slight brake upgrade ? ammended to a source of OE calipers

[lotustonybassplayer]

just purchased i received some front calipers from rockauto part no's kelsey-hayes 4013008 and 4013007 they are from a 1989 Pontiac lemans 2.0l .they cost £14.64 each plus posting got hit for the vat and parcelforce charge. They have a 54mm piston and come with brake pads and new bolts . they have a 7616 bracket. I trial fitted one today the only difference was that the bleed nipple was at the bottom. The pad pins on one caliper was the standard type and the other had pins with R clips. my observations was that the fitted under the standard 15" wheels. With the pads that came with the caliper the were below the rim of the disk and the ferodo pads that are on the car now were slightly above the rim maybe 2mm. Thoughts anyone posting some pics on the facebook page as it's easier for me

[Brit-Car-Nut]

The bleed nipple has to be at the top if you ever expect to get all the air out of them. Are you sure you you are putting the calipers on the correct side? In the US, it is probable the calipers mounted on the REAR of the upright, so the one marked left is really the M100 right.

If you want to post some pictures here, you can send them to me and I will put them up for you.

[lotustonybassplayer]

Aha that would make sense !i just tried it with being able to read the 7616 the right way up as on the original caliper as fitted on the hub. i did think the bleed nipple should be at the top ! i will try the other caliper tomorrow and take a pic in situ. any thoughts on the slight overhang of the pads ?

[Brit-Car-Nut]

Sorry for being ignorant, but what size are the pistons in the OEM/Standard front calipers? I am finding too many different measurements to know what to believe. I suppose I could pull one off my car, but that means I have to actually work on it. Is 46mm right? 48mm? 54mm?

I am hoping Dave P. has that info right on the tip of his typing finger, so please confirm the real answer. Over the years, I have ordered several caliper sets (to have spares for when I ever reassemble my car) and I am now trying to figure out what I really have on hand.

Thanks.
Sorry for hijacking your thread Tony...

[lotustonybassplayer]

No problem John , I thought it was a 52mm caliper that was fitted , hence my slight upgrade heading as these are 54mm. I' m sure someone will be along with a definitive answer

[Brit-Car-Nut]

I think that the 54mm might be a good choice since everyone was getting the smaller bore BMC a while ago because it gave a better "feel". Smaller BMC or larger caliper piston is about the same in concept.

I hope Dave or someone comes back with the real piston size so we will know which ones to jump on since there are very few left.

Have a good night...

[Rambo]

The bleed nipple has to be at the top if you ever expect to get all the air out of them

Totally agree. You'll never get the air out with bleed nipples at the bottom

PS from memory, piston size on OEM was 46 or 48 (not 52 or 54 mm) Unfortunately I don't have any Vernier calipers to give you an accurate measurement

[dapinky]

Well, as many of you know, the answer *should* be 42 .......

...... but for this particular question, it is 52mm.

(if anyone wants the math(s), then the 1mm extra on the radius will give an increase in surface area of 167mm2 (each caliper) - so 334mm2 in total - it works out as an increase of approx 7.8%, so will use minimal extra fluid to achieve the same latteral movement - well within the capacity of the whole system, and only a slight difference in overall brake pedal movement/feel)

[Brit-Car-Nut]

Sorry, changed my train of thought and crashed.

[Rambo]

I just measured the piston on an old OEM caliper with a ruler and it was approx. 47 mm. WTF

Confused

[dapinky]

I just measured the piston on an old OEM caliper with a ruler and it was approx. 47 mm. WTF

Confused

Mark,

Did you measure across the exposed face (which bears on the pad) or across the main body of the piston (which acts against the rubber seal)? - the 2 measurements are different.

[lotustonybassplayer]

just posted a few pics on facebook of the pads fitted to the caliper whilst it bolted to the hub. (the caliper is fitted the right way up bleed nipple at the top ) you will see that the ferodo original pad and the pad that came with caliper does not reach the inner part of the disc surface, how ever when i fitted the new pad to the old caliper it fitted perfectly ! not sure if this would be an issue as the pad has full contact with disc. i guess the disc would have a inner unworn lip over time, but as disc are cheap i'm thinking having to change the pads and discs would not cost the earth.

[Simon_P]

Tony,

Is that a measured 54mm or just what is said on the ad.? all the others are 48 solid disc and 52 mm vented disc.

[lotustonybassplayer]

Simon, the 48mm vented is for the 1.6L the 54mm is for the 2.0l if you look at the pic for the 48mm one it does not have the 7616 bracket. It has i think a 4353 stamped on the bracket hope this helps. Tony

[Simon_P]

Hi Tony,
I asked if you had measured as where dimensions are given they are either 48 mm for solid disc or 52mm for vented disc, only the one you mention says 54mm

I only looked at the 2.0l.

I'm just asking out of interest.

[Bern]

I'm thinking of upgrading my brakes, how much of a difference has this made?

Cheers,

Bern.

[lotusflasherman]

just posted a few pics on facebook of the pads fitted to the caliper whilst it bolted to the hub. (the caliper is fitted the right way up bleed nipple at the top ) you will see that the ferodo original pad and the pad that came with caliper does not reach the inner part of the disc surface, how ever when i fitted the new pad to the old caliper it fitted perfectly ! not sure if this would be an issue as the pad has full contact with disc. i guess the disc would have a inner unworn lip over time, but as disc are cheap i'm thinking having to change the pads and discs would not cost the earth.

Tony, I've looked at the facebook pics and to answer your question about ' unworn inner lips ' ... the braking torque from the pads is greater on the outer edge of the disc than the inner edge and the bigger the disc the greater the braking torque can be achieved so performance cars have very big discs but pads don't go right to the inside edge, there's more advantage in increasing the sector of the disc the pads cover than going further in towards the hub, so it's quite common for a lip to develop on the unused part of the disc.

Last Friday I was sorting out the brakes on my daughter-in-law's Astra SRi (2l turbo with 197 bhp) and took photos to send to my son to show him some new discs were needed. These are standard SRi 308mm diameter & here's an example of an unworn inner lip where the pads don't cover the full disc... there's a bit of an outer lip as well..

20170623_131858.jpg

.. so you've got nothing to worry about, in fact the inner lip helps you see how much the disc has worn without having to get calipers out to measure it ..

Have you checked that your new pads & calipers don't overhang the outside of the discs? If they do you can get an unworn lip on the pads which can be dangerous if not removed - if discs are worn thin and the lips on the pads allowed to get large they can make contact with each other and prevent the pads fully squeezing the disc ... so brake pedal feels fine but not a lot of slowing down occurring ...

[lotustonybassplayer]

Phil the pads that came with caliper are fine at the outer edge, my original ferodo pads on the car at the moment over hang the outer maybe 1or 2mm when fitted to the new caliper but i didn't fit the springs, i don't know if that makes a difference . i still need to get the piston measured to see if indeed they are 54mm.

[lotusflasherman]

i still need to get the piston measured to see if indeed they are 54mm.

These are quite handy to have in the toolbox, LCD-DIGITAL-VERNIER-CARBON-FIBER-COMPOSITE-CALIPER-MICROMETER

read accurately to 0.1mm and much easier to read than my micrometers - it's the age related eyesight problem...

[lotustonybassplayer]

I'm thinking of upgrading my brakes, how much of a difference has this made?

Cheers,

Bern.

Bern i have not fitted them permanently yet so cannot offer any answer to your question . At just over £70 delivered from rockauto I bought these really just to see if they would fit which they do on the hub under the standard 15" wheels. I have yet to confirm they are 54mm pistons as stated either. so i am holding off fitting yet as my local mot man is going to let me use the brake testing rollers to get some before detailed figures so i have a benchmark. Tony