17" wheels on a Cayman

[spiker]

Anyone here had any experience running 17" wheels on the Cayman ( ex boxster ones)

I have 18"'s which I believe are the standard size for my 2007 cayman S

I am interested in knowing if handling , ride are much different

 

[Nick_USA]

I believe you cannot fit 17" rims to an 'S' as there will not clear the callipers. Edit: Just checked I am correct:

 

[John H]

Correct that 17" Cayman wheels will foul the calipers on the Cayman S, but if I remember correctly the issue is one of offset, not diameter, and they will fit if you use spacers. I seem to recall someone using 17's with winter tyres on an S with spacers. In my opinion, the Cayman feels nicer to drive on the 17's with the smaller tyres. There is less grip, but the steering feels sweeter and you can feel the chassis better. Ride is supposedly better, but I reckon the difference is minimal. I have never tried the combination of a Cayman S on 17's, and I would suspect with the extra power it is probably inadvisable, other than perhaps with winter tyres. Only my opinion though.

 

[spiker]

Appreciate the reply - thanks My thoughts were to use them as winter tyres so I am not concerned about a drop in handling performance too much Just had a check on the PCD (pitch circle diameter as I have discovered - the diameter of a circle through the 5 bolts) which is 5x130 with an offset of 52 and the spacers then act as a kind of washer to offset the wheel outwards - almost like a washer on the hub - everyday is a school day - then this should solve the problem of fouling on the calipers There seems to be an unlimited number on eBay , some appear to be produced to fit more than one vehicle which means they have more than 5 holes making them weaker surely ? I suspect the best option is to find spacers with just the 5 holes from a reputable source - is this something Porsche offer ? , I will check tomorrow As I am new to this idea would someone confirm my research is correct and would anyone be able to point me in the right direction of a good manufacturer of them ? Also looking at my wheel diameter using the formula (( 265 width * 40 profile percentage /100 ) (* 2) ( both sidewalls) (/ 25.4 to convert to inches + 18 rim)) this equates to a diameter of 26.35 inches forgive any BODMAS errors there The 17's work out to be 25.86 ( 225/50 r17) so a difference of 0.5 inches in diameter - what effect will this have on the speedometer for example - will this be showing a higher speed than I am actually doing and thus the mileometer will increase at an incorrect ( higher ) rate ? My head hurts I need a beer..................... Beer located.................. More beer required

 

[spiker]

Damn and then there are the front tyres which work out to be 25.4 so a difference of nearly an inch Beer is not working

 

[spiker]

I am thinking of leaving the 18's on

 

[Buddy]

You're right the smaller diameter will make the wheels turn faster for a given speed/distance so will indicate you are travelling faster and rack up the miles quicker. Stick with 18"wheels for winter tyres. Incidentally I found several sets on Ebay.de before christmas wheels and winter tyres not so expensive as here, but how to get them back etc for a reasonable cost. The beer may help in the short term.[]

 

[spiker]

The more beer I drink the more this sounds like a bad idea

 

[John H]

The diameter of the wheel is not the point, it is the diameter of the tyre/wheel combination, and in this case the 17, 18 and 19 packages all work out the same, so no issue.

 

[John H]

The man who knows the answer to the 17" wheels/spacer/Cayman S thing is Allan Whittaker who is on this forum under the name of Tess Tickle

 

[Alan_Armstrong]

HI Spiker, Just my tuppence, but any difference in speedo readings will relate to the change in circumfrence of the tyre, not the diameter. Another thought, but may not be applicable, is that some caymans have pasm which lowers the ride height by 10mm (I think) Would be interested to know if you progress...

 

[spiker]

Yes thanks Alan I now understand that Yet a 265/40 18 will have a different circumference than a 225/50 17 and thus would impact the speedo/mileometer I can see though that certain combinations may work out to be the same circumference but not in my example Please correct me if I am wrong

 

[spiker]

Good point about Pasm though , however it doesn't apply in this case I found pasm an unsuitable ride compromise for my needs and thus chose a car without it

 

[Buddy]

Normally to keep the difference in diameter and hence circumference within a reasonable amount for the wheel/tyre options from an 18" to a 19" wheel the aspect ratio relative to tyre width is changed. The tyres you asked about : 265/40/18 will have a rolling radius of 13.173" ( 26.346" dia ) a 225/50/17 is 12.929" ( 25.858" dia ) a difference of .244" on radius almost 1/2" diameter A 235/50/17 gives a close match to the original correct rolling radius at 26.25" within the wear range of the standard tyre/wheel combination. Considering the cost of spacers from an OPC, probably not much different to buying a secondhand set of 18" wheels and some winter tyres.[8|]

 

[Nick_USA]

Just remember if you are contemplating 5-6mm spacers that you also need the longer wheel bolts for these.

 

[spiker]

This is just too much inconvenience for a cheap set of 17's

ORIGINAL: Buddy Considering the cost of spacers from an OPC, probably not much different to buying a secondhand set of 18" wheels and some winter tyres.[8|]

Agreed - thanks

 

[Richard_Hamilton]

I bought a winter wheel and tyre package from Design911 on 18" wheels. The choice of 19" winter tyres is pretty limited, to say the least. I calculated the rear tyre diameter to be quite a bit smaller than the 19" rears, whereas the fronts were about the same. I queried it before buying them, and was assured the PSM/PASM wouldn't be a problem. They were correct. For calculating diameters and offsets, etc, there are some good calculators on www.1010tires.com.