LOOK HERE for information on wheel sizes and offsets

SDHA4SLine · Jul 2, 2015

In a similar fashion to another thread I made earlier but for a different subject matter...

Seems that a lot of members have questions about wheel sizes and offsets so thought I'd post a thread to collate all other threads covering these subjects that I can find.

I'll keep adding to it as I find them

Please correct me if I’m wrong with my understanding below as I don’t mislead someone but this is how I understand things...

Offset basics
The offset is described by the term ET, which is from the German word 'Einpresstiefe' translated as 'insertion depth'
The smaller the offset number is the further outboard the wheel will be. For example: an 18-8.5J ET45 wheel would sit further into the wheel arch than an 18-8.5J ET35 wheel would. In effect your wheel base would be 20mm wider (10mm a side) with the ET35’s when compared with the ET45 of the same wheel diameter & width

ESD1711 · Jul 3, 2015

Worth noting that the 'J' often quoted in wheel sizes actually has nothing to do with the size whatsoever. The 'J' is to do with the tyre bead profile.

Anyways, i'll try and have a bash at 'negative offsets' for you

Offsets all stem from an imaginary centre point marked half way through the width of the wheel from front to back. The offset of your wheel is defined by where the mounting face of your wheel sits in relation to this centre line.

So, if you were to have an 8' wide wheel, your imaginary centre line would pass through the wheel with 4' either side of it. This would be known as ET0. Therefore for an ET0 wheel, you have as much of the wheel (4' in this case) in front of the mounting face as you do behind it.

The difference between positive and negative offsets depend on which direction you move the mounting face of the wheel from this centre line. Moving the face towards the outside edge of the wheel will result in a positive offset. Obviously, the further you move this towards the outer edge of the wheel, the higher the offset and the further your wheel will sit inside the wheel arch.

In the case of a negative offset wheel, you're moving the mounting face of the wheel in the opposite direction, ie away from the ET0 centre line towards the INSIDE of the wheel. Hence the further you move from the centre line towards the inside edge, the lower your offset will be and the further out from the wheel arch your wheel will poke.

Some examples with numbers using an 8' wide wheel and based on the assumption that there are 25mm in an inch.

8' wide wheel, ET0:
Here, the mounting face will sit slap bang in the middle of the wheel and you'll have 4' of wheel in front (outside) the face and 4' of wheel behind the mounting face.

8' wide wheel, ET25
Here, the mounting face will sit 25mm towards the outside edge of the wheel and you'll have 3' of wheel in front (outside) the face and 5' of wheel behind the mounting face.

8' wide wheel, ET-25
Here, the mounting face will sit 25mm towards the inside edge of the wheel and you'll have 5' of wheel in front (outside) the face and 3' of wheel behind the mounting face.

Hope that helps

SDHA4SLine · Jul 3, 2015

ESD1711 said:
Worth noting that the 'J' often quoted in wheel sizes actually has nothing to do with the size whatsoever. The 'J' is to do with the tyre bead profile.

Anyways, i'll try and have a bash at 'negative offsets' for you

Offsets all stem from an imaginary centre point marked half way through the width of the wheel from front to back. The offset of your wheel is defined by where the mounting face of your wheel sits in relation to this centre line.

So, if you were to have an 8' wide wheel, your imaginary centre line would pass through the wheel with 4' either side of it. This would be known as ET0. Therefore for an ET0 wheel, you have as much of the wheel (4' in this case) in front of the mounting face as you do behind it.

The difference between positive and negative offsets depend on which direction you move the mounting face of the wheel from this centre line. Moving the face towards the outside edge of the wheel will result in a positive offset. Obviously, the further you move this towards the outer edge of the wheel, the higher the offset and the further your wheel will sit inside the wheel arch.

In the case of a negative offset wheel, you're moving the mounting face of the wheel in the opposite direction, ie away from the ET0 centre line towards the INSIDE of the wheel. Hence the further you move from the centre line towards the inside edge, the lower your offset will be and the further out from the wheel arch your wheel will poke.

Some examples with numbers using an 8' wide wheel and based on the assumption that there are 25mm in an inch.

8' wide wheel, ET0:
Here, the mounting face will sit slap bang in the middle of the wheel and you'll have 4' of wheel in front (outside) the face and 4' of wheel behind the mounting face.

8' wide wheel, ET25
Here, the mounting face will sit 25mm towards the outside edge of the wheel and you'll have 3' of wheel in front (outside) the face and 5' of wheel behind the mounting face.

8' wide wheel, ET-25
Here, the mounting face will sit 25mm towards the inside edge of the wheel and you'll have 5' of wheel in front (outside) the face and 3' of wheel behind the mounting face.

Hope that helps

Thanks, thing that I need to understand is... will an ET-25 be further inboard or outboard than an ET-50, in other words as the minus ET number gets bigger which direction is the wheel going in? inbound or outbound

ESD1711 · Jul 3, 2015

SDHA4SLine said:
Thanks, thing that I need to understand is... will an ET-25 be further inboard or outboard than an ET-50, in other words as the minus ET number gets bigger which direction is the wheel going in? inbound or outbound

Again, the actual number represents the deviation from the centre line if you like. The plus or minus just dictates the direction the mounting face is moving in relative to the overall width of the wheel.

So, ET-50 would move the mounting face of the wheel 25mm closer to the inside edge of the wheel than ET-25..... using the examples in my post above you'd have the following:

ET-25 would have 5' of wheel outside of the mounting face and 3' of wheel behind it.
ET-50 would have 6' of wheel outside of the mounting face and only 2' behind it.

Strictly speaking the absolute maximums you could have for an 8' wide wheel, I.e with the mounting face either directly on the inside or outside edge of the wheel (we're in to the realms of make believe here btw) would be either ET-100 or ET100.

So ET-100 would have the mounting face on the inside edge, counting down the numbers towards zero moves the mounting face closer to the centre line.

Then you reach the centre line at ET0 and start counting the numbers up the way as the mounting face moves out towards the outer edge of the wheel till you'd get all the way to ET100.

This is how you get concave wheels. A high positive offset wheel is likely to be a very flat faced wheel, wheres a low / negative number gives you more of a concave look as its pulling the mounting face towards the inside edge of the wheel.

Worth noting that, generally speaking, negative offset wheels are fairly uncommon.

Of course you can then chuck spacers in to the equation as a means of reducing the offset of the wheel which further complicates things

SDHA4SLine · Jul 3, 2015

OK got it, what I was trying to get my head around was the smaller a positive ET number gets the further outbound the external wheel face goes. But the negative ET numbers work the opposite way around, the larger the negative ET number is the further outbound the external wheel face goes.

ESD1711 · Jul 3, 2015

It all sounds a bit daunting at first - but when you get your head around the basics its actually fairly straight forward

Adding in spacers essentially just reduces the offset by moving the mounting face of the wheel closer to the inside edge of the wheel.

So for example, if we took a wheel with ET15, and added a 10mm spacer to it - that would bring the fitment down to ET5.

Taking the same ET15 wheel and adding a 20mm spacer to it would take the mounting face of the wheel beyond the imaginary centre line, leaving you with an offset of ET-5.

PHILIP HUGHES · Feb 1, 2017

Hi,

I'm new to this forum and would like to ask if i wanted to fit genuine audi alloys 19" (all round) to my b7 (2005) s line v6 2.5d saloon what would be the best fitments ET, J, etc; for maximum comfort and road handling. I only ask as I have quite big wheel arches and the wheels I have on (which were on when I bought it) have fake alloys which have cracked, and would prefer original audi alloys. Many thanks

Charlie Farley · Feb 1, 2017

the ET (offset) wont have any effect on ride quality as such, nor will the J size (rim width) , the ride quality will be controlled by the damper/springs and the tyre size / profile.
A 19" 35 profile will be a lot firmer ride than lets say a 40 or 45 profile, the side wall profile eg 35 or 40 or 45 etc will vary depending on the width of the tyre as the sidewall profile is a % of the tyre width.
tyres with a profile less than 40 will have a much more rigid sidewall and wont be such a forgiving tyre on bumpy roads but a lot of guys use them all the same, just down to personal choice.
As you have an S-Line variant the suspension is pretty firm to start with so keep that in mind , a 40 profile will still be firm but a 35 or less will be a lot firmer overall.
Many audi's come from the factory with 18" x 8j rims 235/40 18 is a popular size tyre on them , they are a firm ride with s-line suspension so doing a 19" with a lower profile will be a bit firmer still.
with audi oem rims the a 35 profile is widely used on 19" rims.
The offset can vary widely with audi rims depending on what fitment they are from, A4's are normally in a group of offsets from in the et40 band, but you can fit other audi rims with offsets in the ET30 band for example, but the lower the ET number the further the rim will protrude into the wheel arch so don't go mad .
hope that helps a bit , it's a very extensive subject offsets/rims /widths and tyres etc for A4 to be honest and things don't allways workout the way you would expect.

Charlie Farley · Feb 1, 2017

You mentioned you have big wheel arches, all A4 B7's inc the S4's share the same bodywork so the arches will be the same , only the RS4 uses different panels as they have a wider track and use a more flared wheel arch.
If your 19" rims look small or the wheel arch gap looks to big then you need to change your suspension ride height , by either lowering springs or going coilovers etc, or new spring /dampers , this would give you option to adjust the ride quality aswell, but that's another job alltogether.
If I went to 19" with 35 profile tyres then my car below would still look and the wheel arch gap would still be the same as I lowered the suspension.
I run 235/40 x 18 tyres so if I went 19" with a 35 the overall diameter of the rim will be pretty the same.

PHILIP HUGHES · Feb 1, 2017

Just Rob. said:
the ET (offset) wont have any effect on ride quality as such, nor will the J size (rim width) , the ride quality will be controlled by the damper/springs and the tyre size / profile.
A 19" 35 profile will be a lot firmer ride than lets say a 40 or 45 profile, the side wall profile eg 35 or 40 or 45 etc will vary depending on the width of the tyre as the sidewall profile is a % of the tyre width.
tyres with a profile less than 40 will have a much more rigid sidewall and wont be such a forgiving tyre on bumpy roads but a lot of guys use them all the same, just down to personal choice.
As you have an S-Line variant the suspension is pretty firm to start with so keep that in mind , a 40 profile will still be firm but a 35 or less will be a lot firmer overall.
Many audi's come from the factory with 18" x 8j rims 235/40 18 is a popular size tyre on them , they are a firm ride with s-line suspension so doing a 19" with a lower profile will be a bit firmer still.
with audi oem rims the a 35 profile is widely used on 19" rims.
The offset can vary widely with audi rims depending on what fitment they are from, A4's are normally in a group of offsets from in the et40 band, but you can fit other audi rims with offsets in the ET30 band for example, but the lower the ET number the further the rim will protrude into the wheel arch so don't go mad .
hope that helps a bit , it's a very extensive subject offsets/rims /widths and tyres etc for A4 to be honest and things don't allways workout the way you would expect.

Hi Just Rob, first of many thanks for responding to my enquiry. As you can probably tell I am very limited in my knowledge on this subject. If I was to ask you n layman's terms which wheel and profile tyre combination to go for what would you recommend (sorry the question mark on my keyboard isn't working) which would you recommend. It's just that when I bought the car originally it looked like it had been modified regarding some kind of sports pack , exhaust etc, so I'm thinking it could have been lowered (not sure). So to clarify, if I stayed with the 19" I wouldn't want the rims to protrude from the arch.

Charlie Farley · Feb 1, 2017

can you upload a pic or two , also you'll need to know what your current rims offset is , you can then work from that point, if your happy with the current rims position in the wheel arch then that will make the choosing an oem rim much easier, either if you are staying 19" or going 18" , keep in mind that 18" would have been one of the factory oem rim sizes fitted to your car.

Gazwould · Feb 1, 2017

Wheels can be calculated but tyres are a different kettle of fish !

The manufacturers don't keep to the width and profile sizes as on sidewall .

Charlie Farley · Feb 1, 2017

Gazwould said:
Wheels can be calculated but tyres are a different kettle of fish !

The manufacturers don't keep to the width and profile sizes as on sidewall .

View attachment 116403

exactly.

Charlie Farley · Feb 1, 2017

PHILIP HUGHES said:
Hi Just Rob, first of many thanks for responding to my enquiry. As you can probably tell I am very limited in my knowledge on this subject. If I was to ask you n layman's terms which wheel and profile tyre combination to go for what would you recommend (sorry the question mark on my keyboard isn't working) which would you recommend. It's just that when I bought the car originally it looked like it had been modified regarding some kind of sports pack , exhaust etc, so I'm thinking it could have been lowered (not sure). So to clarify, if I stayed with the 19" I wouldn't want the rims to protrude from the arch.

your A4 with the s-line option would have been fitted with either 7.5j x 17" alloys with an offset of either et43 or et45 , more likely though to have been fitted with the 8j x 18" alloys which also had an ET43 or Et45 offset, 19" wasn't an option but that does not mean they wont fit , as they will but with 35 profile tyres and is a very popular upgrade but many find the harsher ride when using s-line suspension not to there liking .

Charlie Farley · Feb 1, 2017

these were the oem rims that were for A4 B7 fitment 2005 in the 18x8j format , there are also the same style rims in different offsets and width/diameters that will fit your A4 but they will be from other models and variants.

A4 B7 2005/2006 18"x8j

PHILIP HUGHES · Feb 1, 2017

Many thanks for all the advice as I'm totally new to all this I am just panicking about getting any more rims and tyres but getting the wrong ones. So if I just kept the same diameter of rim I take it I'd be better off with a 40 tyre thickness as opposed to 35 e.g instead of 235/35R19 I would be better off with 235/40/R19 hopefully.

PHILIP HUGHES · Feb 1, 2017

Thanks you ever so much guys for all your advice. Just one last question if I sourced rims and tyres from another audi model what style rim with a 19" would any of you guys recommend as I really need to get cracking on changing the old alloys. Sorry I don't want to sound desperate but really I am. And if it is a different model of audi to get the 19" what style of alloy and fitment would you suggest.

tony mc · Feb 1, 2017

buy my 19" rotors and tyres off me lol

Charlie Farley · Feb 1, 2017

rotors are very nice in 19" but you need to stick with a 35 profile on a 19" , is your a 2wd or Quattro Philip.

PHILIP HUGHES · Feb 2, 2017

Hi Rob,

It's me again from yesterday. I looked all over for 19" x 8.5j x et35 but can't find that variant on ebay or various sites. is there any other et's that would work e.g in the et40s range of still using the 19 diameter rim with the 8j or 8.5j By the way as far as I know it is a front wheel drive. Sorry for being a bit numb scull. For the last time many thanks.

PHILIP HUGHES · Feb 2, 2017

tony mc said:
buy my 19" rotors and tyres off me lol

tony mc · Feb 2, 2017

the dogs not for sale though

Charlie Farley · Feb 2, 2017

what about the pallets aswell tony, must be an all inclusive deal for the lot as the dogs not included...haha

carlcall · Feb 2, 2017

PHILIP HUGHES said:
I looked all over for 19" x 8.5j x et35 but can't find that variant on ebay or various sites.

It appears that a lot of sellers are out of stock of the 19's as they are asking £2k for a set of reps which usually just means that have none.....saves closing the listing and doing a new one.

There are a couple of sellers though....also depends on colour and finish.

http://www.ebay.co.uk/itm/4X-BRAND-...801360?hash=item3ad7b0f3d0:g:AR0AAOSw8gVX87df

http://www.ebay.co.uk/itm/19-BRAND-...635999?hash=item3d05ff819f:g:U4oAAOSwDwtUpnM3

tony mc · Feb 2, 2017

ones like mine are solid to get hold of, i had to wait ages till i found some and that was 2 years ago

Rob them pallets are gonna be a make shift fence when i returf my garden, keep the Tasmanian devil of a dog off the grass for a while so they not in the deal sorry

PHILIP HUGHES · Feb 2, 2017

Thanks guys for your feedback. I thinks because of the problem with cracks in my replicas I would have been more interested in genuine rotors. Having said that I don't mind what make of audi alloys as long as genuine. I quite like the look of RS6s, but wouldn't know what spec to go for. Maybe I would be better with 18s, I was just trying to keep the same wheel spec I have on them now. If I had the choice I would stay with 19s but only if originals, that would be suitable for an s line 2005 :blush:

PHILIP HUGHES · Feb 2, 2017

tony mc said:
View attachment 116462
the dogs not for sale though

Fantastic wheels Tony

tony mc · Feb 2, 2017

yours if you want them mate, they going up for sale asap, just sorting the info on them out then the ad will be up

PHILIP HUGHES · Feb 2, 2017

You'll have to post me a link when you're ready Tony. Second mortgage time, Mrs will kill me....ha ha Lol

carlcall · Feb 2, 2017

Tell her they were only £50......I do this so I'm dreading it if I die as there will be plenty of bargains to be had lol

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Charlie Farley · Feb 2, 2017

nothing wrong with reps, you just need to make sure you buy decent quality ones, some are total mingers but not all of them.
OEM audi rims will allways command premium prices, that's the nature of the product but its doesn't mean you have to go OEM to get a nice set of alloys.

I have been through a few sets recently and sold my original Ronal "DTM" rims a while back , my current Rials are german made and have the same quality build and safety stamps etc as the audi's probably a bit better to be honest and certainly lighter in comparison, which we all know is a bonus .
have a look at "wheelbase " they have more alloys than an alloy factory.....

PHILIP HUGHES · Feb 2, 2017

carlcall said:
Tell her they were only £50......I do this so I'm dreading it if I die as there will be plenty of bargains to be had lol

Sent from my iPad using Tapatalk

Lovely thought... That reminds of the joke " fantasy and reality"...In my fantasy I've got these fantastic audi rotors, but in reality all I can hear is my mrs saying "your dead if you buy them"

PHILIP HUGHES · Feb 2, 2017

Anyway guys back to reality I think I will be looking to spend the best part of £800, obviously on a second hand set of oems (if I can find some that is) but realistically I'm going to have to lower my expectations for a while. I've been looking on the links you guys have sent me but I'm not getting too far (as per usual). I quite like the look of rs6s also but again its getting right spec in a 19". I think I've just got to take a leap of faith and go for it. Will be posting some pics when sorted. Keep up the good work guys as you have definitely given me a better understanding, albeit slight, but that just the way my brain works (not very technical, but I'll get there in the end haha). Also Rob's made some good points to ponder on, maybe thinking along the lines other makes and models e.g Ronal (good thinking Rob) Lol

Charlie Farley · Feb 2, 2017

audi's and Ronal's is like bread and butter, the two are nearly allways found together ...

PHILIP HUGHES · Feb 2, 2017

Just Rob. said:
audi's and Ronal's is like bread and butter, the two are nearly allways found together ...

I have to agree with you there Rob. Many thanks for your imput. When I do a search on ebay for example, and I put in a search for 19" genuine audi alloys or Ronal they always ask what make and variant of your car, which straight away cuts down my options by at least 75% on models that are SUPPOSEDLY not suitable for my s line b7. Lol

carlcall · Feb 2, 2017

Just Rob. said:
audi's and Ronal's is like bread and butter

In the real world Audi's and Superleggeras are like bread and butter

Sent from my iPad using Tapatalk

PHILIP HUGHES · Feb 2, 2017

I think caricall what I need is just to make a decision and stick to it instead of getting myself all confused as I am at mo. I was really exited yesterday thinking I'd got it all figured out with the rotors 8.5jx19.et35 etc only to find I couldnt get those fitments with those particular alloys. If say for example I decided to get rs6 alloys 1. first of all would they fit my car and what spec would i need the wheels and tyres to be. Just as an example. I have looked on various "look now" links but the info out there is phenominal and too much to take in. If I had a list of makes models with fitments that would probably do it.

Charlie Farley · Feb 2, 2017

with buffalo mozzarella on top

Charlie Farley · Feb 2, 2017

PHILIP HUGHES said:
I think caricall what I need is just to make a decision and stick to it instead of getting myself all confused as I am at mo. I was really exited yesterday thinking I'd got it all figured out with the rotors 8.5jx19.et35 etc only to find I couldnt get those fitments with those particular alloys. If say for example I decided to get rs6 alloys 1. first of all would they fit my car and what spec would i need the wheels and tyres to be. Just as an example. I have looked on various "look now" links but the info out there is phenominal and too much to take in. If I had a list of makes models with fitments that would probably do it.

look guys , Philip is now starting understand the finer details and complex equations involved with audi ownership, welcome to the club Philip , and we've all been there and some of us still are ....no names.....lol

Charlie Farley · Feb 2, 2017

you need decide on wether you want to go oem or aftermarket, once that part is sorted then onto rim diameter , then rim style ,offset can be decided on a rim by rim basis. ,but you need a starting point.

LOOK HERE for information on wheel sizes and offsets

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