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Author Topic: Front Disc Brake Conversion  (Read 2238 times)
TomCat
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« on: June 04, 2006, 02:39:02 PM »

I'm considering converting the front air drum brakes on my 1987 Thomas SaftLiner to air disc's, before I start shopping for Alcoa's. It seems like the easy way would be to find a compatable front axle, and just swap the entire axle and not have to worry about having to R&R any of the brake assembly. I'm presently equipped with a 12,080lb Rockwell front axle.
After being 95% complete with my conversion, I find my coach weighing in about 4000lbs below my 33,280 lb. GVW, and want to increase my stopping safety margin. I have a DD Series 50 w/Jake in my upgrade plans, but want maximum service brakes to get me started (stopping).
Does anyone have real world experience with a conversion such as this, or can supply a logical argument against it?

Jay
87 SaftLiner
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On The High Plains of Colorado
Burgermeister
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« Reply #1 on: June 04, 2006, 06:50:49 PM »

I am informed that the only way you can make this work is to add ABS the same time you switch brakes.  That's the only way you can incorporate the necessary proportioning valve to coordinate the disc brakes with the drum brakes.
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Nusa
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« Reply #2 on: June 04, 2006, 07:54:10 PM »

That doesn't make sense to me. Disc/Drum combos were around for decades before ABS became a reality.
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Burgermeister
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« Reply #3 on: June 04, 2006, 09:50:09 PM »

What didn't you understand about the only way to incorporate the necessary proportioning valve?  I'm informed that such is the only "flavor" they come in.

I wouldn't tell you such if they made a proportioning valve that wasn't integral with the ABS.
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Burgermeister
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« Reply #4 on: June 04, 2006, 09:55:37 PM »

That sounds a bit harsh on review.  I wasn't upset or trying to be insulting, just emphatic.  Please accept my apology if you were offended on initial reading.
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TomC
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« Reply #5 on: June 04, 2006, 10:00:54 PM »

In reality, drum brakes will stop a bus (or truck) the same distance (why do you think they are still using drum brakes on big rigs?).  They have the power to lock up the wheels at full axle capacity.  What more do you want?  What they won't do is maintain that braking power going down a long grade, whereas disc brakes will.  Maybe disc brakes would keep you at speed going down that long hill without fading, but the tremendous amount of heat created would most likely blow out your tires.  Many buses (particularly the transits) have the largest drum brakes made.  Still your best bet.  There are many different grades and types of lining material made for very specific applications.  I would first start by doing a really good brake job with appropriate brake lining material for your application.  Maybe your bus has transit linings that are harder and only work right after they are heated up.  This is why trucks working in mountains have Jake brakes.  Plus, if you're going to convert to discs, do all the axles.  Besides, it is your rear axle that does most the work, so I think you'd be a bit disappointed in the performance change with just doing the front axle.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
belfert
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« Reply #6 on: June 05, 2006, 05:49:04 AM »

heated up.  This is why trucks working in mountains have Jake brakes.  Plus, if you're going to convert to discs, do all the axles.  Besides, it is your rear axle that does most the work, so I think you'd be a bit disappointed in the performance change with just doing the front axle.  Good Luck,

Jake brakes don't do a damn bit of good in the mountains when engine brakes are not allowed to be used.  Engine brakes are prohibited on westbound I-80 coming into Salt Lake City.  That grade is more than steep enough to make make Jake brakes very useful.

Brian Elfert
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DrivingMissLazy
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« Reply #7 on: June 05, 2006, 05:52:57 AM »

That sounds a bit harsh on review.  I wasn't upset or trying to be insulting, just emphatic.  Please accept my apology if you were offended on initial reading.

Marc, that is what the Modify button is for. You can go back at any time and revise/modify your message if you think it is too harsh.
Richard
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TomC
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« Reply #8 on: June 05, 2006, 08:27:18 AM »

Brian- that's why when I was driving truck and going either west or east through SLC on I-80, (coming west) I would take I-84 to I-15 south to I-215 south back to I-80.  In reality, only about 10 miles out of the way and instead of going over the mountain and down that long downgrade, you go around the mountain and around most of SLC (avoiding traffic) on a very scenic route.

As to Jake brake restrictions, if you have a really good muffler, who's going to know?  It is the trucking cowboys that thinks it's cute to have straight pipes with Jake brake operation that ruins it for the rest of us.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #9 on: June 05, 2006, 08:38:00 AM »

When I first got my bus it had Jake's, turbo and a straight pipe. It sounded beautiful, but you could hear it at least five miles away.
The information I got was that if you had a turbo, you did not need a muffler. The turbo would quiet the Jake down.

No so, as far as I was concerned. I installed a good muffler and it made a world of difference. I could then use my Jake anywhere in the country on any grade and in any locality without worrying about the noise ordinances. Put on well over 100,000 miles and never had to change brake shoes.
Richard


As to Jake brake restrictions, if you have a really good muffler, who's going to know?  It is the trucking cowboys that thinks it's cute to have straight pipes with Jake brake operation that ruins it for the rest of us.  Good Luck, TomC
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Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body. But rather to skid in sideways, chocolate in one hand, a good Reisling in the other, body thoroughly used up, totally worn out and screaming:  WOO HOO, what a ride
Busted Knuckle
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« Reply #10 on: June 05, 2006, 09:01:34 AM »

Jake brakes don't do a damn bit of good in the mountains when engine brakes are not allowed to be used.  Engine brakes are prohibited on westbound I-80 coming into Salt Lake City.  That grade is more than steep enough to make make Jake brakes very useful.
Brian Elfert

That's one of the places I got a ticket for disturbing the golfers at the country club. it's also one of the tickets thrown out by the Judge after my lawyer asked "since when is it legal to outlaw a safety device? " BK
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Busted Knuckle aka Bryce Gaston
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belfert
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« Reply #11 on: June 05, 2006, 10:29:16 AM »

As to Jake brake restrictions, if you have a really good muffler, who's going to know?  It is the trucking cowboys that thinks it's cute to have straight pipes with Jake brake operation that ruins it for the rest of us.  Good Luck, TomC

My jake is pretty loud since my exhaust pipe is broken right now.  But, I am using the Jake a lot since my service brakes are not working 100%.

No, I have not been driving the bus much in this condition.  It goes to the shop tomorrow finally to get the exhaust and brakes fixed.

Brian Elfert
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