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Caliper disassembly/reassembly "How To"
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Posted by: Pappy

Stopping your machine should be paramount over going fast, or you will only go fast once! Your braking system should be designed to handle the machine and rider and in ordinary riding situations should be more then adequate for quite some time before needing your attention, except for brake pads. Pads should be checked before each ride as in certain environments such as riding in mud or when there is a lot of water on the trail your brake pads can get worn down extremely fast leaving you in a bad spot with no brakes!

When you have to get more involved with your calipers due to a rebuild or to fix an issue beyond brake pads, you should know what is involved and for most, the job is simple and will save you some cash over taking it to the dealer. There are five major components to your braking system:

Brake Master Cylinder- Holds fluid and when operated by your brake lever pumps pressurized brake fluid to the caliper to make it operate

Brake Lines- carries the brake fluid from the master Cylinder to the caliper

Caliper- Houses the pressurized brake fluid and when applied, forces a piston out of the caliper to contact the brake pad, which in turn forces the pads to squeeze the brake rotor.

Brake Rotor – This item is connected to your front hub or rear axle assembly (rear Brake Hub) and is what the brake pads contact when pressure is applied to the system via the brake lever(s)

Brake pads- These two pads are made of either sintered metal or organic compounds and are held in place by two sliders in the brake caliper housing and provide friction from the force of the system to stop your machine

All of these components work in harmony to bring you to a nice stop when needed and are often overlooked during routine maintenance. Here we will take an inside look at how to disassemble and reassemble a Honda 400ex caliper. (Most all calipers for ATV’s equipped with hydraulic braking systems are of similar design even though the outer appearance may be different)

Tools needed: Small pick, 4mm and 6mm allen head wrench, soft jaw pliers,

Always start with a clean work area and get the calipers as clean as possible before starting your work. The caliper consists of several parts including the housing, sliders, various seals, piston(s), bleeder valve and caliper mount.

Posted by: Pappy

Start by removing the outer dust caps to access the slider pins and retaining bolt. Save these or replace as they will keep debris out of the bolt heads and make for much easier maintenance in the future

Posted by: Pappy

Using the 4mm allen head wrench, remove the sliders and once removed, the brake pads will fall from the caliper. Then remove the Bushing Pin with the 6mm allen head

Posted by: Pappy

During disassembly, check the seals for rips or tears, as they will need to be replaced

Posted by: Pappy

The caliper mount will also be removed and set aside when the Bushing Pin is removed.

Posted by: Pappy

Dust seals are the most often replaced item as they tear easily, so gently remove them and use care when re-installing them.

Posted by: Pappy

The piston can now be removed, and there are a few methods you can choose from. Tool companies offer an attachment for your air compressor that can pressurize the caliper and force the piston out, or you can use a set of soft jaw pliers to gently remove the piston. Care should be taken when using any pliers and usually a gently turning motion to spin the piston while pulling outwards will release the piston. If the piston is flush with the caliper, use compressed air blown through the bleeder valve hole (reinstall the brake line bolt) to release the piston. Care should be taken and low pressure used to avoid shooting the caliper out and damaging the piston and your fingers

Posted by: Pappy

With the piston removed, use a small pick to remove the two seals from the caliper housing. These seals last a long time and very seldom need replacing, however a good inspection is easy and makes for good piece of mind.

Posted by: Pappy

The Spring Pad can be removed at any point after the pads are removed

Posted by: Pappy

That’s it, you have just disassembled a brake caliper! Re assembly is the reverse of disassembly and total time for both should run about 10 minutes. When re-assembling, be sure to lubricate the internal seals and piston with a small thin layer of brake fluid to keep them from drying out and to aid in reinsertion. The slider pins should be cleaned well and a waterproof grease applied often as they can become corroded and cause issues with the brake pads as the pad will not release off the rotor adding wear to the pad and more money from your wallet.

Posted by: zdowell

I just did this over the weekend. Just started unbolting stuff on the caliper to take it apart. The caliper slide pins were frozen up.

Isn't there suppose to be a pad on the piston?

Posted by: Pappy

yes there should be, but it runs about a 50/50 shot of being there when I get them in here

Posted by: <DRS>GPF

nice walkthrough..

just went through all this on a warrior a friend and i are resurrecting for my son.

they had lived a hard, non-maintained life.. one was allowed to pass on to the afterlife..

Posted by: rideracelivemx7

great thread but you forgot one more seal. the infamous leak in the back of the read caliper. theres a seal where the pb is used. plenty of them leak after time. its just a tiny o ring though. a little pain to get to though.

Posted by: Pappy

quote:
Originally posted by rideracelivemx7
great thread but you forgot one more seal. the infamous leak in the back of the read caliper. theres a seal where the pb is used. plenty of them leak after time. its just a tiny o ring though. a little pain to get to though.

It was omitted due to the fact it rarely ever has to be replaced, but you are correct, it is there

Posted by: 250rAL

There is another part to this subject when you are dealing with 20-plus year old machines like I have. Eventually, the caliper will seize at one of two places. Either the slide pin that the caliper floats on will freeze up in it's bore or the piston(s) will. The cause is corrosion. The slide pin is steel and the caliper is aluminum. The two different metals don't like each other and they will lock together after a couple decades of no maintenance. What you will find when you have a piston seizure is aluminum oxide(rust) in the seal grooves. The oxide grows to the point that it starts pushing the seals out of their grooves and tightly against the piston. Eventually the piston goes out during a brake application and won't return. This results in pads quickly worn away, then the rotor ruined by grinding against the backing plate. The good news is both problems can be fixed by cleaning out the corrosion and replacing the seals.

Posted by: sunco

I put pads in a 300ex 04'. not sure how to adjust them. Its seems that the pads have pressure on them like the brakes are on? Its the rear brake. Any thoughts?

Posted by: Pappy

quote:
Originally posted by sunco
I put pads in a 300ex 04'. not sure how to adjust them. Its seems that the pads have pressure on them like the brakes are on? Its the rear brake. Any thoughts?

You need to compress the piston fully before installing the pads.

Posted by: f4istunna

great how to and pics. Should help alot of people that were kinda intimidated by something that is fairly simple

Do you take how to requests? lol

Posted by: tom416ex

I took my rear caliper apart on my 400 today. Its seized. It shouldnt be hard to rebuild it i hope, correct? Im being told that to have it rebuilt im looking at over 100 bucks. I can get the parts for around 25 bucks. Any imput would be great guys............

Posted by: Homerx

Just did one of my fronts. Its not hard at all, make sure you clean the O ring grove out really well, and oil the cylinder before reinsertion. GL

Posted by: nskukalek79

i tried rebuilding my rear caliper before and everything went great until i tried putting the seal on the float pin. i couldn't get it to set into the groove right or something cuz it just kept pushing out when i would screw the pin in ....is there a trick to this or just luck?

Posted by: Homerx

quote:
Originally posted by nskukalek79
i tried rebuilding my rear caliper before and everything went great until i tried putting the seal on the float pin. i couldn't get it to set into the groove right or something cuz it just kept pushing out when i would screw the pin in ....is there a trick to this or just luck?

If you over grease it, it will pop off.

Posted by: tom416ex

i rebuilt my rear caliper on my 400ex today. wasnt bad at all actually. saved myself about 80 bucks for labor at the honda dealership.. but my question to anyone here is...... when i put it back together. the busing pin is sliding back and forth. i dont remember if it was doing that when i took it apart. is that normal or did i do somehing wrong. or will it be better once it is bolted back up to the quad?

Posted by: Young_Gun1

I went to put new pads on the front on my 400ex but the slide pins are frozen and i can't get them to budge.
any ideas on how to get the bolts loose

Posted by: uchi

great writeup. i think i found this weekends project as my rear brakes have damn near stopped working. i plan on changing the brake fluid in mine aswell. can i simply pop out the brake pads with the brake line on the caliper and pump the rear brake to get the piston out? or is it better to blow air through it?

Posted by: Imbroke

i just rebuilt my rear caliper but for some reason it still doesnt work the brake pedal stays down when you push it down and the piston wont put any pressure on the pad

Posted by: Saul76

Here is a little tip - when you take out the rubber seals you're gunna find a crapload of corrosion. Take your blowtorch and lightly play the flame around inside the caliper cavity. You don't need to get it super hot.

This will turn about 95% of the corrosion to powder which will be much easier to scrape out and remove.

I also cut small 'tabs' of sandpaper a lil bigger then the tip of my index finger to clean the areas the piston slides on throughly ... you wanna make it shine.

I redid my TRX calipers yesterday and the amount of corrosion under the seals and inside the caliper shocked me. No wonder my pistons were not travelling in and out like they should.

Now - smooth as butter.

Posted by: Imbroke

it turns out that my caliper housing was cracked and let out the pressure when i pressed on the pedal so i bought a use one on craigslist for 10 bucks and rebuit it. and it deffinately helps if you take out all of the corrosion and get it super clean.