|
The problem with the internet is the mass of rubbish portrayed as gospel truth. The style and substance of postings which indicate modest intellect and even more modest grasp of matters physical and chemical often spread such rubbish. Readers with a similar level of intellectual ability, or even those with a good level of intellect but little scientific qualification or ability (e.g. Prince Charles - merely 5 'O' levels and no science 'A' levels) will have difficulty in discriminating between rubbishy and reliable scientific info.
Here is what strikes me as reliable info re brake pads - it makes sense to me. I have always found 'quora' to be pretty useless.
textar-professional.com/textar-training-center/slo.../
|
|
Agree with you there John F regarding the accuracy of Internet information. I looked at both of those sites yesterday and can't see why a bit of gas is such a problem on a everyday passenger car.
I've seen quite small pads with a groove and much larger ones without.
|
|
|
The problem with the internet is the mass of rubbish portrayed as gospel truth. The style and substance of postings which indicate modest intellect and even more modest grasp of matters physical and chemical often spread such rubbish. Readers with a similar level of intellectual ability, or even those with a good level of intellect but little scientific qualification or ability (e.g. Prince Charles - merely 5 'O' levels and no science 'A' levels) will have difficulty in discriminating between rubbishy and reliable scientific info.
Here is what strikes me as reliable info re brake pads - it makes sense to me. I have always found 'quora' to be pretty useless.
textar-professional.com/textar-training-center/slo.../
You don’t make your own candle burn brighter by peeing on other people’s.
|
|
|
|
If you google "why do brake pads have a groove in them" the quora site alleges that the resin gives off gas when it is heated. Sounds complete rubbish to me.
Me too. I suppose the resin (presumably a binder holding the friction material together) might just break down and release a few molecules when hot. If the suggestion is that this small amount of gas needs to escape so that braking is not affected, I would suggest that on a car doing 60mph (for example) the outer parts of a disc will be meeting the pad at around 20 metres a second, and far more air is likely to get entrained.
Hogwash IMHO, tho possibly worth consideration in extreme conditions.
|
|
I'm slightly confused by this, because if you read this site, it makes mention of a build up of gas between disc and pad as one factor of brake fade (as well as brake fluid boiling), but later says that passengers cars, trains, aircraft have no holes through the faces of their discs because there is no gas to vent.
en.wikipedia.org/wiki/Brake_fade
Some of you may have been on trains and recall that smell when the brakes are being applied hard. Something must be being produced because it's airborne and travelling between the brake system and your nose.
I've certainly experienced brake fade on a Rover SD1 where the discs seemed to be underspecified for the weight of the car. That would show up as a firm brake pedal but seriously reduced stopping ability, together with a burning smell.
I have to add that I was young and the brakes may not have been maintained in peak condition, but there was mention of it in the car magazines of the time.
Edited by corax on 22/09/2018 at 18:11
|
|
Holes in disks ? See brembo
www.brembo.com/en/company/news/brembo-perforated-d...g
|
Holes in disks ? See brembo
www.brembo.com/en/company/news/brembo-perforated-d...g
Yes, there's a lot of rubbish posted on the Internet, posted by, er, well-known manufacturers of brake components .... ;-)
|
Holes in disks ? See brembo
www.brembo.com/en/company/news/brembo-perforated-d...g
Yes, there's a lot of rubbish posted on the Internet, posted by, er, well-known manufacturers of brake components .... ;-)
Perfectly illustrates the point I was making. A most amusing example of automotive quackery as far as the ordinary motorist is concerned.
|
Perfectly illustrates the point I was making. A most amusing example of automotive quackery as far as the ordinary motorist is concerned.
but but, don't you want drilled and grooved rotors, sorry, brake discs, with labelled racing pads and bright yellow/red/blue/gold calipers shining crassly so everyone knows you're a street racer and hear the horrid noises these pointless things make as you approach ? :-)
Next thing you'll be telling us you haven't had a decat (nothing to do with unleasing your spaniel when the neigbours moggie pees on your vegetable patch) or had a straight through exhaust fitted, badly, so it sounds like you're doing 120mph when Mrs Jones goes past you in almost total silence in her Micra.
I like the go faster rubbish these people pay ridiculous money for, soon as you clock the junk or hear the ruined exhaust or imitation turbo dump valve you know to give them a wide berth.
|
|
|
|
Some of you may have been on trains and recall that smell when the brakes are being applied hard. Something must be being produced because it's airborne and travelling between the brake system and your nose.
Train brakes certainly have a noticeable smell, which I believe is caused by the use of phosphor-bronze brake 'pads'. When train speeds crept up above 100mph It became necessary to move on from the old steel or cast-iron brake blocks working on wheel rims. When you consider what it takes to stop a train of up to 500 tons in a reasonable distance, special materials are called for. Now, disk braking on trains is so effective that wheels easily develop flat spots because of skidding.
I think in the 'old days' when brake fade on cars was a common experience, braking surfaces were mostly based on asbestos, which was abandoned long ago for toxicity reasons.
Edited by Andrew-T on 22/09/2018 at 19:19
|
|
I was astonished by how long the brake pads on my VW Up lasted.
|
|
|
Some of you may have been on trains and recall that smell when the brakes are being applied hard. Something must be being produced because it's airborne and travelling between the brake system and your nose.
Train brakes certainly have a noticeable smell, which I believe is caused by the use of phosphor-bronze brake 'pads'. When train speeds crept up above 100mph It became necessary to move on from the old steel or cast-iron brake blocks working on wheel rims. When you consider what it takes to stop a train of up to 500 tons in a reasonable distance, special materials are called for. Now, disk braking on trains is so effective that wheels easily develop flat spots because of skidding.
I think in the 'old days' when brake fade on cars was a common experience, braking surfaces were mostly based on asbestos, which was abandoned long ago for toxicity reasons.
The only significant brake fade I have ever experienced was in P2 (16) and P4 (75) Rovers with front drum brakes.. - red hot drums and smoke. down a Scottish mountain. The materials were undoubtedly asbestos..(late 1960s early 1970s).. 2 tonnes of car with drum brakes made for entertainment..Never had it with disks,
|
|
Experienced brake fade once, coming down a Welsh hill with a caravan on the back. Firm pedal, but no braking. That was with relatively new Moprod brand pads from Halfords. They were quickly replaced with a more recognisable name.
Boiled the brake fluid once, but that was due to a fault. Pedal hits the floor.
|
|
Used to get brake fade on my old Mustang, which was hardly surprising, as a 5.7 litre flyer with unservoed drum brakes all round wasn't the best of stoppers.
Never had fade but my ex plod driving school Rover 827 used to warp discs regularly, and had been though umpteen sets in its plod life, as with the other Rover noted above, brakes simply too small for the considerable weight and speed capability of the car, i don't think the Honda Legend with the same engine had this problem.
Lots of artic trailers are returning to drum brakes though, no difference in brake performance, but the operators are fed up to the back teeth with the trouble trailer disc brakes can be whilst the drums give little trouble if any.
|
|
Apologies for not getting back before now but been doing more important things since Friday such as driving back from Scotland, picking the Cat up from the cattery, tidying the garden, walking the dog etc.
With regards to gasses. Most compounds that exist on planet Earth (and elsewhere considering that the laws of the universe are considered - excuse the pun - to be universal) give off gasses when heated or burned The materials that brake pads are made from certainly give off gasses.
As for the need for slotted or drilled discs on normal road cars personally I cannot see the point. You don't get the brakes hot enough for long enough normally to have an issue. The only time I have had brake fade and ultimately a car full of smoke and little in the way of braking was a Triumph Spitfire that used the same small Lucas/Girling calipers and pads as JohnF's TR7. If they were inadequate on a Spitfire imagine how rubbish they are on a heavier car. That was on a long downhill run into Ashbourne in the Peak district. Things must have been very hot since the hubs, stub axles and bearings failed a few months later and were replaced under warranty together with the calpers and pads, good old BL, did we not love them.
Both my Caterhams were fitted with the same tiny Lucas/Girling caliper as standard and since the car was much lighter I managed with them for probably 25 years trying different front brake pads in an effort to improve braking, drive a tintop of today and experience better braking than a much faster Caterham and you soom feel the need to make improvements. I eventually fitted a set of fast road/trackday/racing calipers that are normally used on Civic Type R track cars on specially machined brackets. These calipers are 4 pots and use Volvo pads which are at least twice the area of the Triumph ones and the difference is truly astonishing. Using larger diameter discs (more leverage) the balance is now better as well, the rear was always overbraked since it used Sierra Cosworth calipers on Triumph discs. But I see no need to use drilled or slotted discs on the road since they will never get hot enough, if I was intending to use it on the rack again I may consider getting some slots added.
I agree there is lots of nonsense on the interweb but there is also lots of facts. The sites linked to above supply the facts regarding brake materials giving off gasses thus I don't feel the need to add more links that quote the same info.
I am a little confused over the info regarding the need for slots in pads since I have bought pads for several cars in the past (including the Caterham) that in some instances have had slots and in others no slots. I have never seen a pad with cracks in it but that does not mean it does not happen. The need for slots in the pads was one told to me probably 30 years ago now when I first started going on the track and it seemed genuine enough since roads pads had no slots and race pads did. Combine slots in the pads and slots on the discs and there is much greater opportunity for the gasses to escape.
One other fact to remember, disc pads are always in contact with the disc, there is no return spring in the calipers. The brakes will always be slightly warm and that is not a problem, they are designed like that. But the contact means that gasses can be trapped and as described to me all those years ago the slot allows those gasses more opportunity to escape.
|
I see no need to use drilled or slotted discs on the road since they will never get hot enough, if I was intending to use it on the rack again I may consider getting some slots added.
Normal road cars which need more brake cooling often use 'ventilated' discs, a disc sandwich with a central air gap. Pug 205s with the 1.6 or 1.9 injection engines had them, all other models had solid discs. No need for complicated holes or slots.
Incidentally, as a response to earlier posts above (from Wikipedia) :
Most brake pads are equipped with a method of alerting the driver when pads need changing. A common technique is manufacturing a small central groove whose eventual disappearance by wear indicates the end of a pad's service life.
Edited by Andrew-T on 23/09/2018 at 19:14
|
|
My Jag XJR suffered from brake fade when driven very hard. The brakes just weren’t up to the performance of the car. Still a fabulous car though. I did put aftermarket vented discs and Brembo pads on – which did improve matters a little but at the cost of refinement when braking at walking speeds (ie too much grab when coming to a halt.) I have no idea if the venting made any difference, however you very rarely (if ever) see front motorcycle discs without holes these days – I suspect it’s to disrupt the build up of a wegde of water in the wet over venting anything.
|
I suspect it’s to disrupt the build up of a wegde of water in the wet over venting anything.
With the pads being in constant contact with the disc there is very little oppportunity for braking to be affected by water when using discs. Ye olde drums would suffer badly after being driven in wet conditions when water entered the drums.
I suspect its more to do with fashion. Race bikes need them thus by fitting them on a road bike makes them kook racier.
Here is a good article auto.howstuffworks.com/auto-parts/brakes/brake-par...m which does suggest that drilling helps with wet dics. It also suggests that gassing is less trouble with modern brakes and that is probably true, if the brakes are ceramic. With organic friction materials gasses will still be produced.
|
Here is a good article auto.howstuffworks.com/auto-parts/brakes/brake-par...m which does suggest that drilling helps with wet dics. It also suggests that gassing is less trouble with modern brakes and that is probably true, if the brakes are ceramic. With organic friction materials gasses will still be produced.
Good article? You must be joking - I lost the will to live by page 5. I don't think Ms Deaton's American MA in Sociology qualifies her to write authoritatively about scientific matters, although she did seem to realise the concept of trapped gas was bo11ocks. Her prose reminded me of Pippa Middleton.......'
Because trucks are so big and heavy, their brake rotors are especially important brake parts.
It takes a lot of force to stop a truck.
Gosh, really?
|
|
From that article
''That's not because the rotors themselves don't last, but rather, due to the extra stress of stopping a truck, the truck's brake pads tend to wear out more quickly. If worn brake pads aren't changed early enough, they can cause damage to the brake rotors''
I won't comment on the second sentence because it's just too obvious for words, but as for truck pads wearing faster, what a load of cobblers, i'm on just over 102k kms in my current tractor unit and brake pad wear is available on the dash menu, currently 70% pad material left on axles 1 and 3 and 72% on axle 2, so should get a comfortable 200/250k kms (say 130k miles+) before changing @ 20% left..
From previous experience i normally get at least 2 sets of pads out of a disc.
|
With the pads being in constant contact with the disc there is very little oppportunity for braking to be affected by water when using discs. Ye olde drums would suffer badly after being driven in wet conditions when water entered the drums.
I suspect its more to do with fashion. Race bikes need them thus by fitting them on a road bike makes them kook racier.
Well, you obviously do not remember motorcycle brakes from the 70's/early 80s where you'd pull the lever in the wet and nothing would happen for a second or so until the pads finally cut through the film of water on the disk, then they'd grab and you'd crash. I do.
Edited by Avant on 24/09/2018 at 00:30
|
With the pads being in constant contact with the disc there is very little oppportunity for braking to be affected by water when using discs. Ye olde drums would suffer badly after being driven in wet conditions when water entered the drums.
I suspect its more to do with fashion. Race bikes need them thus by fitting them on a road bike makes them kook racier.
Well, you obviously do not remember motorcycle brakes from the 70's/early 80s where you'd pull the lever in the wet and nothing would happen for a second or so until the pads finally cut through the film of water on the disk, then they'd grab and you'd crash. I do.
In my beekeeping travels I occasionally travel through lying water and a small ford whose depth obviously varies withe the weather. If I don't try the brakes afterwards, I find the next time I apply the brakes nothing happens for 3-5 seconds until the water on teh disks is dispersed (solid pads and rotors)
|
In my beekeeping travels I occasionally travel through lying water and a small ford whose depth obviously varies withe the weather. If I don't try the brakes afterwards, I find the next time I apply the brakes nothing happens for 3-5 seconds until the water on teh disks is dispersed (solid pads and rotors)
I would get the brakes checked. If there is sufficient clearance between the diec and pads for water to prevent the brakes working for that amount of time there is a serious issue and your brakes are simply dangerous.
After driving trough deep water I still tend to dab the brakes (after checking behind of course) but its now years since I have found the brakes not working instantly. Had plenty of opportunity for this to happen in the Superb last week while we were in Scotland and in truth its simply not necessary to check.
But I will continue to do it out of habit, would hate to find I had been lulled into a complacency and find I have no brakes when I needed them.
|
In my beekeeping travels I occasionally travel through lying water and a small ford whose depth obviously varies withe the weather. If I don't try the brakes afterwards, I find the next time I apply the brakes nothing happens for 3-5 seconds until the water on teh disks is dispersed (solid pads and rotors)
I would get the brakes checked. If there is sufficient clearance between the diec and pads for water to prevent the brakes working for that amount of time there is a serious issue and your brakes are simply dangerous.
After driving trough deep water I still tend to dab the brakes (after checking behind of course) but its now years since I have found the brakes not working instantly. Had plenty of opportunity for this to happen in the Superb last week while we were in Scotland and in truth its simply not necessary to check.
But I will continue to do it out of habit, would hate to find I had been lulled into a complacency and find I have no brakes when I needed them.
The water is deep enough to cover the lower half of the disks. Clearance is fine.. in normal braking the brakes pads contact th dik within 1cm of foot brake travel.
|
|
Back in my youth you would have no brakes after washing the car. I think the last car I exprienced that on would be a Mk 2 Escort, ever since then never an issue, no bum clenching moments as you pull off the drive.
|
|
|
|
|
|
|
