What is the reasoning behind stiff suspension for track?
Discussion
I've been reading about suspension lately and I catch more than one time, people talking about changing suspension because it's too soft i.e. KW to JRZ, but what's the point of having a hard suspension set on track or on the street? Given that in this subforum there isn't a lot of cup talk if any.
One wants to reduce body motion such as roll under hard cornering, dive under braking and squat under acceleration on track to increase how responsive the car is to inputs from the steering, brakes and accelerator.
Plus with a soft set up and Cup's on that risks bottoming out in bends which will then loose you grip/traction.
Porsche Suspension can gain positive camber under roll , this is very bad and why you see the outside edge of tyres melted at track days, you can kill tyres in 3 laps on a bad set up car.
excessive roll can also cause rear steer, again not ideal.
And last you will feel like you are in a boat which is never a nice feeling.
Plus with a soft set up and Cup's on that risks bottoming out in bends which will then loose you grip/traction.
Porsche Suspension can gain positive camber under roll , this is very bad and why you see the outside edge of tyres melted at track days, you can kill tyres in 3 laps on a bad set up car.
excessive roll can also cause rear steer, again not ideal.
And last you will feel like you are in a boat which is never a nice feeling.
And "stiffer" how; springs, shock rates, roll bars etc. etc.? It's a black art, but the very basic answer, as cmoose says, is that higher loadings - braking, cornering, acceleration - will need more resistance (stiffness) from the suspension system, in order to control body movement and roll. Which is not to say all movement and roll is a bad thing, necessarily.
From my motorcycle racing days stiffer suspension tended to absorb less of the "information" felt by the contact patch and transmitted to me through the pegs, bars and seat.
It's also faster (usually) at getting the thing settled again after a moment -- slide/bump/weave.
However, you need a certain amount of compliance so the whole rig doesn't keep jumping off the road all the time.
It's also faster (usually) at getting the thing settled again after a moment -- slide/bump/weave.
However, you need a certain amount of compliance so the whole rig doesn't keep jumping off the road all the time.
luigisayshello said:
I've been reading about suspension lately and I catch more than one time, people talking about changing suspension because it's too soft i.e. KW to JRZ, but what's the point of having a hard suspension set on track or on the street? Given that in this subforum there isn't a lot of cup talk if any.
Favourite topic of mine this. I ran a rally team, and won several European and world championships...found that its all too easy to become absorbed in suspension setup...!The principal purpose of the spring is to support the weight of the car, but the key to setup is damping. In damping, you can have up to 4 ways of control - High speed and low speed adjustment for both bump and rebound. You tune these, together with spring rates and anti roll bar stiffnesses, until you find the best compromise between speed and feedback.
You don't necessarily want the car to be really stiff, otherwise it'll bounce around, and you wont have tyre contact all the time.
I've driven some cars that have had springs that are way too hard, and damping which is way too stiff, and the car is practically undriveable..!
Lets not get out of control though, a track/race car will have spring rate prob double a road car.
I don't think many people have been in circuit race cars to really know how stiff race cars are.
So any road car on a track day is a compromise, vs what people are trying to do to road cars, and race cars hate roads.
All this GT3 is a race car for the road rubbish spouted on here is daft most of the time.
I don't think many people have been in circuit race cars to really know how stiff race cars are.
So any road car on a track day is a compromise, vs what people are trying to do to road cars, and race cars hate roads.
All this GT3 is a race car for the road rubbish spouted on here is daft most of the time.
IREvans said:
Favourite topic of mine this. I ran a rally team, and won several European and world championships...found that its all too easy to become absorbed in suspension setup...!
From the dabbling I've done - on mountain bikes and also a long while back with the Nitrons on my sprint/hillclimb TVR Griffith - I found that once you find settings that work, varying them by much (sometime even at all) does not necessarily give adjustment, but screws things up. In other works, 'adjustable' shocks are only theoretically adjustable an , in reality, there's a sweet spot for a lot of the settings.Did you find there work some parameters not worth faffing with, once you'd got them dialed?
I love adjustment in shocks, you can have a track set up, a road set up, a wet set up etc etc.
I have done sprint's and was the fastest guy on the day in the dry, then it rained, I did a few clicks on the bump/rebound at the back and was the fastest in the wet in the after noon as once it rained the car just over steered too much, a few clicks dialed the car back in.
adjusting rebound is a great way to just do a few clicks to take that jar out of the car if you have set it up for track and want to drive home, then once home you can dial in your full road set up.
I so miss adjustment in Porsche cars, and think the GT cars are very lacking in this dept to be able to dial in balance, even the Porsche GT4 race cars which are based on road cars had to ditch the PASM crap and fit KW's.
Now all the track guys are fitting springs and DSC PASM controllers to try and make it any good, why spend £2k on a failed system when you can buy some real adjustment and better damping !
I have done sprint's and was the fastest guy on the day in the dry, then it rained, I did a few clicks on the bump/rebound at the back and was the fastest in the wet in the after noon as once it rained the car just over steered too much, a few clicks dialed the car back in.
adjusting rebound is a great way to just do a few clicks to take that jar out of the car if you have set it up for track and want to drive home, then once home you can dial in your full road set up.
I so miss adjustment in Porsche cars, and think the GT cars are very lacking in this dept to be able to dial in balance, even the Porsche GT4 race cars which are based on road cars had to ditch the PASM crap and fit KW's.
Now all the track guys are fitting springs and DSC PASM controllers to try and make it any good, why spend £2k on a failed system when you can buy some real adjustment and better damping !
Edited by Porsche911R on Friday 3rd March 09:53
Porsche911R said:
Lets not get out of control though, a track/race car will have spring rate prob double a road car.
I don't think many people have been in circuit race cars to really know how stiff race cars are.
So any road car on a track day is a compromise, vs what people are trying to do to road cars, and race cars hate roads.
All this GT3 is a race car for the road rubbish spouted on here is daft most of the time.
I'm sorry but you are very wide of the mark I don't think many people have been in circuit race cars to really know how stiff race cars are.
So any road car on a track day is a compromise, vs what people are trying to do to road cars, and race cars hate roads.
All this GT3 is a race car for the road rubbish spouted on here is daft most of the time.
Changing the dampers on a car is the easy bit. The engine, drivetrain, brakes, chassis design, stiffness, and everything else that makes a car track worthy. You cant have a car that has a spring damper set up that is perfect for both road and track, but the rest of a GT3 is essentially a Cup car with trim.
Porsche911R said:
I love adjustment in shocks, you can have a track set up, a road set up, a wet set up etc etc.
I have done sprint's and was the fastest guy on the day in the dry, then it rained, I did a few clicks on the bump/rebound at the back and was the fastest in the wet in the after noon as once it rained the car just over steered too much, a few clicks dialed the car back in.
adjusting rebound is a great way to just do a few clicks to take that jar out of the car if you have set it up for track and want to drive home, then once home you can dial in your full road set up.
I so miss adjustment in Porsche cars, and think the GT cars are very lacking in this dept to be able to dial in balance, even the Porsche GT4 race cars which are based on road cars had to ditch the PASM crap and fit KW's.
Now all the track guys are fitting springs and DSC PASM controllers to try and make it any good, why spend £2k on a failed system when you can buy some real adjustment and better damping !
I agree that it would be fantastic for some drivers if Porsche would fit decent adjustable shockers. The problem that they face is that it is likely that most drivers will not require any adjustment to thier damping and most of those that do wont have the expertise to set up thier dampers properly which mat lead to the cars handling becoming deminished by bad set up - which could backfire on porsche no matter how good thier intentions. I have done sprint's and was the fastest guy on the day in the dry, then it rained, I did a few clicks on the bump/rebound at the back and was the fastest in the wet in the after noon as once it rained the car just over steered too much, a few clicks dialed the car back in.
adjusting rebound is a great way to just do a few clicks to take that jar out of the car if you have set it up for track and want to drive home, then once home you can dial in your full road set up.
I so miss adjustment in Porsche cars, and think the GT cars are very lacking in this dept to be able to dial in balance, even the Porsche GT4 race cars which are based on road cars had to ditch the PASM crap and fit KW's.
Now all the track guys are fitting springs and DSC PASM controllers to try and make it any good, why spend £2k on a failed system when you can buy some real adjustment and better damping !
Edited by Porsche911R on Friday 3rd March 09:53
Steve Rance said:
I'm sorry but you are very wide of the mark
Changing the dampers on a car is the easy bit. The engine, drivetrain, brakes, chassis design, stiffness, and everything else that makes a car track worthy. You cant have a car that has a spring damper set up that is perfect for both road and track, but the rest of a GT3 is essentially a Cup car with trim.
not really, I have driven a older CUP car and it's night and day not a nice thing to drive really.Changing the dampers on a car is the easy bit. The engine, drivetrain, brakes, chassis design, stiffness, and everything else that makes a car track worthy. You cant have a car that has a spring damper set up that is perfect for both road and track, but the rest of a GT3 is essentially a Cup car with trim.
Harsh, VERY noisy, also no road car has a full welded in cage, which gives greater stiffness, MonoBalls, slicks, diff rates etc etc.
brakes also night and day due to cooling, Pads and how much lighter a CUP car is.
just trim :-p
Next people will be saying a RSR is like a 991 RS and the 991 RS is a race car for the road !
And a 911 CUP car would be hell on any road., So just trim, it is not. !
driving a road going 996 GT3 is nothing like the same thing, but people love the "race car for the road comments" because it sounds good !
I see. So the 996 cup had a different engine and gearbox to the Gt3? Did it have different suspension pick up points, geometry or different brakes? Different body panels?
I've spent a lot of time racing 996 Cups. I still hold several lap records in them. I'm pretty tuned into these cars. If you throw on a set of cup srings and dampers and take the trim out they would feel the same to drive and last just as long before they fell apart.
We were second over all for nearly half of the 2007 Silverstone 24 hour race in a 996 cup with an engine taken from a standard 996 GT3. Came 7th over all in the end. Name me another un touched road car engine that could run at that pace?
Anyway. Back to the OP's question. A decent set of double adjustable dampers would have a definate beneficial effect on a car that was intended for both road and track use
I've spent a lot of time racing 996 Cups. I still hold several lap records in them. I'm pretty tuned into these cars. If you throw on a set of cup srings and dampers and take the trim out they would feel the same to drive and last just as long before they fell apart.
We were second over all for nearly half of the 2007 Silverstone 24 hour race in a 996 cup with an engine taken from a standard 996 GT3. Came 7th over all in the end. Name me another un touched road car engine that could run at that pace?
Anyway. Back to the OP's question. A decent set of double adjustable dampers would have a definate beneficial effect on a car that was intended for both road and track use
Porsche911R said:
Driving a road going 996 GT3 is nothing like the same thing, but people love the "race car for the road comments" because it sounds good !
Ahhh, so that's why YOU bought one. A shame you couldn't get your head 'round how to drive it, so gave up and sold it. Thanks for enlightening us ! !
Lots of good replies already, but in addition - something else to think about is that there is a simple reason for stiffer springs for track use - but that then creates extremely complicated variables.
For readers thinking of using their road based car for track use they need to understand a quite simple and practical reality - that one of the main reasons for stiffer suspension stems from the benefits of lowering the car.
This is because the amount of roll from low speed to high speed corners cannot be managed by any one spring rate if the centre of gravity is too high. Lowering the car reduces the centrifugal (or more correctly centripetal) forces acting on the centre of gravity height to roll the car as much at different speeds - it reduces the range of spring stiffness to cover the speeds you are likely to encounter.
However when you lower the car there is a downside because there is no more room above the tyre for it to move to - and so you also reduce the range or distance that the suspension can move through from new lower level to the suspension maxing out before the tyre would hit the wheel arch.
Designing a race car could avoid this problem as you could remove that physical restriction - but starting with a road car - limits are designed in for road use that limit the range of track options available.
The G forces you can use on track for cornering. braking and accelerating will be greater than on most public roads and if you reduce the distance you are managing the movement over (to get the benefit of lowering the car) you need a stiffer spring (as spring rate affects force and distance governed). Too soft and the suspension would simply bottom out (not recommended).
If you are using a shorter but stiffer spring - you then need variable rate or compound springs to keep the spring in contact with the damper when it is fully extended on the inside in a corner and doesn't just become lose.
The resulting stiffness of compound or variable rate springs do not calculate as simply as many would like to think (very complicated).
But stiffer springs need stiffer damping as well and then the anti-roll bar strength has a different effect on the overall stiffness of the car and probably needs adjusting as well.
This simple reality becomes really complicated with any one change influencing several other parameters and for most owners fitting a full kit that has already been tested and reported by other users to work well will be a better way forward than trying to sort it all out yourself.
When we went production racing a few years ago it took us a huge amount of time, research and testing to get our car to be capable of running round a fast corner with two wheels off the ground - in the wet and I wouldn't recommend repeating that development - which is far more complicated for a road car than a race car (especially if it is running on slicks).
By the way we don't offer such suspension kits so we have no ulterior motive in expressing this view other than we think it is the best way forward for most owners.
Baz
For readers thinking of using their road based car for track use they need to understand a quite simple and practical reality - that one of the main reasons for stiffer suspension stems from the benefits of lowering the car.
This is because the amount of roll from low speed to high speed corners cannot be managed by any one spring rate if the centre of gravity is too high. Lowering the car reduces the centrifugal (or more correctly centripetal) forces acting on the centre of gravity height to roll the car as much at different speeds - it reduces the range of spring stiffness to cover the speeds you are likely to encounter.
However when you lower the car there is a downside because there is no more room above the tyre for it to move to - and so you also reduce the range or distance that the suspension can move through from new lower level to the suspension maxing out before the tyre would hit the wheel arch.
Designing a race car could avoid this problem as you could remove that physical restriction - but starting with a road car - limits are designed in for road use that limit the range of track options available.
The G forces you can use on track for cornering. braking and accelerating will be greater than on most public roads and if you reduce the distance you are managing the movement over (to get the benefit of lowering the car) you need a stiffer spring (as spring rate affects force and distance governed). Too soft and the suspension would simply bottom out (not recommended).
If you are using a shorter but stiffer spring - you then need variable rate or compound springs to keep the spring in contact with the damper when it is fully extended on the inside in a corner and doesn't just become lose.
The resulting stiffness of compound or variable rate springs do not calculate as simply as many would like to think (very complicated).
But stiffer springs need stiffer damping as well and then the anti-roll bar strength has a different effect on the overall stiffness of the car and probably needs adjusting as well.
This simple reality becomes really complicated with any one change influencing several other parameters and for most owners fitting a full kit that has already been tested and reported by other users to work well will be a better way forward than trying to sort it all out yourself.
When we went production racing a few years ago it took us a huge amount of time, research and testing to get our car to be capable of running round a fast corner with two wheels off the ground - in the wet and I wouldn't recommend repeating that development - which is far more complicated for a road car than a race car (especially if it is running on slicks).
By the way we don't offer such suspension kits so we have no ulterior motive in expressing this view other than we think it is the best way forward for most owners.
Baz
Steve Rance said:
You cant have a car that has a spring damper set up that is perfect for both road and track
How close could one get with something like a dual spring setup with the softer one with enough travel to soak out most of the road bumps but have the higher rate one take over for track use to reduce the amount of roll/weight transfer? Am assuming modern dampers have enough range to be able to work over 2 very different spring rates obviously but I was told that something like ohlins ttx have an electronic controller now that can be fitted in cabin to switch the car to different damper settings so you could go from full soft on the road to sport then track with more damping dialled in.What is really interesting if your a nerdy engineer is that calculating an ideal spring rate based on frequency and load for a car without downforce will give a number around 50% to 100% more than road car springs, BUT this still results in numbers way lower than people run on race cars which will be double again or more. Never been to happy why that it is other than dynamic effects and overcoming all the compromises inherent in modifying road based tin tops for racing.
Digga said:
From the dabbling I've done - on mountain bikes and also a long while back with the Nitrons on my sprint/hillclimb TVR Griffith - I found that once you find settings that work, varying them by much (sometime even at all) does not necessarily give adjustment, but screws things up. In other works, 'adjustable' shocks are only theoretically adjustable an , in reality, there's a sweet spot for a lot of the settings.
Did you find there work some parameters not worth faffing with, once you'd got them dialed?
Digga, you're right, its easy to make adjustments and screw things up. We had a saying that its easy to "get lost in the setup" that is, to adjust so far away from the base setup that the car becomes undriveable, and then you cant get it back..!Did you find there work some parameters not worth faffing with, once you'd got them dialed?
Lets say we were testing for a dry high grip, yet bumpy rally like Corsica. We would typically have a 2 or 3 day test, doing around 500km. We'd start the test with our base setup with settings for ride height/spring rate/ARB thickness/toe/camber/caster etc. We'd also start on our damper clicks for high speed bump, low speed bump, and rebound. These would have 32 clicks for each parameter, and we'd normally start roughly in the middle of the range.
If the driver would describe a particular aspect he wanted to change, lets say more stability on the back on big braking into a sharp corner, we'd try 2 clicks softer on rear rebound, then do a few runs and see if it got better, and that it didn't introduce another problem elsewhere. The key is only to change a few things at a time...You can see why it takes so long..!
Gassing Station | 911/Carrera GT | Top of Page | What's New | My Stuff