Run Flat Low Profile for Rim Protection?

Coercion Shaman · 08-06-2018, 08:20 AM

I don't want this be a debate on handling. I have little doubt that the go flats will handle better.

We have the factory 19" rims on the 35is. I replaced the rear tires and my wife wanted to keep the RFTs. She just went on a trip for three weeks and I drove the Z4 during that time. I'm fine with everything except that the low profile RFTs are almost non existent when driving over pot holes. lane markers, etc. I get that they are low profile (had on other cars), but it is like there is no tire at all and you are driving on the rim over obstructions. I don't know that I have ever had a tire with this low of a profile, either.

My question is, will a standard tire handle this better? Or will that low profile still have the exact same problem? Would getting a slightly wider tire for a higher side wall aspect help? Since I have the indirect TPMS, would that still work as it is supposed to be relative tire spin on all four tires?

EDIT: Meant to say Go Flat in the title...

paris1 · 08-06-2018, 01:26 PM

You have the worst possible combination of wheel diameter and sidewall height from a ride quality standpoint. YES, a non-rft will improve that, at least for the majority of its tread life. I doubt if replacing with a slightly wider set of rfts would help much and it would be damned expensive. I replaced the 18” run-flats on my wife’s Z4 DD with Bridgestone non-rfts and it made a world of difference. I must say though that I have discouraged her from taking extended trips in the car as yours did because of the risk of having a puncture in some podunk town with only a Slime/pump kit in the boot.

impulsE89 · 08-06-2018, 02:07 PM

Everyone reports a noticeable ride improvement with goflats. This is to be expected because the car was designed for run flats, probably with softer springs to help the problem of stiff sidewalls. So naturally when you put on softer sidewalls the ride is going to be even softer because the suspension was designed to compensate for stiff RFTs. Seems to me to really correct the problem using goflats, one would need to then stiffen things back up a little with aftermarket suspension in order to maintain true sport handling.

Why not use a slime/inflater even for RFTs. The tire is going to be ruined anyway and this would be an extra insurance that you can get to a distant tire store.

Back to you Paris1?

paris1 · 08-06-2018, 02:44 PM

Your point about the suspension being tuned for run flats has been made here before and is no doubt true. However the consensus seems to be that it was done poorly and the result is a bone-crushing ride which can be improved (possibly at the cost of some handling prowess) by substituting non-run flats. My feeling is that E-89s are more GT than sports car anyway and because my wife doesn’t push it that hard in daily driving, it’s a worthwhile trade-off. Especially in light of the cost savings!

ray7792 · 08-06-2018, 11:49 PM

A non-RFT will 100% handle bumps and potholes better, even if the sidewall profile is the same, there is more soft rubber to absorb impacts. I've gone over the exact same bumps and potholes with the OEM RFT and on PS4S, the difference it night and day.

I know you said you don't want to make it into a debate about handling but the tire you choose to replace it with is going to be the primary deciding factor. The OEM RFTs honestly are not terrible summer tires purely from a compound standpoint. If you get a worse tire then yes it'll effect handling but something like continentals extremecontact sport or michelin PS4S, you will drastically gain more traction, lessened noise, and much more comfort. If you want to stiffen it up more then just change the adaptive dampers to sport or sport+

I personally also went up to 235/265 also in an attempt to gain just that tiny little bit more of side wall

You could also get a higher aspect ratio, maybe 40 front and 35 rear, the difference may cause like 3%(?) difference in speedo, personally don't like the looks of it though

Coercion Shaman · 08-07-2018, 06:11 AM

Then perhaps I will just give the non RFT a try. I don't have any complaints on the handling. I would go with your recommendation of the Ps4S or Contintentals from previous research.

I do have a slime kit, plugs and a compressor in all my cars already and have AAA for my wife (the Z4 is her primary car).

I really like the look of the 19" wheel, but didn't appreciate just how much it didn't dampen road issues until driving it for three weeks.

08-06-2018, 08:20 AM	#1
Coercion Shaman Private First Class 48 Rep 140 Posts Drives: 2019 Audi A5 Prestige S/B Join Date: May 2018 Location: Georgia iTrader: (0)	Run Flat Low Profile for Rim Protection? I don't want this be a debate on handling. I have little doubt that the go flats will handle better. We have the factory 19" rims on the 35is. I replaced the rear tires and my wife wanted to keep the RFTs. She just went on a trip for three weeks and I drove the Z4 during that time. I'm fine with everything except that the low profile RFTs are almost non existent when driving over pot holes. lane markers, etc. I get that they are low profile (had on other cars), but it is like there is no tire at all and you are driving on the rim over obstructions. I don't know that I have ever had a tire with this low of a profile, either. My question is, will a standard tire handle this better? Or will that low profile still have the exact same problem? Would getting a slightly wider tire for a higher side wall aspect help? Since I have the indirect TPMS, would that still work as it is supposed to be relative tire spin on all four tires? EDIT: Meant to say Go Flat in the title... __________________ Also own: 2012 Z4 35is M Sport Adaptive (Atacama Yellow) Last edited by Coercion Shaman; 08-06-2018 at 09:07 AM..
	Appreciate 0 Tweet Quote

08-06-2018, 01:26 PM	#2
paris1 Captain 90 Rep 745 Posts Drives: 2013 35i Space Grey over Coral Join Date: Oct 2014 Location: Northern Calif. iTrader: (0)	You have the worst possible combination of wheel diameter and sidewall height from a ride quality standpoint. YES, a non-rft will improve that, at least for the majority of its tread life. I doubt if replacing with a slightly wider set of rfts would help much and it would be damned expensive. I replaced the 18” run-flats on my wife’s Z4 DD with Bridgestone non-rfts and it made a world of difference. I must say though that I have discouraged her from taking extended trips in the car as yours did because of the risk of having a puncture in some podunk town with only a Slime/pump kit in the boot.
	Appreciate 0 Quote

08-06-2018, 02:07 PM	#3
impulsE89 Private 18 Rep 72 Posts Drives: 2Porsches2Alfas2Bmw2Corvettes Join Date: Sep 2017 Location: USA South iTrader: (0)	A couple questions about this Everyone reports a noticeable ride improvement with goflats. This is to be expected because the car was designed for run flats, probably with softer springs to help the problem of stiff sidewalls. So naturally when you put on softer sidewalls the ride is going to be even softer because the suspension was designed to compensate for stiff RFTs. Seems to me to really correct the problem using goflats, one would need to then stiffen things back up a little with aftermarket suspension in order to maintain true sport handling. Why not use a slime/inflater even for RFTs. The tire is going to be ruined anyway and this would be an extra insurance that you can get to a distant tire store. Back to you Paris1?
	Appreciate 0 Quote

08-06-2018, 02:44 PM	#4
paris1 Captain 90 Rep 745 Posts Drives: 2013 35i Space Grey over Coral Join Date: Oct 2014 Location: Northern Calif. iTrader: (0)	Your point about the suspension being tuned for run flats has been made here before and is no doubt true. However the consensus seems to be that it was done poorly and the result is a bone-crushing ride which can be improved (possibly at the cost of some handling prowess) by substituting non-run flats. My feeling is that E-89s are more GT than sports car anyway and because my wife doesn’t push it that hard in daily driving, it’s a worthwhile trade-off. Especially in light of the cost savings!
	Appreciate 0 Quote

08-06-2018, 11:49 PM	#5
ray7792 Private 12 Rep 65 Posts Drives: '14 35is Join Date: Jan 2016 Location: NJ iTrader: (0)	A non-RFT will 100% handle bumps and potholes better, even if the sidewall profile is the same, there is more soft rubber to absorb impacts. I've gone over the exact same bumps and potholes with the OEM RFT and on PS4S, the difference it night and day. I know you said you don't want to make it into a debate about handling but the tire you choose to replace it with is going to be the primary deciding factor. The OEM RFTs honestly are not terrible summer tires purely from a compound standpoint. If you get a worse tire then yes it'll effect handling but something like continentals extremecontact sport or michelin PS4S, you will drastically gain more traction, lessened noise, and much more comfort. If you want to stiffen it up more then just change the adaptive dampers to sport or sport+ I personally also went up to 235/265 also in an attempt to gain just that tiny little bit more of side wall You could also get a higher aspect ratio, maybe 40 front and 35 rear, the difference may cause like 3%(?) difference in speedo, personally don't like the looks of it though
	Appreciate 0 Quote

08-07-2018, 06:11 AM	#6
Coercion Shaman Private First Class 48 Rep 140 Posts Drives: 2019 Audi A5 Prestige S/B Join Date: May 2018 Location: Georgia iTrader: (0)	Then perhaps I will just give the non RFT a try. I don't have any complaints on the handling. I would go with your recommendation of the Ps4S or Contintentals from previous research. I do have a slime kit, plugs and a compressor in all my cars already and have AAA for my wife (the Z4 is her primary car). I really like the look of the 19" wheel, but didn't appreciate just how much it didn't dampen road issues until driving it for three weeks. __________________ Also own: 2012 Z4 35is M Sport Adaptive (Atacama Yellow)
	Appreciate 0 Quote