Author |
Topic |
|
JSandoval
New Member
2 Posts |
Posted - 01/21/2017 : 5:52:18 PM
|
We are looking into buying new 2017 school buses what is recommend? |
|
International-9.0
Advanced Member
USA
459 Posts |
Posted - 01/21/2017 : 7:30:48 PM
|
Well, that's a bit of a complicated question. Several ideas come to mind...but I'm sure the experienced mechanics here can give you much better feedback than I.
1. Is cost a consideration? Hydraulic brakes are usually less money. Air costs a bit more. Air brake systems also cost quite a bit more to maintain. You have to worry about slack adjustment, proper air dryer function and maintenance, air compressor problems, air line leaks, etc. Hydraulic brakes are more or less self maintaining, although you will have to change the pads (and bleed lines) a bit more often than the air brake shoes.
2. Air brakes shoes usually last quite a bit longer before needing new shoes. If you are running mountain territory or have routes with a large number of high speed stops or driving in heavy stop and go traffic-you might consider air brakes. They also have a bit more stopping power under heavy loads.
3. If you are buying IC, I'd completely avoid the hydro systems on these buses as the SAHR units are alot of trouble, from what I hear. I'm not sure on BB and Thomas, but I haven't heard anything specific about their hydraulic brake systems. Perhaps other mechanics here have input.
So, it's really a matter of what your priorities are. Cost, maintenance, stopping power, etc. Perhaps you like the "pshhhhhhhh" from the air dryer purge valve? :D It seems more people I talk to are air brake people, but it all depends on the person, the bus and the application.
I hope that this is helpful.
|
|
|
Fastback
Top Member
1500 Posts |
Posted - 01/23/2017 : 04:10:21 AM
|
Do your drivers have air brake endorsements? State rules? In Iowa you can't buy a bus over 66 passenger unless it has air brakes. We never have had an air brake line rust out and fail, hydraulic yes. For us compressor, drier and slack adjuster problems are rare and for the most part no matter the bus brand the air brakes are the same.
Personally, I don't even consider buses with hydraulic brakes anymore.
I also don't consider buses without rear air ride suspension which is not an expensive option, as long as you have air brakes. |
Why yes, the ORIGinal CHARGER is a Fastback |
Edited by - Fastback on 01/23/2017 04:15:07 AM |
|
|
BigPapa
Advanced Member
215 Posts |
Posted - 01/23/2017 : 05:37:41 AM
|
The only buses we have with hydraulic brakes are the small van cut-a-way models. That makes @ 750 with air and @ 45 with hydraulic. |
|
|
drp53188
Senior Member
89 Posts |
Posted - 01/23/2017 : 10:40:24 AM
|
The HABS system on IC buses is a very good system we run that system on 50 buses you just have to understand it and lean how to service the system. The people that have trouble with the SHARS canister don`t do the prevenitive maintenance and keep everything lubed and clean. |
|
|
jeeptjken
Senior Member
147 Posts |
Posted - 01/23/2017 : 11:39:19 AM
|
nothing but air brakes in our fleet lines never rust that's a big plus here in the rust belt
|
How did you get the gosinta in the whatchamacallit |
|
|
bwest
Administrator
United States
3820 Posts |
Posted - 01/23/2017 : 1:59:18 PM
|
quote: Originally posted by International-9.0
Well, that's a bit of a complicated question. Several ideas come to mind...but I'm sure the experienced mechanics here can give you much better feedback than I.
1. Is cost a consideration? Hydraulic brakes are usually less money. Air costs a bit more. Air brake systems also cost quite a bit more to maintain. You have to worry about slack adjustment, proper air dryer function and maintenance, air compressor problems, air line leaks, etc. Hydraulic brakes are more or less self maintaining, although you will have to change the pads (and bleed lines) a bit more often than the air brake shoes.
2. Air brakes shoes usually last quite a bit longer before needing new shoes. If you are running mountain territory or have routes with a large number of high speed stops or driving in heavy stop and go traffic-you might consider air brakes. They also have a bit more stopping power under heavy loads.
3. If you are buying IC, I'd completely avoid the hydro systems on these buses as the SAHR units are alot of trouble, from what I hear. I'm not sure on BB and Thomas, but I haven't heard anything specific about their hydraulic brake systems. Perhaps other mechanics here have input.
So, it's really a matter of what your priorities are. Cost, maintenance, stopping power, etc. Perhaps you like the "pshhhhhhhh" from the air dryer purge valve? :D It seems more people I talk to are air brake people, but it all depends on the person, the bus and the application. What fastback said about your drivers must be considered. If they don't have the air brake endorsement you WILL see a revolt, no matter how much sense it makes to you.
I hope that this is helpful.
I agree with this post. I was taught air brakes but have never seen the need on a bus that's less than 30k lbs loaded in our flat area. The vast majority of the buses in our area are hydraulic. |
Bryan |
|
|
bfaulkner
Senior Member
168 Posts |
Posted - 01/23/2017 : 2:22:07 PM
|
We run strictly Air in my district. We are in a rust state so there are no steel lines to rust or fluid to loose. the air is used for brakes, door, seat, and sign so its versatile.
This spring we have ordered 2 IC with air disc brake. It seems amazing with fewer moving parts and hopefully longer life. |
|
|
Mechan1c
Top Member
USA
853 Posts |
Posted - 01/23/2017 : 4:49:12 PM
|
Not enough information from the original poster. Some quick questions:
1. Geography? (ups and downs) 2. Locale (rust belt?) 3. Size of the bus? 4. How long will you keep the bus? 5. Do you work on your own buses? 6. What are you tooled up to work on? 7. Shop skill level?
|
|
|
bwest
Administrator
United States
3820 Posts |
Posted - 01/24/2017 : 05:19:44 AM
|
quote: Originally posted by bfaulkner
This spring we have ordered 2 IC with air disc brake. It seems amazing with fewer moving parts and hopefully longer life.
Ah, now there's something I might be interested in! I guess the other obstacle in my own mind has been the old technology of drums. Good to hear that they are going disc. |
Bryan |
|
|
aaronwilmoth80911
Top Member
538 Posts |
Posted - 01/24/2017 : 05:30:31 AM
|
We have a few IC with air disc, and they are pretty nice. I think they say the norm is 3 sets of pads before you need to change a rotor. No slack adjuster measurements, and simple to maintain.
As far as the doors, we went electric because IC changed up the design a few years back and they are terrible now, we've had nothing but problems.
Now onto the original question. I believe the rules in my state have been changed to where any type C or type D bus requires air brakes. We have a couple type A with hydraulic, obviously, and have not had any problems. However, we are not in the rust belt. I personally like air because of what was stated with it being so versatile for other things on the bus. |
|
|
Thomasbus24
Administrator
USA
4544 Posts |
Posted - 01/24/2017 : 05:51:27 AM
|
Air brakes, nothing else! Just my opinion.
I just ordered 3 CE's with air disk too. Test drove a bus with them recently and was sold on it...now just hoping I don't regret it later! |
|
|
International-9.0
Advanced Member
USA
459 Posts |
Posted - 01/24/2017 : 4:50:13 PM
|
Yes, the steel lines rusting problem is a very good point I didn't think to bring up. We don't have any road salt down here, so that's never an issue for us.
My parents have a motorhome with air disc brakes, but only on the front wheels. The rear ones are drums.
Do the buses you are referencing have air disc brakes on all wheels? If so, how does the parking brake work? How do the disc brakes actually apply? I've heard of a screw style before, but never really studied how they work. Do chambers on either side of the pad simply pressurize and push the brake pads against the rotor (just like hydraulic except using air)?
For DRP-As for the IC HABS and SAHR designs, you are the first person I've ever talked to that has anything good to say about them. I have a friend who owns a used bus stealership and he told me that he has to work on/replace every single unit that comes in with this system. I think the fail-safe design is a very good idea, but I think the engineering leaves something to be desired. Several units he had worked on at the dealer had to be taken back several weeks after the units had been completely replaced and fixed under warranty. Perhaps the dealer didn't install properly, but who really knows. I know if the if the electric pumps fail, you have to change the entire assembly, which is rather expensive. I think some components are replaceable, but I cannot remember which ones.
Maybe some people have had better luck than others with them and they have just gotten a bad name from those who had trouble. I just know I never hear anything good from anybody who has a bus with that system. What kind of maintenance does the system require? I always figured it was maintenance free other than exchanging fluids from time to time.
Jonathan
|
|
|
Fastback
Top Member
1500 Posts |
Posted - 01/25/2017 : 03:48:25 AM
|
quote: Originally posted by bwest
quote: Originally posted by bfaulkner
This spring we have ordered 2 IC with air disc brake. It seems amazing with fewer moving parts and hopefully longer life.
Ah, now there's something I might be interested in! I guess the other obstacle in my own mind has been the old technology of drums. Good to hear that they are going disc.
Differant strokes I guess. I list drums as one of the advantages of air brakes. |
Why yes, the ORIGinal CHARGER is a Fastback |
|
|
Thomasbus24
Administrator
USA
4544 Posts |
Posted - 01/25/2017 : 04:32:41 AM
|
quote: Originally posted by International-9.0
Do the buses you are referencing have air disc brakes on all wheels? If so, how does the parking brake work? How do the disc brakes actually apply? I've heard of a screw style before, but never really studied how they work. Do chambers on either side of the pad simply pressurize and push the brake pads against the rotor (just like hydraulic except using air)?
Disk at all wheel.
Check out these videos, they are pretty good...
https://www.youtube.com/watch?v=C-4VAt-JXOA
https://www.youtube.com/watch?v=mWlBU_9v7AU |
|
|
International-9.0
Advanced Member
USA
459 Posts |
Posted - 01/26/2017 : 6:08:10 PM
|
Interesting links! I enjoyed watching the guy demonstrate how to change pads. Looks pretty easy and no real adjustments to make. I'm still curious as to exactly how those work, but haven't had time to look up diagrams. Apparently they use the same style chambers as a drum system, but the pushrods are just a bit different. Thanks for the links Thomasbus24.
Jonathan |
|
|
bwest
Administrator
United States
3820 Posts |
|
International-9.0
Advanced Member
USA
459 Posts |
Posted - 01/28/2017 : 2:10:55 PM
|
Good link. I looked up a few other videos. It seems like the Meritor-Wabco design has the adjuster in the center of the pistons. I'm still not quite sure how the adjuster works in the Bendix. Either way, they both seem to work on a ratcheting screw drive that screws out to keep the clearance to the specified amount. You back off the clearance to change pads. Then tighten the whole thing up and back out a specified number of clicks or turns. I know the adjuster must have a preset clearance (maybe a mm or 2?) so that the brakes do not stick when they get hot. Instead of the drum expanding outward and causing brake fade, these could very well get "stuck on" where release was not possible when they were heated to really high temps. It would still be interesting to see the internals of the adjuster and how it keeps the the slack at the right amount.
It seems the discs have several inherent advantages: Longer pad life, better cooling, better performance in water, better stopping performance, no brake fade, shorter down time, no lubrication points, no slack adjustment problems, etc. The actually percentage of advantage would be subject to heavy debate, but I think there are definite advantages. I think the only disadvantages the increased cost and the extra weight (for weight sensitive applications). Anybody else heard any gripes about these? |
|
|
bwest
Administrator
United States
3820 Posts |
Posted - 01/30/2017 : 05:32:29 AM
|
So, is it just the buses I've been on in my area or do all air brake buses apply harshly? What I'm saying is that the ones I've test driven have all seemed like they slow suddenly when applying the brakes? If so, would this be averted with disc? |
Bryan |
|
|
Thomasbus24
Administrator
USA
4544 Posts |
Posted - 01/30/2017 : 05:41:18 AM
|
Being used to air brakes I don't notice any harshness. The air disk buses do seem to stop more evenly and smoothly than the drum buses, but you will put your nose to the windshield if you get on the pedal hard. |
|
|
Fastback
Top Member
1500 Posts |
Posted - 01/30/2017 : 09:30:05 AM
|
We have mostly air brakes (all drum) and a few 2001 and older buses with hydraulic disc brakes, I can't tell much difference in brake application between any of them. |
Why yes, the ORIGinal CHARGER is a Fastback |
|
|
drp53188
Senior Member
89 Posts |
Posted - 01/30/2017 : 10:25:07 AM
|
Again, if you don`t know the system you WILL pull your hair out. My buses live in an area that uses salt and liquid cloride on the roads and some parts of that system just don`t hold up to that. As far as cost the HCU rebuilt is around 2000.00 some parts are serviced some not. Out of 50 i have replaced 5 or 6 HCUs over the years but that`s 2007 to 2009 buses, just my 02 cents. |
|
|
bfaulkner
Senior Member
168 Posts |
Posted - 01/30/2017 : 10:29:35 AM
|
quote: Originally posted by bwest
So, is it just the buses I've been on in my area or do all air brake buses apply harshly? What I'm saying is that the ones I've test driven have all seemed like they slow suddenly when applying the brakes? If so, would this be averted with disc?
If i get your complaint there is a pop and the suddenly break hard? if so i would say they are out of adjustment. I go between hydraulic and air all the time and haven't noticed a difference unless they are out of adjustment. And i must say my newer internationals with Bendix breaks go out of adjustment often. |
|
|
RonF
Top Member
867 Posts |
Posted - 01/30/2017 : 12:38:48 PM
|
quote: Originally posted by bfaulkner
quote: Originally posted by bwest
So, is it just the buses I've been on in my area or do all air brake buses apply harshly? What I'm saying is that the ones I've test driven have all seemed like they slow suddenly when applying the brakes? If so, would this be averted with disc?
If i get your complaint there is a pop and the suddenly break hard? if so i would say they are out of adjustment. I go between hydraulic and air all the time and haven't noticed a difference unless they are out of adjustment. And i must say my newer internationals with Bendix breaks go out of adjustment often.
We brought this up in a class with Haldex some years ago and the instructor said if build you air up to full pressure then pump your brakes hard about 4 or 5 times, once in the morning and once in the afternoon it will take care of that sudden braking hard. It helps keep the brakes adjusted. I've tried for for about 4 years now and for the most part it works. |
US Army retired CMBT |
|
|
bfaulkner
Senior Member
168 Posts |
Posted - 01/30/2017 : 2:12:48 PM
|
quote: Originally posted by RonF We brought this up in a class with Haldex some years ago and the instructor said if build you air up to full pressure then pump your brakes hard about 4 or 5 times, once in the morning and once in the afternoon it will take care of that sudden braking hard. It helps keep the brakes adjusted. I've tried for for about 4 years now and for the most part it works.
This should be a thread in itself. but you should be right in theory. In practice i have found it to be wish washy.
Either way don't let that scare you from air brakes. I still would recommend them to everyone. |
|
|
wrenchsnapper
Active Member
27 Posts |
Posted - 01/30/2017 : 7:01:54 PM
|
I am in the buckle of the rust belt. We ran IC wabco hydraulic up until 2012 when we switched to the Freightliner chassis with air. Within 40,000 miles every single rear axle had worn the right lower shoes down to minimum, every factory air chamber spring rusted and broke, the stock drums were worn to minimum on the first shoe change. Many front brakes had no wear but the shoes all had cracks needing replacement. We replaced with aftermarket and most are over 100,000 now and still going. As far as the IH hydraulic expenses go up on the newer systems as the tone rings rust and pop off the hubs requiring new hubs ,as well as rotors to repair. Labor times are substantially longer on these systems as well. They did however go to coated brake lines in 2009 so some of the lines may make it 9 to 10 years before rust through. I would go with air but spec good quality parts instead of bottom shelf original parts. |
|
|
International-9.0
Advanced Member
USA
459 Posts |
Posted - 01/30/2017 : 7:22:06 PM
|
Thanks for the continued input DRP. That's far less units to replace than I would have suspected. I think that you are right that it's important to "know" the system you are working on and know what you can replace without changing the whole unit. Salt and chloride destroy pretty much everything, even concrete. No brake system is fully immune to the effects of this stuff.
I think the "grabbiness" or large chunkiness of air brake applications can be caused by several things:
1. Unfamiliarity with air brakes or just not regularly driving a vehicle that has them. There is a delay between when you move the pedal and when the brakes apply. The natural human tendency is to push a little more and and little more until you get the braking you want. This can cause you to get more braking power at one time than you initially desired. Driving a bus regularly with air brakes helps to get around this a bit.
2. Treadle valves can have different sensitivities due to design, wear & tear, temperatures, etc. Sometimes the changes in pressure may just come in larger steps with particular treadle valves. Not much you can do, but change or rebuild the valve.
3. Drum brakes have a known tendency to be a little grabby under certain conditions. Any kind of differential fluid/bearing oil, grease, water or other contaminants will affect how they work. Even just small amounts of contaminants make a big difference. We've had buses with sticky brakes that weren't smooth (smooth in applying or releasing, not in stopping power) and would sometimes stick because the grease in the slack adjuster and area around the s-cam got really old and sticky (poor maintenance).
I do think hydraulic brakes allow you to control your braking to a much finer level (in terms of the exact amount of braking you want, less "chunky" if you will). You also get the effect of any changes instantaneously. I'm not saying one is better than the other, but just sharing my thoughts on how the increments between the 2 types of system compare.
Jonathan
|
|
|
|
Topic |
|