Racing Brakes Rear Bias Kit Evaluation

[ViperGeorge]

So I ordered the Racing Brakes Rear Reduced bias kit for my 15 TA. I was told it would reduce/eliminate the rear end wiggle under heavy braking. Guess what? It worked. I installed the new calipers on Thursday and went to the track today. I also went back to full racing pads in the rear. I had been running stock pads in the rear to try and reduce the wiggle but they didn't work. The new calipers with the smaller pistons did the trick. There was still just a faint hint of wiggle on initial braking but it was very mild and hardly noticeable.

I ordered the calipers in red because they only had red and yellow in stock. I would prefer to have black to match the front calipers on the front of my TA but they don't make black. Now one problem is that the red calipers turned a brownish red. I had once had this problem on stock OEM red calipers on my 09 ACR and they were replaced under warranty. I don't know if anything can be done to prevent the calipers from changing color.

In any event anyone with the rear end wiggle should consider this kit. Maybe go with the Anoodized finish (kind of a gray color). Unfortunately they didn't have them in stock.

UPDATE: When I loaded the car on the trailer the rear calipers were reddish brown. They were still hot. Today I got the car off the trailer and the calipers, while dirty, appear to be red again.

[darbgnik]

Thanks for the review!

[Bruce H.]

Did you datalog your brake force and lap times to determine if the car braked as hard or lapped as fast?

The wiggle is puzzling, and even varies in intensity from day to day. Even Ben Keating is unsure whether the rear actually needs more or less bias to reduce it. And some track rats feel it isn't an issue and just learn to basically ignore it, confident that there's no loss of control, which is where I'm at with a fully stock TA.

[KB Viper]

awesome feedback, thanks for sharing. I recently ordered thier BBK, I can't wait to get a first track day and report back.

[donk_316]

Why doesn't my car do this wiggle under hard breaking? Or atleast I have never noticed it.

[darbgnik]

Why doesn't my car do this wiggle under hard breaking? Or atleast I have never noticed it.

Might need to brake harder from higher speeds? I only notice it braking very hard from very fast. Basically only turn 1 at our track.......

[LmeaViper]

I only ever noticed it while bedding my new pads on a paved rural road (~ 120 - 20 mpg max brake). I can't recall it ever happening on track when I had the stock P-Zeros on.

[ViperGeorge]

The track I was at I would hit 145 or so on the back straight before entering a reasonably hard braking zone. Car used to wiggle a lot there, now not so much.

[ViperGeorge]

Why doesn't my car do this wiggle under hard breaking? Or atleast I have never noticed it.

Hard to say why you don't have it. If you did, you would definitely notice it, really hard to miss it when it happens. All I can say is maybe you are not as hard on the brakes as we are. According to SRT engineers the wiggle is caused by interaction of the 4 channel ABS (new on the Gen 5) and the diff pump moving torque from side to side. The SRT hot shoes for sure know about it but they just say hang on and ride it out. It makes me very uncomfortable. In any event the engineers also have confirmed that "yes, less rear brake would help reduce or eliminate it." In fact, they had previously told me to run race pads in the front and OEM pads in the rear to reduce rear bias. That didn't work.

The new calipers seem to work way better and with race pads all around. The SRT engineer did say that the smaller pistons in the rear might increase stopping distance. I did not notice that but that maybe because I was less tentative on the brakes than I was with the wiggle. With the wiggle I would tend to brake earlier and not as hard in an attempt to lessen it.

The only thing that is a bit disappointing is the color change on the rear calipers. They went from red to reddish brown.

See update in my first post. Calipers appear to be red again after they cooled down.

[TrackAire]

Good to hear the wiggle issue is getting a little bit more under control. I wish SRT had solved this problem before the car left the assembly line...obviously there is a cure to the issue.

Regarding the discoloration of the rear caliper, that usually happens to the fronts since they get so much hotter. I'm sure RB will chime in, maybe the powder coating was not correct or a different type of powder can be used that is more impervious to the temps so the units don't turn brown. Hard to believe the rears are getting hotter than the fronts so I'm thinking it's got something to do with the actual coating not being able to handle the heat that is produced.

Best case scenario is a higher temp powder coating in black....all problems would then be solved.

[ViperGeorge]

See edits to previous posts concerning color changes. Calipers after cooling seem to be red again.

[ViperGeorge]

One additional item. If you buy the Rear Bias kit from Racing Brakes (which you should if you are concerned about the rear end wiggle), do not clean them with Brake Cleaner. I had a couple of dirty spots that didn't come off easily so I used a little brake cleaner on a rag and some red color came off on the rag so I stopped. Didn't seem to hurt anything but if I had rubbed harder or used more brake cleaner it may have been a problem. Ether (starting fluid) works and doesn't effect the color. It is not as strong as brake cleaner so it takes some elbow grease.

[Racingbrake]

Thanks for sharing your experience.

For caliper cleaning we recommended the following fluids but definitely not brake cleaner which is too strong and abrasive.

http://cimg2.ibsrv.net/gimg/www.mbworld.org-vbulletin/640x480/80-img_0541_2387e03e4d1061722ccad2091560f40c0b006184. jpg

Use D-Alcohol to clean your caliper for dirt, oil grease etc. (including rid of rubber from your rims), It works like magic and can make caliper surface clean and shining with little effort.

Use Goof Off if you have sticky stuff like glue or tar etc.

Both are available at HomeDepot or online retailers (<$10)

[Racingbrake]

...Hard to believe the rears are getting hotter than the fronts so I'm thinking it's got something to do with the actual coating not being able to handle the heat that is produced.

Best case scenario is a higher temp powder coating in black....all problems would then be solved.

I don't think the rear is hotter rather it's because the rear is in "RED" which more noticeable than the "BLACK" in the front.

All powder coating are more or less the same in temperature fading, and the best heat resistant to color fade is Hard-Anodizing which is available as an optional finish.

[MomentaryRacing]

We did not observe any significant color changes when we ran the kit - we used it for some practice sessions, 3 qualifying sessions and 3 races over the course of 3 days. Will check the color to be sure.

OEM rear calipers do change their color fairly quickly with track use, "browning" of the calipers was a fairly common occurrence on ACR-X cars that actually saw race use - because of the way the airflow travels underneath the car on Gen3-4-5 Vipers, there is a build-up of heat inside the rear wheels. We logged up to 800-900F sustained temperatures in there under hard race use, before we started to make aero modifications around rear wheels (currently, we are able to keep rear rotor temps under 700 degrees or so, with re-worked exhaust pod venting, cooling ducting, and upsized RB 2-piece rotors).

It is quite possible that any finish on rear brake parts would deteriorate with time, unless the car is modified to block hot air from getting "sucked" underneath the car, and cooler air is channeled toward the brakes.

As far as consistency of balance/rear ABS issues: A lot of that will be affected by the type of tire and pads used, as well as balance between front and rear downforce. If anyone has wheel speed, or even just plain GPS track data from various Gen5 configurations, let us know and we can take a look.
Obviously, it takes a fair amount of instrumentation to track downforce balance with precision, but a lot can be determined from longitudinal deceleration profiles during high speed braking, especially considering how unique Viper's front/rear bias is (in the stock form)

Very encouraging to hear that higher friction coefficient pads can be used with the kit - this was one of the reasons for developing it.

[MomentaryRacing]

Might need to brake harder from higher speeds? I only notice it braking very hard from very fast. Basically only turn 1 at our track.......

It may be a sign that the car can take more front downforce, more rake, less rear wing, softer front compression settings, or some combination of the above :)

[ViperGeorge]

To recap. I ran the rear kit with Raybestos 45s in the front and the very slightly less aggressive Raybestos 43s in the rear. While the red calipers appeared to be reddish brown when hot they did return to red when cool. As for the cleaner I won't use Brake Cleaner again. Ether seemed to work well but I will switch to alcohol.

None the less the big NEWS is that the kit does what it is supposed to do, it improves brake balance and virtually eliminates the rear end wiggle that the Gen 5s are prone to. While SRT engineers have said that smaller rear pistons will increase stopping distances, I did not notice that at all. In fact and because I was more confident in the brakes (since there was no real wiggle) I was able to brake later and harder. Bottom line, buy the kit if the rear end wiggle is bothering you, your lap times will go down, mine did.

[MomentaryRacing]

On our Gen4, we have braking points deeper 20-40ft in most corners with the kit, and about a second off lap times. Upgrading rear calipers may not sound like an obvious method to improve track performance, but when it fixes the balance of the car, it works better than adding more power.

Our detailed review is here: http://driveviper.com/forums/threads/14877-New-kit-under-development-improving-GenIII-IV-brake-balance-for-track-autocross-use?p=249690&viewfull=1#post249690

[Racingbrake]

...While SRT engineers have said that smaller rear pistons will increase stopping distances, I did not notice that at all. In fact and because I was more confident in the brakes (since there was no real wiggle) I was able to brake later and harder. Bottom line, buy the kit if the rear end wiggle is bothering you, your lap times will go down, mine did.

Your experience proven SRT engineers were incorrect, they only considered the direct result of "down sizing" the pistons (less pressure) but failed to realize the reduction of rear bias was actually shifted to the front, so with an overall (front & rear) better balanced brake system it allows you to apply more pedal pressure (brake harder) without the rear wiggling issue, so not only you can stop the car in shorter distance, but you can brake "late" to shave the lap time which was also witnessed by Momentary Racing.

[The_Ruski_Driver]

ViperGeorge, thanks for the review! The first few times I felt the wiggle I was very nervous and have gotten more used to it. I am not a track junkie like some on here but when/if it becomes a possibility for me I will definitely look into it. I can't believe the engineers allow such an unsafe bias to leave the assembly line.
Glad you're enjoying your car more than before!

- - - Updated - - -


Why doesn't my car do this wiggle under hard breaking? Or atleast I have never noticed it.

Stop driving like a b***h :p

[Racingbrake]

On our Gen4, we have braking points deeper 20-40ft in most corners with the kit, and about a second off lap times. Upgrading rear calipers may not sound like an obvious method to improve track performance, but when it fixes the balance of the car, it works better than adding more power.

Our detailed review is here: http://driveviper.com/forums/threads/14877-New-kit-under-development-improving-GenIII-IV-brake-balance-for-track-autocross-use?p=249690&viewfull=1#post249690

Very true and well said - "A balanced brake works better than adding more power".

However it seems more people are interested in adding "Turbo/HP", while intelligent track racers tend to look for an optimal brake system to inspire their confidence before benefiting from those extra horsepower.

A word about caliper color.

This rear caliper is the same as the CCB brake kit we built for Porsche 911, so they are powder coated with "Porsche" Yellow (pccb) and Red (standard iron brake). Black and Hard-Anodizing finish can be made available if more Viper owners are interested in this kit.

[ViperGeorge]

Very true and well said - "A balanced brake works better than adding more power".

However it seems more people are interested in adding "Turbo/HP", while intelligent track racers tend to look for an optimal brake system to inspire their confidence before benefiting from those extra horsepower.

A word about caliper color.

This rear caliper is the same as the CCB brake kit we built for Porsche 911, so they are powder coated with "Porsche" Yellow (pccb) and Red (standard iron brake). Black and Hard-Anodizing finish can be made available if more Viper owners are interested in this kit.

I got to admit that I was in the camp of add more power first. Now that I've changed the rear calipers I realize that the improved balance makes a bigger difference in lap times. I certainly am more comfortable in the car now.

[ViperGeorge]

Went to the track again today with my 15 TA 2.0. I have the Racing Brakes rear bias calipers installed and I have to say, amazing! No more rear end wiggle! It is gone. This is huge. Anyone that has experienced the rear end wiggle with stock steel brakes needs this upgrade. Even if you say "it doesn't really bother me." I call BS. The rear end wiggle effects your confidence in braking. Now I don't even have to think about the brakes. They are always there and they work great. Why SRT didn't set the car up this way to begin with is beyond me. HUGE improvement.

[Racingbrake]

George,

Thanks for sharing although your testimonial sounds too good to be true until someone actually tried it - This kit was created for Momentary Racing to maximize their race car's full potential and I hope more Viper owners can realize the benefit of its availability of this set up to effectively improve their lap.


awesome feedback, thanks for sharing. I recently ordered thier BBK, I can't wait to get a first track day and report back.

Just you know that the kit you purchased only the front new 6 pot calipers are supplied, the rear calipers remain as the original old 4 pot, so your bias will the same as before.

Your 6 pot kit:
http://www.racingbrake.com/Dodge-Viper-2016-ACR-E-Iron-6-Pot-Caliper-BBK-w-RB-p/dod-irp-02.htm

Rear balanced kit:
http://www.racingbrake.com/RB-Rear-Aluminum-Caliper-and-Iron-Rotors-for-Dodge-p/2546.htm

[MomentaryRacing]

Hey, super gratifying to see others benefitting from the R&D that happened last season. It may seem counter - intuitive to upgrade brakes to go faster, but it is no accident that a lot of pro's invest heavily into both car and driver development when it comes to brake (and braking) performance.

It is hard to say why Dodge/SRT decided to go with such an unusual front/rear bias configuration. It may be that it was driven by pricing/availability of brembo/stoptech parts. One thing that stock ratio is good for, is limiting front brake pad wear, and resulting dust in street/daily driving conditions, so maybe that was a factor as well :)

[sharmut]

@RB,

I have a 14 T/A and wanted to know if the rear kit below can be used with the factory TA brembo rotors without modifications?
http://www.racingbrake.com/ProductDetails.asp?ProductCode=2546

Which pads do you suggest for the rear if I wanted to retain the factory brembo pads on the front?
Assuming 6 months after purchasing the rear balanced kit, I wanted to replace the front factory 4-pot brembo with the RB 6-pot caliper, what would the front/rear bias be?

[Racingbrake]

The balanced bias rear RB caliper uses the same pad as GTS (with 53mm lining depth), you can also use TA pad (with 60mm depth). If you purchase the complete kit (including rotors), you can use both pads without the concern of brake pad overhang because RB rotors are made for track duty with 65mm wide annulus.

Please note that change of brake pad shape (size) will not affect the brake bias but will affect the braking temperature, e.g. A larger pad will make the braking temperature lower than a smaller pad.

Here is a re-cap of 4 set up with brake bias, as you can see if you install RB 6/4 brake system the bias is almost identical to the new Viper with CCB which has a reduced bias rear 4 pot calipers.

http://cimg8.ibsrv.net/gimg/www.mbworld.org-vbulletin/615x590/80-brake_bias_analysis_5aaf2bc0abbf7b0c3bb4dd192c41dd 3bde477c10.png

We offer a very flexible upgrade program, you can upgrade/replace the rear first and see how it goes, and then upgrade the front to 6 pot or do it all together at one time.

[Racingbrake]

Here are reference pictures of RB 6 piston caliper and rotor.

http://cimg0.ibsrv.net/gimg/www.mbworld.org-vbulletin/600x220/80-red_7c41d46977ab52840618e243d7301e72180ef973.png

http://cimg9.ibsrv.net/gimg/www.mbworld.org-vbulletin/600x480/80-red_caliper_rotor_d66f3d4714b94544580704a4449fc597 c86486e5.png

[Racingbrake]

Hi,

Wonder if any serious track racers here are interested in ordering this balanced kit, which someone commented "should" have been corrected since G3 or G4, but we did it.

This kit was proven working by Momentary Racing Team and your fellow Viper racers, so what are you waiting for?

[Racingbrake]

Some members asking about how the CCB 6 pot piston area compares to GTS's 4 pot front:

The CCB front 6 pot in fact is 50mm^2 vs. GTS 4 pot 55.5mm^2, so it's actually smaller than GTS's

Here the summary of piston size, area and bias analysis:
https://driveviper.com/forums/threads/15649-Racing-Brakes-Rear-Bias-Kit-Evaluation?p=261921&viewfull=1#post261921

[Dan Cragin]

On the 08-10 ACR models we tracked, new software for the ABS module in conjunction with a rear bias valve took care of the issue. On the 03-08 Competition coupes, a smaller rear brake rotor was used for World Challenge to correct this issue.

[Scott_in_fl]

On the 08-10 ACR models we tracked, new software for the ABS module in conjunction with a rear bias valve took care of the issue. On the 03-08 Competition coupes, a smaller rear brake rotor was used for World Challenge to correct this issue.

In the motorcycle roadracing world, 99.9999% of the braking comes from the front. However, when you get going really fast around a track, you learn that you can settle any nervousness in the chassis just before diving into a turn by lightly dragging the rear brake (it also helps tighten your line, and this is happening as you're also trail braking the front to max lean -- do not try this at home).

Anyway, the point I'm making is that the rear brake is like the hand of God pulling on the back of the bike so that it does not want to get ahead of the front. It's a finesse thing that I would love to be able to control in a car.

That said, there appear to be different views about whether the rear needs more or less bias. Dan seems to be saying less braking to the rear (with a smaller rotor). George seems to have found some success with more braking to the rear.

Has anyone yet tried both to see where the answer lies?

[dmann]

In the motorcycle roadracing world, 99.9999% of the braking comes from the front. However, when you get going really fast around a track, you learn that you can settle any nervousness in the chassis just before diving into a turn by lightly dragging the rear brake (it also helps tighten your line, and this is happening as you're also trail braking the front to max lean -- do not try this at home).
Anyway, the point I'm making is that the rear brake is like the hand of God pulling on the back of the bike so that it does not want to get ahead of the front. It's a finesse thing that I would love to be able to control in a car.
?

Kinda similar in the MX world. I could drop the front in a rut and smooth out chopped up braking bumps using a light modulation of brakes. I too hope that some day I'll be able to have the same kind of control out there in the car.

[serpent]

Here are reference pictures of RB 6 piston caliper and rotor.
http://cimg0.ibsrv.net/gimg/www.mbworld.org-vbulletin/600x220/80-red_7c41d46977ab52840618e243d7301e72180ef973.png

Warren, do you know how much the calipers weigh? Are they lighter than the stock 4 piston setup?

[Racingbrake]

Based on the fact that Dodge reduced the rear caliper bias on the new CCB 6/4 pot set up, it's evident the old 4/4 pot bias needs improvement.

When it comes to brake bias balance, there is nothing more effective than the output of hydraulic pressure - The most direct brake force applied to the brake pads, although some other components change such as rotor size, brake pad COF etc. followed by the auxiliary devices (proportional valve (https://en.wikipedia.org/wiki/Proportioning_valve), electronic control etc.) may also achieve similar result.

Our caliper library has a total of 172 units of fixed piston calipers; OEM (from Acura & Aston Martin to Porsche & Tesla) & aftermarket (All major brands), so our understanding covers a very wide range of applications, our analysis is objective and based on the numbers (no biased opinion).

We offer fundamental solution with caliper replacement for those who really need them; to improve brake bias, or prefer to have a more durable and stiffer calipers like GTR community.

[ViperGeorge]

Based on the fact that Dodge reduced the rear caliper bias on the new CCB 6/4 pot set up, it's evident the old 4/4 pot bias needs improvement.

When it comes to brake bias balance, there is nothing more effective than the output of hydraulic pressure - The most direct brake force applied to the brake pads, although some other components change such as rotor size, brake pad COF etc. followed by the auxiliary devices (proportional valve (https://en.wikipedia.org/wiki/Proportioning_valve), electronic control etc.) may also achieve similar result.

Our caliper library has a total of 172 units of fixed piston calipers; OEM (from Acura & Aston Martin to Porsche & Tesla) & aftermarket (All major brands), so our understanding covers a very wide range of applications, our analysis is objective and based on the numbers (no biased opinion).

We offer fundamental solution with caliper replacement for those who really need them; to improve brake bias, or prefer to have a more durable and stiffer calipers like GTR community.

I was one of the first to install your rear reduced bias calipers on my 2015 TA 2.0. They completely eliminated the rear end wiggle. Since then I upgraded to an ACR-E with steel TA brakes. I haven't noticed the wiggle on the ACR even though it has the TA's steel brakes. Is that due to the effects of aero? or did Dodge change the bias somehow on all ACRs regardless of brake type. By the way I use the same pads - Raybestos 45s in the front and 43s in the rear.

[Racingbrake]

ACR-E TA brake, as far as we know only changes the front rotor with increased annulus for taller pads, the calipers remain the same, so it shall not change the bias.

[Racingbrake]

Warren, do you know how much the calipers weigh? Are they lighter than the stock 4 piston setup?

https://cimg8.ibsrv.net/gimg/www.mbworld.org-vbulletin/640x480-1/oe_4_pot_8_3_lbs_c6d6b610ae4f25cef6c80ddb9a92f3e7d 643b480.jpg

https://cimg5.ibsrv.net/gimg/www.mbworld.org-vbulletin/640x480-1/rb_6_pot_8_6_lbs_f5a9884e236be00206d3935ba70d8f8b6 fac1d38.jpg

https://cimg7.ibsrv.net/gimg/www.mbworld.org-vbulletin/640x480-1/top_view_759755db3989d8047634c5b130fbc4c791ef0bcf. jpg

[Racingbrake]

Brake pad size comparison:

Left (RB 6 pot): 168 width x 65 depth (PD1666=Mustang GT500)

Right top (OE): 132 width x 52 depth (PD592)
Right bottom (OE/TA): 132 width x 60 depth (PD1001)

*Dimensions are in mm, width=steel backing plate; depth=lining (friction material)

https://cimg3.ibsrv.net/gimg/www.mbworld.org-vbulletin/604x326-1/brake_pad_comparison_20d3f68e568438db36c44cc4d8a3b b076fe36a46.png

[ViperGeorge]

ACR-E TA brake, as far as we know only changes the front rotor with increased annulus for taller pads, the calipers remain the same, so it shall not change the bias.

Rear rotors on the ACR-E TA brake package also have the wider annulus. Calipers do look the same as the TA but the car definitely brakes better. Virtually no wiggle from high speed braking. Maybe aero helps.

[Racingbrake]

From your experience it seems the TA rear calipers have been updated to the same as CCB rear with reduced bias.

[ViperGeorge]

By the way, apparently some folks were wondering if RB's rear bias calipers will work with the OEM e-Brake. Yes, they do. There are absolutely no modifications required to the e-Brake and it will continue to function as it did before. RB's calipers mount in place of the OEM calipers using a very solid "bracket" that is supplied with the kit.

Also I did just receive a set of the rear bias adjusting calipers for my ACR/TA. It has steel brakes and while initially I didn't think the wiggle was as bad as it was in the TA, there are times when it does wiggle quite a bit. I haven't installed them yet, been too busy, but I will get to it in a week or so. Want to get them installed before One Lap of America. When I can save up enough dough I think I will get RB to rebuild my front OEM calipers and go with their larger rotors.

[Racingbrake]

In case you are interested to learn, the new Corvette C8 has a similar rear biased brake set up although not as bad as GTS, here is a comparison of OE C8 vs. RB 6/4 pot BBK set up.