Posted 2009-04-17 3:01 PM (#103521) Subject: Why don't they use disc brakes on trailers?
Veteran
Posts: 241
I've noticed that even the top name trailers are not using disc brakes on trailers... is it the cost or is there a reason disc brakes are not well suited for horse/stock trailers?
Posted 2009-04-17 8:21 PM (#103531 - in reply to #103521) Subject: RE: Why don't they use disc brakes on trailers?
Expert
Posts: 2453 Location: Northern Utah
Could it be the space required for the disk and calipers? Since most trailers are trying to push the wheels as far out to the edge of the trailer to keep room inside for the horses. Also most trailers are Torson axles. Does this pose some problems for adding a disk and caliper?
Posted 2009-04-17 10:19 PM (#103539 - in reply to #103521) Subject: RE: Why don't they use disc brakes on trailers?
Expert
Posts: 1351 Location: Decatur, Texas
Do they even make disc brakes that are "electric" or would you have to convert to a hydraulic brake system? Or I should say electric over hydraulic brake system, which the price is a little high for the avg. trailer.
So that being said, this would be the reason that most manufactures do not use them because of the cost factor.
Posted 2009-04-17 10:22 PM (#103540 - in reply to #103521) Subject: RE: Why don't they use disc brakes on trailers?
Extreme Veteran
Posts: 383 Location: Texas
You can get disc brakes, mine has them. They are more expensive but they also have benefits. You have to have an electric/hydraulic actuator, vacuum/hydraulic actuator or air/hydraulic actuator..... all of which are expensive. They have better stopping power especially on long hills where brakes get hot. And they should be easier to service (I haven't needed to yet so I don't know). I have oil bath hubs on my trailer so it was a no-brainer to get disc brakes so I don't have to pull the hubs to work on the brakes.
I think cost is the biggest part of why they aren't on more trailers.
Posted 2009-04-18 8:47 AM (#103550 - in reply to #103521) Subject: RE: Why don't they use disc brakes on trailers?
Location: Central Arkansas
The integrated brake controller in my 2008 Ford 450 works fine with my Bloomer with elec/hydraulic brakes. Although, I rarely pull that trailer with it, it seems to work well when I have.
Posted 2009-04-18 9:03 PM (#103578 - in reply to #103521) Subject: RE: Why don't they use disc brakes on trailers?
Extreme Veteran
Posts: 317 Location: Barnesville, Ga.
Replaced my drums with electric hydraulic last fall. LOVE THEM. Will not ever have another heavy trailer without them. They are the best thing since sliced bread. Consistent stopping power everytime. My guess would be the initial cost. I think most manufacturers take a gamble on how much their trailers are going to be used. Seems like a lot of folks buy them for yard art, and are only looking for the cheap price. Price sells brakes usually don't unless you have had problems in the past. You just take it for granted that it will stop and not have blow outs. So put a cheap tire and cheap brakes and if it don't get used often no problems 90% of the time. For the other 10% deal with them on a case by case basis.
Posted 2009-04-19 12:02 AM (#103589 - in reply to #103578) Subject: RE: Why don't they use disc brakes on trailers?
Expert
Posts: 3853 Location: Vermont
Originally written by tom-tom on 2009-04-18 10:03 PM
Replaced my drums with electric hydraulic last fall. LOVE THEM. Will not ever have another heavy trailer without them. They are the best thing since sliced bread. Consistent stopping power everytime. My guess would be the initial cost. I think most manufacturers take a gamble on how much their trailers are going to be used. Seems like a lot of folks buy them for yard art, and are only looking for the cheap price. Price sells brakes usually don't unless you have had problems in the past. You just take it for granted that it will stop and not have blow outs. So put a cheap tire and cheap brakes and if it don't get used often no problems 90% of the time. For the other 10% deal with them on a case by case basis.
Posted 2009-04-19 8:05 AM (#103593 - in reply to #103521) Subject: RE: Why don't they use disc brakes on trailers?
Expert
Posts: 2453 Location: Northern Utah
When you look at the difference in buy standard hub brakes vs disk the cost isn't that much more. It seems the actuator is the only real cost increase.
Posted 2009-04-19 8:54 AM (#103597 - in reply to #103589) Subject: RE: Why don't they use disc brakes on trailers?
Expert
Posts: 3802 Location: Rocky Mount N.C.
Originally written by PaulChristenson on 2009-04-19 1:02 AM
Originally written by tom-tom on 2009-04-18 10:03 PM
Replaced my drums with electric hydraulic last fall. LOVE THEM. Will not ever have another heavy trailer without them. They are the best thing since sliced bread. Consistent stopping power everytime. My guess would be the initial cost. I think most manufacturers take a gamble on how much their trailers are going to be used. Seems like a lot of folks buy them for yard art, and are only looking for the cheap price. Price sells brakes usually don't unless you have had problems in the past. You just take it for granted that it will stop and not have blow outs. So put a cheap tire and cheap brakes and if it don't get used often no problems 90% of the time. For the other 10% deal with them on a case by case basis.
Posted 2009-04-19 12:50 PM (#103608 - in reply to #103521) Subject: RE: Why don't they use disc brakes on trailers?
Extreme Veteran
Posts: 317 Location: Barnesville, Ga.
The 7k brake in disc is the same rotor and caliper as the 8k. So you get more braking on a 7K axle. Additionally you can change the pads for even more stopping power. The kodiak kit uses a standard GM disc brake assembly, and that gives you a bunch of different pads to select from. 7k backing plates per set $210 new drums $130 total $340/set. New rotors pads calipers $322/set. The pump is the main additional cost. The cost is more noticeable on the 7.2K and 8K axles, as there components are considerablely more expensive $830/set. The consistency you get with electric hydraulic is nice. Magnets heat up more and fade and grab more you don't have that problem with hydraulic. Also, the Kodiak kit can be used as oil lube or grease lube it just depends on which oil seal you use. You don't ever have to work about grease ruinning a set of shoes and losing brakes. Electric hyd pump costs about $600 and a hydraulic line kit costs another $100.
Posted 2009-04-19 10:25 PM (#103635 - in reply to #103594) Subject: RE: Why don't they use disc brakes on trailers?
Extreme Veteran
Posts: 383 Location: Texas
Originally written by wyndancer on 2009-04-19 8:06 AM
If disk brakes are "all that and a bag of chips" then why don't class 8 trucks and semi trailers have disk brakes?
They are moving toward that in the next few years, many trucks in Europe already do. Air discs are more complicated than air drums from what I've seen so that's probably the main reason they aren't using them already. Air drums are a heck of a lot better than electric trailer brakes are to begin with too.
Posted 2009-04-19 10:44 PM (#103638 - in reply to #103594) Subject: RE: Why don't they use disc brakes on trailers?
Expert
Posts: 3853 Location: Vermont
Originally written by wyndancer on 2009-04-19 9:06 AM
If disk brakes are "all that and a bag of chips" then why don't class 8 trucks and semi trailers have disk brakes?
They do...
All Major OEMs Offer Bendix Air Disc Brakes
3/20/2009
Bendix Spicer Foundation Brake announced that Bendix ADB22X air disc brakes are now available as options on select platforms at all six of the major truck OEMs for the first time, including Peterbilt, Kenworth, Daimler Trucks North America, Mack, Volvo, and International.
The Bendix ADB22X air disc brake - which has also been released as an option at Utility Trailer and Hendrickson Trailer Suspension Systems - is a lightweight air disc brake package that reduces total wheel-end weight over competitive air disc brake packages, offers longer brake life, and provides fast and easy pad replacement, improving uptime.
Easy access to the air disc brake pads allows for minimized maintenance labor and expense, allowing drivers and fleets to reduce downtime.Bendix air disc brakes have experienced a 30 percent year-over-year growth in units sold in each of the past three years.
An estimated 150,000 Bendix air disc brakes are now in use on North American highways.
Posted 2009-04-20 2:39 AM (#103641 - in reply to #103521) Subject: RE: Why don't they use disc brakes on trailers?
Veteran
Posts: 177 Location: East London South Africa
I had discs on my old home built 4H GN.... they were awsome, and I am sorry my new Trailer does not have them...They were elec over Hyd. We used landrover Discovery discs and calipers that we got from a breakers yard and were really cheap.... The discs just slip over the tortion axel hub and are kept in place by the wheele. We mounted the caliper by placing the caliper on the disc where we wanted it - then actuated the pump, which clamped the caliper to the disc. Then I made a plate to join the axel and the caliper... bolted it to the caliper and welded it to the axel....whalla and it was done.
If I recall the whole excercize cost less than $1000 and that included importing the actuator pump and controller....
I think I will convert my trailer when the time comes to overhaul the existing drums...they are just too new to waste at the moment...
Posted 2009-04-20 7:34 AM (#103644 - in reply to #103635) Subject: RE: Why don't they use disc brakes on trailers?
Extreme Veteran
Posts: 406 Location: Minneapolis, MN
Originally written by greyhorse on 2009-04-19 10:25 PM
Originally written by wyndancer on 2009-04-19 8:06 AM
If disk brakes are "all that and a bag of chips" then why don't class 8 trucks and semi trailers have disk brakes?
They are moving toward that in the next few years, many trucks in Europe already do. Air discs are more complicated than air drums from what I've seen so that's probably the main reason they aren't using them already. Air drums are a heck of a lot better than electric trailer brakes are to begin with too.
I heard, and maybe the manufacturers have this addressed, is that the braking area on a drum is greater than can be had on a disk?
Posted 2009-04-20 11:20 AM (#103656 - in reply to #103521) Subject: RE: Why don't they use disc brakes on trailers?
Extreme Veteran
Posts: 383 Location: Texas
I'm not sure how they deal with the braking area, I think the disc brakes apply more pressure to the pads than drums do to the shoes so maybe that's it. What I understand about the class 8 trucks going to discs over the next few years is that it's because it will allow them to stop in a shorter distance (emergency braking). I wonder how the reaction time of the two kinds of brakes compares (I'm talking air brakes here), I know there is a lag on the current air brakes that use drums from when you push the pedal to when the braking occurs.
Posted 2009-04-20 3:58 PM (#103686 - in reply to #103644) Subject: RE: Why don't they use disc brakes on trailers?
Expert
Posts: 5870 Location: western PA
Originally written by wyndancer on 2009-04-20 7:34 AM
I heard, and maybe the manufacturers have this addressed, is that the braking area on a drum is greater than can be had on a disk?
The largest difference between the two systems, disc and drum, is how much heat can be dissipated the fastest. Brakes work by converting energy to heat. A drum cannot be quickly cooled, a disc can. Newer disc designs have cooling slots cut into the surface that expels the gases and assists cooling.
Discs have pads on both sides of the rotors, that are evenly pushed together at high pressures. Drums have shoes that only push outwards. Discs use multiple pistons to increase the pressures and friction, most drums only have one cylinder actuating multiple shoes.
By being able to cool the disc at a faster rate, higher pressures and higher braking temperatures can be used for more efficiency. The braking capabilities between the two systems are not just a function of the braking pad surface areas. High performance braking systems are now using 4 and 6 piston designs, with composite rotors and ceramic pads.
Commercial aircraft use disc brake systems, that can have more than a dozen brake rotors that are stacked together. They have to stop up to a half a million pounds of energy traveling at 160 knots, in less than a mile.
Why don't they use disc brakes on trailers?
