Rim Fitment - 97 Box

[RandallNeighbour]

I would like to upgrade my ROH 17's to a set of 18 inch aftermarket Carrera wheels I've found, but I'm unsure if they'll fit, and if they will, what sort of spacers I'd need.

Here's what I've found and would like to buy:

Size: Front 18x8" / Rear 18x10"

Offset: Front 50mm / Rear 65mm

Weights: Front 24.5lbs / Rear 27lbs

Bolt Pattern: 5x130

I believe the bolt pattern is correct, and these rims are probably similar in weight or even lighter than the 17 inch ROH's that came with my car... I think the ROH's are quite heavy in fact, so this might just make my car a little lighter going with these even though they are 18's.

From the info I have gathered (and PLEASE correct me if I am wrong), the front rims are a 1/2 inch larger and may not require spacers. The rear rims are a full inch larger than what the car can take and I'll need 15mm spacers to allow them to clear the brake lines and calipers.

If anyone can tell me if these rims will a) fit my 1997 Boxster and b)what spacers I'd need for sure on the front or rear or both, I sure would appreciate it.

This kind of information does not seem to be readily avaiable on the web!

[RandallNeighbour]

Does anyone know about required offsets for my 97? I can't wait too long to buy these rims as they are on Ebay.

[Loren]

I don't think that 18" wheels are approved for MY97 Boxsters. Something about the chassis not being stiff enough. Later cars had the added stiffening.

You can find standard wheel offsets in your owners manual - or you can download a later model owners manual here.

[RandallNeighbour]

Loren, should I decide to try it anyway (I know of a couple of MY97 owners who've done it and had no problems long-term) how do I figure out how big my spacers should be? Do I take the offset number of the wheel (65) and subtract the manual's offset requirements (50) and use that difference number (15mm) as what I need for a spacer?

[ar38070]

A 8x18 wheel needs a 50mm offset. A 10x18 wheel needs a 40mm offset. So you need 25mm spacers for the rear. 15mm might be enough but depending on what tire width you use you may have rubbing problems on the inside.

It is unlikely that the 18" wheel/tire combo will weigh less than the 17" wheel tire combo. The wheels might weigh a little less because of the design but the tires will be heavier.

[Highlander]

A 8x18 wheel needs a 50mm offset.  A 10x18 wheel needs a 40mm offset.  So you need 25mm spacers for the rear.  15mm might be enough but depending on what tire width you use you may have rubbing problems on the inside.

Hmmmm. I have 10" wheels on the rear of my '01 with a 47mm offset. No rubbing. Actually, the wheels have a 50mm offset and I'm using a 3mm spacer - I'm pretty sure 1 or 2mm would work, but all I had lying around the garage was a 3mm spacer so that's what I'm using.

RandallNeighbour,

The 50mm offset 8's will fit fine up front with no issues or spacers required. For the rears, you will need to get the offset down to 47mm or less. Spacers effectively reduce the offset, so a 25mm spacer would bring the offset down to 40mm which will fit OK. Any more and you run the risk of rubbing the fender with the outside of the tire.

Graeme

[RandallNeighbour]

Geez, 25 mm spacers seem very large indeed. Do I run the risk of premature bearing wear or screwing up a control arm or bending the bucket having my wheels that far out and away from the hub?

My reason for asking all this is I can get some aftermarket Carrera lights for 800.00 (size and offset info above) or authentic Porsche Carrera lights with the correct offsets for 2500.00. I'll save up and spend more if it will prevent bearing wear or suspension problems down the line.

Any other input with this information posted?

[ar38070]

Large spacers are okay as long as they are made correctly. A wheel with a spacer does not load the suspension any differently than a wheel with the equivalent offset.

I do not like doing it for aesthetic reasons. I prefer that my wheels fit right the first time. Also with wheel spacers you have to remember to use the right size bolts all the time.

[adsach]

RandallNeighbour

The problem with the 18x10 Carrera wheels is that MOST of the time you can get them to fit, but not all of the time. While I can't be sure there is a Boxster with STOCK suspension where they won't work, there have been cars with lowered springs(PSS9,H&R,etc) where fenders had to be pounded and fittings done with different spacers. In a few cases, they could not fit at all.

There seems to be 2-3mm difference between the placement of suspension knuckles on 'identical' cars, so that how to fit wheels is a bit like how much camber you can get in the front. You really have to try it on your actual car to be sure.

As far as fitment goes, I don't think it really matters whether you get the $800 or the $2500 wheels. Neither one is designed for your specific Boxster, so some tweaking of spacers will probably be necessary.

Good luck with your decision.

[RandallNeighbour]

Thanks for all this input.

I contacted the aftermarket Ebay reseller and he said he gets a couple of calls a day for these 18's for boxsters and is headed off to the Las Vegas show to meet with the italian maker and will supply them with some Porsche rims to duplicate.

He said to watch Ebay in about six months and he'd have them for sale as rims that will fit standard boxster suspensions, wheel wells, etc.

[Chris_in_NH]

RN,

i've heard that 18's are not a problem on the 97s unless you track the car.

but if you were to track the car, i'm pretty sure that upgrading to the ROW 030 suspension would solve the problem.

i know people that run 18s and even 19s with no problems.

good luck!

[ar38070]

The suspension is not the issue with the 97s. "Weak" mounting points were the problem supposedly. There were some reports of body cracks.

18x10s should fit on most cars. I have H&R coilovers on my car. Several friends have PSS9s. We all have 18x10s on our cars.

There are wheel clearance issues and tire clearance issues.

The wheel clearance issue is on the inside where the wheel can touch the strut. You fix this with spacers if necessary. This is more a problem with coilovers as the spring perch is much lower than on the stock strut. It is even a bigger problem with the euro PSS9s as they used larger diameter springs than the US spec ones.

The tire clearance issue is usually on the outside up against the wheel well. This is only a problem when people insist on using very wide tires. 265s should never be a problem, 275s are usually okay, 285s maybe, 295+ you probably need to roll the fenders, increase camber, etc.