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Cadillac V-Sport General Discussion Discussion, V rear calipers on a Vsport? Will it work? in Cadillac CTS V-Sport; Originally Posted by pissedoffwookiee and the size of the floating caliper piston?....since OP doesn't like the look of the floating ...
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    Re: V rear calipers on a Vsport? Will it work?

    Quote Originally Posted by pissedoffwookiee View Post
    and the size of the floating caliper piston?....since OP doesn't like the look of the floating and wants a brake upgrade to correct the issue....i suspect your arguments are moot because he can't help but increase 'effective' piston area because he'd be adding an entirely unused size....case in point....a typical GM floating piston is around 40-45 mm this will give an area of 1589 mm (using 45mm to be generous to your argument) and the dual pot brembos i suggested looking into are 2x36 mm which gives us an area of 2034 mm....which takes us right back to the beginning before this effective area talk.....this change leads to more pistons, which changes the equation for the entire braking system, which could get weird
    Piston count non-issue aside, your math is wrong; as stated earlier, you have to double the sliding caliper piston area to come up with effective area. The single 45mm piston in a slider would give you an effective area of 3179 sq mm. Your 2x36 is going to be woefully inadequate.

    But FWIW, I don't think the V-Sport piston is that big. I can't find that diameter with a few quick searches, but based on a quick eyeball of the externals, and a data table of rear sliding caliper single piston diameters for GM cars over the past 30 or so years, I'd wager it's closer to 40mm, give or take a couple. A 40 mm piston calculates to 1256 x 2 = 2512 sq mm. A two piston fixed caliper would of course have to be the same 40 mm diameter for the same clamping force. A 4 pot fixed caliper with 28mm pistons would be within about 2 percent of the same area. Either of those would certainly be within the realm of available aftermarket caliper configurations. But the mounting bracket pieces would most likely be the long pole in the tent... I checked Wilwood for instance, and they have no bracket kits for the CTS, front or rear.

    I'm sticking with my original statement, quoted here for your convenience "But you have to remember it's total piston area per caliper that's the key factor, regardless of pot count...."


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    Re: V rear calipers on a Vsport? Will it work?

    Quote Originally Posted by Denrael View Post
    Piston count non-issue aside, your math is wrong; as stated earlier, you have to double the sliding caliper piston area to come up with effective area. The single 45mm piston in a slider would give you an effective area of 3179 sq mm. Your 2x36 is going to be woefully inadequate.

    But FWIW, I don't think the V-Sport piston is that big. I can't find that diameter with a few quick searches, but based on a quick eyeball of the externals, and a data table of rear sliding caliper single piston diameters for GM cars over the past 30 or so years, I'd wager it's closer to 40mm, give or take a couple. A 40 mm piston calculates to 1256 x 2 = 2512 sq mm. A two piston fixed caliper would of course have to be the same 40 mm diameter for the same clamping force. A 4 pot fixed caliper with 28mm pistons would be within about 2 percent of the same area. Either of those would certainly be within the realm of available aftermarket caliper configurations. But the mounting bracket pieces would most likely be the long pole in the tent... I checked Wilwood for instance, and they have no bracket kits for the CTS, front or rear.

    I'm sticking with my original statement, quoted here for your convenience "But you have to remember it's total piston area per caliper that's the key factor, regardless of pot count...."
    don't know how you are figuring piston area but according to THIS a 40mm piston has an area of 1256mm and a 45mm piston has an area of 1589 by their definition....so unless math has suddenly changed and calculating the area of a circle is no longer a=pi(r*r) "Lucy!..Ju got some 'splainin to do" because 1589 is way far off of your 3179

    here is another cool table of piston areas

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    Re: V rear calipers on a Vsport? Will it work?

    Quote Originally Posted by pissedoffwookiee View Post
    don't know how you are figuring piston area but according to THIS a 40mm piston has an area of 1256mm and a 45mm piston has an area of 1589 by their definition....so unless math has suddenly changed and calculating the area of a circle is no longer a=pi(r*r) "Lucy!..Ju got some 'splainin to do" because 1589 is way far off of your 3179

    here is another cool table of piston areas
    I'm calculating piston area just like everyone else, but for the sliding/floating caliper (also just like everyone else), I'm doubling the area in order to compare it on a level playing field with the total area of a multiple-pot fixed caliper. I've mentioned this many times during this conversation, but for some reason, you choose to ignore it. Whatever.

    Here's the math for total piston area of the two calipers you mentioned:

    45mm single piston, floating caliper: 2 x 1589.6 = 3189.2 sq mm
    36mm double piston, fixed caliper: 2 x 1037.4 = 2034.7 sq mm

    But when comparing piston areas, engineers more typically just use the area for the pistons in one side of the caliper:

    45mm single piston, floating caliper: 1 x 1589.6 sq mm
    36mm double piston, fixed caliper: 1 x 1017.4 sq mm

    To repeat... your 2x36 fixed will not even come close to generating the stopping power of the 45mm floater.

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    Re: V rear calipers on a Vsport? Will it work?

    Quote Originally Posted by Denrael View Post
    I'm calculating piston area just like everyone else, but for the sliding/floating caliper (also just like everyone else), I'm doubling the area in order to compare it on a level playing field with the total area of a multiple-pot fixed caliper. I've mentioned this many times during this conversation, but for some reason, you choose to ignore it. Whatever.

    Here's the math for total piston area of the two calipers you mentioned:

    45mm single piston, floating caliper: 2 x 1589.6 = 3189.2 sq mm
    36mm double piston, fixed caliper: 2 x 1037.4 = 2034.7 sq mm

    But when comparing piston areas, engineers more typically just use the area for the pistons in one side of the caliper:

    45mm single piston, floating caliper: 1 x 1589.6 sq mm
    36mm double piston, fixed caliper: 1 x 1017.4 sq mm

    To repeat... your 2x36 fixed will not even come close to generating the stopping power of the 45mm floater.
    THESE FOLKS disagree with you

    so do these folks

    and the SAE make no mention of phantom (effective) pistons in floating calipers, only that PISTON AREA contributes to force not effective

    and this engineer doesn't talk effective either

    but these guys agree with you partly, they do the single side method of calculation, but no mention of doubling sliding caliper area

    so

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    Re: V rear calipers on a Vsport? Will it work?

    Quote Originally Posted by pissedoffwookiee View Post
    THESE FOLKS disagree with you

    so do these folks

    and the SAE make no mention of phantom (effective) pistons in floating calipers, only that PISTON AREA contributes to force not effective

    and this engineer doesn't talk effective either

    but these guys agree with you partly, they do the single side method of calculation, but no mention of doubling sliding caliper area

    so
    In the first four examples, the fact it's not mentioned is certainly not proof that it's not valid. But from the 5th link (where you say they "partly" agree with me), they do mention it, you just have to be able to read and comprehend. Here's the quote from the Wilwood paper:

    "A calipers piston area is calculated by finding the total piston area from one side of the caliper (this is true for a single piston caliper also)." (underscore emphasis mine)

    What this says is that if you want to compare floating and fixed caliper piston areas on an even basis, you only look at one half of the caliper - ignoring the fact the floating caliper only has piston(s) in one side.

    I did a quick search on the subject and came up with this site which deals with actual calculations. It very clearly spells out the need to double the piston area on floating calipers. In fact it's mentioned twice...

    ----------
    Edit:

    And another calculator complete with a note (under "Terms and Values Explained") that states exactly what I've been saying from the get-go. Here's the quote:

    "Note: multi piston calipers express their values using one HALF of the caliper body. This accounts for the floating aspect of the single piston caliper. A six pot caliper would be 1.625/1.125/1.125" for example. True clamping force would be double that but also double the single piston of a floating caliper taking into account the 'pull' of the outer pad to the rotor surface. Using total area (all six for example) would require you double that of the floating caliper also- thus the net result is the same whichever way you do it."

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    Re: V rear calipers on a Vsport? Will it work?

    Quote Originally Posted by Denrael View Post
    In the first four examples, the fact it's not mentioned is certainly not proof that it's not valid. But from the 5th link (where you say they "partly" agree with me), they do mention it, you just have to be able to read and comprehend. Here's the quote from the Wilwood paper:

    "A calipers piston area is calculated by finding the total piston area from one side of the caliper (this is true for a single piston caliper also)." (underscore emphasis mine)

    What this says is that if you want to compare floating and fixed caliper piston areas on an even basis, you only look at one half of the caliper - ignoring the fact the floating caliper only has piston(s) in one side.

    I did a quick search on the subject and came up with this site which deals with actual calculations. It very clearly spells out the need to double the piston area on floating calipers. In fact it's mentioned twice...

    ----------
    Edit:

    And another calculator complete with a note (under "Terms and Values Explained") that states exactly what I've been saying from the get-go. Here's the quote:

    "Note: multi piston calipers express their values using one HALF of the caliper body. This accounts for the floating aspect of the single piston caliper. A six pot caliper would be 1.625/1.125/1.125" for example. True clamping force would be double that but also double the single piston of a floating caliper taking into account the 'pull' of the outer pad to the rotor surface. Using total area (all six for example) would require you double that of the floating caliper also- thus the net result is the same whichever way you do it."
    if by comprehend you mean make up stuff they didn't say, you'd be right...but like i said they partly agree with you by saying one side, but they don't say multiply by two, and neither does your quote from them say it....you were reaching on that one

    in the end we have differing information hence the

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    Re: V rear calipers on a Vsport? Will it work?

    Quote Originally Posted by pissedoffwookiee View Post
    if by comprehend you mean make up stuff they didn't say, you'd be right...but like i said they partly agree with you by saying one side, but they don't say multiply by two, and neither does your quote from them say it....you were reaching on that one

    in the end we have differing information hence the
    Actually, in the end we have you refusing to believe something that is pretty much 6th grade physics. What's your opinion of the other two quotes I pointed out... the ones associated with caliper piston area calculators? They made that stuff up too?

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    Re: V rear calipers on a Vsport? Will it work?

    Quote Originally Posted by Garycoral View Post
    I was considering picking up a pair of V2 rear calipers and swapping for the stock units - Anybody know if it's a direct swap??
    Direct swap meaning what? If you mean change nothing but the caliper, no, it's not a direct swap - the V2 rear rotors are 365mm diameter vs 315mm diameter for the VSport. So, even without knowing how the offsets of the calipers compare, or how the mounting bolt spacing compares, we know that the V2 caliper would not work with the VSport rotors. You'd need the V2 rotors to match up to the calipers, but to use those you'd need to know if the parking brake diameter is the same, and if the rotor/hub offset would match up right.

    Basically, I think the only way to answer the questions would be to buy the parts and do a test fit. A V2 rear caliper can be had for ~$165 via Amazon Prime - take some measurements, return it if you end up not needing it. You'd just be out the shipping cost. A rear rotor can be had for ~$35; again, if you don't need it, return it.


    Quote Originally Posted by pissedoffwookiee View Post
    This...,,if you want V brakes do all of it....rotors and calipers, front and rear....or at minimum if the rotors are compatible calipers only.....otherwise your monkeying with a Nurburgring tuned brake setup, no need to throw that out of whack, plus you'd also likely be throwing stabilitrak and ABS out of whack too....going from a single piston sliding caliper to a 4 piston unit is a huge change and balance will be changed for some weirdness, partly due to clamping power, and partly due change in fluid use..... the amount of fluid used to move 4 Pistons vs 1 would at least triple and change pedal travel and add mushiness.
    Without knowing the piston diameters involved you can't make that sort of statement.

    Quote Originally Posted by pissedoffwookiee View Post
    in that case i wouldn't even bother with trying to figure out Cadillac OEM Brembos and call a brembo distributor and get some 2 pot calipers that fit the V-Sport
    Attachment 410049
    Did you bother to check to see if Brembo even offers such a thing?

    Quote Originally Posted by pissedoffwookiee View Post
    remember, the V-Sport front caliper is essentially the V rear caliper
    No, it isn't. The VSport front caliper is significantly larger. Compare a FMSI D1001 pad vs a D592 pad and you'll see.

    Quote Originally Posted by pissedoffwookiee View Post
    so doing 4 pot in the front and 4 pot in the rear could get weird for the car but 2 pot rear and 4 pot front is a common pairing.
    Again, the number of pistons has nothing to do with this, it's the area of the pistons that matters. My V1 came from the factory with 4-piston Brembos front and rear and that wasn't weird at all.

    Quote Originally Posted by pissedoffwookiee View Post
    it's actually more than piston area....it's piston area, volume of fluid required for a given travel of pistons in calipers (slave), # of pistons,
    All of which is the same thing.

    Quote Originally Posted by pissedoffwookiee View Post
    volume of fluid displaced by plunger/piston (master), leverage applied to plunger (travel & length of lever which is typically a brake pedal or brake lever) , and force applied to lever.....its because of these factors i said the brakes will get weird
    How are any of these factors being affected by changing the rear calipers?

    Quote Originally Posted by pissedoffwookiee View Post
    if by comprehend you mean make up stuff they didn't say, you'd be right...but like i said they partly agree with you by saying one side, but they don't say multiply by two, and neither does your quote from them say it....you were reaching on that one

    in the end we have differing information hence the
    Denrael is correct, you are not. If you understand how a sliding caliper works then it's obvious why you have to double the piston area; the force generated by the piston(s) acts on both sides of the rotor. So when you're comparing fixed vs sliding calipers, you either double the sliding caliper's piston area, or you only use 1 side of the fixed caliper.
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    Re: V rear calipers on a Vsport? Will it work?

    As for comparing the V2 rear setup to the VSport rear setup, you'd need to do the math like I did before installing V2 fronts on my V1 - http://www.cadillacforums.com/forums...ml#post2733225.
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    Re: V rear calipers on a Vsport? Will it work?

    Meanwhile, even ignoring the dimensional aspects (mount bolt spacing, offsets, parking brake, etc.), I think we have an answer to the OP's question. It appears the V-Sport rear caliper piston is 43 mm, so that puts us at 1451 sq mm, vs the V2's 28/32 mm pistons at 1419. This is only 2+% less area with the V2 caliper; not a bad match, so far, so good. But assuming we use the matching 365mm V2 rotor, we introduce a 50mm difference in diameter, which is going to upset the balance significantly. I don't know the exact effective radii (measured at the center of the respective pads) of the two setups, but my guess is it would be enough to generate something on the order of a 15-20% increase in braking torque. Not good... at least not without a corresponding braking torque increase at the front end of the car.

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    Re: V rear calipers on a Vsport? Will it work?


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    Re: V rear calipers on a Vsport? Will it work?

    I respectfully withdraw my question...
    duneless and KRDCAD like this.

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    Re: V rear calipers on a Vsport? Will it work?

    This is good stuff though. It gives us answers from people that know their stuff. A debate is always good because the best answers will come out in the end. I'm not a brake caliper genius so I like to hear all aspects of a debate. I won't really know though until I see someone change out the rear calipers because this is something I would like to do.

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    Re: V rear calipers on a Vsport? Will it work?

    I was just re-thinking this... Any other ideas on this out there? I really would like to give it a shot.

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    Re: V rear calipers on a Vsport? Will it work?

    I was told by an engineer very familiar with the system that it is. In addition, the current gen rear Camaro SS caliper is a direct swap and so is the current gen rear Corvette caliper on base models. I have installed the later on mine - pictures forthcoming. BTW - HOW do you get pictures uploaded here. Every time I try it says they are too big?!

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