Brake caliper piston won't go back in

[MvM]

Last week I noticed that my brake pads were finished so I wanted to replace them.
I removed the old pads and wanted to push the caliper pistons back in as the caliper won't fit over the new pads because these are, of course, much thicker than the old ones.

The lower brake caliper piston went it with no problem. During this, the upper piston came out quite a distance.
And for some reason, I don't seem to be able to push it back in. I am using a C-clamp for this, but it simpley won't move. The boots seem to be fine, no tears or slits, but the piston doesn't want to move back in.

Now, before I start using a really big C-clamp, does anyone have any advice on what I might check first before I start tearing things up by accident ??

 

[sptrader]

Be sure that you open the brake bleeder screw BEFORE compressing the pistons ! (The brake fluid needs some place to go.)

 

[lqqky]

If it's the rear brakes the piston has to be screwed in not pushed.

 

[03 raw nsx]

did you open your brake fluid reservoir?

 

[BioBanker]

Yep - I learned the hard way that you cant push the rear pistons in, TURN them.

But be careful what you turn them with. I was in a pinch so I took some needle nose pliers and spread them an inch or so and that worked. There is a tool made to do this.

I bent my C Clamp trying to get it back in!!!

 

[L8apex32]

Did you try pushing in just one piston at a time?

The goal is to push both in at the same time. The fluid will be pushed back up into the reservoir - or you can open a bleed screw to let it out.

I imagine that there is a chance that one of the pistons could come out too far and then not be back in line correctly, if you just pushed on at a time.

If you didn't do this before, here is a way to do it. I put one of the old pads back in the caliper, backwards, then push on it with the C-clamp. This pushes both pistons back in at the same time.

Hope this helps.

 

[goldNSX]

MvM is talking about the front calipers as they have two piston (the rears are screwed back). Usually it's not necessary to open the bleeding screw but in the case of two pistons if you push back one by one and not both together it's helpful to avoid that the other piston moves out while you push the other in. I think what happened to your piston is (yes, it's my nightmare, don't ask me how I know, ok 20 years back) that your larger piston moved even more outward than it already was and now is stuck. This is the least comfortable scenario but not sure if this happened. Don't put brute force on it! This way you'll be changing the caliper in the end. If my guessed scenario holds you'll need an input of someone who restored his calipers.

For turning the rear pistons I hope to do a pic of the 'tools' I've used. Cheap trick but very, very save.

 

[Larry Bastanza]

I always pus them both in together using a small block of wood. You may have extended your one piston out past the seal, and this is why it is tough to get back in. Just make sure it is not cocked on the bore, if it is straight, it just may take a little persuasion to get it back in.

HTH,
LarryB

 

[slamstrom]

Invest in one of these
http://www.partsamerica.com/ProductDetail.aspx?MfrCode=PBI&MfrPartNumber=648412&CategoryCode=3479
Less than $10.00 with tax. Works better than a C-clamp.
http://www.partsamerica.com/ProductDetail.aspx?MfrCode=PBI&MfrPartNumber=648410&CategoryCode=3479
About the same price.
I used to use a C-clamp to compress the piston, but the block of wood keeps falling. After getting the items above, changing brake pads are quick & easy. Good luck.

 

[MvM]

Thanks for all the suggestions.

Usually, I never have a problem with the pistons.

In the past, I used a block of wood also, but like many, it would fall out all the time. That's why I started to do it piston by piston.
I will check things tomorrow again, perhaps the piston did in fact come out too far.

 

[Swift]

C-clamp is good but also a better way is to use the old brake pad and old it in position and you a tall visegrips...and make sure the one end is kinda in the center therefore you are putting equal pressure on both pistons they should go it relatively easy. if not....then they are binding or stuck.

On my one type 2 caliper(similiar) i got rebuilt the one rubber boot wasnt sealing properly and in rain or humid weather the piston would get rusty and bind if i wasnt driving the car. You can attempt to fix yourself if careful by wire brushing pistons and cleaning out surface on caliper with wire brush and lubing everything during assembly.

good luck

 

[MvM]

Ok guys, problem is solved.

I guess the second piston did in fact come out too far. So I ended up opening the bleeding nipple a little. Then it was easy to push in the piston by hand.
Guess it was a nice demonstration to see the power of hydraulics at work :smile:

Pads are changed, brake fluid filled up again and now I am taking the car out to brake the pads in.

 

[goldNSX]

Ok guys, problem is solved.

I guess the second piston did in fact come out too far. So I ended up opening the bleeding nipple a little. Then it was easy to push in the piston by hand.
Guess it was a nice demonstration to see the power of hydraulics at work :smile:

Pads are changed, brake fluid filled up again and now I am taking the car out to brake the pads in.

Lucky you! Just wondering: Did you install HP+ again?

 

[MvM]

Lucky you! Just wondering: Did you install HP+ again?

Thanks!
Actually, I did not. I still had a pair of Axxis Ultimate pads in the house, so that's what I put on this time. Those I must say, so far, braking is significantly less agressive.

On a side note, I also noticed that I have worn down my rotors much more than I thought. The rotors are the Racing Brake slotted rotors, and the slots are practically gone. Completely out of sight on the right side and only about 0.2-0.4 mm left on the left side. This is on the front mind you. The rears are ok.
I guess I am in for a new set of rotors as well Hmm, maybe I should try and be a little easier on the brakes with the next set.

 

[goldNSX]

On a side note, I also noticed that I have worn down my rotors much more than I thought. The rotors are the Racing Brake slotted rotors, and the slots are practically gone. Completely out of sight on the right side and only about 0.2-0.4 mm left on the left side. This is on the front mind you. The rears are ok.
I guess I am in for a new set of rotors as well Hmm, maybe I should try and be a little easier on the brakes with the next set.

There are other reasons than hard braking in your scenario. Could it be that the Racing brake discs are much more prone to wear. The slots remind me of rotating knifes which eat up the pads like a big salami (sorry for the comparison :tongue:)

 

[rsevo6]

Thanks!

On a side note, I also noticed that I have worn down my rotors much more than I thought. The rotors are the Racing Brake slotted rotors, and the slots are practically gone. Completely out of sight on the right side and only about 0.2-0.4 mm left on the left side. This is on the front mind you. The rears are ok.
I guess I am in for a new set of rotors as well Hmm, maybe I should try and be a little easier on the brakes with the next set.

This kind of wear on the RB BB discs is rediculous IMHO
We installed them on your car about 6-7 months How many Km's of use? cannot be more than 5-6K Km, no track use.
No matter what pads you have used, superfast wear like this with only street use cannot be acceptable.
I would certainly get into contact with Chris at SOS!!

This makes me wonder on the BB RB discs that I ordered together with you and which are still in the box as I saved them for my new recently titled CTSC NSX. If after install ( I will probably do this in a month or so) they wear as fast as yours, I will be VERY unhappy and will be putting in a claim with with SOS for sure.

Perhaps they have had a bad batch?? If so, I will have the same bad ones as you as we ordered them together.

Please keep us updated.
Good luck!

 

[goldNSX]

I guess it has much more to do with the ultimate hard braking IMO.

 

[MvM]

This kind of wear on the RB BB discs is rediculous IMHO
We installed them on your car about 6-7 months How many Km's of use? cannot be more than 5-6K Km, no track use.
No matter what pads you have used, superfast wear like this with only street use cannot be acceptable.
I would certainly get into contact with Chris at SOS!!

This makes me wonder on the BB RB discs that I ordered together with you and which are still in the box as I saved them for my new recently titled CTSC NSX. If after install ( I will probably do this in a month or so) they wear as fast as yours, I will be VERY unhappy and will be putting in a claim with with SOS for sure.

Perhaps they have had a bad batch?? If so, I will have the same bad ones as you as we ordered them together.

I have driven the car about 12000 km (about 7500 miles) with the new brakes and pads.

And yes, I have been surprised with the speed both the pads and rotors were worn down. And yes, I do use my brakes to their full potential, but as they were used on the public roads, they don't get hot as they would on a track.

It could also be that the slots in these rotors are not as deep as they are on other rotors, meaning that they are worn down more quickly. I haven't been able to measure the remaining thickness of the rotors but I will let you know.

In the meantime, I will ask ScienceofSpeed what the normal life expectancy should be off these rotoros.

 

[rsevo6]

Your OE discs were only replaced because you wanted better braking of a BB kit, not because of disc wear right? So one may conclude that your OE discs held up a lot longer with same driving style?

Normal disc life expectancy (with street use) should be a lot more than 12.000 Km.
Especially because the BB uses a bigger braking surface and as such should get lesser wear than with original disc size.
When buying these discs at more than double the price of OE replacements I do feel one may expect them to outperform the OE discs and last at least as long with same use!

OE discs (with heavy braking on street use) usually last 40-80K Km (unless they are prematurely replaced because of warping).

Seems to me the steel quality used for the RB BB discs may be too soft and this possibly combined with very hard/abrasive pads has caused this extreme wear.
Am very interested in reaction from SOS/ RB.

As there are more of these discs in use, perhaps making a seperate forum topic finding out the wear rate with other users might be a good thing?

Please measure the disc thickness on your discs and let's compare this with the new discs I have, so we can determine how much wear is on them.

 

[goldNSX]

Just wondering: Are brake discs treated in any way to last longer?

 

[rsevo6]

Just wondering: Are brake discs treated in any way to last longer?

Normally no!
Some producers offer several coatings, but these are only to prevent rust.

Some producers such as Brembo, offer discs which have undergone a heat treating process which should increase the resistance to "warping"

Also there is a process called "cryo treating" during which the discs are deepfrozen (I think to -/- 180 C). This changes/densifies the molecular structure and hardens the material.
Discs treated this way should be much harder (less wearing) and have a lot less chance of "warping"