False economy.
Discussion
Read an article in a motoring magazine about driving like an IAM and getting better fuel consumption, he was getting between 32-38 mpg from a 2ltr car.
Sounds good, unfortunatly when he put his car in for a service he needed rear discs, they had rusted away due to gentle braking.
The machanic said gentle braking tends to just use the front brakes so all this careful driving meant he only got 30,000 miles out of his rear discs, the machanic said he could have expected more than twice that milage if they had`nt rusted.
So if rear discs cost £300 fitted and you put that onto 2 years fuel, i work that out at about 10p a litre or 10% worse fuel consumption.
That brings his figure down to 29-34mpg.
Sometimes you just can`t win.
Sounds good, unfortunatly when he put his car in for a service he needed rear discs, they had rusted away due to gentle braking.
The machanic said gentle braking tends to just use the front brakes so all this careful driving meant he only got 30,000 miles out of his rear discs, the machanic said he could have expected more than twice that milage if they had`nt rusted.
So if rear discs cost £300 fitted and you put that onto 2 years fuel, i work that out at about 10p a litre or 10% worse fuel consumption.
That brings his figure down to 29-34mpg.
Sometimes you just can`t win.
gridgway said:
interesting, is this verifiable or more urban myth-like. It seems a bit strange that the driver managed to brake so gently that he didn't generate enough pressure on the rears to scrub off the rust on each drive.
Graham
Yes I agree, it does sound suspicious. Perhaps a more likely explanation is that the car was not in regular use, and this had caused the brake disc corrosion?
Best wishes all,
Dave.
I would copy out all of the letter but i`m stuck for time but if you get hold of ,
Motoring and Leisure May 2006, the CSMA magazine the letter is on page 21, "Take a break" by David Beale Washington Tyne and Wear.
Seems on the level to me.
>> Edited by slowly slowly on Thursday 11th May 19:26
Motoring and Leisure May 2006, the CSMA magazine the letter is on page 21, "Take a break" by David Beale Washington Tyne and Wear.
Seems on the level to me.
>> Edited by slowly slowly on Thursday 11th May 19:26
Even a light application of the brakes is enough to put pad in contact with disc and hence scrub the rust off, so it smells a bit fishy to me. Most FWD cars do have a front biased brake balance (hence the heavier wear) but I'm not aware of any that use the rears at a later stage of the braking process.
John
>> Edited by goliath on Thursday 11th May 20:16
John
>> Edited by goliath on Thursday 11th May 20:16
slowly slowly said:
The machanic said gentle braking tends to just use the front brakes so all this careful driving meant he only got 30,000 miles out of his rear discs,
Sounds like rowlocks to me, the rear brakes do proportionally more work under gentle braking, and in any case you can't avoid using the brakes in day to day driving even if you are driving *really* economically; you'd only have to use them once every few days to keep the discs clean. Anyway, 30 mpg is nothing special is it? So it's unlikely he was doing anything particularly unusual.
sounds a bit like CSMA twaddle to me. [light-hearted gross generalisation coming] it's an ok mag, but my father-in-law reads it, so it's for old duffers :-))
No offence intended to either CSMA members or old duffers (I'll certainly be one of those before too long and I dont expect my membership application for the CSMA to be accepted now!).
Graham
No offence intended to either CSMA members or old duffers (I'll certainly be one of those before too long and I dont expect my membership application for the CSMA to be accepted now!).
Graham
TripleS said:
interesting, is this verifiable or more urban myth-like. It seems a bit strange that the driver managed to brake so gently that he didn't generate enough pressure on the rears to scrub off the rust on each drive.
Graham
Yes I agree, it does sound suspicious. Perhaps a more likely explanation is that the car was not in regular use, and this had caused the brake disc corrosion?
Best wishes all,
Dave.
Just looking at the brakes on my mothers car says it all. Used every day, but even the bloody fronts had corrosion over them! 40mph everywhere stylee and starts slowing down early enough to let rolling resistance and wind drag slow her down!
Dave
Here is the letter.
TAKE A BRAKE.
I was particularly interested by Tony Simpsons letter of the month(March page 10). I have adopted that tencnique for most of my four decades of driving. However i have found the savings in fuel consumption are cancelled out by the effect on the rear brakes.
I ran a Vauxhall Carlton 2.0 for nine years and averaged 32mpg consistently overall with 38mpg possible on high speed European motorway trips. I thought that was pretty good for a large 2.0 saloon.
It was bought at a local auction with 88.000 miles on the clock and at 106.000 miles my local independant garage advised me that the rear discs needed replacment which seemed reasonable. It seemed less reasonable when they needed replacing again at the MOT test 30.000 miles later.
They had passed on the dynomometer, but failed a visual inspection as they were badly corroded. The cause- lack of use!
There is a pressure valve between front and rear brakes and gentle braking only involves the front discs(which incidentaly never needed replacing in the 60.000 miles i owned the car). If you never brake hard the rear discs gently rust away!
According to the garage rear discs are more trouble that they are worth and i`m inclined to agree. We don`t all go charging down Alpine passes on a regular basis after all.Mind you, the rear slave cylinders on many an old banger i`ve owned used to seize up as well, but they were less costly to repair.
For a while after this i would hurtle along downhill slip roads and brake at the last minute to ensure the rear brakes got a good workout, but i found it rather nerve-wracking and have reverted to my old style which is much more relaxed.
I don`t know what the answer is; going out occasionally to give the brakes a good thrashing may be fun but defeats the object surely?
David Beale Washington
Tyne & Wear
Phew.....
>> Edited by slowly slowly on Tuesday 16th May 18:22
TAKE A BRAKE.
I was particularly interested by Tony Simpsons letter of the month(March page 10). I have adopted that tencnique for most of my four decades of driving. However i have found the savings in fuel consumption are cancelled out by the effect on the rear brakes.
I ran a Vauxhall Carlton 2.0 for nine years and averaged 32mpg consistently overall with 38mpg possible on high speed European motorway trips. I thought that was pretty good for a large 2.0 saloon.
It was bought at a local auction with 88.000 miles on the clock and at 106.000 miles my local independant garage advised me that the rear discs needed replacment which seemed reasonable. It seemed less reasonable when they needed replacing again at the MOT test 30.000 miles later.
They had passed on the dynomometer, but failed a visual inspection as they were badly corroded. The cause- lack of use!
There is a pressure valve between front and rear brakes and gentle braking only involves the front discs(which incidentaly never needed replacing in the 60.000 miles i owned the car). If you never brake hard the rear discs gently rust away!
According to the garage rear discs are more trouble that they are worth and i`m inclined to agree. We don`t all go charging down Alpine passes on a regular basis after all.Mind you, the rear slave cylinders on many an old banger i`ve owned used to seize up as well, but they were less costly to repair.
For a while after this i would hurtle along downhill slip roads and brake at the last minute to ensure the rear brakes got a good workout, but i found it rather nerve-wracking and have reverted to my old style which is much more relaxed.
I don`t know what the answer is; going out occasionally to give the brakes a good thrashing may be fun but defeats the object surely?
David Beale Washington
Tyne & Wear
Phew.....
>> Edited by slowly slowly on Tuesday 16th May 18:22
Gentle braking doesn't "only involve the front brakes" unless your brakes are defective. If the brakes are working correctly the rear brakes do proportionally more work under light braking and the fronts do more under heavy braking. Even if you are driving very gently (and 30 mpg is nothing special) you'd still use the brakes enough to clean the rust off.
"If you never brake hard your discs gently rust away" - rubbish!
However, what about the moving brake test. That is more than enough to use the brakes, and stop them "gently rusting away" (the more I read that the more I laugh).
Or is the moving brake test something that people only learn to do to pass their IAM test, then decide they know best, and stop doing it.
..gently rust away....stop it ,please.
However, what about the moving brake test. That is more than enough to use the brakes, and stop them "gently rusting away" (the more I read that the more I laugh).
Or is the moving brake test something that people only learn to do to pass their IAM test, then decide they know best, and stop doing it.
..gently rust away....stop it ,please.
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