e30 wheel offset

[fozzy325is]

what is it ET??????

[iDreamBeemer]

24

[nav786]

24 is the standard for the BBS wheels, but it can vary, between 15 - 30ish depending on wheel width is normally ok

[orangecurry]

as the man said, depends on the rim width

BMW Bottletops 6jx14h2 et35
BMW BBS 6.5j x 14h2 et30
BMW BBS 7j x 15h2 et24
Hartge 7.5j x 16h2 et25

for comparison, VW steelies 6jx14h2 et38

[m-dtech]

what is it ET??????

[thebigone]

spot on M8

[nav786]

what is it ET??????

sad but that made me chuckle

[tim-ix]

And to make my life difficult my 325iX needs a 41mm offset for a 15" rim. I'm wondering whether I can machine 17mm off the inside of a set of normal 15" BBS cross-spokes. I don't know whether there's enough metal there to safely do it.

[loggyboy]

And to make my life difficult my 325iX needs a 41mm offset for a 15" rim.

Rim diameter bares little consequence to offset, its the width that is the key factor. (allthough of course dia and overal rolling diameter inc tyre still needs to be accounted for)

You have the advantage of having vauxhalls being set at 45-49mm ET so you can buy rims designed for them (obviously not OE stuff) but aftermarket items will be widely available.

I have a guide to offset fro complete novices here
http://forums.roybacer.net/index.php?showtopic=1461

it also links to a handy tyre size calculator/comparer.

[tim-ix]

Thanks loggyboy.

I found the following numbers on an American site for the iX -

14"x 6 offset 47
alloy rims:
14"x 6,5 offset 45
15"x 7 offset 41 - 205/55
16"x 7 (7,5) offset 38 - 205/50
17"x 7 (7,5) offset 35 - 205/45 or 215/40

At the risk of asking a silly question, do I need to take anything other than rim diameter, width, offset and PCD into account? I'm thinking about hub size and spigot rings etc. I don't want to spend a load of money on something that won't fit.

I'd like 16"s so if I can find something I like with the right PCD and an offset of 38mm or larger I should be okay, though I may need to use spacers to get the positioning right and avoid excessive bump steer or tramlining.

Am I right with my suppsitions or am I heading for expensive misery?

[loggyboy]

Yes bore size needs to be accounted for or they may not fit over your hub centres.
unfortunately im new to BMs so cant give any sizes for that.

Of course the other main consideration is tyre size, no point in going for rims that need tiny (or unpopular) profile tyres that will cost a fortune.

[DaveD]

if anyone wants a copy of the best tyre and wheel size calculator i have seen send me an email address and i will send it to them

[orangecurry]

Thanks loggyboy.

I found the following numbers on an American site for the iX -

14"x 6 offset 47
alloy rims:
14"x 6,5 offset 45
15"x 7 offset 41 - 205/55
16"x 7 (7,5) offset 38 - 205/50
17"x 7 (7,5) offset 35 - 205/45 or 215/40

At the risk of asking a silly question, do I need to take anything other than rim diameter, width, offset and PCD into account? I'm thinking about hub size and spigot rings etc. I don't want to spend a load of money on something that won't fit.

I'd like 16"s so if I can find something I like with the right PCD and an offset of 38mm or larger I should be okay, though I may need to use spacers to get the positioning right and avoid excessive bump steer or tramlining.

Am I right with my suppsitions or am I heading for expensive misery?

you can simply measure your current wheels for hub diameter - apart from that the crucial one is PCD, closely followed by offset - I think you would get away with at least ET5 either way

IMHO you should buy the best quality wheels you can find, esp if 16" rims as 50 profile isn't the deepest in the world, and the first pothole may easily bend/distort cheap rims.

Tramlining is more a feature of tyre width - 205 is not too wide on an ordinary E30, but of course your iX has a wider track.

Good luck.

[E30Adam]

I'm wondering whether I can machine 17mm off the inside of a set of normal 15" BBS cross-spokes. I don't know whether there's enough metal there to safely do it.

No, no, no, no. Never take material from the mounting face of a wheel to change the offset. Dicing with death.

[loggyboy]

No, no, no, no. Never take material from the mounting face of a wheel to change the offset. Dicing with death.

Not strictly true, how do you think wheel manufacturers acheive different offsets? certainly not a different mould for each one!

However there are points where you can go to far, so its 'best' not to mess unless you are 100% it wont reduce the integrity of the wheel. and of course, if you do do it, it needs to be perfectly done by a proffesional

[tim-ix]

No, no, no, no. Never take material from the mounting face of a wheel to change the offset. Dicing with death

This is exactly what I've worried about. BBS did supply a 7x15 cross-spoke for the iX but I might as well try finding some fragments of the true cross for my door cappings as look for them here.

The car looks good at the moment from the back with the standard E30 15s but looks cack from the front. It needs fairly wide wheels and tyres to look good because of the wider bodykit. My preference is for period-style 80s wheels along the lines of the Ronal Turbo or similar. I've got H&R lowering springs for the car and Koni are making some shocks for me at present.

Thanks all for answers everyone. I'll put some pics up of the car once I work out how.

[micktdel]

Tim-ix where are you based? I have a set of 16 x 7.5 ET 35 with 205/45 tyres on 2 of them that you can try out to see if they fit. They are just cluttering up my garage at the moment. Until I decide to sell / fit them to my iS.

Mick

[orangecurry]

No, no, no, no. Never take material from the mounting face of a wheel to change the offset. Dicing with death.

Not strictly true, how do you think wheel manufacturers acheive different offsets? certainly not a different mould for each one!

yes they do have a different shaped wheel - I'll take some pictures later to explain, but that's how e.g. Speedline do theirs

[loggyboy]

well yes, for odd manufactuers such as vauxhall with 49mm offset, sum companies like compmotive for example, they produce a special design of the MO that allows for the high ET. HOWEVER that design is now the standard for all MOs produced. You will note on compomotives the ET is stamped on the wheel post production AFTER they have machined the wheel to the desired offset.

ie:


note the moulded dia & width and stamped ET ;)

All mounting faces will be a machined finish as if moulded they would have too many inaccuracies to remain balanced (except steels, which ar formed rather than moulded/cast)

[orangecurry]

piffle - Speedline make wheels for everyone

here's 2 of their wheels - the same size, the same wheel in fact, GC-07B IIRC



but if you look at them from the side, they are a totally different shape in the centre to give different offsets...

ET35



vs ET 52



thanks must go to the 'Loft Wheelery' for the loan of these examples

[loggyboy]

But your showing 2 extremes there - Those wheels would be available in a lot more offsets than those 2, would they have 2 different moulds for a 30mm offset and a 40mm? of course not, they would machine them to suit. Yes they may have 2 moulds to give as much variatey as possible, as I already stated that compomotive do/did.

Those pictures you show, show a clear excess of material in the 35mm version compared to the 52mm version. meaning the 35mm version could easily be trimmed to accihieve a different offset.

[m-dtech]

best bet is vauxhall rims with a hubcentric spacer

[orangecurry]

arguing? Here on the zone? Never

the camera angle is not misleading - there is no 'excess of material' on the ET35 offset wheel - the 5x steel sections/tubes/sleeves where the bolts sit are the same length on both wheels - so the bolts sit inboard much further on the ET35 wheel if you see what I mean - the wheel is a very different shape; only a very SMALL amount/depth of machining could take place.

And I'm not showing extremes - offset can go as 'low' as 10 or 15? These wheels offsets are only 17mm difference, and yet Speedline did bother to make very different shapes for the centre.

[loggyboy]

High offsets are harder to cater for, it requires a special design that means the spokes need to 'stick out' more. just check the design of the MOs, speedline allesios (one of the only rims available in 16"x6 with 49mm offset) and the wheels u posted, they all have spokes that stick out. You cant do 'deep dish' style rims on high offset cars, its nearly impossible to get arch and caliper clearances.
General manufacturers will always cater for the 95percentile. The extremes like vauxhall and subaru that have high offsets (close to 50mm) are catered for by specialist like speedline and compomotive, but you try and find a tsw or team dynamics rim in anything more than 45mm offset, you will struggle as they design one mould and machine the offsets that are most common (the VW/ford etc etc 30ish)

[orangecurry]

so quality manufacturers do the job properly, and 'Cheapo-alloys-inc' machine a bit off? I'm happy with that summary

But Speedline are not 'specialist' - they do some of the 'standard' Original Equipment alloys for Alfa Audi Peugeot Citroen Fiat Ford Lotus most Jap.......... loads more I'm sure

[loggyboy]

Bored now

[tim-ix]

Thanks for the offer micktdel but I'm at the end of the world (nearly) in Swansea.

[bigpimpin]

Have a look at this

http://www.alloywheelsdirect.net/bmw_wheel_fitments.pdf

Cut and paste into your browser cause link doesn't work properly ?

[orangecurry]

I only get Mercedes wheels with your link

m m m m m m m
that company has genuine 16" Alpinas; only 940 GBP... plus VAT?

[bigpimpin]

Yeah, its a bit funny?

cut and paste the link and should open up the pdf. I'm gonna host it on my website to sort it out.

[loggyboy]

http://www.alloywheelsdirect.net/knowle ... ting_chart

then click the bmw pdf

**EDIT - no its an error on their website by the looks of it