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Wheels, Offset, Spacing etc. - Help please? Really not my strong point...

Discussion in 'A3/S3 Forum (8L Chassis)' started by AJD S3, Jun 19, 2012.

  1. AJD S3
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    AJD S3 2nd Gear

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    [Jun 19, 2012]
    As some of you may have already seen from other posts I've put on here previously, I'm seriously considering getting hold of some new wheels for my S3 next month.

    I've got my heart set on some 9.5J Rota Grid Drifts in Steel Grey, specs below that I've been reccomended to get by Rota themselves:
    - 18" x 9.5J
    - ET 23
    - 225/40 tyres

    They've said to compare the offset of these to my current wheels, to work out what size spacers I may (or may not) need, and to work out how I should fit the wheels in general.

    Forgive me for seeming being really stupid, but all this wheel stuff really isn't my strong point, I have absolutely no idea how to do this.

    I currently run Audi RSTTs in 18", which are obviously the wheels that I need to compare against. I currently run these with 10mm spacers on the front, and 16mm on the rear, but the wheels still nowhere near fill the arches - another thing I really do want to achieve! I've already had the front arches rolled in advance to cover this.

    All in all, the questions I really need answering are...
    - Will the Rotas even fit at all in the above size?
    - What size spacers will I ideally need to be running to fill out the arches properly? (If the wheels will even fit)

    I understand if no one can help with this, but I just can't seem to get my head around wheels and setting them up.

    Thanks!
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  3. patTTpoa
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    patTTpoa Member

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    [Jun 19, 2012]
    That spec will fit fine on the rear but you will need min 5mm spacer on the front as it will rub the shock/coilover.

    Pat
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  4. AJD S3
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    AJD S3 2nd Gear

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    [Jun 19, 2012]
    Hi Pat,

    Thanks for this. Do you run these wheels then? Looks like you do from your signature, or at least similar ones?

    It's good to hear they fit, although to completely fill the arches to the very edge, what sort of spacing will be needed on the front and rear do you think? I can adjust camber as I already run adjustable tie bars, and arches aren't a problem - already had these rolled.
    Ideally I'm looking for this sort of thing in terms of spacing:
    [​IMG]
    [​IMG]
    #3
  5. sideways steve
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    sideways steve Member

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    [Jun 19, 2012]
    Whats the offset and width of the stock 17" rims on the S3 ? If anyone can tell me this I can work out the correct offset/spacer combo for you.
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  6. sideways steve
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    sideways steve Member

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    [Jun 19, 2012]
    Right found it myself.

    The stock S3 Avus Wheels are 7.5" Wide on an ET32 Offset. Thats your base point regardless of what wheels you want to run.

    If you fit 9.5" Wide wheels with an ET23 offset the following will happen:

    1) The inside edge of the rim will be 16mm closer to your strut.
    2) The outside edge of the rim will be 34mm further out toward the wheel arch.

    To determine the correct offset required to achieve the look you are after someone needs to measure how far out the arch is from the edge of the standard wheels. I cannot do it as I am at work and dont have my car with me.

    As an example if you then fitted a 10mm spacer to the above wheel setup, you would move the outside edge of the wheel 44 mm closer to the arch and it would only be 6mm closer to your strut (compared to the standard setup) this would effectively change your offset to ET13
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  7. sideways steve
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    sideways steve Member

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    [Jun 19, 2012]
    To take it one step further I used your current setup as a baseline (18" RSTT's with 16mm Spacer on rear)

    If you fitted the Rota's with NO SPACER they would stick out 13mm further than your current setup but you would have 25mm less clearance toward your strut. I think you would therefore get contact between the wheel and strut but you would need to measure it to be sure.

    If you measure from the outside edge of your RSTT's to the wheel arch you will know how much further in MM you need the wheel to "stick out" and you would use the appropriate spacer or tey to get the wheels with a better offset.
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  8. AJD S3
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    AJD S3 2nd Gear

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    [Jun 19, 2012]
    The way you broke all that down is unbelievably helpful - I think I actually now understand wheel offsets! Thank you!

    I'd go outside right now and measure the distance I need to know right now, but unfortunately I don't have the standard Avus alloys, and my RSTTs run spacers, so my findings wouldn't be at all accurate.

    Can anyone else help with this?
    #7
  9. AJD S3
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    AJD S3 2nd Gear

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    [Jun 19, 2012]
    Thanks Sideways Steve,

    So your calculations here are for the back? I run 16mm spacers on the back, but only 10mm spacers on the front. I would have thought, considering the space in the rear wheel wells, contact with the suspension components would not be an issue - I was only expecting this to be an issue at the front of the car?
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  10. Jpd89
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    Jpd89 Member

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    [Jun 19, 2012]
    Sorry for the hijack but was hoping someone could help me too! Could i make a set of alloys with this fitment go onto a 8l S3? [h=1]7 x 17" 5 stud 114.3 pcd et45[/h]
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  11. sideways steve
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    sideways steve Member

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    [Jun 19, 2012]
    Give me the distance you need the wheel to move outward for the front and back by measuring with your current setup and Ill tell you the right offset/spacer combo you will need for front and back :)
    #10
  12. jojo
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    jojo S3 Drift King! Staff Member Moderator

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    [Jun 19, 2012]
    I just want to say 9.5" wide up front is stupidly wide! If that's what you are after, then who am I going to argue? You need closer to ET20 for the front wheels to clear the strut, maybe even ET15(or ET18 if you stick 5mm spacers on ET23) from my experience.
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  13. jojo
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    jojo S3 Drift King! Staff Member Moderator

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    [Jun 19, 2012]
    This is ET25 on 19x8.5" with 235/35 tyres, the rear is ET20.

    [​IMG]
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  14. AJD S3
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    AJD S3 2nd Gear

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    [Jun 19, 2012]
    Right I've just been outside on my lunchbreak with a ruler, yes, a ruler, measuring things. So from what you've already mentioned, here are the calculations I came to:
    Front - Rotas will extend 19mm beyond current setup
    Rear - Rotas will extend 13mm beyong current setup

    I used my ruler (gets funnier every time I say it) and added the above to the edge of my current wheels. Both front and back moved out to pretty much meet the arch, however, I think I'm going to need to add another 5 - 10mm to this, as I'll be running fairly stretched style tyres on the new wheels - I want to push the tyre edge to meet the arch lip, as opposed to the edge of the wheel itself.

    It does very much look like the only way I'm going to get this spot on is by experiementing with the wheels once I have them!
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  15. AJD S3
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    AJD S3 2nd Gear

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    [Jun 19, 2012]
    Furthermore Steve, I saw you posted in the below thread as well, similar to what we're talking about here:
    http://www.audi-sport.net/vb/a3-s3-forum-8l-chassis/160922-rota-gtrs-s3.html

    The Imola Yellow example at the top of the thread, is EXACTLY the setup I'm looking for. Thing is, the specs listed for that car seem frankly stupid? This is, supposedly, what it's running:

    Rota grids
    18x9,5
    ET 38
    17mm spacers in the front
    30mm spacers in the rear

    Surely that can't be right? Unless in those details, the value of the width of the spacers is actually the complete widening of the track width? Both sides added together to make a total? In other words - 15mm per side on the rear, and approx. 10mm per side on the front?

    If this is correct, then we end up with the spacer setup that I have now? Which would be highly convenient? :think:

    Very much doubt this is the case...
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  16. sideways steve
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    sideways steve Member

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    [Jun 19, 2012]
    On the yellow one I frankly cannot understand why he went for ET38 offset wheels when an ET23 was available which would allow a far smaller spacer to be used.

    In an ideal world you want NO spacers so obviously that being the case if you can run with a small spacer thats better than having a big bolt on beast !

    Essentially the if you take the fact hes using spacers into account his offsets are actually as follows:

    Front - ET21
    Rear - ET8

    if thats the same look you want to go with I would be tempted to see if Rota do the wheel in an ET20 I know they do with a 114 PCD (as I had them on my Evo) but if not then go with the ET23 you mentioned in the first post.

    With the ET23 Try running with no spacer on the front and you wont be far off the yellow car (2mm) and on the rear I would go with a 15mm Spacer you may get away with your 16mm ones but that extra 1mm may cause you clearance issues with your arches. If running no spacer on the front causes contact issues with your strut then you can preferably go with a 3mm spacer or at the most a 5mm.

    What people forget though is your tyre choice will also have a massive impact on your offset, some tyres sidewalls are chunkier than others and dont take a stretch quite so wellso if that was the case you would need to add or remove a bit of offset accordingly.

    For example, I ran Falken 235/45 18's on my Rota GTR Drift 9.5" ET20's with no rubbing but if I swapped the tyres for Toyo R888's they would have rubbed like hell on the arch as the sidewall was much "squarer" when compared to the Falkens.
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  17. AJD S3
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    AJD S3 2nd Gear

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    [Jun 19, 2012]
    Right, thanks to the efforts of Sideways Steve, I finally think I understand this whole offset lark! YAY!

    I've done some calculations and come up with the below, based on the original/standard S3 Avus alloys (7.5" wide with an offset of ET32) being as close as you can go to the front suspension strut safely:

    AVUS ALLOYS:
    Size - 7.5"/190mm
    Centre Line - 95mm
    ET Offset - 32mm
    Total distance between inside wheel edge and mounting - 95mm + 32mm = 127mm (so in other words, this is the maximum - we're aiming to match or get below this value with the new wheels)

    ROTA GRID DRIFTS:
    Size - 9.5"/241mm
    Centre Line - 120.5mm
    ET Offset - 23mm
    Total distance between inside wheel edge and mounting -120.5mm + 23mm = 143.5mm

    So what I can take from this is that, without spacers, the Rota Grids on the front will exceed the original acceptable distance inwards towards the strut by 16.5mm (143.5mm - 127mm = 16.5mm). Which tells me, that in order to conform with how the car was originally setup, and clear the front struts, I will need at least 16.5mm spacers on the front wheels to make up the difference (obviously rounding this value up to 17mm or even 18mm). This distance though, as mentioned earlier, is based entirely upon the idea of the Avus Alloys being as close as you can possibly go towards the strut - this is probably not the case at all, and I expect there is far more room to play with?

    Not sure if this is good or bad news really, but all I know is the only way to really work all this out properly in terms of reaching the arch lip with the tyre, is going to be through trial and error once I get the wheels. Oh well, at least I'm learning! :yahoo:
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  18. sideways steve
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    sideways steve Member

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    [Jun 20, 2012]
    Based on what other people are running I think its safe to say that although your theory above is correct, the bit thats wrong is the assumption that the stock Avus alloys are as close to the strut as possible. This is not the case.

    If you run a 18mm spacer on the Rotas with ET23 they will stick out wayyyyy to far.

    As mentioned in my previous post, the yellow car is effectively running an offset on the front of ET21 when you take the spacers into account.

    if you fitted an 18mm spacer you would end up down at ET5 which would be far to low.

    I rekon you will be able to run the desired rotas with a 3mm spacer on the front and a 15mm on the rear and you should have no issues.
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  19. Alex C
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    Alex C Well-Known Member

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    [Jun 20, 2012]
    with ET23, you would need 5 mm spacer to match Donjons old S3 setup... 20 - (38-23) = 5
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  20. superkarl
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    superkarl MAN OF STEEL

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    [Jun 20, 2012]
    i post this in every wheel/offset thread, helps to get an idea of fitment and wether or not they will or will not fit. especially if you know your inner clearance and outer clearance to the arch

    Wheel Offset Calculator
    #19
  21. AJD S3
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    AJD S3 2nd Gear

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    [Jun 22, 2012]
    Thanks Steve, I did think this was probably the case regarding the Avus alloys and their clearance from the strut. So you reckon 3mm on the front (I'd round up to 5mm) and 15mm on the rear?

    What about the below with donjon's old setup? 5mm all round? Is so much wider on the back a necessity for clearance do we think, or just styling wise?

    Alex C - thanks for the info on donjon's setup.
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