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  #1  
Old 03-03-2001, 07:31 PM
Chicagoland
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Is it better to brake only or down shift and brake on a manual transmission? I have always had this question on my mind for years.

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  #2  
Old 03-03-2001, 07:33 PM
engatwork's Avatar
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I have always heard

it is better to brake because brake parts are cheaper than tranny/drivetrain parts.
Jim
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  #3  
Old 03-03-2001, 07:56 PM
Chicagoland
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Thanks Jim. About how much would it decrease the manual life?
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  #4  
Old 03-03-2001, 08:26 PM
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Tut, Tut, Gentlemen...

The reason you have gears to shift in the first place is to maintain the proper RPM for optimum performance of your engine. That applies to acceleration as well as braking.

I always downshift prior to applying the brakes. You will be able to maintain better control of your vehicle, and you will be in a better position to accelarate sooner if and when the situation calls for it. The only exception to this, is if some bonehead does something that forces me to brake first, and then pick the correct gear.

There is nothing wrong with correctly downshifting to aid in braking, or even in lieu of braking, if you do it correctly. This applies to manual as well as automatic transmissions. And there should be no excessive wear caused by correctly downshifting your car. The key is doing it smoothly, and being aware of what gear you should be in at a given speed, and them matching the RPM to those two factors. Speed+RPM+correct gear.

Next time you drive your car, make note of the RPM range you run in before shifting. What is the high RPM when you shift, and what is the low RPM after you shift (when you let out the clutch)? Then, keep track of your speed range in all of the gears (this is easier if you have someone write it all down while you are driving), For instance, 1st gear, 0 to 15 MPH, 2nd gear, 15 to 30 MPH, etc. So if you know, for instance that you are going 25 MPH in 2nd gear at 3,000 RPM, you will know that if you want to shift down to 2nd from 3rd, that you need to do so when you are going 25 MPH, and will need to increase your RPM to 3,000 in order to do a smooth shift. Then, after you do that, you can decrease throttle pressure to slow down smoothly. Just remember this: Whatever speed you are going when you shift into a higher gear, is just a different RPM for either gear. 25 MPH in 2nd = 3,000 RPM; 25 MPH in 3rd = 1,200 RPM, get it?

Again, the purpose of shifting is to keep your engine operating in the optimim power curve for the drive train on your car. I hope you follow what it is I am saying, and understand that all of the numbers I am using here are simply hypothetical examples and not absolute guidelines of any sort.

This stuff takes time and practice to get it right, and high performance driving schools actually charge you money to learn how to do this correctly.



[Edited by longston on 03-03-2001 at 07:32 PM]
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  #5  
Old 03-03-2001, 08:47 PM
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While I hate to disagree with Scott, I do
High Performance driving schools (at least none that I have been to) do not teach to down shift before braking, EVER.
Say you are going 140+ MPH at the end of a straight with a 180 degree curve ahead. You brake before you enter the turn to scrub off speed and shift the weight of the car from rear to front to help steering. When you enter the turn, you use the heel-toe technique (gas & brakes at same time) while you down shift into the appropriate gear. In some situations (never high speed) you could slow the car down by down shifting but you risk the possibility of over-revving the engine and it also throws the car off balance. Not to mention that brakes are MUCH less expensive than a clutch. There is a web site that details HP driving techniques ( I can't seem to find it now), I'll hook you up with the link.

Gary
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  #6  
Old 03-03-2001, 08:54 PM
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Its not a either/or thing.......you need to do both at the same time!!!
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  #7  
Old 03-03-2001, 10:19 PM
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Yes, And No...

OK, fine, you're right, and you're wrong. I'm sorry if I wasn't clear enough, or didn't explain myself sufficiently, but now I'm paying for it aren't I?

In high performance driving, what Gary is correcting me on is absolutely true. But, what I was talking about was simply the proper technique for downshifting so you don't damage your clutch, drivetrain, or over rev the engine, and can still use the drivetrain and engine to aide in braking.

The answer I gave was for well thought out safe street and highway driving, not high performance "going 140+ MPH at the end of a straight with a 180 degree curve ahead." And while I understand your example Gary, I gotta ask, what, you were never taught in any instance to downshift strictly for power without braking first?

And I wasn't saying that high performance driving schools teach people to downshift before braking, I only said that was what I do, and I only meant under normal driving conditions, not while racing. What I was talking about the schools charging you money for was to learn how to shift a transmission the way I was explaining.

When I down shift, I do so in such a way as to not create an immediate braking effect, but to stay within the operating parameters of the vehicle I'm driving (at least I thought I explained it that way). But then, all of my training and experience is being focused right now on defensive driving on normal streets and highways because that't where we drive. That doesn't mean that I don't know how to, or can't heel and toe, drive by the seat of my pants, and power in and out of curves like a champ. :p

The original question from Chicagoland was phrased in such a way that I assumed that this was someone fairly inexperienced with shifting manual transmissions. Let's look at it again: "Is it better to brake only or down shift and brake on a manual transmission?" I don't think he wast asking for high performance racing tips, just about shifting and braking while engaged in common sense driving... Maybe I over-answered the question? Perhaps I should have just said, "downshift and brake is better", and left it at that.

But I have to disagree with this concept of driving that says that brake parts are cheaper than drivetrain parts. Initially, yes, but cumulatively, no. How many brakes and rotors does it take to equal a clutch job? And why does it even have to been seen as an either or situation? Why not get the best longevity out of both systems by using them properly? I'd wager that the way I drive, I can make my brake parts last considerably longer than most people without damaging, or even prematurely wearing any driveline components.
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  #8  
Old 03-04-2001, 03:22 AM
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I prefer to just use the brakes to slow down rather than downshifting. The brakes are cheaper than the clutch.

My dad bought my car brand new and I inherited it. It has 200,000 miles all on the original clutch with no of slippage at all.
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  #9  
Old 03-04-2001, 03:49 AM
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My clutch on my 85 Mustage GT is original 179000 miles. I prefer not to downshift to not place addition stess on the crankshaft, driveshaft and U joints.
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  #10  
Old 03-04-2001, 12:45 PM
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Longston is quite correct.

Chicagoland,

Don't be limited to either braking or downshifting. You can do both at once. Matter of fact, you can brake, shift gears, AND stand on the gas... all at the same time!

*vroom* *vroom*

Kuan
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  #11  
Old 03-04-2001, 02:31 PM
roas
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Several questions have always been unanswered in the back of my mind and they seem to apply to this thread so I'll ask.

#1 Does downshifting manually in a Auto transmission do any harm or create any out of the ordinary wear? This is assuming you are not overrevving the motor upon downshifting.

#2 Is is OK to use the heel and toe method in a Auto by blipping the throttle to get a matching rpm just before the transmission responds with the downshift?

#3 And lastly, in a manual transmission is there any harm in upshifting to a random higher gear, such as from 2nd to 4th?

I do practice these techniques all the time I must tell you, every women who has been in the car (and some men) seem to think these are harmful? I have not seen evidence to support either side?
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  #12  
Old 03-04-2001, 04:04 PM
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Ah, The Old Skip Shift, Eh?

First, your clutch and driveline components wear out from IMPROPER shifting and clutching, not just from downshifting, that is, assuming that the shifting is being done c o r r e c t l y....

But everyone drives differently and continues to drive the way that they have "adapted" for themselves, unless they are taught to drive by a professional instructor. BTW, The hardest part of that learning process for both the student and teacher is the first stage where the student must un-learn all of their old bad habits.

Ross, you either need to learn to drive better, or to not let stupid people ride in your car anymore!

Seriously, as I already wrote in this thread, manually shifting an automatic transmission is pretty much the same as doing it with a manual transmission. Read my original comments on this thread, but record the speeds and RPM' while allowing the transmission to operate in fully automatic mode. Then you will know what the normal operating range is for each position on your automatic transmission selector. So, just stay within those operating ranges for those gears, and you will not harm, or prematurely wear out anything other than the patience of those less enlightened than you.

Now as for your last question, I haven't seen anyone do this in a car in years. We used to call it "skip shifting". You mainly see it done in big trucks with more than 5 selectable gears when the truck is driven unloaded, and on a flat stretch of road. Still, you must stay within the operating range of the engine. If you, in your Mercedes, shift from 2nd to 4th, you are probably not operating the engine and driveline within the correct operating range, are likely to be "lugging" the engine, and if you have any load (slight grade for instance) on the engine, using heavy throttle will cause undue wear. However, that said, if you're entering traffic on a downhill grade, like a velocity ramp, and you don't push the car past the correct operating range, gradual accelleration will get you going faster than hitting 3rd first, and under those circumstances, will not do any harm.

See, what you're doing when you skip-shift is just creating a kind of "false overdrive" where the smallest amount of RPM can be translated into a faster speed, because you're "overdriving" the engine / transmission relationship. Older cars used to sometimes have overdrive transmissions to help save fuel. Once you shifted to the highest gear, you'd activate the overdrive which would let you cruise at high speed, but also at a lower RPM. It was like having a 5th gear.

Rule of thumb, if it feels right and smooth, it probabaly is. If it feels like you're lugging it, if the vehicle is bucking, if the tires screech, or if the car feels like to just ran into the world's largest block of gelatin, that's bad. Go to a library and see if you can check out a couple of books on driving by Bob Bondurant. He's the guy who encouraged me to shift automatics just like manuals...

Oh, and tell your passengers to: "Get in, Sit down, Buckle up, Shut your yap, and Hold on". :p
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  #13  
Old 03-04-2001, 05:20 PM
roas
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In regards to the "skip-shifting", this is in a manual tranny car.

My dad always used to do it and that of course brought on the comments from my Mom, "Oh Roger, stop doing that! You are ruining the car." Well he never paid much attention to the advise and now I do the same thing.

I ask because I usually do this in our Toyota Tacoma at stop lights, 1st, 2nd to the speed I want then 4th to level the speed off quickly.

As for the automatic transmission downshifting, I am mainly addressing a situation where you may be cruising at a steady speed (60 mph) and then may have the need to downshift for a little passing, its faster to already be in the gear than to wait for the auto-kickdown from the transmission.

I have always let the engine so some of the breaking on down grades and even when coming to a stop (good practice of Heel-and-Toe technique even to first gear) so I want to avoid any potential long term damage, hence my questions.
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  #14  
Old 03-04-2001, 08:25 PM
LarryBible
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There's performance driving and there is economy driving. If you are driving for economy, you will be able to stop much, much cheaper with the brakes.

If you're talking about performance driving, I'll let the Michael Shumacher's(sp?) on this site argue that point.

Have a great day,
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  #15  
Old 03-05-2001, 02:12 PM
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downshifting without matching revs also contributes to gear synchronizer wear. And if you force it, not only will the driveline be subjected to shock, but you will also upset the car's balance because of the sudden engine-braking.

once you have downshifted and are engine-braking, you are also wearing off the opposite faces of your gear teeth, especially the rear axle hypoid gear. Of course these could be negligible, but contribute to additional wear nonetheless.

but when i downshift from 5th to 4th to 3rd on an offramp (with proper rev-matching of course), i tend to forget that because of the glorious sound that inline6 makes when engine-braking in 3rd at about 4000rpm.

rev-matching is especially needed for the benz because of the wide spacing between ratios, and the high rotational mass of the engine/flywheel.

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Old 03-05-2001, 02:12 PM
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