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Changing from run flats to regular

48K views 83 replies 27 participants last post by  Erwan 
#1 ·
I live in sunny southern California, I have roadside assistance, and other than an occasional trip to Big Bear or Mammoth or Arizona, help is only minutes away, so I really don't need the run flats on my GLA250 (2wd).

When the RF's finally wear out, I'd like to change over to regular tires, but wondering what happens to the TPMS that wants to see 44psi? Can it be reset to something like 35psi?
 
#2 · (Edited)
The TPMS threshold can be reset using the car's settings menus. Basically you set your car's tires pressure to the correct values then reset TPMS. TPMS then uses the new values for its baseline.

However, 44 psi is way too high for your current tires it should be 32 psi front/29 psi rear (at least those are the correct values for my 2016 GLA 250 4Matic). 44 psi is the maximum pressure rating for the tire. The correct values for your car can be found on the fuel filler flap.
I bet you have a very harsh ride as a result and poor tire wear, too.
 
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#3 ·
Yeah ride has always been harsh, but I assumed they were correctly set at the factory! (Foolish of me, I guess). I've never heard of a tire at that pressure before, but assumed it was because of the RF.

Seems to me that this incorrect setting (for a year now) should be a warranty issue, as well as tire wear. Doubt I'll get MBZ to agree with that!
 
#5 ·
Hi WhiteRabbit-You surely are right. Thanks. The sticker on the driver side door jamb says only 44, the fuel filler flap says 34 front and 29 rear. I will fix that first thing tomorrow. My suggestion to Oceansol would be, if you are thinking of changing from the runflats, and you still have some tread, do the change sooner rather than later, and save the runflats for when you get rid of the car. This could be especially important if you lease, as some of the lease folks want to see runflats when the car is turned in, and if you trade it, not having runflats could affect the trade value.
 
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#6 ·
Thanks for the tip, but my car is purchased and I keep my cars a long time, so I'll just run them till their done.

Thanks so much for this forum, too! I've learned a lot and continue to do so.
 
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#7 ·
I changed front pressure, cold, to 34 and rear to 32. The TPS didn't have a problem with this, without doing a reset. Will see if it feels different.
 
#8 ·
I would still reset the TPMS since you don't know what baseline it is using.
If you do reset it, do so when the tires are cold.
 
#9 ·
Good advice-will do. I noted that all 4 tires were at 37, cold, this morning before I changed pressures. As mentioned I put fronts at 34 and rears at 32. The pressures seen on the TPMS system were 1 or 2 pounds higher than at the tires-I checked while adjusting air with two different gauges, both agreed. I kept the system on while driving, and the TPMS went up to 37 pounds, all 4 wheels, after a few minutes of 60 mph driving.
 
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#11 ·
TPMS on both my Mercedes also reads 1 - 2 lbs higher than my tire pressure gauge does. And I use pro type gauge.
So I go by the gauge and that gives me a little cushion. :)
 
#12 ·
I emailed my service writer to discuss this situation, and he said 'no problem, bring it in we'll fix it.' So I stopped this morning and a young man came and took the car to the service area for a few minutes, then when he brought it back he said, "all fixed, all 4 tires at 44psi and the TPMS is reset!" He showed me the gas filler cap with the recommended inflation pressures, and said that they always inflate to the max allowable! I was very surprised by that and told him why do they go the the max when most of the time I don't have max load. He said he could set it anywhere I wanted.

So we discussed, and settled on 35psi front, and 33psi rear. I know recommended is 31F/29R, but since they do this all the time I decided a compromise was in order.

Any thoughts?
 
#13 ·
Since you had driven in and they took the car right away the tires would have warmed up quite a bit. The pressure should be checked and set when the tires are cold.
Check what TPMS says the pressures are after the car has set over night without being driven. I bet the pressure will be lower in every tire.
Personally I never rely on the dealer or any garage to set the tire pressures correctly. They invariably set them too high.
 
#14 ·
When they delivered my car, the dealer had pumped up the tires as well (above 40 psi). Lowering them to what the gas cap says significantly improved the ride (very harsh -> manageable).

Also, keep in mind that what your TPMS shows could be off due to altitude. I live at 6,000 ft and travel to 8,500 ft and the car generally shows 4-5 psi over where it is with a good gauge. All cars I have had with TPMS do the same thing at altitude.
 
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#15 ·
Thanks guys, I thought about the fact that the tires were warm when I brought it in, so likely they'll be lower when I head home tonight. In fact, that's why I had him go 4psi over, because I figured they'd be about right when cool. I guess I have to figure out how to reset the TPMS to current pressures.

Thanks!
 
#17 ·
To reset the TPMS monitor values, from page 335 of the 2015 GLA Owner's Manual (pdf version):
Set the tire pressure to the value recommended for the corresponding driving situation on the Tire and Loading Information placard on the driver's side B-pillar (Y page 328).
Additional tire pressure values for different loads can also be found on the tire pressure table on the inside of the fuel filler flap (Y page 328).
Make sure that the tire pressure is correct on all four wheels.
Make sure that the SmartKey is in position 2 in the ignition lock.
Press the Left or Right Arrow button on the steering wheel to select the Serv. Menu.
Press the Up or Down button to select Tire Pressure.
Press the OK button.
The multifunction display shows the current tire pressure for each tire or the Tire pressure will be displayed after driving a few minutes message.
Press Down arrow button.
The multifunction display shows the Use current pressures as new reference values message.
If you wish to confirm the restart:
Press the OK button.
The Tire Press. Monitor Restarted message appears in the multifunction display.
After driving for a few minutes, the system checks whether the current tire pressures are within the specified range. The new tire pressures are then accepted as reference values and monitored.
If you wish to cancel the restart:
Press the Back/Cancel button.
The tire pressure values stored at the last restart will continue to be monitored.


Its not as complicated to do as it seems from the above directions. ;)
 
#16 ·
Rayman, I live at sea level, but when I go up to Big Bear (6750ft) in the winter, the car in the cold mornings always show low pressure. So I hit a gas station and bring it up a bit, but just a bit.
 
#18 ·
FWIW, here is the temperature compensation chart for filling tires. The colder it is the less pressure you supply (moles of air support the car, not psi). This chart also helps detail air loss with colder temperatures which can occur at higher elevations. Of course, there is natural leakage through the tire itself, so monthly checks are a good thing. I use the TPMS on my 997 more to check for potential nails than anything else. I count on my tire gauge fill in the details.

PS: The table image was resized when downloaded. Hopefully it is still readable.
 

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#19 ·
compact spare?

We are considering a GLA250 4matic as my wife's daily driver, downsizing from an ML bluetec. I'm leery of this pocket benz, but she likes it. One concern from a test drive [19" wheels, Conti SSR MOE tires] is the rough ride. If we reach a deal on this certified used [a dealer demo, 5k on the odo], one factor will likely be there willingness to sub back the 18" 5 spoke 7"w wheels and out of the MOE tires into a Michelin LTX or similar regular tire. I don't see a compact spare listed for the GLAs. Anyone have one/know what will fit? I see ML compact spares, an 18x4 wheel on the same 5x112 bolt pattern - anyone know for sure this will work, or what would? Thanks.
 
#21 ·
On a GLA 250 4Matic with light load (2/3 people little cargo) I found that 34PSI (cold 68F) Front anf Rear provides great handling. Once warm, the fronts will be a couple of PSI higher than the rears and that is normal and due to the weight distribution.

For the same tire size, runflats or not, the tire pressure should be the same.
 
#22 ·
Re runflats... I drive other cars with high performance Summer non-runflat tires and I think that the factory fitment - Continental ProContact TX SSR runflat - is an excellent tire. I do not understand those who consider it harsh/loud; I guess they never experienced true harsh/loud tires.
 
#23 ·
RFT's are way too harsh !!! ... the so called "soft" MB's MO Extended Mobility is still very harsh. You will be pleasantly surprised when you switch to non-RFT's how good riding your GLA's suspension really is. I pleasantly found this out when I dumped my BMW's e93 RFT's and installed non-RFT's. In my 2017 GLA 250 SUV, the oem tires are Bridgestone Dueller 235/50 R18 97H speed, which is a run of mill ordinary tire size, there are actually at least 90 available tires. for this size. The top brand in my case is Michelin Primacy MXM4
 
#26 ·
RFT's are way too harsh !!! ... the so called "soft" MB's MO Extended Mobility is still very harsh. You will be pleasantly surprised when you switch to non-RFT's how good riding your GLA's suspension really is.


My 2015 GLA250 4Matic came with 19" Goodyear Eagle MO RF tires. Last year I picked up a set of four non-RFT 19" Continental Pro Contact tires mounted on MB rims from a member of this group. I decided to switch out Goodyear RFTs for the Continentals as my winter tires last November. (Mostly a waste of time since we hardly had any snow and only one ice storm in Indiana this winter.)


After driving the non-RFT Continentals for four months, I frankly don't notice a significant difference in ride quality or road noise compared to the Goodyear RFTs. The Continentals did have superior grip in the ice storm.


Do you think the change to non-RFT is more noticeable because you're equipped with 18" tires instead of my 19"?
 
#24 ·
PS: I am definitely going to dump the MOExtended Mobility tires and install non-RFT's. Towards that goal I equipped my GLA with the TireFit mobility kit, i.e. an electric pump with sealant ... sourced from MB UK... and it fits perfectly in the trunk even with the up graded Harman Kardon sub woofer unit !!!
 
#27 ·
Hey Hook,

How did you purchase this kit? Were you able to buy it online/eBay or did you have to reach out to a MB UK dealership directly?
 
#29 ·
I bought a kit called Slime Smart Spair for my BMW when I changed to non-runflats. It contains a can of Slime sealer and an electric tire inflator. At the time a similar kit from BMW was over $100. I paid around $25 for this kit. I did some research at the time (2011) and found that Slime was one of the products that got pretty good reviews, and one of the factors cited for giving the good review in most cases was that it didn't interfere with tire pressure sensors. Most users felt the pump was very slow, which wasn't a bother, because I already had an inflator that is pretty good. I am completely satisfied with my Slime Spair kit; I haven't had a flat since I got it.
 
#32 ·
I am going to change from run flats to non run flats. I got an offer from the local MB dealer on Pirelli P Zero Nero All Seasons-$172 per tire, mounted and balanced. They are less expensive at Tire Rack, but when you add delivery and mounting/balancing, the Tire Rack price is more. Anybody have experience with Pirelli P Zero Nero?
 
#33 ·
I did get non-runflats-the Michelin Pilot Sport A/S+. Major difference in ride, noise, handling. Earlier in this thread it was mentioned that tire pressures would be the same as the run flats. Is there agreement on that concept?
 
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#35 ·
I'd look at what the recommended pressures are for a GLA45 and use them if opting for an UHP tire like the Sport 3+ or the Conti DWS06. You may find that something like a premium All Season touring tire works well on the 250 (front or AWD). Many will not like the noise the UHP tires make. BTW, the Pirelli is a good tire but my sense is the Michelin and the Conti may be better. Price installed is very good IMHO.
 
#38 ·
I just got rid of stock Goodyear efficient grip run flat 235/45/19 and got MICHELIN Pilot sport 4. The difference is huge! Like driving a different car. Much better ride quality, no damps, less rattles, better handling and no road noise! I am looking now for a tire fit kit. Do you know the price of the original?
 
#39 ·
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