Can a car clutch be made lighter / easier to operate?

September 9, 2009 6:05 AM

Is there a way to make the clutch lighter to operate? Can springs be changed, etc? If it helps, it's a 96 VW Cabrio

History: my wife's right foot had a tendon that stretched and let the arch collapse. It was treated surgically. Her left foot is headed the same way, but does not yet need correction.

Current: we are considering buying a stick shift. The car we like has a clutch that is a little stiff (normal for the model of car). She feels that this might endanger her left foot's tendon.

Question: is there a way to make the clutch lighter to operate? Can springs be changed, etc? If it helps, it's a 96 VW Cabrio

I don't mind hearing about assistive devices / shoes / orthotics, etc. but to be honest, these have not helped much with other activities such as cycling. So I'm primarily focused on how adjustable the clutch might be.

posted by blue_wardrobe to Travel & Transportation (9 answers total)

Generally, a clutch can't be made softer without significant reengineering. There are three factors to consider: the pressure plate acting upon the clutch, the displacement of the master cylinder, and the fulcrum point of the clutch lever. Each of these things is interrelated - decreasing MC displacement requires increased clutch pedal travel, modifying the pedal fulcrum changes the master cylinder piston travel, etc. The OEM pressure plate is generally the softest available, as aftermarket companies usually aim for higher torque holding ability, which means a stiffer pedal. I would confirm that the car currently has a completely stock pressure plate and clutch, and maybe drive a similar model to compare.

One thing that you may be able to do is to alter driving style. I haven't been in a Cabrio lately, but if she can operate the clutch pedal with her heel (instead of her toes or the ball of her foot, as most people do), that might reduce stresses. Just a thought.
posted by TheNewWazoo at 6:12 AM on September 9, 2009

Generally, a clutch can't be made softer without significant reengineering.

Agreed. The mechanical advantage of the pedal/lever would be difficult to adjust and the main force is the pressure plate spring. It would be very expensive to modify. Possible theoretically, but not practically. Even changing out the pedal box assembly for a different one would be a massive undertaking and require removal of a lot of standard parts of the car (like the lower dash) - it's just not practicable.

if she can operate the clutch pedal with her heel (instead of her toes or the ball of her foot, as most people do), that might reduce stresses.

This would be very difficult - both in terms of control (the flex of your foot is important for clutch control) and in terms of physical space. There is no way you can get your heel on the pedal through the arc of its travel effectively. The control aspect alone is enough to shy away from this idea, to me.

In short, the clutch (for your purposes) is essentially completely non-adjustable. Is there any reason you won't consider an automatic? I'd have though this was a perfectly valid reason to get one, but I am assuming that the lack of second hand VW Cabrio auto's is an issue?
posted by Brockles at 6:45 AM on September 9, 2009

VW clutches are pretty darned light to begin with. There might be some adjustment leeway to move the actuation point either higher or lower (in relation to the pedal's distance from the floor as it moves through the travel arc) which might make things easier for your wife.
posted by Thorzdad at 8:33 AM on September 9, 2009

Response by poster: @Thorzdad: having driven the Peugeot 205 GTI range as well, I found their clutches a *lot* lighter. And the European Corsa's clutches are so light as to be almost sensation free under your foot. That can be quite disconcerting.
posted by blue_wardrobe at 8:43 AM on September 9, 2009

Response by poster: @Brockles: it just comes down to opportunity: we find ourselves in need of a car suddenly, and there it is, just sitting there near us, at a good price. We weren't thinking about a convertible, but hey, if we're going to buy one, it might as well be fun to drive, and a stick-shift (in our minds) is part of that. But not if it's going to be a pain. Unless, of course, it becomes my main commuter car... :)
posted by blue_wardrobe at 8:45 AM on September 9, 2009

Response by poster: Thanks all for your feedback. I now get that the clutch is essentially unadjustable.
posted by blue_wardrobe at 8:46 AM on September 9, 2009

Squats
posted by low affect at 2:08 PM on September 9, 2009

Uh, hang on a second. My Skyline GTR had a rock hard twin plate racing clutch (built for standing starts). I made it almost normal by replacing the slave cylinder. This changes the amount that you need to depress the pedal by with respect to plate pickup. You may be able to find a different sized unit at a breaker. Alternatively, lighter (less dense) fluid may help? Not sure about VW, but Nissan's racing arm (Nismo) makes these sorts of alternatives freely available.
posted by Sutekh at 1:30 AM on September 10, 2009

Less dense fluid will do nothing. The stiffness of a hydraulic Clutch is dictated by the pressure plate springs, the mechanical advantage of the pedal (pivot to actuation point length) and the relative bore sizes of the master and slave cylinders.

VW's of this type do not have hydraulic clutches, so your experience is not applicable.
posted by Brockles at 6:34 AM on September 10, 2009