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Spongy feel left brake lever?


omy005

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omy005

Hello all, my 2012 Intega with combined brakes has a issue when I pull the left lever it comes very close to the bars (but the stopping power is good). If I pump it a couple of times it feels much firmer and doesn't come so close to the bars. Right lever (front only) feels and performs fine. Front and rear pads have plenty of material left and there are no obvious leaks any where. Discs are running true.

 

So it might just be a case of bleeding the left lever? Is there a special procedure for doing this on combined systems with ABS?

 

Thanks. 

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davebike

Rather than bleeding at first  clean and service both calipers 

If that fails Then bleed  dont drain the left hand/rear brake master cylinder  remember it goes to both front and rear calipers sorry cannot remember whitch bleed nipple is the linking one

BUT unless you or someone else has been working on the hydrolics I expect it to be a sticking caliper or poor / worn pads  you don't "lose bleed"  unless you have a leek or have been lossening or disconecting pipes removing pistons etc 

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trisaki

Middle nipple on the front  caliper  is the rear /combined  brake 

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omy005

Thanks for the reply's, I'll look into it a bit further with the above suggestions.

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Steve Case

Surely there is some increase in movement as the pads wear, obviously not as much as a car but since the brake lever is operated by hand you would tend to notice it more.

 

I had to adjust the lever position on mine for the front brake to take up play due to wear.

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Andy m
1 hour ago, Steve Case said:

Surely there is some increase in movement as the pads wear, obviously not as much as a car but since the brake lever is operated by hand you would tend to notice it more.

 

I had to adjust the lever position on mine for the front brake to take up play due to wear.

 

No. 

 

Lets say (all made up numbers) the pads are 5mm thick and 0.5mm off the disk with the brake not applied . We send 10cc's of fluid down the line and the piston closes the gap and wears 0.01mm off the pad. We now release the brake and 9.999 cc's of fluid comes back and is then connected to the reservoir which drops its level to account for the piston staying out an extra 0.1mm. We now have the 0.5mm gap between disk and pad again and it takes the same 10cc's to close it at the next application . If every ratio in the system was 1:1 the volume of fluid in the reservoir would drop by volume of pad worn away. Over the life of a pad maybe 10mm drop in fluid depth. 

 

If mechanical slack adjustment is needed there is something wrong. 

 

On bigger stuff there is mechanical adjustment, basically a ratchet system. Legislation requires all stack adjustment to be automatic up to the point wear can be detected. In the case of a bike the groove in the pad will be gone before the reservoir level drops below the min line having started in the middle or empties having started on min. You have two chances to spot it, the line and the groove. The groove is the official way because you can just top up (and new pads will then cause an over flow). 

 

Andy

 

 

Edited by Andy m
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Steve Case

Sorry mate ratchet? you sure about that

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Andy m

 

Filthy, ****y things that loonies think can be adjusted via laptop. The normal tale is that the design (my job) must be wrong because the slack adjusters have been full set and it still won't stop. When you get there a good tug, click-clack and normal service is resumed, of they are so full of **** there is no click-clack only the thud as the brake cylinder strokes out. 

 

Andy

Edited by Andy m
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Steve Case

Is that a truck? I have never seen a slack adjuster except on the cable on a cable operated drum...

 

I guess they must have something similar on the hydraulic drums on the old BMC tat some of my friends run, but hopefully I will never know.

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Andy m

Hopefully you won't see one, horrible things that are only still here because UK commercial vehicles are stuck in the stone age. 

 

The reservoir level dropping serves the same purpose on an hydraulic system just in smaller steps. 

 

Andy

 

 

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Steve Case

Yup I've seen the reservoir dropping on the car.

 

On the bike I have to explain I have the lever set with the 1st third of the travel doing nothing essentially the 2nd third is where the braking happens and the last third is where my fingers are. as the pads wear I will see the fluid level drop but I will also gain some more movement on the lever.

 

Since the lever is operated by hand which is more sensitive and essentially the lever has to move a large amount for a small amount of piston travel there will be some change in feel as the brake caliper will retract to the same resting position and I think the piston will not take all of the change in stroke, 

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davebike

The slack on the leaver comes from

1 The need for there to be enough clearence leaver to Master cylinder piston to ensure the piston returnes to "at rest" so return hole is open and brakes relese

2 the verious mechanical bit like the leaver pivet having slack

3 The caliper  pistons being VERY slightly pulled back by the seals and any inperfection in the disk

 

In my experence excessive travel is almost always calliper related unless it is owner fitted leavers !

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Steve Case

Yup sounds reasonable, I do set the lever with slack as I don't like the brakes to operate as soon as I touch the lever.

 

I was thinking that with these sliding calipers fitted that half the travel is the piston and half the caliper on the pins, and since the caliper appears to return to the same starting position that means the travel to the biting point must increase. And the caliper resting position doesn't change the fluid level.

 

Also the crap that gets in the calipers must affect where the caliper and piston rest, tho mostly I would expect it to cause binding of the brake.

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embattle

Use brake pads rather than sponges for stopping.

 

On a serious note, I get my bikes serviced so they can check them rather than myself making a utter pig's ear of it.

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omy005

I checked the left brake reservoir and the level is fine, next job (now I've done the shift pin replacement) is to look at the caliper sliders. 

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Steve Case

I have noticed the retaining pin for the pads corrodes quite badly and could affect travel, since they are readily available and not massively expensive I will replace at the same time as the brake pads from now on.

 

On another note I have to maintain my own brakes as I prep them for winter and then check them in the spring (generally clean and regrease), plus I may have to replace pads at some random time in the year.

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omy005

I removed the rear caliper this afternoon and greased the slider pins and any other point of contact that may affect movement. I'll test it out on my commute tomorrow.

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omy005

No difference to the rear brake feel, one or two pumps and the lever is firm. Maybe a seal kit for the master cylinder then?

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Steve Case

That thing has C-ABS doesn't it? Are you sure you want to be taking apart that system as it could be air in anyone of the 97 hydraulic pipes and 43 fittings.

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On 10/09/2021 at 23:11, Steve Case said:

That thing has C-ABS doesn't it? Are you sure you want to be taking apart that system as it could be air in anyone of the 97 hydraulic pipes and 43 fittings.

Yes it does have the combined system and I'm quite used to it now. There's only one line from the master cylinder, It's no more complicated than a car's brake system? And I've bled plenty of them over the years.

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Steve Case

I suspect you may be more logical and patient than I am.

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