2018 R Tire Pressure Monitor is Not as Effecitve as I'd Like

[kevinkar]

Preparing to take my car in to a body shop this week for the rear end collision it sustained last week and I washed it and checked the tire pressures (also due to the freaking potholes I hit in the SF Bay Area to check and make sure all the tires were ok) and I noticed ALL 4 tires were 5-7 lbs low and the low pressure indicator has not come on for any of them. So either 7 lbs is not enough to rate as "significantly underinflated" or it's not a very good system.

In my opinion, 7 lbs is significant. My Corvette, which had internally mounted TPMS sensors, would always let me know when any of the tires were no more than 5 lbs low. While the VW system is not based on actual pressure, I would have hoped that it was sensitive enough to know when any of the tires were 5 lbs out or at least 7 lbs like two of them were. 32 psi is definitely not 39psi.

Granted the manual says it's no substitute for the owner checking and maintaining the tire pressure but what's the point of having a TPMS if it's not going to alert you when the tires are almost 20% low? So either my system is not working right or the system IS working right but not as effective as I'd like. All the tires have even wear so there is no indication of under inflation yet so maybe it's not that big a deal but I'd prefer it alert me at 5 lbs if not at least 7 lbs.

I might consider trying out a cheap bluetooth system (valve stem caps that connect to your phone) as a test to see if they alert me better than the VW system does. As it stands now, the VW system is not very good in my opinion.

 

[jimlloyd40]

Preparing to take my car in to a body shop this week for the rear end collision it sustained last week and I washed it and checked the tire pressures (also due to the freaking potholes I hit in the SF Bay Area to check and make sure all the tires were ok) and I noticed ALL 4 tires were 5-7 lbs low and the low pressure indicator has not come on for any of them. So either 7 lbs is not enough to rate as "significantly underinflated" or it's not a very good system.

In my opinion, 7 lbs is significant. My Corvette, which had internally mounted TPMS sensors, would always let me know when any of the tires were no more than 5 lbs low. While the VW system is not based on actual pressure, I would have hoped that it was sensitive enough to know when any of the tires were 5 lbs out or at least 7 lbs like two of them were. 32 psi is definitely not 39psi.

Granted the manual says it's no substitute for the owner checking and maintaining the tire pressure but what's the point of having a TPMS if it's not going to alert you when the tires are almost 20% low? So either my system is not working right or the system IS working right but not as effective as I'd like. All the tires have even wear so there is no indication of under inflation yet so maybe it's not that big a deal but I'd prefer it alert me at 5 lbs if not at least 7 lbs.

I might consider trying out a cheap bluetooth system (valve stem caps that connect to your phone) as a test to see if they alert me better than the VW system does. As it stands now, the VW system is not very good in my opinion.

When I had the stock TPMS mine would give me a low tire warning with as little as a 3 lb difference. It was so annoying I converted it to the TPMS system with the sensors in the tire.

 

[kevinkar]

Yeah, 3 is probably too early but 7 is too late. 5 is just right.

 

[GenX Retread]

I may not understand this car's TPMS system correctly, but I believe it uses the ABS wheel speed sensors to detect differences in wheel speed, indicating that one tire is low. If all 4 tires lost exactly the same amount of air at the same rate, maybe the car doesn't register any differences day to day, and doesn't indicate a low tire?

 

[jimlloyd40]

I may not understand this car's TPMS system correctly, but I believe it uses the ABS wheel speed sensors to detect differences in wheel speed, indicating that one tire is low. If all 4 tires lost exactly the same amount of air at the same rate, maybe the car doesn't register any differences day to day, and doesn't indicate a low tire?

I was thinking the same thing but that would require each tire to lose pressure at the same time.

 

[krs]

I may not understand this car's TPMS system correctly, but I believe it uses the ABS wheel speed sensors to detect differences in wheel speed, indicating that one tire is low. If all 4 tires lost exactly the same amount of air at the same rate, maybe the car doesn't register any differences day to day, and doesn't indicate a low tire?

That was my understanding as well. I've had mine go off with as little as 3psi difference in one wheel.

 

[The Fed]

Mine alerts at about 33 with a setting of 39. You can make it alert sooner, just set the pressure higher.

 

[kevinkar]

It worked on that one day I got a nail in one tire. Apparently it immediately registered low pressure and I got it repaired in short order. If all slowly lose pressure at the same time, I can see why that (failure to notify) might happen but it's still not a good outcome if it fails to alert the driver. I was going to say maybe the VW system is better than nothing but it seems it's just as good/bad as nothing.

Yeah, I generally set mine at 39 as well. Might be a bit high as the ride on 19" tires is pretty bad. Could probably drop them all down a few.

 

[sterkrazzy]

I don't think having 19's help either. If they were 17s or 18s it'd have an easier time detecting pressure loss.

 

[jimlloyd40]

For anyone wanting to convert the stock TPMS to sensors in the tires see below.

https://m.aliexpress.com/item/32962...tedetail&spm=a2g0s.8937460.0.0.545a2e0efjLec3

 

[Keehs360]

I may not understand this car's TPMS system correctly, but I believe it uses the ABS wheel speed sensors to detect differences in wheel speed, indicating that one tire is low. If all 4 tires lost exactly the same amount of air at the same rate, maybe the car doesn't register any differences day to day, and doesn't indicate a low tire?

That’s exactly what’s going on

I check my air monthly (I drive 200-300 miles a month) and multiple times during track days

so far the tpms has gone off twice on me. And my tires (according to the digital air compressor at the gas station) are usually only low by 4-5 psi.

 

[cb1111]

I may not understand this car's TPMS system correctly, but I believe it uses the ABS wheel speed sensors to detect differences in wheel speed, indicating that one tire is low. If all 4 tires lost exactly the same amount of air at the same rate, maybe the car doesn't register any differences day to day, and doesn't indicate a low tire?

BINGO. VW uses the indirect system that will not show time or temp based changes. TPMS is not intended to replace the need for periodic checks, but is intended to give advance notice of a catastrophic tire failure.

 

[SRGTD]

BINGO. VW uses the indirect system that will not show time or temp based changes. TPMS is not intended to replace the need for periodic checks, but is intended to give advance notice of a catastrophic tire failure.

^This. The indirect TPMS that VW uses is an aid to help detect defects such as punctures and deflation as a result of pothole damage.

All tyres lose a small amount of pressure over time, and IMHO there’s no substitute for periodic manual pressure checks, and buying a tyre pressure gauge and a tyre inflator that can be powered from the car’s 12v socket is a good investment (I keep mine in the car boot / trunk, along with the pressure gauge).

Manually checking my tyres form part of my other regular checks - e.g. under the bonnet / hood fluid levels. It also gives an opportunity to do a visual check for items that might have become embedded in the tyre tread, such as nails and screws, and checking the tyre tread depth across the width of the tyres for early signs of uneven wear, which might indicate an alignment issue. No tyre monitoring system - direct or indirect - can undertake these visual checks, they don’t take long, and along with tyre pressure checks can save you money in the long term, as they‘ll help an owner to maximise the life of their car’s tyres.

 

[IWMTom]

I may not understand this car's TPMS system correctly, but I believe it uses the ABS wheel speed sensors to detect differences in wheel speed, indicating that one tire is low. If all 4 tires lost exactly the same amount of air at the same rate, maybe the car doesn't register any differences day to day, and doesn't indicate a low tire?

It's based on deviation from saved values, not checking against each other.

When you reset the system, it'll undergo an adaptation process where it will record wheel speed and vibration patterns. This takes approximately one hour of driving.

 

[kevinkar]

It's based on deviation from saved values, not checking against each other.

When you reset the system, it'll undergo an adaptation process where it will record wheel speed and vibration patterns. This takes approximately one hour of driving.

Yes, which is why I'd expect it to compare the 7 lbs low values against the originally saved fully inflated cold pressure values when calibrated. There has to be more of a difference it can see when that much pressure is lost (remember that 7 lbs is almost 20% low.) It definitely did work when I got that nail but I'd think I should be able to fill the tires cold, calibrate and drive to make sure the values are indeed captured, release 7 lbs from each tire and immediately be told there's an issue. Shouldn't make a difference if it's lost incrementally or immediately if it's different from the original calibrated values. As I said, it's not as effective as I'd like.