Watchdog: Faulty safety systems

Watchdog: Faulty safety systems
5 Sep, 2012 11:00am Jon Morgan

Why fork out on expensive safety systems if you can't rely on them?

What's the point in an expensive safety warning system if you still have to make manual checks of the part of the car it’s supposed to monitor?

That’s the question on Mike Allen’s mind. Mike, from Reigate, Surrey, was amazed when he took his BMW 5 Series to his local Kwik Fit to get the tyres checked.

He was told the car was dangerous to drive until new rear tyres were fitted. The rubber was badly worn – yet Mike hadn’t noticed. “The inside of the tyres had worn badly and unevenly,” he said. “But there was plenty of tread on the outside.”

He also hadn’t been worried about his tyres as his car came with a factory-fitted tyre pressure monitoring system (TPMS). This is a £255 option on the 5 Series. But even though the back right tyre had virtually no air in it, the expensive TPMS gave no warning. “If the tyre had given up on the motorway, it could have been really serious,” Mike said.

Staff at his local dealer, Vines of Redhill, argued Mike should be checking his pressures manually. “But if that’s the case, what’s the point in having a tyre pressure monitoring system?” Mike asked.

We put that question to Vines. Its service adviser, Paul Gilchrist, said: “The light only comes on if the pressure in one or more of the tyres is different to the others. It won’t come on if they’re all low by the same amount.”

We pointed out that only two of Mike’s tyres were affected, but the garage would only add that it had checked his system. “Any faults would have shown up,” Gilchrist explained.

A BMW spokesman told Auto Express it was “extremely rare” for the TPMS to fail, adding: “I don’t know of any issue we’ve had since the system was introduced.”

The AA’s legal team added that Mike would have to prove the TPMS was defective to take legal action, telling us: “Had something happened and it could be proven there was a defect in either the material used or the way it was put together, then he could pursue a claim against the manufacturer under product liability legislation.”

The problem
Mike’s TPMS system failed to tell him when his tyres were under-inflated. BMW said he should check his tyres manually – so what’s the gadget’s point?

BMW's response
BMW is unaware of any issues with its TPMS system and has had no record of failures. The dealer reiterated its advice that owners conduct manual checks.

Legal advice
The AA’s legal team says that if a motorist is in an accident as a result of a fault that should have been flagged up by a safety system, they may be able to pursue the manufacturer under product liability legislation.

Our verdict
Mike makes a great point... Why would you fork out £255 for a fancy gadget if it can’t be relied upon? If you need to manually check tyre pressures anyway, there’s no point in having a TPMS.

Do you have a motoring problem that needs investigating? We're here to help… E-mail or Tweet us @AutoExpress.

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Tricky one. They are right, it's in most contracts of sale, lease, company car ownership etc that you must check the tyre pressure.

There is research as well that says the more safety features we have the more likely we are to take risks, i.e. it is referred to as "risk compensation" by Wilde (1982) and there is an interesting article on this matter by Charles Spence in The Psychologist magazine vol 25 no 9 Sept 2012.

Disappointing to see BMW being defensive about it though. They could have offered to fully check the car and offer the driver some tuition over the limitations of his systems. It is sad to see that so many companies start from such a defensive and closed position putting the onus on the customer to prove things, I always remind myself you are buying into an idea and a service, otherwise it's just another tin can that handles better than other tin cans. Take note BMW your service needs to handle as well as your cars.

That said my TPMS on my 3 series worked a treat a couple of weeks ago, shame I had to go all the way back to main dealer to get a new tyre as we don't get a spare these days, and the foam works only on non-audible leaks apparently...

Most of these systems use the ABS sensor which works on the rate of rotation of the wheel, and makes a comparison to the previous value, if the change is only small i.e. a slow puncture or gradual loss of pressure over time it won't detect this as a fault as the rate of change is small so could be attributed to a number of common environmental factors, therefore is ingnored by the system. Otherwise it would beep at you every 20 seconds! They are there to warn you of sudden deflations, not as a substitute to proper checks and maintenance.

On another note this was a very poor excuse for journalism... I felt like I was reading the daily mail not a well respected specialist publication.

I spent 255 quid so I shouldn't have to think any more!

This is what happens when manufacturers (e.g. BMW, VW Group) use the cheaper version of TPMS, using the ABS sensors and some extra software to calculate any difference in rolling circumference, rather than the more expensive system using in-wheel pressure sensors (as used by many non-premium brands such as Renault, Nissan and Hyundai). That system would have detected the low pressures in this case.

The TPMS is just an aid, it's not a tool to rely on, neither is intelligent cruise control, neither is an oil light! It's the drivers responsibility to check the tyre pressures. In wheel pressure sensors cost the customer more in the long term - with their 2 year battery life and interference from other vehicles. In this case, both tyres were deflated - hence in the BMW owners manual it warns drivers to check tyre pressures manually every 2 weeks.

Disappointingly this type of article seems to crop up more and more on AutoExpress. Another example which comes to mind was the BMW owner who was complaining that his local council wouldn't grit his unadopted road in the winter, and had suggested he shouldn't have bought a rear wheel drive car. I just thought that surely the residents on the street could have just bought some bags of salt themselves....

Sugests to me that Mike didn't properly understand all the 'fancy gadgets' he was paying for....

My 2000 E46 coupe would warn me if the pressure dropped more than 3 PSI with a Yellow light and a single warning noise, if it detected 5 PSI or sudden pressure loss would show a Red light and a repeating warning noise. It also worked perfectly letting me know when to add more air, I don't know if they have changed them now to a different type.

What kind of system is discussed in the article? Two different system are discussed, since BMW is offering:
1. Tyre Presssure Warning, a 1st generation indirect TPMS - so using difference in circumferential speed measured with the ABS - that is fitted as STANDARD.
2. Tyre Pressure Monitoring, a direct TPMS that is offered as an OPTION and that is actually measuring pressure and temperature (see BMW website).

The complaint is in regard to the system 2. and the explanation given is matching system 1. Seems inconsistent to me. The statement that the direct system as used by Renault, etc... would have detected I can't understand consequently either, since if it is the optional system it is a similar system.

As stitch already mentioned TPMS is not a replacement of doing normal 'tyre maintenance', since in particular in a diffusion case you are already running significant underpressure for quite some time before a warning can be issued.

It is true that among others VAG are adopting systems based on using ABS signals for their TPMS however for their latest cars this is 2nd generation indirect TPMS which is much, much more sophisticated than 'difference in rolling circumference'. As matter of fact these systems are capable of detecting diffusion (simultaneous deflation of all tyres over time) as well.

I have a new Series1 M Sport that has TPMS and I don't think Mike has read his hand book. The system is a pressure monitoiring system, not a tyre wear monitoiring system. Pressures and wear should be manually checked on regular basis, once a week is recommended. However for the TPMS to work properly, you need to go into the iDrive system. After checking/adjusting the pressures you need to INITIALISE the system, shown in the iDrive instructions, this takes about 1 minute. The TPMS will then sense if one or more of the tyre pressures has dropped or indead there is a punture. Remember that Run Flat Tyres are fitted to BMW's, so it is perfectly safe to drive at a sensible speed and distance until a new tyre can be fitted. All this is described in the comprehesive handbook.

Shouldn't Mike, and Auto Express, be more concerned with the fact that the inside of the tyres had 'worn unevenly and badly' whilst there was 'plenty of tread on the outside'? This could potentially indicate a wheel or chassis misalignment issue, which is likely to be far more significant than the perceived problem with his car's TPMS.

My new 5-Series was delivered with all four wheels so far out of alignment that the car almost went round in circles if you let go of the steering wheel; I'd have been in the same boat with tyre wear later on if I hadn't pressed my dealer to carry out an immediate alignment check and make the necessary adjustments all round. (They did, and the problem was eventually corrected.) I'd suggest Mike takes the potential alignment issue up with his dealer as well.

Shouldn't happen on a new BMW, but it clearly does.

This what happens when people buy into and believe the "Badge" and not real experience or common sense.
My wife's car has TPMS, the one that actually detects a difference in pressure of individual tyres, (type 2 as mentioned below), however that doesn't prevent me from checking them for her on a regular basis, the best safety systems money can buy are no good if your tyres are in poor condition, because at the end of the day they are what actually connects your car to the road.

Maybe I am being the elephant in the room here but, what about the tyre wear? This is not a function of TPMS and clearly the owner has responsibility for checking that.

With TPMS did anyone think of letting a tyre down manually at the garage to validate functionality. There seems to have been a lot of effort spent by this magazine wasting the AA's, BMW's and it's own time over an incompetent owner. Due diligence Auto Express in future please.