the first thing out. Another driver with a Radical CSR has had the same problems. I have changed to a cable system.

[RobLav]

I'm using a cable for my Yamaha. The Indy car pedal I bought is set up perfectly for it.

And lately, I've been using the clutch on downshifts in the RF99. Seems to be smoother. Intend to do that with the Yamaha.

I think the Suzuki 1000's in the Citations will be using the Hayabusa hydraulic slave. I'm the only one building a Citation with a Yamaha and it is getting to be a pain...

[carnut169]

FWIW- I have both. Stock VD setup to a Wilwood pull cyl to the stock bike cable. Seems to work pretty well (no issues, knocking on wood)

[rickb99]

Pssst, you wanna try a hydrolic??

I purchased a Wilwood pull-type about 2 years ago. This model:

http://www.hotrodsusa.com/store/slave.html

We went pure FC instead of building a D/SR. So the slave is sitting here with nothing to do. This is a brand new unit never mounted or filled with fluid.

Lists today at $73. It's yours for $35 including shipping within USA.

Pssst, any takers? Need a spare?

[RussMcB]

I'm confused. How do these work? Does a cable pull the "push rod", which in turn causes the hydraulic cylinder to pull the clutch lever? Is there a master cylinder involved? I must not be imagining it correctly.

This “Pull Type” slave cylinder is made from billet aluminum for high strength and plated with a tough anti-corrosion finish. The stainless steel push rod has a longer stroke than most cylinders assuring a full release of the clutch. Ideal for drag racing, late model stock, pro series and off road applications.

on edit: Oh, I think I get it. The end result is that the slave cylinder converts the cable pull to a hydraulic push.

I think I got confused because my stock Kawasaki set up pulls the clutch lever. There's no "pushing" involved.

[rickb99]

You set the slave up in such an orientation that it "pulls" the clutch fork. Use a hydrolic master cylinder clutch pedal just like in a 'real car' works good.

[Mike Devins]

Russ, This is what I on my DSR, the master cylinder pumped fluid to the Wilwood slave cylinder and the rod pulled on the original cable.

Three seasons and never had to bleed it and never had a failure.

That being said my conversion will have a cable all the way to the pedal if the engine does not already have a hydraulic clutch such as the 07 GSXR.

[RussMcB]

Looks pretty interesting.

Rick's offer is pretty good, so I'm going to get it from him and decide if that's the way to go or not. There are some advantages I like, such as, using the bike's cable & mount on the engine, while using the car's existing pedal/master/line. The slave cylinder is remote from the engine, so it should live a pampered life.