Re: Brake design question - Ray? Anyone?

"Ray O" <rokigawa@tristarassociatesDOTcom> wrote in message news:...[color=blue]
>
> "Mark" <bogusmailmark@yahoo.com> wrote in message
> news:1148992047.221682.326620@j73g2000cwa.googlegroups.com...[color=green]
>> With a 4-wheel disc brake configuration, is the braking force (and
>> wear) distributed more evenly front-to-back than the use of discs in
>> the front and drum brakes in the rear? It may be my imagination, but I
>> think the rotors used on my Scion (all disc brakes) are smaller in the
>> front than those of my Matrix (disc/drum combination), even though the
>> weight of the cars is comparable, and I was wondering if the rear
>> brakes are intended to take more of the load.
>>[/color]
>
> The distribution of braking force from front to rear is more dependent on
> the weight distribution of the vehicle itself, suspension, vehicle speed,
> and design of the master cylinder than whether the rear brakes are disc or
> drum.
>
> Brakes stop vehicles by changing kinetic energy to heat energy, and the
> faster the heat is dissipated, the more efficiently it can change more
> kinetic energy to heat energy. Since disc brakes are exposed to more air
> than drum brakes, they can get rid of the heat more efficiently.
>
> Factors that affect brake rotor or drum diameter are wheel diameter,
> unsprung weight, vehicle weight, rotor and friction material composition,
> and standard designs from rotor manufacturers.
>
> I suspect that the rotors on the Scion may appear smaller because the
> wheel has a larger diameter and so there is more space between the outside
> of the rotor and the inside of the wheel rim.
> --
>
> Ray O
> (correct punctuation to reply)[/color]

Oops, forgot to mention swept area as one of the biggest factors in rotor
design. It is possible for a smaller diameter rotor to have a larger swept
area than a larger diameter rotor.
--

Ray O
(correct punctuation to reply)

On Tue, 30 May 2006 11:36:22 -0500, Ray O wrote:
[color=blue]
>
> "Ray O" <rokigawa@tristarassociatesDOTcom> wrote in message news:...[color=green]
>>
>> "Mark" <bogusmailmark@yahoo.com> wrote in message
>> news:1148992047.221682.326620@j73g2000cwa.googlegroups.com...[color=darkred]
>>> With a 4-wheel disc brake configuration, is the braking force (and
>>> wear) distributed more evenly front-to-back than the use of discs in
>>> the front and drum brakes in the rear? It may be my imagination, but I
>>> think the rotors used on my Scion (all disc brakes) are smaller in the
>>> front than those of my Matrix (disc/drum combination), even though the
>>> weight of the cars is comparable, and I was wondering if the rear
>>> brakes are intended to take more of the load.
>>>[/color]
>>
>> The distribution of braking force from front to rear is more dependent on
>> the weight distribution of the vehicle itself, suspension, vehicle speed,
>> and design of the master cylinder than whether the rear brakes are disc or
>> drum.
>>
>> Brakes stop vehicles by changing kinetic energy to heat energy, and the
>> faster the heat is dissipated, the more efficiently it can change more
>> kinetic energy to heat energy. Since disc brakes are exposed to more air
>> than drum brakes, they can get rid of the heat more efficiently.
>>
>> Factors that affect brake rotor or drum diameter are wheel diameter,
>> unsprung weight, vehicle weight, rotor and friction material composition,
>> and standard designs from rotor manufacturers.
>>
>> I suspect that the rotors on the Scion may appear smaller because the
>> wheel has a larger diameter and so there is more space between the outside
>> of the rotor and the inside of the wheel rim.
>> --
>>
>> Ray O
>> (correct punctuation to reply)[/color]
>
> Oops, forgot to mention swept area as one of the biggest factors in rotor
> design. It is possible for a smaller diameter rotor to have a larger swept
> area than a larger diameter rotor.[/color]

Dang! What would be the size of the pads?!?!

"Hachiroku" <Trueno@ae86.GTS> wrote in message
news:xF6fg.56$Cw3.40@trndny01...[color=blue]
> On Tue, 30 May 2006 11:36:22 -0500, Ray O wrote:
>[color=green]
>>
>> "Ray O" <rokigawa@tristarassociatesDOTcom> wrote in message news:...[color=darkred]
>>>
>>> "Mark" <bogusmailmark@yahoo.com> wrote in message
>>> news:1148992047.221682.326620@j73g2000cwa.googlegroups.com...
>>>> With a 4-wheel disc brake configuration, is the braking force (and
>>>> wear) distributed more evenly front-to-back than the use of discs in
>>>> the front and drum brakes in the rear? It may be my imagination, but I
>>>> think the rotors used on my Scion (all disc brakes) are smaller in the
>>>> front than those of my Matrix (disc/drum combination), even though the
>>>> weight of the cars is comparable, and I was wondering if the rear
>>>> brakes are intended to take more of the load.
>>>>
>>>
>>> The distribution of braking force from front to rear is more dependent
>>> on
>>> the weight distribution of the vehicle itself, suspension, vehicle
>>> speed,
>>> and design of the master cylinder than whether the rear brakes are disc
>>> or
>>> drum.
>>>
>>> Brakes stop vehicles by changing kinetic energy to heat energy, and the
>>> faster the heat is dissipated, the more efficiently it can change more
>>> kinetic energy to heat energy. Since disc brakes are exposed to more
>>> air
>>> than drum brakes, they can get rid of the heat more efficiently.
>>>
>>> Factors that affect brake rotor or drum diameter are wheel diameter,
>>> unsprung weight, vehicle weight, rotor and friction material
>>> composition,
>>> and standard designs from rotor manufacturers.
>>>
>>> I suspect that the rotors on the Scion may appear smaller because the
>>> wheel has a larger diameter and so there is more space between the
>>> outside
>>> of the rotor and the inside of the wheel rim.
>>> --
>>>
>>> Ray O
>>> (correct punctuation to reply)[/color]
>>
>> Oops, forgot to mention swept area as one of the biggest factors in rotor
>> design. It is possible for a smaller diameter rotor to have a larger
>> swept
>> area than a larger diameter rotor.[/color]
>
> Dang! What would be the size of the pads?!?![/color]

If you picture a brake rotor as a top hat, with the brim being the swept
area and the rotor's hub being the crown of the hat, a smaller hub would
allow a larger brim, which would in turn allow larger pads.

If you want to see small rear brake pads, take a look at the rear pads on a
Honda. The first time I did the rear brakes on my neighbor's Accord, I
thought she bought Honda motorcycle pads when I opened the box.
--

Ray O
(correct punctuation to reply)[color=blue]
>[/color]

On Tue, 30 May 2006 11:36:22 -0500, "Ray O"
<rokigawa@tristarassociatesDOTcom> wrote:
[color=blue]
>
>Oops, forgot to mention swept area as one of the biggest factors in rotor
>design. It is possible for a smaller diameter rotor to have a larger swept
>area than a larger diameter rotor.[/color]

Given that the pad area is the same, the bigger rotor has a leverage
advantage over the smaller rotor. It's the same principle as having a
longer handle on a wrench. The larger rotor also has the advantage of
dissipating the heat over a longer area of the rotor. As you have
mentioned, the more heat it dissipates, the more kinetic energy it can
convert to heat.

On Tue, 30 May 2006 22:20:30 -0500, "Ray O"
<rokigawa@tristarassociatesDOTcom> wrote:
[color=blue]
>
>"Hachiroku" <Trueno@ae86.GTS> wrote in message
>news:xF6fg.56$Cw3.40@trndny01...[color=green]
>> On Tue, 30 May 2006 11:36:22 -0500, Ray O wrote:
>>[color=darkred]
>>>
>>> "Ray O" <rokigawa@tristarassociatesDOTcom> wrote in message news:...
>>>>
>>>> "Mark" <bogusmailmark@yahoo.com> wrote in message
>>>> news:1148992047.221682.326620@j73g2000cwa.googlegroups.com...
>>>>> With a 4-wheel disc brake configuration, is the braking force (and
>>>>> wear) distributed more evenly front-to-back than the use of discs in
>>>>> the front and drum brakes in the rear? It may be my imagination, but I
>>>>> think the rotors used on my Scion (all disc brakes) are smaller in the
>>>>> front than those of my Matrix (disc/drum combination), even though the
>>>>> weight of the cars is comparable, and I was wondering if the rear
>>>>> brakes are intended to take more of the load.
>>>>>
>>>>
>>>> The distribution of braking force from front to rear is more dependent
>>>> on
>>>> the weight distribution of the vehicle itself, suspension, vehicle
>>>> speed,
>>>> and design of the master cylinder than whether the rear brakes are disc
>>>> or
>>>> drum.
>>>>
>>>> Brakes stop vehicles by changing kinetic energy to heat energy, and the
>>>> faster the heat is dissipated, the more efficiently it can change more
>>>> kinetic energy to heat energy. Since disc brakes are exposed to more
>>>> air
>>>> than drum brakes, they can get rid of the heat more efficiently.
>>>>
>>>> Factors that affect brake rotor or drum diameter are wheel diameter,
>>>> unsprung weight, vehicle weight, rotor and friction material
>>>> composition,
>>>> and standard designs from rotor manufacturers.
>>>>
>>>> I suspect that the rotors on the Scion may appear smaller because the
>>>> wheel has a larger diameter and so there is more space between the
>>>> outside
>>>> of the rotor and the inside of the wheel rim.
>>>> --
>>>>
>>>> Ray O
>>>> (correct punctuation to reply)
>>>
>>> Oops, forgot to mention swept area as one of the biggest factors in rotor
>>> design. It is possible for a smaller diameter rotor to have a larger
>>> swept
>>> area than a larger diameter rotor.[/color]
>>
>> Dang! What would be the size of the pads?!?![/color]
>
>If you picture a brake rotor as a top hat, with the brim being the swept
>area and the rotor's hub being the crown of the hat, a smaller hub would
>allow a larger brim, which would in turn allow larger pads.
>
>If you want to see small rear brake pads, take a look at the rear pads on a
>Honda. The first time I did the rear brakes on my neighbor's Accord, I
>thought she bought Honda motorcycle pads when I opened the box.[/color]

Funny you say that. Honda motorcycles use Nissin brand brakes. Their
cars do too. Hmmm...

By the way, I would also like to add that the caliper is a big factor
in breaking strength. The opposite force of the piston pushing
against the pad is the force pushing the caliper away from the rotor.
The less the caliper flexes, the more efficient the braking force.

"Ray O" <rokigawa@tristarassociatesDOTcom> wrote in message
news:3be98$447d0c59$180fead6$15347@msgid.meganewsservers.com...[color=blue]
>
> "Hachiroku" <Trueno@ae86.GTS> wrote in message
> news:xF6fg.56$Cw3.40@trndny01...[color=green]
>> On Tue, 30 May 2006 11:36:22 -0500, Ray O wrote:
>>[color=darkred]
>>>
>>> "Ray O" <rokigawa@tristarassociatesDOTcom> wrote in message news:...
>>>>
>>>> "Mark" <bogusmailmark@yahoo.com> wrote in message
>>>> news:1148992047.221682.326620@j73g2000cwa.googlegroups.com...
>>>>> With a 4-wheel disc brake configuration, is the braking force (and
>>>>> wear) distributed more evenly front-to-back than the use of discs in
>>>>> the front and drum brakes in the rear? It may be my imagination, but
>>>>> I
>>>>> think the rotors used on my Scion (all disc brakes) are smaller in the
>>>>> front than those of my Matrix (disc/drum combination), even though the
>>>>> weight of the cars is comparable, and I was wondering if the rear
>>>>> brakes are intended to take more of the load.
>>>>>
>>>>
>>>> The distribution of braking force from front to rear is more dependent
>>>> on
>>>> the weight distribution of the vehicle itself, suspension, vehicle
>>>> speed,
>>>> and design of the master cylinder than whether the rear brakes are disc
>>>> or
>>>> drum.
>>>>
>>>> Brakes stop vehicles by changing kinetic energy to heat energy, and the
>>>> faster the heat is dissipated, the more efficiently it can change more
>>>> kinetic energy to heat energy. Since disc brakes are exposed to more
>>>> air
>>>> than drum brakes, they can get rid of the heat more efficiently.
>>>>
>>>> Factors that affect brake rotor or drum diameter are wheel diameter,
>>>> unsprung weight, vehicle weight, rotor and friction material
>>>> composition,
>>>> and standard designs from rotor manufacturers.
>>>>
>>>> I suspect that the rotors on the Scion may appear smaller because the
>>>> wheel has a larger diameter and so there is more space between the
>>>> outside
>>>> of the rotor and the inside of the wheel rim.
>>>> --
>>>>
>>>> Ray O
>>>> (correct punctuation to reply)
>>>
>>> Oops, forgot to mention swept area as one of the biggest factors in
>>> rotor
>>> design. It is possible for a smaller diameter rotor to have a larger
>>> swept
>>> area than a larger diameter rotor.[/color]
>>
>> Dang! What would be the size of the pads?!?![/color]
>
> If you picture a brake rotor as a top hat, with the brim being the swept
> area and the rotor's hub being the crown of the hat, a smaller hub would
> allow a larger brim, which would in turn allow larger pads.
>
> If you want to see small rear brake pads, take a look at the rear pads on
> a Honda. The first time I did the rear brakes on my neighbor's Accord, I
> thought she bought Honda motorcycle pads when I opened the box.
> --
>
> Ray O
> (correct punctuation to reply)[/color]
I can't remember what car I was working on, it may have been the Supra, and
I was STUNNED at how small the rear pads were!

"Hachiroku" <Trueno@ae86.GTS> wrote in message
news:qUhfg.211$Jm5.116@trndny08...[color=blue]
>
> "Ray O" <rokigawa@tristarassociatesDOTcom> wrote in message
> news:3be98$447d0c59$180fead6$15347@msgid.meganewsservers.com...[color=green]
>>[/color][/color]
<snipped>>[color=blue][color=green]
>> If you want to see small rear brake pads, take a look at the rear pads on
>> a Honda. The first time I did the rear brakes on my neighbor's Accord, I
>> thought she bought Honda motorcycle pads when I opened the box.
>> --
>>
>> Ray O
>> (correct punctuation to reply)[/color]
> I can't remember what car I was working on, it may have been the Supra,
> and I was STUNNED at how small the rear pads were!
>[/color]

IIRC, the Supra's rear pads are not that small. The Tercel's rear pads are
pretty small but not as small as on a Honda.
--

Ray O
(correct punctuation to reply)