[GTO]

Most of you know how I hate runflats. Here's the dilemma - My 530d has low-profile tyres running on large 18" rims. I honestly feel this new trend of big wheels & shorter tyre profiles sucks as it only results in a stiffer ride, tyre damage, wheel damage & expensive replacements, but we'll save that discussion for another day.

My 530d has been out on the highway a dozen times or so in the last year. Inevitably, a couple of deep potholes have been hit (including at high speed).

Here's the thing - Despite the highway running & bad roads, my current Continental ContiSport runflat tyres don't have a single bulge on them. They have taken all the beating that our roads could throw at them. I want to switch over to regular tubeless tyres, but the runflats have survived 25,000 km without any damage / bulging. Is it safe to assume that the stronger sidewall of a runflat tyre makes it more suitable to bad roads? Or is it that a firmer sidewall will flex lesser and bulge easier?

Tubeless tyres are cheaper, ride better and quieter. The first point isn't a problem. While I'd like better ride quality, I'm very happy with the current comfort levels too. No issue with tyre noise either.

My car sees the highway at least once a month, hence my main concern is tyre damage - Do runflats survive bad roads where tubeless tyres fail? Again, keep the low profile size in mind.

Tyre change due soon. Thanks in advance!

[Jaggu]

Originally Posted by GTO

I want to switch over to regular tubeless tyres, but the runflats have survived 25,000 km without any damage / bulging. Is it safe to assume that the stronger sidewall of a runflat tyre makes it more suitable to bad roads? Or is it that a firmer sidewall will flex lesser and bulge easier?

My experience with run flats were only with the office 5, they used to last 20-25k with indian roads, mix of city and highway. One or two punctures also happened in first set. But they never damaged the alloy or got any bulges. So i derive the stiffer side wall helps.

Where as a better ride from normal tubeless means rubber is cushioning, which means its lesser stress on suspension BUT chances are the potholes will reach the wheel rims more.

Tubeless tyres are cheaper, ride better and quieter. The first point isn't a problem. While I'd like better ride quality, I'm very happy with the current comfort levels too. No issue with tyre noise either.

And if you cover the tyres in that insurance thingy, there is no reason that comes to my mind to change.

My car sees the highway at least once a month, hence my main concern is tyre damage - Do runflats survive bad roads where tubeless tyres fail? Again, keep the low profile size in mind.

Like i mentioned before, apart from few nails that resulted in puncture no serious issues during the usable life.

[arunphilip]

Originally Posted by GTO

Is it safe to assume that the stronger sidewall of a runflat tyre makes it more suitable to bad roads? Or is it that a firmer sidewall will flex lesser and bulge easier?

I personally suspect both would apply - the stronger sidewall allows it to take a beating, but when it has reached a point of failure, it will fail more severely.

Remember that old story about a tree trunk that didn't sway in the wind, but maize leaves which used to get flattened in even a light gust, and then spring back? When a heavy wind came, the tree stood for a while and was properly uprooted while the maize was unaffected.

OK, moving away from folk tales , taking an automotive corollary - firm suspensions. Firm suspensions are what make a lot of us get excited due to it offering better control, but if a suspension is too firm, then it cannot respond to varying conditions (e.g. a high kerb on a race track). It needs a balance of "enough, but not too much".

[Akshay1234]

I think because of the thicker sidewall, the runflats definitely are a bit more resistant to bulging. Arunphilip has put it across very well

But I have also seen the opposite, runflats getting sidewall tears a lot, possibly again due to what Arunphilip has explained above.

In your cars tyre size, you would only get high performance tyres which would in any case have tougher sidewalls than regular tyres. I think its worth trying it out. A really bad bump or pothole will most probably put a tyre out of action be it a runflat or a regular tubeless.

Another thing you may notice is that the turn in will be slightly less sharp than with runflats, but the overall grip will be more.

[karan561]

GTO,

I think you have been lucky, but not only luck you also know the repercussions of facing a side wall crack / bulge and hence have been a careful driver. Also couple of potholes in 25k kms life is excellent driving IMO. Usual careless drivers would be hitting couple of potholes everyday.

For them the runflats wont last much, specially the low profile ones.

Another friend & BHPian Manish (bhp) is a runflat fan who has an X1 and a F30 20d, until he changed his X1 tyres to tubeless Michelins & his car transformed. But he had 55 profiles in both & not a low profile so that would have helped him out. Just like F10 17" size being 225/55 R17 havent seen that size being a problem with Runflats.

New generation of Runflats are definitely good but for low profile they being better than tubeless when it comes to toughness i'd say no.

My OE fitment tyres were Good Year RFT's in the 328i & definitely did not perform well on the toughness part, may be Continentals are better in making RunFlats.

Also the biggest disadvantage of Runflats are that they are HEAVY. Do note the ///M Cars from the BMW stable dont use Runflats

For reference even after switching to a larger size tubeless tyres i was able to save a total of aprox 16 lbs (7.25 Kgs). Thats a substantial saving considering they are unspring weight which means lower the unspring weight the less work the shocks and springs have to do to keep the tires in contact with the road over bumpy surfaces. Hence making tubeless tyres perform better than Runflats

[Santoshbhat]

One thing I am quite certain is that run flats are safer than regular tubeless in tyre blowout scenarios. The reinforced sidewalls will be able to carry the weight of the car and allow you to steer and stop the car safely.

Modern runflats are much improved when it comes to ride quality. My BMW X3 rides exceptionally well despite running on RFTs. Only sharp ruts catch it out at slower speeds and the front axle thuds through. Surprisingly the rear wheels absorb the impact much better. Maybe its the adaptive suspension at work?

RFTs may not be prone to bulging as much as they are prone to shredding. I'd say if you are not perturbed by the ride quality, stick with RFTs. BMW engineers designed their cars with RFTs. Change it only if there is a compelling reason for change.

[Cyborg]

Originally Posted by GTO

Tubeless tyres are cheaper, ride better and quieter. The first point isn't a problem. While I'd like better ride quality, I'm very happy with the current comfort levels too. No issue with tyre noise either.

GTO, Since you are happy with the RFT's and they do give you the added peace of mind to simply continue driving, why change?

Hope it never happens, but, if you have a puncture at night or say in a place you would rather not stop, it would be so much safer to have the RFT's. You have the best of both worlds, do continue with it.

Cheers

[coolboy007]

Run flats are way harder than tubeless tyres and there are no two ways about it, when it is time to change tyres in my 3 series, am definitely going to go the tubeless way. The 3rd gen rft's + bmw's softening of suspension in all its cars does lay in a very good low speed ride quality but still hit a deep pothole at any thing more than 30-40, you do get a loud thud and that is mostly down to the super hard sidewalls of run flat tyres.

I was going through BMW India's facebook posts and many owners keep crying there and curse bmw for opting to use run flat tyres as they have a tendency to get a sidewall bluge/cut very soon. We do need to have a nice balance in sidewall stiffness just like super soft/super hard suspension set ups are not feasible in our conditions. Most BMW owners i have spoken to have been extremely happy after switching to tubeless and no one has anything good to say about run flats.

I personally feel that more than tubeless v/s rft for tyre damage, it is more down to the sidewall profile you have in your car. My car has 225/55 R16 which gives a sidewall height of 123 mm which is quite a lot for a sports sedan. Your 530D must be having 275/40 which is too low profile and banging hard some where may present you with an expensive tyre bill.

I suggest you go with tubeless tyres, they are much more comfortable (any extra comfort over our poor roads would be appreciated), they are much less noisier, they don't tramline like rft's, owing to the ultra stiff sidewalls the rft's start squealing way to early during hard cornering,they are much cheaper and they are way lighter than RFT's. As Karan said, there is a reason why M cars do not have run flats, unsprung mass is a big enemy of both handling and performance.

Yes, the rft's are safe during high speed tyre bursts but you won't be doing 200 on public roads, the advantages of tubeless tyres overcome the single disadvantage it has.

[Mpower]

I would say make the switch and you will not regret it

Road surfaces quality on Indian National highways have improved vastly over the years. Nothing like what it was 10 years ago

Now, small highways and mofussiil areas are a totally different ball game. So just think about where you will be taking an expensive car like the 530D

Secondly, there are cases of a run flat experiencing side wall cut or failure (not necessarily from a bump) in which case you are totally stranded because you have no spare and the tire cannot 'run' with a 'flat'

In case you have a typical flat (nail pierce with air leak), a run-flat will let you drive only X-miles (which may not work for you if you are in the middle of nowhere)

I know you are happy with your ride, but I when I drove your car, I did find secondary ride a little 'busy' and this is indicative of a stiff sidewall. Also found steering light at high speeds in the wet (mild hydroplaning)

Originally Posted by GTO

Here's the thing - Despite the highway running & bad roads, my current Continental ContiSport runflat tyres don't have a single bulge on them. They have taken all the beating that our roads could throw at them. I want to switch over to regular tubeless tyres, but the runflats have survived 25,000 km without any damage / bulging. Is it safe to assume that the stronger sidewall of a runflat tyre makes it more suitable to bad roads? Or is it that a firmer sidewall will flex lesser and bulge easier?

The bulging happens because the internal belts/cords in the reinforcement 'tear' locally at one point and the air pressure pushes the rubber out locally

Stronger sidewall makes it less suitable due to a loss in cushioning effect. But durability wise, it may be better butt....there are regular tires that can match the durability AND give you better ride quality

Originally Posted by GTO

Tubeless tyres are cheaper, ride better and quieter.

They also have significantly longer life

Originally Posted by GTO

My car sees the highway at least once a month, hence my main concern is tyre damage - Do runflats survive bad roads where tubeless tyres fail? Again, keep the low profile size in mind.

Around Bangalore, I found the highways were better than city roads (only difference being you hit a pothole at very low speed in the city environment)

In summary, I would support the move to regular tubeless.

Not all tubeless tires are the same. Some have tougher (doesn't mean stiffer) sidewalls and others dont. The ones that are not tough are prone to bulging. So do your research

Going to tubeless will also open up your choices to at least 10-12 different brands/models which you wont have in a RFT

Given that you go so much rain during monsoons, you should look for a summer tire that has good wet weather performance

[Durango Dude]

I think the best would be to down size those rims and add some high profile tyres in the interests of improvement in ride quality, sure those 18" rims and low profile RFT will look terrific but our roads would definitely take it's toll in the form of rim, tyre damage and suspension damage.

[karan561]

Originally Posted by Mpower

Secondly, there are cases of a run flat experiencing side wall cut or failure (not necessarily from a bump)

+1

Another way you may be able to damage the Runflat would be if you approach an flyover at a very high speed and because of experiencing an sudden incline the Runflat may get pinched resulting in a bulge or a cut too.

That's how one of the tyres of my 328i had got damaged, worse thing was that i wasn't even driving that time as my friend was at the wheel

[jalajprakash]

The only reasonable explanation I know for having RFTs is the one BMW provides in their sales presentation. God forbid, if your car gets punctured while you are driving it on the highway, would you rather get down and swap out the spare tire or (considering middle of nowhere) drive to the closest fuel pump which has a tire puncture person who can repair the car for you?

The real reason I feel that BMW provides RFTs are that if the owner is himself driving, they wouldn't want the owner to get out and change to the spare tire (it could be middle of the night or a scorching afternoon or in the middle of traffic jam), rather have them drive to the closest resource where they can have the luxury of having someone repair the tire for them which should allow the tire to be used normally again.

If you are okay with swapping a tire yourself, tubeless tires are the way to go. If you do not wish to take that responsibility it would be better to stick to RFTs. For example, in my self-driven car I might make that trade for a better ride but if my dad was also going to drive the car sometimes, I would stick to RFTs since I wouldn't want to put him through changing a tire in the middle of the road or at least get stranded until help arrives.

Disclaimer : Have spent the last few days at the BMW showroom and "Why RFT?" was a question I posed to them also quoting many complaints from BHPian owners about the harsh ride quality of RFTs. Their explanation does seem reasonable to me though.

[asterix]

I reckon RFTs are tougher than tubeless and can take bad roads better. I have done 42k kms on my X5 and never had any tyre issue except for punctures due to nails. Driving was on a mix of city and highway both state and national.

I recently noticed that the ride quality with RFTs improves if the air pressure is a notch lower than the recommendation..in the X5, the recommended pressures are 29 and 31 psi for front and rear respectively and if I set it at 28 and 30 there is a noticeable improvement in ride quality. Is the lower pressure allowing better flexure?...curious to know if anyone else has experienced this?

[Mpower]

Here's an example of a spider chart. Every tire is designed to favour one attribute while sacrificing another. You have to find one that suits your preference and usage.

Red one shown in the pic is a good option for you (although the blue has better ride)

[keroo1099]

Originally Posted by GTO

Most of you know how I hate runflats.

So does Alpina. They ditch the runflats in favor of high performance tyres on all their models so I assume they feel tubeless is superior, and most reviewers agree. The caveat though is that the roads most of these cars run on are billiard table smooth compared to ours.

The issue with going tubeless is what happens when you have a puncture; carry a spare (eats up boot space), or survive on a puncture kit/pump.

http://www.torquenews.com/1083/we-pu...-you-need-know