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Re: Setting Toe
Dave and Trudy wrote:
> "TeGGeR®" <tegger@tegger.c0m> wrote in message > news:Xns97EADC0BC8473tegger@207.14.116.130... > >>"R Flowers" <rflowers@Tinbowlinggreen.com> wrote in >>news:FK6dnVW-malmfwfZnZ2dnUVZ_ridnZ2d@insightbb.com: >>Ever driven un-powered 4-wheel drums? GAWD they were awful. Terrible! Plan >>your stops in advance, preferably in writing. >> >> >> >> >>>Then the front 2 discs came out, >> >> >> >>And it was akin to a religious conversion: YES LAWD, AH SEE THE LIGHT!!! >>Discs were a sea-change compared to drums. >> >> >> >> >>>and I guess people >>>thought "Well, if 2 are good, let's do all 4!" I remember sports cars >>>in the 70s and 80s touting their 4 wheel discs. >> >> >>Yep. But there is a point of diminishing returns, and rear discs was it. >>For road-going, legal speed, grocery-getting FWD cars, of course. >> >> >>-- >>TeGGeR® >> >>The Unofficial Honda/Acura FAQ >>www.tegger.com/hondafaq/ > > Just one question...If disks are so much better, why do the large trucks and > tour buses still use drums on all axles? I know there are some exceptions > but most use drums. I hadn't really considered this until your above > comments... > > Dave D > > very few of the modern tour buses use drums these days, or at least, not on the front. the main reason drums are still used on large trucks, especially big rigs, is because of the air brake thing. unlike cars and lighter vehicles, they're "fail safe" which means their "natural" position is full on as opposed to off like a car. strong springs inside the drums press the shoes real hard against the drum, and the air system actuates against the springs to hold the shoes off the drum so the vehicle can roll. if the braking system fails, the brakes come on, and the 30+ ton cargo comes to a halt. hopefully. "fail safe" is much more complicated to implement on disk brakes, but real simple inside a drum. plus imo, a lot of domestic truck manufacturers are not exactly innovative pioneers in the engineering department - the quality of the chrome plating seems to get more attention from what i can see. |
Re: Setting Toe
"TeGGeR®" <tegger@tegger.c0m> wrote in message
news:Xns97EADC0BC8473tegger@207.14.116.130... > > Ever driven un-powered 4-wheel drums? GAWD they were awful. Terrible! Plan > your stops in advance, preferably in writing. > I drove a '67 Chevy Biscayne (like a low end Impala) with unpowered 4-wheel drums down a long shallow descent in California when I was a new driver. Within a couple miles I had both feet braced on the brake pedal and was hoping for a place I could coast to a stop. The tranny was a 2-speed "Powerglide" (more glide than power) so low gear was just keeping my speed below 50 mph. I wanted my mommy! Mike |
Re: Setting Toe
"TeGGeR®" <tegger@tegger.c0m> wrote in message
news:Xns97EADC0BC8473tegger@207.14.116.130... > > Ever driven un-powered 4-wheel drums? GAWD they were awful. Terrible! Plan > your stops in advance, preferably in writing. > I drove a '67 Chevy Biscayne (like a low end Impala) with unpowered 4-wheel drums down a long shallow descent in California when I was a new driver. Within a couple miles I had both feet braced on the brake pedal and was hoping for a place I could coast to a stop. The tranny was a 2-speed "Powerglide" (more glide than power) so low gear was just keeping my speed below 50 mph. I wanted my mommy! Mike |
Re: Setting Toe
"TeGGeR®" <tegger@tegger.c0m> wrote in message
news:Xns97EADC0BC8473tegger@207.14.116.130... > > Ever driven un-powered 4-wheel drums? GAWD they were awful. Terrible! Plan > your stops in advance, preferably in writing. > I drove a '67 Chevy Biscayne (like a low end Impala) with unpowered 4-wheel drums down a long shallow descent in California when I was a new driver. Within a couple miles I had both feet braced on the brake pedal and was hoping for a place I could coast to a stop. The tranny was a 2-speed "Powerglide" (more glide than power) so low gear was just keeping my speed below 50 mph. I wanted my mommy! Mike |
Re: Setting Toe
"Michael Pardee" <michaeltnull@cybertrails.com> wrote in
news:vaidnXilwfUY5AHZnZ2dnUVZ_oidnZ2d@sedona.net: > "TeGGeR®" <tegger@tegger.c0m> wrote in message > news:Xns97EADC0BC8473tegger@207.14.116.130... >> >> Ever driven un-powered 4-wheel drums? GAWD they were awful. Terrible! >> Plan your stops in advance, preferably in writing. >> > > I drove a '67 Chevy Biscayne (like a low end Impala) with unpowered > 4-wheel drums down a long shallow descent in California when I was a > new driver. Within a couple miles I had both feet braced on the brake > pedal and was hoping for a place I could coast to a stop. The tranny > was a 2-speed "Powerglide" (more glide than power) so low gear was > just keeping my speed below 50 mph. I wanted my mommy! The worst car I ever personally drove was a 1974 Nova with manual drums all around. Now, a '74 Nova is not nearly a '38 Ford when it comes to brakes, but it was still quite a culture shock when you're used to a vacuum- assisted 1975 Japanese disc/drum setup. So remind me again, how come the Japs got such a foothold over here in the first place?... -- TeGGeR® The Unofficial Honda/Acura FAQ www.tegger.com/hondafaq/ |
Re: Setting Toe
"Michael Pardee" <michaeltnull@cybertrails.com> wrote in
news:vaidnXilwfUY5AHZnZ2dnUVZ_oidnZ2d@sedona.net: > "TeGGeR®" <tegger@tegger.c0m> wrote in message > news:Xns97EADC0BC8473tegger@207.14.116.130... >> >> Ever driven un-powered 4-wheel drums? GAWD they were awful. Terrible! >> Plan your stops in advance, preferably in writing. >> > > I drove a '67 Chevy Biscayne (like a low end Impala) with unpowered > 4-wheel drums down a long shallow descent in California when I was a > new driver. Within a couple miles I had both feet braced on the brake > pedal and was hoping for a place I could coast to a stop. The tranny > was a 2-speed "Powerglide" (more glide than power) so low gear was > just keeping my speed below 50 mph. I wanted my mommy! The worst car I ever personally drove was a 1974 Nova with manual drums all around. Now, a '74 Nova is not nearly a '38 Ford when it comes to brakes, but it was still quite a culture shock when you're used to a vacuum- assisted 1975 Japanese disc/drum setup. So remind me again, how come the Japs got such a foothold over here in the first place?... -- TeGGeR® The Unofficial Honda/Acura FAQ www.tegger.com/hondafaq/ |
Re: Setting Toe
"Michael Pardee" <michaeltnull@cybertrails.com> wrote in
news:vaidnXilwfUY5AHZnZ2dnUVZ_oidnZ2d@sedona.net: > "TeGGeR®" <tegger@tegger.c0m> wrote in message > news:Xns97EADC0BC8473tegger@207.14.116.130... >> >> Ever driven un-powered 4-wheel drums? GAWD they were awful. Terrible! >> Plan your stops in advance, preferably in writing. >> > > I drove a '67 Chevy Biscayne (like a low end Impala) with unpowered > 4-wheel drums down a long shallow descent in California when I was a > new driver. Within a couple miles I had both feet braced on the brake > pedal and was hoping for a place I could coast to a stop. The tranny > was a 2-speed "Powerglide" (more glide than power) so low gear was > just keeping my speed below 50 mph. I wanted my mommy! The worst car I ever personally drove was a 1974 Nova with manual drums all around. Now, a '74 Nova is not nearly a '38 Ford when it comes to brakes, but it was still quite a culture shock when you're used to a vacuum- assisted 1975 Japanese disc/drum setup. So remind me again, how come the Japs got such a foothold over here in the first place?... -- TeGGeR® The Unofficial Honda/Acura FAQ www.tegger.com/hondafaq/ |
Re: Setting Toe
"jim beam" <nospam@example.net> wrote in message news:KtKdnT4xV5_ccQbZnZ2dnUVZ_rOdnZ2d@speakeasy.ne t... > Dave and Trudy wrote: >> "TeGGeR®" <tegger@tegger.c0m> wrote in message >> news:Xns97EADC0BC8473tegger@207.14.116.130... >> >>>"R Flowers" <rflowers@Tinbowlinggreen.com> wrote in >>>news:FK6dnVW-malmfwfZnZ2dnUVZ_ridnZ2d@insightbb.com: >>>Ever driven un-powered 4-wheel drums? GAWD they were awful. Terrible! >>>Plan >>>your stops in advance, preferably in writing. >>> >>> >>> >>> >>>>Then the front 2 discs came out, >>> >>> >>> >>>And it was akin to a religious conversion: YES LAWD, AH SEE THE LIGHT!!! >>>Discs were a sea-change compared to drums. >>> >>> >>> >>> >>>>and I guess people >>>>thought "Well, if 2 are good, let's do all 4!" I remember sports cars >>>>in the 70s and 80s touting their 4 wheel discs. >>> >>> >>>Yep. But there is a point of diminishing returns, and rear discs was it. >>>For road-going, legal speed, grocery-getting FWD cars, of course. >>> >>> >>>-- >>>TeGGeR® >>> >>>The Unofficial Honda/Acura FAQ >>>www.tegger.com/hondafaq/ >> >> Just one question...If disks are so much better, why do the large trucks >> and tour buses still use drums on all axles? I know there are some >> exceptions but most use drums. I hadn't really considered this until your >> above comments... >> >> Dave D > very few of the modern tour buses use drums these days, or at least, not > on the front. Hate to disagree with you but every MCI coach I have driven in the past 10 years, including new ones, all had drums on all axles. I checked with our shop chief and he says it has to do with the larger swept area of the drum/shoe brakes as opposed to the disk/pad brakes. It is true that the disks will not heat up as quickly and are less susceptible to fade and water but the increased stopping power is the reason he gave me. > > the main reason drums are still used on large trucks, especially big rigs, > is because of the air brake thing. unlike cars and lighter vehicles, > they're "fail safe" which means their "natural" position is full on as > opposed to off like a car. strong springs inside the drums press the > shoes real hard against the drum, and the air system actuates against the > springs to hold the shoes off the drum so the vehicle can roll. if the > braking system fails, the brakes come on, and the 30+ ton cargo comes to a > halt. hopefully. "fail safe" is much more complicated to implement on > disk brakes, but real simple inside a drum. plus imo, a lot of domestic > truck manufacturers are not exactly innovative pioneers in the engineering > department - the quality of the chrome plating seems to get more attention > from what i can see. Actually, there are two systems at work there. The service brakes are activated via an "S" cam and release when the pedal is no longer depressed. You are quite correct, however, that in the event of catastrophic air pressure loss, the failsafe system that you describe will lock up (full on) all the brakes. Rather an unsettling experience I might add. Dave D |
Re: Setting Toe
"jim beam" <nospam@example.net> wrote in message news:KtKdnT4xV5_ccQbZnZ2dnUVZ_rOdnZ2d@speakeasy.ne t... > Dave and Trudy wrote: >> "TeGGeR®" <tegger@tegger.c0m> wrote in message >> news:Xns97EADC0BC8473tegger@207.14.116.130... >> >>>"R Flowers" <rflowers@Tinbowlinggreen.com> wrote in >>>news:FK6dnVW-malmfwfZnZ2dnUVZ_ridnZ2d@insightbb.com: >>>Ever driven un-powered 4-wheel drums? GAWD they were awful. Terrible! >>>Plan >>>your stops in advance, preferably in writing. >>> >>> >>> >>> >>>>Then the front 2 discs came out, >>> >>> >>> >>>And it was akin to a religious conversion: YES LAWD, AH SEE THE LIGHT!!! >>>Discs were a sea-change compared to drums. >>> >>> >>> >>> >>>>and I guess people >>>>thought "Well, if 2 are good, let's do all 4!" I remember sports cars >>>>in the 70s and 80s touting their 4 wheel discs. >>> >>> >>>Yep. But there is a point of diminishing returns, and rear discs was it. >>>For road-going, legal speed, grocery-getting FWD cars, of course. >>> >>> >>>-- >>>TeGGeR® >>> >>>The Unofficial Honda/Acura FAQ >>>www.tegger.com/hondafaq/ >> >> Just one question...If disks are so much better, why do the large trucks >> and tour buses still use drums on all axles? I know there are some >> exceptions but most use drums. I hadn't really considered this until your >> above comments... >> >> Dave D > very few of the modern tour buses use drums these days, or at least, not > on the front. Hate to disagree with you but every MCI coach I have driven in the past 10 years, including new ones, all had drums on all axles. I checked with our shop chief and he says it has to do with the larger swept area of the drum/shoe brakes as opposed to the disk/pad brakes. It is true that the disks will not heat up as quickly and are less susceptible to fade and water but the increased stopping power is the reason he gave me. > > the main reason drums are still used on large trucks, especially big rigs, > is because of the air brake thing. unlike cars and lighter vehicles, > they're "fail safe" which means their "natural" position is full on as > opposed to off like a car. strong springs inside the drums press the > shoes real hard against the drum, and the air system actuates against the > springs to hold the shoes off the drum so the vehicle can roll. if the > braking system fails, the brakes come on, and the 30+ ton cargo comes to a > halt. hopefully. "fail safe" is much more complicated to implement on > disk brakes, but real simple inside a drum. plus imo, a lot of domestic > truck manufacturers are not exactly innovative pioneers in the engineering > department - the quality of the chrome plating seems to get more attention > from what i can see. Actually, there are two systems at work there. The service brakes are activated via an "S" cam and release when the pedal is no longer depressed. You are quite correct, however, that in the event of catastrophic air pressure loss, the failsafe system that you describe will lock up (full on) all the brakes. Rather an unsettling experience I might add. Dave D |
Re: Setting Toe
"jim beam" <nospam@example.net> wrote in message news:KtKdnT4xV5_ccQbZnZ2dnUVZ_rOdnZ2d@speakeasy.ne t... > Dave and Trudy wrote: >> "TeGGeR®" <tegger@tegger.c0m> wrote in message >> news:Xns97EADC0BC8473tegger@207.14.116.130... >> >>>"R Flowers" <rflowers@Tinbowlinggreen.com> wrote in >>>news:FK6dnVW-malmfwfZnZ2dnUVZ_ridnZ2d@insightbb.com: >>>Ever driven un-powered 4-wheel drums? GAWD they were awful. Terrible! >>>Plan >>>your stops in advance, preferably in writing. >>> >>> >>> >>> >>>>Then the front 2 discs came out, >>> >>> >>> >>>And it was akin to a religious conversion: YES LAWD, AH SEE THE LIGHT!!! >>>Discs were a sea-change compared to drums. >>> >>> >>> >>> >>>>and I guess people >>>>thought "Well, if 2 are good, let's do all 4!" I remember sports cars >>>>in the 70s and 80s touting their 4 wheel discs. >>> >>> >>>Yep. But there is a point of diminishing returns, and rear discs was it. >>>For road-going, legal speed, grocery-getting FWD cars, of course. >>> >>> >>>-- >>>TeGGeR® >>> >>>The Unofficial Honda/Acura FAQ >>>www.tegger.com/hondafaq/ >> >> Just one question...If disks are so much better, why do the large trucks >> and tour buses still use drums on all axles? I know there are some >> exceptions but most use drums. I hadn't really considered this until your >> above comments... >> >> Dave D > very few of the modern tour buses use drums these days, or at least, not > on the front. Hate to disagree with you but every MCI coach I have driven in the past 10 years, including new ones, all had drums on all axles. I checked with our shop chief and he says it has to do with the larger swept area of the drum/shoe brakes as opposed to the disk/pad brakes. It is true that the disks will not heat up as quickly and are less susceptible to fade and water but the increased stopping power is the reason he gave me. > > the main reason drums are still used on large trucks, especially big rigs, > is because of the air brake thing. unlike cars and lighter vehicles, > they're "fail safe" which means their "natural" position is full on as > opposed to off like a car. strong springs inside the drums press the > shoes real hard against the drum, and the air system actuates against the > springs to hold the shoes off the drum so the vehicle can roll. if the > braking system fails, the brakes come on, and the 30+ ton cargo comes to a > halt. hopefully. "fail safe" is much more complicated to implement on > disk brakes, but real simple inside a drum. plus imo, a lot of domestic > truck manufacturers are not exactly innovative pioneers in the engineering > department - the quality of the chrome plating seems to get more attention > from what i can see. Actually, there are two systems at work there. The service brakes are activated via an "S" cam and release when the pedal is no longer depressed. You are quite correct, however, that in the event of catastrophic air pressure loss, the failsafe system that you describe will lock up (full on) all the brakes. Rather an unsettling experience I might add. Dave D |
Re: Setting Toe
Dave and Trudy wrote:
> "jim beam" <nospam@example.net> wrote in message > news:KtKdnT4xV5_ccQbZnZ2dnUVZ_rOdnZ2d@speakeasy.ne t... > >>Dave and Trudy wrote: >> >>>"TeGGeR®" <tegger@tegger.c0m> wrote in message >>>news:Xns97EADC0BC8473tegger@207.14.116.130... >>> >>> >>>>"R Flowers" <rflowers@Tinbowlinggreen.com> wrote in >>>>news:FK6dnVW-malmfwfZnZ2dnUVZ_ridnZ2d@insightbb.com: >>>>Ever driven un-powered 4-wheel drums? GAWD they were awful. Terrible! >>>>Plan >>>>your stops in advance, preferably in writing. >>>> >>>> >>>> >>>> >>>> >>>>>Then the front 2 discs came out, >>>> >>>> >>>> >>>>And it was akin to a religious conversion: YES LAWD, AH SEE THE LIGHT!!! >>>>Discs were a sea-change compared to drums. >>>> >>>> >>>> >>>> >>>> >>>>>and I guess people >>>>>thought "Well, if 2 are good, let's do all 4!" I remember sports cars >>>>>in the 70s and 80s touting their 4 wheel discs. >>>> >>>> >>>>Yep. But there is a point of diminishing returns, and rear discs was it. >>>>For road-going, legal speed, grocery-getting FWD cars, of course. >>>> >>>> >>>>-- >>>>TeGGeR® >>>> >>>>The Unofficial Honda/Acura FAQ >>>>www.tegger.com/hondafaq/ >>> >>>Just one question...If disks are so much better, why do the large trucks >>>and tour buses still use drums on all axles? I know there are some >>>exceptions but most use drums. I hadn't really considered this until your >>>above comments... >>> >>>Dave D >> >>very few of the modern tour buses use drums these days, or at least, not >>on the front. > > Hate to disagree with you but every MCI coach I have driven in the past 10 > years, including new ones, all had drums on all axles. http://www.mcicoach.com/parts-servic...sDrum2Disc.htm euro coaches like setra & van hool have had them for more than a decade. > I checked with our > shop chief and he says it has to do with the larger swept area of the > drum/shoe brakes as opposed to the disk/pad brakes. It is true that the > disks will not heat up as quickly and are less susceptible to fade and water > but the increased stopping power is the reason he gave me. nope. see above. > >>the main reason drums are still used on large trucks, especially big rigs, >>is because of the air brake thing. unlike cars and lighter vehicles, >>they're "fail safe" which means their "natural" position is full on as >>opposed to off like a car. strong springs inside the drums press the >>shoes real hard against the drum, and the air system actuates against the >>springs to hold the shoes off the drum so the vehicle can roll. if the >>braking system fails, the brakes come on, and the 30+ ton cargo comes to a >>halt. hopefully. "fail safe" is much more complicated to implement on >>disk brakes, but real simple inside a drum. plus imo, a lot of domestic >>truck manufacturers are not exactly innovative pioneers in the engineering >>department - the quality of the chrome plating seems to get more attention >>from what i can see. > > > Actually, there are two systems at work there. The service brakes are > activated via an "S" cam and release when the pedal is no longer depressed. > You are quite correct, however, that in the event of catastrophic air > pressure loss, the failsafe system that you describe will lock up (full on) > all the brakes. Rather an unsettling experience I might add. > > Dave D > > |
Re: Setting Toe
Dave and Trudy wrote:
> "jim beam" <nospam@example.net> wrote in message > news:KtKdnT4xV5_ccQbZnZ2dnUVZ_rOdnZ2d@speakeasy.ne t... > >>Dave and Trudy wrote: >> >>>"TeGGeR®" <tegger@tegger.c0m> wrote in message >>>news:Xns97EADC0BC8473tegger@207.14.116.130... >>> >>> >>>>"R Flowers" <rflowers@Tinbowlinggreen.com> wrote in >>>>news:FK6dnVW-malmfwfZnZ2dnUVZ_ridnZ2d@insightbb.com: >>>>Ever driven un-powered 4-wheel drums? GAWD they were awful. Terrible! >>>>Plan >>>>your stops in advance, preferably in writing. >>>> >>>> >>>> >>>> >>>> >>>>>Then the front 2 discs came out, >>>> >>>> >>>> >>>>And it was akin to a religious conversion: YES LAWD, AH SEE THE LIGHT!!! >>>>Discs were a sea-change compared to drums. >>>> >>>> >>>> >>>> >>>> >>>>>and I guess people >>>>>thought "Well, if 2 are good, let's do all 4!" I remember sports cars >>>>>in the 70s and 80s touting their 4 wheel discs. >>>> >>>> >>>>Yep. But there is a point of diminishing returns, and rear discs was it. >>>>For road-going, legal speed, grocery-getting FWD cars, of course. >>>> >>>> >>>>-- >>>>TeGGeR® >>>> >>>>The Unofficial Honda/Acura FAQ >>>>www.tegger.com/hondafaq/ >>> >>>Just one question...If disks are so much better, why do the large trucks >>>and tour buses still use drums on all axles? I know there are some >>>exceptions but most use drums. I hadn't really considered this until your >>>above comments... >>> >>>Dave D >> >>very few of the modern tour buses use drums these days, or at least, not >>on the front. > > Hate to disagree with you but every MCI coach I have driven in the past 10 > years, including new ones, all had drums on all axles. http://www.mcicoach.com/parts-servic...sDrum2Disc.htm euro coaches like setra & van hool have had them for more than a decade. > I checked with our > shop chief and he says it has to do with the larger swept area of the > drum/shoe brakes as opposed to the disk/pad brakes. It is true that the > disks will not heat up as quickly and are less susceptible to fade and water > but the increased stopping power is the reason he gave me. nope. see above. > >>the main reason drums are still used on large trucks, especially big rigs, >>is because of the air brake thing. unlike cars and lighter vehicles, >>they're "fail safe" which means their "natural" position is full on as >>opposed to off like a car. strong springs inside the drums press the >>shoes real hard against the drum, and the air system actuates against the >>springs to hold the shoes off the drum so the vehicle can roll. if the >>braking system fails, the brakes come on, and the 30+ ton cargo comes to a >>halt. hopefully. "fail safe" is much more complicated to implement on >>disk brakes, but real simple inside a drum. plus imo, a lot of domestic >>truck manufacturers are not exactly innovative pioneers in the engineering >>department - the quality of the chrome plating seems to get more attention >>from what i can see. > > > Actually, there are two systems at work there. The service brakes are > activated via an "S" cam and release when the pedal is no longer depressed. > You are quite correct, however, that in the event of catastrophic air > pressure loss, the failsafe system that you describe will lock up (full on) > all the brakes. Rather an unsettling experience I might add. > > Dave D > > |
Re: Setting Toe
Dave and Trudy wrote:
> "jim beam" <nospam@example.net> wrote in message > news:KtKdnT4xV5_ccQbZnZ2dnUVZ_rOdnZ2d@speakeasy.ne t... > >>Dave and Trudy wrote: >> >>>"TeGGeR®" <tegger@tegger.c0m> wrote in message >>>news:Xns97EADC0BC8473tegger@207.14.116.130... >>> >>> >>>>"R Flowers" <rflowers@Tinbowlinggreen.com> wrote in >>>>news:FK6dnVW-malmfwfZnZ2dnUVZ_ridnZ2d@insightbb.com: >>>>Ever driven un-powered 4-wheel drums? GAWD they were awful. Terrible! >>>>Plan >>>>your stops in advance, preferably in writing. >>>> >>>> >>>> >>>> >>>> >>>>>Then the front 2 discs came out, >>>> >>>> >>>> >>>>And it was akin to a religious conversion: YES LAWD, AH SEE THE LIGHT!!! >>>>Discs were a sea-change compared to drums. >>>> >>>> >>>> >>>> >>>> >>>>>and I guess people >>>>>thought "Well, if 2 are good, let's do all 4!" I remember sports cars >>>>>in the 70s and 80s touting their 4 wheel discs. >>>> >>>> >>>>Yep. But there is a point of diminishing returns, and rear discs was it. >>>>For road-going, legal speed, grocery-getting FWD cars, of course. >>>> >>>> >>>>-- >>>>TeGGeR® >>>> >>>>The Unofficial Honda/Acura FAQ >>>>www.tegger.com/hondafaq/ >>> >>>Just one question...If disks are so much better, why do the large trucks >>>and tour buses still use drums on all axles? I know there are some >>>exceptions but most use drums. I hadn't really considered this until your >>>above comments... >>> >>>Dave D >> >>very few of the modern tour buses use drums these days, or at least, not >>on the front. > > Hate to disagree with you but every MCI coach I have driven in the past 10 > years, including new ones, all had drums on all axles. http://www.mcicoach.com/parts-servic...sDrum2Disc.htm euro coaches like setra & van hool have had them for more than a decade. > I checked with our > shop chief and he says it has to do with the larger swept area of the > drum/shoe brakes as opposed to the disk/pad brakes. It is true that the > disks will not heat up as quickly and are less susceptible to fade and water > but the increased stopping power is the reason he gave me. nope. see above. > >>the main reason drums are still used on large trucks, especially big rigs, >>is because of the air brake thing. unlike cars and lighter vehicles, >>they're "fail safe" which means their "natural" position is full on as >>opposed to off like a car. strong springs inside the drums press the >>shoes real hard against the drum, and the air system actuates against the >>springs to hold the shoes off the drum so the vehicle can roll. if the >>braking system fails, the brakes come on, and the 30+ ton cargo comes to a >>halt. hopefully. "fail safe" is much more complicated to implement on >>disk brakes, but real simple inside a drum. plus imo, a lot of domestic >>truck manufacturers are not exactly innovative pioneers in the engineering >>department - the quality of the chrome plating seems to get more attention >>from what i can see. > > > Actually, there are two systems at work there. The service brakes are > activated via an "S" cam and release when the pedal is no longer depressed. > You are quite correct, however, that in the event of catastrophic air > pressure loss, the failsafe system that you describe will lock up (full on) > all the brakes. Rather an unsettling experience I might add. > > Dave D > > |
Re: Setting Toe
jim beam wrote:
> Dave and Trudy wrote: <snip> >> Just one question...If disks are so much better, why do the large >> trucks and tour buses still use drums on all axles? I know there are >> some exceptions but most use drums. I hadn't really considered this >> until your above comments... >> >> Dave D >> > very few of the modern tour buses use drums these days, or at least, not > on the front. > > the main reason drums are still used on large trucks, especially big > rigs, is because of the air brake thing. unlike cars and lighter > vehicles, they're "fail safe" which means their "natural" position is > full on as opposed to off like a car. strong springs inside the drums > press the shoes real hard against the drum, and the air system actuates > against the springs to hold the shoes off the drum so the vehicle can > roll. if the braking system fails, the brakes come on, and the 30+ ton > cargo comes to a halt. hopefully. "fail safe" is much more complicated > to implement on disk brakes, but real simple inside a drum. plus imo, a > lot of domestic truck manufacturers are not exactly innovative pioneers > in the engineering department - the quality of the chrome plating seems > to get more attention from what i can see. Plus interstate buses and 18-wheelers are seldom bought on the strength of some advertising campaign (as opposed to passenger vehicles), IMHO anyway. |
Re: Setting Toe
jim beam wrote:
> Dave and Trudy wrote: <snip> >> Just one question...If disks are so much better, why do the large >> trucks and tour buses still use drums on all axles? I know there are >> some exceptions but most use drums. I hadn't really considered this >> until your above comments... >> >> Dave D >> > very few of the modern tour buses use drums these days, or at least, not > on the front. > > the main reason drums are still used on large trucks, especially big > rigs, is because of the air brake thing. unlike cars and lighter > vehicles, they're "fail safe" which means their "natural" position is > full on as opposed to off like a car. strong springs inside the drums > press the shoes real hard against the drum, and the air system actuates > against the springs to hold the shoes off the drum so the vehicle can > roll. if the braking system fails, the brakes come on, and the 30+ ton > cargo comes to a halt. hopefully. "fail safe" is much more complicated > to implement on disk brakes, but real simple inside a drum. plus imo, a > lot of domestic truck manufacturers are not exactly innovative pioneers > in the engineering department - the quality of the chrome plating seems > to get more attention from what i can see. Plus interstate buses and 18-wheelers are seldom bought on the strength of some advertising campaign (as opposed to passenger vehicles), IMHO anyway. |
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