bravex

ove read all posts on rev matching and clutch problems. but i need to know just one last thing.

when i shift from 1-2 does rev matching mean that i should apply a little throttle while i let the clutch up or do i just feather the clutch all the way up and then accelerate away. i was tols by my dealer that under no circumstances should i have my foot on the gas while the clutch is down.

please advise . i know this is probably boring u greg as you have posted many times on clutches. but please push yourself once more to solve this problem for me.

greg

Don't worry, BraveX - it is a fair question. The ones I worry about are the ones who are too afriad to ask.

An early P.S. - After writing this, I realized how hard it is to describe some stuff in words. Really, you just don't think about this and it all happens very naturally. But here is the theory, so at least you can understand what you're trying to accomplish.

Here we go. The answer is you DO use throttle. Otherwise, as you feather the clutch, the clutch has to absorb all the energy it takes to accelerate the engine to the speed at which the wheels are making the transmission turn in 2nd. (breathe...)

Let's say you accelerate gently and shift out of 1st at 4500. I'm not in the car so I forget the numbers, but let's assume that 4500RPM in 1st is 30mph, and that, at 30mph, the revs in 2nd will be 3000. Your job is to let the clutch out with the engine at 3000RPM.

Now - the engine will naturally slow down when you lift (and you DO lift all the way as you shift out of 1st) - so if you get into second and let the clutch up right as the engine falls through 3000, you'd be perfect. Only problem is that the engine RPM's fall pretty fast, so you'd have to shift pretty aggressively to do this with no throttle - and you'd still have no throttle when you were done and the car would continue to decelerate until you did finally step on the gas. Makes for a rougher-than-you'd like shift.

Assuming we're after an every-day, smooth shift, we want to take just a little longer and be more relaxed. So you add a little throttle - this keeps the engine from falling toward idle. You don't need much - the engine isn't connected to anything. Depending on your timing and amount of throttle applied, you may speed the engine back up, or simply slow its downward fall - but the goal is to have the "right" amount to that the shift is smooth.

You don't HAVE to watch the tach and wait for the tach to read 3000 - this takes too much time and concentration, especially when you're going up a hill and the car is now coasting at 20mph, and the right RPM is now 2000 RPM - you get the idea. But note that even if you just get kinda close, you're reducing the work the clutch has to do to either accelerate the car/decelerate the engine to match speeds (if you're a little too high) to accelerate the engine to the match speed.

SO - you do feather the clutch, and you add a bit of throttle during the process until everything is fully connected up. You can feel this. This is the point at which, no matter how much slip you were allowing during the "feather", things have synchronized and you can let the pedal the rest of the way up instantly - because everything is matched up.

At that point you can do anything you want with your throttle foot. Even if it makes the wheels slip, once the clutch is fully engaged (and assuming it isn't already damaged) it will NOT slip and it will NOT be hurt.

This whole thing can be done very fluidly and very quickly. Maybe we should just have one guy drive and another shoot video showing his feet while you listen to everything else. Any takers?

Hope that helps.

BraveX - don't worry about this too much either. It isn't rocket science, there are many ways that work, and for each combination of RPM and how hard you are accelerating, it takes different timing, throttle management and feathering. But it becomes very second nature. You just don't think about it.

1C00lVC

Greg,

That a good explenation, but I believe it is almost imposible to "learn" it. Any one (most?) who drive stick do that naturaly. The only way to "learn" it is to drive a car/truck with no synchromesh gearbox. If you do something wrong the grinding gears will tell ya...

Many years ago I learn to drive a Sherman tank. 3 forward gears, anemic engin, 29 tons, and a clutch with a throrw of over a foot in travel... and this thing "rolled" along as easy as a qube .. That's where I really learned how to drive a stick...

AndyMenard

Guys,

Rev matching takes a bit of practice, but will most definitely extend the life of both your clutch and your engine.

I was fortunate (or unfortunate which ever way you look at it?) enough to have spent 7 years in a past life driving big rigs...and this is a practice you get real good at over time. I've found however that it took me a little while to get used to the M5 after driving an M3 for 2 years... Rev matching is a little different on a high revving inline 6 as it is on a torque monster beast like the M5.

The concept is the same however, bottom line is... you are trying to match the revs of the motor when you down shift to avoid the sudden shock on the crank, clutch and transmission. It should be one smooth motion when you learn to get it right.

-Andy-

PhilSeastrand

Excellent post, Greg...

I used to have a car with with poor syncros and it was very important to match engine speed to the transmission in order to even get it into gear. The way I practiced was to shift without the clutch at all. This required you to precisely match the engine revs to the transmission revs. I wouldn't recommend this on a prize such as your M5, but if you have a beater, it can help you to learn.

This is like anything else, you have to practice and gain muscle memory to make it work right all the time. If you have to think about it, it won't work right because it all happens to fast -- sort of like learning to riding a bike.

I've been driving sticks since I was about 6 years old. There are some benefits to growing up out in the country!

One week to go and counting!

------------------
Phil

01 M5 SilverStone due 12/00

[This message has been edited by PhilSeastrand (edited 02 December 2000).]

rad22

I have driven manual transmissions exclusively for over 25 years and in over 20 cars (I am apparently older than most of you) and wouldn't drive anything else. I considered myself skilled at shifting but was forced to adjust my technique with my most recent car. I just unloaded a 99 996 Carrera that was, for a long time, an absolute b**ch to shift smoothly. The clutch had seemingly only about 1/8" of engagement travel for feathering. Ultimately I found that my smoothest shifting came, not as a result of feeding in throttle to match revs, as I had been able to do with multiple previous cars, but rather learning to shift quickly enough to catch the revs as they fell through the matching rpm range. I ultimately found or learned that this practice doesn't necessarily mean aggressive acceleration and out of control driving, even in traffic. When done well, it's like playing a musical instrument, and believe me, your passengers will notice.

My new '01 M5 (with 275 miles so far) is comparatively much easier to shift smoothly, but that only makes it a finer instrument in the hands of a skilled "musician". Keep practicing...you'll get it.

Incidentally, of all the cars I've owned, the M5 is the finest, most refined, fun to drive and awesome performer of them all, including:
1974 Cosworth Vega GT (only mentioned because it's what I learned the stick on, fun for 9,000 miles...then it melted, GM bought it)
1977 VW Scirocco (my first true sports car and first love)
1985 Saab Turbo SPG (hi-tech for its time and fun when boost was dialed up by a tuner)
1987 Porsche 911 Turbo (a raging beast, unrefined)
1992 Mercedes 500E (boooooring)
1991 Acura NSX (2nd best car I've ever owned)
1995 BMW M3 (best friend bought it from me and is still my best friend, 'nuff said?)
1999 Porsche Carrera 2 (overrated, overpriced, under-quality-controlled, unimpressive POS)

Long live the BEAST!

------------------
01 Imola/Caramel/Burl
96 BMW R1100RT
00 Yukon XL

AndyMenard

rad22:

Sounds like you and I are close to the same age?? I grew up in the 60's-70's and I too learned to drive on a stick in my old man's Ford F350 truck on the back roads in the country.

btw: I am 42! but still a kid at heart!! Thanks to the BEAST!

-Andy-

Jim Dolan

Good job Greg. Co-incidently I meet with some enthusiasts tonight. A young man was there and he asked me about the heel and toe technique and I could have used your help. He asked me if it meant having your heel on the brake while at the same time your toe on the gas. That took me by surprise and I guess I under estimated the lack of experience some have with stick shift cars.

He went on to say every time he did it, it caused the car to jump or be jerky. Wow, I was speechless. On the way home I tried it and damned near crashed. That technique could be dangerous.

Hey Greg, help this guy out once more cause I couldn't explain it. All I know is shifting is second nature to me and smooth, I match revs, downshift when appropriate and try never to grind the gears.

rad22, I enjoyed your post as well we have similar backgrounds as to sticks. I've had nine bimmers; seven sticks and wouldn't have it any other way.


Andy, I got you beat. I drive my M5 on the weekends only just so I'll never get sick of it, this is truly a beautiful beast.

71 2002 (Colorado) What a car!
75 450SL (Colorado Beige)After 3yrs sold for a $2000 profit.(inflation era)
76 2002 (Inka)
80 Bristol 40 Sloop(20 year hiatus from cars.
82 528e Artic blue(The only mistake BMW ever made.)
84 533i Burgundy Metallic
87 325i Alpine White(good solid frame for racing.)
88 535is Salmon Silver
93 525i Calypso Red
95 E320 Brilliant Silver
99 5281 Titanium Silver
00 M5 Titanium Silver


[This message has been edited by Jim Dolan (edited 02 December 2000).]

greg

Hi, Guys -

Phil - yeah, my first car was a '63 VW bug (this was about '72 - it was already old) and the synchros were pretty worn. I learned to shift it without the clutch, to double-clutch, etc. It was an easy car to do this in. Every car I've had since has had much tighter tolerances in the transmission so that clutchless shifting is considerably more difficult- I would only attempt it in an emergency. NEVER in the M5 - might break a gear! (I double clutch all the time though - ca'nt break the habit!) But man, I was good at that old VW. It saved me a few times, 'cuz the clutch cable didn't last very long in that car. I had 3 break while I had it. Each time I got it home though, once even when the key broke off in the ignition and I calmly reached for the screwdriver I had in the glovebox - turned the "stub" with that and didn't miss a beat!

(For those of you who never experienced this "art" - you pop the car into neutral as you coast up to a stop light. Before the light turns green, you turn the car off, put it in first, and start the car in gear. Off you go - then shift up and down without the clutch, creep thru stop signs in 1st, and repeat the above if you have to make a full stop.)

Rad22 - I know what you mean about the Porsche. My new TT is a bit better than the old ones - but the shift technique practically demands near-perfect matches and very little feathering. Smooth launches are really hard to get in the Porsche.

Jim - I'm not a trained racer - so others may have more to say about heel and toe. Here's my take - whether you heel the brake and toe the gas or vice versa is personal preference and I think may actually relate to whether you're pigeon toed or bow legged - as well as the pedal position. I use the ball and side of my foot on the brake, and heel on the throttle. The goal, of course, is to execute a downshift while braking. Totally unecessary except on the track, but I learned it only because I thought it made me cooler.

Cheers -

TD

I have a note of caution on rev matching. While shifting, make sure that the revs are not too high. This is what causes jerky bucking shifts for me. It is easy to add too much throttle while going around corners, while not concentrating, right foot poorly positioned, ect.

Think of it this way. If the engine has no throttle input while letting the clutch out during a shift it is "passive" and will be "lifted" to the right speed. Granted, the closer the better. On the other hand if there is too much throttle while the clutch is let out the engine will fight against the the speed of the car. The result is a jerky shift. I don't think one needs to overshoot by a whole lot to get that result.

I was making a bad shift just often enough that I decided to rethink my technique and delay adding throttle. Like rad22 below, I too find that quick shifts help minimize the need for throttle matching.

I bet another bad outcome of frequently adding too much throttle during shifts is people slipping the clutch to smooth it out.

In normal driving, I never have a bad shift if I shift quickly and am light on the throttle.

TD