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18 inch wheels - spacers or not?

S

simonf

New member
Hi there,

I have a 2003 2.7 and I am about to change its 17 Boxster S II wheels to 18 inch Sport Design wheels (BBS GT3 style split rims).

Both wheels are original Porsche parts/equipment and these are Boxster wheels, not 911 ones.

The spec for the 18s is:

Fronts 7.5 inch Offset 50 Tyres 225/40
Rears 9 inch Offset 52 Tyres 265/35


Can anyone categorically tell me whether I need spacers for these? Opinion seems to be split depending upon which dealer I talk to...

Many thanks!
 
I can't understand why there should be any confusion - particularly from the dealers!!!

The standard Boxster S wheels are 7J/ET55 and 8.5J/ET50 so comparing to the new sizes reveals a very small change for both front and back so there is no need for spacers of any sort. You'll find the new wheels will stick out a few mm further than the old ones (11mm at the front, 4mm at the rear). In both cases there is marginally less space on the inside of the wheel but should be OK.

You can check out the calculations at http://www.1010tires.com/WheelOffsetCalculator.asp

Regards

Dave
 
Thanks for the reply Dave.

Yes, I agree and do not want spacers if I can avoid them. I had worked out the figures too and the front internal clearance is only 1mm different, so no problem there. The rear internal clearance is reduced by 10mm, so there is more of a difference.

I tried these 18s on the car yesterday and in a straight line they are fine. However, as soon as the car turns left or right there is a rubbing noise from the back wheels. The more the car is loaded the sharper and faster the turn - the louder the noise. If the 17s are put back on, no noise.

After much inspection we thought we could see a very faint mark on the tyres and on the strut but this was very faint indeed and could have been a mark left by the manufacturing process. The tyres are new.

The brake disks are faintly noisey when the car is jacked and the wheels are rotated by hand. Could this by exacerbated by the larger, heavier wheels. Discs are fine, far from worn and don't look corroded and don't feel warped. The car is in A1 condition but only gets light use (26k), which means it could be a bit of rust in the brake system.

My wheel dealer did not think spacers were necessary, another well known porsche parts dealer agrees but my OPC, after hearing the story, is not so sure and is going to call me back on Monday. If I can rule out spacers then it must be a problem with the brakes that shows up under heavier load.

Any ideas?

Excuse any spelling mistakes - typed out painfully slowly on an iPhone...
 
Simon,

I can't believe the problem would be caused by any additional stresses that would become apparent with 18" wheels that wasn't already apparent with the 17" wheels. Agreed, the lesser clearance (actually 8mm) on the rear may be causing some contact, depending on what bit is closest to the rim and/or tyre. I'm no Boxster specialist so I don't know the rear suspension in any detail but it's possible the contact may be between the wheel and another part of the suspension rather than the shock absorber. If it IS a problem you may be able to get away with some 5mm shims - and you probably won't need longer wheel bolts then.

Regards

Dave
 
Yes, agreed re the extra loading, it would be very weird to go from no effect at all with the 17s to a very noisy problem with the 18s. Can anyone with a non-S car confirm that they are using these wheels with or without spacers? There are loads of these wheels about...

Thanks in advance!

Thanks Dave for your help too.
 
After a bit more research it appears that a dirty/corroded handbrake mechanism (within the calipers) and or corroded disks can cause this problem when the car is turning. However, it does seem strange that this only happens with the 18s on. Anyone got any ideas? Seems very quiet on this forum...
 
Can anyone help me with this? Just trying to find out if anyone else has experienced this problem. Or, if anyone else has BBS split rims (9inch width) on a Boxster without having to use spacers.

Thanks
 
I had 18" Turbo II look wheels on my 2004 986 2.7 spec'd from the factory - they were the same offset as the BBS option.

IIRC the only wheels that Porsche allowed their 5mm spacers on were the Carrera 5 spoke wheels (also their lightest wheel), and they came standard on the Anniversary model. From recollection there was also a TSB about fitting 18" wheels and having to tie the brake line to prevent rubbing on the inner edge of the wheel/tyre.
 
Thanks for letting me know Black80XSA - very helpful. Bristol OPC have had my car for a couple of days looking in to another matter but they also looked at the discs and brake mechanism and could find nothing wrong. They also tried some 18s on the car - not the same offset though - and could not reproduce the problem. I'm going back to the fitters tomorrow to try the wheel again - I'll let you know how I get on.

Thanks again.
 
In answer to your original question then you do not need any modification whatsoever, as you are using the wheel set designed for the 986 Boxster (some owners use the wide set form the 996). To quote from the Porsche tech files...

For tyre / rim sizes
225/40 ZR 18 Front 7.5J x 18 ET 50
265/35 ZR 18 Rear 9J x 18 ET 52

Porsche TSB lists as available with and without use of 5mm spacers - if spacers are fitted then the longer bolts from the GT3 must be used (part # 996.361.203.90), and the spacer remains on the hub if using the space saver spare wheel

Only when using 8J x 18 ET50 and 10J x 18 ET47 does the TSB mention fitting clip (part # 999.651.230.02) to tie the parking brake cables back to the arms, and against this wheel size /offset there is no mention of spacers, so presumably they cannot be used (the offset is already pushing the wheel out by 5mm compared to the ET52 anyway).


So you need do nothing bar use your existing wheel bolts and fit the wheels - you have the option to fit the 5mm spacers all round and longer bolts if you want to at a later date.
 
Hello,

I have a MY04 2.7 Boxster and carried out exactly the same wheel swap.

I have noticed a slight scraping sound from the rear N/S when passing a wall on a left hand bend, nothing serious as I put it down to the handbrake mechanism.

The wheels you have are the correct width, offset and tyre choice according to the Porsche Tequipment leaflet as well.

Could it be that you are just being hyper critical with the new setup?

Regards,

Steve.
 
Thanks for all the help everyone. Bristol OPC could find nothing wrong, so when I finally got the wheels fitted again I was delighted to find that the noise, which was very apparent, was now only slightly audible on the driver's side of the car when turning right. So, yes, a mucky handbrake mechanism that must have cleared after a thousand miles of driving.

Steve - EXY27 - I guess you are EXY from Boxa.net? Good to run into you here.
 
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