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Brake efficiency  Rating:  Rating
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 Posted: Sat Nov 8th, 2008 12:10 am
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Spunkymonkey
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Wesley wrote: Afermarket parts are normally an upgrade to enhance vehicle performance.

Not as you portray in your posting,

Who in their right mind is going to downgrade a Ferrari from multiple pot calipers, to 1967 Mini shoes and cylinders?:?

Annually I Inspect a 1968 Jag, It has 4 pot calipers and vented discs on the braking system;) It also has an Electrically assisted power steering system fitted:P

ps; it also has an original "Discs" Sticker.;)

pps; Pot Kettle Black? what about Your Tyres?:P

Wes.



I know mods are normally upgrades, Wes, but David suggested that after-market fitments might make it impossible to use a manufacturer's figure as a "baseline" so I was making the point that mods that seriously lowered the designed efficiency should be grounds for failure. 

The suggestion of Mini drums on a Ferarri was just an extreme example to illustrate that point ;)  As for "who in their right minds..." - there are a hell of a lot of owners out there absolutely not in their right minds (though hopefully not quite that stupid!).... :P

My tyres are all new now btw - always planned to replace them as soon as it was legal to drive to a tyre shop.  Only budgets from Event but it IS a Daf so Bridgestones all round seemed a little OTT :D


Edited to add: I suspect the Events would let go of the road before I got anywhere near 100% braking!

Last edited on Sat Nov 8th, 2008 12:12 am by Spunkymonkey

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 Posted: Sat Nov 8th, 2008 12:06 am
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Wesley
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A lot of newer vehicles that we test can have over 80% total efficiency, but the one to take the biscuit this year was an old Bedford Doormobile;)

Outperformed an 05 C5 by a country mile.;)

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 Posted: Fri Nov 7th, 2008 11:55 pm
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KevG
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I Tested a Bike yesterday with over 100% brake efficiency.

 

kev

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 Posted: Fri Nov 7th, 2008 11:24 pm
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Wesley
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Mana: 
Afermarket parts are normally an upgrade to enhance vehicle performance.

Not as you portray in your posting,

Who in their right mind is going to downgrade a Ferrari from multiple pot calipers, to 1967 Mini shoes and cylinders?:?

Annually I Inspect a 1968 Jag, It has 4 pot calipers and vented discs on the braking system;) It also has an Electrically assisted power steering system fitted:P

ps; it also has an original "Discs" Sticker.;)

pps; Pot Kettle Black? what about Your Tyres?:P

Wes.


Last edited on Fri Nov 7th, 2008 11:34 pm by Wesley

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 Posted: Fri Nov 7th, 2008 10:44 pm
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Spunkymonkey
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David wrote:
Hi Joe,


With regards Braking Figures, I think the manufacturer works to standards of each model in standard factory specifications, some people change brake components like calipers etc for after market ones, I think based on what the market presents that it would or maybe impossible to have a standard to apply if VOSA tried to change what we already have, which they say is the "minimum standards and criteria to be met". which we have just recently had much discussion on.

It's worth noting that Braking systems in good working order produce efficiency's between 66 - 70%, these are consider high, although it is possible and some vehicles do produce higher than these figures, but when designing brakes, one would have to be careful because efficiency which is too high, i.e. 100% + would be considered dangerous.

David:D

Some fair points in there, David.  I totally appreciate it's not a Tester's place to set (or even sometimes query) policy from on-high but, given that a great many testers probably have more practical experience than those setting the policy, I'm interested in their views all the same :)

A few things I would query in the parts of you post I've quoted, though:

The Highway Code stopping distances ("A car in good condition, with godd brakes in good conditions blah-de-blah-de-blah....") base their actual stopping distance (ie: NOT the reaction part) on a decelleration of 0.66g - that's 66% braking efficiency.  So, that would tally with your range for "good" brakes. 

However, those stopping distances were first published in the Highway Code in 1946 and haven't been updates since.  I would sincerely hope that any car produced recently should have better brakes than anything from 1946!  Having experienced 66% brakes in the Daf, I shuddr to think what the "minimum requirement" of 50% would be like in use!

As for modifications / aftermarket parts etc.  That's a reasonable enough comment but, surely, any aftermarket changes that significantly reduce the braking performance should be discouraged - if not made downright illegal?  Taking a brand new Ferarri and fitting a set of Mini drum brakes to it would have a good chance of hitting the 50% required - but would be bloody dangerous!  Since there's no other way (short of accident investigations) to spot inappropriate mods or sub (manufacturer's) standard parts, wouldn't the annual (supposedly) safety inspection be the best place?

They already publish for emissions because that's "important to save the planet" - surely being able to stop as fast (or at least nearly) as the makers designed when some eejut runs out in front of you is important too?

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 Posted: Fri Nov 7th, 2008 09:16 pm
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David
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Spunkymonkey wrote: Ok, this doesn't really come under regulation discussions - but it's not really a "pass or fail" issue either.  If a MOD would like to find the most suitable place for it then I'd be grateful!  I'm just curious to hear what you guys think...

I've just replaced the front brake cylinders and shoes on our Daf.  It passed its MOT about 3 months ago, including a decelerometer test for the brakes (can't RBT the backs because of the belt drive).  The decelerometer showed about 60% service brake - comfortably above the minimum - but not exactly confidence inspiring on the road compared to modern systems.

Once it went into use I noticed that the fluid was going down (slowly but steadily) so, knowing that the backs were ok and with no leaks elsewhere, I splashed out on the £30 or so for new fronts.  Having fitted them today, I found that both front cylinders were leaking (not badly enough to show signs outside the drums) and the difference after replacing is startling.  I suspect that the self-lubricating (anti-squeal???) shoes that were in there had something to do with it:dude:

Anyway, my question is this:  Given that the 60-odd % it had before was road legal - and would be a pass for a modern car capable of 2 or 3 times the Daf's speed - how do you guys feel when you have to pass (and advise?) a car that you KNOW is well below par and you KNOW that the chances are the owner won't get the work done (and may well be driving it like a nutter)? 

Now that everything's available on the computer, would there be a case for having pass levels for modern brakes based on manufacturer's figures?  Surely if they can provide emmissions figures for everything, they could do the same for something as fundamental as brakes?


Hi Joe,

you wrote; Anyway, my question is this:  Given that the 60-odd % it had before was road legal - and would be a pass for a modern car capable of 2 or 3 times the Daf's speed - how do you guys feel when you have to pass (and advise?) a car that you KNOW is well below par and you KNOW that the chances are the owner won't get the work done (and may well be driving it like a nutter)? 

Now that everything's available on the computer, would there be a case for having pass levels for modern brakes based on manufacturer's figures?  Surely if they can provide emmissions figures for everything, they could do the same for something as fundamental as brakes?


I say, we can't put the country to rights, no matter how anybody tries. I would like to say tho, the roller brake tester is measuring the efficiency of your vehicles brakes with a calculated amount of weight added, known as the brake test weight, the decelerometer is measuring the deceleration of your vehicle, not the brakes, in saying this, there is a formula to compare both the roller brake test results with the decelerometer results, which are consistant.

If any tester reads this, compare your calculated brake test results from the roller testing, then do a decelerometer test, you will never get the same efficiency result?

With regards Braking Figures, I think the manufacturer works to standards of each model in standard factory specifications, some people change brake components like calipers etc for after market ones, I think based on what the market presents that it would or maybe impossible to have a standard to apply if VOSA tried to change what we already have, which they say is the "minimum standards and criteria to be met". which we have just recently had much discussion on.

It's worth noting that Braking systems in good working order produce efficiency's between 66 - 70%, these are consider high, although it is possible and some vehicles do produce higher than these figures, but when designing brakes, one would have to be careful because efficiency which is too high, i.e. 100% + would be considered dangerous.

David:D

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 Posted: Fri Nov 7th, 2008 07:05 pm
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Spunkymonkey
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Mana: 
Ok, this doesn't really come under regulation discussions - but it's not really a "pass or fail" issue either.  If a MOD would like to find the most suitable place for it then I'd be grateful!  I'm just curious to hear what you guys think...

I've just replaced the front brake cylinders and shoes on our Daf.  It passed its MOT about 3 months ago, including a decelerometer test for the brakes (can't RBT the backs because of the belt drive).  The decelerometer showed about 60% service brake - comfortably above the minimum - but not exactly confidence inspiring on the road compared to modern systems.

Once it went into use I noticed that the fluid was going down (slowly but steadily) so, knowing that the backs were ok and with no leaks elsewhere, I splashed out on the £30 or so for new fronts.  Having fitted them today, I found that both front cylinders were leaking (not badly enough to show signs outside the drums) and the difference after replacing is startling.  I suspect that the self-lubricating (anti-squeal???) shoes that were in there had something to do with it:dude:

Anyway, my question is this:  Given that the 60-odd % it had before was road legal - and would be a pass for a modern car capable of 2 or 3 times the Daf's speed - how do you guys feel when you have to pass (and advise?) a car that you KNOW is well below par and you KNOW that the chances are the owner won't get the work done (and may well be driving it like a nutter)? 

Now that everything's available on the computer, would there be a case for having pass levels for modern brakes based on manufacturer's figures?  Surely if they can provide emmissions figures for everything, they could do the same for something as fundamental as brakes?

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