[T20najam]

After scouring the forum to gain some insights, I still hard hit with what to do and as much as there are posts with this subject...they tend to go off topic so maybe we need a fresh post!

Currently running on 20 inch 624m wheels on 225 35 and 255 30.
I really HAVE to change away from runflats due to the harsh road noise so I am set on this decision completely.

Forking our for 4 new tyres is most definetly not cheap and as much I would want the most expensive non-rft’s, I can’t warrant around £1k. I haven’t got a budget as such and yes I understand tyres are important blah blah blah but maybe some alternatives to the higher priced Pirelli’s etc. Maybe in between the £500-1000 for a full set.

I’d seen good reviews on the Falken Azenis FK510 and after some digging I can source a new set for a smidge over £500.

Any experiences and would be great to keep things ON TOPIC in this post

[Sasquartch]

Before you spend lots of money are you sure non-RFTs will be much quieter ?

20 inch wheels will always be extremely harsh in that respect whatever tyre you have

[T20najam]

Originally Posted by Sasquartch

Before you spend lots of money are you sure non-RFTs will be much quieter ?

20 inch wheels will always be extremely harsh in that respect whatever tyre you have

Lol thanks for making my decision easier(!)
624’s are lightweight wheels, much lighter than the 442’s I had on previously.
I’m looking at the index rating of different tyres and the p-zero’s I have on at the moment have a reading of 72db. For example the Falkens I have just mentioned really stand out as they have a reading of 69db. Also the other 2 ratings (fuel efficiency/rolling resistance and wet grip) are exactly the same as p-zeros.

All in all...I’m going off statistics

[HighlandPete]

Originally Posted by Sasquartch

Before you spend lots of money are you sure non-RFTs will be much quieter ?

20 inch wheels will always be extremely harsh in that respect whatever tyre you have

Add the fact that the tyre label is for "exterior noise emission" in a 'roll by' test. The road noise to the cabin is not always related to the figures quoted. Can depend on how the noise is transmitted, whether airborne or through the suspension/body structure.

Really need experience of other users who have changed to specific tyre and can comment on the difference.

[Sasquartch]

When I replaced my Continentals (at the front only) which were 72dB I think, with Goodyears which were 69dB I can't say I really noticed any difference

As HighlandPete says the rating is not related to cabin noise

[sammoorman]

Hi,
I have exactly the same dilemma right now, I have 624m 20" rims with Pirelli P zero runflats which hardly last and are not worth the money. Looking at fitting either Kumho PS71 or Falken FK510.

Anyone any feedback on either of these?

[SuperHamz]

I found the reviews on here pretty useful:

https://www.tyrereviews.com/Tyre-Siz...5-20-Tyres.htm

https://www.tyrereviews.com/Tyre-Siz...0-20-Tyres.htm

I had a similar problem with Pirellis soft compound on my S2K, the rears were wearing away far too quickly. Opted for Hankook Ventus S12s which were pretty good all round tyres.

Also worth checking for offers on Blackcircles.com or at Costco, tbey regularly have money off and can usually get MP4S. I got a full set of MP4S about 6 weeks ago (albeit for 19" wheels) recent for £540 fully fitted from Costco.

[martin10chk]

You have two concerns it seems - whether more budget tyres are going to perform and what tyres are going to be quieter. Cant help with the second one. My experience has been that big diameter low profile tyres tend to be noisy. I now spec smaller wheels (not tiny but certainly not the biggest possible). For your first concern - I have experience of the Falkens and thought they were very good. Not in any way inferior to premium that I could tell. One giveaway to me is how much balancing is required. Manufacturing tolerance of cheap tyres is sometimes such that they need a pile if weights in order to balance. Falkens were very good on that ‘test’

[Abzynthe]

The only non rft I have on my 624m as the MPS4S tyres so probably not very helpful to you. But, they are a bit quieter I can't really remember quite how much. The ride is noticeably smoother, however it's not smooth smooth, it's still a 20 inch tyre.
One thing I'm thinking about with mine though as that the fronts "look" perfect, but the rears look a little stretched. It's not much, but enough that I'm thinking a 265 would look better.

[Lorcan]

As the OP's car is xDrive they need to be VERY careful about tyre swaps as many brands and models, even in the correct sizes, are not compatible with the xDrive system. Damage to the transfer case is the likely outcome if you use incompatible tyres.

We only recommend Michelin Pilot Sport 4S and Continental SportContact 6 in the standard sizes 225/35/20 and 255/30/20. They do not need to be star rated. AC Schnitzer have tested these and found them to be compatible with xDrive. We recommend the same tyres for RWD cars, but you are free to use others.

[martin10chk]

Originally Posted by Lorcan

As the OP's car is xDrive they need to be VERY careful about tyre swaps as many brands and models, even in the correct sizes, are not compatible with the xDrive system. Damage to the transfer case is the likely outcome if you use incompatible tyres.

We only recommend Michelin Pilot Sport 4S and Continental SportContact 6 in the standard sizes 225/35/20 and 255/30/20. They do not need to be star rated. AC Schnitzer have tested these and found them to be compatible with xDrive. We recommend the same tyres for RWD cars, but you are free to use others.

Interested in this (I don't have xDrive) but would consider it next time. So as I understood it xDrive is sensitive to different rolling circumference. I presume it doesn't know or care what brand of tyres are fitted. In which case Lorcan is it your experience that only Michelins are close enough tolerance. Or is there some other issue of compatibility I have not understood.

[Lorcan]

Originally Posted by martin10chk

Interested in this (I don't have xDrive) but would consider it next time. So as I understood it xDrive is sensitive to different rolling circumference. I presume it doesn't know or care what brand of tyres are fitted. In which case Lorcan is it your experience that only Michelins are close enough tolerance. Or is there some other issue of compatibility I have not understood.

You're correct, the circumference needs to be within 1% front to back when the tyres are new. AC Schnitzer only test with Conti and Michelin so it's possible/likely that other tyres will be compatible, but we also know that some are not, the Pilot Sport 4 (not 4S) for example is not compatible. Tread carefully. Tread! Get it? I'm here all week...

[HighlandPete]

Originally Posted by martin10chk

Interested in this (I don't have xDrive) but would consider it next time. So as I understood it xDrive is sensitive to different rolling circumference. I presume it doesn't know or care what brand of tyres are fitted.

The issue as I see it, the manufacturing tolerances of the generic sizing, even to ISO, DIN, ETRTO, etc., is too wide to always keep within the 1%.

We can look at the tyre size guides, we read the nominal figures, having no knowledge of the tolerances used for a particular tyre.

As an example, according to DIN 70020 at 37 mph (60 km/h), the nominal RC of our typical passenger car/SUV tyres can have a +1.5%/-2.5% tolerance.

[Lorcan]

Originally Posted by HighlandPete

The issue as I see it, the manufacturing tolerances of the generic sizing, even to ISO, DIN, ETRTO, etc., is too wide to always keep within the 1%.

We can look at the tyre size guides, we read the nominal figures, having no knowledge of the tolerances used for a particular tyre.

As an example, according to DIN 70020 at 37 mph (60 km/h), the nominal RC of our typical passenger car/SUV tyres can have a +1.5%/-2.5% tolerance.

Spot on, and then you have to account for wear as well. If the tolerance is the "wrong" way and the rears wear out faster than the fronts, you could be in trouble. Looks like BMW have twigged this with the F90 M5 which is xDrive and wears 285 fronts and 295 rears, both the same profile. Some scribbled calcs give a nominal circumference difference of 0.3%, but as the rears wear out faster they will wear IN to tolerance not wear OUT of it.

[HighlandPete]

Originally Posted by Lorcan

Spot on, and then you have to account for wear as well. If the tolerance is the "wrong" way and the rears wear out faster than the fronts, you could be in trouble. Looks like BMW have twigged this with the F90 M5 which is xDrive and wears 285 fronts and 295 rears, both the same profile. Some scribbled calcs give a nominal circumference difference of 0.3%, but as the rears wear out faster they will wear IN to tolerance not wear OUT of it.

All so logical from an engineering perspective, but so different when users want to play a different game.

BTW, I understand the M5 transfer box has some design changes which adds to the cooling efficiency.

[martin10chk]

So I read this as “don’t get an xDrive”. In any real world scenario the variation across tyres will trash the transfer box - I presume an expensive item. Seems pretty rubbish design to me to have a system that is so intolerant to expected natural variation!

[HighlandPete]

Originally Posted by martin10chk

So I read this as “don’t get an xDrive”. In any real world scenario the variation across tyres will trash the transfer box - I presume an expensive item. Seems pretty rubbish design to me to have a system that is so intolerant to expected natural variation!

Historically 4x4 have pretty much universally been tyre sensitive. The reason many had to have all tyres replaced together, or tyre shaving, if replaced running a part worn set. "Transmission bunching" has ruined many a drivetrain before BMW ever thought of xDrive. Check out Land Rover of the past, if you want to understand 4x4 transmission limitations.

Most users don't understand something like xDrive has engineering limits. Keep to approved tyres and the chance of faults and failures is minimal.

[Ennoch]

Originally Posted by martin10chk

So I read this as “don’t get an xDrive”. In any real world scenario the variation across tyres will trash the transfer box - I presume an expensive item. Seems pretty rubbish design to me to have a system that is so intolerant to expected natural variation!

And engines occasionally fail if you don't look after them, so don't get a car with an engine and instead cut a hole through the floor and go places Flintstone style. Yes, I'm being facetious but the reality is that if you want an effective 4wd system you're going to have limitations with tyres. Some setups are more fragile than others. The biggest downside of BMW's is the staggered wheel setup which you can't rotate to keep tyre wear even, but even then the reality is that driving style or the box just having a manufacturing weakness is as likely to give you a failure than the tyres being ever so slightly different in size.