Shock Adjustment for Understeer - Time Attrack

[260DET]

Situation is the hybrid Z tends towards understeer, particularly when there is insufficient weight transfer to the front, mostly but not always when turning in.

 

The low speed bump has been adjusted a few times, its very sensitive, too much and the tyres just lose grip completely and slide front and/or back. Take it off a few clicks and the car moves around a lot through high speed sweepers and tends to understeer badly in certain low/mid speed corners although rear end grip is then great. This is OK in some corners where the car can be driven in to the apex and the good rear grip can be used to power out of the corner. But in other corners this can't be done due to their configuration, in those corners the only way is to basically steer the car around the corner. Go too fast and the car pushes out and can only be retrieved by backing right off and even then it comes back reluctantly.

 

The recommended settings for normal bump and rebound have not been altered at all, basically because I'm not sure which way to go with them and the car feels good otherwise. So, any suggestions?

[johnc]

Situation is the hybrid Z tends towards understeer, particularly when there is insufficient weight transfer to the front, mostly but not always when turning in.

 

The low speed bump has been adjusted a few times, its very sensitive, too much and the tyres just lose grip completely and slide front and/or back. Take it off a few clicks and the car moves around a lot through high speed sweepers and tends to understeer badly in certain low/mid speed corners although rear end grip is then great. This is OK in some corners where the car can be driven in to the apex and the good rear grip can be used to power out of the corner. But in other corners this can't be done due to their configuration, in those corners the only way is to basically steer the car around the corner. Go too fast and the car pushes out and can only be retrieved by backing right off and even then it comes back reluctantly.

 

The recommended settings for normal bump and rebound have not been altered at all, basically because I'm not sure which way to go with them and the car feels good otherwise. So, any suggestions?

 

At turn-in are you popping off the brake pedal or slowly coming off the brake pedal? I have (had?) a tendency to pop off the brake pedal at turn-in after getting the downshifts done which quickly transferred weight off the front and made the car push through the first part of the turn. I worked hard to calm myself down coming into a comer (started braking a bit earlier, slowed my feet down) and that solved the problem - when I remember to do that. Problem always comes back when I get in a hurry or sloppy.

[260DET]

Been thinking about that John, the problematical corner is a slow 180 degrees at the top of a rise, my tendancy has been to rush up the rise, brake hard and then turn. Going to try to brake further and turn in with some forward momentum while still trail braking. That sound right?

[frank280zx]

Been thinking about that John, the problematical corner is a slow 180 degrees at the top of a rise, my tendancy has been to rush up the rise, brake hard and then turn. Going to try to brake further and turn in with some forward momentum while still trail braking. That sound right?

Any pictures of the turn, is it a steep rise? if the car has to much lift coming over the rise, it might help 'planting' your car first (much like i do with a couple of corners on the nurburgring)

[hoov100]

What are you're corner weights and what are the ride heights front and rear? I'm suspecting weight transfer issues. (obviously) What I'm interested in, is if you have solid mounted your sway bars to the control arms, because it almost sounds like the sway bar is not doing its job and is allowing the weight to transfer to the outside corner of the car and is also unloading the inside rear suspension causing even more unwanted weight transfer.

Edited May 18, 2010 by hoov100

[260DET]

One of the blokes who is pretty quick around the circuit has said if it handles at that particular corner it won't handle anywhere else Yeh Frank I think I know what you mean by 'planting' and thats probably the answer. Anyway pics may help, its a 180 degree right turn, in the pic below the car has reached about 100 degrees @ 90 KPH. In the linked video the corner entry commences at 0:51

The suspension is set up a little different in the video so ignore that.

Edited May 18, 2010 by 260DET

[frank280zx]

One of the blokes who is pretty quick around the circuit has said if it handles at that particular corner it won't handle anywhere else Yeh Frank I think I know what you mean by 'planting' and thats probably the answer. Anyway pics may help, its a 180 degree right turn, in the pic below the car has reached about 100 degrees @ 90 KPH. In the linked video the corner entry commences at 0:51

The suspension is set up a little different in the video so ignore that.

Note what happens to the Red Holden? (Looks like an opel but not exactly) he either downshifts and is 'fishtailing' all the way through.

How about turning in a bit later? Staying more left, you steer in way more early than i would much like the slomotion on this Mini

at 2:38 its the same turn. a late Apex would give you benefits in this turn (especially comming out of it..) if it is a 180 degree turn. The whole pack you are in is driving a defensive line!

Much like the picture below (i love google)

 

 

 

Now dont get me wrong but you leave allot of track unused, so my advise use more of it! I find that 180degree sweepers are best taking with a late apex as it leaves room to weave out in the rest of turn, instead of fighting understeer.

In most of your corners you choose the 'Geometric' Apex, It's very common for drivers to apex too early due to nerves about the approaching corner and eagerness as described in your previous post, to take the turn. The racing line apex in this corner is further round the corner than you expect. (This is where experience and track knowledge come in, but it seems you know your way around it fairly well)

 

my advise Apex a bit later in some turns!!

 

 

 

 

hope it helps.. though i dont know the track this is my advise to try and see what gives. it looks allot like one of the turns on the ring.

 

Other than that you might try hurtling towards this corner, and you turn the wheel and find yourself ploughing straight on easing off the throttle (much like john said in braking more gentle) It will result in a forwards weight transfer which will increase the available grip at the front wheels. Hopefully this should correct your course. If you're already off the gas, then a light dab on the brakes should help.

 

Anyway i learned a great deal from sitting next to a pro who was very gentle on brakes steering etc... haha what John said !

Edited May 18, 2010 by frank280zx

[Whittie]

Looks like a pretty tricky track there Rich!!

 

First things first, I'd be getting some gloves!

 

I don't want to be nit-picky, but there seems to be plenty of track that you aren't using on the inside and outside of a few corners, most pointedly the last corner (2:05)

 

For the particular corner in your question I would suggest, this will be hard to follow without showing you in person, but at 3:00 in the video I would be full throttle aiming for the right hand edge of that white sign and the very right hand edge of the inside of the corner. Braking hard in a straight line up hill and turning in tight for a late apex at the very last bit of the inside ripple strip on the way out for an early start on the throttle.

 

It looks VERY hard with the undulations, so take my word with a grain of salt considering I've never been there, but basically at 3:06 to 3:07 in that video you should be on full throttle aiming for the outside edge of the track. You are still coasting at this point. At 3:09 there is a bit of brown dirt on the outside edge of the track. I would be hitting the edge of the track at this point. I would then aim for the same inside apex you use on the last corner, flat stick, sliding to the outside edge of the track.

 

As frank280zx said, you seem to be apexing too early. This corner is followed by a reasonable straight and while you are following a good line for a double apex nuetral corner, by making it a single late apex you should get a faster run in, a slower mid corner, but a much faster late corner and exit.

 

You do a better job on the next lap, but I would still stay on the gas longer on the way in, tuck in more on the right hand side on the way in and apex later and drive out wider.

 

On the same next lap, during the left hander coming in to it I would stay on the gas more, drift right out to the right hand edge of the track, come back in to about half track instead of the left hand outer edge and then turn in to the right to hit the inside of the track, brake in a straight line towards the edge of that white sign and rip it around. At 5:09 where you are turning in from mid track I would be out towards the left hand edge(make a straight line toward the edge of the white sign and that is where I would be, at the same turn in angle you are at that time, but with more steering angle) and aiming for a much shallower exit. At 5:15 I'd already be on the outer edge of the track, full throttle, and then turning in much earlier for the last corner and riding it all the way out to the far edge.

 

Maybe stiffen the front sway bar a little to help that mid corner, neutral throttle, under-steer?

 

Hopefully that is understandable!

Edited May 18, 2010 by Whittie

[johnc]

One of the blokes who is pretty quick around the circuit has said if it handles at that particular corner it won't handle anywhere else

 

That is true at most race tracks. That 180 turn is not as important as the following right hand turn leading onto the front straight. Slow down a little more on corner entry to the 180 turn and focus on exit speed from that corner. Giving up a little at the start of the 180 may make you faster at the next right hander and onto the front straight. All the driving suggestions above are good ones.

[frank280zx]

Looks like a pretty tricky track there Rich!!

 

 

Whittie a lil topic hijack .. i demand more pictures of your car

[tube80z]

Been thinking about that John, the problematical corner is a slow 180 degrees at the top of a rise, my tendancy has been to rush up the rise, brake hard and then turn. Going to try to brake further and turn in with some forward momentum while still trail braking. That sound right?

 

If this corner is at the end of a straight your tires will cool down. Using the brakes really hard will help get them back up to temp. If you don't have them at the operating window you may chase your tail thinking it is a shock tuning/geometry issue.

 

Cary

[260DET]

Thanks all, after a bit more thought it may well be that the problem is a combination of driver and a very sensitive low speed bump adjustment.

 

After starting the topic I was reading some Penske shock tuning material, the comment there on how a car feels with loose low speed bump was exactly what I experienced last Sunday, that incar I posted above is not current. The car was moving around a lot through the high speed bendy bits, it had grip but felt very loose. What was good was that the car could be driven hard out of corners, a particularly good thing when you have power

 

So the low speed bump will be adjusted up by one click each end and I will try to do more suitable lines. And drive harder

 

On the circuit, Lakeside has a lot of history, a world championship F1 equivalent GP race was held there back in the day believe it or not Now its used for grass roots events up to State level, one of the fastest average speed circuits in the country, about the same as Phillip Island where the motorcycle GP's are held.

[frank280zx]

Thanks all, after a bit more thought it may well be that the problem is a combination of driver and a very sensitive low speed bump adjustment.

 

After starting the topic I was reading some Penske shock tuning material, the comment there on how a car feels with loose low speed bump was exactly what I experienced last Sunday, that incar I posted above is not current. The car was moving around a lot through the high speed bendy bits, it had grip but felt very loose. What was good was that the car could be driven hard out of corners, a particularly good thing when you have power

 

So the low speed bump will be adjusted up by one click each end and I will try to do more suitable lines. And drive harder

 

On the circuit, Lakeside has a lot of history, a world championship F1 equivalent GP race was held there back in the day believe it or not Now its used for grass roots events up to State level, one of the fastest average speed circuits in the country, about the same as Phillip Island where the motorcycle GP's are held.

Looks cool .. and tricky as hell at that .. i guess im spoiled with so many tracks that have curb stones and 'litter'.. this looks like the ring.. so like a back road at speed

[260DET]

Aaaah the Nurburgring, wouldn't we all like to drive our cars there Given the S130 a run there Frank? Incar vid?

 

Planning on going to Bathurst/Mt Panorama next year, with a 3.9 diff and 7000+RPM 300KPH is possible, in theory

[Whittie]

Aaaah the Nurburgring, wouldn't we all like to drive our cars there Given the S130 a run there Frank? Incar vid?

 

Planning on going to Bathurst/Mt Panorama next year, with a 3.9 diff and 7000+RPM 300KPH is possible, in theory

 

Incar vid of a zed at the Ring? Yes please!

 

Also Rich, I would LOVE to see incar vid of a zed going that fast! I, as you know, did 250 there, but it was CRAZY scary!

 

When is the next event for you to find out about that them there suspension?

[260DET]

Back at Lakeside Sunday week W, the 30th, incar video is working again. Last time it was switching itself off and of course there was some extra good stuff that was missed. Including passing someone through the kink at over 200 clicks, which was a bit silly really, rush of blood

[260DET]

To finish this off, went to the circuit on Sunday and did a PB, running only 12 PSI boost too Car still moves around a bit but the low speed bump adjustment is not fine enough to adjust it any more, besides its good, according to the Penske info I guess its nearer a wet weather setup.

 

Car has great power down out of corners so to get it to turn in I stomp the brakes and turn the wheel decisively at the same time. This forces an agressive corner approach which means later braking, all good.