Prius Failed Mot Today On Rear Brake Efficiency

[valmiki]

Hot off the press, just had a call from the dealer, car was in for a minor service today and MOT. The car (Prius III, 2010 67k miles) failed on rear brake efficiency. They want to charge £46 to 'investigate'. Unfortunately they've only just got hold of me so can't do anything today, I'm going to drive the car home tonight and bring it back in tomorrow morning. I'll know more when I speak to them when I go pick the car up.

Any bets on it's just the cable needs tightening? And this just as the extended warranty is running out (they have already informed me that it's probably not covered).

Wish me luck!

[ToyotaAuris]

maybe pads?

[valmiki]

They'd better not charge me for diagnosing that!! lol

[Grumpy Cabbie]

My rear discs and pads were replaced at 60k miles. They might have managed a few thousand more, but I like to be safe.

I actively look after my car and as such have never failed an MOT or had an advisory, despite very hard miles.

[valmiki]

You'd think they could have found that out when doing the service. As it turns out the MOT wasn't done until late afternoon, guess they just didn't have time for any such repairs. Anyway, car back in in the morning so we'll see. Thanks GC guess that will be the answer tomorrow :-)

[johalareewi]

And this just as the extended warranty is running out (they have already informed me that it's probably not covered).

The Toyota Extended Warranty has MOT failure cover.

http://www.toyota.co.uk/insurance-and-warranty/extended-warranty

MOT test cover

If your vehicle fails its MOT test, a Toyota Extended Warranty protects you against unexpected repair bills. As long as the vehicle is repaired and passes, your Extended Warranty will pay for repairs or replacement of covered parts including labour, up to the vehicle's purchase price. All you have to pay is the original MOT test fee and the first £10 of any repair costs covered by the Toyota Extended Warranty.

[valmiki]

Hi, just had a phone call from the dealer - as GC predicted, needs new pads and discs. One wonders why they couldn't have diagnosed that yesterday, but I'm guessing they were just too late and busy to do it then so bumped it to today. Pretty sure it's not covered by the MOT test cover as it's consumables, and not a covered part which kind of makes the the whole 'MOT test cover' redundant (!)

[Grumpy Cabbie]

Brakes wear out. No warranty will cover them for wearing out or age related wear.

[valmiki]

Also more common than other cars for my year Prius (to fail on rear brakes)

http://good-garage-guide.honestjohn.co.uk/mot/toyota/prius

Bit of an eye opener!

[FROSTYBALLS]

Years ago we had a Honda that failed its first MOT on the front suspension bushes, and we had MOT cover as part of the extended warranty. The dealer said it was down to wear and tear, but when I looked at the 'covered parts' section of the policy, suspension was one of the covered parts. Spoke to Honda UK who said wear and tear had nothing to do with the failure - and the bushes were replaced for the cost of the £10 excess, instead of the £125 quoted cost from the dealer (1997 prices).

So I would say if there is anything else wrong with the braking system apart from new pads and discs being required, your MOT cover should be valid.

[PeteB]

I must admit this makes my blood boil!

When everyday cars started getting front disc brakes in the 1960s and 70s (as opposed to drum brakes all round), it was almost unthinkable that the discs would EVER need replacing, whereas the pads were often replaced every 12,000 miles.

The main reason many discs are replaced is because they rust if not used daily. My previous Mk 1 Prius was used daily until nearly 90,000 miles and the discs showed no measurable wear, and the pads just 5% gone (even though it was always parked outside). (I made a point of maximising regenerative braking whenever possible which obviously helped).

I then had a year where a drove (someone else's) Prius minicab for a year, during which time mine only got used about 3 days a month. The disc pads sounded very scratchy each time I drove for the first few miles, and behold they wore down to minimum in just 7,000 miles!

I then drove the car daily for another 70,000 miles and the replacements were still hardly worn when I sold it at 9 years old with 163k on the clock.

I rather think that despite Toyota discs being rather expensive, they scrimp on the mix of metals that resist rusting, so that they need replacing more frequently (but not just Toyota's).

[Grumpy Cabbie]

Don't Toyota use softer metals on the UK/EU model discs to give the brakes more 'bite'? Apparently European drivers prefer that. The US Prius (even in taxi use) go well into the 100k miles before needing replacement. I'm sure this was checked previously but the part numbers for front discs are different. Their brakes however, are meant to be duller.

But brakes and tyres and fuel economy too all depend on the use of the car. No point comparing brake or tyre wear on a car used gently on A roads and motorways where they could drive for 40 miles without even touching their brakes, against an enthusiastically driven taxi driven in town on a busy Saturday night.

I got 30k out of my front pads and 60k out of the front discs and the rear pads. For me that is exceptional. To a motorway cruiser or hypermiler it would be chronic.

Keep your brakes and tyres in good order and have less stress in your life.

[valmiki]

Was charged £200 for new discs and pads. Happy to pay for that every 60k :-)

[Whitewagon]

The main reason for high disc wear in modern cars is down to health and safety regulations. Pads used to have high levels of asbestos in them but legislation now prevents that being used. The friction materials now used are much harder and often contain metals, manufacturers often use softer metal for the disc to compensate thus wearing them out more frequently.

[Grumpy Cabbie]

The main reason for high disc wear in modern cars is down to health and safety regulations. Pads used to have high levels of asbestos in them but legislation now prevents that being used. The friction materials now used are much harder and often contain metals, manufacturers often use softer metal for the disc to compensate thus wearing them out more frequently.

But in the US where asbestos is also banned they appear to use a harder metal in their discs, hence why they last significantly longer than ours.

One of the early selling points to the Prius to me was reading about the amazing brake pad and disc life, yet when I got one my pads wore out in 30k miles (good but not the 100k that they get in the US). A number of other European members were getting short disc and pad life compared to US members. Initially it was put down to differing traffic conditions, smaller roads and streets etc, which sounds feasible. But the contrast was too great and someone checked the part numbers and the US and EU discs are different.

Saying that, the gen2 US Prius used to have drums at the rear whereas the UK and EU models always had discs front and rear.

Personally I don't mind my discs lasting 60k miles if it means I get great braking - which I do. Anyone else experienced the emergency brake assist on their Prius? Now that brakes HARD :)

[PeteB]

On the Toyota Hybrids, pad/disc life seems to depend a lot on 2 things:

1. type of driving; as GC says, taxi use around town is very different to someone on a motorway all day
   
2. number of days a month the car is driven

Type of driving also includes how much the driver manages to use only regenerative braking to slow down (helped on the Gen 3 2010 onwards cars having the ECO monitor - getting the bar (or needle) to the left/button of the GEN scale maximises regen, pressing the brake harder uses the friction brakes as well). There are plenty of examples of Prius brakes ni the UK lasting well over 100,000 miles.

My 2nd Gen 1 Prius would almost certainly have done had I not had a year where I hardly used it and they wore very quickly. I make a point of planning ahead to use regen as much as possible and stay off the 'real' brakes.

A moderator on the Yahoo Prius-UK group is selling his 2004 Prius with 100k on the clock and plenty of life left in his original brakes (he's buying a Gen 3 Prius).

My current Gen 3 Prius was reported on the dealer's Visual Safety Report to have 6mm remaining on all pads at 34,000 miles last November (although I confess I have no idea what they started with or what the minimum is).

The second point refers to the apparent excessive rust caused when the car is not driven almost daily (presumably parking outside makes it worse). I come back to my 2nd Gen 1 Prius, which was reported to have over 90% disc/pads life remaining at nearly 80k, after 4 years high mileage daily use, and they wore them out completely in just 7,000 miles for a year where the car was used very infrequently. The replacement discs were still in good shape when I sold the car at 9½ years old with 163k on it, after the remaining use was again high mileage.

With today's technology, how hard could it be to make discs that do the job and don't rust so easily?

[kithmo]

Pads usually start at 10mm thick and should be changed when they get below 2mm, so you're only half way there Pete, good for another 34K miles.

Pads usually outlast the discs on most cars these days.

[PeteB]

Thanks Keith - be interesting to see - looks like they're not doing as well as my Gen 1 Prius then.

[valmiki]

sorry to resurrect this one, but is there a method or procedure of ''using the rear brakes whilst driving? just so i can rub off any rust that may have collected when standing in the damp

[Cyker]

Other than actually braking, not really (And often you have to brake fairly hard for the rear discs to get any actual bite!).

I'd recommend a quiet down-hill as an optimal place for such a thing.

On some cars you could use the handbrake lever to scrub the rear discs, but most cars these days have a separate drum-brake for the handbrake on the rears so this is not a guarantee (Heck, some cars don't even have proper handbrakes these days!).

[kithmo]

The gen 3 doesn't have a drum in the rear for parking brake.

[valmiki]

I thought that a hard brake would do the job, doesn't it have to be in neutral?

[timberwolf]

I thought that a hard brake would do the job, doesn't it have to be in neutral?

Nope. Rear brakes are friction only. The Front brakes are regeneration and friction. Most of the braking force is to the front. Maybe you could drive around in reverse for a time to even things out :-)

[Grumpy Cabbie]

Doesn't putting the car in neutral over 45 mph potentially cause damage to the hybrid motors? I'm sure I've read that by doing this you can cause one of them to overspin. I guess once or twice you might get away with it, but knowing my luck I'd try it once and it would go bang - expensively.

[PeteB]

there was a consensus among the engineer members on the Yahoo Prius-UK group some years ago that 20 mph in N with relatively gentle braking was enough to clear surface rust off the front and rear discs, but a normal journey will do it anyway on Gen 1 & 2 Prius as the regen stops at or below 7 mph. On my Gen 3 it seems to work at a lightly lower speed, but not entirely sure.