BMW 20" wheels and runflats issue

[topaz]

Hi

I recently bought a 2020 530d sports edition BMW. Sold my Porsche Macan due to the Sunroof leaking and flooding the car. Took them three weeks to fix. In the meantime, a friend loaned me a 530e ex-fleet car which drove beautifully and made me want to drive a car again hence the purchase. There is nothing wrong with the car but everything is wrong with the roads locally. I suspect it's a national problem. I've seen videos reviewing various beemers and they usually recommend changing the 20" to 19" with none runflats. Has anyone on here actually done this. The car has M-sport brakes and the front caliphers look huge and I'm not sure 19" would fit correctly.

[eddy77]

I’ve got a 2021 520i with the 20” rims and run flats. Initially hated it for jiggly ride but…….after some research I tried reducing the pressures all round from the recommended 2.4 bar to 2.2. Flipped the pressure monitor to all season so it still monitors but doesn’t complain that the pressures are low. Made a massive difference. Not perfect but now tolerable. When the RFTs are worn out I will put standard non run flats on which by all accounts makes a massive difference for the better.

So, try dropping the pressures and see how it feels. I had the same thought of dropping to 19s but as things stand the 20s are fine and will be even better once I ditch the rft setup.

My car doesn’t have adaptive suspension. It’s an M sport on stabndard M dampers. Hope that helps.

[SuperCharged V6]

20" with run flats here on my 530d, I enjoy the ride, don't find it harsh at all, despite the potholes, I have recently had all four tyres changed, and had the rims checked, no issues at all in 35k miles

[d_a_n1979]

topaz said:

Hi

I recently bought a 2020 530d sports edition BMW. Sold my Porsche Macan due to the Sunroof leaking and flooding the car. Took them three weeks to fix. In the meantime, a friend loaned me a 530e ex-fleet car which drove beautifully and made me want to drive a car again hence the purchase. There is nothing wrong with the car but everything is wrong with the roads locally. I suspect it's a national problem. I've seen videos reviewing various beemers and they usually recommend changing the 20" to 19" with none runflats. Has anyone on here actually done this. The car has M-sport brakes and the front caliphers look huge and I'm not sure 19" would fit correctly.

When I bought my previous it came with 20" alloys and RFTs... Binned them off more or less straight away and dropped to 19s with non RFTs and it made a whole world of difference. It drove & handled better, quieter and little to no tramlining!

My current F31 touring came on 19" alloys with RFTs; I've done exactly the same and dropped down a size (18s) and run non RFTs and as above; transformed the car. I have the M Performance 370/345mm brakes also

That's on M Sport suspension, non adaptive (my 7 series was adaptive)

It's horses for courses; some folk like them, some don't

Everyone I know that's had their car on RFTs have gone to non RFTs and haven't looked back

[topaz]

Interesting comments, thanks. I'll try the deflating the rft route first and see how that goes and then the 19" with a set of Michelins if that doesn't work. Might help if the Government gave the Councils a bigger chunk of the £30 billion they steal from motorists every yeat instead of spending it on railways in London.

[Mirinjawbro]

similar story to me.

have a 640d on RFTs. never had them before but the ride is not as comfortable as i hoped.

some people say RFTS are much better these days and wont notice much, others say you will.

dont want to change now incase im wrong as its over 1k to replace them all.


hmmmmm

[eddy77]

Seriously try reducing the pressures by a few psi. You will be surprised at how much better it feels. I was at my wits end with my 20s. My back was hurting from the hard ride and the car was awful. Dropping the pressures improved things massively to the point where I don’t mind the run flats anymore. It’s still overly jittery for my taste so I will go Michelin pilot sports non rft when the time comes but it’s not urgent now with the pressures reduced.

That said I really don’t believe you will regret spending £1k on non run flats. I’ve never read a comment from anyone who said anything other than it made a massive improvement. Don’t think you’d regret it. The question is whether you bin your rfts before they are worn out or wait until they need replacing. Depends how bad you find the existing run flats. I’m ok with them now and will get the wear out of them. But very much looking forward to replacing them in due course.

Edited by eddy77 on Thursday 25th May 20:39

[archie456]

I’d be wary of reducing the pressure more than a couple of psi on 20” wheels.

I had a very slow puncture and while the tyre hadn’t gone down by more than 5psi, when I went to get it fixed the tyre was trashed on the inside. I explained that it had never been flat, but the tyre shop said it was as a result of being under inflated.
I rang the technical helpline for Goodyear, and the very helpful guy said that I was very welcome to send it back to be checked, but it’s the camber on the 5 series that puts the load in the inside, which I guess is why the wheels always crack on the inside.

I bought some 18” wheels and while still on run flats it has transformed the car.

Edit: I forgot to say that the 20” wheels were shocking, with winter potholes wrecking both front tyres and both near side rims.

Edited by archie456 on Monday 29th May 19:57

[eddy77]

I had a look at my pressures today to see what it is running and I’m currently running at 33psi all round which is 2psi below the recommendation for a partially loaded saloon with 20” rims. Not sure where my 2.2 bar number came from so apologies for that!

My experience is that a couple of psi below the recommended has made a big difference. I’ve been running with these pressures for around 6 months over winter and it’s been fine. Interesting point around inside tyre wall. Will monitor but I really wouldn’t expect 33psi to be causing a structural issue when optimum is only 2psi more.

[Pica-Pica]

archie456 said:

I’d be wary of reducing the pressure more than a couple of psi on 20” wheels.

I had a very slow puncture and while the tyre hadn’t gone down by more than 5psi, when I went to get it fixed the tyre was trashed on the inside. I explained that it had never been flat, but the tyre shop said it was as a result of being under inflated.
I rang the technical helpline for Goodyear, and the very helpful guy said that I was very welcome to send it back to be checked, but it’s the camber on the 5 series that puts the load in the inside, which I guess is why the wheels always crack on the inside.

I bought some 18” wheels and while still on run flats it has transformed the car.

Edit: I forgot to say that the 20” wheels were shocking, with winter potholes wrecking both front tyres and both near side rims.

Edited by archie456 on Monday 29th May 19:57

I went from 19” Pirelli RFT to 18” Goodyear EfficientGrip RFT, much better.
A point to note, drive over speed cushions with one tyre in the centre, especially the horrible, nasty sharp-edged ones. Don’t let the inner edge of the rim go over the edge, there is less radial support on the inner edge of wheels.

[topaz]

What does p*** me off is that we have to look at taking these mesures on a £55k plus car, but as I said, it's more the state of the roads that causes this issue. £33 BILLION this crap Government take from the motorist every year. I almost hit another car a few days ago that was swerving it's way around potholes. I think 19" with non-runflats will be the way to go when I have enough money to do it. Thanks for posting, very useful.

[d_a_n1979]

topaz said:

What does p*** me off is that we have to look at taking these mesures on a £55k plus car, but as I said, it's more the state of the roads that causes this issue. £33 BILLION this crap Government take from the motorist every year. I almost hit another car a few days ago that was swerving it's way around potholes. I think 19" with non-runflats will be the way to go when I have enough money to do it. Thanks for posting, very useful.

As said re my F01:

Went from 20s with RFTs:



Tramlined on every road; noisy/crashy/not comfy etc

To 18s with non RFT winter tyres:



Car drove like it was on balloons but it handled really well and took the roads in the Highlands superbly

And then to 19s (albeit from the F10/11 range, so used 15/12mm spacers to have them sitting right with Falken FK510 non RFTs) and they were absolutely brilliant; drove/handled superbly. Smooth, comfy, quiet & very grippy

[topaz]

Looks good. I will certainly change to 19" when the RF have reached their minimum depth and then buy a Gunge puncture repair kit.

[d_a_n1979]

topaz said:

Looks good. I will certainly change to 19" when the RF have reached their minimum depth and then buy a Gunge puncture repair kit.

They made a very marked difference!

Personally I wouldn't wait for the tyres to get low; alloys & decent tyres sell easy enough. Exactly what I did with the 20s off my F01; sold them in a few days of being listed on eBay etc

Re tyre inflation kit; this is the one I had in the F01 and now have it in my F31:

https://www.amazon.co.uk/Slime-50129-Tyre-Repair/d...

[rottenegg]

eddy77 said:

I’ve never read a comment from anyone who said anything other than it made a massive improvement

What no one ever mentions is the loss of turn-in crispness/precision, which is a pleasant side effect of rock hard side walls.

But if you go for a decent UHP summer tyre like the PS4S, ContiSport 7 or Eagle F1 SuperSport, the reduction in turn-in precision isn't as huge as it would be if going for a no name ditch finder, but it is a negative change none the less.

Post 2012 BMWs running RFTs have a very particular feel about them through the wheel, off centre, which is lost when dumping RFTs. Everything from top mounts down will have been holistically tuned around RFTs. Most are happy with the compromise though. But climb back into one running RFTs again after 6 months or so, yeah, you definitely notice the difference!

The improvement in ride quality is more or less guaranteed though, unless you get really ste cheap tyres.

[Mirinjawbro]

in regards to all of the above.

what would people rate as the best thing to improve "comfort" and ride quality

- smaller wheels
- different tyres
- springs?

currently with a 640d on 20 RFTs. bouncy. not as comfortable as would imagine. really looking to change into some PS4S soon

any others?

[d_a_n1979]

rottenegg said:

eddy77 said:

I’ve never read a comment from anyone who said anything other than it made a massive improvement

What no one ever mentions is the loss of turn-in crispness/precision, which is a pleasant side effect of rock hard side walls.

But if you go for a decent UHP summer tyre like the PS4S, ContiSport 7 or Eagle F1 SuperSport, the reduction in turn-in precision isn't as huge as it would be if going for a no name ditch finder, but it is a negative change none the less.

Post 2012 BMWs running RFTs have a very particular feel about them through the wheel, off centre, which is lost when dumping RFTs. Everything from top mounts down will have been holistically tuned around RFTs. Most are happy with the compromise though. But climb back into one running RFTs again after 6 months or so, yeah, you definitely notice the difference!

The improvement in ride quality is more or less guaranteed though, unless you get really ste cheap tyres.

Same as what I did with my F01 probably; same suspension set up more or less!

Dropped to 18s for winters and 19s for summers; non RFTs and made a huge, marked improvement

Suspension (unless it needs replacing (old/worn etc) will be fine; its the RFTs that cause the main issues

[eddy77]

Appreciate the handling may not be quite as sharp on non run flats, but I’ll stick my neck out here and say I, in common with most 5 series drivers, rarely drive my car at anywhere more than 50% of its ability. I’d happily take the compromise for better comfort. Appreciate we’re all different but most drivers are not gods behind the wheel and would struggle to notice. IMHO.

[rottenegg]

Don't get me wrong, switching from 19" RFTs (nasty Pirelli P Zeros with the BMW * marking) to 19" ContiSport 7s was a great move. Significantly less tramlining on adverse cambers/road repair patches and obviously hugely improved ride comfort, less tyre roar etc....but I'm sorry....RFTs do definitely feel better in the corners!

It's just one of those classic compromises.

If you want a bit of both, I'd recommend the F1 SuperSport. Suitably stiff sidewalls for the off centre crispness, but not as harsh as RFTs.

The ContiSports are comparable in dry grip, and have next level wet grip (the best I've experienced to date, better than PS4S), but in typical Continental style, they are on the softer side sidewall wise.

And if it's of importance to you, non RFTs reduce unsprung mass, especially the Continentals. They're lighter than a PS4S and significantly lighter than a run flat of the same size. Damper rebound is noticeably better with lighter tyres.

[Mirinjawbro]

just recently changed the PSI in the 20 inch RFTs and what a difference.

they are now set to around 31/32 PSI and once driving settle around 33/34.

before they were set to 35 ish and went up to 37/38

car is way way smoother over bumps, more floaty, also seems to get better mpg (havent tested yet)

next step is PS4S once these wear out and maybe some different springs.