Fitting 18" wheels on early C2 993

[charlesw]

I am considering fitting 18" twist spoke wheels on my '94 C2. I read in FAQs that some chassis numbers are "can't do it", some " you must fit a steering rack brace" and some "no problem, brace already fitted". As the middle part of my chassis number is ....ZRS.... rather than ....ZSS.... I fear I drop into the first category?! As this post was in 2010 I'm wondering if things have relaxed? I have seen a number of '94 cars with 18" wheels so wonder what may need to be done so I can do this if possible? Thanks.

Charles

 

[IndischRot]

IMHO you're not missing much by staying with 17s. Lighter wheels/tyres = more nimble handling.

 

[charlesw]

Hi Maurice, indeed, nice to hear from you!

I really do like the 18" look although I am aware of the compromises. However, from what you say it looks as if I would have to buy a later car to get it!! My chassis number at ZRS obviously comes before the permitted ranges of ZSS numbers. Have you any idea what the limitation is with the early chassis? Do you know of any way round this?
Thanks
Charles

 

[PORKA]

I fitted 18" Turbo twist wheels to my very early 1994 993 C2 way back in the day, don't have the car anymore or the VIN no, fitted ok and also fitted the rack brace as well which it did not have.
Drove very well, looked better than the 17" alloys and did a considerable mileage both in the UK and Europe in it[]

 

[Mark Elder]

FWIW I had a loan set of 18" turbo twists on my '96 coupe for a couple of weeks while its 17" cups where away for a refurb. Handling noticeably more skittish so I was keen to get the 17s back on. Unfortunately the tyres were also different, so not conclusive.

 

[charlesw]

Thanks for all your replies, guys.

As you know, ideas don't stay still!! I'm now looking at a Bilstein/Eibach B12 Pro Kit set-up to go along with a change of wheels - nothing too extreme. Has anyone made this change? I've taken Maurice's advice and am talking to Colin Belton about the wheel situation. I suspect I will be making a visit up to Warrington to find out exactly what is involved and how much?! Given that a change to 18" may be possible I'm looking at either the turbo twist (hollow spoke if pos) or the MY02 5 spoke from the narrow body 996 and I believe, Boxster - 996.362.136.03 fronts and 996.362.140.03 rears. I've seen these on a number of 993s and they look great. I'm looking to buy used so was wondering where is the best place to advertise - wanted?
Many thanks
Charles

 

[993C2EX]

Hi gents,
Maurice I hear there is nothing you dont know about 993s but this is a crossover question from a 986 so lets see if you can help....

The wheel and part numbers have really got to me today so hopefully you can help.
I have just refurbished in gold the solid spoke wheels on my Boxster 986 which are turbo twist and have 265 35 18 rubber.
They look really good so I want to move them to my 993 and put the 993 wheels on the Boxster.
I thought the wheels were the same but how wrong was I!

The rear 993 wheels foul the suspension on the 986 and it seems from some googling that the off set is different and maybe the wheel width is different also (10" or 9.5").

The 993 alloys are hollow spoke (who knew!?) and running on the same rubber 265 35 16.
I cant read the part code properly on the back of the wheel because of the powder coating but interesting the Boxster wheels also have a 993 part code... 993.362.133....
From what I can tell on research the front wheels are the same on both cars.
The rear wheels may have a different offset due to the Boxster being mid engined and so the mechanics are wider hence the wheel being pushed further out ?

So the basic questions.....
If I put the 993 hollow spoke alloys on the 986 is it just a matter of installing a spacer to push the wheel out and off the suspension ?
If so what is the width of the spacer needed ?
With the 986 solid spoke alloys on the 993 will they just sit out a little further (the seem to have a nicer aspect than the hollows)?

On each car, what will be the effect on handling, etc ? I note that its mention that there may be less grip but actually the tyres are the same width so how would the grip be less ?

Is there a difference with alloy wheel width or is the difference just the offset location ?

986 fronts seem to be 7.5j18ET50
986 rears I cant get a number off

 

[MoC2S]

Blimey, I thought I'd resigned ! And I've never been Boxster Register Sec .. []
I have to give you a prize for the most convoluted question ever expressed on this forum, offsets give most people headaches, and swapping different wheel sets is just asking for trouble, really !

Here's some stuff ..
981 Boxster 18" Fitment
F 7.5 x 18 ET 50
R 9 x 18 ET 52
993 Narrow Body 18" Fitment - Cabriolet must be '96 or later
F 8 x 18 ET 50 or 52
R 10 x 18 ET 65

Fronts are certainly not identical, but probably close enough, but rears NOT. The offset combined with the extra inch of width will mean the inner edge of the 993 rim is 25.5 mm further in than your original Boxster wheel. The difference in rear rim width / offset is just design choice for the suspension relationship to the wheel arch, both 986 and 993 drive comes from the gearbox, the engine is just behind the gearbox instead of in front, doesn't affect drive shaft length or placement of wheels. 993 may have wider rims because of weight distribution and greater moment of inertia.

I wouldn't go near spacers myself with a 25.5mm gap to fill, although Porsche did allow some 25mm to fit 65 offset 18s on wide body cars. I'd be checking available thread carefully if anyone would supply a simple spacer or shim in that size, you'd have to look at something equivalent to System 4/8 from Eibach https://www.eibachshop.co.uk/info-pro-wheel-spacers , which would add unsprung weight but at least be safe.

The you've got the opposite problem putting Boxster wheels on your 993 , so why would you do such a thing ? You'd have to get the boxster wheels on so that the centre line of the wheel was in the same position as the original 993 wheels to make it handle the same. The grip should be pretty close despite a slight difference in sidewall angle, but will change if the track is different to some extent. If you go proper spacers the unsprung mass will increase, meaning bumpy road handling might suffer.

Don't do it !

Cheers, Maurice (Invoice to follow)

© Maurice Piper 2021 All Rights Reserved and No Licence Granted

 

[T911UK]

Don't do it !

Well said that man!

 

[993C2EX]

Maurice,
Seems "they” were right about your knowledge.
of course now you know that wasn’t a serious question and for sure I wasn’t going to do that...... honest.
but what a great answer. All the missing numbers filled in and all the points answered individually.
Well done that man.
But now still the problem. My gold 986 wheels look better than my silver 993 wheels.
The solution it seems is simple, re dress the 993 wheels in gold also and continue the theme across the two black cars.
Thanks again.
The invoice will surely be paid as soon as it arrives in the post, or maybe the terms are 30 days and flexible

 

[MoC2S]

I sourced a second pair of WB 18s, and had the centres/spokes done in body colour (Zenith Blue) .. [8D]

I don't se your body colour, but is gold complementary ? I so, do it ! Pristine Wheels did mine in 200x for £250 or so inc refurb for a couple of kerbs on the set (not me, guv !).

With genuine hollow spokes don't send them just anywhere : if they don't know hollow spokes, you might end up with untraceable balance problems from sand getting inside through the valve aperture, allegedly !

cheers, Maurice

 

[993C2EX]

Hi Maurice,

Its such a faff to load photos here.
Body colour is black on both 993 and 986 and the alloys have been coated in a GT3 pale gold.
Going a bit bling here but I've got matt gold Porsche stripes, cut out number 25 (as its 25 years old on the 19th April) and considering gold plated exhaust tips (sure to upset the purists).
I paid £450 for the four wheels coated at South West alloys but they really struggled with the centre caps as they are plastic and so couldn't bake.
Ive just searched Pristine Wheels and there are several comments about them being permanently closed. Are you aware of this ? What was the location that you took your wheels to ?
Good point re hollow spoke and sand getting into the valve aperture. You are indeed a font of 993 knowledge.

I have good news re the baton challenge this evening so raring to go with that 1st April!

 

[T911UK]

I wouldnt let anyone refurb hollow spokes except Chris at Exel

https://exelwheels.co.uk/