Advice sought on winter wheel/tyre combo

Z

z4james

Member
Hello,

I've been reading through the posts related to winter tyres and found them really useful. I think I know my next step but wanted to check with those with more experience.

Currently, our 2008 2.0 Sport Z4 has:
- 225x40x18 on Composite Star Spoke (code 108) 8Jx18 wheels (front)
- 255x35x18 on Composite Star Spoke (code 108) 8.5Jx18 wheels (rear)

I've had two options from two different BMW dealerships, one for 225x45x17s and one for 16" wheels, but both wanting around £1800. Gulp. Clearly there are better options online and I'm currently considering a set of 16" Dezent alloys with Continental Winter Contact Runflats 205x55x16 for about half that.

I'd be really grateful for the view on the following questions:
1. 16" wheels will be cheaper, reduce the risk of kerbing the alloys, perhaps give a softer ride, but won't look as good as bigger wheels - am I right to go for 16" over 17"? And is 205x55x16 or 225x50x16 the best option?
2. I hear that Runflats are rarely repairable, so should I go for normal tyres and a can of inflation foam, and save some money?
3. If normal tyres are ok, anyone got any views on Syron Everest winter tyres (German company, Far East manufacturing, cheap)?
4. Lastly, I'm told that the 16" Dezent wheels will fit straight on to my Z4 without any adjustments with spacers or offsets - is that correct?

Many thanks for any help,

James
 
Hi James , i wouldn't go as low as 16's on the car . it will look naff .
A decent set of 17inch replicas with the winter tyres should set you back around £750 . Yes a lot of money but well worth it if you need the car in all weathers . I fit these http://www.mytyres.co.uk/cgi-bin/rshop.pl?details=Ordern&cart_id=15469001.110.27547&typ=R-169654&ranzahl=4&Breite=225&Quer=45&Felge=17&Speed=H&weiter=20&kategorie=6&Ang_pro_Seite=20&sort_by=preis&Transport=P&dsco=110&sowigan=Wi to my wifes Golf in october & they have been fantastic ( need some deeper snow for real test :wink: )

Fit them on something like http://www.ebay.co.uk/itm/BMW-MINI-17-Inch-WHEEL-SET-SILVER-SATIN-GLOSS-Set-4-/150979231265?pt=UK_CarParts_Acc_Wheels_tyres_Trims_Car_Rims_ET&hash=item2327103e21 & you will get good money back should you not need them in the future 8)
Just don't forget the tyre gunk/inflator though :thumbsup:
 
Apologies for jumping in on your thread and adding more questions, but they may be useful to your question as well.

Edit: Fixed inability to add in calculations!
You have the same alloys/tyre sizes as me, giving a front diameter of 630mm (450mm alloy, 40% of 225, 90mm tyre) and rear diameter of 628.5mm (450mm alloy, 35% of 255, 89.25mm tyre).

Your option of 16" alloys and suggested 205/55/16 tyres gives a diameter of 625.5mm (400mm alloy, 55% of 205, 112.75mm tyre), so a drop of about 5mm.
Your option of 16" alloys and suggested 225/50/16 tyres gives a diameter of 625mm (400mm alloy, 50% of 225, 112.5mm tyre), so a drop of about 5mm.

I'm considering 225/50/16 winter tyres as they would make a useful spare for longer journeys and 16" will be lighter than 17". Maybe it's a stupid idea, but with a 17" spacesaver costing £100+, you can find a set of second hand 16" Z4 alloys being offloaded around that price.

However, I know I'd need a 17" spacesaver to fit over the callipers on my 2007 Coupe Sport, so perhaps 16" alloys won't fit either? With 17" alloys, I'd need 225/45/17, but the alloys weight more and the 17" alloys will cost more. In my case, I'm considering the 2 birds with 1 stone as I need a spare wheel, but don't really need winter tyres as I have a second vehicle. Winter tyres and a spare for a few more pounds, why not :) Any thoughts?

* assuming alloy sizes aren't actually imperial and they use 25mm per inch, rather than 25.4mm
 
@Stovax: I don't think the difference is as great as your calculations suggest. An online tyre calculator (I used http://www.miata.net/garage/tirecalc.html) gives the following:

Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
255/35-18 3.5in 12.5in 25.0in 78.6in 806 0.0%
205/55-16 4.4in 12.4in 24.9in 78.2in 811 -0.6%

Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
255/35-18 3.5in 12.5in 25.0in 78.6in 806 0.0%
225/45-17 4.0in 12.5in 25.0in 78.5in 808 -0.2%

...so at 60mph the speedo is only out by 0.36mph with the 16s and 0.12mph with the 17s.

@Mr Wilks: thanks for that - did think 16s might look a bit small - now looking at 225/45-17s with non-runflats
 
Just corrected my post above, you should add the tyre profile twice to overall diameter, not once :rofl: With the new figures, your suggested winter tyre sizes do match the original set.
 
16s won't fit over the front callipers on a 3.0. I believe that BMW recommend 17" wheels with 225/45/17 tyres all round for winter driving on the 3.0 - not sure about on the 2.0, sorry. I have 225/45/17 on at the moment, Avon Ice Touring, nice mid-range tyres that work just fine for me and are on their second winter :thumbsup:
 
If anyone wants to have a play with tyre sizes/wheel sizes here's a link to help you
http://www.kouki.co.uk/utilities/visual-tyre-size-calculator :thumbsup:
 
It's a lot of relatively cheap 17" unoriginal alu rims out there, it should not be difficult to find something that suits your car. Find yourself a smooth type with few spokes, that will ease the cleaning of the rims during the winter. When it comes to the tyre's, do not choose an unknown and cheap type. Go for a type that have good test reports and is well known in the market. Remember that the tyres are your "shoes" and is the only contact between you and mother earth when you are driving. A good tyre have the margins that may save you from a crash in a difficult situation :!:
 
Im using contiwinetcontacts 225/45/17 all round and they're quite good, but next winter will probably swich to pirellis sottozero, as they're said to be much better.

TapaTalking
 
Thanks for all the advice on this. I got hold of a second-hand set of BMW alloys (225x45/17 with pattern 103) with Continental Winter Contact tyres all round (with 1000 miles of use).

Do I still use the same pressures as my old set (i.e. 2.2 bar or 32 psi on the rear, and 2.0 or 29 psi on the front)?

There's a bit of a thrub-thrub-thrub noise at times, particularly noticeable when coming off the gas at 40+. I didn't notice on the ~15 mile test run on Sunday but my wife did her 35 mile round trip commute with them today, including some dual-carriageway.

I haven't had the new wheels balanced - I just put them on myself after buying them, so I'm hoping that's what is needed. But grateful for any other thoughts or suggestions? (It didn't makes any noise with the old wheels, so I'm ruling out bearings etc).

Thanks,

James

P.S. Now I'm not on run flats, I also put together my own mobility pack - compact tyre compressor plus two cans of Tyreweld, fluorescent jacket and gloves, all bagged up for around £27 - slightly cheaper than the BMW Mobility Pack :D
 
We're your old wheels 18"? If so don't rule out a wheel bearing as there will be less road noise on smaller wheels with higher sidewalled tyres.

Hope you got a bargain on the wheels/tyres. I run 16" with 205's all round on budget winter tyres and have found the Z unstoppable in the snow. Rims were £80 (102's I think) that came with 2 good RFT's that I sold for £100 and the winter tyres were £50 each so the entire set up stands me at £180 :D
 
Yes they were 18s but I don't think they were noisy enough to mask the sound I'm now hearing.

I got a bargain compared to the £1800 that BMW wanted for the same set. But not quite the bargain you got ;-)
 
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