Cayman - Light front end?
Discussion
Hello experienced Cayman/Boxster owners,
I just picked up a 57 plate Cayman S and so far I love pretty much everything about it. My one issue however is that when cruising at 70 or above (on a private runway obviously) that the front end seems light and twitchy, and wanders around a little bit. The strange thing is that under power it feels planted and gives me loads of confidence to keep pushing, but as soon as I cruise, it goes all bambified. Is that normal and am I worrying too much, or do I have a problem?
Regards,
Andrew
I just picked up a 57 plate Cayman S and so far I love pretty much everything about it. My one issue however is that when cruising at 70 or above (on a private runway obviously) that the front end seems light and twitchy, and wanders around a little bit. The strange thing is that under power it feels planted and gives me loads of confidence to keep pushing, but as soon as I cruise, it goes all bambified. Is that normal and am I worrying too much, or do I have a problem?
Regards,
Andrew
Not normal. +1 for the alignment check.
I always go somewhere that uses a hunter alignment machine. You get some lovely printouts of exact setup and how far in the green you are.
Anyone aligning a car worth there salt should weight down the passenger seat as well, I had my 1 series done by bmw lincoln and they simulated two people in the front seats by putting weights in the foot wells
Can be pricy though.
I always go somewhere that uses a hunter alignment machine. You get some lovely printouts of exact setup and how far in the green you are.
Anyone aligning a car worth there salt should weight down the passenger seat as well, I had my 1 series done by bmw lincoln and they simulated two people in the front seats by putting weights in the foot wells
Can be pricy though.
bcr5784 said:
Trev450 said:
Suggest you have the geo checked by someone who knows Porsches. Sounds like you may have incorrect toe angles on the front.
I'd be more inclined to think rear toe might be the issue - but either way the geometry sounds a likely candidate.Trev450 said:
If the rear toe was out it would make for an unstable backend.
Actually no - I had exactly this problem on my Elise, toe out at the rear makes the car feel very twitchy at speed. Some manufactures engineer the rear suspension to increase toe in at the rear under cornering loads to aid stability at speed. Toe in or toe out at the front generally makes the car understeer because, in effect one wheel is fighting the other and reducing the grip at that end of the car. The only exception I know is when you need to warm the tyres to get them to grip - in the wet for example. In karting for example you use a lot of toe out at the front to get heat into the tyres in the wet. But that won't happen on normal road tyres, it's only something you would do when racing and on tyres that don't work when cold.Edited by bcr5784 on Thursday 19th November 17:50
bcr5784 said:
Trev450 said:
If the rear toe was out it would make for an unstable backend.
Actually no - I had exactly this problem on my Elise, toe out at the rear makes the car feel very twitchy at speed. Some manufactures engineer the rear suspension to increase toe in at the rear under cornering loads to aid stability at speed. Toe in or toe out at the front generally makes the car understeer because, in effect one wheel is fighting the other and reducing the grip at that end of the car. The only exception I know is when you need to warm the tyres to get them to grip - in the wet for example. In karting for example you use a lot of toe out at the front to get heat into the tyres in the wet. But that won't happen on normal road tyres, it's only something you would do when racing and on tyres that don't work when cold.Edited by bcr5784 on Thursday 19th November 17:50
Trev450 said:
I agree toe out at the rear will make the car feel twitchy, but that is due to it trying to steer from the rear and consequently produces oversteer. Excessive toe out at the front will result in the car trying to permantly turn, thus giving a vague feel to the front when driving in a straight line.
Oversteer and twitchiness are (subjectively) the same thing. Agreed about the rear, but excessive (or any dynamic) toe out at the front will produce a vague feel as you say and (normally) understeer not twitchiness. If you think about it the outside front wheel is the most important (effective)in terms of response but with toe out the outside front wheel is actually pointing in the wrong direction (out) as you start to turn so (as you say) the steering is vague until you get some lock on and the outside wheel is developing any slip angle and therefore causing the front to turn in. Hence it creates vagueness rather than the reverse (twitchiness)bcr5784 said:
Trev450 said:
I agree toe out at the rear will make the car feel twitchy, but that is due to it trying to steer from the rear and consequently produces oversteer. Excessive toe out at the front will result in the car trying to permantly turn, thus giving a vague feel to the front when driving in a straight line.
Oversteer and twitchiness are (subjectively) the same thing. Agreed about the rear, but excessive (or any dynamic) toe out at the front will produce a vague feel as you say and (normally) understeer not twitchiness. If you think about it the outside front wheel is the most important (effective)in terms of response but with toe out the outside front wheel is actually pointing in the wrong direction (out) as you start to turn so (as you say) the steering is vague until you get some lock on and the outside wheel is developing any slip angle and therefore causing the front to turn in. Hence it creates vagueness rather than the reverse (twitchiness)"The toe setting on a particular car becomes a tradeoff between the straight-line stability afforded by toe-in and the quick steering response promoted by toe-out. Nobody wants their road car to constantly wander requiring never-ending steering corrections. But racers are willing to sacrifice a bit of stability on the straight-ahead for a sharper turn-in to the corners. So road cars are generally set up with toe-in, while race cars are often set up with toe-out."
Trev450 said:
What you are describing is the characteristics of a car entering a corner. The OP is complaining of straight ahead instability and therefore I refer back to my original statement and quote shamelessly from Racecar Enginering:
"The toe setting on a particular car becomes a tradeoff between the straight-line stability afforded by toe-in and the quick steering response promoted by toe-out. Nobody wants their road car to constantly wander requiring never-ending steering corrections. But racers are willing to sacrifice a bit of stability on the straight-ahead for a sharper turn-in to the corners. So road cars are generally set up with toe-in, while race cars are often set up with toe-out."
Well Milliken and Milliken says that you can should use toe OUT to IMPROVE stability over bumps if you have negative camber on the wheels (as we have)."The toe setting on a particular car becomes a tradeoff between the straight-line stability afforded by toe-in and the quick steering response promoted by toe-out. Nobody wants their road car to constantly wander requiring never-ending steering corrections. But racers are willing to sacrifice a bit of stability on the straight-ahead for a sharper turn-in to the corners. So road cars are generally set up with toe-in, while race cars are often set up with toe-out."
But all that be as it may if the front wheels are toed out significantly and have been for any length of time it will be easy to check - the INSIDE edges of the tyres will be feathered (if you have toe in the outside edges become feathered).
dunster said:
Thank you ladies, I'll get onto it in the morning. Can anyone suggest anywhere near Manchester? Otherwise I'll just Google it. Thank you
Ninemeister and Unit11 in Warrington will be able to sort your geo. Ninemeister have just been right through the suspension on my 997 and Unit11 recently fully rebuilt and modded a friends 944 track car suspension.bcr5784 said:
Trev450 said:
What you are describing is the characteristics of a car entering a corner. The OP is complaining of straight ahead instability and therefore I refer back to my original statement and quote shamelessly from Racecar Enginering:
"The toe setting on a particular car becomes a tradeoff between the straight-line stability afforded by toe-in and the quick steering response promoted by toe-out. Nobody wants their road car to constantly wander requiring never-ending steering corrections. But racers are willing to sacrifice a bit of stability on the straight-ahead for a sharper turn-in to the corners. So road cars are generally set up with toe-in, while race cars are often set up with toe-out."
Well Milliken and Milliken says that you can should use toe OUT to IMPROVE stability over bumps if you have negative camber on the wheels (as we have)."The toe setting on a particular car becomes a tradeoff between the straight-line stability afforded by toe-in and the quick steering response promoted by toe-out. Nobody wants their road car to constantly wander requiring never-ending steering corrections. But racers are willing to sacrifice a bit of stability on the straight-ahead for a sharper turn-in to the corners. So road cars are generally set up with toe-in, while race cars are often set up with toe-out."
But all that be as it may if the front wheels are toed out significantly and have been for any length of time it will be easy to check - the INSIDE edges of the tyres will be feathered (if you have toe in the outside edges become feathered).
Trev450 said:
I don't consider -0.3 degrees (OE setting)of negative camber to be of any consequence which is why anyone looking to improve the handling of these cars increases that by some margin. Furthermore, the OP is not making any reference to the state of the road surface. He also appears to be confident that his 'problem' has now been accurately identified.
He won't know until he has fixed the problem, or at very least established that he is toed out by looking at the state of the tyres. If the front tyres indicate a problem he might save himself the cost of a full geo check. If not it probably suggests a geometry check is a good starting point. But at the end of the day it may be neither of the things we suggest - suspension bushes, dampers, bent links etc may all be the culprits. It may even be a previous track day hero who has put an aggressive front end setting on the car. At the moment there is far too little knowledge to be definitive.Edited by bcr5784 on Friday 20th November 19:33
Edited by bcr5784 on Friday 20th November 19:42
I've booked it in at Ninemeister in Warrington, the guy on the phone filled me with confidence compared to a regular garage I rang just before, just to double check. Seeing as everyone seems interested and opinions are divided, I'll report back with what will no doubt be an incredibly boring and average update next week. Thanks everyone.
dunster said:
I've booked it in at Ninemeister in Warrington, the guy on the phone filled me with confidence compared to a regular garage I rang just before, just to double check. Seeing as everyone seems interested and opinions are divided, I'll report back with what will no doubt be an incredibly boring and average update next week. Thanks everyone.
I'd be very interested to hear the results. Trev quotes one source suggesting the front, Milliken and Milliken (the bible on such things?) suggests the rear. My son (who has been very successful at international level in everything from F3 to GTs) is aware that people use front toe out aiming to promote turn in - but thinks front toe makes little difference and (I read today) that Lotus on the Evora 400 has toe IN to promote turn in. All very contradictory.Edited by bcr5784 on Sunday 22 November 20:26
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