Brake thoughts

[petawawarace]

We run the stock single piston steel calipers with Hawk DTC 60 pads on the front of our car. We like the feel and modulation, but a set of front pads are only lasting 1 weekend and cost $350/pair.  Rears are single piston and hp+ pads. They will last 2 or more weekends. I have the option to bolt on some 4 piston brembo calipers that literally bolt right on (they came factory on a similar model).  Here are the dimensions of the pads:

 

Stock surface area is 4.8in2 and 0.740" thick   11.5" rotor

Brembo surface area is 10.2in2 and 0.590" thick   12.5" rotor

 

Obviously the Brembos should help stopping performance, but we were not really lacking in that area.  

Any thoughts on if the Brembo pads will last significantly longer?

[Chris Huggins]

Brake life is a complicated dance.

 

Heat management is what I would address first.  Cooling for wheel Bearings, Rotor, Axle (if fwd), will help everything.

Pad compound is the second path I would address.  DTC60 are not known for being endurance pads.  Hawk is coming out with an endurance compound but I have not received my test pads yet so I don't know what it will perform like.  Not sure what other compounds are available for your pad shape, but I can look it up and give you a recommendation if you tell me the fitment.  

 

Surface area increase will help pad life, but at the same time you are reducing the thickness.  Hard to say conclusively if the change will be a net positive.

 

Not sure what you mean by "help stopping performance".  I'm afraid you might be confused by the myth that bigger brakes mean shorter stopping distances, which is unfortunately quite prevalent but not true at all.  If your current brakes have enough strength to lock your tires (or engage ABS), then going to bigger ones won't shorten your stopping distances.  Things that improve stopping distances:  Tires. Tires. Tires. ABS improvements.  Tires. Brake Bias improvements.  Tires. Alignment.  Tires. Suspension setup

 

[mender]

To the point where the heat generated overwhelms the brakes' capability to dissipate that heat in a timely fashion and keep the overall temperatures within the operating range of the weakest component.

 

Pad volume is a consideration but as Chris said, there is a trade-off when talking about surface temp. Wear vs temperature is usually expressed as a log function so keeping temps down usually has a significant effect on life. Rotor temp may be your limiting factor, and you may find that covering more of the rotor surface with bigger pads may not be the direction that you need to go.

 

Also as Chris said, maximize your cooling and that will help everything. If you're already there, consider other pad choices. I went from Hawk Blues to ST-43s and cut my pad costs to about a third but gave up some sensitivity/modulation.  

Edited September 1, 2021 by mender

[petawawarace]

Thanks guys,

 

We currently have really good brakes.  We do have a small issue with the rear getting light on really heavy braking and engaging the ABS.  I'm sure that we could get a little bit better braking with some changes, but the advantages are small.  Heat management is pretty well looked after.  

 

But, perhaps a different pad would be the cheapest/easiest solution. I would be willing to give up some feel, if I can cut those costs in half.

 

Any suggestions for endurance pads on a fwd car?

 

 

[Hugh Jass]

I don't know if they work well on fwd cars but I have always had good luck with Raybestos ST-43 in rwd cars and from the sounds of it would be cheaper and last longer than what you are using now.  I'd call Porterfield Brakes and see what they think too, they will know what other people are buying.

[Black Magic]

1 hour ago, petawawarace said:

Any suggestions for endurance pads on a fwd car?

 

I assume much of your issue is late in the braking zone. Stop trail braking. It is hard to break drivers from this, but it an inherit weakness of FWD cars. You have to brake sooner\roll more speed into the corner (if you car will scrub more speed naturally you roll more speed, heavier cars you brake sooner)

 

You can remove more rear brake bias, but this will most likely hurt your straight-line raw braking potential. I am assuming in a straight line you have good brake bias but feel rear lock during combined braking events. 

 

Most FWD cars run a little more front brake bias, which does increase the brake work on the front axle. Upsize those brakes and run good pads. The rears you can often leave stock, using the up size front brakes to get a little more front bias. 

 

I have run ST43, lasted forever and was good to the last drop...however the feel and release are tough for many drivers to tame. Carbotech has some pads a step down in durability that are much easier to driver, if you brake temps allow. When you make front running power you will want about 12 lbs of front rotor mass per 2,000 lbs of race weight, some people lean towards 14. A 2000 lbs FWD car will have about 11" brakes, assuming a setup with moderate brake temps, wear and heat. 

 

For FWD cars bigger brakes allow more cooling, heat storage and most importantly help keep the temp out of those precious wheel bearings and CVs. They have a hard enough life as it is. 

[petawawarace]

1 hour ago, Black Magic said:

 

I assume much of your issue is late in the braking zone. Stop trail braking. It is hard to break drivers from this, but it an inherit weakness of FWD cars. You have to brake sooner\roll more speed into the corner (if you car will scrub more speed naturally you roll more speed, heavier cars you brake sooner)

 

You can remove more rear brake bias, but this will most likely hurt your straight-line raw braking potential. I am assuming in a straight line you have good brake bias but feel rear lock during combined braking events. 

 

Most FWD cars run a little more front brake bias, which does increase the brake work on the front axle. Upsize those brakes and run good pads. The rears you can often leave stock, using the up size front brakes to get a little more front bias. 

 

I have run ST43, lasted forever and was good to the last drop...however the feel and release are tough for many drivers to tame. Carbotech has some pads a step down in durability that are much easier to driver, if you brake temps allow. When you make front running power you will want about 12 lbs of front rotor mass per 2,000 lbs of race weight, some people lean towards 14. A 2000 lbs FWD car will have about 11" brakes, assuming a setup with moderate brake temps, wear and heat. 

 

For FWD cars bigger brakes allow more cooling, heat storage and most importantly help keep the temp out of those precious wheel bearings and CVs. They have a hard enough life as it is. 

The abs issue is under hard straight-line braking.  I actually dont trail brake much as we've got this car to rotate well through the corner.  I believe our the abs issue is more that of weight transfer and not a great abs control system.  I have adjustable dampers on the front, and increasing the compression dampning helped keep the rear wheels in contact. But I still can get it under very hard braking. Our braking is actually pretty good and I'm happy with it. Its the wear that I would like to improve. The pads are relatively small. 

 

I don't know the weight of the rotors off hand, but we have 11.5" rotors and are 2500lbs.   

[Black Magic]

The brake wear will be highly non linear with temp. Sizing the brakes to get reasonable temps can be huge. I have run St43 pads that lasted 14 hours, and another that lasted 3 race weekends. Both on the same type of car, one of them is an 10 lb rotor the other is nearly 16. The heavier rotor was an inch bigger and also much more flow area in the vanes. 

 

Sounds like a reasonable rotor diameter change (weight cooling and size) would help. I would suggests making a reasonable change, 20% or more increase in braking at the same pressure. We can build you a calculator to determine this, simple answer being up size the rotor effective (center of pad) diameter 20%, make the pistons 20% more area, or some combo of those. I would also up the rotor mass to something nearing 16 lbs + if you want to really open up the pad options you can run and keep the rest of the parts happy.  

[petawawarace]

Stock rotors are 11.5” and 16.4lbs

Brembo versions are 12.5” and 17.6lbs

 

The brembo calipers weigh 6lbs while the factory steel ones and brackets weigh 12pbs.  
 

Im thinking that I would do a floating rotor setup with an aluminum hat which would shave off a few more pounds without sacrificing the heat mass all that much.  

[Black Magic]

45 minutes ago, petawawarace said:

Im thinking that I would do a floating rotor setup with an aluminum hat which would shave off a few more pounds without sacrificing the heat mass all that much.  

 

Not a bad idea, but the easy money would be running the oe brembo package and moving on to another development project for the car. Sounds like a win win, better brakes at a net weigh reduction. 

 

Most of your rotor mass is in the section that would still be iron with 2 piece rotors. 

 

 

[Grant]

I usually find opposed-piston calipers to get longer pad life than sliders. Some sliders have upgraded (brass) bushings available which should help.

 

Don't forget to look at rotor thickness and directionality as well as diameter. You'll also need to measure piston diameters and piston radial distance to calculate brake bias change. Brake bias can have a big effect on pad life too.

 

Lastly, if you use ABS a lot you'll find your tires wear out quicker but your brakes last longer. Brake bias also becomes less of a concern if you're on ABS. If you threshold brake up to ABS, you absolutely need good brake bias.

Like Chris I've never seen Hawk DTC-anything last very long. ST43s last forever but are difficult to modulate.

Our 11# directional Wilwood rotors seem to be out-lasting our old 18# non-directional RX8 rotors.

Edited September 1, 2021 by Grant

[petawawarace]

Picked up some old parts to test fit.  They bolt right up. Only thing I’d need to add is a 1/16” shim behind the rotor to space it out center of the caliper.  Or I could mill that off the ears on the caliper.  
 

The stock rotors are just over 1” thick. If I wanted to go to floating rotors (cheaper ones) I’d almost need to go to 1.21”or 0.81”

thick. Not sure if I would have pad space for that or not.  
 

Brand new Brembo calipers are only $190usd too.  

[MR2 Biohazard]

What is the pad size and area of your current pads vs the brembo pads. I went with the wilwood setup because the pad volume was like 3x the stock. This has me using the pads for around 3 races now instead of one. The cost for the wilwoods has paid for itself in 2-3 races with how costly pads are. Long term the Wilwood setup saves me a lot of money.

 

Pads also wear faster as the wear out as they can only absorb so much heat and will overheat faster.

 

Personally I hate the feel of ST43, but some like them. I currently like G-LOC R18 that have good feel, modulation and last a long time.

 

Also, based on the weight savings, if the pad area and volume is more it seems like the right setup. Since you have a FWD setup, said you might have a bit to much rear bias, the larger front setup might have the correct bias, but you should calculate it.

[turbogrill]

2 hours ago, MR2 Biohazard said:

Personally I hate the feel of ST43, but some like them. I currently like G-LOC R18 that have good feel, modulation and last a long time.

 

 

I have the ST43 on my NC, 0% feel. The brake is more of a binary switch

 

I always thought that was the ABS module playing tricks.

[Robmink]

I run a FWD VW and use Wilwood calipers with Wilwood BP-30 pads.  I used to go through a set of (fill-in-the-blank) in 7-10 hours, now I can run 2-3 weekends on one set.  I love the feel and none of my drivers complain (about the brakes anyway).  I use the stock rears with something like Hawk blues.  Change them once a season or two or three or just because I think I probably should.

[EngEtan]

On 9/2/2021 at 8:57 PM, petawawarace said:

The stock rotors are just over 1” thick. If I wanted to go to floating rotors (cheaper ones) I’d almost need to go to 1.21”or 0.81”

thick. Not sure if I would have pad space for that or not.  
 

 

Don't confuse two piece rotors with floating rotors. Floating rotors are much more expensive since they also include the bobbins or similar connecting methods. In most cases, two piece rotors are just fine.

[petawawarace]

1 hour ago, EngEtan said:

 

Don't confuse two piece rotors with floating rotors. Floating rotors are much more expensive since they also include the bobbins or similar connecting methods. In most cases, two piece rotors are just fine.

I do know what floating rotors are. 

[BMW_CEMETERY]

2 hours ago, EngEtan said:

 

Don't confuse two piece rotors with floating rotors. Floating rotors are much more expensive since they also include the bobbins or similar connecting methods. In most cases, two piece rotors are just fine.

You mean in most cases 1 piece rotors are fine??

 

How many chumps are running two piece/floating setups? 

[Rodger Coan-Burningham]

Just consider there is a reason(s) the Raybestos ST43 is probably the most widely used pad in this series.

[EngEtan]

15 hours ago, BMW_CEMETERY said:

You mean in most cases 1 piece rotors are fine??

 

Yes, same with one piece. Only advantages going with two piece rotors are the small weight savings of the aluminum hats, ring replacement costs are reduced slightly (but not cheaper than the bargain parts store one piece), and you can be had in different diameters and widths which usually equates to a better performing rotor but results may differ. I use the Wilwood two piece rotors with their 4 piston calipers. They've got lots of heat capacity. I thought about going with a full floating rotor, but the cost didn't make sense.

[petawawarace]

10 minutes ago, EngEtan said:

Yes, same with one piece. Only advantages going with two piece rotors are the small weight savings of the aluminum hats, ring replacement costs are reduced slightly (but not cheaper than the bargain parts store one piece), and you can be had in different diameters and widths which usually equates to a better performing rotor but results may differ. I use the Wilwood two piece rotors with their 4 piston calipers. They've got lots of heat capacity. I thought about going with a full floating rotor, but the cost didn't make sense.

The cost of the hats/bobbins would be a 1 time cost.  I own a machine shop, so I’ll make my own hats (plus no one makes them). So it’s just the rotors and bobbins I will buy.  

[EngEtan]

10 minutes ago, petawawarace said:

The cost of the hats/bobbins would be a 1 time cost.  I own a machine shop, so I’ll make my own hats (plus no one makes them). So it’s just the rotors and bobbins I will buy.  

Where are you buying the bobbins from? I've looked around a bit in the past and all I could fine were replacement kits for motorcycles and a couple part numbers at AP Racing and Alcon websites. Definitely wish I had my own machine shop to make that happen!

[MR2 Biohazard]

What is the need to go full floating rotor with Bobbins? Is there a real benefit to go floating vs just making a hat that rotor bolts to? I have made the hats myself and not have any issues, plus it is not expensive at all to make your own hats. I found the cost of the twp piece is even when you use the second rotor and can save money on the third and beyond.

[petawawarace]

So doing some more parts research and I think I’m going to put the bigger Brembo brakes on the front.  I’d like to go with a floating rotor.  I can make the hats so no cost there. I’m having a hard time finding rotor rings that will work with these calipers.  The factory rotors are 12.4” dia and 1” thick.  I can get lots of different affordable rings in 0.81” or 1.25” but none in 1”.  The 1.25” ones are too thick. I could maybe get 1.15” but that’d be tight. 
Thoughts on the 0.81”?  I’m a bit worried I would over extend the pistons, so I was thinking I could make some Ti spacers for the pistons that would prevent them

from over travelling.  

[MR2 Biohazard]

1 hour ago, petawawarace said:

So doing some more parts research and I think I’m going to put the bigger Brembo brakes on the front.  I’d like to go with a floating rotor.  I can make the hats so no cost there. I’m having a hard time finding rotor rings that will work with these calipers.  The factory rotors are 12.4” dia and 1” thick.  I can get lots of different affordable rings in 0.81” or 1.25” but none in 1”.  The 1.25” ones are too thick. I could maybe get 1.15” but that’d be tight. 
Thoughts on the 0.81”?  I’m a bit worried I would over extend the pistons, so I was thinking I could make some Ti spacers for the pistons that would prevent them

from over travelling.  

You can get pads made as thick as you want. You would just need to replace them before the get to thin. Gloc can make them whatever you want. You could also get them made with thicker backing plates so when you do metal on metal your pistons do not come out all the way.