Tyre Pressure Loss !

[VKS]

Just to share..Was driving back from PD and suddenly "Tyre Pressure Loss" message popped out on the idrive..checked the tyre pressure status and all 4 tyres showing yellow instead of greean ... how come all 4 tyres?Then called a buddy from AB and he recommended me to check air pressure on all the tyres and pumped 220psi front and 200psi rear...go to idrive and reset/confirm the desired pressure after pumped air..Then waited few secs to initializing and :top: all four rft's turn green again..Found couple of tyres less pressure and one rear extra inflated so i guess the system found no balance on wheel rotation due to difference on tyre pressure..very very impressed with this safety system since i thought it will only reminds during puncture as correct tyre pressure is very very important for fast drivers..Gong Xi Gong Xi

 

[Schwepps]

Good to know the RFM worked, VKS. :top: It would be interesting to know how sensitive it is: what were the pressures of the 4 tyres before you pumped them up?

BTW, it can't be 220/200psi, that would be in kPa units. 220kPa is 32psi and 200kPa is 29psi. And the fronts shouldn't be higher than the rears! Depending on your tyre sizes and whether they're RFTs, that pressure is way low. Mine are 250kPa/36psi fronts and 280kPa/40psi rears, per the recommended pressures.

 

[pussy]

Good to know the RFM worked, VKS. :top: It would be interesting to know how sensitive it is: what were the pressures of the 4 tyres before you pumped them up?

BTW, it can't be 220/200psi, that would be in kPa units. 220kPa is 32psi and 200kPa is 29psi. And the fronts shouldn't be higher than the rears! Depending on your tyre sizes and whether they're RFTs, that pressure is way low. Mine are 250kPa/36psi fronts and 280kPa/40psi rears, per the recommended pressures.

yes, correct for the e90 cars, recommended..

as for me, i m on 34psi front, 38 at the rears.. car drives like a dream..:top:

 

[bimmerdude]

Good to know the RFM worked, VKS. :top: It would be interesting to know how sensitive it is: what were the pressures of the 4 tyres before you pumped them up?

BTW, it can't be 220/200psi, that would be in kPa units. 220kPa is 32psi and 200kPa is 29psi. And the fronts shouldn't be higher than the rears! Depending on your tyre sizes and whether they're RFTs, that pressure is way low. Mine are 250kPa/36psi fronts and 280kPa/40psi rears, per the recommended pressures.

hey Prof,

i have a severe arithmatic adeptness... always had a problem with numbers.. worse still when it involves having to deal with volume/pressure units!
so, for a E90 320i sports with 225 front and 255 rear RFTs, what would be the recommended pressure?
the air pressure scale on the door isnt very helpful to me la..too many diagrams and combinations of numbers!

thanks Prof!

 

[VKS]

Good to know the RFM worked, VKS. :top: It would be interesting to know how sensitive it is: what were the pressures of the 4 tyres before you pumped them up?

BTW, it can't be 220/200psi, that would be in kPa units. 220kPa is 32psi and 200kPa is 29psi. And the fronts shouldn't be higher than the rears! Depending on your tyre sizes and whether they're RFTs, that pressure is way low. Mine are 250kPa/36psi fronts and 280kPa/40psi rears, per the recommended pressures.

Ops my bad Schwepps..its on kPa actually but i was recommended 220kPa on front and 200kPa on rear ones..before i pumped the air it was around 180 on front tyres and 180 on rear left while 220 on rear right...my fault i didnt give a proper check before i travel..anyway this system proved to be very useful for someone like me imagine if theres no fault message then i might be driving back with this hazard all the way..

Do you mean the recommended setting for stock RFT on E90 325 is 250kPa/36psi fronts and 280kPa/40psi rears?

 

[Schwepps]

hey Prof,

i have a severe arithmatic adeptness... always had a problem with numbers.. worse still when it involves having to deal with volume/pressure units!
so, for a E90 320i sports with 225 front and 255 rear RFTs, what would be the recommended pressure?
the air pressure scale on the door isnt very helpful to me la..too many diagrams and combinations of numbers!

thanks Prof!

For 225 front and 255 rear RFTs on 18 inch wheels, the recommended pressure with a load of 4 people is 250kPa (36psi) front and 280kPa (40psi) rear. You can safely reduce both front and rear by up to 30kPa (4psi) if your load is mostly 1 or 2 people.

 

[Schwepps]

Ops my bad Schwepps..its on kPa actually but i was recommended 220kPa on front and 200kPa on rear ones..before i pumped the air it was around 180 on front tyres and 180 on rear left while 220 on rear right...my fault i didnt give a proper check before i travel..anyway this system proved to be very useful for someone like me imagine if theres no fault message then i might be driving back with this hazard all the way..

Do you mean the recommended setting for stock RFT on E90 325 is 250kPa/36psi fronts and 280kPa/40psi rears?

180 vs 220 is 60kPa or almost 9psi. Good to know that's the sensitivity of the RFI system, thanks! :top:

180kPa (26psi) is low, but not below minimum. RFTs have stiff walls that are not designed to flex, and should not be allowed to flex, or they'll get damaged. Driving around continuously below 160kpa (23psi) will damage the tyre from the inside. RFTs also need to be pumped hard if you want maximum life out of them; lower pressures lower their thread life.

Whichever AB person told you the pressures of your 325i Sport's 225/40/18R fronts are 220kPa and 255/35/18R rears are 200kPa doesn't even know his own products! Look at the label on your B-pillar and you'll see it says 250kPa and 280kPa. In any case, fronts should never be higher than rears, even on a FWD car.

If one drives above 110kmh on the highways, one should check one's tyre pressures regularly. Blowouts are caused by under-inflation, not over-inflation. And a blowout at high speed can be fatal. Not checking tyre pressures is simply being irresponsible to self, family and other road users.

 

[MSport]

Mine are 250kPa/36psi fronts and 280kPa/40psi rears, per the recommended pressures.

Bro, that's the recommendation for a full-load. :top:

But what about if 90% of the time is only a single driver? Should the 250kPa/280kPa for front/rear respectively or use the recommended 240kPa/270kPa for front/rear ?

 

[Schwepps]

No mate, that's standard load. Full load of 5 adults + luggage is 280 (40psi) and 320 (46psi) per the sticker.

So 10% of the time, your car is double driver? (kidding) As I said to bimmerdude, it's okay to drop 30kPa from the standard load if mostly 1 or 2 adults only, so you can go down to 220 (32psi) and 250 (36psi)

 

[bimmerdude]

No mate, that's standard load. Full load of 5 adults + luggage is 280 (40psi) and 320 (46psi) per the sticker.

So 10% of the time, your car is double driver? (kidding) As I said to bimmerdude, it's okay to drop 30kPa from the standard load if mostly 1 or 2 adults only, so you can go down to 220 (32psi) and 250 (36psi)

sorry prof, i didnt say my tire size. Its 17 inch standard issue rfts. mostly 1 or 2 adults plus 2 kids (3 and 6 yrs). so i can safely go to 32psi front and 36psi rear? mostly city driving.

thanks Prof !

 

[viewfinder]

Just curious, does the label on the b-pillar applicable to non-RFT's both 17" and 18" (don't suppose staggered/non matters here)? If not, what's the offset for non-RFT? Thx.

 

[dzuljazz2001]

yes, correct for the e90 cars, recommended..

as for me, i m on 34psi front, 38 at the rears.. car drives like a dream..:top:

:top: though the rfm is very sensitive to loss of air pressure ...(dont really know abt other models) but a drop of 5 psi and above on my E60 will trigger the system. Went thru the experience (had to stop a few times Ktn - KL) of the system triggering the "you hv a puncture" with no noticeable puncture. Finally after reaching KL took the tyre off only to find that my rim had cracked!!! I was very lucky that nothing bad happened!!

 

[Schwepps]

Bimmerdude, when you talk tyres, you need to give the whole size description. So yours are 225/ ? /17 and 255/ ? /17. What are the aspect ratios? (the middle no) Different sizes need different pressures of course.

You'll need to look at your own B-pillar for your particular sizes, but offhand I think 32/36psi would be fine.

 

[Schwepps]

No, not applicable to non-RFTs, Viewfinder. Maybe those who have gone non-RFT can help you.

Based on other similar-sized cars, I would guess 210kPa (31psi) and 230kPa (33psi)?

 

[astroboy]

My rule of thumb:

Front 29~33psi, Rear 32~36psi.. for my 225/45R17 RFTs..

For town driving, I prefer to run soft due to the terrible road condition in town and housing areas while outstation highway or spirited runs, I prefer to run hard.. :love:

For track days or gymkhana... flat 40psi..

 

[David Yong]

I'm on non RFT 235/35/19 front and 265/30/19 rear with 30psi front and 32psi rear most of the time. But sometimes will go for 32psi front and 35psi rear (I used this pressure too for my previous 18").

 

[Schwepps]

There you go View-ey. Err on the high side anyway and you won't go wrong. The trend is above 30psi pressures for tyres these days. Even the Myvi specifies 31psi all round for their tiny 175 tyres.

 

[bimmerdude]

Bimmerdude, when you talk tyres, you need to give the whole size description. So yours are 225/ ? /17 and 255/ ? /17. What are the aspect ratios? (the middle no) Different sizes need different pressures of course.

You'll need to look at your own B-pillar for your particular sizes, but offhand I think 32/36psi would be fine.

ok prof, i checked. my tires are 225/45/17 front and 255/40/17 rear. Staggered and RFTs. 32/36 psi?

thanks prof.

 

[Schwepps]

Bimmer, you should check your B-pillar too. My sticker only has markings for 18" staggered wheels. But I reckon your staggered set-up should have the same recommended pressures, ie 250/280kPa (36/40psi). So going down to 32/36psi is okay. But do bear in mind that the compromise for increase in comfort is shorter lifespan for your expensive RFTs.

A good middle road would be to go 34/38psi like Pussy (don't you just love his nick? )

 

[astroboy]

.. So going down to 32/36psi is okay. But do bear in mind that the compromise for increase in comfort is shorter lifespan for your expensive RFTs...

Very true.. but the bumpier ride from a hard tyre will shorten life span of our engine and transmission mounts and other bushings as well.. pickup, FC and handling improves though..

Just remember there's no free lunch.. to go either way, there's a price to pay. That's why I chose to use different pressure at different occasions.. :wink: better still, over inflate them and leave them for months for the pressure to slowly soften down to say... 28psi... then I inflate them back to mid 30s for the next cycle..