Here is an interesting question. How do we improve braking in a standard vehicle without redesigning the whole system?
Tires are always the first upgrade as they are what do the work for stopping, turning, and going. So that is priority 1, but what is #2?
Modern vehicles come with more and more advanced systems that use the brakes. From a supercar with an open diff that uses rear brakes as a limited slip, to turn-in assistance and anti-lock brakes, the modern vehicle braking system can and does A LOT!
How do we improve it without braking the bank (pun and spelling intended)?
Stuffing a Brembo carbon ceramic big brake kit will bring even the most aggressive car down from the Talladega speed record but I remember a Fox Body Mustang kit that achieved similar-to-the-time big brake kit performance with a pad, line, and fluid change.
So what say you GRM? Best bang for the buck, measurable, brake improvements?
Pads. (or shoes for drum brakes)
There's a lot one can do with the friction materials that will dramatically improve things.
Improve front/rear balance. An adjustable proportioning valve has made a big difference to a couple of cars I have run.
Weight. Every ounce you carry around with you is added stress on the brakes and less mass is better.
In reply to alfadriver :
Ok, which pads do you recommend? or is it time for a magazine comparison?
In reply to Streetwiseguy :
Would this interfere with the ABS?
In reply to KyAllroad :
Mr Chapman in the house!!! Lotus 7s for everyone!!!! JK.
All good suggestions. I'd add ventilation. Cars rarely need more braking force but often need more brake heat capacity. Ventilation helps here and also slows pad wear.
Gains from proportioning changes are unfortunately going the way of the dodo due to ABS. Manufacturers often half-ass the brake proportioning on modern cars and let the ABS take care of it.
Autocross or road race or ..?
if road racing then change your fluid! A higher boiling point fluid will help a lot.
Ok, so lets take your normal appliance.
Mazda CX-5 is a good appliance. Likely to be used by normal people. CX-5. 70-0 is 177 ft. What would you do to shorten it? The Mazda 3 is 171 ft at 300lbs lighter so weight can be accounted for 6 feet.
Remember this isn't JUST for HPDE/Autocross/track use but DD as well.
NOHOME
UltimaDork
10/11/17 9:26 a.m.
As with most engineered systems, if you are going to try and optimize, you need to be aware of what you want to achieve, and what you are going to compromise in the effort.
The first thing you need to do is set the baseline for what you want to improve. Is it shorter stopping or fade resistance? Create the test, measure and record results. You need to do this in the wet and the dry.
Be aware that you are going to give up something with every change that you make. If you mess with front/rear, you might compromise wet weather results. Good idea to know what you are compromising so it does not take you by surprise.
Trying to answer this same question, I tried full race pads on the MGB about 25 years ago. Sailed right past the first stop-sign that I came to in the hood. Who knew you had to pre-warm the damn things? And the banshee squeal was insane. Ate rotors also. The good is that once warmed up they bit into the rotor like a Pitbull. They were stupid. Had to live with them for a while cause out of $$$.
Current pads are great for pretty much everything. Great at stopping the car in all conditions and great at coating the wheel in brake dust. No point in even cleaning the front wheels.
Over the years, I have come full circle and come to the conclusion that it is hard to beat the OEM engineers at their own game. If possible, when Hot-rodding, I adopt a system as it was designed to work and try not too mess with it.
FlightService said:
In reply to alfadriver :
Ok, which pads do you recommend? or is it time for a magazine comparison?
That, I don't know. It's been a few years since I've raced, but I know that compounds can make a huge difference. One can even mix and match compounds to balance the brakes for autocrossing when you are not allowed to do that (there are many classes where you can change pad compounds but not other hardware).
For me, on an Alfa, given that there were few choices, I had Porterfield pads that I liked a lot. But the last time I bought anything was a decade ago.
Hopefully, someone will be able to chime in for your specific application.
Which pads depends on what you're doing. I have EBC Yellowstuff pads and for a lightweight low-powered car, I find that they're good for mixed street and track use. They handle all the heat you can throw at them on track and still work well when cold, and they're not too noisy (just a little squeaking on the first stop from stone cold, and a grinding/milling noise under heavy braking). Plenty of dust production though, and they're kind of hard to control because they bite so sharply. They're a favorite in the handbrake calipers of pro drift cars for that reason.
In reply to NOHOME :
As a former Tier 1 Engineer, I have found that Cost is king, everything else is secondary. So I do agree with what you say, I just realize what the OEM engineers were focused on which isn't what I am focused on.
I could have narrowed down the qualifications, initial bite, fade resistance, brake dust, noise, but I didn't want to sway or focus the answers any more than I already have by reminding it is not just about track/competition work but DD as well. Sometimes you come to solutions from answers that weren't directed to that question specifically. So socially driven forum question as opposed to a specific answer to a specific personal issue.
NOHOME said:
The first thing you need to do is set the baseline for what you want to improve. Is it shorter stopping or fade resistance? Create the test, measure and record results. You need to do this in the wet and the dry.
Exactly. There are two major components to braking: single stop distance and fade resistance. You approach them differently.
Single stop is all about the amount of traction available at the wheels, and the ability of the brakes to take full advantage of that. Proportioning is a big factor here. On a modern car like a CX5 with electronic brake distribution and good ABS, you're pretty much already in an ideal situation there so all you can do is either increase the amount of traction (better tires) or simply give the brakes less work to do by making the car lighter. Lowering the car should help as it decreases the amount of weight transfer and thus increases the total amount of traction available.
Multiple stops is about heat management. Keeping the pads in their working temperature and not overheating any component. This means good (and fresh) fluid, the correct pads and cooling airflow. This is also where big brake kits come in, they have more thermal mass.
SEADave
HalfDork
10/11/17 10:32 a.m.
As others said, start with pads and fluid. Here there is some benefit in just replacing the old with new, and if the new pads or fluid is an upgrade all the better. Then maybe brake hoses and rotors, which again might make more of a difference by the fact that you are replacing old with new more than any noticeable benefit from something like fancy braided hoses or slotted rotors.
Finally, and this varies from vehicle to vehicle, see if there is some sort of OEM upgrade available. If there was a performance model (or newer model, station wagon, police car etc.) on the same chassis with better brakes, maybe you can simply swap them out. Pretty much any car with an internet following probably has a forum that would tell you what the hot setup is. One time I was googling Lexus LS brakes to do some work on mine, and happened on a forum where folks were using them as an upgrade on some older Porsche. Who knew?
Yep, Keith and everyone else covered it.
Bugatti used active areo to help slow the car from high speeds.
Those crazy racing trucks in Europe spray water on the brakes to help cool them.
Those fancy Magnetorheological dampers should be able to provide a anti-dive system that would help with weight transfer without causing lock-up when hitting bumps.
Dive is a visible result of weight transfer, not a cause. You can change the speed of weight transfer by messing with shocks, but not the overall amount.
I've used active aero to help with braking. The biggest advantage was the stability it offered.
ABS and prop valves are mutually exclusive, but for a fwd track car, I won't hit the track without pulling the fuse. I forgot one day, and coming into a slow left hander from a long straight, the left rear lifted, the abs panicked and shut all the brakes off, and I died in a flaming crash. Well, not quite, but I yanked all the abs stuff and added adjustable prop valves to the rear.
ABS and prop valves are not mutually exclusive. On a less clever system, you can disconnect the ABS and use a prop valve to get the fundamental bias right, then turn the ABS back on. That will minimize ABS engagement. On a clever system, the ABS does real-time proportioning for you so the valve is essentially integrated.
ABS lets every wheel brake as hard as it can. Running without ABS means that no wheel can brake any harder than the one with the least traction. If you're running a crude system from a couple of decades ago, there are certainly failure modes.
In reply to Keith Tanner :
Agreed. In theory, ABS can be very useful. But a lot of older systems just don't work that well. And some are tuned to allow very little slip before engagement. Great for rock hard all seasons that lock up with very little slip first, but not so great for sticky rubber or snow tires that develop max braking force at a significantly higher slip level (the poorly tuned ABS will never let you get there).
That tuning flaw is what led to me killing the ABS in the Jeep. In snow (with snow tires), it would stop significantly faster without ABS than with it. The ABS was cutting in and reducing braking well before the tires were slipping enough to get max braking (and correspondingly, the ABS was cutting in way before we were close to lockup). So without ABS, you could lean on the pedal harder and push the tires closer to their limits.
Thus my comment about crude systems from a couple of decades ago. Modern ABS is excellent technology, but it didn't burst on to the scene fully refined.
Deep snow has always been a case where locking the wheels is preferable, as it lets you build up a wedge under the tires. But tossing out the whole system because occasionally you think you can do better is...well, if I wanted to start a bunfight I'd make some allusion to vaccination. But this is a car forum, so a comparison with autonomous cars is more appropriate.
I can tell you from setting up the V8 ND that the braking distances go all to hell when the ABS fails and your brake bias goes all out of whack. That's a good modern system and running very sticky tires.
In reply to Keith Tanner :
In your experience, would you say it's better to achieve the proper fundamental bias through hydraulic proportioning or by juggling pad compounds? Since those are probably the easiest ways to change the bias.
My 2001 Forester seems to have a fairly rear biased system from the factory, running the same pads front and rear. The ABS system is also total garbage for ice, snow, dirt, gravel, and even mildly slippery pavement.
My dad's 2000 Silverado seems to run ONLY the rear brakes up to a certain input force. We usually drive it pretty gingerly and have had to replace the rear pads twice and rear rotors once with 190k miles. However the front rotors and pads literally look new.
I like to do it hydraulically, as pad compounds tend to be temperature sensitive and I don't want to have my bias change with temperature. Besides, hydraulic proportioning can have a curve (ish) shape whereas friction ratios are fixed - other than the aforementioned temperature changes.
Start with getting the basics right, piston sizes and rotor diameter. Then fine-tune with a valve. Then let the electronic system do the on-the-fly changes.
Type Q
SuperDork
10/11/17 10:43 p.m.
AngryCorvair said:
Yep, Keith and everyone else covered it.
Are you still doing brake system design as a day job?
