Wheel and tyre choice advice required - please!

[DomS]

Hello all,

I'm looking to replace my 17" OEM wheels with 18" wheels, but I have a few queries regarding wheel/tyre fitments. I have a 2000 model (facelift) 3.0 with Eibach Pro Kit Springs fitted which lower it by 30mm.

The new wheels I have are staggered 8.5" (et38) and 9.5" (et45) with 225/40/18 and 255/35/18 Falken FK452 tyres respectively.

The problem I have is that the tyres (particularly on the rear) have a very "stretched" look, which leaves the edge of the rim looking very exposed and is not a look I like.

I therefore haven't fitted them and was considering a few options...

I was considering:
- Fitting different tyres of the same size, which hopefully won't look as stretched as the Falken FK452s, as I understand the FK452s have a more "tapered" profile suitable for better arch clearance.
- Fitting 285/30/18 rear tyres to fit the 9.5" rims better (and maintain the correct rolling radius) - but that seems very wide and I'm not sure they'll fit the car!
- Keep the current tyres, but change the wheels for 8x18 and 9x18 wheels instead, for a generally better tyre fit.

I'm thinking the latter may be the only real options as I'm not convinced a different brand of tyre will make a huge difference on a 9.5" rim and 285/30 rear tyres seem a bit too drastic!

Has anyone run 285/30/18 tyres on a facelift Z3 (non Z3M)?

Any other suggestions welcome!

(Of course just refurbing the original wheels is an option too, which I may do anyway as my "winter" wheels).

Cheers,
Dom

[Jonttt]

I have just fitted the following Falkens:

Front 8.5x18 wheel & tyre 235x40
Rear 9.5x18 wheel & tyre 275x35

albeit an ///M the difference is the offset and your are pretty spot on for a non ///M wide body and should be able to take the same tyres.

As you say partly depends on the tyre make but also the alloy how much the rim is exposed.

The above are fitted to a Schnitzer Type III Race and protect the rim perfectly.

However my Type II Race in same spec have 225's on the front and 255's on the rear. The 225's are fine on the front but the rears although could take 275's, ideally would take 265's when I change them. (nb not Falken tyres on those but interesting how the type III's definately need a wider rear to sit correctly).

Also my Breytons had 225 front and 255 rear. The front's were probably right but the rears needed 265/275 as well (had dunlops on).

So I would not worry too much about the Falkens profile, its probably as much the alloy style and I would always recomment 225/235 front (225 if you can get away with them) and 265/275 for rears. You should have no issues with those

[DomS]

Thanks for the feedback, it's good to hear a 275/35 works.

When I asked about changing to 265 or 275s, I was told a 35 profile would result in too big a rolling radius, hence the option of 285/30s instead.
By my calculations (not an expert!), these are the rolling radius figures I worked out...
255/35/18 - 317.85mm
265/35/18 - 321.35mm
275/35/18 - 324.85mm
285/30/18 - 314.10mm (which is almost exactly the same as the current 245/40/17s)

The RR for a 275/35 appears to be outside the recommended +/- 2.5% difference

I'd be quite happy for the ride height to be nudged up a tad, but wouldn't want the speedo or anything else to be affected "too much".

Have you noticed any adverse effects (e.g. speedo accuracy or ride height etc)?

BTW, that's a nice ///M you have

Cheers,
Dom

[Jonttt]

Nothing wrong with your logic or the advice you've been given.

I've not noticed a difference but of course there comes a point when you would

[c_w]

This is a tyre calculator that I always use;

http://www.miata.net/garage/tirecalc.html

You can put in the 225/40/18 and the "new" tyre can be the rear tyre to match best. It does look like a 285/30/18 seems to be the closest but that is pretty wide for a 9.5J rim.

[DomS]

Thanks for that c_w.

The forum has been a goldmine of information and many sleepness nights have been spent searching for similar issues and trawling through the replies!

I decided to return those wheels and now have a different set (similar style) which are 8Jx18 front and 9Jx18 rear, both with a 35 offset. They are shod with 225/35/18 and 255/40/18 Falken FK452s respectively.

The rears look great with the extra 10mm offset meaning no spacers required for a nice "snug" fit (and no rubbing).

The fronts however are virtually flush with the bonnet/arch and when descending speed bumps etc. on a test drive, I found the tyres were rubbing on the arch liners.

I've seen that the rear spring seats are available in different thicknesses and wondered if something is similarly available to raise the front by a few mm? In the parts diagram, the front spring perch looks quite different to the rear.

As mentioned, I have Eibach springs (-30mm) fitted with the standard 3.0i shocks which gives a good ride and looks about right, though I'd be happy to raise the car by 10mm F&R.

While not ideal, has anyone cut away the inner plastic arch liner to get around this problem? I see someone else asked this and didn't get a single reply!

Cheers,
Dom

[DomS]

Sorry, I meant my tyre sizes are 225/40/18 front and 255/35/18 rear [/i]