Disc brakes problems!

[mtb_Josh]

Ja, I think i'll rather take it to the lbs, dont have a bleed kit anyway..

[coola]

 

 

Changed the pads on my xt brake set but I can't get the oustpon bwck to stop them binding ? Any help

[Johan Bornman]

I think you can fix this one easily. The pistons are siff and dont' want to slide in and out their seals anymore.

 

Take out the pads, pull the brake lever gently until the pistons just-just want to pop out of their sockets. Now spray them with Q20 until they run clean. Push them back, wipe the lot, replace the pads and go ride.

 

Temperature has ziltch to do with it. They can go from snow to desert without a hiccup.

 

 

[Weight Weenie]

You see Josh, told you they could be dirty or heated up

 

Thanks for the ride bud !

[mtb_Josh]

Thanks JB! will try that tomorrow!

 

 

 

WW, sorry bout the technical difficulties! Next time we can hopefully do a proper ride without having to dismantle by bike next to the road

[Wyatt Earp]

The pistons are siff and dont' want to slide in and out their seals anymore.

 

 

How do they slide in and out their seals ?

[ichnusa]

I think you can fix this one easily. The pistons are siff and dont' want to slide in and out their seals anymore.

 

?

 

Take out the pads' date=' pull the brake lever gently until the pistons just-just want to pop out of their sockets. Now spray them with Q20 until they run clean. Push them back, wipe the lot, replace the pads and go ride.

 

?

 

Temperature has ziltch to do with it. They can go from snow to desert without a hiccup.

 

?

 

?

[/quote']

 

 

 

I agree that temp has nothing to do with it...

 

 

 

The reason they not pulling back as nicely is maybe that the pistons are worn... ie, in stead of being perfect cylinders, they are now "hour-glass" shaped. Thus they do not sit perfectly perpendicular in the calipers and do not slide as nicely. Once agian, replace the pads...

 

 

 

JB's solution will work, but i do not think for very long if you do not replace the pads. Q20 dries up in minutes....

 

 

 

regards

 

al

[Little-Ben]

I agree that temp has nothing to do with it...

The reason they not pulling back as nicely is maybe that the pistons are worn... ie' date=' in stead of being perfect cylinders, they are now "hour-glass" shaped. Thus they do not sit perfectly perpendicular in the calipers and do not slide as nicely. Once agian, replace the pads...

JB's solution will work, but i do not think for very long if you do not replace the pads. Q20 dries up in minutes....

regards
al[/quote']

that would mean a solid object needs to change shape, if it wares into a hourglass shape then in theory the pistons would become loose.

[ichnusa]

I agree that temp has nothing to do with it... The reason they not pulling back as nicely is maybe that the pistons are worn... ie' date=' in stead of being perfect cylinders, they are now "hour-glass" shaped. Thus they do not sit perfectly perpendicular in the calipers and do not slide as nicely. Once agian, replace the pads... JB's solution will work, but i do not think for very long if you do not replace the pads. Q20 dries up in minutes.... regards al[/quote']

 

 

that would mean a solid object needs to change shape, if it wares into a hourglass shape then in theory the pistons would become loose.

 

 

 

Yes, they become loose, but, as i said, just in that they do not come out perfectly perpendicular to the calipers. Thus, they also do not retract nicely. It could only be dirt... but if Q20 does not work for long with new pads, you need new pistons as well. It is what i needed to do with my Juicy's

 

 

 

a

[mtb_Josh]

I tried JB's solution yesterday. I battled to push the pistons back after i sprayed them, but I think they have actually been out too far since I got them (had more drag on the back than the front). Anyway, got them back far enough to get the old pads back(these pads are very new...dont really want to replace them...) in. There is still a bit too much drag, but I had that before the incident anyway. But to my great joy, I realised my fork isn't holding pressure in the negative chamber so I haven't had a chance to test drive the brakes very much...

[Wyatt Earp]

Q20 contains Chlorinated Hydrocarbons which is supposed to be rather volatile towards some natural rubbers.

 

The o-ring in your piston is rubber and only a small one at that.

 

Some rubbers get manufactured using Chlorinated Hydrocarbons but it has been found that if natural rubber was to have Chlorinated Hydrocarbons applied in liquid form it could cause swelling.

 

 

 

"     On the other hand, Buna-n rubbers generally have poor resistance to sunlight, ozone, weathering, phosphate esters, ketones, glycol-based brake fluids, high-aromatic fuels and hydrocarbons like benzene, chlorinated hydrocarbons like trichlorethylene, polar solvents like ketone, acetone, acetic acid and ethylene-ester, and strong acids. "(copied of the WWW)

 

 

 

 

 

My advice , get the pistons out, replace the o-rings and re-assemble.            

[Johan Bornman]

I cannot find any reference to Q-20 or WD-40 containing chlorinated hydrocarbons. Maybe I just can't search properly.  In found a German spec sheet and even a nice website dedicated to "What's inside WD-40" that I found interesting.  WD-40 is not patented, the owners claim that would give away the secret, but safety regulations in some countries require full disclosure, hence the data sheets.

O-rings may be rubber, but they're not natural rubber and they're completely impervious to penetrating lubricants. Test it for yourself.  The type of rubber used in oil-based and DOT fluid-based brakes are different, but neither have problems with a bit of Q-20. The amount you spray on simply lubricates and cleans the pistons and the volatile stuff evaporates and the rest drips off with the dirt. After a few strokes of the piston, it is mobilised and lubricated by its own fluid once more. The little bit of Q-20 that remains is either absorbed by the rest of the fluid or expelled.

 

It is a known fact that certain fluids do cause certain types of rubber to swell. It is more of a jellification process than swelling, with the rubber becoming softer and bigger. This in itself is not a bad thing and can save you from a problem, if you know how to use it to your advantage.

 

A case in point is watch casing seals. If you as an amateur remove your watch's back to change the R10 battery that the agent wants R150 for, you're faced with the dire threat of a leaking watch. An old trick is to soak the seal in a bit of Q-20 squirted on a cloth. It expands and softens the seal/o-ring ever so slightly and it seals properly again. Unfortunately or, fortunately this is not the case with standard O-rings we buy from engineering supply shops.

 

Back to the brakes. If the pistons had worn, like ichnusa here said, then clearly they need to be replaced and it would be prudent to replace the o-rings/seals at the same time.

 

I find that in most cases they are simply dry and need a bit of lubricant to get them mobile again. It is always worth a try, especially since we know nothing can be damaged by this type of attempt armed with Q-20 or similar.

 

Josh, there is a good chance that you'll find that your brakes come right by themselves, as long as those pistons can move and are made to move a bit. You may need to remove the pads and push them out as far as you dare, if that is what it takes.

 

 

 

 

 

 

 

 

 

 

 

[Wyatt Earp]

Q2O SUPER MULTI-PURPOSE LUBRICANT

 

 

 

Material Safety Data Sheet Q20 Aerosol

 

 

 

1    IDENTIFICATION

 

Manufacturer:          Triton-Leo Group (PTY)LTD, P.O. Box 459, Isando 1600

 

                                 Tel:   011 452 7048       Fax:   011 452 8457

 

Chemical name:      Organic mixture

 

Trade name             Q20 Super Multi-Purpose Lubricant

 

1.1    Chemical characterisation        Organic mixture of highly refined mineral oil distillates of specific

 

                                                           composition, which repels moisture, prevents corrosion, cleans

 

                                                           and lubricates.

 

1.2   Colour:                                      Straw colour

 

1.3   Odour:                                       Mild oily solvent odour                   

 

2    COMPOSITION

 

The product contains the following materials apart from gases.

 

                                                               %Weight                    Cas No                    Chip (risk)

 

Chlorinated Hydrocarbons                     54.72%                   64742-82-1                    R10

 

(WHITE SPIRIT)

 

MINERAL OIL (REFINED)                   18.20%                   64742-65-0               N/A(for lubrication)

 

CARBON DIOXIDE AND R22(gases)   13 %                        124-38-9                        N/A

 

LUBRICANTS & JELLIES                    2.08%           (RUST INHIBITORS)

 

SOLVENTS                                           25%               (CLEANING PROPERTIES)    

 

3    HAZARDS IDENTIFICATION

 

3.1     Fire and Explosion

 

Flash point:                                   Tag open cup 85?c (minimum)

 

Flammable limits:                         (Lel)1.0% (Uel)6.0%

 

                                                      (Solvent portion)

 

Extinguishing media:                    CO?, dry chemical, foam

 

Special fire fighting procedures:   See section 5herein

 

Unusual fire and explosion            Flammable

 

3.2     Health/Routes of Entry

 

Threshold limit value:                    Hydrocarbon solvent lowest TLV(100ppm)

 

Carcinogenic:                                 The product has been assessed by independent laboratories as

 

                                                        being human carcinogen category 3

 

3.3     Symptoms of Exposure

 

Inhalation                                       May cause anaesthesia, headache, dizziness, nausea and upper

 

                                                        Respiratory irritation

 

Skin contact:                                  May cause drying of skin and/or irritation

 

Eye contact:                                   May cause irritation, tears and redness

 

Ingestion:                                       May cause irritation,nausea,vomiting and diarrhoea

 

DANGER if swallowed can enter lungs and may cause chemical pneumonia. Do not induce vomiting. Obtain medical assistance.

 

 

[shimano 105]

 

 

 

 

 

Juicy's should only be bled with dot 4 or dot 5.1 ' date='if your shop used something else that is not easy on the rubbers this could be the problem.[/quote']

 

This could be the problem.Wrong fluid.

 

[Johan Bornman]

Summit, thanks for the spec sheet. I somehow overlooked it on that funny website. Anyway, it still doesn't swell o-rings. Soak an o-ring in some of the stuff, you'll see.

 

 

[mtb_Josh]

I took the pads out and pulled the brake lever in all the way - didn't result in too much movement from the pistons though. I tried to get a bit of Q20 in and then tried to push the pistons back, but like I said, not a lot of movement at all.