Suspension question for folks who’ve had German cars

[Dangerous Fish]

If you brake (or regen) while taking a high speed turn on a fairly balanced car you're almost certainly going to have some oversteer from the weight transfer robbing you of rear end grip. I think the "problem" (if you want to call it that) is that many people are not expecting to have that effect on the car's balance when lifting off the throttle. It's definitely something that takes some getting used to OR you can simply change the settings to make it less of an impact.

I've raced FWD cars in the past which were set up to be very tail-happy. There has been a long history of one-make racing in the UK where small FWD cars such as the Ford Fiesta, Renault 5 & Clio, Mini etc. raced against each other with minimal modifcations to the engine allowed, so it was all about getting the best suspension set up to bring you to the front of the grid.

Most of these cars inherently understeer. They're designed that way (like most cars these days) to be safer on the road. When you take them racing, various alignment and hardware changes are made to try and cancel out that characteristic but that means the fastest cars are often the ones most difficult to drive. You'd come into a corner and have to be fully committed with the throttle all the way through to stop the back from stepping out. They were on a knife edge. If you did lift and got a big oversteer moment, the only way to get it back was to bury the throttle pedal so the front pulls the car back in line. That technique is counter-intuitive to some, but you soon learnt it otherwise you'd soon be on a one-way trip to the Armco.

The same can happen with a RWD car on a trailing throttle into a corner where engine braking on the rear wheels can provoke some oversteer. With some cars and setups, that can also take a lot of commitment to control it.

With an AWD car, the tendency is often still for it to understeer on corner entry if not enough weight is over the front axle but then the application of more throttle feeds power to the rear to balance that out. The P3D behaves in a similar way to that a lot of the time I'd say (with around 50/50 balance set).

What I've found with the P3D is not so much what happens when you deliberately lift off the throttle to prevoke some oversteer, or cancel out understeer on corner entry or mid-corner. That can be beneficial and a faster way if done right. No, what I'm describing is what happens when you are at the point where your entry speed is optimal or maybe just a little too fast and you're off the brake and haven't started to apply any throttle. If you don't left foot brake, that could be at the point you're moving your foot from the brake to the gas pedal. At that exact moment, the regen comes in and it induces oversteer, even with the car hardly turned in and it can happen very quickly. So then you either need to get on the throttle and hope the front motor pulls you out and/or correct the slide with steering and hope you don't run out of lock.

It's unlike the behaviour I've experienced with FWD or RWD cars and personally I don't like it, but that's not to say some other P3D drivers won't just find a way to use it to their benefit to make them faster or find a way to tune it out other than reducing the amount of regen in track mode. For me, having the regen slider there so I can tune it in real time is very handy and I'll be using it. In the future, the ability to programme in different settings for all the sliders at different points around a track would be awesome IMO. Let's face it, almost anything's possible with Tesla. Even what we have now would have been unobtainable on professional race and rally cars not that long ago. I showed track mode to a pro race driver yesterday and he was blown away by what it can do. But there's not going to be a 'one setting for all' with it.

So, a long winded way of saying "everyone's driving style is different" maybe, but since the Model 3 was released I've been reading these forums and read quite a few threads where it's been criticized for been unstable or twitchy particularly on high speed, sweeping curves and I now wonder if the regen contributes to this.

One more thing - why have Tesla put a regen slider in track mode if it wasn't to help with some aspect of the handling/balance? I wouldn't say it's going to help much with brake balance but I could be wrong.

If someone could get Randy Pobst's views on all of this, that would be useful as he helped programme track mode initially.

Maybe this long post has explained what I was trying to say yesterday a bit better?

I'll shut up now.

 

[Dangerous Fish]

I would still be interested in the full setup of your car.

VIR has some high speed turns (back straight esses 100mph+, Turn 10 sharp 90mph corner, Turn 14, Turn 17) and I haven't noticed the liftoff oversteer you are describing. I didn't notice it at Lime Rock either coming on to the front straight at 100mph.

Do you have any video with data overlays from laps you've done at these you can share? Would be useful to see your throttle/brake inputs and the car's power output.

I've mentioned elsewhere I've got the Redwood/Ohlins coilovers and arms from Redwood and MPP on mine now. The alignment is not vastly different to stock other than more front and rear negative camber. I've spent quite a bit of time in the last 2 months getting it set up for the track and I'm very happy with it overall. Yes, I'm sure I could change alignment settings to tune out what I'm feeling, but alignmnet isn't the root cause and would just end up creating a different issue somewhere else. All IMO.

 

[MasterC17]

Do you have any video with data overlays from laps you've done at these you can share? Would be useful to see your throttle/brake inputs and the car's power output.

I've mentioned elsewhere I've got the Redwood/Ohlins coilovers and arms from Redwood and MPP on mine now. The alignment is not vastly different to stock other than more front and rear negative camber. I've spent quite a bit of time in the last 2 months getting it set up for the track and I'm very happy with it overall. Yes, I'm sure I could change alignment settings to tune out what I'm feeling, but alignmnet isn't the root cause and would just end up creating a different issue somewhere else. All IMO.

One thing you mentioned above that I had not considered is left foot braking. I left foot brake, so it gives me control over the throttle constantly.

With your more clear description, I can say I have felt a few times where the car would understeer and the rear end would start to get loose, but I would just bury the throttle and pull right through it, so I did not think much of it. Good discussion! What size tires are you running? I also noticed when my front sway bar end links were pre-loaded improperly I noticed this to a much larger degree.

Here's video with data:

 

[Dangerous Fish]

One thing you mentioned above that I had not considered is left foot braking. I left foot brake, so it gives me control over the throttle constantly.

With your more clear description, I can say I have felt a few times where the car would understeer and the rear end would start to get loose, but I would just bury the throttle and pull right through it, so I did not think much of it. Good discussion! What size tires are you running? I also noticed when my front sway bar end links were pre-loaded improperly I noticed this to a much larger degree.

Yes, I think left foot braking is going to make a difference. If you can keep a tiny bit of throttle on all the time in the entry phase of a corner you may find you get almost no regen. It's effectively a dynamic way of controlling the regen. I've never been a left foot braker, so I'm bound to approach things differently and having a way of controlling it with track mode is fine for my style.

That second video of yours is very useful. What I've done in RR is make the range of the 'power' bar from -160 to 400 so it displays the regen as well as the power output on the same bar. That makes it easy to see how much regen you're getting. I'll have some video to show at some point to illustrate my point and you'll see how that looks.

Tyre-wise I run 265/35 19 (square) on track but the car behaves the same in this respect the standard 20" PS4Ss.

I'd also add that I felt this happening the very first time I took my car on track a week after picking it up when it was totally stock. I've been trying to pinpoint the cause ever since. I also had the alignment checked before that first track day and it was all within specs, so there's nothing inherently wrong with the chassis. Unless I've got some deep-rooted issue with the way the motors/regen are operating I can't see it's anything to do with alignment, suspension, tyres etc.

I could blame the driver of course, but once I started looking closely at the data and spent the time testing yesterday I think I'm comfortable it isn't ALL my fault.

 

[Dangerous Fish]

Watching that VIR lap (which you drove very nicely and with plenty of commitment!) it's clear there are hardly any moments when you're not either on the throttle or the brake (even slightly) which is exactly how it should be, but difficult to always achieve and more so if you only use one foot like me.

So it's back to different driving styles influencing how the car behaves I guess.

 

[MasterC17]

Watching that VIR lap (which you drove very nicely and with plenty of commitment!) it's clear there are hardly any moments when you're not either on the throttle or the brake (even slightly) which is exactly how it should be, but difficult to always achieve and more so if you only use one foot like me.

So it's back to different driving styles influencing how the car behaves I guess.

Thanks! I've had 12 track days at VIR in the past year and a half, and each visit I find a little bit more time! I hadn't been to Lime Rock in 5 years, so I definitely left some time on the table especially in Turn 1/2.

Just start left foot braking now (start on the street); it will take several months to get good at it but it's so much better once you do.

 

[Dangerous Fish]

Thanks! I've had 12 track days at VIR in the past year and a half, and each visit I find a little bit more time! I hadn't been to Lime Rock in 5 years, so I definitely left some time on the table especially in Turn 1/2.

Just start left foot braking now (start on the street); it will take several months to get good at it but it's so much better once you do.

I may just be too stuck in my ways to change now. I've driven manual gearboxes all my life (other than rentals in the U.S.) so the Model 3 is really the first car I've had which I could drive with 2 feet all the time if I wanted to. I've used left foot braking in some cars on track when really necessary, but it doesn't come naturally to me.
I may give it a try at some point, but for now I'll stick to what I know works for me.

 

[MasterC17]

I may just be too stuck in my ways to change now. I've driven manual gearboxes all my life (other than rentals in the U.S.) so the Model 3 is really the first car I've had which I could drive with 2 feet all the time if I wanted to. I've used left foot braking in some cars on track when really necessary, but it doesn't come naturally to me.
I may give it a try at some point, but for now I'll stick to what I know works for me.

I had driven manuals (and still do) for years before I started left foot braking. Now I can switch between the two without even thinking about it. Any time I hop in a 2-pedal car I left foot brake, and any time I hop in a 3-pedal car I don't. Muscle memory is a pretty cool thing!

The first time I did it, I nearly went through the windshield. It get's better quickly lol

 

[Zcd1]

I may just be too stuck in my ways to change now. I've driven manual gearboxes all my life (other than rentals in the U.S.) so the Model 3 is really the first car I've had which I could drive with 2 feet all the time if I wanted to. I've used left foot braking in some cars on track when really necessary, but it doesn't come naturally to me.
I may give it a try at some point, but for now I'll stick to what I know works for me.

Learning to be fast and smooth on track in any car takes practice. The Model 3 requires finer/less binary throttle control during all phases of cornering due to the instantaneous throttle response.

 

[Dangerous Fish]

Learning to be fast and smooth on track in any car takes practice. The Model 3 requires finer/less binary throttle control during all phases of cornering due to the instantaneous throttle response.

I don't have much of an issue driving fast and smooth in the Model 3, but I don't want it to decide to use regen when I don't want/need it, especially if it unsettles the rear.

I also don't want unnecessary regen in the entry/mid point of a corner if I'm off the throttle as it's slowing the car. I want to carry as much speed as possible through that corner.

 

[Dangerous Fish]

I've had a closer look at the data and video I recorded when testing last week. Up to now my understanding was that regen only works on the rear motor on the P3D but that's only the case when in normal driving mode. In track mode, there's regen from both motors and the amount and ratio depends on the slider and also whether the car is on a straight or in a corner.

There's more rear regen when lifting on a straight and more front regen lifting in a corner. I think now the corner where I encountered the imbalance is just an unusual combination where the attitude of the car and the lack of throttle input just before turn in led to the snap oversteer, but it's still a consequence of the regen IMO, so I'll be trying different amounts of regen from now on to see if I can find a sweet spot.

On another point, I don't think the power loss from changing the balance from 50/50 is much of a concern. I've seen the thread where someone tested 50/50 and 0/100 and the overall loss was around 7%. It'll be less at 25/75 and I'd personally rather have a slightly less powerful car with good balance than vice versa, especially in the wet.

Anyway, more testing required (as always) so I better book more track time...