Best way to slow down.

If I'm coming to a light or off the highway,I will put it neutral and use the brakes. I figure it saves clutch wear. Probably more break wear. Is it important to down shift and engine break
..?

 

This is the Tracking and Driver Education Forum, totally different style of driving.

 

My namesake is correct, the street and the track require totally different styles of driving but I tend to mix the two for fun and practice on the street. What car are you talking about?

 

Track use brakes and gears for control. Street shift into N and use just the brakes.
GTS Bruce

 

Engine braking is a holdover from old times when brakes were not so good. I was taught to engine brake in Driver's Ed in the early 70's. Many cars back then still had drum brakes or a drum/disc combination.

The thinking now is never use engine braking except in an emergency (like when your brakes fail). Modern brakes (usually discs at all 4 corners) will stop the car. It's much cheaper and easier to replace pads and discs than it is to replace a clutch or transmission. So-Never use the engine for braking. It puts a lot of stress on driveline components and is totally unnecessary.

On the track I would never use engine braking for the above reason, plus:
1) it induces a rapid weight shift which can upset the car just as you are going into a turn. You can modulate weight transfer with brakes, but you can't modulate a shift from let's say 5th to 3rd without a lot of clutch slippage. Then you soon need a new clutch.
2) It is a slow way to slow down.

Downshift "blips" are not engine braking. They are just rev-matching for a smooth shift.

 

Really? I think it's the opposite of what you claim.

Engine braking places its braking effect mainly on the drive wheels (rear wheel for Fcars) while regular braking causes a forward weight transfer on to the front wheels. When combined with judicious control of the brakes, careful rev matching can add engine braking to reduce front end dive (weight transfer) and set up the chassis for faster corner entry and faster exits.

If you are trying to slow down while entering a corner, engine braking will set up the car's suspension to reduce weight transfer to the front, reducing understeer while OTOH sole reliance on regular braking into a corner will promote understeer and scrubbing. You always want your front wheels to run as freely as possible when you steer with them. Over-reliance on the brakes will slow you down unnecessarily in the corners.

The other nasty effect of too much weight transfer on to the front wheels from regular braking is that the rear suspension will be lightened, decompress and lift. The lightened rear end will reduce traction on the rear tires and increase the possibility of a loss of control. We all know big rear wings provide their benefits in the corners where they create downforce on the rear wheels, to improve traction and control. You want the whole car to hunker down, not tilt or dive forward.

I think you're worrying too much about clutch wear. Watch a video of 599XXs or LaFs on a race course... and listen as they enter and approach the apex in their turns. You'll hear 2 or 3 big timed downshifts. These cars have F1 shifters and trannies that could automatically downshift for the drivers if they had wanted to avoid engine braking but the drivers always purposely downshift earlier, before the system picks a lower gear for them, in order to create some engine braking to set up the chassis for better (more neutral) cornering. IMO, engine braking in performance driving is not done to compensate for inadequate old-fashioned brakes. It's used to balance the braking effort between the front and rear wheels.

FWIW, I always brake and downshift at the same time. I've never replaced a clutch or tranny.

 

the previous poster is correct.

weight transfer occurs no matter what you use to slow the car. when you arrest the speed of an object the forward force is transmitted to the forward part of the object until its slowed to a halt. regardless of using either brakes or engine braking - the force will be transmitted to the front of the car. Brakes are much better to use to slow the car, because you can modulate the smoothness of applying the brakes vs. applying or decelerating the car.

when you see modern F-1 or FXX's slowing down they are not using engine braking to slow the car - rather to balance the car for the exit of the turn. the exit of a corner is WAY more important than the entry. with modern cars it all happens so much faster, so its hard to tell.

in classic driving - with a manual transmission - you should always apply the brakes first - then match the speed with the engine using engine braking ( in an old car - 40's to 70's ) ... otherwise use the brakes... not only are they cheaper to replace, they are much easier to use and control.

the blips you see are in deed correct used to speed up the gear you are down shifting to... so that it is spinning closer to the gear you are selecting.

 

Spot on..

 

You're reading my message incorrectly. Read what I wrote again. I did not say don't use your brakes. I said several times, use both braking and engine braking at the same time.

No sane driver will purposely downshift without braking - that's how you overrev engines. I always begin braking and then downshift while I continue to brake. While it can take a bit of fancy left-footwork in stick shift cars, this feat is achieved very easily with F1 paddles. It's one of the main reasons I like driving F1 paddle cars.

Some people on this thread do not understand the useful effects of engine braking and now you are misrepresenting what I wrote on top of that... and saying solly is correct. Bravo Spirot.

Engine braking reduces the tendency to transfer weight to the front. You won't convince me that if the rear wheels go slower than the front wheels, the rear end will still want to tip over to the front as much as if the rear was going faster than the front (front brake bias). Engine braking is about keeping the suspension compressed all-round and balanced. You do not want any corner of the car becoming light and lifted. You want all 4 corners pressed tightly onto the road. especially in the corners.

Most braking is done by the front brakes. Adding engine braking in a RWD car simply reduces that imbalance in braking, reducing the tendency to pitch forward during hard braking, helping the driver maintain control. If you are a good driver you will FEEL this effect on your butt and you won't need me to explain it to you. And you can modulate a downshift... by careful braking before you downshift, not by slipping the clutch.

IMO, you guys need to analyse the mechanics of a maneuver as well as carefully read other people's messages before jumping to conclusions.

 

Tree's
Wall's
Buildings

 

Michael

With due respect, this reminds me of your argument a while back about engaging neutral as a recovery mechanism when a car is sliding, and the contention that F1 drivers have the neutral button near their thumbs to engage it when losing control...

Engine braking does decelerate the car somewhat, but less than you think, especially compared to the use of brakes. Regardless of how much engine braking exists, the net effect on the car with any deceleration is to shift the weight FORWARD....i.e. front springs compress, rear springs decompress.

Example - take your California, stabilize at 40mph and downshift quickly (no brakes) to 1st gear. The engine will blip to accept the gear change, and it will feel like you threw an anchor out of the car - but the nose will dive. More weight goes on the front. If you did that on a "regular" manual car, you're likely to get rear tire chirp, if not hop, as the rear suspension is unloaded. My wife and daughter do that in our FWD Fiat sometimes, feels like the rear wheels are coming off the ground..

In cornering, the idea is to keep a stable platform on the chassis - to optimize grip, which allows a high minimum speed and balanced car - and then allows early and maximum power application. That's why the magic sauce of good drivers isn't how hard they brake, it's how well they release the brake pedal, particularly in relation to steering inputs. It's also why the art of trail-braking isn't to slow the car down, but to maintain weight forward on the outside wheel. Power ("maintenance throttle" in rare cases) is what gets the rear end to squat, as the weight is transferred backwards.

Engineer to Win Understanding Race Car Dynamics: Carroll Smith: 0752748318687: Amazon.com: Books

good reference on vehicle physics; it's focused on racing, but luckily the laws of physics apply the same to road cars too

 

4th_gear:
you just plain are misunderstanding the physics at work.

Deceleration causes weight transfer. End of story.
Brakes are already biased to provide a reasonable amount of rear braking. True, you can usually add a little more via engine braking due to the conservative nature of engineers.

However, the suggestion to modulate your downshift by careful braking before the downshift, sounds like reduce your braking so you can add more engine braking at the rear...while reducing the front braking that we all agree is the most important!

 

First of all, dragging in unresolved arguments from other discussions is a bit like the way the Russians like to create unresolved conflicts - it's meant to harass your opponent, not to resolve any past disagreements or any new ones for that matter. Please grow up and move on.

WRONG.

Actually, your bodies are pitching forward against your seatbelts and are bending at the waist... because you are GOING FASTER than the rest of the car. YOUR HEAD IS NOSE-DIVING, NOT THE CAR. The car is just slowing down real fast. That's how powerful engine braking can be.

Still unconvinced? Then try this explanation. I regularly train on bikes, the kind you have to provide leg power for.

You ever ride a bike? Try going really fast on a flat section then grab hard on the front brake - where do you end up? Right over the handlebars! This is because you and the rear of the bike are now going a lot faster than the "stopped" front wheel and the front wheel acts as a pivot. This is a demo of 100% front brake bias - massive front weight transfer.

Now do the same thing again but only grab the rear brakes. What happens? Your rear tire starts to skid but you don't go over the handlebars because your body is going at the same velocity as your front wheel and the rear wheel is the pivot. Since you are in front of the pivot, there is no pitching or pivoting even though you are still going faster than the rear "stopped" wheel. This is 100% rear brake bias - no front weight transfer. The bike does not pitch forward.

Since the force of engine braking is transferred through the driveline where the rear driving tires are in contact with the ground it effectively increases the amount of rear brake bias.

Sorry but if you only apply brakes when you corner I have to disagree with that technique. Remember, I am advocating simultaneous braking and engine braking.

Although I figured it out myself apparently I am not the first person on FChat to point this out. ...And here's the actual 2008 FChat posting in case you don't want to read it. F1 cars have provisions for dynamically adjusting brake bias. Since regular road cars cannot dynamically adjust brake bias, a combination of careful braking and engine braking results in superior chassis balance when braking hard.

Image Unavailable, Please Login ​

 

What's the best oil to use in an 348?

 

No, I just don't slam on the brakes when I set up for a corner. I downshift as I apply brakes and feel the car slowing. This allows me to use a bit of engine drag to balance the braking bias. I continue to brake and apply more engine braking if the car needs to slow further. I also continue to apply some throttle in between downshifts. The added weight and traction retention on the rear wheels allow me to put more power down on exiting the corner. I fly past cars that only use brakes and stay off the throttle.

IMO it's very poor technique to only rely on brakes in corners because the suspension will get unhinged.

 

So you want to post off topic when you have nothing useful to contribute? Interesting.

 

1) the bike metaphor is interesting - the difference is cars have suspensions, bikes do not, and cars in motion are subject to pitch, roll and yaw

2)current Ferrari's, and most cars with ABS, actually have EBD - electronic brake distribution. Even so, Ferrari (like most street car makers) over-bias the brakes towards the front.

3) my point about your "neutral" assertions was not to drag up the past, merely to point out that you would likely enjoy actually learning about vehicle dynamics and associated physics to better inform your point of view.

 

2002 360

 

This seemed to fall under the "driver education" part of the title.

 

You lost me when you said the car's nose doesn't dive.. I can use the other car's nose dive during threshold braking to tell me when he is braking when alongside in a race.. He must have been engine braking and I was just confused. I'll say it from my prospective as a racer. I do not intentionally use my engine to slow down, ever. I use my brakes to achieve the proper speed and initial rotation and downshift to have my car in the proper gear for mid-corner and exit. That's it, all I have.

 

Bikes also pitch, roll and yaw; but because bikes only have 2 wheels, no cockpit, cyclists want to avoid pronounced examples of those movements. Bikes also have suspensions but only some have shock absorbers. Instead weight and changes in momentum are absorbed by special materials including CF, double/triple-butted metal tubing as well as specially-design frame geometry.

But none of this makes any difference to my bike braking example because it is an absolutely clear demonstration of weight transfer due to rapid sudden braking.

If your car's suspension is unsettled when you brake, especially while cornering it doesn't matter what sort of 3-letter acronym is associated with your car, if you need to re-balance the suspension during the maneuver engine braking will do that if you apply it properly. I'm just flabbergasted that no one has felt their car tuck in and hunker down when they downshift properly for a corner.

I suggest you stop dragging up unresolved past discussions out of context because they are unrelated and unresolved. Attempting to do so is just a lame way of deflecting the current discussion by trying to cast unsubstantiated doubt on the other person. This sort of tactic has no respectful merit. So just stop it.

I happen to understand driving and physics better than you think or want to admit.

 

to each your own. I did not mean to malign you and your driving prowess. However from personaly racing Formula cars - before paddle shifters - I simply do not agree with your statements - does not mean you are wrong... ( but for me you are ) ... I'll drive my way ... you drive your way. As I cant think in miliseconed like the shift speed on a Ferrari... I;ll just do it my way.


as for your bike reference - there is very little suspension in a road bike. however tire deflection happens when you apply the rear brake...your body moving forward is Newtons first law of Motion - a body in motion tends to stay in motion... kind of thing.

F-1 cars that your past post suggests - is about the cross braking ... and how to "fake" stability control. the only way adding more fuel to a car can stop forward pitch ... is to accelerate that wheel... taking the pitch away... which further points to my statement that all weight pitches to the front regardless of what brakes are being used - engine braking or not.

simply put your car in 3rd gear - and shift to 1st at 20 MPH. you get a huge dive ... that is just using engine braking. ( if you go real fast you'll get diff lock up... not fun.)

Further - I'm very fortunate to know a number of drivers - F-1, past and present...( not well, but know them ) I've never heard anyone talking about slowing down then shifting to balance the car using engine braking

 

The whole suspension of a car will compress regardless of brake bias (and will dive if your friend's car has a sloppy front end or excessive front end braking bias). However, if his suspension is well-balanced and he is applying judicious amount of brakes and engine braking, his car will just hunker down lower without a noticeable front end dive. I gather you agree it's bad to have your front end dive.

Your brakes will slow the car down and you will brake according to how the brakes affect the yaw and understeer/oversteer balance but you will not get the optimum corner entry/exit speed if you do not explore the benefits of engine braking to maintain optimum traction and optimum loading of the suspension.

What you want is the whole car to HUNKER DOWN as you enter the corner. Braking alone won't do this because the rear suspension is not compressing as much as the front end (unless you use a big rear wing or something similar but that causes drag along the straights). You won't have optimum traction on your drive wheels if you don't compress the rear suspension. The nice thing about judicious use of engine braking is that you can do it in any car where you have good control of the downshifts.

 

My bike tires are at 80/105 PSI (other people use 120/120 PSI) and total weight is less than 200 lbs (approx. 185 lbs). Tire deflection is negligible or non-existent on a racing bike. But again, my bike example is not about suspensions, it's a very pure demonstration of how the mass of the bike is distributed over the front and back wheels during front and rear brake bias situations.

It's not about suspensions.

No, there are 2 situations in F-1 engine braking. You are not being honest. You conveniently only refer to 1 of the situations mentioned in the F-1 Fchat discussion. The situation you refer to is where there is too much driveline drag, causing oversteer, so the system applies a bit of throttle to relieve it.

The second situation, which you conveniently omit, is where the front end understeers due to excessive front end brake bias. The F-1 system would then apply engine-braking and reduce understeer. The F-1 engine braking reference specifically points to it affecting the braking system bias.

You need to be more transparent and sincere in your discussion. We should be pursuing knowledge not just personal advantage. Other people have to read this stuff and I would not feel right if I were not being honest.

That pitch you refer to, if it is more than just overall suspension compression, is not due to brake bias. It' simply the suspension absorbing the energy from the car's change in momentum. The energy has to be absorbed. If the front suspension is a bit soft, it will compress more than the rear. With the California having a 43/57 rear weight bias, it should help keep it in check. But again, that is not caused by a brake system bias because what you suggest is just throttle lift-off with no mention of braking.

Oh well, but judging from videos of F1 races as well as XX Fcars, they all do it... all the same, don't they?

They don't just brake and downshift once as they approach the apex. They continually downshift (and brake hard) as they go through a corner, 2,3, 4 and sometimes 5 times. They do this because engine braking maintains a balanced load on the suspension and also allows them to play with the throttle even in middle of the corners. Whereas if they just brake hard, they are no longer in proper gear and cannot apply throttle to affect the slip angle until they downshift to a proper gear.

 

Buy an F car without basic driving,mechanical,knowledge or skills. There are a # of books worth reading,techniques practiced and driving schools worth attending that will answer a lot of questions and build confidence. Top it off with some track days or even a racing school.Most important: Find your and the vehicles limits while having fun. GTS BRUCE