Jump to content

Brake upgrade options; comparative braking torque achieved


Guest ReattaCat

Recommended Posts

Guest ReattaCat

So, just for fun I ran the numbers on the various brake upgrade options I have seen applied here. They are:

1) Stock (baseline)

2)~12" rotor, aurora caliper frt., stock rear

3)~12" rotor, camaro calipers (LS-1), stock rear

4) ~12" rotor, corvette calipers (C-5), stock rear

5) All of the above with Seville rear brake conversion; ~11" rotor with Seville caliper

Summary:

First, all the gain in the best cases is due almost in toto to the larger rotors used; calipers were not a significant factor in torque gains. But, and this was interesting to me...one caliper option actually *lost* torque: the C-5 caliper/12" rotor option was found to deliver *less* torque than the stock caliper on a stock 10.25" rotor! IOW, the C-5 setup works out as a net loss in front braking torque from stock! So, this is due to this caliper being designed for a larger rotor (13") which probably explains the significantly smaller pistons compared to the other dualie, the LS-1 (40-55mm each piston, respectively). Looking into this a bit I found that the corvette guys use the camaro (LS-1) calipers as *their* brake upgrade from stock, lol! All of which is a real shame as the C-5 calipers are heads and tails above the LS-1 calipers vis a vis build quality.

So the percentages of braking torque gain/loss, based on stock as 100%, of the above systems (stock rear) are as follows:

1) stock 100%

2) aurora +19.8%

3) LS-1 +20.1

4) C-5 -5.5%

And the rear Seville upgrade alone:

+12.6%

And the combined four wheel system torque gains (with upgraded rear):

1) stock 100%

2) +17.9% (aurora)

3) +18.1 (LS-1)

4) -1% (C-5)

Figures used in calculator were as follows:

Stock: 2.5" piston diameter, 10.25 dia. rotor, frt; rear: 1.49" piston, 10.02" rotor

Aurora: 2.5" piton, 11.92" rotor

LS-1: 1.77" piston x2; 11.92" rotor

C-5: 1.57" piston x2; 11.92" rotor

Seville (rear); 1.49" piston; 11.06" rotor

All other variables uniformly constrained. (variables can be constrained at any level as long as they _all_ are; the relevant ratios will remain the same, though the raw numbers will change.)

So the winner, and not by much) is the LS-1 setup followed (and virtually indistinguishable from) the Aurora setup. Of course, the dual pistons offer less objective advantages over single piston setups as others have noted (primarily relating to reduced fade I suspect...).

BTW, the gain in _reduced_ pedal pressure (in the LS1 setup), torque constrained, runs about 5-8lbs at 50lbs nominal pedal pressure. So stock=50lbs pressure and equivalent torque with LS-1 upgrade would require only 42-45 lbs of pressure.

i'm glad i did this...as i was -this- close to pulling the trigger on a pair of 'vette calipers! (Which still bums me out...they are sooo nice otherwise.)

Incidental...Anyone know what the height of the COG is on the Reatta coupe? If I had that I could calculate the dynamic bias--which would be interesting.... Just guessing and using 20" for a COG height, it appears going significantly beyond these upgrades would risk potentially un-weighting the rear to the point of contact loss under heavy 1.25-1.5G braking (using with wider-than-stock modern street performance tires..) O.O There's apparently a whole pile of fwd dynamic transfer in these cars and it only gets worse if my 20" COG guess is low...which it likely is.

(Jake Latham's calculator used.)

Link to comment
Share on other sites

Guest Mc_Reatta

Similar to what I determined when I decided to upgrade.

The most significant factor that made me decide on the dual piston Camero option was that caliper is available in aluminum which significantly reduces unsprung weight, and also improves corrosion resistance.

Link to comment
Share on other sites

I did the rear brake upgrade but used 95-99 Riv. calipers which I believe to be the same as Park Avenue. I have since gone back to stock for a number of reasons.

1] The calipers were of poor condition [my fault for choosing poorly] and needed to be replaced

2] The calipers "locked" up on the rotors and had to be replaced as well.

3] I don't see myself ever selling my Reattas but didn't want the buyer to "wonder" what I had done when doing the brakes.

4] I never had a problem with the famous "rear brake rattle".

5] The Reatta I did [the Black] has 15" wheels and will always have 15" wheels so I could never go on to the fronts and "upgrade" and go to 16"

Link to comment
Share on other sites

I don't think there is sufficient reason for me to mess with upgrading the backs from what I have read. Oddly enough, I DID have the infamous rear wheel rattle until I recently did a rebuild of the brakes and for whatever reason, the rattle stopped completely. I don't have any plans to move away from my 15" original rims.

Link to comment
Share on other sites

Guest ReattaCat
the front brakes do like 80 percent of the braking.if i remember correctly. the only reason to modify back brakes is for the bling factor imo.

Here's the numbers on that question using LS1 setup:

Stock frt/rear braking ratio: 74/26

LS1 and stock rear: 78/22

LS1 and Seville rear: 76/24

The net increase in total braking torque gained by upgrading the rear with the seville setup with LS1 fronts vs LS1 and stock rear is +3%

So upgrading the rear gives you a ratio a bit closer to stock plus 3%. So yeh, mostly bling. But slotted & drilled plated rotors do look nice through more open wheels like I have and it's nice for everything to match frt & rear. And..since the name of the game is *optimize* so, i tell myself, why not just finish? ;)

Link to comment
Share on other sites

You can do the rear brake mod and maintain stock 15" wheels, but you are correct that the front upgrade requires 16" or larger wheels..

These should be a goo option while keeping the stock 15" rims. Also the rotors have the right bolt pattern I am not sure about the center opening but the cars that these fit would point to it being large enough. I think someone had done this a long time ago, but I could not find the post. They also would be easy to fine in yards to do the real tests.

You get the dual pistons and keep the stack rims.

http://www.ebay.com/itm/Disc-Brake-Caliper-Reman-A-1-Friction-Choice-Caliper-w-Bracket-Front-Left-/350872671745?pt=Motors_Car_Truck_Parts_Accessories&hash=item51b1a41601&vxp=mtr

Link to comment
Share on other sites

There have been other discussions that detail options that allow keeping the 15" wheels. You use 11" rotors instead of 12" and as I recall a couple of the options were Olds Alero, Pontiac Grand Am and the Chevy Ventura (small front drive) van. While it does not have the appeal of the 12" rotor, I believe it is almost "plug n play" as you do not need to drill the Reatta spindles for the mounting bolts. The Alero calipers are aluminum.... which save weight, but Harry commented that these were a problem in the rust belt as the corrode more than cast iron calipers.

Someone needs to write up a detailed presentation on all these conversions so Ronnie can post them and we don't reinvent the wheel once a year.

Link to comment
Share on other sites

There have been other discussions that detail options that allow keeping the 15" wheels. You use 11" rotors instead of 12" and as I recall a couple of the options were Olds Alero, Pontiac Grand Am and the Chevy Ventura (small front drive) van. While it does not have the appeal of the 12" rotor, I believe it is almost "plug n play" as you do not need to drill the Reatta spindles for the mounting bolts. The Alero calipers are aluminum.... which save weight, but Harry commented that these were a problem in the rust belt as the corrode more than cast iron calipers.

Someone needs to write up a detailed presentation on all these conversions so Ronnie can post them and we don't reinvent the wheel once a year.

I would be more than happy to post any brake upgrades that can be done by bolting on parts. For me to do it properly I need detailed instructions and part numbers (or some other way of identifying the specific parts that are needed). Photos are also helpful in the tutorials.

I don't feel comfortable posting brake upgrades that require drilling, cutting, welding or fabricating parts due to liability issues. I had a couple of good brake upgrades on ROJ for a while that required some fabrication of parts. I removed them on the recommendation of a friend who is an attorney.

Link to comment
Share on other sites

Guest Mc_Reatta
There have been other discussions that detail options that allow keeping the 15" wheels. You use 11" rotors instead of 12" The Alero calipers are aluminum.... which save weight, but Harry commented that these were a problem in the rust belt as the corrode more than cast iron calipers.

Surprised this option hasn't gotten more play on here.

This offers a promising alternative to anyone running stock wheels while gaining improved performance and opening up more current replacement parts to the stock calipers which are not stocked well at a lot of FLAPS now.

Who has performed this mod?

I would guess that to accommodate the larger rotor you would need to get the caliper mounting bracket from a donor car or vendor.

Need to confirm that that bracket will bolt directly to our spindle.

Need to confirm if our stock banjo bolt will work or a donor one is needed.

Since the offset of the caliper mounting position is smaller than the 12" conversion, I assume there would be no problem using the stock flex line.

Has anyone got these answers?

The performance increase of this conversion should turn out to be about half (10-12% vs 20%) of that of the 12" inch conversion which should appeal to many of us, along with the other benefits from improved thermal and weight improvements.

Think Barney's quote of Harry's comment about the "corrosion" of aluminum calipers should be more correctly stated as "erosion". Aluminum corrodes (oxidizes) less than steel under similar conditions, but it is much more reactive with acids and bases than steel. All that road salt used up there in the rust belt dissolves in the slush and melt and turns the water in to a very alkaline solution which eats away at the aluminum. So folks in the salt belt should probably stay away from aluminum calipers.

Link to comment
Share on other sites

I have modeled this using 2000 Grand Am parts from the salvage yard. I did not try hooking up the factory (Reatta) brake line and do not remember if it even has the same caliper end fitting.

If you go to www.rockauto.com and look at the front brakes for a 2000 Grand AM you can determine if there are other donors. Example, look at the Grand Am bracket and by clicking on the part number it shows the other vehicles that use the same part number, in this case... The Grand Am from 1999-2005, Cutlass 1997-1999, Olds Alero 1999-2004, Malibu 1997-2003.

Even if you are going to buy new (rebuilt) calipers you will need cores. You can usually by the used calipers at a pick n pull for less than the core charge. The bracket should be perfectly good used.

post-30596-14314235821_thumb.jpg

post-30596-143142358207_thumb.jpg

Link to comment
Share on other sites

Guest Mc_Reatta

So we just need to know if the stock banjo bolt will work, or like the Camero upgrade, you need a Camero banjo bolt.

Easy enough if your getting parts from a P&P.

Barney the list of cars you give appears to be for the single piston aluminum caliper.

There should be a similar sized dual piston steel version from 2000 ish Luminas as shown in the link that Daniel provided.

When I find the specs on the two, I'll try to document any differences, and if there is a clear winner between them or just go by what material you prefer them made from.

The cooling ribs used on those aluminum calipers may make them stick out further, so confirmation that there is good clearance with stock rims would be nice too.

Link to comment
Share on other sites

Guest Mc_Reatta

More information on these caliper upgrades:

The dual piston steel caliper was used in:

BUICK REGAL (1988 - 1996)

CHEVROLET LUMINA (1990 - 2001)

CHEVROLET MONTE CARLO (1995 - 1999)

OLDSMOBILE CUTLASS SUPREME (1988 - 1997)

PONTIAC GRAND PRIX (1988 - 1996)

The single piston aluminum caliper was used in:

CHEVROLET MALIBU (1997 - 2002)

OLDSMOBILE ALERO (1999 - 2002)

OLDSMOBILE CUTLASS (1998 - 1999)

PONTIAC GRAND AM (1999 - 2002)

Both calipers will require less travel and force on the brake pedal than stock to provide a given stopping force. The pedal travel required would be pretty indistinguishable between the two.

The dual piston caliper would give better performance due to several factors. It uses longer shorter pads which lie closer to the outer edge of the rotor, so for the same clamping force it will yield greater torque. It also spreads the clamping force more evenly over a greater area so it will have better thermal properties and pad wear properties than the single piston design.

So for all out performance I'd go with the dual piston design, but both will give a much better experience than the stock caliper..

If the lighter weight and differing corrosion properties of the aluminum caliper appeals to you, be warned that just like the aluminum Camero caliper you will need a different banjo bolt than stock. I believe this is due to the softer nature of the aluminum that they use a coarser thread pitch to prevent stripping. So you need to find a 10x1.0 mm bolt vs the stock 10x1.5 mm that is also used in the dual piston steel caliper.

Also you need to get the proper bracket that goes with the caliper you choose. Each type uses a different one.

When you go to mount the caliper to the bracket, make sure the bleeder screw is toward the top end of the caliper. This may require you to mount the indicated right hand (passenger) caliper on the left (drivers) side of your Reatta. This is required for using the Camero calipers to get them to bleed properly.

So now we just need a guinea pig to do this upgrade and document how it goes.

Edited by Mc_Reatta (see edit history)
Link to comment
Share on other sites

More information on these caliper upgrades:

If the lighter weight and differing corrosion properties of the aluminum caliper appeals to you, be warned that just like the aluminum Camero caliper you will need a different banjo bolt than stock. I believe this is due to the softer nature of the aluminum that they use a coarser thread pitch to prevent stripping. So you need to find a 10x1.0 mm bolt vs the stock 10x1.5 mm that is also used in the dual piston steel caliper.

.

go to advance auto and get the 13912 bolts from the 'help' section.the reatta bolts are much too short.i ripped out some threads from the caliper trying to use reatta length bolts.

Link to comment
Share on other sites

Guest ReattaCat
More information on these caliper upgrades:

The dual piston caliper would give better performance due to several factors. It uses longer shorter pads which lie closer to the outer edge of the rotor, so for the same clamping force it will yield greater torque.

Good point! I went back to the calculator to see what difference this makes. The factor is called "pad radial height" and it turns out to be significant. For the LS1 setup vs. stock, front only, the difference adds an additional +10% to the LS1 setup over stock (entirely from the stock setup's decrease in braking torque from using it's much larger pad radial height figure in the calculation rather than constraining this factor as before at 1.80" for all). Without this correction it was +20%. I used 1.8" radial height for the LS1 pads and 2.5" for the stock pads (corresponds to piston diameters). Also, applying this correction to the C-5 setup ends up giving it a 5% improvement over stock rather than -1% as before. (used pad radial height for the C-5 of 1.6", again reflecting piston diameter.) The C-5 is still the least optimal of these 12" rotor upgrades (needing 16" wheels).

I also ran the numbers on a Buick Regal Gran Sport's brakes: the rotor is 10.5" (1/4" larger than the Reatta stock rotor) and the calipers are dual with 1.65" pistons with a pad radial height of 1.70. They give 99% of the stock brake torque, so that upgrade is a wash (except for a probable improved fade characteristics , as you mentioned.)

Link to comment
Share on other sites

Guest Mc_Reatta

To add to my earlier post the two styles of calipers use slightly different size rotors. The twin piston ones are 0.3 inches larger in diameter, so get them to match the caliper.

Also, the aluminum calipers will fit a 15" wheel for sure as those cars came with then. But Luminas came stock with both 15 and 16" wheels in that era so they might be tight.

Edited by Mc_Reatta (see edit history)
Link to comment
Share on other sites

The 1st gen W-body Regal (88-96) did use 10.5" rotors in front. All Regals of that vintage had 4-wheel disk brakes. They also came stock with 14" wheels - with 15" and later 16" options. Maybe because of the 14" wheels, that is why GM felt the need for dual piston calipers in front? BTW in the 1990 Regal FSM they refer to these as "3242 front calipers".

The rear calipers in those cars were very problematic. The pistons would seize and the fronts would do all the work. Lots of threads on the W-body email list about them back in the day.

Link to comment
Share on other sites

Good point! I went back to the calculator to see what difference this makes. The factor is called "pad radial height" and it turns out to be significant. For the LS1 setup vs. stock, front only, the difference adds an additional +10% to the LS1 setup over stock (entirely from the stock setup's decrease in braking torque from using it's much larger pad radial height figure in the calculation rather than constraining this factor as before at 1.80" for all). Without this correction it was +20%. I used 1.8" radial height for the LS1 pads and 2.5" for the stock pads (corresponds to piston diameters). Also, applying this correction to the C-5 setup ends up giving it a 5% improvement over stock rather than -1% as before. (used pad radial height for the C-5 of 1.6", again reflecting piston diameter.) The C-5 is still the least optimal of these 12" rotor upgrades (needing 16" wheels).

I also ran the numbers on a Buick Regal Gran Sport's brakes: the rotor is 10.5" (1/4" larger than the Reatta stock rotor) and the calipers are dual with 1.65" pistons with a pad radial height of 1.70. They give 99% of the stock brake torque, so that upgrade is a wash (except for a probable improved fade characteristics , as you mentioned.)

check out this site.http://lukeskaff.com/?page_id=333

Link to comment
Share on other sites

Guest ReattaCat

Yep, saw that...nice not to have to fabricate/modify spindles, brackets, turn down rotors, etc, for our cars eh? We got it easy. ;)

...was looking at some of the modern setup..four and six piston brembos with 14-15.5" rotors?!? A Reatta would do stoppies with brakes like that, lo!

Edited by ReattaCat (see edit history)
Link to comment
Share on other sites

Guest Mc_Reatta

...was looking at some of the modern setup..four and six piston brembos with 14-15.5" rotors?!? A Reatta would do stoppies with brakes like that, lo!

Guess there is a reason to put those 20" rims on a Reatta after all. :rolleyes:

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...