[el lobo 6061]

Originally Posted by Dr.AD

An Eventful Weekend Drive to Karwar (RFT Proves its Worth!)

How much did these new Michelin Primacy 3 ZP RFT 225 50 R 17 cost?

I think, its due to RFT that you suffered this cut since sidewalls are hard. Had it been a normal tubeless, it would have taken the impact than get cut.

Also 225 50 R17 have very good sidewall of 112.5 mm.

You should have changed over to Space Saver tyre post cut since driving 80 Kms on RFT can also damage your alloy wheel.

Problem with RFT is very low life of mere 20,000 kms when you drive BMW like its meant to be.

[Dr.AD]

Originally Posted by el lobo 6061

How much did these new Michelin Primacy 3 ZP RFT 225 50 R 17 cost?

The cost was Rs. 17,800 per tyre.

I think, its due to RFT that you suffered this cut since sidewalls are hard. Had it been a normal tubeless, it would have taken the impact than get cut.

That is not for sure. That is just one theory. In reality, even normal tubeless tyres suffer plenty of damage on such massive potholes, and I know of many cases where normal tubeless tyres suffered similar cut in the sidewall after hitting a pothole at a good speed. In fact, on this road (as well as the "infamous" Tumkur road section near Bangalore), I saw many vehicles broken down after potholes, including taxis, trucks and buses. None of the run RFTs. So no point blaming this on RFTs.

Also 225 50 R17 have very good sidewall of 112.5 mm.

Correct! And that is why RFTs are even more suitable. For such a tall sidewall, normal tubeless tyres could be a bit too soft. RFTs give the F30 a much better handling that what normal tubeless would give. That is also a major advantage of RFTs specifically on F30 with R17 wheels.

You should have changed over to Space Saver tyre post cut since driving 80 Kms on RFT can also damage your alloy wheel.

Not sure if this is true. This would beat the whole purpose of RFTs. BMW manuals mention one can drive for a 100km or so on the RFT with zero pressure. And that is precisely what I did. And yes, I did check the alloy wheel thoroughly when putting new tyres after I returned back. There was no issue with the wheels.

Problem with RFT is very low life of mere 20,000 kms when you drive BMW like its meant to be.

Again, I would disagree. I drive the BMW the way it is meant to be, and even more, and even after that. my first set of RFTs lasted for 35,000km and the second set lasted 38,000km. I know of my friends driving F30 who also got similar lives on their RFTs. So it is not necessarily true that yoy get very low life. And my friends also drive the BMW pretty hard, the way it is meant to be driven!

[VineetG]

Originally Posted by Dr.AD

Again, I would disagree. I drive the BMW the way it is meant to be, and even more, and even after that. my first set of RFTs lasted for 35,000km and the second set lasted 38,000km. I know of my friends driving F30 who also got similar lives on their RFTs. So it is not necessarily true that yoy get very low life. And my friends also drive the BMW pretty hard, the way it is meant to be driven!

I agree. My RFTs were changed at 45000 kms, and still had about 5000kms worth of tread left, but i chose to replace them considering high speed highway driving in the rainy season.

Got non rft Continentals for 10K each, inclusive of wheel alignment and balancing.

rgds

Vineet

[itwasntme]

Originally Posted by Dr.AD

The specified pressure is indeed 420 kPa or 60 psi

Hi Dr. AD, all is well that ends well .

However, I feel you were lucky in not blowing out your Space Saver Tyre (SST) by running it for such a long distance and that too at 36 PSI!

It is very much 60 PSI for both storage and usage. You potentially managed it because you were alone in the car and hence very lightly loaded. Had you had a full complement of passengers and luggage, you would have really overburdened the underinflated SST, be it at 60 km/hr or 80. Technically speaking, do also keep in mind you will have to replace the SST now.
Related threads:
https://www.team-bhp.com/forum/techn...d-go-flat.html (Run Flats could go Flat)
https://www.team-bhp.com/forum/tyre-...-solution.html (Pics: BMW's incredibly stupid spare tyre solution)

[Dr.AD]

Originally Posted by itwasntme

However, I feel you were lucky in not blowing out your Space Saver Tyre (SST) by running it for such a long distance and that too at 36 PSI!

Yes, I agree with you. Running the space saver on 36 psi was a mistake, and I realized it now. Luckily for me the car very lightly loaded (I was alone and practically had no luggage other than a small bag for just one-night stay) and got away with this mistake.

It is very much 60 PSI for both storage and usage. You potentially managed it because you were alone in the car and hence very lightly loaded.

Thanks for the confirmation on the running pressure.

Technically speaking, do also keep in mind you will have to replace the SST now.

Really? When I inspected the SST at the end of all this drama (while installing new tyres), it looked just like how it was at the start of the journey. It has not taken any beating and has no visible damage or wear at all. I did not realize the SST has such a short life of 600km. I will double check this and replace the SST if required.

Related threads:

Thanks. Yes, I have read those thread. However, most of the objections to RFTs on such (mostly older) threads are these: 1. They wear out too fast, and 2. Not having space saver is dangerous and stupid.

For me, my experience shows that 1. is not true in my case. I get very good life on RFTs. and 2. is not applicable too because I always carry a space saver (and I agree with point 2 anyways).

Thus, from my own experience, RFTs are actually quite good if used along with a space saver tyre. The very fact that I can drive to the nearest town and do not have to change the wheel on the spot all by myself in the middle of a forest (I do plenty of solo drives) is the most important argument in favor of RFTs, at least for my use case.

[itwasntme]

Originally Posted by Dr.AD

Thanks for the confirmation on the running pressure.

I will double check this and replace the SST if required.

The very fact that I can drive to the nearest town and do not have to change the wheel on the spot all by myself in the middle of a forest (I do plenty of solo drives) is the most important argument in favor of RFTs, at least for my use case.

Sounds good! Agree, RFTs have improved by leaps and bounds.

Unfortunately in India, BMW provides the G20 M Sport with Michelin Pilot Sport 4ZP (18" RFT), but beggars the G20 Sport with Bridgestone Turanza T005s (17" RFT). I've more or less finished off the latter at ~25K km.

As a replacement, while the Michelin Pilot Sport 3ZP (RFT) looks great at ~18K INR, so does the Michelin Pilot Sport 4 (tubeless) at ~12.5K INR.

[Dr.AD]

Originally Posted by itwasntme

As a replacement, while the Michelin Pilot Sport 3ZP (RFT) looks great at ~18K INR, so does the Michelin Pilot Sport 4 (tubeless) at ~12.5K INR.

Agreed. However, just a minor correction. These are NOT Michelin Pilot Sport 3ZP. I have not seen those available anywhere. What I have, and what is available in the market is Michelin Primacy 3 ZP (P3 ZP). These are (unfortunately) more comfort oriented than outright performance oriented series (that Pilot Sport is).

These are the RFT equivalent of the Micheline Primacy 3 ST (P3 ST) tyres that were so popular among sedan owners sometime ago. I still have those on my old SX4. However, thanks to the RFT version, which is a bit stiffer be definition, I found these P3ZP = P3 + RFT combo to be ideal for my ride and handling needs. These are great for long highway drives, and when the road gets rough, they provide quite a comfortable ride too.

On the other hand, the Pilot Sport 4 (non ZP version) which is available at about Rs. 12.5K is an outright performance oriented tyre. That will definitely offer a lot more grip than the P3 ZP tyres for sure. And as a bonus, it is a lot cheaper than P3 ZP (there is a good saving for a set of 4 tyres).

Before this incidence happened to me, I was actually considering if I should (like many other 3 series owners) ditch the RFTs and just get the Michelin PS4 and both enjoy more grip levels and save some money too. However, this incidence just before the tyre change sort of reinforced the usefulness of RFTs for my kind of driving, and then any thought of ditching the RFTs vanished. The peace of mind I get while driving with RFT + Space Saver Tyre is now invaluable to me.

[ritedhawan]

Insightful read. I have no experience of RFT's and this update is helpful. However, I have a few questions, but before I state those questions. Kindly confirm whether its a RFT or a normal tubeless tire , a car driven with a deflated FR tire should pull the steering wheel in its direction, the rim holding the deflated tire would start getting hot, the engine needs to rev up in order to overcome the drag associated with a deflated tire, thus begging these questions:

(1) Did the steering pull in the direction of the RF (Right Front) tire and you had to pull it in opposite direction to keep the car steady during the course of drive while RFT's were being used? ( if the answer is yes, what is the consequence?)

(2) The moment the tire got deflated to the point when it was replaced with a space saver, was the rim was too hot and you had to wait before replacing it with a space saver? How long you had to wait?

(3) The engine needs to rev up in order to overcome the drag associated with the deflated tire and if brakes are used then every single brake point would have an effect on the wear of brake pads of that specific tire. Is that what happened in your case : That there was excessive brake pad wear of that specific tire compared to rest?

The above needs to be taken into consideration for the journey from the moment the tire got deflated to the point the saved saver was installed.

Nevertheless, I had faced a similar situation in the year 2010 even though the car and tire type were different. I was driving my brother Hyundai Verna 1.5 and on way out of New Delhi, I took an off beat road which has next to nothing when it comes to traffic and the scenic beauty was the added advantage. It was not the first time I was driving on this road. I was in the habit of driving above 100+ on this road. I could see ahead that a portion of the road was uneven , the tarmac was adequate but the surface was uneven. The left portion of the road was uneven and the right was alright. Obviously I tried to keep the car on the even surface but it would incur driving the LF and LR tire on uneven surface. I overlooked the depth of the uneven surface and the car flew for a second or two , when it hit the ground, three tires got deflated instantly : the LF, LR, RF and the one that got saved with the RR tire. I pulled over and replaced the RF tire and ambled along on first gear to the next local puncture shop! The car rev'd in first gear in order to overcome the drag and I had to keep the steering wheel from pulling to the left as the left side of the car had two deflated tires and the right had two intact!

[Dr.AD]

Originally Posted by ritedhawan

Kindly confirm whether its a RFT or a normal tubeless tire , a car driven with a deflated FR tire should pull the steering wheel in its direction, the rim holding the deflated tire would start getting hot, the engine needs to rev up in order to overcome the drag associated with a deflated tire, thus begging these questions:

I think you are confused between issues with running normal tubeless tyre at zero pressure and running RFT under similar situation.

The whole point of RFTs is that they are able to support the vehicle load (at slow speeds and for limited distance) with zero air pressure, and without losing any vehicle controls or any safety system. RFTs properly support the wheel and the vehicle with zero pressure so that none of the issues you mentioned happen.

No, there was no pulling to any one side at all. The steering behaved perfectly! No, there was no excessive brake pad wear or any braking issues. The brakes worked normally and perfectly! In fact, BMW manuals clearly say that all vehicle controls, all safety systems including ABS and vehicle stability controls work perfectly well even with zero pressure in RFTs. Again, that is the whole point of RFTs that you can drive the vehicle without any safety issues at all (again, at slow speeds and for limited distance).

Running a normal tubeless tyre (non-RFT) at zero pressure is NOT recommended at all, and that should never be done.

[ritedhawan]

The whole point of RFTs is that they are able to support the vehicle load (at slow speeds and for limited distance) with zero air pressure, and without losing any vehicle controls or any safety system. RFTs properly support the wheel and the vehicle with zero pressure so that none of the issues you mentioned happen

The above pretty much puts my apprehensions about RFT's to rest. If what you stated is true, then RFT's are definitely worth its salt.

[viXit]

A question for you doc.

You mentioned that the TPMS shows 0.0 psi when the RFT blows.
Is this a relative measure of air pressure over atmospheric pressure ? or an absolute?

Doubt because, the absolute air pressure at mean sea level is 14 .7 psi right?

[InControl]

RFT's saved the day!

I hope you kept one of the RFT tyre's being replaced as a backup(the one in better condition relatively) for your future highway drives when your boot isn't packed full. This way you will have a RFT as a stepney apart from(or instead of) the space saver. You can also keep it in a nice tyre cover so that it doesn't look ugly sitting in the boot or sully other stuff kept there.

Space saver helps in an emergency but with an RFT you will not have to worry at all.

[vjbox]

Originally Posted by Dr.AD

In all my ownership years of the car, I have been reading about similar tyre blowouts in other BMWs, and was part of many discussions about pros and cons of RFTs in such situation. Luckily, until now I never had this experience, and was merely a theoretical participant in such discussions. Finally, this time, it was my turn to have the tyre blowout that I have discussed numerous times in many groups.

Wow, your experience is very similar to mine that I had encountered recently with my V40 CC when returning to Chennai. We were doing some good speeds on the usual GST Road at night, super smooth roads mostly and out of no where we hit a nasty pot hole that we didn't even get to see as we were tailing another V40 CC ahead (tell me about the coincidence right?). Lucky for him he managed to dodge the pothole, we had zero reaction time and we hit the pothole at a good triple digit speed. We hear a nasty thud on the front left wheel and the next second I managed to pull over to the left as I immediately sensed vibrations due to the blown out tyre. It was remarkable as to how poised the car remained despite a tear at those speeds, no drama whatsoever and I was able to bring the car to a graceful stop. Incredible sense of safety that the car reassured to us.

Although it was scary as we had to pull over at a speeding section at night. We have had many pothole drive throughs in the past but this time around, just like how you narrated, it was our turn to face it. The alloy was clearly bent and we had to switch to the space saver with the help of a local. That 45 minutes stop was scary as I had to move my family aside, place the warning triangle on the side of the road and make sure it was seen on top of the hazard lights. Luckily I had my friend with me who got hold of a local and we managed to change the tyre and got out of that place. Drove back at a speed no greater than 60 or 70 KMPH for a good 120+ KMS. I wasn't as fortunate in getting the tyres as 225/45/18s are extremely difficult to get hold of (25k a tyre, ouch!).

In the mean while I had to face an episode with the Volvo Service as they messed up the alloy wheel claim and delayed the tyre procurement as I exhausted all options from the market. I eventually had to get the wheel repaired after getting the new set of tyres ( had to replace all 4 as they are were nearing their end of life). Got the 50K service done and the service centre reported an unusual pull to the right from their road test. They then diagnosed the issue to be the faulty steering rack ( mostly the ball joint) but they decided to change it under Extended Warranty.

Now I have decided to down grade to 17 inchers once this new set of tyres wear out for two clear reasons. One, this tyre spec is hard to get and two, the 18 inchers are more vulnerable to damage due to pot holes.

And lucky you! Your Alloy stayed intact and didn't bend or crack. Perhaps the angle of attack helped it?

[ajayc123]

Slightly off topic, but I am wondering who should be thanked for boosting the automobile industry due to higher wear and tear attributed to bad roads, and more specifically, boosting the tyre industry due to the potholes.

Are there other countries in the world famous for bad roads and potholes?

[Dr.AD]

Originally Posted by ritedhawan

The above pretty much puts my apprehensions about RFT's to rest. If what you stated is true, then RFT's are definitely worth its salt.

Yes, what I said is true. That is the whole point of RFTs. Just in case you are still unsure, see these snippets from BMW manuals (originally posted by @RSUDARSANAN in here: https://www.team-bhp.com/forum/tyre-...ml#post3988707 (Pics: BMW's incredibly stupid spare tyre solution))



And see the red highlighted box (highlighting mine) about safety electronics and RFTs:


This is why RFTs are so useful.

Originally Posted by viXit

You mentioned that the TPMS shows 0.0 psi when the RFT blows.
Is this a relative measure of air pressure over atmospheric pressure ? or an absolute?

Doubt because, the absolute air pressure at mean sea level is 14 .7 psi right?

TPMS (just like any other tyre pressure gauge) measures relative pressure difference between the tyre pressure and atmospheric pressure. This is because when your tyre has absolutely no pressurized air inside, it still has the atmospheric air (it is not a vacuum) and that will be the reference measurement for further pressurization. You are right that at that point the absolute pressure is 14.7 psi, assuming we are at sea level. But the TPMS as well as any other tyre pressure gauge is calibrated to read 0.0 at that time.

Since it is a relative pressure measurement (with respect to atmospheric pressure) and not absolute, the moment tyre loses all air, the TPMS will show 0.0 psi (as will any other pressure gauge) and not 14.7 psi.

By the same logic, when we say tyre pressure is 32 psi, as an example, and when TPMS or any tyre pressure gauge shows 32 psi, the absolute pressure in the tyre, at sea level, will be 32 + 14.7 = 46.7 psi.

Hope this answers your question.

Originally Posted by InControl

I hope you kept one of the RFT tyre's being replaced as a backup(the one in better condition relatively) for your future highway drives when your boot isn't packed full.
Space saver helps in an emergency but with an RFT you will not have to worry at all.

No, I did not keep it. Your thought is valid, but practically it is just not feasible, for at least three reasons: 1. The full size tyre will need to be mounted on a full size wheel (not the donut wheel), and that combo will eat up almost the entire boot space. After that, there is no place in the boot even for a small bag. 2. Without full size spare alloy (which I don't have anyways), the empty RFT is useless. It is not easy to mount and unmount RFTs on wheels. That requires special tools. Therefore, it is not possible to unmount the damaged RFT from the alloy wheel and put the spare RFT there, especially on the side of the road. 3. And anyways, even without the spare full size wheel the RFT by itself will eat up enough boot space to make it not a practical solution.

Therefore, I discarded the old RFTs and simply put the space saver tyre back in the boot. Even that eats away almost half of the boot space, but that is something I have learnt to live with now.

Originally Posted by vjbox

I wasn't as fortunate in getting the tyres as 225/45/18s are extremely difficult to get hold of (25k a tyre, ouch!).

That is a scary incidence for sure. Glad everything went well and you were fine. I agree with you that it is quite difficult to find these sizes in any smaller towns. Even for me, finding a 225/50/R17 size RFT in any town other than the major metros is almost impossible. So buying a new tyre somewhere on the road or in the smaller town is just not going to work.

And lucky you! Your Alloy stayed intact and didn't bend or crack. Perhaps the angle of attack helped it?

Yes, luckily for me, the alloy wheel was fine.

I checked complete underbody, suspensions etc in addition to all alloy wheels, and luckily, everything is fine!