SuperUser

I have read every offset thread and I think am all set. That being said, I do not want to roll my fenders so here are my specs up for review.

Front 18 x 8.0 +56

Back 18 x 9.5 +49
or
Back 18 x 10 +43

Thanks for any input

pantera43

Daryl, imho I think your close but a tad off with the exception possibly of the 10's. If it were me I might consider the following:

18x8 ET 52mm using a 225 tire possibly a 235
18x9.5 ET 47mm using a 255 possibly a 265

The ET's you mention might bring the wheel a little too far out. Is your car lowered with stiffer springs. The wheel vendor should know exactly what you need for what tire size you plan on running. I would validate with them before laying down your hard earned dollars. There are a lot of variables to consider. Who do you plan on ordering the wheels from?

Dan

SuperUser

I am getting the wheels from Work, unfortunately they only come in set sizes. I used http://www.1010tires.com/WheelOffsetCalculator.asp to try and come up with a setup that would work.

It was my under standing that a lower offset # for a given width would push the wheels out more.

I am not sure what suspension I will put on. I have used KW in the past and loved them but am unclear if I can get down around RS height with them.

sml

I have copied & pasted my comments from another recent post of mine ....

how much risk do you want to take with your 'maximum'?
are you happy to roll the fender?
stock springs or track springs?
are you happy to flatten the oil pipe or do you have already have the later version already flattened?
what camber do you run?
what type of tyres as they have slightly different dimensions?
are you legally allowed to use spacers in your country?
are you legally allowed to use adapters in your country?
and do you really want the perfect max fitment that requires you to do some work, or is something 'pretty safe' and quick preferred?

as an example of the difficulties ... there are a few threads where people are running 10ET44 265/35 and it is fine, but then another guy mentions that he runs 10ET43 265/35 with lowering & about -2 negative camber and that example hits on the inside etc etc.

and maybe read this after I went through the same question ...
http://forums.rennlist.com/rennforum...el-offset.html

or if you just want the 'close enough' quick answer with no fuss then go to tirerack and you'll see 9ET43 and 8ET50. i've measured this up on the rear and you'll be left with about approx 10mm either side on the rear rim which is a LOT compared to when you start trying to squeeze in a 10" rear wheel.

sml

I think you mean the opposite ... 8ET56 and 9.5ET49 .. is a little too far in NOT out.

Do you want to you use a small spacer on the front?

pantera43

Forgive me for the confusion, I'm bad. Your correct, the lower the ET will bring the wheel out. The ET's you mentioned might be a tad too much inboard and you may get some inside rubbing.

Dan

SuperUser

sml,

It was your post that got me nervous about doing the 10 inch rear.

I went with Bill Vurberg's info as my starting point: "Cup1(aka Design92) in 17 were both ET55 for 7 & 9"
So a 9.5 ET49 would have the same inside clearance and be +12mm on the outside.

I am happy to run a 3mm spacer on the front if needed.

Thanks again.

Henrik964

Hijacking a bit Anyone on 17 and 9" ET 45 in the back? Would that work?

sml

Diameter of the rim makes pretty much no difference.

What is your current rear wheel width & offset on your car?

Henrik964

I run 18" at the moment but i'm after "track wheels" 17" they I ran std 8" and et 52 in the back on my supposed track wheels...

Bill Verburg

You have to understand that when width changes the ET needs to change as well

964 RS and Cup used
8ET52 front and 9.5ET68 w/ a 21mm spacer 9.5 ET68 w/ 21mm spacer is net ET 47

various people have used slight variations on the above like 8ET50 front, widest I've seen in back is 10ET65 w/ a spacer to bring net ET down to ~ 44 -47

sml

The calcs are easier to understand if you have a benchmark width & offset.

The best benchmark would be what is currently on your car however we dont know this info unfortunately.

But if you want a quick simple answer, a lot of people seem to suggest 9.5ET47 as per the Cup car spec is good.

9.5ET49 is 2mm further inwards .. not much so should be ok but worst case you could use a small spacer.

Using the benchmark of the Cup wheels currently installed on my car of 8ET52 against the 9.5ET49 ..
Inner clearance of WHEEL - 16mm less
Outside clearance of WHEEL - 22mm more
So the centre of the tyre moves 6mm outwards

Remember that a change to WHEEL clearance is NOT the same as the change to the TYRE clearance.

With my 8ET52, my clearances with my current ride height and camber, I have the following clearances ...
Oil Pipe Clearance to Tyre = 20mm
Oil Pipe Clearance to Rim = 31mm
Suspension Arm Clearance to Tyre = 25mm
Suspension Arm Clearance to Rim = 36mm
Tyre Clearance to Fender = 35mm

Put that together and you can understand what is really going to happen ... in that comparison all you are really doing is giving the tire some more stretch with the tire shifting 6mm outwards.

So take some measurements of your clearances if you really want to understand
.. but the quick answer is the 9.5ET49 would be fine (and worst case use a small spacer but probably not needed).
.. personally I would go with the 10ET43 (but the worst case of a $50 fender adjustment or small spacer doesn't worry me).

sml

Wheel diameter is pretty much irrelevant so there is no need to include.

8ET53 benchmark compared to 9ET45
Inner clearance of WHEEL is 5mm less
Outer clearance of WHEEL is 21mm extends
Centre of TYRE shifts 16mm outwards

Go out to your car with a tape measure, lay on the ground and see if you like the result.

Just remember that whilst the WHEEL clearance might extend, you may just be stretching the tyre, so the WHEEL clearance change is not the same as the TYRE clearance change. So also keep in mind the 'centre of tyre shift' of 16mm outwards. ie the wheel edge is moving 5mm closer to the body of the car but you are actually shifting the tyre 16mm outwards, so you would actually end up improving the clearance on the inside.

Henrik964

sml I just edited my post, it is 8 ET 52 of course, but I start to get it. You are a true asset here

sml

.. ... definately not an asset .. i just spent about 1 month studying the topic on the forums here and with conflicting outcomes & different opinions, it felt like I was guessing on $3k worth or rims. It wasn't until someone suggested that offset calculator, combined with going outside to study my car, that I gained some confidence.

It does get tricky as often you might just be stretching the tyre and hence clearances may not even change with wider rims!