So which alloy wheel size REALLY is the best..

[Rosc0PColtrane]

..... or is it just preference??


Alot of people on here go on about 15" or !^2 being the best size alloy wheel for e30's. Frankly, I'm not entirely convinced.

If the smaller size is so great, why do touring cars use such large alloy wheel sizes? Check maxfield sig pic for immediate proof, an e30 touring car with what looks like 17 or 18 inch alloys.

Same with rally. On tarmac stages (normal roads) they tend to use huge alloys, saving the smaller sizes obviusly for the more gruelling surfaces.

Obviously the smaller sizes can assist with dampening characteristics of cars but the rally example to me is good evidence for the larger wheel sizes being used on similar roads to our very own e30's?

So would our issues with the larger wheel sizes have anything to do with cadence and camber as opposed to just being bigger wheels causing the apparant issues?

I fail to believe enthusiasts such as ourselves would have knowledge that would not have been thought of by rally/touring car professionals.

I also remember reading some geeky tech article many years ago on formula 1 using "15inch wheel technology" as an optimum size as the varying wheel pressures are used to adjust the dampening traits of the car so the suspension set up can be as stiff as poss? (Just to try to post a balanced thread)

I just wanted to open a debate on this matter. Input guys!!!!!

Oh I love my 17" alloys and think they rock!!!!! [/u]

[Morat]

I'm no professional and I've no experience.. so I'll shut up then

On the other hand, if the suspension was designed with 14 and 15" wheels in mind, surely its going to work best with them? Even if you keep the correct overall diameter then you're going to lose a lot of the shock absorbency in the sidewalls and your ride will get harsher as a result. If you are lowering/stiffening and changing the shocks then I guess all bets are off since you're really altering the original setup so far that its going to be completely down to your abilities as a suspension guru.

The other thing I'd think about is whether the big wheels fit properly. Surely if they need wobbly spacers or somehow alter the track then they're going to add some more problems all of their own....

Not that I know jack, I'm just keeping the thread alive until someone who knows what they're talking about chips in

The rears don't seem to be all that low profile, although there may be a practical limit on the lowest profile available with such a wide tyre overall ....



edit: search ebay for F1 wheels, there's some very tasty gold BBS on there. I don't think bootyman would approve of the dish tho....

[Rosc0PColtrane]

hahaha,

Can't beat amateurish logic mate, what you said makes sense, hence me prattling on about cadence and camber.

Just waiting for some definitive responses from those in the know now!!

Interesting what the resident zone racer would think too!!!!

Cheers for you input!!

[Dominitry]

Dont forget, those race cars have much more than the bigger wheels applied to them thats not standard, try fitting those brakes in 15" BBS wheels too!

Things are just so much better on an E30 with the 15's rather than sticking 17's on etc, lets face it everyone puts on bigger wheels for looks only, but if you want serious fun in an e30, put some 14" bottle tops on

[m3ben05]

The Group A M3 racers that you mentioned have 18"x10" wheels but dont forget the M3 has the flared arches to accomodate them. They are needed for the massive brakes they run.

Also, take it from me, the suspension is so stiff they can run with a few mm of clearance and nver rub.

If you are talking about buying for a non M3 car, i would stick with the 15" or 16" max.

[Rosc0PColtrane]

Why do 14's 15's etc equal greater fun? Surely the increase tyre height means more roll through corners and less stability?

[Hyperion]

From what i have read, i think the best size for the e30 would be 16" wheels, i was on a mission to find a set of 16" for my car with no luck, In the end i had 2 options, either 15" or 17". I felt going up from my 14" bottles to a 15" wheel might look odd on my car, so i went for the 17" Alpinas , and as you can see in the my sig they look way cool on my car
Oh and blatantarrogance here is a pic of a car riding on 14" putting pedal to the metal, and you can see how much the tyre is flexing!!

[Theo]

Surely race cars have bigger wheels to accomodate the massive brakes!

[Morat]

Surely race cars have bigger wheels to accomodate the massive brakes!

and since F1 cars use carbon brakes... .they don't need to run such massive disks? So, given the freedom to choose their wheel sizes/tyre profiles it seems that F1 teams go for quite high profile tyres. Maybe they need more sidewall with the car being squished into the tarmac by all that downforce?

Here is an article on carbon/carbon brakes which makes me glad they're not road legal ;)

As for the E30, it looks like we need to compromise between handling and braking. We'll have to see how Sal's WMS kits work out under 15" BBS...

[Rosc0PColtrane]

From what i have read, i think the best size for the e30 would be 16" wheels, i was on a mission to find a set of 16" for my car with no luck, In the end i had 2 options, either 15" or 17". I felt going up from my 14" bottles to a 15" wheel might look odd on my car, so i went for the 17" Alpinas , and as you can see in the my sig they look way cool on my car
Oh and blatantarrogance here is a pic of a car riding on 14" putting pedal to the metal, and you can see how much the tyre is flexing!!

Yeah, sweet pic mate. That reminds me of a comment that was past at the Haynes track day recently. "I wouldn't be driving like that with 55 profile tyres", 30 second before understeering tourer with 55 profiles careers into tyre wall!!!

I think 17's look great on e30's too!!

[m3ben05]

Surely race cars have bigger wheels to accomodate the massive brakes!

and since F1 cars use carbon brakes... .they don't need to run such massive disks? So, given the freedom to choose their wheel sizes/tyre profiles it seems that F1 teams go for quite high profile tyres. Maybe they need more sidewall with the car being squished into the tarmac by all that downforce?

Here is an article on carbon/carbon brakes which makes me glad they're not road legal ;)

As for the E30, it looks like we need to compromise between handling and braking. We'll have to see how Sal's WMS kits work out under 15" BBS...

F1 cars use amazingly small brakes -



As has been said mate, it really depends on what your after, for looks - 17's, for handling - 15's

[E30BeemerLad]

got to remember that it's also about the unspring mass.

from my knowledge the BBS 15" are the best you are going to get here in terms of being light. Most aftermarket alloys weigh a tonne, so this causes poorer turn-in and general balance

I had 17" alpina reps on my E30 and personally I was never hugely impressed with the handling/ feel

[Morat]

It seems F1 brakes are limited to 28mm thickness and 278mm diameter by the FIA so that size is not through choice. I guess its a limitation to reduce the overall effectiveness, but over 5G braking is still awesome!

[Rosc0PColtrane]

Surely race cars have bigger wheels to accomodate the massive brakes!

and since F1 cars use carbon brakes... .they don't need to run such massive disks? So, given the freedom to choose their wheel sizes/tyre profiles it seems that F1 teams go for quite high profile tyres. Maybe they need more sidewall with the car being squished into the tarmac by all that downforce?

Here is an article on carbon/carbon brakes which makes me glad they're not road legal ;)

As for the E30, it looks like we need to compromise between handling and braking. We'll have to see how Sal's WMS kits work out under 15" BBS...

From what I remember of the tech article I read, the wheel size means the tyres are an integral part of the suspension set up. Hence the pressure changes in pit stops.

[Simon13]

because an E30 was designed to handle on 15's or smaller.

go look at all the best non M3 track slags 15's and maybe 16's

M3 race cars are a totally different kettle of fish to us and our road cars

[Bob_S]

I cant really fault 15's they seem to be the perfect mix and dont hamper the car like 17's

Dont porsche actually have carbon/carbon brakes on their supercar beast thing and as an option on the newest GT3's?

[Rosc0PColtrane]

because an E30 was designed to handle on 15's or smaller.

go look at all the best non M3 track slags 15's and maybe 16's

M3 race cars are a totally different kettle of fish to us and our road cars

Ref your first sentance: So why then did alpina and hartge slap on some 16's?

Surely the smaller wheels will give a softer ride, but from a performance perspective, the piccy of the severe roll on the 15's above as evidence, lower profile wheels will give more stability?

The race cars owe their heritage to road going versions. You only have to look at the latest incarnations of most cars, the standard cars have smaller wheels, the performance models have larger wheels.

Can you quantify how you would class a car as being the best track slag? is it proven or an opinion? Surely a track slag is trying to emulate a race car, therefore the touring cars in Maxfields signature would be the target to aim for in creating one?

I'm just keen to question popular thinking on this topic, not trying to stir up any ill feeling or animosity, just asking questions, I hope are relevant.

[Rosc0PColtrane]

I cant really fault 15's they seem to be the perfect mix and dont hamper the car like 17's

Dont porsche actually have carbon/carbon brakes on their supercar beast thing and as an option on the newest GT3's?

Think you're right about the brakes, that porsche is awesome. Normally aspirated too. never thought I'd prefer a n/a 911 over a turbo!!!

Not faulting 15's, but how exactly do 17's hamper the car. Under g force, the larger solid area and smaller rubber area means less flex, more cornering stability. Granted there maybe some weight issue but I'm just looking for a generic comparison. TBH you could probably buy some composite alloy wheel that would be as light as the 15's, if you felt that was necessary.

Is it not really a sweeping statement?

[Rosc0PColtrane]

got to remember that it's also about the unspring mass.

from my knowledge the BBS 15" are the best you are going to get here in terms of being light. Most aftermarket alloys weigh a tonne, so this causes poorer turn-in and general balance

I had 17" alpina reps on my E30 and personally I was never hugely impressed with the handling/ feel

I may be misinterpreting "unsprung mass" but I thought that the aim was to have a greater unsprung mass. Therefore lower profile wheels would help to that end? Or am I wider of the mark than Frank Lampards shooting in the world cup?

How is the balance affected? You have a equally weighted wheel in each corner. Also des anyone know what the average %age increase in weight would actually be?

[fly124t]

i think that it depends somewhat on how you use the car, i think i could cruise with 17's at the weekend but i would miss the 15's when takling the trip to work,

i recently aquired a new E30 318is and it came with 17's i loved the look however the handling of the car was very diiferent to my original number, it just seemed wrong

15's can look good if you get the right style, azev a's looks the nuts even in 15's

[ian332isport]

It's not so much the size that matters, it's the extra weight that causes the problems.

If you fit a nice light 17" wheel, it will make very little difference. If you fit a cheap 17" Alpina rep that weighs a ton then you are going to notice it.

As an example, my 7.5x17" BBS RC's weigh 7.34kg and a standard E30 7x15" BBS Crosspoke weighs 7.38kg.

Ian.

[Richy325iTouring]

[quote= if you want serious fun in an e30, put some 14" bottle tops on [/quote]

there a pic somewhere to proove that

[stuartgallafant]

i love the ride and feel i've got with my 7.5" x 16" Azev A's

[Frenchy]

In my opinion for what it's worth 15" max for the E30 i have driven other quality cars with "Big" wheels on felt like shit eg; mate has a 944 Turbo with 19" wheels on looks the part but is aweful to drive Mine ran 17" Porsche Cup alloys (genuine) 100% better the standard issue was 16".

BMW Chassis people knew what they were doing when they designed the E30 i am about to put 15" on my 318iS but know right now ultimately it would handle better with the 14's but it looks nice!

Jim.

[Rosc0PColtrane]

It's not so much the size that matters, it's the extra weight that causes the problems.

If you fit a nice light 17" wheel, it will make very little difference. If you fit a cheap 17" Alpina rep that weighs a ton then you are going to notice it.

As an example, my 7.5x17" BBS RC's weigh 7.34kg and a standard E30 7x15" BBS Crosspoke weighs 7.38kg.

Ian.

Ah, some science at last!!!

Quantified with straight facts!!

Would be interesting to know the weight of the cheaper alpina reps.

Still not convinced just "knowing" that 14's are better. On what basis? Higher wheel tyre profiles = greater body roll and less stability through greater weight shift? Hence H&R cup kits and strut braces and improved brushes. Are all these mods also worse than the original fitments from bmw because bmw didn't use them in the first place?

Alot of decisions about what components are used in cars are based on costs first, not performance first.

Yes the chassis was designed by the clever bods at bmw to the cobnventions of the day, but Hartge, Alpina etc etc decided to improve it and increased wheel size.

Come on you small wheel fiends.... dazzle me with some science!!!!

[Zayyan]

i am about to put 15" on my 318iS but know right now ultimately it would handle better with the 14's but it looks nice!

As soon as you get them on you can post up here to tell everyone you were wrong

Having tried 14s, 15s and 16s it's between the 15s and the 16s for handling. Adding comfort to the equation though the 15s seem to be the best all-rounders.

[Rosc0PColtrane]

i think that it depends somewhat on how you use the car, i think i could cruise with 17's at the weekend but i would miss the 15's when takling the trip to work,

Why?

i recently aquired a new E30 318is and it came with 17's i loved the look however the handling of the car was very diiferent to my original number, it just seemed wrong

How was the handling wrong? And why was it wrong?

15's can look good if you get the right style, azev a's looks the nuts even in 15's

Appearance is down the the preference of the individual, I don't doubt they did look fecking ace!! I am yet to be convinced that generally 14/15's etc are just better!![/quote]

[e30_Turbo]

I've tried:

14 inch bottle tops - tyre profile gave nice ride but poor response
15 inch BBS - best all round performance and IMO the car felt faster
16 inch Hartge - As good as BBS but didn't feel as quick
17 inch Azev A - Good look, ok performance, prone to tramlining.

I'm going for 16's next, best comprimise I feel, poss wider rears to help with grip etc.

There are many e30's on 18 and some on 19's so there is quite a choice to pick from.

HTH, Mark.

[E30BeemerLad]

the main points made so far are surrounding the weight of aftermarket 17" alloys, more weight = less responsive handling & slower acceleration.

another thing is the tyre profile.

17's with 40 profile rubber, whilst also giving a similar rolling radius to a 15 with 50 profile, will give you less comfort, so any pot holes etc and you'll be crashing the suspension big time, also prematurely wearing wheel bearings etc.

But the main thing with the low profile tyre is that although it may give a feeling of a sharper response because there is less sidewall give, so the tyre does not lean before reaching maximum grip, there is far less feel given and a hell of a lot less warning that you are reaching the limits of adhesion. a 14 or 15 inch wheel & tyre combo will give you warning by the grip progressively going and turning into understeer or oversteer, whereas a 17 will just let go and you get a proper brown trouser moment.

When I return to E30 rightness, it will be 15" BBS all the way on my sleeper, maybe even bottle tops for the nostalgia:D Although some 15" MIMS would be top banana

[Frenchy]

when BMW brought out the 318 iS 15" wheels were available ie the 325i sport and to fit these to he 318 iS would have been of next to no cost to BMW.
In fact probably no cost at all as the contract with BBS was massive and the moulds were already there so again it was down to chassis engineers it does feel more nimble on 14's.
I really do believe cost was not an issue but 15" make the car look meatier.

I am having a bit of a job finding some at the mo!

[jonbuoy]

I had a set of 17's on my motor for about 1 1/2 yrs. Everyone was alway's going on about how good the handling is on an E30 but i could never agree as mine was no where near good handling

I chatted to a few people about my problem and they said to go to 15's. Obviously i was'nt happy as i loved the way my car looked with the 17's on but had to make a decision whether i wanted "look's" or "handling". I wanted handling so picked up some cheap 15" BBS's, refurbed them and wacked them on.

What a difference!!
I've got used to the look's now and taken a different course to styling but most of all, i have my handling back...................it's worth the sacrifice!

[Frenchy]

We obviously must know more (NOT)than some very clever German engineers who get paid to do the job.

I am sure you could get an E30 to handle brilliantly on 17" wheels with know-how and loads of dosh.

[Zayyan]

when BMW brought out the 318 iS 15" wheels were available ie the 325i sport and to fit these to he 318 iS would have been of next to no cost to BMW.
In fact probably no cost at all as the contract with BBS was massive and the moulds were already there so again it was down to chassis engineers it does feel more nimble on 14's.
I really do believe cost was not an issue but 15" make the car look meatier.

Bollocks. It'd cost very little more money for BMW to put "Sport" kits on every new 3 series, but unless you pay extra you get standard bumpers.

It's all about marketing - perhaps with the 325i Sport being the "top of the range" model (obviously M3 excluded which is a different matter) and having 15" BBS they didn't want this to be overshadowed by the 318is.

Plus, of course, the dealer would try to persuade 318is buyers to upgrade to the 15" wheels, which would obviously be extra money

The sidewall flex is just too high on 14s (assuming standard tyre sizes) and of course there is less contact with the road in comparison to the 15" wheels due to the tyre width being smaller.

[jaistanley]

The reason the cars handle best on 15"s (or indeed the wheel they were designed to run on) and not aftermarket wheels is that certain geometries are programmed in.

The king pin inclination is the angle of the centre of the wheels effective contact patch to the pivot point of the top of the McPhereson strut. This and the slip angle of the tyre determine the dynamic camber and castor of the wheel.

If you choose the offset, width and tyre profile correctly you can reduce adverse effects. Smaller profile tyres, to a point, can improve the feel of a car but has two nock on effects. The slip angle of the tyre is reduced and on rough surfaces has less compliance so don't deform to maintain grip.

Changing diameters widths and profiles also changes the shape of a tyres contact patch. Different shapes exibit different characteristics of grip and camber thrust.

The cumulative effect of the above are the symptoms you describe. 'Not feeling right'. Rather than go into detail (and have to look stuff up in uni notes - quit while you're ahead!) I'll leave it at that!

Touring car wheels were massive to accomodate massive brakes and reduce tyre temperatures and pit stops (wear).

Jai

[CraigG]

Are all these mods also worse than the original fitments from bmw because bmw didn't use them in the first place?

Alot of decisions about what components are used in cars are based on costs first, not performance first.

not only cost, but comfort, most E30's were not outandout performace sport cars, but upmarket saloon cars, ergo, they had to be comfortable, HnR cup kits, rollbars and polybushes dont exactly give the smoothist of rides now do they?