Urgent - Serious Brake Failure

grantwils · Post by **grantwils** » Mon Aug 27, 2007 6:48 pm

2 fast straights into tight corners = very serious brake fade... with brand new pads

I had the bike serviced and MOT'd on Wednesday and everything was OK. Had the front brake pads renewed and thought something was strange with them.
Decided to take the twisties home from work tonight and nearly had a serious off. I noticed the front brake leaver was very firm and lock up about 1/2 to 3/4 of the way to the handlebar. After the first two long straight into tight corner I approached the next corner and the lever came all the way back to the bar and wasn't doing anywhere near enough work to slow me to a speed I was comfortable getting round the corner with.
I had plenty time to think about what was about to happen and with a serious amount of 'oh f*ck' inside my helmet I made sure I didn't get target fixation with the stone wall at the side of the road and got round the corner. On the next straight I was testing the brakes and found I could accelerate from about 2000rpm in third with the brake lever pulled all the way back to the bar.

Does anyone know why this is happening? My thoughts are that either they've put on poo quality pads or they've not been bled properly.

I asked my dad who's a bit more mechanically minded than me and of course he's just telling me to go out and get new pads, calipers, discs, master cylinder etc coz he doesn't want anything happening to me he'll pay if I can't afford it - I'd prefer him to save his pennies.

Grant · Post by **Grant** » Mon Aug 27, 2007 7:59 pm

New brake pads need to be bedded in before they work properly, but the lever to the handle bar scenario sounds like the brakes haven't been bled properly.

Post by al » Mon Aug 27, 2007 8:02 pm

Sounds like a combination of brand new pads that are not bedded in and air in the hydraulic system.

On bikes with 2 front disks I only ever fit new pads (to an existing disk) to one side at a time . That way I still have one good side to brake with while the new bads bed in. A bit harder to do if you only have one disk so extreme causion must be exercised in that case.

Sounds like when the front calliper(s) were loose to fit the new pads that somehow some air got into the system. A similar thing happened to my Firestorm when I was getting a new chain and sprockets fitted. It has a hydraulic clutch and the piston that actuates the clutch has to be moved out o f the way to fit the front sprocket. In doing that some air got into the system and it was a right bugger to get rid of it.

Big Kneed Al (master of the emergency stop & "stand up" comedian).

Coddy · Post by **Coddy** » Mon Aug 27, 2007 8:06 pm

1. Brake pads need a good 200-300 miles of use, to bed them into the discs and to work heat (cycle) them.

2. Before the lever is coming back to the bars, their is air in the system or not enough fluid. Check for leaks, check level in the master cylinder, bleed the brakes.

IZINBARD · Post by **IZINBARD** » Mon Aug 27, 2007 9:18 pm

Not the bleeding brakes. (Sorry) :I can't believe it's not butter!

Wrong pads and something fouling. Lever lock up is not caused by air in the system, but by Max (Billy-Ray) hyd pressure in the system. Metal against metal and squeezing the poo out of the lever, if it was air then the lever would come all the way back to the bar or be spongy at least not hard as a rock.

look at the disc(s) is there a very blue or new shiny bit on them.

Remove the pads and look for scuff marks where there shouldn't be.

Something is fouling to give you a hard lever and no stopping power.

cbr1100 · Post by **cbr1100** » Mon Aug 27, 2007 9:24 pm

I just had the same with mine, after delinking my brakes i put in new HH pads and bled the system the first 30-40 miles it did around town started off just tappi ng the brakes lightly and keeping my speed low so if i had to stop i wouldn;t need a lot of brakes and now 268 miles later they feel great.......sound like bedding in and maybe air in the system or a sticky piston/piston on the calipers.

grantwils · Post by **grantwils** » Mon Aug 27, 2007 9:40 pm

Thanks for the replies guys.

I've just been looking over the bike with my car-mechanic mate and we've noticed that the pad on the right hand side (furthest from the wheel) is completely cooked with very little 'pad' left. It's all cracked and looks like it has been in a fire. The pad on the left hand side (closest to the wheel) still looks all shiny and new.

I'm very tempted to go get new discs, pads and braided hoses fitted at a main dealer.

Post by al » Mon Aug 27, 2007 10:02 pm

grantwils wrote:Thanks for the replies guys.

I've just been looking over the bike with my car-mechanic mate and we've noticed that the pad on the right hand side (furthest from the wheel) is completely cooked with very little 'pad' left. It's all cracked and looks like it has been in a fire. The pad on the left hand side (closest to the wheel) still looks all shiny and new.

I'm very tempted to go get new discs, pads and braided hoses fitted at a main dealer.

If your bike has sliding callipers it may be that the sliders are seized! If the calliper only has pistons on one side then they are definetly sliding callipers.

The sliding part of the calliper should be able to move freely with finger tip farce. If not get it off and cleande up and lubricated. If you can, get the rubber sleeve out from the other part of the calliper as crub can build up between the metal and the rubber causing the rubber to "grip" the sliding pin inside. The front callipers on Bandits and SV650's are prone to that.

Big Kneed Al (master of the emergency stop & "stand up" comedian).

Post by al » Mon Aug 27, 2007 10:03 pm

No point in fitting new disks till the callipers are fully operational. The pistons should be clean and able to be pushed back into the body of the calliper with finger pressure only.

grantwils · Post by **grantwils** » Mon Aug 27, 2007 10:07 pm

Cheers Big Kneed Al (master of the emergency stop & "stand up" comedian)

So now you've got me tempted to get new discs, pads, lines and callipers - or should I just get the calipers overhauled?

Post by al » Mon Aug 27, 2007 10:11 pm

grantwils wrote:Cheers Big Kneed Al (master of the emergency stop & "stand up" comedian) ( Super Nanny )

So now you've got me tempted to get new discs, pads, lines and callipers - or should I just get the calipers overhauled?

Unless the disks are now warped of worn then I'd get the callipers sorted first. The hoses on the bike are probably due to be changed out anyway but no point in spending money elsewhere if the callipers are kack.

grantwils · Post by **grantwils** » Mon Aug 27, 2007 10:16 pm

OK, calipers then the rest...

Now the big question... braided hoses or rubber hoses?

Grant · Post by **Grant** » Mon Aug 27, 2007 10:17 pm

grantwils wrote:OK, calipers then the rest...

Now the big question... braided hoses or rubber hoses?

Go for braided!

Post by al » Mon Aug 27, 2007 10:20 pm

braided hoses will be cheeper than a standard rubber kit.

grantwils · Post by **grantwils** » Mon Aug 27, 2007 10:21 pm

Cheaper? But would I be better saving a few quid or getting rubber hoses?

Grant · Post by **Grant** » Mon Aug 27, 2007 10:22 pm

grantwils wrote:Cheaper? But would I be better saving a few quid or getting rubber hoses?

Braided hoses are better than rubber hoses!

brooner · Post by **brooner** » Mon Aug 27, 2007 10:36 pm

Grant wrote:
grantwils wrote:Cheaper? But would I be better saving a few quid or getting rubber hoses?
Braided hoses are better than rubber hoses!

Aye, braided hoses dont 'flex' under pressure, so more hydraulic pressure goes into the calipers, bringing you to a safe halt (hopefully!!).
And they last longer too.

Post by al » Mon Aug 27, 2007 10:42 pm

Grant wrote:Braided hoses are better than rubber hoses!

They are no better than brand new rubber hoses.

Braided hoses can give the brakes a wooden feel. Rubber hoses can allow a less experienced rider to better modulate the pressure on the brake so can brake safer and give more confidence.

When it comes to replacing the lines after market braided kits work out cheaper than OEM rubber kits so hence why very few folk go for the OEM kit.

It took me ages to get used to the feel of the front brake on the XT which uses a single braided line. Where as, just like rubber hoses, the lines on the TT600 are past their best and could do with being replaced.

As Public Enemy say, "Don't believe the hype"!!

Big Kneed Al (master of the emergency stop & "stand up" comedian).

yelloisfriedegg · Post by **yelloisfriedegg** » Tue Aug 28, 2007 7:02 am

Coddy wrote:1. Brake pads need a good 200-300 miles of use, to bed them into the discs and to work heat (cycle) them.

absolute bollocks

Coddy wrote:2. Before the lever is coming back to the bars, their is air in the system or not enough fluid. Check for leaks, check level in the master cylinder, bleed the brakes.

Correctamundo :I can't believe it's not butter!

Backs 400 · Post by **Backs 400** » Tue Aug 28, 2007 9:22 am

yelloisfriedegg wrote:
Coddy wrote:1. Brake pads need a good 200-300 miles of use, to bed them into the discs and to work heat (cycle) them.
absolute bollocks l

Please quantify this statement! :)

Every set of pads i have ever fitted have said on the box "Full performance will not be achieved until XYZ miles have been covered"

The brake overhaul manual i have from the library just now says the same.

Just interested in why you say this.

yelloisfriedegg · Post by **yelloisfriedegg** » Tue Aug 28, 2007 10:08 am

Brake pads are made by moulding (it used to be asbestos and lots of other stuff like gunmetal and carbon powder) powdered metal (sintered) into a shape at very high pressure and temperature using a hydaulic press.

The material is molded (bonded) directly onto the backing plate and the outer surface of the new pad is smooth and very hard.

The inner construction of the pad is different , all the particles of powdered metal have very (microscopic) small gaps between them , this is how a brake pad works , as you brake the friction material loses it's efficiency as it glazes up through heat , the small gaps allow material to "fall away" exposing new high friction material. It's a bit like a grinding wheel , as you use the grit in the wheel to cut something it dulls , falls away and exposes new sharp grit to continue cutting / grinding.

When pads are new the outer smooth surface is very prone to "glazing" if you brake too hard and get the pads too hot , a few miles of gentle braking to bed the pads into the disc and expose the inner material is usually enough , although even when pads have been used for thousands of miles lots of repeated heavy braking could cause a pad to glaze up , if this happens a few miles of gentle braking to clean the surface should bring things back to normal.

When I said bollocks to hundreds of miles to bed a pad in it's the same as stories of hundreds of miles to scrub in tyres , it's just not true , a tyre can be scrubbed in after just a few miles , someone like Dale is only using a tyre for 1 or 2 races so 30 miles or so , are they scrubbed in , you bet :I can't believe it's not butter!

Same for brake pads , I doubt Dale would get more than 300 miles out of a set , when I was racing 250's pads would last maybe 500 miles tops

...........oh , by the way , I served my apprenticeship at Mintex Ltd , the largest prodcer of brake pads and friction materials in Europe , Ferodo , Lucas , Girling all trading names of mintex , they also invented the sintered pad and were leaders in non-asbestos brake development.

..............quantified ?

Graeme · Post by **Graeme** » Tue Aug 28, 2007 12:36 pm

Are you sure the pad didn't separated from the back plate? I had a similar experience once - when I grabbed the brake lever there was no resistance at all, it came right back to the bar. Later inspection showed the pad material had detached from the backing plate - there was no pad left at all on one side. I'd heard a loud clonk from the front just prior and thought it was a stone, it must have been the brake pad bouncing off the wheel !

Luckily there was an 'escape route' which gave me enough time to stop with the rear brake

Backs 400 · Post by **Backs 400** » Tue Aug 28, 2007 12:38 pm

yelloisfriedegg wrote:...........oh , by the way , I served my apprenticeship at Mintex Ltd ,

Thats what i thought and thats why I asked you and no one else!

Thank you for that explaination! :I can't believe it's not butter! I hoped you could come up with a much better way of expersing the facts than bollocks!

yelloisfriedegg · Post by **yelloisfriedegg** » Tue Aug 28, 2007 12:57 pm

I thought bollocks was fine actually

grantwils · Post by **grantwils** » Tue Aug 28, 2007 1:04 pm

Took it to the local Kwak dealer this morning. They said that the previous mechanic had just put new pads on when the caliper clearly needed a refurb. They're doing the front and back brakes today - new pads & refurb/clean calipers - braided hoses are on order and will be fitted next week.

the pad that had jammed on was completely knackered - no 'pad' left and all crispy and burned.

While I was there they tried to tempt me to buy a new Versys - 0%apr. Â£99 deposit and Â£116/month for 3 years. Anyone got the money they want to give away?

Thanks for all the help and advise folks - I just hope I can get used to the new braided hoses.