Driving technique with a sensitive clutch

[jrwilson]

So, I finally got to drive my '78 today and I have to say I was very surprised at how the clutch has zero transition - it is literally like a light switch. Even shifting into second is a bit of a hurky jerky affair.

I'm used to the above floor clutch pedals that have a significant transition so it's also the change in pivot as well that is so different. Also figuring out the gas pedal sensitivity has me feeling like I'm learning to drive stick all over again.

Does anyone have any driving tips on how to adjust to this thing? Being able to take off from a light without stalling and looking like a tool would be welcome!

[Bill Douglas]

You could try giving it 3,000rpm as you let the clutch out then when the car starts to take off, just hold it there for a few moments and give it some more gas. Don't let it all the way out immediately. First gear is quite high compared with most other cars.

I'm wondering if the spring/cable is a bit sticky. It should be smooth. Especially shifting into second. You could spray some oil on the omega spring, the pivot and a few other bits in the area. Also bushings on the clutch pedal wear too. I put some oil on mine occasionally. Good luck.

[ecotyresuk]

Hello

[GaryR]

Originally Posted by jrwilson

So, I finally got to drive my '78 today and I have to say I was very surprised at how the clutch has zero transition - it is literally like a light switch. Even shifting into second is a bit of a hurky jerky affair.

I'm used to the above floor clutch pedals that have a significant transition so it's also the change in pivot as well that is so different. Also figuring out the gas pedal sensitivity has me feeling like I'm learning to drive stick all over again.

Does anyone have any driving tips on how to adjust to this thing? Being able to take off from a light without stalling and looking like a tool would be welcome!

There is no clutch adjustment, only free play. As has been described above, assuming you didn't install some whacky "race" clutch or you hear some strange sounds (bad through-out bearing), I would start with being sure all levers and springs are correct, cable moves easily, and finally the pedal assembly.

[jrwilson]

I don't think there's anything wrong per se, I'm just not used to it. I'm told that Porsches have hair trigger clutches. Just wondering if there's any advice on how to manage it.

[911obgyn]

Practice, get out of traffic, be deliberate and find the release point.
Adjust the clutch according to the bently manual. There are bearings in the clutch arm that seize up and need cleaning and lube.

[jrwilson]

I'm so used to hovering with my foot off the floor to release the clutch in a traditional setup, it'll be hard to adjust!

I'm planting my heel on the floor and levering back that way to finesse the clutch, is that the best method?

[darrin]

Originally Posted by jrwilson

I don't think there's anything wrong per se, I'm just not used to it. I'm told that Porsches have hair trigger clutches. Just wondering if there's any advice on how to manage it.

Not my experience with my '86 (also with a 915 transmission - I have a stock Sachs clutch) -- my clutch has a pretty broad engagement zone -- on a hill, I can easily modulate between rolling backward, staying still and rolling forward using the clutch alone. That said, my clutch does release a bit higher than on other cars I've driven. Suspect you'll become better accustomed to it as you build mileage in your SC

[MichaelSJackson]

Maybe a little practice? Find a gentle incline with no traffic and just play with the friction point. Don't engage the clutch to take off, but use the clutch to gently rock the car. (on and off, on and off,...) A little of that and it won't feel so binary.

Maybe a previous owner put in a lightened flywheel? Flywheels are momentum batteries. Build up the revs to store the momentum. The momentum is then used to start pushing the stopped car. Lighter flywheels require more revs to produce the same momentum.

As mentioned above, your '78's torque curve really starts at about the 3000 range. If your flywheel isn't storing "enough" momentum, you'll have to include more torque?

All that said, the same jerkyness in 2nd, points to something binding. Unless you're shifting too early? (I doubt it. But your upshifts should result in still being in the torque curve's strong part. 3000+)

I hope none of that was insulting. I'd just been driving low RPM V8 trucks most of my life and this was all new to me.

Michael J.
'78 SC

[spuggy]

Originally Posted by jrwilson

I don't think there's anything wrong per se, I'm just not used to it. I'm told that Porsches have hair trigger clutches. Just wondering if there's any advice on how to manage it.

The stock clutch shouldn't be hair trigger. It's like any other clutch.

Perhaps someone fitted a kevlar puck friction plate? These are pretty digital - either in or out - and really hate to be slipped. They will complain (chatter) loudly on hill starts and the like, where you have no alternative but to slip the clutch. But if it doesn't chatter when slipped, it almost certainly isn't a puck...

Bill's advice would apply regardless. Moving away from stopped, let it start to bite, let it engage gradually, increase throttle as required to maintain RPM. With a puck, you just have to use a lot more finesse than the stock friction plate, because the difference between "in" and "out" feels like 2mm on the pedal, instead of 20mm or whatever...

I always found the best/smoothest 1st->2nd shifts on a 915 happen when you pull enough RPM in 1st that 2nd is in the sweet spot when you let the clutch out again. So try not shifting into 2nd below 3500, 4000 RPM or so.

It is a sports car.

[jrwilson]

It's a stock clutch as far as I know, the whole engine and transmission was just rebuilt and nothing in the paperwork implies a special clutch. I'm a bit dismayed to learn it should have a broad engagement, I wonder if there's anything to be done about that?

[T77911S]

if the "helper" spring is broken the clutch will feel heavier and perhaps that extra force is giving you issues due to pedal arrangement.

also, you may be use to hydraulic clutches. cable clutches are different.
make sure it is adjusted properly.

[917_Langheck]

A properly functioning 915 clutch package shouldn't feel any different, engagement-wise, than any other car. The take-up should be a smooth transition without any switch-like behavior. If that is the case, either the package is race-prep, or it's out of adjustment.

[spuggy]

Originally Posted by darrin

That said, my clutch does release a bit higher than on other cars I've driven.

Heh. My wrenches gave my car back to me once with the clutch beginning to engage really early, like first inch of travel or something. Hard "nope" from me and a quick cable adjustment later....

You can used to/drive anything, but I like mine to start to "bite" where I expect it to - somewhere about the lower 1/4, 1/3,of the range.

[spuggy]

Originally Posted by T77911S

if the "helper" spring is broken the clutch will feel heavier and perhaps that extra force is giving you issues due to pedal arrangement.

PO rebuilt pedal box and got fed up trying to put the helper spring back, so just left it out.

Said it didn't make much difference. I bought the car and drove it 10+ years without one, felt just fine to me.

Stock clutch - well, I distinctly recall you could depress the clutch pedal all the way with one hand at an odd angle while lying in the footwell. Very little effort.

The RSR-equiv pressure plate, on the other hand, broke every original lever/bracket in the cable path one after the other due to the increased pedal effort (felt like a leg press machine and would have your calf muscle trembling and you weeping like a little girl after 20 minutes of stop-go traffic) - but I don't think the pedal box helper spring would have made any difference to that at all...

You can't mean the omega spring; wouldn't the car be basically undriveable if that weren't working/fitted correctly?.

Originally Posted by T77911S

i
make sure it is adjusted properly.

Where you mentally expect the clutch to engage can make a big difference - some may prefer a different point/find it easier to control/apply pressure at a certain engagement point.

But IME stock 915 clutch is light, predictable and user-friendly with a fairly wide range between "in" and "out". They just don't last very long with 300 ft/lbs at the crank. And are just a fond memory with over 350 ft/lbs at the wheels..

Perhaps get someone who knows what a 915 clutch should feel like to drive it? Maybe even the shop - if you can't trust them, probably shouldn't be using them anyway...

[jrwilson]

Originally Posted by spuggy

Perhaps get someone who knows what a 915 clutch should feel like to drive it? Maybe even the shop - if you can't trust them, probably shouldn't be using them anyway...

Good idea. I found the clutch pressure moderate but having to pivot my ankle to delicately release it cumbersome. It being out of adjustment makes sense.

[dave123456789]

Dig you heel into the floor when you press the clutch down, when you release rock your foot back till it engages then the rest of your pedal your whole foot moves away from the floor slowly at this point.

once i started doing this it was as easy as driving an above hinged car.

previously my clutch pedal was annoying to drive till I did that and I have never had an issue with a manual car before. my clutch is likely the original and very worn though which makes it heavy.

[RSTarga]

My left heel never touches the floor, only on the accelerator. My 16 year old granddaughter had no problems, something is wrong with your clutch.

[proporsche]

JR..if you can take a picture of your clutch arm i could tell you what adjustments you need.
If you are a taller man i prefer the clutch cable a little loose so it grabs lower towards the pedal cluster board.If you are shorter man i like to make the clutch cable 2 clicks tiger so it releases higher...take a pic like this and let us see it
Ivan

[spuggy]

Originally Posted by RSTarga

My left heel never touches the floor, only on the accelerator.

Huh, interesting.

My left heel is on the floor for 100% of starts from stationary, for pretty much any manual transmission car; think it enables better control. It was simply not an option due to the pedal arrangement/travel on the school bus I drove once, or most vans/trucks.

In a 911, my left foot comes off the floor for double-clutching, but that's about the only time, at least since I gave up experimenting with left-foot braking...