Bigger rotors and Braking Distance?

[thescreensavers]

Got a question

From what I understand bigger rotors = better braking performance. Forget they can displace more heat or have more surface area.


But lets say you take a Car that's 2 tons with braking system, 2 Piston setup that can easily lock up the wheels and get ABS to go on.

Then you take the same car same tires and everything except you add bigger rotors, bigger pads to accompany the rotors and the same 2 piston setup, would there be a difference in stopping distance? Based on just 1 full stop(no fade..ect)


From 70-0? Highway speeds..ect

 

[Greenman]

I wouldn't think so. There is a finite limit on how much braking a given tire with a given amount of weight will take before it locks.

 

[Bartman39]

From what I understand bigger rotors = better braking performance

What this means is the larger brakes handle the more severe duty better over a longer period of time and heavier weights... Traction is the main factor in stopping distance so if you have over powered brakes with poor traction then the stopping distance might even increase...? Anti lock brakes helps make up for this but is not perfect either although it will help maintain control more than anything... Larger brakes will "feel" better but its up to the driver to handle and control stopping distances...

 

[Vette73]

Tires stop a car; rotors/brakes stop the tires.

So if the rotors heat up/fade enough in heavy braking then yea it might help. But easier to get good tires.

 

[exdeath]

Tires stop the car.

Brakes dissipate heat.

You do get more brake torque with larger diameter rotors, but if this exceeds the capacity of the tires, it will do more harm than good. The biggest benefit to larger brakes is larger surface area for cooling, larger mass for heat capacity, more pistons and larger pads to spread out the pressure/stress and heat per surface area, keep the brake fluid from boiling, pads from glazing, etc.

Brakes simply turn kinetic energy into heat, that's all they do. Brakes are a heat sink. Tires stop the car.

For my car, just doing a 60 to 0 hard stop, the difference in brake rotor surface temps between a 13" rotor and 14" rotor is over 100 deg. That's like 800 vs 900 F, huge when it comes to brakes and their ability to *repeatedly* stop a 3600 lb vehicle.

 

[exdeath]

But lets say you take a Car that's 2 tons with braking system, 2 Piston setup that can easily lock up the wheels and get ABS to go on.

Then you take the same car same tires and everything except you add bigger rotors, bigger pads to accompany the rotors and the same 2 piston setup, would there be a difference in stopping distance? Based on just 1 full stop(no fade..ect)

No change in stopping distance. The factory brakes already overpower the stock tires and trigger ABS.

Where you will run into a difference is with repeated stops, and life expectancy of the rotors/pads/brake fluid.

 

[mwmorph]

Tires stop the car.

Brakes dissipate heat.

You do get more brake torque with larger diameter rotors, but if this exceeds the capacity of the tires, it will do more harm than good. The biggest benefit to larger brakes is larger surface area for cooling, larger mass for heat capacity, more pistons and larger pads to spread out the pressure/stress and heat per surface area, keep the brake fluid from boiling, pads from glazing, etc.

Brakes simply turn kinetic energy into heat, that's all they do. Brakes are a heat sink. Tires stop the car.

For my car, just doing a 60 to 0 hard stop, the difference in brake rotor surface temps between a 13" rotor and 14" rotor is over 100 deg. That's like 800 vs 900 F, huge when it comes to brakes and their ability to *repeatedly* stop a 3600 lb vehicle.

Very accurate, except I think you forgot ot mention extreme high speed driving Larger brakes, larger pad surface area and higher piston pressure can help at extreme speeds to shorten braking distances.

Replacing just about any stock brakes with no tire change will not change 60-0mph stopping distances much. Where it will help is as you mentioned, repeated hard stopping and high speed. I would expect much shorter distances from say 80-0 or 120-0 from big brake kits versus most stock brakes.

 

[MJinZ]

No change in stopping distance. The factory brakes already overpower the stock tires and trigger ABS.

Where you will run into a difference is with repeated stops, and life expectancy of the rotors/pads/brake fluid.

I think with performance cars, this true.

I think with more more standard cars, the brakes don't necessarily outclass the tires, so an upgrade will likely help braking distance, even if it isn't a huge difference.

 

[HarryLui]

Car with bigger rotor might take longer distance to stop.

Bigger rotor = heavier = more rotational force to stop.


I remember Top Gear took a minivan, added bigger rotors, calipers, pads, and bigger wheels/tires, the lap time took longer than the car stock's time.

 

[Pulsar]

I think with performance cars, this true.

I think with more more standard cars, the brakes don't necessarily outclass the tires, so an upgrade will likely help braking distance, even if it isn't a huge difference.

You "think"?

If you can lock up all four tires with factory brakes- and I'm unaware of a car that can't - then the limiting factor of deceleration is the friction provided by your tires.

Increasing your rotor size, pad size, or the clamping cylinders / hydraulic pressure will do nothing. You've already got enough torque from your brakes to stop your tires from spinning.

Unless of course you can come up with a brand of car that can't lock it's brakes up. Perhaps there's one out there.

 

[jlee]

I think with performance cars, this true.

I think with more more standard cars, the brakes don't necessarily outclass the tires, so an upgrade will likely help braking distance, even if it isn't a huge difference.

If you can't get ABS to engage on a modern car with factory tires on dry pavement, something is wrong with your braking system. Barring extreme situations (repeated hard stops, racing, etc), any modern car should out-brake its tires.

 

[Apex]

Got a question

From what I understand bigger rotors = better braking performance. Forget they can displace more heat or have more surface area.


But lets say you take a Car that's 2 tons with braking system, 2 Piston setup that can easily lock up the wheels and get ABS to go on.

Then you take the same car same tires and everything except you add bigger rotors, bigger pads to accompany the rotors and the same 2 piston setup, would there be a difference in stopping distance? Based on just 1 full stop(no fade..ect)


From 70-0? Highway speeds..ect

In general, yes, you will stop in a shorter distance with larger rotors and bigger pads. The difference, however, will be relatively small.

The difference comes in how quickly a system can reach the clamping pressure necessary to lock the wheels/tires. Larger pads and bigger rotors will allow you to reach the pressure necessary to lock the wheels more quickly.

Let's say (just for instance), you can lock the tires 1/20th of a second faster with the bigger brake setup.

At 70 mph, you're traveling 103 feet per second. A miniscule 1/20th of a second difference is a difference of just over 5 feet.

Lots of variables may change that, of course. However, if we're talking about apples to apples, a bigger brake system will SLIGHTLY shorten your stopping distance, even when discussing a single stop.

Again, this only holds with a straight apples to apples comparison. If you want to change other variables, the results may be wildly different.

 

[thescreensavers]

^ oh really I did not know that.

Thanks for all the replies guys. I for what ever reason forgot to think into how much grip the tires can give lol

 

[MJinZ]

You "think"?

If you can lock up all four tires with factory brakes- and I'm unaware of a car that can't - then the limiting factor of deceleration is the friction provided by your tires.

Increasing your rotor size, pad size, or the clamping cylinders / hydraulic pressure will do nothing. You've already got enough torque from your brakes to stop your tires from spinning.

Unless of course you can come up with a brand of car that can't lock it's brakes up. Perhaps there's one out there.

Yes, I'm thinking any compact Civic/Corolla type won't be able to.

 

[MJinZ]

In general, yes, you will stop in a shorter distance with larger rotors and bigger pads. The difference, however, will be relatively small.

The difference comes in how quickly a system can reach the clamping pressure necessary to lock the wheels/tires. Larger pads and bigger rotors will allow you to reach the pressure necessary to lock the wheels more quickly.

Let's say (just for instance), you can lock the tires 1/20th of a second faster with the bigger brake setup.

At 70 mph, you're traveling 103 feet per second. A miniscule 1/20th of a second difference is a difference of just over 5 feet.

Lots of variables may change that, of course. However, if we're talking about apples to apples, a bigger brake system will SLIGHTLY shorten your stopping distance, even when discussing a single stop.

Again, this only holds with a straight apples to apples comparison. If you want to change other variables, the results may be wildly different.

I thought about this as well, because the smaller surface area of clamping on small brakes will not be able to generate the same amount of stopping force in the same amount of time as a larger version. Of course, at some point, both will likely reach the saturation point where the ABS is necessary fairly quickly, but not at the same rate and thus not in the same amount of time.

One system will kick ABS on earlier - this is the faster braking system.

That difference in rate should make a few feet of decreased stopping distance.

 

[Bartman39]

I thought about this as well, because the smaller surface area of clamping on small brakes will not be able to generate the same amount of stopping force in the same amount of time as a larger version. Of course, at some point, both will likely reach the saturation point where the ABS is necessary fairly quickly, but not at the same rate and thus not in the same amount of time.

One system will kick ABS on earlier - this is the faster braking system.

That difference in rate should make a few feet of decreased stopping distance.

Would very little if any and still is dependant on the tire traction which is what directly affects the ABS doing its job... Also everything is thrown out the door with various weather conditions because traction A tires are supposed to be better than traction B but does not mean under all condtions...

 

[Demo24]

Yes, I'm thinking any compact Civic/Corolla type won't be able to.

lol, wut. The cars aren't that heavy (weighing around 3k pounds) and pretty much all can brake from 60 in under 130ft, usually around 120ft. That's fairly respectable, especially given the skinny tires put on the cars. Sorry, but any vehicle capable of such numbers will be able to overpower the tires and trip ABS.

 

[JulesMaximus]

I think with performance cars, this true.

I think with more more standard cars, the brakes don't necessarily outclass the tires, so an upgrade will likely help braking distance, even if it isn't a huge difference.

Not true at all. Any car would be able to lock up the brakes without ABS.

Bigger rotors/brakes will just improve heat dissipation with repeated stops which helps reduce fade. This is very important in stops from high speed or under race conditions where you are constantly using the brakes.

 

[MJinZ]

Not true at all. Any car would be able to lock up the brakes without ABS.

Bigger rotors/brakes will just improve heat dissipation with repeated stops which helps reduce fade. This is very important in stops from high speed or under race conditions where you are constantly using the brakes.

Perhaps we should test this, some cars are still equipped with drum brakes in the rear. I would wonder about say a Corolla's ability to brake from 60mph to 0 with ABS.

 

[Demo24]

Perhaps we should test this, some cars are still equipped with drum brakes in the rear. I would wonder about say a Corolla's ability to brake from 60mph to 0 with ABS.

Drums or not it hardly matters. Go yank the parking brake, even at speed it will lock the rear tires. The parking brake on a lot of vehicles is simply a drum brake.

 

[MJinZ]

Drums or not it hardly matters. Go yank the parking brake, even at speed it will lock the rear tires. The parking brake on a lot of vehicles is simply a drum brake.

Hmmm people can drive my car just fine with the parking brakes on... as have many people who have attempted to move my car without realizing the parking brakes (left foot) are engaged.

 

[Bartman39]

Hmmm people can drive my car just fine with the parking brakes on... as have many people who have attempted to move my car without realizing the parking brakes (left foot) are engaged.

Perhaps your rear brakes are not working properly but understand its a parking brake not as it used to be termed (emergency brake) so not all parking brakes will lock the wheels down...

Also we have a 2005 Corolla S that when it had the Wallyworld Goodyear Viva II`s it would not stop or handle worth a crap... Went back to what I put on after the OEM tires which were Yokohama TRZ`s and it handles and dry/wet traction is awesome as compared to either the OEM`s or the Viva II`s... Will say its parking brake will lock the rear wheels from a stop or while moving and of course they are drum rear...

 

[Bignate603]

Hmmm people can drive my car just fine with the parking brakes on... as have many people who have attempted to move my car without realizing the parking brakes (left foot) are engaged.

The amount of braking force you get from the parking brake locked on and the amount you get when you're yanking on it can be far different. Try driving around while you're pulling on the lever pretty hard and see if its any different.

 

[JulesMaximus]

Hmmm people can drive my car just fine with the parking brakes on... as have many people who have attempted to move my car without realizing the parking brakes (left foot) are engaged.

Sounds like you need to have your parking brake adjusted.

 

[Howard]

not another fucking mjizzum thread

You "think"?

If you can lock up all four tires with factory brakes- and I'm unaware of a car that can't - then the limiting factor of deceleration is the friction provided by your tires.

Increasing your rotor size, pad size, or the clamping cylinders / hydraulic pressure will do nothing. You've already got enough torque from your brakes to stop your tires from spinning.

Unless of course you can come up with a brand of car that can't lock it's brakes up. Perhaps there's one out there.

The tires are the limiting factor until brake fade happens. Bigger brakes attenuate its effect by way of higher thermal mass and faster cooling.




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