Jerky/pulsing front brake

[ClareQuilty]

My latest Yamaha Tiara is all fixed up now, running and driving great, but with one annoying problem - the front brake, if applied at all strongly, catches with a jerky, pulsing feeling. Its fairly annoying. I had hoped it might be just the front wheel put on a bit 'off', as the problem wasn't noticeable before a recent application of (original spec) new tires (the previous ones had been a bit too narrow, as the Thais are wont to do), but the mechanic says its the rotor. He didn't recommend replacing the rotor as he said the problem wasn't severe and the part could cost about 1,200 baht.

I've replaced a rotor on a Honda Tena before and I think it was only around 650 baht. I'm wondering if anyone has any opinion on this problem, such as alternative solutions or diagnoses. Has anyone had occasion to deal with the herky jerky disc brake?

[Briggsy]

I have replaced a brake disc or rotor on a Honda Sonic. The mechanic said, "Don't worry, we'll find a second-hand one." He was very vague but when I asked him to do it a few weeks later, I think it was 350 Baht.

Second-hand one is the way to go if you don't want to spend 1200 Baht. Don't put off fixing brakes. If the disc is damaged, then your brake pads will be wearing out after 2,000 km so you might as well replace the disc if it is damaged.

Is the disc simply scored or is it bent?

I know it is simple but how are your brake pads? I am sure you have checked already.

Edited December 28, 2013 by Briggsy

[1ma]

Start by spraying a fukload of wd-40 on the brake-lever components and (visible) cable.

Edited December 28, 2013 by 1ma

[PiPiFFS]

You can't really put the front wheel on a " bit off "and if it is a disc brake then spraying the lever, there is no cable, with WD will do nothing. It sounds like you have a warped front disc which needs replacing. Not expensive and will remove all the shudder etc when braking.

If it is snatching then the pistons may need a bit of attention which is even cheaper

[David48]

^^ Ditto ... I was think slightly warped disc.

Hey, just a general question, if the disc is think enough ... do they machine them here as opposed to replacing them?

[Briggsy]

Oh yes, the grinder will come out if the disc is scored.

[ll2]

Still wd40 the levers and cable first. If still same, just change all brake components. If it is brakes, money is not important really!

Sent from my GT-N7100 using Thaivisa Connect Thailand mobile app

[1ma]

You can't really put the front wheel on a " bit off "and if it is a disc brake then spraying the lever, there is no cable, with WD will do nothing.

You'll have to excuse my lack of proper terminology.

1st step: Pull the brake lever. Spray wd-40 into the bolt area/housing that allows the lever to move, and then where the cable connects to the lever.

[desmondspencer]

Brake cable on a bike????

From my minute experience, isn't the brake

Connected to the brake hose within it

is the brake fluid???

To OP, reveled your brake lines and check again, you might simply have poor bleeding, if that fails dont compromise and change out for a brand new rotor.

[ClareQuilty]

The lever's moving great, I think its probably the disk. I'm pretty sure it must be warped, as that's how the motion feels when you brake hard. When you brake softly its fine.

It sounds like you have a warped front disc which needs replacing. Not expensive and will remove all the shudder etc when braking.

Well it didn't sound cheap to me - he quoted 1,200 baht!

Edited December 28, 2013 by ClareQuilty

[desmondspencer]

I meant to say rebleed you brake lines

[Maybole]

First check that all the bolts fixing the disc to the wheel are tightened to the proper torque, then check the disc is true. If the disc is warped try to get it replaced under waranty

[wantan]

If the disc is warped the pulsing should correspondent with the rpm of the wheel (Pulsing always at the same place, lower speed = lower pulsing frequence). Get a used disc for replacement if a new one is "expensive". And maybe check the front wheel bearing for damage. But it sounds like a warped disc.

[ClareQuilty]

First check that all the bolts fixing the disc to the wheel are tightened to the proper torque, then check the disc is true. If the disc is warped try to get it replaced under waranty

I doubt any warranty is valid - the bike's about 20 years old I'd guess.

[ktm jeff]

If the bike has been standing a while , being fixed up , there may be a rust spot (barley visible) where the disc pad has sat against the disc , and may just require cleaning up with abrasive paper.A slight warp may be straightened out with careful use of small lever ( or remove disc and straighten on a anvil ).Rust spot OR a warped disc will cause feeling as described with one pulse per wheel revolution.

[Longtooth]

If the bike has been standing a while , being fixed up , there may be a rust spot (barley visible) where the disc pad has sat against the disc , and may just require cleaning up with abrasive paper.A slight warp may be straightened out with careful use of small lever ( or remove disc and straighten on a anvil ).Rust spot OR a warped disc will cause feeling as described with one pulse per wheel revolution.

That's it for sure! Rust on the disc except where the pads were sitting. Get the front wheel off the ground, have somebody spin it by hand as fast as they can, and hold some medium sandpaper or emery cloth against the disc, BOTH SIDES, one side at a time, because you want to push hard and your spinner guy won't be up to you being the "brake". It won't take long, it'll fix it. You'll see and feel the problem for yourself when you do this.

[paz]

That's it for sure! Rust on the disc except where the pads were sitting. Get the front wheel off the ground, have somebody spin it by hand as fast as they can, and hold some medium sandpaper or emery cloth against the disc, BOTH SIDES, one side at a time, because you want to push hard and your spinner guy won't be up to you being the "brake". It won't take long, it'll fix it. You'll see and feel the problem for yourself when you do this.

That will NOT fix it, if ever the OP want to bother trying.

[canuckamuck]

Change your brake fluid. and try again

[BirdsandBooze]

Sounds like a warped disc. On a 20 year old bike it'll be pretty thin if it's the original and heat build up from regular brake application can be enough to put it out of true. If you buy a secondhand one make sure it has enough 'meat' on it.

[BSJ]

Some funny answers here!

Go to a shop that has aftermarket parts and accessories and you will find new disk rotors for 850 baht and up. Problem solved.

[Gonsalviz]

Jeez, the number of no mechanical knowledge people on here is phenomenal.

Change the disc and the brake pads.

Edited December 29, 2013 by Gonsalviz

[1ma]

Whatever you do CQ, make sure you do it in a patronizing manner.

[yankee99]

Before wasting money why not check to see of your rotor is warped which can be done in about 8 seconds once the wheel is off the ground...

[cornishcarlos]

It's probably the battery

[canuckamuck]

How old is the paint job?

[BSJ]

Before wasting money why not check to see of your rotor is warped which can be done in about 8 seconds once the wheel is off the ground...

He has already come to the right conclusion: "if applied at all strongly, catches with a jerky, pulsing feeling. "

[David48]

Jeez, the number of no mechanical knowledge people on here is phenomenal.

Change the disc and the brake pads.

I have a wee bit of experience ...

If the front disc, after 20 years use the front disk is either warped or too thin ... why must the brake pads be changed if they are serviceable?

[Gonsalviz]

Jeez, the number of no mechanical knowledge people on here is phenomenal.

Change the disc and the brake pads.

I have a wee bit of experience ...

If the front disc, after 20 years use the front disk is either warped or too thin ... why must the brake pads be changed if they are serviceable?

Because if the disc is warped is causes uneven wear on the brake pads. Besides they are cheap.

[guzzi850m2]

The lever's moving great, I think its probably the disk. I'm pretty sure it must be warped, as that's how the motion feels when you brake hard. When you brake softly its fine.

It sounds like you have a warped front disc which needs replacing. Not expensive and will remove all the shudder etc when braking.

Well it didn't sound cheap to me - he quoted 1,200 baht!

1200 baht is cheap man, what is your problem with that??

Only a fool fools around with the brakes on your vehicle, I would never take any changes with them, never, and always buy new replacements parts.

[paz]

1200 baht is cheap man, what is your problem with that??

Only a fool fools around with the brakes on your vehicle, I would never take any changes with them, never, and always buy new replacements parts.

Not cheap on a bike worth 5 or 6K. Brakes are very simple and robusts devices, not difficult at all to maintain and fix. The fear that people has about themis par with mechanical ignorance as well exposed on this thread.