Downshifting
 

Hi all

A question on downshifting technique on track. Is there any mechanical concern with downshifting, say, from 5th to 2nd, or 5th to 3rd, or 4th to 2nd?

Or, to get into a bit of minutiae, say, shifting from 5th to 2nd, and running through the gears but NOT releasing the clutch until you reach the desired gear?

Most of the top guys I've rode along with will dutifully go through every gear, blipping and de-clutching accordingly. My skill level is not as high, and I am terrified of going from 5th to 2nd when I am looking for 4th and over-revving.

Ok, I'll take care of this one :)

I blew my engine (my old C2S) at Sebring last year because I couldn't heel & toe with the bucket seats. So I was downshifting from 4th to 2nd and over-revved the engine. And then poof! :D

The best reason to go through each gear is so that you don't over-rev the engine by downshifting multiple gears. When you downshift multiple gears you don't know what RPM you're going to end up in.

If you don't release the clutch there is no reason to run each gear.

Learn to heel-toe through each gear... 5th...4th...3rd..2nd...releasing the clutch with each gear. There is actually a nice rhythm to it that helps with braking. And by keeping the drivetrain engaged, you stop faster and keep the diff locked for more stability during braking. The key is the know when your speed is right for the each gear as you brake. It takes practice to get it done right.. so don't expect to nail it every time at first.

The synchromesh gearbox can easily accomplish a 5-3 or a 5-2 downshift in one motion if you do it late enough in the braking zone.

But.

If you are trying to improve yourself as a driver then doing it sequentially with full clutch release will teach you proper technique in case you get into a real race car. Even if you never get to drive a race car with a sequential unit it is still good to have the technique.

It's not too complicated to do but requires some practice. Initially your braking distances will increase so you might not win the DE championship but you will be doing the E part of DE.

If you are hard on the brakes to slow the car down, going thru the gears and engaging the clutch for each gear makes no sense. You slow the car to the correct speed in the shortest distance possible and engage the right gear. That's just wasted motion and you will end up distracting yourself. Finding the right gear in a hurry is another matter. If it helps you find the gear then by all means go thru the pattern in sequence, but double clutching for each gear just adds wear and tear and slows you down.

I shift from 5th to 3rd after the long straight at my local track, no problems. Make sure you are relaxed and know exactly where the gear shift is, blip the throttle at the correct speed and go into the lower gear. There is less wear and tear on the car using the brakes rather than the transmission, and a lot less work. Some guys just enjoy doing it the other way, or in a race it may be of some use in tricky situations, otherwise why bother. Simple is better in my book.

what ... no one mentioned "get a PDK" ... sheesh you guys are slipping like a GT3 LSD ... :D

it may actually help to release the clutch while passing thru neutral on the way to the lower gear ... you MUST (regardless) ensure that you blip (rev match) the engine before releasing the clutch in the new lower gear ... failure to do so will result in ... 1) a nasty jerk as the revs match, and potentially 2) an overrev situation (say "bye bye valves - hello expensive engine rebuild")

Yeah... PDK it is, and I have used a manual many, many years. I bet next year the first GT3 w/ PDK will be here. :)

Re multiple downshifting... try downshifting from 130MPH to 40MPH, 4th (or 5th) to 2nd on your way to Turn 2 at Laguna. Perhaps it can be done, but I bet it's not pretty.

5th to 3rd is a pretty normal downshift for me, for instance at T1 at the Glen. Just take your time in neutral and I often do 2 blips to be sure the revs are good.

Thanks all.

Am glad I'm not the only one who skips down a gear sometimes. I always blip the throttle, and actually to go from 4-3-2 I find a lot easier than going from 5-4-3. I wind up going 5-3, The 5-4 shift just isn't that comfortable, but then again is the shift that I think most of us have the LEAST experience doing in a hurry.

Looking at the other thread that Slow referred, I didn't really see a consensus, except that skipping a downshift works the synchros harder. How much harder? Does it make a difference?

Am practising as much as I can. But am still a little green - right now my focus is to blip the throttle WITHOUT losing brake pressure, something that I am getting proficient at when downshifting only 1 year (less foot movement) but with multiple downchanges I just can't control the brakes properly...

ONE GEAR AT A TIME, IF YOU CAN'T ACCOMPLISH THAT THEN PDK. YOU THINK Walter Röhrl slams it from 5 to 2? More then likely you only need to go to 3rd.

This equation leaves you with much too much time off of the gas resulting time and position loss IMHO....just sayin'

You may be right but I doubt it. I'm under full brake while this is going on so I can't see how I'm losing time on the gas. OTOH, you're driving and racing an RSR so I assume you know whereof you speak.

At no point on a track should you be in neutral. You should A.) always be in a gear and B.) you must be either on gas or braking..never coasting. If you need to avoid something, how can you in neutral? What if your braking and someone spins right in front of you and you need to avoid them? That is why race driver downshift thought the gears... as you need to be able to control the car in any situation. And again, your braking will be much more stable with the drivetrain engaged. Start slow and work your up to speed. Each person develops their skills at a different rate. Don't be in a rush. Work on being smooth...and the speed and lower lap times will come. Better to learn the fundamentals and good habits now, so you don't have to change later.

skilful drivers change gear (yes - double declutch whilst braking) without having to think about it. The only way to achieve that level of learned familiarity is by double-declutching and 'heel-and-toe' (for want of a better word) ALL THE TIME - shopping, commuting, trailering, tractoring, at the track, wherever you go. so that you 'Joest Do It'.

'Heel-and-toe' is a disservice, in most vehicles, its 'toe-and-another-part-of the foot-but-never-the-heel'.

With modern brake systems, the need to go down through the gears one by one is no longer paramount, engine braking is dwarfed by the hugely greater effect of the brakes themselves. It may depend on what else you are doing. in many cars ESP/TC is less intrusive in a higher gear. Very often when driving round the outside you are slightly overgeared in the first part of the corner (and remember even at the F1 level, you can almost always drive round the outside) so that you are perfectly placed to get out of the corner better than the other guy.

It is very noticeable that the faster cars at endurance events change gear less often than the slower cars. One of the reasons for double declutching is to be less harsh on the car, so that it lasts.

Just double declutch everywhere you go - you know you are getting there when you no longer need to use the clutch (save this for the old pickup until you have the technique down pat) - its not a track-tool, its a driving tool.

R+C

Thanks Nordschleife

What is your definition of "double de-clutching"?

I do try to heal-and-toe (which is actually more like ball of foot with side of foot) whenever I can. Carrying a higher gear through a corner also encourages you to carry more speed (so that you are more in the power band). I try to do that as much as possible.

Downshifting through 2 gears (4-3-2) correctly is something I am OK at. Downshifting through 3 gears (5-4-3-2) I just can't manage; I am not quick enough through the gears and the car scrubs off so much speed so quickly that I wind up turning in already and either in neutral or in the middle of a gear change. So I "cheat" by going 5-3-2. The gearbox also seems to "accept" a 5-3 change much more than a 4-2 change. Maybe its my imagination, or that my forward gear movement is more precise that my rearward (moving lever up vs. down).

I do eventually want to get into a race car, but I've told myself not to waste my money until I can drive my road car to a very high level of skill. Then again, I suspect downshifting a sequential box is easier than an H-box.

To me it is: Clutch in, neutral, clutch out throttle keep revs up near revs of next gear, clutch in next gear revs matched. up or down the same way.
If you do it right and have a feel for car/track transmission you no longer need the clutch.

Used to be able to double clutch (Had to in old truck) and tried it for a few laps while on track, but it just seems to cost some time and I am a super slow shifter on track as it is.

But Nordschleife is right, practice rev matching everywhere. On cold trans the upshift the lever moves into gear so slow I match revs as the revs drop off to idle. Even puttering around Florida I do it without thinking.
Hard to get enough speed and to actually match revs as i can barely reach the pedal with cold tires and you sound like a moron, but then again driving around in a car with numbers on, you look like one anyway :-)

as trakcar says

to make it more straight forward, don't think of changing gear from 3 to 2, for example, but from 3 to N and then N to 2 (where N is Neutral), whether you are going up or down the box, you should move the gear lever along the natural planes of the gear shift gate, so going from 2 to 3 is 'up in a slightly offset direction, relax the wrist to let the lever springing align it with the 3-4 axis, then up from the 'middle', 'sprung' or 'natural' neutral position, in a less offset direction to the third gear position.

ramming the gear in a diagonal direction from 2 to 3 is not a great idea.

Strangely, the better you change gear, the less need there is to do so in a wink of a gnat's arse.

R+C

Well put!

I am amazed at how fast I see cars shifting on the flatout video's compared to my slow motion action on my flatout video's (Click on my signature to see how slow I do everything lol).
I feel like I'm hurting the car with the riffle action shifts I see done often. Maybe in racing you will win time, but for DE, not worth it IMHO.

Even more so because I think the shifter, cables, clutch, pressure plate are the weak links in RS. I know some of it has been updated on 4.0, that should tell us that the 3.8 is on the limit when track used (abused).

Well, I just installed a sport clutch, flywheel and pulley on my gt3, and "rifle shot" is exactly how the box feels now. Plus I am forced to shift much faster to keep up with the flywheel. Downshifting is more intuitive now, because smaller blips yield bigger revs. I also cleaned up a misfire that was affecting my throttle response.

Still don't understand the need to double clutch. Definitely understand the 2-N-3 philosphy, I do that already I think. But the marginal benefit of double clutching will cost me 1) loads of time 2) open me up to a host of driving errors (like mistiming a shift movement while the clutch is out

My only addition to this conversation would be to say that if you are going to skip gears, please don't skip 3rd and drop it into 2nd. 2nd is the money gear. What I mean is that if you screw up the shift it's going to cost you a lot of money, and it's got more delicate dog teeth on it, so it's easier to screw up if you haven't properly double clutched and rev-matched as you enter the gear.
Pictures for reference.
3rd gear:
http://i205.photobucket.com/albums/b...0Stuff/3rd.jpg
2nd gear:
http://i205.photobucket.com/albums/b...0Stuff/2nd.jpg
In addition to the smaller teeth, 2nd is a 3 ring sychro assembly. If you replace those parts with Cup Car synchros it's more than $2000. And if you damage the teeth on the gear itself, you need a new mainshaft because both 1st and 2nd are integral to the mainshaft. Basically, if you screw up 2nd gear, you've got a $6000-7000 Oops on your hand. Not as expensive as an over-revved engine, but not cheap either.

So, if you are going to skip gears, stick to 6-4 or 5-3, but do NOT ever go 5-2 or 4-2. Put it in 3rd before you move over to 2.

Stickier tires and forget all about 2nd might be a solution :thumbup:

This is my fault for saying something imprecisely. When I say relax in neutral, I mean for maybe .5 seconds while downshifting. I didn't mean to suggest that you should roll into the corner in neutral, only that there is no need to rush the 5-3 shift while you are under full brake at or near the end of the brake zone.

I'm confused here. On my .2 (non RS), I get an indicated 147 or so at red line in fourth gear. Are you hitting speeds above that on the front straight at the Glen? If so, my hats off to you! I get to about 130+, 4 is fine with a shift to 3 for T1

Cheers,

R

I'm shifting to 5th before I'm bouncing off the rev limiter but I'm pretty close to red line so whatever that is... No way I'm looking at the speedo! You have to be pretty brave in T11 and if I'm not, I can't get to 5th by T1.

Thanks Matt, those are some nice photos. Had no idea 2nd was that important. Looks fragile too.

Haha, I agree about not looking at the speedo...that makes sense, I am not very brave in T11 and am only tracking out at about 95 mph.....I just can't seem to get over the wall looming up;)....

The .2 RS has a shorter final drive ratio. 5th gear comes up on most tracks where a non RS from 996 GT3 and up have pretty tall gears thus very rarely requiring 5th gear. At least with most drivers like us. I know guys getting into 5th with tall gears in places I can only dream of. Most of them are paid real money to drive cars fast.

I double clutch on downshifts, and I also like going down to each gear for timing. Skipping just feels strange to me. Let me share something I teach my students learning heel toe and proper downshifting called the rule of halves. I'll suggest Road Atlanta 10a for example. If you begin your braking at 200' in 5th gear, set up your 4th gear downshift at 100' marker (halfway), then time your 3rd gear downshift at 50' (halfway from your last downshift to turn in), and again 2nd at 25'. Since your rate of speed is decreasing, you have adequate time to make these shifts at the proper revs without a risk of over rev letting the clutch out with each shift. This works consistently in threshold braking situations with multiple downshifts.

I really like this idea. Will try it out for sure. Thanks for the tip.

Ahh, that makes sense!!!

Nice plan.

I hate that wall. And I have seen it reach out and grab a car.