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Cayman Tires & WheelsDiscussion of Tires, Wheels, Suspension, etc.
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I changed my standard 18" Wheels for 19" Sport Design wheels with 235/35/19 Front and 285/35/19 Rear(with 5mm spacers) and drove happily away...........
Came to a junction and braked and all hell broke loose - Warning, after Warning after Warning.......
I had checked clearances, everything ok........ Turn off ignition, faults/warning messages cleared. Drive again......... If I braked slowly/gently no problem, but if I had to press even a little hard these warnings came on:
Drove 20 miles like this, stopping and cancelling these warnings by turning off the ignition......... Then a Dog darted out in front of me - Emergency Stop - all ok............ And then since then (120 miles) I have had no warnings at all.
Does the system have to learn the new tyre/wheel configuration?
I called Porsche GB technical service and they said that when you change wheel/tyre sizes they would re-programme the System (takes 5 minutes - come in anytime!)
What experiences do you have?
PSM - Porsche Stability Management
While it can’t overcome the laws of physics, the revolutionary Porsche Stability Management (PSM) system does lend an added degree of balance and control to the Cayman’s mid-engine driving dynamics, inspiring surefooted confidence in corners and extreme situations.
A standard feature on the Cayman and Cayman S, PSM continuously monitors steering input, road speed, yaw velocity and lateral acceleration to calculate the actual direction of travel. If the car begins to steer off line, PSM instantly intervenes with precision brake inputs on individual wheels to help bring the car back onto the driver’s intended path.
If braking alone isn’t enough to correct the vehicle’s cornering line, PSM then calls on the Cayman’s engine management system, adjusting engine output as needed to help stabilize handling. PSM can also compensate in an instant for mid-corner changes in load resulting from deceleration or braking. When Sport mode is selected with the optional Sport Chrono Package, PSM’s threshold for intervention is raised, allowing for greater driver involvement. If you prefer driving without automatic PSM assistance, the system can be set to standby at any time. In this case, it will only intervene under heavy braking, where both front wheels exceed the ABS threshold.
For all of its technical ability, PSM goes virtually unnoticed in everyday driving situations, preserving the Cayman’s natural agility.
I have never heard of any such reprogramming for changing tire/wheel sizes, although it is recommended that you keep the rolling diameters within 5% of stock to avoid potential PSM conflicts. This sounds like you have some sort of other intermittent failure or problem with the brakes, etc.
PSM - Porsche Stability Management
While it can’t overcome the laws of physics, the revolutionary Porsche Stability Management (PSM) system does lend an added degree of balance and control to the Cayman’s mid-engine driving dynamics, inspiring surefooted confidence in corners and extreme situations.
A standard feature on the Cayman and Cayman S, PSM continuously monitors steering input, road speed, yaw velocity and lateral acceleration to calculate the actual direction of travel. If the car begins to steer off line, PSM instantly intervenes with precision brake inputs on individual wheels to help bring the car back onto the driver’s intended path.
If braking alone isn’t enough to correct the vehicle’s cornering line, PSM then calls on the Cayman’s engine management system, adjusting engine output as needed to help stabilize handling. PSM can also compensate in an instant for mid-corner changes in load resulting from deceleration or braking. When Sport mode is selected with the optional Sport Chrono Package, PSM’s threshold for intervention is raised, allowing for greater driver involvement. If you prefer driving without automatic PSM assistance, the system can be set to standby at any time. In this case, it will only intervene under heavy braking, where both front wheels exceed the ABS threshold.
For all of its technical ability, PSM goes virtually unnoticed in everyday driving situations, preserving the Cayman’s natural agility.
The only reprogramming needed for a wheel/tire change that I'm aware of is for the TPMS which you can do yourself with the OBC. But it would not cause the issues described.
TPMS
TPMS - The Tire Pressure Monitoring System provides early warning of any drop in pressure by continuously monitoring the pressure in each tire and alerting you in the onboard computer display in the event of a pressure deficiency. It communicates the exact pressure of each tire and/or their deviation from ideal pressure. This does away with the need for regular air pressure checks at the service station, which often prove highly inconvenient.
I have never heard of any such reprogramming for changing tire/wheel sizes, although it is recommended that you keep the rolling diameters within 5% of stock to avoid potential PSM conflicts. This sounds like you have some sort of other intermittent failure or problem with the brakes, etc.
It also can play hell with your ABS - it depends on which tires you put on there. - all tires of those sizes are not the same - you need to look up the measurements of their overall diameters and compare then to the overall diameters of the stock tires you took off - I've heard and read that the variance should be no more than 4% to be safe. My guess is that you exceeded this somehow - probably with the 285's in the rear.
I did my sums before changing the wheels using the Miata tyre size calculator pointed to elsewhere on this forum so the wheel sizes are extremely close to standard. All calculations are based on circumference.
Front = 1/4% (0.25%) Variance from Standard
Rear = 2% Variance from Standard
Original Standard Front/Rear Variance = 6.14%
New Front/Rear Variance = 5.5%
I was shocked and astounded that these error messages came up, however the Technical support guys at Porsche GB Centre in Reading said that they knew of the occurrance, and it was an easy five minute 'fix' with the Programmer and they invited me in to sort it out there and then.
Whilst driving over to them, I had to do my 'emergency stop' activating the ABS, and from then on no more error messages! I felt such a fool, that when I arrived, I did not go in, but telephoned them and said it had resolved itself so would not be needing their assistance.
I had this happen once (thank goodness it didn't happen twice more to me too -- the urine stains can be tough to get out of the leather seats) driving home after a DE in which I left my 225/40 18 fronts on, but replaced my 285/30 18 rear track tires (which i'd worn down to the belts) with my street 265/35 19's. I thought it was due to having 19' wheels in back and 18" in front, even though it was within tolerences for the abs/psm.
Besides recoding the tpms each time I swap wheels, there's a recalibrate command for the pcm (nav screen --> set) that corrects for tire circumference being tracked along with the gps signal to track vehical movement, but doubt this impacts abs/psm.
Greg
PSM - Porsche Stability Management
While it can’t overcome the laws of physics, the revolutionary Porsche Stability Management (PSM) system does lend an added degree of balance and control to the Cayman’s mid-engine driving dynamics, inspiring surefooted confidence in corners and extreme situations.
A standard feature on the Cayman and Cayman S, PSM continuously monitors steering input, road speed, yaw velocity and lateral acceleration to calculate the actual direction of travel. If the car begins to steer off line, PSM instantly intervenes with precision brake inputs on individual wheels to help bring the car back onto the driver’s intended path.
If braking alone isn’t enough to correct the vehicle’s cornering line, PSM then calls on the Cayman’s engine management system, adjusting engine output as needed to help stabilize handling. PSM can also compensate in an instant for mid-corner changes in load resulting from deceleration or braking. When Sport mode is selected with the optional Sport Chrono Package, PSM’s threshold for intervention is raised, allowing for greater driver involvement. If you prefer driving without automatic PSM assistance, the system can be set to standby at any time. In this case, it will only intervene under heavy braking, where both front wheels exceed the ABS threshold.
For all of its technical ability, PSM goes virtually unnoticed in everyday driving situations, preserving the Cayman’s natural agility.
TPMS
TPMS - The Tire Pressure Monitoring System provides early warning of any drop in pressure by continuously monitoring the pressure in each tire and alerting you in the onboard computer display in the event of a pressure deficiency. It communicates the exact pressure of each tire and/or their deviation from ideal pressure. This does away with the need for regular air pressure checks at the service station, which often prove highly inconvenient.
Linear Mode
