Wheel Sizing / Offset / Staggered track info.

[pantha]

OK everyone,

I Just want to confirm some info, and make sure I'm not missing anything or what not... As well as have all the info here for anyone else considering this.

On an 2006 A3 8P Quattro Sportback, the standard wheels are:

17" x 7.5" ET56 PCD112 - 225x45 R17 Tyres

The FRONT / REAR Track is: 1531mm / 1515mm (See Below)



This equates to a noticeable 16mm difference (skinnier) at the rear of the car.

If I wanted:

18" x 8" ETxx PCD112 - 225x40 R18 Tyres

I'm planning on staggering the offset to make the wheels the same track front and rear. (See below)



You will note the BLUE underlined dimensions. If you calculate the difference, you 14mm (7mm per side). Referring back to the original track specifications, If I use this setup, I will reduce my track difference down to 2mm. (1mm per side) This is not noticeable. (See Below for Visual diagram)




So, some points/questions:

1. The use of wheel spacers is illegal in Australia. They are NOT an option here.

2. If you're wondering why not just get a ET39/45 setup or a ET38/44 setup to get a perfectly even track from front to rear. I believe the ET's I have selected are easier to get. anyone agree/disagree?

3. Being that the rim width is not staggered, I can maintain the same rolling diameter front to rear with the same tyres used all round. (Haldex SAFE)

4. Will changing the track dimensions affect the Haldex at all? At an educated guess, I assume not, but would like confirmation if I can? (Best to ask and be told, than not to ask and break something)

5. Can anyone confirm this setup will work? (Based on Guard spacing, etc) All I would need is someone who is running ET45's to confirm the front doesn't rub and someone running ET38's to confirm the rear doesn't rub. (With 8" wide rims running 225/40/R18 tyres)

6. I'm Currently running standard springs. Assuming this works now. Would this work at lower ride heights? (Please note the bonus of strut tower clearance in both offsets of 4.7mm and 11.7mm greater above the standard wheel clearance)

7. This setup will give me more options for brake upgrades, due to the increased offset? (The standard A3 has shocking BBK clearance)

8. Would I get greater handling/cornering from both the increased tyre width and greater overall track width setup? (Not considering suspension setups, that's a whole different discussion)

9. I understand this setup removes the ability to rotate wheels around the car to promote even tyre wear. But, in saying that, the Haldex Diff will work safely with a certain % Difference in rolling diameter to compensate for tyre wear. So If you put brand new tyres on the front and leave say, 60% worn tyres on the back. (Or vice-versa) It Shouldn't affect it. Agree/Disagree?

Thanks in advance.

 

[Sayam]

Wow, very well explained!

The front with 225/40/18 8J ET45 will work perfect, I could be wrong but I suspect you'll get rubbing on the rear with ET38. Removing the rear arch screw can help lots.

 

[pantha]

Wow, very well explained!

The front with 225/40/18 8J ET45 will work perfect, I could be wrong but I suspect you'll get rubbing on the rear with ET38. Removing the rear arch screw can help lots.

I figured the front would be ok. Just the rear I'm having trouble finding a definitive answer for.

It seems everywhere I search on the net, people are running 8.5J rims or 235 profile tyres, etc. nothing similar to what I'm trying to find?

 

[Sayam]

Well the factory wheel and tyre spec is 18x7.5J ET54.

The majority of aftermarket wheels in the UK use 18x8J ET45. This helps fill the arch whilst maintaining the factory usability of the car, i.e., no issues with rubbing the arch liner etc.

That probably explains why you may be struggling to find info on the spec you'd like to use.

I guess the obvious answer is to try it and see, and then let us know how you get on so we have the answer on the forum for the next person.

As I say, it is definitely the arch screw the tyre catches on so removing that will be a big help.

You may find more info on a forum dedicated to 'stance'...

 

[pantha]

hmmm... maybe i need to buy some spacers to install on the rear wheels, to "experiment" with changing the offset. (Not have them installed permanently, just to trial fit the wheels)

Then, with simple maths, I can establish max. offsets for any width rim...

question is, considering I don't want to wast money on spacers i "technically" wont be using, should i try to find the cheapest spacers out there? or are cheap spacers an ABSOLUTE NO-NO??

 

[Double J]

If you won't be using them just get ones with longer bolts. FK Automotive make cheap spacers. I assume you're wanting 16mm ones so they track the same. You'd only want bolt on spacers if you were using 20mm+

People shorten axles etc to fit wheels, you could extend yours instead?

P.S. I'm running Audi Speedlines (18 x 7.5) and have them spaced on my 2.0 TDI Quattro. Haldex hasn't complained to my knowledge. I'm just about to get 19x9 all around too, reckon it'll be fine. And at standard height I can't imagine any rubbing.

 

[pantha]

If you won't be using them just get ones with longer bolts. FK Automotive make cheap spacers. I assume you're wanting 16mm ones so they track the same. You'd only want bolt on spacers if you were using 20mm+

To test how far I can go out, (using my current 7.5J Rims) and simulating an 8J rim, I would need spacers up to 24mm. (See blue underlined text in first post) But, If they were too thick ... then I would obviously want thinner ones. Perhaps I buy a "pack" of spacers to "shim" out the wheel to the desired offset?

(Like I said, I will only bolt it all up and if I'm not confident driving it, I can just get a car load of mates to sit in the car, load up the boot and then get more mates to rock the car side to side to see it it will rub?)

People shorten axles etc to fit wheels, you could extend yours instead?

I think I looked into this, I came to the conclusion it was not possible, as lengthening the axles, doesn't shift the brake mounts and hence, you wont be able to do it. Am I wrong??

P.S. I'm running Audi Speedlines (18 x 7.5) and have them spaced on my 2.0 TDI Quattro. Haldex hasn't complained to my knowledge. I'm just about to get 19x9 all around too, reckon it'll be fine. And at standard height I can't imagine any rubbing

Agreed here, I think to ONLY issue with the Haldex is if you run different rolling diameter tyres from front to rear as it confuses the Haldex into thinking you are skidding. The change in rear offset (Or "Track") will do nothing to that parameter. I'm more concerned about any small descrepencies in cornering, as I am changing the turning circle of the wheels. BUT, I doubt such a small difference would affect it?