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Post by mikebentley on Oct 15, 2019 15:26:14 GMT
FRONT BRAKE poor efficiency
Hi all I have rebuilt all my brakes ( new master cylinder slave cylinders and shoes)
I have been driving up and down the road to bed the brakes in and I keep adjusting them and the peddle is almost perfect now
But the front brake seems useless and the backs lock on and skid.
the front shoes that came with the car are as new with no oil on them (Could be 20 years old though)
the rear shoes I bought this year
I am thinking that the front linings could be to hard
Has anyone else had this problem please
Mike |
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Post by cdb15 on Oct 21, 2019 21:54:24 GMT
It could be that the old shoes linings have become glazed, if they look a bit shiny and feel very smooth. New shoes won't cost the earth, but if you want to try to salvage the old ones you could try gently cutting a diamond mesh pattern on them using a junior hacksaw. This will 'rough up' the surface to achieve a better grip with the drum. Make the saw cuts no more than about 1mm deep, diagonally across the lining from edge to edge, and spaced about 3-5mm apart. When you try them out, be prepared for anything - the brake might grab, or pull to one side etc, so make your first test run where you have plenty of space to swerve, and don't go too fast ! Bear in mind that if the shoes really are 20 years old, new shoes will have linings with 20 years worth of newer materials technology in them. You might also want to check your tyre pressures, as an over-inflated tyre will have less grip on the road and hence be more prone to locking up under braking.It could be that your front is too soft and your rears are too hard. Just a thought.
And an afterthought - check that the front shoes are properly fitted. I think I'm right in that the front is a twin-leading shoe set up, isn't it? If that's the case, then the shoes should 'follow' each other around the drum, as opposed to being symetrically fitted. If the front brake has two single-ended cylinders, then it's a TLS set-up. If it only has one double-ended cylinder then it's a single-leading shoe type. The leading edge of the shoe must face the direction of rotation of the wheel.
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Post by steve archer on Oct 24, 2019 15:33:35 GMT
under no circumstances must you cut the surface of the brake lining.the linings work most efficiently when they are shiny that's why new linings need bedding in.i would try changing the wheel cylinders if you havn.t already done so
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Post by mikebentley on Oct 24, 2019 16:30:28 GMT
thanks guys
I will be changing the front shoes. I'm sure that's all it is
as I said every thing is new except the front shoes.
I'm in the middle of doing the elecrics at the moment including fitting a small Nippon Denso alternator and will do the front brakes next then its put the hood back on and start using it
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Post by cdb15 on Oct 29, 2019 21:20:53 GMT
under no circumstances must you cut the surface of the brake lining.the linings work most efficiently when they are shiny that's why new linings need bedding in.i would try changing the wheel cylinders if you havn.t already done so Grooving drum brake shoes is as old as the technology. By putting in grooves, dust escape is facilitated, ingressed water is provided an exit channel, by reducing surface area the pressure applied to the wheel drum is increased, and allowing an air flow channel across the friction surfaces aids cooling, where heat build up is greatest (and is what causes glazing in the first place).
Grooving old shoes is not without risks, principally to be sure each side is as near the same as possible to avoid imbalance between the sides, but I stress: OLD shoes.
As I said, brake shoes technology has come on substantially since the 1970s, when the shoes material was the same right through the shoes, held in place using rivets. Today's shoes are multi-layer multi-functional bonded material, with outer layers designed to abrade the wheel drum on initial use, then secondary layers to aid bedding in, and deeper bulk to provide on-going braking efficiency. Properly installed, it's unlikely grooving would make any noticeable difference to the initial bedding in process, but grooving still aids in dust and water removal, and heat dissipation.
For similar reasons, high performance brake discs typically have holes in them.
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Post by stevenarcher on Nov 3, 2019 10:22:24 GMT
hi that's a new one on me never heard that before. but what I forgot to mention was you need to check the front flexi pipe because sometimes with age they can expand under pressure causing decreased effort at the wheel cylinders. steve archer.
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Post by cdb15 on Nov 3, 2019 23:12:49 GMT
... what I forgot to mention was you need to check the front flexi pipe because sometimes with age they can expand under pressure causing decreased effort at the wheel cylinders. steve archer. Yes, I overlooked this too - but it's a very important point with such old parts. Back in the day stainless steel braided flexi-pipes were only for the likes of race teams and Concorde, but today they are so affordable I wonder than anyone fits unbraided pipes any more. When I was sourcing parts for my Bug's brakes I replaced all the flexi-pipes with braided Goodrich ones, for the very reason you mention, and the cost was very modest. In my searching around I spoke with Goodrich and it's worth giving them a call as although they don't list any three wheelers as standard they make to order anyway, so getting a bespoke set for the whole car is no more expensive than for a listed car.
Having a 4-wheeler my set is different from the OP's, and Goodrich advised me to just get a set of pipes they make for the Mini from a dealer (£26 delivered for two front pipes from Moss Europe) as they make these in bigger batches so the unit price is a bit lower. So a single front pipe for the Bug would probably be less than this price direct from Goodrich. I'd recommend getting a set for the whole car though.
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Post by mikebentley on Nov 15, 2019 17:10:35 GMT
thanks guys
I have already fitted braided hoses
still doing electrics shoes will be changed soon and ill give fed back
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Post by mikebentley on Dec 10, 2019 8:46:13 GMT
UPDATE
New. Front Shoes fitted
Brake. Nice and balanced now
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Post by vannin on Dec 10, 2019 20:50:41 GMT
glad you got sorted eventually Mike.
as for braided hoses, i have bought a couple of cars in the past with them already fitted
and one of the first things i do is take them off and throw them in the bin.
total overkill on a road car and you can't check the internal condition of them
or clamp them without damaging them, real pain in the backside they are. what has me in stitches
is when people say "oh it's firmed up the pedal a treat" yeah and plain rubber flexi's would
have done exactly the same thing.
very similar to Bug owners who fit yokahama tyres (or similar) to the rear of their Bug. the
last thing on earth you want is really sticky tyres on the back of your Bug for obvious reasons.
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Post by cdb15 on Dec 11, 2019 14:45:04 GMT
as for braided hoses, ... total overkill on a road car and you can't check the internal condition of them or clamp them without damaging them, real pain in the backside they are. what has me in stitches is when people say "oh it's firmed up the pedal a treat" yeah and plain rubber flexi's would have done exactly the same thing. It's true that a NEW plain rubber hose will perform as well as a braid-supported one, because the rubber will be new and stiff. But the difference is in the longevity of the tubing. The braid not only protects the rubber from damage, it also supports it to prevent radial stretching which over time can lead to failure under pressure. So the braid prolongs the life of the hose and also helps maintain its performance to near-new level for much longer.
It is course true that you can't check the condition of the rubber underneath the steel braid, but the whole point of supporting the rubber is that by preventing the stretching there will be very little degradation of the outer rubber surface to check. Furthermore, if there were any mechanical damage to the hose, it would be easily and permanently visible on the braid whereas cuts to rubber will be extremely difficult to spot without a detailed bend test of every part of the tube to see if any crack opens up.
If you cut a "rubber" hose you'll find that it does actually contain its own textile braid - laminated into it internally during extrusion. This is done for the very same reason - to minimise radial stretching.
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Post by vannin on Dec 15, 2019 18:31:00 GMT
i'm not sure what is going to damage the flexi hose to warrant incasing it in metal braid for normal road use ?
i've been driving old cars for 40 years and owned 100's of them and i have never had a flexi damaged in any way.
as for longevity, i changed all 3 flexi hoses on a 1976 car a couple of years ago i owned and they were in really
good condition when i examined them closely, they were also dated on the side which was 10/1975 yeah the originals.
so over 40 years life out of a what £7.00 hose compared with what about £20.00 for a braided hose which you can't
clamp without damaging it and who or what is cutting these brake hoses ? ? ? never had or seen one yet cut, this is
just scare mongering, how long has the motoring world managed perfectly well with plain rubber flexi's ? a long time
braided hoses are designed for competition and motorsport use not for road use.
if you've got a psycho neighbour that you've fell out with then maybe fit these daft braided hoses just incase he goes
under your motor and trys to cut your flexi's, if you haven't then save some money and buy the proper rubber flexi's
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