jimmyR

I have been using my down shift paddle to down shift when slowing down for stop lights on a regular basis. It seems to work well and gives me the feeling of using a 5 speed shifter. I know it saves the brake pads, but is the RDX designed to do this on a regular basis without damage?

SinCity

I would think that you are putting more wear on the trans by downshifting that way. That is just my opinion.

aznboi2424

iTrader: (10)

x2
brakes are used to stop the car. thats what they were designed for.

Acura604

x3
brakes are cheaper to replace than a trans. so use your brakes.

Ibn Rushd

More or less, what you're doing is engine braking.

Usually, you want to avoid doing it, and use your normal brakes...especially if you have ample room. Use the brakes.

However, if you see that stopping isn't working well enough, and you don't want to totally mess up your passengers braking really hard (as that can get nasty), then usually if you shift down, it'll be okay.

There are times when i had 5 people in the car and my normal brakes in the Civic weren't going to do it, so i engined broke instead,and it works like a charge, and your passengers don't feel it, AND you don't nosedive your car and mess up the person behind you.

You can also down shift when you notice your RPM is at the very bottom of the band as you're coming to the light but you KNOW it will change to green as you get there, in which case, just downshift, so that when you do accelerate, you won't get yourself stuck in the wrong gear.

scudzuki

Engines are also quite expensive to replace. I read once that it takes 3000 HP to stop a 4000 pound car in an average stopping distance (this was in the 80s, so I'm guessing around 250 feet). The same car might have taken over a quarter mile (1320 feet) to accelerate to the same speed. In other words, brakes generate way several times the thust (in the opposite direction) than the engine generates in the forward direction. The energy to stop your car has to come from somewhere. When you use engine braking, almost all of the thrust (except for small frictional losses in the tires, bearings, and transmission) are exerted through your engine's crankshaft, connecting rods, piston, and rings... as well as the cylinder block and cylinder head. Do you think your engine was designed to handle outputs with bursts of 1000 ft-lbs of torque?
Get some EBC green or yellow stuff pads and cut your drivetrain a brake.
Note that I am not talking about leaving the tranny in a lower gear (in sportshift mode) trailing the throttle into a corner, or the automatic downshifts that the tranny produces when braking down a hill. Neither of these situations creates the large potentially destructive energy spikes I am talking about.
Joe

JGard

Don't let these people scare you, it's fine. I do it all the time and it's a normal way to drive a manual transmission.

There's no more wear on the transmission from doing this than normal upshifting or when it automatically downshifts when you stomp on the throttle.

SinCity

This is not a manual trans. If you use the manual trans logic, it is normal to downshift like you stated. But on the other hand, you are putting wear on the clutch. Looking from that persepctive, it would be cheaper and easier to replace brake pads than the clutch.

johnny99

Engine braking is useful when you're going down a long hill and don't want to ride your brakes all the way down. Use the brakes for faster and more accurate stops.

JGard

That's not true if you're doing it properly. If you're wearing out the clutch it's because you're not rev matching your downshifts which is the inappropriate way of doing it.

It's also technically clutch-braking at that point and not engine braking.

SinCity

You are correct, less frictional loss with rev-match.
Heck, I just leave it on D and brake normally.

sj993

I used to downshift to slow down all the time in my 94 accord, I never once had a problem with the auto transmission. Even in the owner's manual (for the accord) it stated that by using 1,2,D3,D4 you could drive the car like a manual transmission except without the use of the clutch. Granted, the RDX isn't quite the same but on occasion I do downshift to slow down just not all the time.

Fishbulb

The main reason one downshifts in a manual car is so you can be in the correct gear for accelleration. The auto does it for you.

Why would you bother using the auto tranny for engine braking? It makes no sense.

mau108

your automatic 94 accord manual stated you can drive the auto like a manual by shifting through the gears like that?

Please do scan and post this, I'd love to see it.

sj993

Here it is:

creativeguy

I downshifted to engine brake my Integra GSR for 11 years and never had any clutch problems. And I didn't have to replace my brake pads until 90k miles. I sold the car to a mechanic and he was quite happy with the transmission.

I do the same with my RDX. The computer won't downshift unless your speed is in the correct range, so you'll never make a mistake like you can with a manual. An added benefit is that it keeps people from tailgating. After a few downshifts in traffic on the freeway with no brake lights, they tend to give you some space.

JGard

Actually, the one thing an automatic can not do for you is anticipate the needed gear for upcoming conditions. This makes it that much better an option to "auto-shift" when braking. Maybe you like pressing the gas and waiting for it to downshift and then going, but I prefer to step on the throttle and just go.

737 Jock

I agree with these gentlemen. Downshifting to select the proper corner exit gear or to make a controlled descent down a slippery hill, does not slam massive energy spikes into the trans and engine the way downshifting for speed reduction does.

Much of the initial spike is absorbed in the friction-wear surfaces in the trans (and there is not one clutch, there are five).

Good EBC brakes (highly recommend) are about $150.......a trans rebuild is thousands.

phoward_15

If I were to purchase the EBC brakes what would a typical installation/labor cost be at a dealership? There's no way I can do this myself.

sj993

Downshifting for light deceleration isn't going to harm anything. I find it convienient to do so when someone turns off a road and I'm following behind them as it saves me from having to use the brakes and I can simply downshift a gear slow down enough for the person in front of me to turn off and then accelerate. Also, I do enjoy shifting the gears as I find it gives me more driving enjoyment. In the 5 years of doing I have never had a problem in either my Accord or my Audi.

SinCity

Also, our trans does not rev-match like VW's DSG.

JGard

well, the VW DSG is also a manual transmission with a clutch, so it needs to rev-match.

Our slushboxes have torque converters which remove any potential "shock" to either the engine or the transmission, so rev-matching is not necessary.

737 Jock

This is a good observation, but driveline shock can damage the torque converter as well: Torque Converter damage

We're not talking about shock from brake torque launches here, but the OP question seemed to regard using downshifting to save the brakes.

Brakes are still the least expensive way to stop.

JGard

Yar. Brake-stand type launches are the WORST thing you can do for your car. I have a friend who had an AT Subaru WRX and took it to the drag strip. It took a few trips to the strip, but eventually he destroyed his torque converter completely and had to get a new transmission. The car was less than two years old at that point.

That said, using the transmission to slow the car down is not doing nearly the same kind of damage as that.