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[driven1]

Would there be a problem in downgrading my wheels and tyres and is there any advice you can offer? I'm looking at buying a 2006 e90 325 ZMP that has 18inch 193M wheels (nearly all ZMPs have 193M here).

I have read that the ride will be harsher than it needs to be, rim damage can occur (we have very bad roads here), hurts my insurance and the cost of tyres, rft or normal, will be very high. I am not really interested in looks and I fear bmw 16 inch alloys will be too pricey. I would like to do 1/2 trackdays a year for fun/car control, not really to post fast times or compete with others, and that would also increase wear making 18in tyres short lived and very expensive. So, I was thinking of downgrading to non-staggered 16in wheels with a normal(ish) profile.

1) What information do I need to know when shopping for new alloys? Is it enough to ask the local independent alloy shop for a 5-bolt, 16in rim that will take (at least) 205mm wide tyres? Are they all the same?
2)Will non standard alloys work with RFTs? How will the car know if there is a leak in the RFTs?
3) Looking at the calculator above, my speedo should overestimate my speed, shouldn't it (I'm not fussed by this)?
4) Will the reduced tyre size cause any problems with traction control?
5) Will I have a further reduced ride height (I really don't want that given our roads)?

Sorry for so many questions, I don't know much about wheels and tyres other than what I've learnt here over the last few months. Depending on the cost and your answers, I may have to just go with the 18in and non-rfts.

[AlanAZ]

I may have to just go with the 18in and non-rfts.

That's the answer. The BMW wheels are quite strong (they have to be to be able to drive on a flat tire for 80 mls and not be damaged), and replace the runflats with non-runflats to give you a much better ride, lower purchase cost, and increased wear rating. Get a Conti mobility kit for when you do get a flat. You can sell your new runflats for more than what the non-runflats will cost.

Tires to consider: Bridgestone RE760, and Hankook evo V12.

I have staggered 18's with RE760s on my 325 sport and it's good setup all around.

[prototyp]

Which brand RFT do you have? RFT from one brand ≠ RFT from another... I recently went from Bridgestone to Michelin and the difference is about like this:



the 193M's... they're just starting to turn up in option packages here.

[AlanAZ]

Which brand RFT do you have?

Tires in Australia are about twice as expensive as here, so keeping PS2s on the car, especially with occasional track days, would be super expensive.

[Stuart@BMRAutowerkes]

To the op LOL I thought you were in some third world country or something where you share the roads with cattle and stuff from the way you describe your 'need for smaller rims' but you're in Aus?!

I'm a Sydneysider myself and unless you plan on carrying loads and loads of fine china, houses made from cards and performing open heart surgery in your vehicle all at the same time I'm very confident you will not find Msport suspension with 18inch wheels unbearable!
To improve the ride, go with non-run flat tyres. Simple. Keep the 18s because 16s are weak and not worth the hassle.

As for your other issues
1) Bolt pattern is 5x120, no they are not all the same but I really don't want you putting 16s on your car!
2) can't help you
3) It may overestimate your speed, no biggie
4) Thinner tyres (eg 205 v 255) will have less grip than bigger and wider wheels. That said, 16s with the right tyres can be quicker than larger wheels due to the effective gearing of the wheels.
5) The ride height shouldn't be too different. When you go to a smaller wheel, the tyre profile increases and vice versa - it keeps the vehicles height at a ballpark figure.

Whereabouts are you from anyway?
Do you have to navigate potholes like this lol

[driven1]

Hahaha. No, I'm from Sydney as well. It's just that the road I take to and from work seems to have 3-5 recurring potholes each way. It rains, potholes get worse, it gets a cosmetic fix and gradually gets worse again until it rains again.

Perhaps I've been reading too many posts about 19in tyres with RFTs getting hairline cracks in the rims and assumed that also applied to 18s.

On the 193Ms, they are 255mm wide at the rear - could I fit narrower, eg 225mm tyres on there? 255mm just seems a bit excessive (and no doubt you pay a bucketload for them)...maybe it's just me.

16s are standard on the 4cylinder and lower 6cylinder 3 series here - are they really that bad?

[cyphr]

Originally Posted by bmroxm5

To the op LOL I thought you were in some third world country or something where you share the roads with cattle and stuff from the way you describe your 'need for smaller rims' but you're in Aus?!

I'm a Sydneysider myself and unless you plan on carrying loads and loads of fine china, houses made from cards and performing open heart surgery in your vehicle all at the same time I'm very confident you will not find Msport suspension with 18inch wheels unbearable!
To improve the ride, go with non-run flat tyres. Simple. Keep the 18s because 16s are weak and not worth the hassle.

As for your other issues
1) Bolt pattern is 5x120, no they are not all the same but I really don't want you putting 16s on your car!
2) can't help you
3) It may overestimate your speed, no biggie
4) Thinner tyres (eg 205 v 255) will have less grip than bigger and wider wheels. That said, 16s with the right tyres can be quicker than larger wheels due to the effective gearing of the wheels.
5) The ride height shouldn't be too different. When you go to a smaller wheel, the tyre profile increases and vice versa - it keeps the vehicles height at a ballpark figure.

Whereabouts are you from anyway?
Do you have to navigate potholes like this lol

This is correct. Some things to add.

4) Make sure you use the tire calculator above to make sure your rolling diameter is the same as stock. You won't have traction control issues if you stick to those guidelines.

16" wheels might also run into clearance issues with the brakes.

[sbce90]

I don't think you should get 16s on a car with Msport. Have you thought about the 17" 194M wheels? They're smaller and you can keep the full Msport pack look too. Personally I would go for the 194M with non-rft if I was in your position.

I'm on 193m with rfts in Sydney and I find it okay. Certainly not Mercedes smooth ride though.

YAY for NSW roads!

[AlanAZ]

BMW are "super expensive" in Australia, so I am not sure I am following your point?

In tires, what one recieves in performance in the later stages of tire wear especially is pretty well correlated to what one pays initially.

Yes, BMWs are super expensive down there, my sister-in-law has a 323 coupe, but with non-runflats you can get similar or better performance for half the (big) cost. Plus Australia has the same problem as some parts of the US, where the distances to drive to a tire store are greater than what you can do on a flat runflat, and you'll want a mobility kit anyway.