Change run-flats to standard tyres?

flyingscotno1

jase1 wrote: »

Is there any reason why the OP didn't realise that the tyres were £1150 to replace before he bought the car?

Looking at tyre cost isn't what most people do when looking at cars. They just assume cost will be usual £50-80 for a tyre.

I'm lucky, I never checked but my car has a normal size (205/55/16) which is in stock and cheap. Many manufacturers are getting 'big wheel obsessed' which is a large price if there is a puncture.

At work someone got a puncture in a Peugeot- unfortunately it takes wide low profile tyres with a high speed rating which are £100 a corner for the cheapest in stock. Why does a Peugeot estate need such high spec tyres?

colino

Hopefully as the tyres are now almost completely across the range and Merc are following suit, the prices will come down, but only to "normal" BMW prices where any decent tyre hovers around £100 per (17") corner.
Comparing like with like, the 5 series, converted to ordinary tyres is both softer (but just as agile) and quieter that it was on the run flats.

Honkycat

I've had a new 5 series for a year now and in that time have had 3 RFT replacements....3!!! Before that I can't remember having a flat tyre in the previous 10-15 years. Just bad luck?

jaydeeuk1

This is what is scary with all these cheap BMWs and other premium brands flooding the market. People see the badge and cheap price without researching the running costs, and then try and skimp on one of the most important aspects. Not saying this is what the OP has done, but price of tyres is one the many things I'd check on before buying a car, like insurance, fuel costs, servicing etc...

sunshinetours

BAA1 wrote: »

In your opinion ... there is no "of course" about it
Since BMW cars have been designed and set-up to use Run Flat Tyres which have different operating characteristics to none run flats.

So in my opinion ... I stick with my earlier comment :

In mine and many BMW knowledgeable people I should clarify then. You are of course entitled to sticj with yoru own opinion. Others ahev since covered this it seems but plenty of info on specialist BMW forums like bmwland.

Did have to chuckle at the "individual suspension set up". They are nice cars but they aren't hand made Morgans!

BMW cowtailing to the US market caused these ROF things to become standard fit across the range and they are in general a complete compromise on all accounts

And yes they are generally very expensive in 17" or larger sizes

GolfBravo

reeac wrote: »

... My point is that there was never any mystique about "specially tuned suspension" etc. I never noticed any difference in the handling.

Yes, car suspension is specifically tuned for each model (different engine size may have different suspension components, different brake discs and pods, etc.). And when I say tuned, I don't mean completely redesigned suspension, I mean there may be different specification components used. It is also about tolerances, so BMW 318 and 320 may share the same suspension (simply because they are very similar in weight) however 335 will have a different suspension characteristics due to extra weight.

Nearly_Old wrote: »

... So key suspension components are individually designed?

You forgot two other key components: springs and shock absorbers. Each manufacturer has plenty to choose from their parts bin, and before a new model is released there would be hundreds of different suspension setups tested.

There are two issues with RFTs: side wall stiffness and unsprung mass. These two are key suspension functions that need to be accounted for when tuning a suspension. RFTs have significantly stiffer side walls (producing firmer ride) and significantly more mass (requiring beefier shock absorbers). No suspension engineer would sign off a suspension design without taking into account RFTs characteristics - the difference between standard tyres and RFTs is huge.

And the fact is that from 2005 all BMW models are designed for RFTs. Are they any better? Probably not (why would you want more unsprung weight anyway?). And BMW take kickbacks from tyre manufacturers for their "BMW approved star marked tyres", so no wonder they are pushing this technology.

By all means feel free to fit standard tyres to any BMW, but make sure you know what you are doing. You may have to use reinforced tyres and definitely run them at a higher pressure than what's indicated on a tyre placard.

Nearly_Old

GolfBravo wrote: »

It is also about tolerances, so BMW 318 and 320 may share the same suspension (simply because they are very similar in weight) however 335 will have a different suspension characteristics due to extra weight.

You forgot two other key components: springs and shock absorbers. Each manufacturer has plenty to choose from their parts bin, and before a new model is released there would be hundreds of different suspension setups tested.

By all means feel free to fit standard tyres to any BMW, but make sure you know what you are doing. You may have to use reinforced tyres and definitely run them at a higher pressure than what's indicated on a tyre placard.

As far as the shock absorbers then they are fairly standard across all the models in any particular range; e.g. the the E90 3 Series with a production date of Jan07:
The 4 cylinder engines have different front shock absorbers to the 6 cylinder engines but all models from the 316 to 335 have the same rear shock absorbers. Yes they may try hundreds of combinations and therefore the end result is a compromise - generally for the American market.

As for tyre pressures they can vary greatly between different tyres even of the same type. I've got 2 sets of wheels for the Z3 and the Goodyear Eagle F1's are best at 31Fr 33Rr whilst the Falken 912's are better at 32Fr 35Rr.

Non of the high performance models; e.g. the BMW M Series are fitted with run flat tyres as their performance at the limit is not as good as non run flat tyres.

My view is that run flat tyres are being used to allow a small weight reduction (no spare wheel, etc) and to make life easier for American consumers who dominate the market. Fleet managers (or more likely the lease companies) are now getting cars from BMW (and others) with normal tyres but the private buyer still gets the run flats. If there was any safety issues then BMW would not be supplying cars with normal tyres instead of run flat tyres as the risk would be too great.

Tyre manufacturers appear to have jumped on the bandwagon as the cost of run flat tyres has increased at a greater rate than normal tyres which is why the OP is asking if fitting normal tyres is now an option.

andygb

BAA1 wrote: »

A company like BMW spend millions on car development and design, which includes suspension set-up in conjunction with wheel / tyre specifications.

BMW have specifications for the type of tyre that can / should be fitted to each model, and also which tyre combination is suitable for each car's suspension characteristics.

But, if you guys think you know more than the BMW designers, then go for it :rotfl:

Oh, and just because a dealer recommends non-run-flat Winter tyres, does not mean that those will be the best match for your car's suspension. The majority of dealer salespeople have little or no technical knowledge, so unless they ask the relevant technician for the correct tyre specifications, I would take what they say with a pinch of salt.
The key is : Only fit tyres that are listed by the manufacturer for your particular car. (So if they do list non-run-flats, use that listed spec of tyre if you wish)

Back in 2000, I bought a 520i which was fitted with run flat tyres. I changed them for a new set of alloys (the originals were metric) with tyres for £600, and then ran the car on non run flats for the next five years and 80K miles (including plenty of high speed work on autobahns). The original manufacturer spec run flats were rubbish, particularly on rural roads. The handling and comfort improved with non run flat tyres. As others have said, go on the BMW forums to get advice, they love the cars and know a thing or two.

Nearly_Old

I've been having a look to see if there is anything official from BMW and came across this:

The following text was published by BMW on babybmw.net, an UK fans forum, in response to a customer’s concerns. I have added some personal comments

Quote:
BMW aims to provide our customers with a premium product that provides ultimate safety with optimum performance and it is always a concern to receive feedback of this nature.
We chose to include Run-flat technology on our vehicles for the following reasons:

• It is dangerous to stop on any road to change a tyre, especially on a motorway or at night. Fair point but you would still probably stop to see which wheel had the puncture.
• There is no need to have to wait for a breakdown service to arrive. Assumes that you can’t change a wheel – USA inspired?
• Safety and security of the driver and passenger(s) is maintained. How? Not sure what this is supposed to mean.
• Alloy wheels are difficult to detach from steel hubs. Not a very good advert for a full BMW service history as they never take the wheels off so yes they will be difficult to remove!
• On most cars the spare is under the contents of the boot, and uses boot space. BMW fit some spare wheels in carriers behind the rear bumper
• It can be tricky to line up the wheel bolt holes with the hub screw holes and match the thread. Do BMW generally sell to people who don’t know the first thing about cars?
• The dirty punctured tyre needs to be removed and stored in the boot. Or in the car as BMW supply a nice bag to put it in.
• Another puncture before the punctured tyre is mended means one is stranded. Not sure that I'd want to drive any car with two punctured tyres.
• A driver can continue for 150 miles at 50mph with a punctured Run-flat tyre. By which time the tyre will be ruined and we will charge you ££££ for a new one.

All of our vehicles that use Run-flat technology have their suspension and braking components set up to accommodate Run-flat tyres. (and other tyres as below) Should you decide to change to non Run-flats, it may (it may actually alter them for the better) alter the driving and handling characteristics of your vehicle. It is for this reason that this modification is not recommended by BMW as a manufacturer.
However, it is possible to have standard tyres fitted (so the suspension is OK for non run flats as well as run flats). You will additionally need to purchase either a spare wheel with jack and brace set or a mobility kit which can be ordered from the Parts Department of your nearest BMW Approved Dealership. Now that we can't charge you ££££ for run flat tyres as there is no reason to keep them on the car we want to sell you other things.
End quote.

I found this here: http:////www.bmwblog.com/2009/03/12/reasons-to-have-run-flat-tires-on-your-bmw/

neilmcl

To balance I've added my comments.

Nearly_Old wrote: »

I've been having a look to see if there is anything official from BMW and came across this:

The following text was published by BMW on babybmw.net, an UK fans forum, in response to a customer’s concerns. I have added some personal comments

Quote:
BMW aims to provide our customers with a premium product that provides ultimate safety with optimum performance and it is always a concern to receive feedback of this nature.
We chose to include Run-flat technology on our vehicles for the following reasons:

• It is dangerous to stop on any road to change a tyre, especially on a motorway or at night. Fair point but you would still probably stop to see which wheel had the puncture. Not really, not until you get to the destination.
• There is no need to have to wait for a breakdown service to arrive. Assumes that you can’t change a wheel – USA inspired? True, but if the alloys are difficult to get off, and I've experienced this myself then you may heve no option.
• Safety and security of the driver and passenger(s) is maintained. How? Not sure what this is supposed to mean. It means you don't have to get out to fix your wheel at the roadside, soemthing most female drivers would prefer no to do.
• Alloy wheels are difficult to detach from steel hubs. Not a very good advert for a full BMW service history as they never take the wheels off so yes they will be difficult to remove! It only takes a good winter with all the salt and carp for the wheels to become stuck onto the hubs.
• On most cars the spare is under the contents of the boot, and uses boot space. BMW fit some spare wheels in carriers behind the rear bumper As standard?? which models?
• It can be tricky to line up the wheel bolt holes with the hub screw holes and match the thread. Do BMW generally sell to people who don’t know the first thing about cars? I'd tend to agree with you on this.
• The dirty punctured tyre needs to be removed and stored in the boot. Or in the car as BMW supply a nice bag to put it in. Then you've got no room for anything else.
• Another puncture before the punctured tyre is mended means one is stranded. Not sure that I'd want to drive any car with two punctured tyres. Maybe not, but it's perfectly safe to do so, no to mention that chances of this is very small.
• A driver can continue for 150 miles at 50mph with a punctured Run-flat tyre. By which time the tyre will be ruined and we will charge you ££££ for a new one. It's not recommended to repair an RFT anyway, I wouldn't do it anyway.

All of our vehicles that use Run-flat technology have their suspension and braking components set up to accommodate Run-flat tyres. (and other tyres as below) Should you decide to change to non Run-flats, it may (it may actually alter them for the better) alter the driving and handling characteristics of your vehicle. It is for this reason that this modification is not recommended by BMW as a manufacturer.
However, it is possible to have standard tyres fitted (so the suspension is OK for non run flats as well as run flats) - only if you take this into account by using reinforced tyres or at the very least increasing tyre pressures.. You will additionally need to purchase either a spare wheel with jack and brace set or a mobility kit which can be ordered from the Parts Department of your nearest BMW Approved Dealership. Now that we can't charge you ££££ for run flat tyres as there is no reason to keep them on the car we want to sell you other things. Other manufacturers charge you for these things as part of the cost of the car.
End quote.

I found this here: http:////www.bmwblog.com/2009/03/12/reasons-to-have-run-flat-tires-on-your-bmw/