Foot-braking vs. Down-shifting - BMW Forum - BimmerWerkz.com
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#1 (permalink) Old 06-12-2009, 03:43 PM
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Lightbulb Foot-braking vs. Down-shifting

What's your guys' opinion on foot-braking vs. using down-shifting as braking?

My friend and I were having a discussion about what's better on the car. He said downshifting uses less of the brakes and in turn the brakes last longer.

However, I think that down-shifting puts extra strain on the engine and thus your wearing out your engine more than the brakes.

What are your thoughts?

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#2 (permalink) Old 06-12-2009, 04:10 PM
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A decent engine shouldn't be stressed by downshifting for deceleration. But don't slip the clutch; blip the throttle to get engine speed closer to the expected higher revs before shifting (this also saves the transmission syncros). I usually lift off, wait a bit and then downshift when the new engine speed will be about 4000 rpm. Even a Trabant engine should last forever doing that. Using brakes alone will tend to heat them, and that accelerates wear nearly exponentially (a guess, but likely close).

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#3 (permalink) Old 06-12-2009, 04:32 PM
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Ok which would you rather replace your clutch or your brakes?

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#4 (permalink) Old 06-12-2009, 04:48 PM
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Replacing my brake.....Save my clutch for all who wants to test BMW Power!!!
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#5 (permalink) Old 06-12-2009, 06:55 PM
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Originally Posted by AlpineSixAndSeven View Post
Ok which would you rather replace your clutch or your brakes?
*Sigh* if you match revs even remotely closely, there is no clutch stress. My E30 passed 180,000 mile on the original clutch!

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#6 (permalink) Old 06-12-2009, 08:08 PM
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But rev matching doesn't really slow you down. I always downshift and rev match, as I slow down, but what I really am using to slow down the car are the brakes.

The engine is for making you go. The brakes are for making you stop.

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#7 (permalink) Old 06-12-2009, 08:34 PM
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.... even with revmatching there is still wear as you can match the rpms to be the same any RPM difference between the engine and transmission causes wear on the clutch. Rev matching on Reduces the wear... also the Newer Bmw's come with a CDV(Clutch delay valve) which slows the engagement of the clutch(basically causes it to slip more on engagement) causeing the clutch to Prematurely wear out(like mine at 120k is now slipping under higher Rpm shifts and launch's such as On Ramps) I have now done the CDV Delete BIG impovement BTW... Use the brakes there is a reason they put them on the car there SOOO much easyer to change(And way cheaper if you paying for Labor)

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#8 (permalink) Old 06-12-2009, 09:07 PM
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There is no better proof than long term durability. The E30 in my family didn't need brakes until 160,000 miles, and the clutch is still good at over 180,000 miles (including original throw out bearing). The method of driving this car must be doing something right. That is all.

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#9 (permalink) Old 06-12-2009, 10:48 PM
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Quote:
Originally Posted by AlpineSixAndSeven View Post
.... even with revmatching there is still wear as you can match the rpms to be the same any RPM difference between the engine and transmission causes wear on the clutch. Rev matching on Reduces the wear... also the Newer Bmw's come with a CDV(Clutch delay valve) which slows the engagement of the clutch(basically causes it to slip more on engagement) causeing the clutch to Prematurely wear out(like mine at 120k is now slipping under higher Rpm shifts and launch's such as On Ramps) I have now done the CDV Delete BIG impovement BTW... Use the brakes there is a reason they put them on the car there SOOO much easyer to change(And way cheaper if you paying for Labor)
Rev matching makes wear negligible. And CDV delete ftw.

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Originally Posted by witeshark View Post
There is no better proof than long term durability. The E30 in my family didn't need brakes until 160,000 miles, and the clutch is still good at over 180,000 miles (including original throw out bearing). The method of driving this car must be doing something right. That is all.
But what you and I do is much different from what most people consider engine braking. What folks like to do is downshift and just let the clutch out. That forces the clutch and synchros to do most of the work.

The engine's valves work the hardest at higher rpms. If you slow down enough by using the brakes to a point at which you can downshift at matching revs, then downshift, and let the gearing further slow you down until you can rev match and downshift to the next gear, etc., you're golden (what I do, and I gather that is what witeshark does as well). However, popping the clutch and seeing your engine go to 6000 rpm to violently slow you down is not something I recommend.

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#10 (permalink) Old 06-12-2009, 11:10 PM
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Rev matching makes wear negligible. And CDV delete ftw.



But what you and I do is much different from what most people consider engine braking. What folks like to do is downshift and just let the clutch out. That forces the clutch and synchros to do most of the work.

The engine's valves work the hardest at higher rpms. If you slow down enough by using the brakes to a point at which you can downshift at matching revs, then downshift, and let the gearing further slow you down until you can rev match and downshift to the next gear, etc., you're golden (what I do, and I gather that is what witeshark does as well). However, popping the clutch and seeing your engine go to 6000 rpm to violently slow you down is not something I recommend.
Right, which is why when I downshift (with matched revs), I rarely exceed ~4000 RPM. But I usually get to that point by simple throttle lift off with nearly no braking, most times, none at all.

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#11 (permalink) Old 06-12-2009, 11:46 PM
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I donno about you guys but I learned to coast in neutral till I'm almost to a stop then use my brakes for the last bit... 160 is good on brakes round town or highway?

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#12 (permalink) Old 06-12-2009, 11:54 PM
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I donno about you guys but I learned to coast in neutral till I'm almost to a stop then use my brakes for the last bit... 160 is good on brakes round town or highway?
That mileage was mixed, including a trip to Europe (the car was shipped there and back) and fresh tires for the German Autobahn. All the service records prove it.

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#13 (permalink) Old 06-13-2009, 12:01 AM
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Quote:
Originally Posted by AlpineSixAndSeven View Post
I donno about you guys but I learned to coast in neutral till I'm almost to a stop then use my brakes for the last bit... 160 is good on brakes round town or highway?

I only put in the clutch if I am breaking heavily. Otherwise it stay engaged till it need to be downshifted or stop.

Of course if i am driving like i should be driving I downshift to slow down and supplement with brakes.

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#14 (permalink) Old 06-13-2009, 12:04 AM
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Coasting in neutral is illegal in most -- if not all -- states.

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#15 (permalink) Old 06-13-2009, 12:20 AM
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Well, good clutch and brake use needs to be better learned I guess.

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