http://www.autopia-carcare.com/downshifting.html

This article (linked to s2ki) says its bad on your car to slow down using the clutch. What?

I have always drove this way. Is it really bad? how bad is it? I cant even imagine driving otherwise. The only time I use my brakes are when I'm coming to a complete stop. Is this really bad -- someone help... I thought everyone slowed down by downshifting? The article dosen't really say much, so I'm asking everyones opinion?

 

Well, just considering the wear factor alone, ask yourself this question: what's easier/cheaper/faster to replace: brake pads or engine bits?

I try to keep downshidting-to-slow-down techniques mostly for the track, of course it is kinda hard with some cars that love to be shifted i.e. S2K.

Enjoy!

 

Well as downshifting is usually done at the same time as breaking (not for slowing down but for being prepared with the right gear though and out of the corner) i find it a bit hard not to use engine breaking. It's not really a good idea though, i think you'll have more control under hard braking if you use the brakes only. Someone (i think it was at a bike track day i attended last summer) said the engine is for accelerating, the brakes are for decellerating, and you should never use both at the same time. I don't know.

 

I for one, can't imagine using downshifting to slow the car down except when I play the video games. You know all that many racing games you can take corners faster by just downshifting and without using a brake. But that is videogame where you don't have to worry about anything.
In a real world, for your engine's longevity sake, you want the brake to do the job of slowing down and stopping.
I downshift to accelerate not decelerate.
Also if this has to do with taking the foot off the gas and let the car slow down while in gear, here is what I do.
I ususally let it go to neutral and slow down to a stop, because to avoid excess gear whine.
But my driving style is very mild, I am no where near aggressive as I'v seen from other members.

 

It's not really your engine that you kill when you downshift to slow down, it's your transmission and clutch. Every time you downshift without double clutching, you wear out your syncros a little more. Even if you shift into a gear but don't let the clutch out, just by shifting into that gear, the syncro damage is already done. Also, your clutch is made to slip when you're getting the car going from a dead stop, but other than that, it's really only supposed to let your smooth your shifts and allow for the speed of the transmission main shaft to change suddenly as you change gears. If you're downshifting all the time to slow the car down, you're basically using the clutch as a brake - and it's just not built to handle that kind of abuse for very long. Lastly, there is always the possibility of a mis-shift if you're downshifting that much. If you accidentally throw it into, say first gear at 50 mph, you've just put a hell of a lot of strain on the syncros and when you let the clutch out, you're engine will hit something like 11 or 12 thousand rpms. When that happens, it blows. And it's usually obvious to the dealer when an engine fails due to over-revving.

As someone else said, think about it like this - brake pads are cheap and can be replaced in minutes. Your clutch is expensive and takes a day to replace. And your syncros are expensive and require a full transmission rebuild (more than one day) to replace. Next time you see a light turn red, do your car a favor and use your brakes, not your transmission, clutch, and engine to slow the car down. Either keep it in whatever gear you're already in while you're slowing down, or just put it in neutral.

 

I have asked the same question, in the last 48 hours even! When we were cruising Lime Creek Rd (ok, not cruising, tearing it up!), I found myself downshifting a lot to slow in the corners, as I didn't feel as confident with the brake. It may make more sense financially to use the brake, but my confidence is priceless...

 

Somebody once said......"Gears are for going and brakes are for slowing". If you don't know how to drive, this is a valuable option - and certainly the way 95% of the population do it.

However, have a look at racing drivers when they are behind the wheel. Even heard of a term called "Heel/Toe"?

When I was certified for my competition racing license back in '97, one of the requirements to achieve certification was to show your proficiency in "heel-toeing".

So, you've heard the term before, but don't know what it is......

Basically, this is where you match the engine revolutions to the gear that you are about to be shifting into when slowing down. We all know that when "lazy driving" (ie. not heel-toeing) we simply change down a gear and let the clutch out, the clutch grabs the flywheel, and the engine revs rise as you are decellerating.

Some of you that have done it from very high speeds have heard/felt the rear tires (or front if a front driver), go "Squeak" as you temporarily lock up the back wheels. This is called "Compression Lock" - where the lower gear makes the engine spin higher than it is physically able to. And it temporarily locks the engine from turning. The wheels spin due to the lack of traction, and resume turning when the car slows enough for the wheels to meet the operable rev range of the engine. Bigger the compression lock, bigger the tire squeal or 'lock'. Some people think this is fun.....wrecks the car if you keep doing it!

So, let's get back to heel toeing. As I said earlier, heel-toeing is where you match the revs to the lower gear that you are about to select. The theory is that as you perfectly match the revs, you:

a. will not get compression lock - which 'could' lead to an accident situation or at the very least, damaged mechanicals
b. allow for smooth movements and weight transfer of the car so that equates to faster times on the track (or road) and;
c. you are more "mechanically sympathetic" on the car and not asking it to do something that it is incapable of. Car will last longer and show less wear

Here's how to do it:

As you slow down, and are about to change gear, JUST after you depress the clutch, with the ball (bit below the toes) of your right foot, roll it over on the accellerator using your heel as the pivot (whilst you are still braking!). Most of your foot still stays on the brake and this is where most of the pressure from your right foot is. You want to raise the revs after you have disengaged the clutch - so you don't jerk forward under accelleration.

'Blipping' the throttle with the clutch out will raise the revs, and, as you then select the lower gear, let the clutch out and the revs should also begin to drop. The gear will then meet the engine revs at the perfect point if you get it right.

The perfect analogy is to think of a baton race. The guy who starts running to get the baton, MUST be at the same speed as the guy who is handing him the baton. If the speeds are identical, the change will be perfect. If one of them is not going the same speed as the other, the change over will be jeapordized and it could fail. Assuming that the 'handing over' guy is running faster than the receiving guy and doesn't slow for the other guy, the receiving guy then has to run faster to just catch the handing guy who has just run past him! Same philosophy with the gears. The clutch has to work double time as it brings itself up to speed with the flywheel. This stresses the gears as well as the clutch. If the two are going the same speed, then the 'mating' is much more attanable and harmonious.

At the point of clutch engagement, you want to aim to have the revs AT THE HIGHEST POINT where they would have been HAD YOU just released the clutch without matching the revs. ie. lazy driving. In other words, if you WEREN'T doing the heel toe thing.....the HIGHEST point that your revs went to AFTER you released the clutch and the revs went up, is the rev point that YOU WANT the revs to be at when you are doing the heel-toe. This is the matching or "meshing" point. That way, the engine doesn't have to play "catch up" with the clutch!

You can practice rolling your right foot when the car is stopped. Just leave your foot aligned with the brake, and pivot with the heel, but roll the ball of your foot over to the accellerator. You are in effect, "pinching" the throttle just to raise the revs somewhat. Then, you can translate it to the downshift practice and try to get one fluid movement. Eventually it becomes second nature and you do it totally subconsciously!

I hope this helps. You will realy save your clutch and transmision by learning this technique. Plus, it adds so much more enjoyment to driving a manual/stick transmission. After you master it, you'll wonder how you ever got along without it!

Cheers,

BTW, any of you who ride motorbikes probably already do this now without even thinking....as compression lock on a bike is WAAAAY more serious than in a car. It's the same principle.

 

Very good Sime. I've driven both bike and cars that ways since I got my licence. Always thought it was the right thing to do. I know I'm doing it right when I don't see the passenger's head move on a down shift. Smooth just like an automatic transmission. Look at my sig. My slammer is on her second clutch in 220K miles. I don't actually downshift every gear approaching stop lights but I do it if the light changes or a turn is comming.

 

Sime, thanks so much for the explanation. As someone totally new to a manual, I could still go through the steps you described in my mind.

Care to explain what double-clutching is?

 

Good detail on h/t'ing, Sime...nice job.

As for braking with the engine, The Rev is correct when he says that the parts that take the most damage are the clutch and tranny. It's going to cause premature wear/failure if you do it too often and especially if you don't rev match.

And on a racetrack, the only reason you downshift coming into a turn is so that you can be in the correct gear AFTER the turn. These days "slowing the car" with by downshifting isn't necesary.

Unless you like to trail brake (something I don't do), you want to be finished with the downshift before turn in, which means that you are also done with braking before turn in.

Anyway, downshifting to slow the car is...bad...ummmkay?