[Mkii Spit]

I'm looking to replace the wheels on my ph2 gtv v6. I've upgraded the suspension to the Koni Sport shocks with Eibach springs so it does ride a bit lower than stock. Does anyone run a similar setup on 18x8J rims and if so, what would be the best offset to ensure I don't start rubbing body work (current offset is 30.5mm); should I reduce the offset by 6mm to keep the inner rim position in the same place, (outer rim moves outboard by 12mm), keep the same offset (both rims move 6mm) or increase the offset by 6mm to keep the outer rim in the same place (inner rim moves inboard by 12mm).
Ordinarily I would have kept the inner rim in the same place to ensure no clearance issues with suspension components etc, however moving the outer rim outboard seems to be a problem on the rear as a straightedge across the tyre currently just touches the inside of the return lip on the bodywork, so any outboard movement is likely to rub if the suspension compresses by more than 30mm. Would moving the inner rim inboard 12mm create any clearance issues?
Any advice is greatfully received, many thanks,
Gareth.

 

[David C]

Even though the wheel is 0.5" wider than std, a 225/40R18 on an 8" ET30.5 18" rim would be sitting in pretty much the same place as a 225/45R17 on a 7.5" ET30.5 17".

 

[Mkii Spit]

Thanks David, i suppose it's logical when you think about it that the same tread width centred at the same position would sit in the same place. Do you know of any concerns with the rim clashing with anything with it being 6mm further inboard than std particularly on the front with steering lock?

 

[David C]

It will come down to what offset the wheels you like are available in.
You may end up needing spacers anyway, depending what offset you can get.

 

[Mkii Spit]

I'm looking at a set of Team Dynamcs ProRace 1.2 which they'll make in any hole pattern, BCD & offset between 25 & 45mm. One of the few new wheel options that'll fit the old Alfa 5x98 bolt hole pattern. So am really looking for confimation of a known offset that'll work with an 18" rim and the lowered Eibach springs...if, of course, there is one onder:

 

[spudkey]

I have Koni / Eibach setup with zender sienna 18" wheels they have an offset of 28mm and I'm sure they are 8"
I have no issues with clearance on the inner edges of both front and rear tyres and suspension,
The only rubbing I get is at the very top inner shoulder and arch liner of rears over big bumps or dips, I'm am currently in the process of fine tuning rear camber setting and bump stop length to cure rubbing
The fronts have 5mm spacers to clear Brembo calipers

 

[David C]

I'm looking at a set of Team Dynamcs ProRace 1.2 which they'll make in any hole pattern, BCD & offset between 25 & 45mm.

Think I'd be leaning towards the ET25

 

[CGTVs]

Ok...here goes...again, I've posted this numerous times but they're not always easy to find.

I've run 18s with std & Eibach springs.

Firstly lowering does NOT cause clearance problems as it just 'uses' up the first part of the suspension travel, it doesn't alter the later part where the clearance problems occur.

Bump stops are a must, even if the cars sits on them when stationary....they do compress & there's not that much movement anyway.

It would help immensely if people would also state what tyre sizes they're using as it's the tyre width/height that causes the rubbing....as well as the wheel positioning....ET/spacing.

The 'correct' 18" size is 225/40 to keep it as near to a 225/45 17. New tyres have taller tread & this can cause rubbing compared to worn tyres when clearance is minimal. If 225 17s don't rub why should 225 18s....same tyre width, it's all down to the wheel position/ET. If you really want to play it safe stick with the std ET of 30.5.

The 18s I used had an ET 40 BUT spaced 12mm giving an ET of 28 with absolutely no clearance problems. Originally I fitted 16mm spacers, giving ET 24, & the rears rubbed....fronts were fine.

So somewhere between ET 28 & ET 24 is the safe limit, I'd stick to 28.

I also ran the ET 40 rears unspaced, while waiting for the 12mms to arrive, & also had no problems.......so I can't understand how Spukey's are rubbing on the inner edge.....he hasn't stated his tyre size though.

Also tyres aren't exactly the same size when comparing different makes, only small ammounts but when a couple of mm is all it takes to clear or not....I think you get my point.

In the past I used to also calculate the wheel's increased J/width into the differing ET when comparing against std 7.5 J ET 30.5 225/45 17s but this was incorrect as it's the tyre width + ET/spacing that's important. The wheel width is only really critical if still using 17s for inner clearance of the springpan but again ET/spacing can usually overcome this. Larger rim diameters easily clear the springpan as my ET 40s proved.

So to summarise, 225/40 18s ET28 should be fine.

Clive

 

[Mkii Spit]

Thanks Clive, thats exactly the info I was after :thumbup:
@ David & Spud, thanks for your input also, it's all good stuff to know.
I'll update with my experience once i've got them fitted.
Regards,
G.

 

[cgc]

The 'correct' 18" size is 225/40 to keep it as near to a 225/45 17. New tyres have taller tread & this can cause rubbing compared to worn tyres when clearance is minimal. If 225 17s don't rub why should 225 18s....same tyre width, it's all down to the wheel position/ET.

Clive

Hi Clive do you know if 235/40 18 just gives you 5mm more height and width over the 225/40 18? And is this not closer in height to the original 225/45 17 tyre?

 

[Jowey]

Online Wheel and Tyre Fitment Calculator. Offset, Tyre Stretch and Speedo Error | Will They Fit

Play around with tire sizes here. Put the 225/45/17 et30 7.5J specs from original 17s in and play around with 18" tires sizes to get something similar in tread width and sidewall height.

 

[David C]

Hi Clive do you know if 235/40 18 just gives you 5mm more height and width over the 225/40 18? And is this not closer in height to the original 225/45 17 tyre?

225/45R17 is 634mm diameter.
225/40R18 is 637mm diameter.
235/40R18 is 645mm diameter.

So: 225/40R18 is what you want. It is also a widely used size, so a wide choice at good prices.
235/40R18 is a lot more £££ and less choice.

 

[El 4 Romeo]

Could we please insert Clive's comments on wheel spacing in an FAQ sticky, please?