I've read numerous posts here discussing tyres and that most favour getting rid of run flats. I also see many change the size of their tyres to a slightly larger tyre. I currently have run flats, 225/35 19 on front, and 255/30 19 on rear. 2012 E89 28i with M Sport suspension. Not a daily and is not used at track days or driven really hard. The inside edge (approx. 1"-2") of the rear tyres are wearing really badly. I spoke to tyre guy today and he said the wearing is standard across the range with BMW. He has tried fiddling with the alignment but it effects the feel of the car and has had people come back within a week asking to revert the settings because the car felt so bad. (Tyre guy was not specifically talking Z4, but BMW.) Discuss. Next, ditch the run flats. I asked about increasing the rear tyres to perhaps a 255/35 19. I don't want to risk going too large as the sport suspension might result in tyre and car touching. Again my tyre guy said changing the size will impact the feel plus impact the ABS and other sensors the car has around the wheels and the car will feel 'out of whack'. Discuss. He was ok with run flats on front and just replacing the rear with non run flats, but did say it would feel hard at front and softer at the rear, even though not much as the tyre size isn't changing, just softer walls. I would only do this, maybe, whilst the front tyres were, and are , still good. I know there are numerous opinions on this and many have changed sizes, changed alignment or just been happy to get new tyres more frequently. So there I am, confused.
Tyres and confused
- Thread starter YDB
- Start date
I did some research on this subject before buying NRF Michelin Pilot 4s recently. Mine is a weekender car and I wanted a better ride. Everything I read says your Tireguy is right about the inside wear being a common BMW trait... expect it. Since you are not tracking the car comfort may be a priority, it was for me. I improved the ride with NRF (softer) tires and stayed with my 4" sidewall. Non M 225-45-17s I believe. IN your case you may want to buy smaller rims thus increasing the size of the sidewall = softening the ride without changing tire height and negatively effecting speedo and ABS etc.
That's if rims are in your budget.
That's if rims are in your budget.
Mmmm! Hadn’t given that any consideration. I do like the look of the car with the 19’s on though. I just struggle to look at what is otherwise a good tyre, except that narrow inside strip that screams out that I won’t pass rego next time. Food for thought when the time comes, if so, to replace the wheels. I hadn’t seen anyone else mentioning change wheel size albeit they might already have the smaller wheels. I might have to budget the budget, eventually.scootr said:
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The tyre guy is correct in that it will impact the feel of the car and also have an impact on ABS and DSC. Whether you can personally feel the difference is another question, it's quite a small change to the rear rolling radius so the ABS and DSC won't work as effectively but you probably wouldn't notice without doing some in-depth testing.
Inner edge tyre wear is a common issue with BMWs but I've not experienced it with the Z4.
Inner edge tyre wear is a common issue with BMWs but I've not experienced it with the Z4.
Attleborough, Norfolk
R.E92 said:
Worth noting that the OP spoke about increasing to 255/35 on the back, whereas Mr Wilks recommended 245/35, which should reduce the rolling radius change somewhat.
Just thought I'd add that, as it is very easy to miss the subtle difference in the text.
R.E92 said:
Splitting hairs implying the Abs & Dsc sensors will be affected.
How do they cope from a Se 23i on worn down 18inch summers switching to brand new 17inch winters?
Or from 17inch worn runflats to brand new 19inch non runflats.
There are so many different wheel /tyre options on these cars the sensors must have a range they operate within otherwise each car off the production line would need specific sensors based on its wheel, tyre & suspension package.
As for the tyre shoulder wear being common to BMW ?
Never experienced it in over 25 cars but maybe not kept one long enough
The wheel and tyre size is not important, what matters is that the overall diameters of the tyres on different sized wheels remain the same otherwise the speedo, for example, will not read correctly. Plenty of enthusiastic BMW drivers don't like runflats and are pleased to have thrown them away.
Overweight Unicorn
Member
I have the same model and wheels as you. I changed the rears to Bridgestone Potenza run flats (as that is what I was changing from) 255/35/19 and the ride is softer. Still hard, but definitely softer.
On my second Z4, neither exhibited uneven tyre wear!
Don't change tyre sizes, it's not just about dry grip, wet is the most important issue, obviously.
If you increase the tyres contact area with the road i.e. increase width you are decreasing the total load on the contact patch, this also reduces the tyres abiity to pierce the surface water as it is more lightly loaded!
Consider this carefully, BMW fit the best and safest tyre/wheel options (optional extras included) at build
Don't change tyre sizes, it's not just about dry grip, wet is the most important issue, obviously.
If you increase the tyres contact area with the road i.e. increase width you are decreasing the total load on the contact patch, this also reduces the tyres abiity to pierce the surface water as it is more lightly loaded!
Consider this carefully, BMW fit the best and safest tyre/wheel options (optional extras included) at build
mcbutler said:
You might have a problem there, the higher powered variants of the E89 come with staggered wheel sizes. BMW clearly sold you a dangerous vehicle as your 35i has wider profile rear tyres. How have you managed to pierce the surface of the water with 255 rear tyres?
R.E92 said:mcbutler said:
You might have a problem there, the higher powered variants of the E89 come with staggered wheel sizes. BMW clearly sold you a dangerous vehicle as your 35i has wider profile rear tyres. How have you managed to pierce the surface of the water with 255 rear tyres?
Whoooops
to repeatmr wilks said:R.E92 said:mcbutler said:
You might have a problem there, the higher powered variants of the E89 come with staggered wheel sizes. BMW clearly sold you a dangerous vehicle as your 35i has wider profile rear tyres. How have you managed to pierce the surface of the water with 255 rear tyres?
Whoooops
"BMW fit the best and safest tyre/wheel options (optional extras included) at build"
my 35i has tyres and wheels as per original fit.
If you doubt that putting on replacement tyres with a greater contact patch reduces wet grip then that is your choice, just take care.
mcbutler said:to repeatmr wilks said:R.E92 said:You might have a problem there, the higher powered variants of the E89 come with staggered wheel sizes. BMW clearly sold you a dangerous vehicle as your 35i has wider profile rear tyres. How have you managed to pierce the surface of the water with 255 rear tyres?
Whoooops
"BMW fit the best and safest tyre/wheel options (optional extras included) at build"
my 35i has tyres and wheels as per original fit.
If you doubt that putting on replacement tyres with a greater contact patch reduces wet grip then that is your choice, just take care.
That's fair enough but i suggested 245 35 19 on 9j as opposed to 255 30 19 as Bmw oe
Wouldn't the original have a wider contact area :? Unless driver is 19stone & always drives with a full tank