AP Racing 2-pot caliper images - LotusTalk - The Lotus Cars Community

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post #1 of 29 (permalink) Old 01-08-2017, 03:50 PM Thread Starter
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AP Racing 2-pot caliper images

Doing some refurbishment of my 2 piston AP racing calipers. Here are some images of the hardware that you can't see from the outside:

Piston diameter: 44.4mm


Piston design:


Piston outer surface is ground (possibly after hard anodizing):


Wiper on top, pressure seal below:


Anti-rattle pad:


P/N & S/N found on underside of inboard half:


Cracks found in all cross-tube fittings:


Other info:
Caliper to spindle fasteners: SHCS M10x1.5, 60mm long, Class 12.9
Caliper assembly fasteners: SHCS M10x1.5, 2X 70mm, 2X 55mm, Class 12.9
Bleed screws: M10x1.0, ~30mm long

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post #2 of 29 (permalink) Old 01-08-2017, 03:53 PM
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Very nice!! I see some wear on the piston and the line is cracked.....stating the obvious LOL.

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post #3 of 29 (permalink) Old 01-08-2017, 04:03 PM
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Looks like a single pot. Am I missing something?

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post #4 of 29 (permalink) Old 01-08-2017, 04:03 PM Thread Starter
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The line on the piston is more of a polished band. Can't feel any ridges or lips.

I'd bet my calipers aren't the only ones with split fittings on the cross-tubes.

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post #5 of 29 (permalink) Old 01-08-2017, 04:04 PM Thread Starter
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Originally Posted by oldmansan View Post
Looks like a single pot. Am I missing something?

San
2 pistons total. Not the optional 4-piston calipers for the Exige.

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post #6 of 29 (permalink) Old 01-09-2017, 12:46 AM
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Originally Posted by jdawson View Post
Doing some refurbishment of my 2 piston AP racing calipers. Here are some images of the hardware that you can't see from the outside:

Piston diameter: 44.4mm
It's actually 1.75", so it should be 44.45mm. Have you ever calibrated your caliper?

Whoever said that island life is great was never committed to Alcatraz...
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post #7 of 29 (permalink) Old 01-09-2017, 07:37 AM
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As usual, you are a meticulous man. Nice break down. SAN, it's a two piston caliper because there's a piston on each side of the disk. The caliper is not floating like the rear.
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post #8 of 29 (permalink) Old 01-10-2017, 09:14 AM Thread Starter
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Originally Posted by machine.gun.kelly View Post
It's actually 1.75", so it should be 44.45mm. Have you ever calibrated your caliper?
It's actually 44.41mm. I just single-point calibrated my $15 calipers against a set of in-cal Mitutoyo calipers... using this piston.


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post #9 of 29 (permalink) Old 01-10-2017, 07:07 PM
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Originally Posted by jdawson View Post
It's actually 44.41mm. I just single-point calibrated my $15 calipers against a set of in-cal Mitutoyo calipers... using this piston.

Go try to buy replacement parts for an AP Racing 44.41mm piston... You won't find any! My point is that AP Racing builds and sells a 1.75-inch piston...You can find and buy replacement parts for a 1.75-inch piston. I don't think we want to get into production tolerances here...

Whoever said that island life is great was never committed to Alcatraz...
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post #10 of 29 (permalink) Old 01-10-2017, 08:12 PM
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Quote:
Originally Posted by jdawson View Post
The line on the piston is more of a polished band. Can't feel any ridges or lips.

I'd bet my calipers aren't the only ones with split fittings on the cross-tubes.
Are you getting new cross-tubes, and from whom/where? I just started to refurb a pair of front calipers to mount at the rear of my Exige and while not cracked the fittings on my cross-tubes are deformed and rusty. Therefore, replacement is in order. Looks like I made a mistake not including these on my recent big ($$) order from Brexit-land.

BTW, all four pistons measure 1.748" per my old but accurate vernier caliper. Translates to 44.40mm. It is general AP practice for the dimensions listed in brake caliper specs to be the bore size, not piston. This is the case on every AP print that I have. MGK, you can check this yourself on the AP Racing website.

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post #11 of 29 (permalink) Old 01-10-2017, 08:43 PM Thread Starter
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Originally Posted by Formulabob View Post
Are you getting new cross-tubes, and from whom/where? I just started to refurb a pair of front calipers to mount at the rear of my Exige and while not cracked the fittings on my cross-tubes are deformed and rusty. Therefore, replacement is in order. Looks like I made a mistake not including these on my recent big ($$) order from Brexit-land.

BTW, all four pistons measure 1.748" per my old but accurate vernier caliper. Translates to 44.40mm. It is general AP practice for the dimensions listed in brake caliper specs to be the bore size, not piston. This is the case on every AP print that I have. MGK, you can check this yourself on the AP Racing website.

Bob L
The only place I've found replacement cross tubes is Eliseparts.com.

I know the pistons are nominally 1.75", I just figured people would like to know what their actual dimension is... and I kinda wanted to poke at Machine.gun.kelly I understand clearances, manufacturing tolerances, CTE, etc.

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post #12 of 29 (permalink) Old 01-10-2017, 08:57 PM
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lol... Good stuff.

If helpful, we have a nice vented stainless steel piston option and new seals on our website. in stock... the pistons are the correct size for the bore... what ever that is.


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post #13 of 29 (permalink) Old 01-10-2017, 09:13 PM
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Originally Posted by machine.gun.kelly View Post
Go try to buy replacement parts for an AP Racing 44.41mm piston... You won't find any! My point is that AP Racing builds and sells a 1.75-inch piston...You can find and buy replacement parts for a 1.75-inch piston. I don't think we want to get into production tolerances here...
I find that interesting since AP only specifies parts in metric and to only 1 significant figure....

https://www.apracing.com/product_det...olid_disc.aspx

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Last edited by Vulcan Grey; 01-10-2017 at 09:38 PM.
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post #14 of 29 (permalink) Old 01-10-2017, 09:45 PM Thread Starter
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Originally Posted by turbophil View Post
lol... Good stuff.

If helpful, we have a nice vented stainless steel piston option and new seals on our website. in stock... the pistons are the correct size for the bore... what ever that is.


Compliments of your AZ counterpart, Mr. Zust:

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post #15 of 29 (permalink) Old 01-10-2017, 09:49 PM
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Originally Posted by jdawson View Post


Compliments of your AZ counterpart, Mr. Zust:
Nice. Sometimes you have a part that looks so good you don't want to install it, you just want to hang it on the wall. The BWR Penske DAs were like that.

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post #16 of 29 (permalink) Old 01-10-2017, 10:06 PM
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Good stuff, good stuff..
Always interesting to see the naughty bits of our fine machine.

I feel like I need to refurb mine, too, soon, eventually~

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post #17 of 29 (permalink) Old 01-11-2017, 02:10 AM
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Originally Posted by Vulcan Grey View Post
I find that interesting since AP only specifies parts in metric and to only 1 significant figure....

https://www.apracing.com/product_det...olid_disc.aspx
That's only because you were too lazy to go to the download tab, download the customer installation drawing and RTFM...Or drawing in this case.

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post #18 of 29 (permalink) Old 01-11-2017, 07:01 AM
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Originally Posted by machine.gun.kelly View Post
That's only because you were too lazy to go to the download tab, download the customer installation drawing and RTFM...Or drawing in this case.
Yeaaaa..... the one that only says "TECHNICAL INFORMATION PISTON DIA : 2 X 44.5MM"?... The one on the download page? https://www.apracing.com/drawings/cp...-%20Sheet1.pdf

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post #19 of 29 (permalink) Old 01-13-2017, 12:26 AM
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Originally Posted by Vulcan Grey View Post
Yeaaaa..... the one that only says "TECHNICAL INFORMATION PISTON DIA : 2 X 44.5MM"?... The one on the download page? https://www.apracing.com/drawings/cp...-%20Sheet1.pdf
Would you be so kind to explain to us all why the only dimension on that drawing in "inches" is the piston diameter if that was not the piston diameter?

Whoever said that island life is great was never committed to Alcatraz...
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post #20 of 29 (permalink) Old 01-13-2017, 08:05 AM
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Dunno what you all are arguing about

It is called a 1.75 inch caliper, but the 'drawing' is not a 'drawing' it is a cartoon, derived from a production drawing, since it is full of REF dimensions, and no tolerance block, you do not have the information to make the parts.
Referencing the dimensions on the 'drawing' is kind of silly, since the piston is called 44.5 and the bore is called 44.45, methinks as referenced it would make a pretty lousy brake caliper. Since the bore is called more carefully in the cartoon[but in a blind view, no, not ever] it is probably something to the effect of 44.45 +.01mm -0 and the piston is probably something like 44.42mm +0 -.01mm, pretty much meaning that nothing is ever 1.75[or 1.7499965]

A 1/4-20 bolt is called that because that is its name, there is nothing on it that measures precisely 1/4 inch, it must be under .2500[.2489 max] or it won't fit in the 1/4-20 nut, which is very unlikely to ever have a dimension of .250.....

Let us not even get into 1/4 pipe......

IT is called a 1.75 inch caliper because that is what they call it, not because any dimension on it is precisely 1.75 inches, and the drawing is in mm because everything in the EU for pretty much 40 years has been metric, and a drawing is either metric or inch, never both. But who cares because I can just walk over to one of my machines and push a button and it will display in whichever units I please in whichever language I please[which is always English since I cannot read any of the others]
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