Run flat tyres with standard rims?

[Medicman1972]

Hi everyone I’m a newbie so be gentle!😄
I’ve just got a 2011 Z4 35is. With 31,000 miles on it. Generally really happy with the car but I have a problem..
When driving the car in a straight line on a smooth road, the ride is firm but bearable. If I corner either left or right and go over a bump at the same time (even a small one) the car jolts.. similar to a scuttle shake type thing, it really spoils the ride.

I’m running the following setup which I believe is standard for the 35is:
Rear-255/30 R19 Bridgestone Run flats (RFT)
Front-225/35 R 19 Bridgestone run flats
Both on standard rims, all pressures checked and correct. No defects in tyres. Lots of tread left.
The car has not been modified in any way..yet🤣
How can I improve the ride without selling a kidney to pay for it?😀

If I switched to Michelin pilot sport 4s tyres (£750 or 1300 USD for four) how much will it improve the handling/comfort if any?And can they be fitted to standard rims that previously had RFT on them?
I will spend the money if it improves things..
I realise that 19” wheels on any car isn’t going to give the best of rides but this is shaking the fillings out of my teeth!😃
I’m also considering getting four wheel alignment done as well.
Thanks for any advice you can give

[KennyP]

Coming from Supersport tires...

Handling benefits are definitely noticable... more stable at speed, sharper steering, more control and grip is good aswell.
When i did my first testdrive after going from RFT to Michelin i remember being amazed how much better my car handled, i could place it on the road much more accurately.

Comfort: It is better, but there is only so much you can improve with such a thin tire sidewall. And that sidewall still needs to have some stiffness for the handling benefits. It does improve the ride somewhat but for me tires + quality suspension setup did the trick.

If you still have life left on your RFT-s then you could just use them up and replace with Michelin when they are done.
If they have a lot of tread left you could try to sell your RFT tires to get some money back.

I think i got Michelin Pilot Superspots in 2017 spring, right when PS4S came out. PS4S did not have enough reviews yet and Supersport was really well established and praised so i went with the older model. Its been 4 years and around 25000km of driving on them. I am going to replace them next spring. Not for running out of tread (still a lot left in the front and ok tread depth in the back) but just because they are actually starting to get old. Rubber compounds lose their properties, sidewalls show first signs of drying up and starting cracking and so on.

For the same reason i replaced my winter tire set aswell. A lot of tread still left but just got old and rubber loses its properties and turns hard.

You can check your tires production date, it is usually marked on the sidewall. Google helps to do that. I think the recommended life of a tire is 4-5 years. So even if not driven that much you still should replace tires every 5 years max.

PS4S according to reviews and comparisons should be more comfortable than older Supersport model.

I have same 19" oem tire sizes as you mentioned.

[Medicman1972]

Kennyp
Thanks for the reply. There’s plenty of tread left in the RFT,s so will maybe just leave it for another year. Could you confirm that I can put non RFT on standard rims?
What suspension mods did you do and how much of a difference did it make?
Thanks

[KennyP]

Yes you can put non RFT on standard rims.

I have KW v3 suspension that has separate rebound and compression adjustment. At stock KW settings it was too stiff for me so i softened the settings until i was happy with it. This kit comes with progressive springs aswell.. these are softer at first and stiffen up as they compress more. Eibach springs should be progressive aswell. So these springs aid somewhat aswell.
I did have issues on bigger bumps but after raising the ride height a bit to have more suspension travel im totally happy with the setup. And here in my area roads a not that good, especially smaller curvy b roads that are old and really bumpy.

Suspension is a very subjective thing so what works for me may not work for others. Proboner has a long thread here changing his setup numerous times in search of what works for him.


I suggest checking the production dates on your tires. Your car is low miles but still 10 years old (2011 production if im right?) and when going with the 5 year rule it should have got new tires in 2016? So the second set is maybe 5 years old already aswell and tires rubber has got a bit hard resulting in crappier ride.

[Medicman1972]

Thanks once again for all of your help, you have been fantastic. I will check the manufacture date of my tyres. Have just looked and there is a KW dealer 5 miles from me, I will go and make some enquiries about suspension.
Thanks

[proboner]

Id be very wary of going aftermarket suspension if the stock stuff is already harsh for you. Get new tires first (The PS4S will be a great choice) and see how it changes the comfort of the car. I can basically guarantee going to an aftermarket "race" suspension will not make you happier in the comfort department.

[Marcoose]

Originally Posted by proboner

Id be very wary of going aftermarket suspension if the stock stuff is already harsh for you. Get new tires first (The PS4S will be a great choice) and see how it changes the comfort of the car. I can basically guarantee going to an aftermarket "race" suspension will not make you happier in the comfort department.

Hey, I'm in San Francisco. Hi!

On my first proper ride, in the Foothills, even wifey, as a passenger, complained the car was understeering. And it was. Badly. So the local indy did the mods in the sig, plus -5 degrees front camber. Boom. The car turns just by thinking of turning. A++.

But, yeah, the ride is very hard now. You think the airbags will pop with every bump.

[Medicman1972]

Addition- just ordered 4 michilin PS4s tyres. Having them fitted tomorrow (21st July) will report back on handling, comfort etc. This might assist anybody that’s in the same boat as me with the dreaded RFT.
Will report back ��

[Marcoose]

Medic, FYI, with my setup, I'm running 34F-38R psi cold, 37F-41R psi hot. Again, see suspension setup in sig below. And about -5 deg camber on all four. I went up a local twisty yesterday (CA Hwy 84 from Woodside to CA Hwy 35), very spirited run, not a single screech, not a millimetre of understeering. Planted thru and thru like the doctor ordered.

I hope your setup will be to your liking.

[Medicman1972]

Ok so a follow up to my previous post re changing from RFT (runflats) to PS4s
Had the tyres fitted today, total cost was nearly £700 which hurt a bit!😢
I can report the following improvements-

Ride quality- improvement of about 80%. The car no longer crashes into potholes, shaking my fillings out! The ride is now much smoother and much more forgiving.
Cornering-50% improvement. Steering/cornering is more precise, the car now stays where it’s put. I can now corner at higher speeds confidently.
Wet weather ability-can’t comment as it’s hasn’t rained yet.. really unusual for the UK!!😂
At the moment I’m running the same pressures as the RFT were on. Will give it a week and maybe experiment with reducing slightly.
Thanks again to all those that gave me some valuable advice about tyres and suspension etc, being able to tap in to all of those experienced guys out there has been fantastic.
Hope this helps someone else out.

[paris1]

These tires (sorry-tyres) are going to feel a whole lot different (probably better) in a thousand miles or so after they're "scrubbed in". So don't get overly excited about how they feel the day after installation. However, you made the right decision getting rid of the RFs. Just about anything is better!

[Marcoose]

Medic, I highly recommend a tyre plug kit. I carry two; round plugs and funny shape plugs. And a pump. Enjoy the ride.

[proboner]

Originally Posted by Marcoose

Hey, I'm in San Francisco. Hi!

On my first proper ride, in the Foothills, even wifey, as a passenger, complained the car was understeering. And it was. Badly. So the local indy did the mods in the sig, plus -5 degrees front camber. Boom. The car turns just by thinking of turning. A++.

But, yeah, the ride is very hard now. You think the airbags will pop with every bump.

Yup, I ran H&Rs. I'd highly recommend switching to Eibach springs if you want some comfort back.

[Marcoose]

Originally Posted by proboner

Yup, I ran H&Rs. I'd highly recommend switching to Eibach springs if you want some comfort back.

Thanks. I will certainly ask the indy. Presently, the setting is great for performance driving, but comfort is nil. I have to give my wife a boob message every night!

[proboner]

Originally Posted by Marcoose

Thanks. I will certainly ask the indy. Presently, the setting is great for performance driving, but comfort is nil. I have to give my wife a boob message every night!

I mean that sounds like more than enough reason to keep it how it is!

[Meonstoke]

Originally Posted by Medicman1972

Hi everyone IÂ’m a newbie so be gentle!😄
IÂ’ve just got a 2011 Z4 35is. With 31,000 miles on it. Generally really happy with the car but I have a problem..
When driving the car in a straight line on a smooth road, the ride is firm but bearable. If I corner either left or right and go over a bump at the same time (even a small one) the car jolts.. similar to a scuttle shake type thing, it really spoils the ride.

IÂ’m running the following setup which I believe is standard for the 35is:
Rear-255/30 R19 Bridgestone Run flats (RFT)
Front-225/35 R 19 Bridgestone run flats
Both on standard rims, all pressures checked and correct. No defects in tyres. Lots of tread left.
The car has not been modified in any way..yet🤣
How can I improve the ride without selling a kidney to pay for it?😀

If I switched to Michelin pilot sport 4s tyres (£750 or 1300 USD for four) how much will it improve the handling/comfort if any?And can they be fitted to standard rims that previously had RFT on them?
I will spend the money if it improves things..
I realise that 19” wheels on any car isnÂ’t going to give the best of rides but this is shaking the fillings out of my teeth!😃
IÂ’m also considering getting four wheel alignment done as well.
Thanks for any advice you can give

Hi,
I’m in the same boat (or will be hopefully very soon) as Medicman1972 was - see above. The E89 that l’m certain to purchase has the same 19” wheel rim sizes as quoted above. They are ‘296’ type wheels; also running on RunFlats. These are old and need to be replaced.
The dilemma l face is the following:
* the tyres need replacing for safety reasons (too old)
* 3 of the wheels are kerbed and need renovating foe aesthetic reasons
* despite assuming RFTs would be a terrible ride, l was pleasantly surprised by the quality of the ride. Admittedly the roads are smooth where l live
* the dealer advises the RFTs with todayÂ’s technology are much improved c.f. 20 years ago when BMW first introduced them to their models. He recommends sticking with modern RFTs e.g. from Michelin
* the car has standard suspension, not lowered, and has the adaptive suspension option
* my preferences are for a ‘sporty GT’ set-up; looking for comfort but also good handling for the occasional spirited backroad blast. Road use only, no track activities
* lÂ’m aware that reducing the unsprong weight will make a significant difference to handling (and comfort)
* hence, l was considering swapping the 19” 296 wheels for 17” or 18” wheels. Either to smaller 296 variants OR to other BMW wheel variants which are lighter than the 296 type. Any views on this point?

My thoughts are:
* if lÂ’m going to need new tyres (and would like to have undamaged wheels) then no point in further investing in the current 296 wheels on the car
* perhaps better going straight to a completely new wheel-tyre set-up that will fit best to my preferences as described above
* one strategy that came to mind was to perhaps go to BMW 17” wheels which are known to be light (c.f. other 17” options) and pair them with modern RFT’s?
* alternatively, go for 18” BMW wheels (again, as lite as possible) and pair with non-RFTs such as Pilot Sport 4 (or the new Pilot Sport 5)?

Apologises for the long post. I am really interested to hear your thoughts / advice on the various possibilities open to me.

Thanks!

M.

[B21]

18” is probably the ‘Goldilocks’ zone ..good ride quality no adverse effect on handling..

BMW wheels for the E89 are not of any notable quality..so after market options can make life even more complicated ..

If you have a 35i / 35is then maybe 18” after market wheels with slightly wider tyres front and rear..

I’ve tried 7 sets of alloys and 12 sets of tyres so plenty of options..

Not aware of anyone fitting latter day RFs and reviews on E89s..

[Meonstoke]

In the last 24 hours, l think l have answered my own question.

It seems the 296 are prone to cracking, and not only on RFTs.

Examining the OEM wheel options for the E89, l’ve come down on the side of 276 type wheels as a replacement. I only have to consider whether l go for 17 inch or 18 inch. Being an older gent, the look of 17 inch look perfectly fine to my eyes, and will be comfortable for sure. It means that front and rear will have the same tyre width size of 225 which is convenient.

But would the 18 inch variant offer significantly better handling? And what is the upside of having 255 rear tyre size when choosing 18 inch? Fitting a wider tyre at the rear will surely increase the road noise c.f. having 225 tyre width both front and rear.

All thoughts welcomed.

M.

[B21]

Your answers here..

[Meonstoke]

Thanks B21! Really useful.

My Conclusion: 18 inch with 225F / 255R i.e. stick to stock setup.