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Author Topic: Jake Brake and effectiveness  (Read 4475 times)
belfert
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« on: December 31, 2009, 09:25:20 AM »

I posted a long time ago that I didn't think my Jake Brake worked all that well.  The DDEC and WTEC together will downshift the B500 by one gear automatically any time the Jake Brake is engaged.  On my most recent trip I downshifted into 2nd or 3rd manually and man does the Jake Brake really work then!  I've never had any training on using the Jake Brake or I probably would have learned this long ago.

The road was quite slippery on my last trip and I ended up using the Jake Brake in combination with downshifting to keep the bus under control.  The bus would start sliding if the service brakes were used, but not with the Jakes.  I know they don't recommend use of engine brakes when slippery, but they seemed to work better than the regular brakes.

I like the Jake even better now that I know how to make it work better.  If it isn't keeping me slowed down enough I just downshift a gear.
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Brian Elfert - 1995 Dina Viaggio 1000 Series 60/B500 - 75% done but usable - Minneapolis, MN
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« Reply #1 on: December 31, 2009, 04:37:47 PM »

We have had excellent results with our Jakes on our 4104 [w/6-71].  Hwy 58 through the Tehachipi Mtns. here in California is a series of curving 5% grades.  Without the Jakes it was second and third gear and lots of brake action [they were getting hot on the last grade], the Jakes keep us at 45 mph in 4th and 35 in 3rd.  Not bad for a 52 year old GMC.  To say the least, we are more than happy their performance.
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rv_safetyman
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« Reply #2 on: December 31, 2009, 05:49:58 PM »

Hi Brian.  With my 10 speed, I just keep grabbing gears until I get the slowing effort I need.  Really easy with the AutoShift and it will not let you go into a gear that will hurt the engine.

In another thread you talked about letting the transmission "do its thing".  This is just one example why you should be "in control" of that device when the conditions are demanding.  I am told that some world transmissions have two control scenarios.  Even there, a good driver knows when to "take over" and optimize the operation. 

When I do my SilverLeaf seminar, I talk about using the engine information to help you make decisions on "getting up that big hill better".  There, you can watch engine temperature, air inlet temperature and turbo boost to help you make sure you are making your engine happy - by using the proper transmission gearing.  The turbo boost is your best indicator of how much you are asking of your engine.  Watching temperatures (transmission if you have a gauge), can guide you as to which gear to be in, or when to back off the throttle and "smell the roses".  I suggest watching the TREND of the gauges.  This will give you an early indication of when to shift.  If all the temperatures are holding well, then you are probably in the proper gear.  If any of the temperatures are trending upward, you know what to watch and can make the proper gear selection ahead of when a problem can occur.

Sorry, that is a bit off the subject, but somewhat related.

Lots of folks really discourage using Jakes when it is slick.  My take is that I put mine in the low or medium setting (two or four cylinders in my case) and really pay attention to what the bus it telling me.  I also try to keep my hand close to the switches to shut them off quickly.

You bring up an interesting point.  That is that Jakes are not very effective when the engine RPM is low.  We had an RV exit off of our infamous I 70 right at the bottom and did not have the brakes to stop him completely at the bottom.  Fortunately there was no traffic.  When he got to the nearby campground he was talking with my customer about how his Jakes did not work.  Turns out he simply left the transmission control set for normal highway (did not shift down) and you DO NOT DO THAT on I 70 heading into Denver.

Jim
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Jim Shepherd
Evergreen, CO
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« Reply #3 on: December 31, 2009, 06:08:37 PM »

If you have Jakes on a 2 stroke with a gear in the 3:33 to 3:76 range and in fourth or fifth gear with a Allision the Jakes are about useless as tits on a boar hog you better down shift and not wait for the tranny to do the work for you.
Check out the braking power on a 2 stroke then compare it to a 60s or any other 4 stroke  




good luck
« Last Edit: December 31, 2009, 06:10:17 PM by luvrbus » Logged

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« Reply #4 on: December 31, 2009, 10:42:04 PM »

It seems to me that if you are using your Jakes because your tires keep sliding when you use the brakes you are probably not driving appropriately for conditions.

How would you stop the bus if you had to make an emergency stop?


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Craig Shepard
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belfert
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« Reply #5 on: January 01, 2010, 05:55:21 AM »

It seems to me that if you are using your Jakes because your tires keep sliding when you use the brakes you are probably not driving appropriately for conditions.

How would you stop the bus if you had to make an emergency stop?

I was going all of 20 or 25 MPH and I did pull off the road for a while to let things improve.  Exits are far between whe you are going so slow.
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Brian Elfert - 1995 Dina Viaggio 1000 Series 60/B500 - 75% done but usable - Minneapolis, MN
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« Reply #6 on: January 01, 2010, 06:35:47 AM »

I have and mc9 with 8v71 and jakes with an automatic transmission.  I don't have very much experience with them but have noticed at low rpm (like slow speed driving) they don't work all that much but on the freeway with the bus in higher rpms they work very well.  Problem is with an automatic is is sometimes hard to keep it in higher rpm.
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« Reply #7 on: January 01, 2010, 06:45:38 AM »

Kwood, the 2 strokes don't have enough oil pressure at low rpms to make the Jake hold ,you need to down shift to keep the oil pressure up that is why I love my Stone/Bennett shifter just a filp of the switch


good luck
« Last Edit: January 01, 2010, 06:51:26 AM by luvrbus » Logged

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rv_safetyman
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« Reply #8 on: January 01, 2010, 08:22:59 AM »

Kwood and others, we need to separate out driving conditions.  On the flatter, open roads, there is no need to try to keep the RPM up for the Jakes.  The exception being that even there you want to make sure the engine RPM is not in the "lugging" range.  Unless your transmission control system is screwed up, that will probably not happen.

Where we need to take control of the transmission is when we really need the Jakes.  That would be on long downhill runs and on tight, twisty roads.  There it just make sense to take over control and keep the engine in the higher RPM ranges (say above 1700-1800 RPM).  On the real "hills" you want to keep the RPM even higher.  We are over 44K and I keep the Series 60 at 1800-2100 when the hills are steep.  When the engine frequently wants to go over 2100 in a given gear, you know that you need to slow down and drop one more gear. 

You really should not be touching the brakes very often in those conditions, so that you have them available if you really need them.  It really does not take long to get the brakes hot and when you do, you are probably in trouble.

Jim
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Jim Shepherd
Evergreen, CO
85 Eagle 10/Series 60/Eaton AutoShift 10 speed transmission
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« Reply #9 on: January 01, 2010, 08:38:00 AM »

Jim, that is not true in all case some of these older buses need all the help you can get to whoa it up even here in AZ and TX on flat ground. 
A lot of folks with the early 01 and 05 Eagles with crappy brakes from Eagle use the Jake's for assist in stopping on level ground. 
I for one before upgrading my brakes would have bought several cars without my Jake's in Houston or Phoenix


good luck
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« Reply #10 on: January 01, 2010, 08:55:37 AM »

Clifford, good point. 

Kind of a sad testimony about brake design in those coaches. 

At typical highway speed, the Jakes should be effective when you first let off.  However, you are then reliant on the transmission shifting down aggressively (to keep the RPM up).  Under critical conditions, you would probably not be able to control the transmission and handle the other panic functions.

I will be the first to make the observation that, if you have a bus with marginal brakes, you need to really be careful to keep the bus in a safe operating condition.  By that I mean good mechanical condition (emphasis on brake adjustment), and keeping the bus in a safe operating range from a driving condition (speed and spacing).  Then, I will be the first to say that I have not been as careful of a driver as I should be.  Also idiot drivers do not always allow you to be a safe driver Angry.

I suspect there will be folks who say that Jakes were never intended to augment the brakes under the conditions you describe.  Even with the fairly good Jakes on a Series 60, I don't count on them helping except on the downhill and twisty road conditions.

Not debating, just adding my thoughts (I sure don't want to pi$$ anyone off on the first day of the new decade Smiley> Wink

Jim
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Jim Shepherd
Evergreen, CO
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« Reply #11 on: January 01, 2010, 09:08:01 AM »

I recall one downgrade when I had the Jake brake on.  The guys in the back started yelling about using the brakes too much as they could smell burning brakes.  I yelled back that it wasn't us as I hadn't touched the brakes in several minutes.  It was some other vehicle next to us that was burning up their brakes.

I will admit it wasn't legal to use to use engine brakes on that grade, but I wasn't about to not use a safety device where it is most needed.  I wanted my service brakes nice and cool if I needed them.
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Brian Elfert - 1995 Dina Viaggio 1000 Series 60/B500 - 75% done but usable - Minneapolis, MN
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« Reply #12 on: January 01, 2010, 09:19:55 AM »

Belfert,

That brings up an interesting point.  One often sees local signs prohibiting engine brakes, but I was once told that a locality cannot ban the use of safety equipment in some states.  Does anyone know the truth about this?
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« Reply #13 on: January 01, 2010, 09:27:34 AM »

Lin, if you look at the signs closely some say all jakes prohibited and others say only non muffled jakes prohibited.  Smiley
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« Reply #14 on: January 01, 2010, 09:52:15 AM »

Jacobs Vehicle Systems has been very agressive about government entities not posting signs banning Jake Brakes.  Jake Brake is a registered trademark plus JVS believes it devalues their product.  JVS suggests the posting of signs that prohibit unmuffled engine brakes instead.

I have lots of signs prohibiting engine brakes, but I don't recall seeing one that only prohibited unmuffled engine brakes.  It seems that unmuffled engine brakes are the real reason for most of the complaints.
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Brian Elfert - 1995 Dina Viaggio 1000 Series 60/B500 - 75% done but usable - Minneapolis, MN
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« Reply #15 on: January 01, 2010, 09:54:51 AM »

I figure if I am ever cited for using Jakes in one of those towns I'll make the appearance and ask the judge if he would rather I had cold brakes or hot ones when his grand-daughter steps off the curb.  The ones that really bug me are the ones with the sign at the top of the hill and the short cycle traffic light right smack dab at the bottom of the hill before you really get into the town.  Not a soul around for miles and they expect me to ride my service brakes down the hill - I don't think so.
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« Reply #16 on: January 01, 2010, 10:07:12 AM »

I see the unmuffled signs about every where I travel now for a while you would see the NO JAKE BRAKE signs but haven't seen those lately.
I was told if you do see one call Jake and they will have it removed and FWIW no engine brakes are not for Jake only the PAC exhaust brake is a load critter also


good luck
« Last Edit: January 01, 2010, 10:10:32 AM by luvrbus » Logged

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« Reply #17 on: January 01, 2010, 10:08:08 AM »

Lin, i just tried to send you an email and a personal mail. Did you get either one?   damn computer!!!!
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1968 MCI 5A with 8V71 and Allison MT644 transmission.  Western USA
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« Reply #18 on: January 01, 2010, 10:11:05 AM »

Jake brakes turn the engine into an air compressor.  Hence the faster rpm the engine goes, the more horsepower it produces for braking.  On most 4 stroke engines, including the Series 60, 2300 rpm is the maximum recommended engine speed when using Jake brake.  2300rpm also applies to any 92 series (92 series should NEVER be taken above 2300rpm for any reason).  On 71 series, 2500rpm is allowed (unlike 92 series, 71 series many times were turned up to 2800rpm for more horsepower-but, still 2500rpm is the highest recommended).  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #19 on: January 01, 2010, 10:58:35 AM »

In comparing Jakes and Service Brakes, we need to be sure we are comparing apples to apples.

All things being equal, the service brakes will outperform the jakes in the slippery, because they have the grip of all the tires available, and are more closely modulated via the brake pedal.

The jakes get the benefit of only the 4 drive tires and whatever grip they can muster. The sudden action of a downshift during the deceleration can tear them loose.

Too many Transport Canada/NHTSA reports cite the retarder or engine brake as being involved in slippery road collisions.

How do you know that the brakes on your coach are all doing their fair share of the job?

If only one or two of your brakes are doing the work, linings are contaminated, linings are burned and crumbling, the relay valve is failing, wrong valving plumbed in by you or some previous owner, sticking valves, then you'll get slides from those couple of wheels in slippery conditions, and little deceleration.

Trouble is, under "normal" conditions, the little braking you have is enough to stop.

If we put our coaches onto a brake dynometer, I can guarantee many of us will not like the results, having brake positions that show good adjustment but do little gripping inside the drum to stop the coach.


happy coaching!
buswarrior

« Last Edit: January 01, 2010, 11:01:03 AM by buswarrior » Logged

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Eagle Andy
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« Reply #20 on: January 01, 2010, 12:10:45 PM »

All good points on the jakes ,  As someone who drives big heavy stuff everyday and this year in all kinds of road conditions , When Iam driving in wet conditions with temps above freezing I pretty much use my jake at will , That being said iam also awear of whats going on around me . In below freezing conditions Iam a little more cautious . Now when Iam appproching a down grade in winter conditions Iam grabbing grears alot sooner  and I usel my jake as needed , but not for very long I use my brakes alot more in those conditions. I know there are a lot of different thoughts on this Iam only shareing what I do , Its what Iam comfortable with So I guess all Iam saying is we all have are comfort  levels be aware of your conditoins and use your common sence . FWIW
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« Reply #21 on: January 01, 2010, 12:37:36 PM »

Using Allisons for braking is an expensive proposition since it generates so much heat and heat is the #1 enemy of AT.

Jakes don't heat the AT at all and the engine is designed for all this heat, in fact the engine needs a bit of heat when going down grade.

I never ever use an AT for retarding. Even service brakes are cheaper than ATs.

I, too, have experienced that burned service brake smell from another vehicle on the western Tehachapi down grade, sure scared me at first.

For what it's worth, my 4sp 4104 with 671 does a great job of retarding in 4th gear, it all depends on starting from the top at slow speed.
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PD4107-152
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« Reply #22 on: January 01, 2010, 12:43:57 PM »

I drive a MCI D3, S60, 7 speed manual for the hockey team. Great Jakes by the way. I use them pretty well all the time, except in town or if it is really icy. They really slow me down nicely when taking my foot off the pedal. I pretty well ignore the "no engine brakes" signs, driving downhill into town like is very common in BC. Mine aren't very loud with a good muffler anyway. I am of the same opinion as B.O.T.Norh on this issue. One of the coaching staff on board is a RCMP highway patrol, and he agrees with me. They usually don't bother enforcing those bylaws, as they would not stand up in court, against the safety factor. Really loud ones without a muffler is another matter. How about all the loud pipes on Harleys in the summer? The cops generally ignore that too around here. Although some bikers would argue that it is a safety issue...

Happy New Year to all you nuts by the way,

I don't post much, but I read the board every day,

JC
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JC
Invermere, BC
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buswarrior
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« Reply #23 on: January 01, 2010, 12:50:19 PM »

Those with proper mufflers have no need to worry about postings against engine brake use.

They are concerned with the ones who make lots of noise, and there are more than enough sound bylaws to deal with them.

Signs are put up by town councils to shut up the rate payers.

But, let's remember the Golden Rule as often as we can:

be courteous in someone else's neighbourhood.

happy coaching!
buswarrior
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« Reply #24 on: January 01, 2010, 03:54:53 PM »

All -


We have one of those signs coming into Fresburg SB on SR-41, it says "Truckers - limit engine brake usage".  Interesting wording on a yellow sign.

Now, here's an interesting bit of trivia, at least for here in Californication:

Black & White traffic signs are enforceable by the local gendarmes.

Yellow & Black traffic signs are advisory only, cannot be enforced by the militia.

So law enforcement cannot legally cite you here for using an engine brake based on a yellow advisory sign.

Might research in your locality?

FWIW & HTH. . .

 Wink

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RJ Long
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« Reply #25 on: January 01, 2010, 04:31:04 PM »

Here is a link to an article summarizing state regs for Jakes.  It seems that the key words are "indiscriminate use" and "un-muffled".   Notice Kansas seems to be the only state that bans there use for certain vehicles.  One would guess that they feel any use on their terrain is indiscriminate.

http://www.cga.ct.gov/2004/rpt/2004-R-0741.htm

I also found other articles which said that the the State of New York ruled that municipalities do not have the right to legislate about highway braking, and one that said that attorneys for the City of Glendale, Ca advised their city counsel that they did not have the right to pass engine brake laws.  Jacobs is active in opposing such laws claiming that the issue is really modified mufflers and not their product.  They say that highway police should just be enforcing existing muffler and noise laws.

I think that this comes down to a common sense and common courtesy issue.  If you are driving through a residential area, even on a freeway, that has a minimal grade--don't turn them on.  If safety is involved, you must use them.
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« Reply #26 on: January 01, 2010, 04:37:30 PM »

Oh, and for your listening enjoyment:

jake brake
(The video's owner prevents external embedding)
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« Reply #27 on: January 01, 2010, 04:50:03 PM »

A question on jakes and 740 allisons: does the transmission stay in lockup when the jakes are applied? and if so, how is this acclomplished? I would think that if it was in lockup there would be no heat buildup in the trans. I amasking because I am currently converting to an auto.   

Gerry
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belfert
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« Reply #28 on: January 01, 2010, 05:53:11 PM »

A question on jakes and 740 allisons: does the transmission stay in lockup when the jakes are applied? and if so, how is this acclomplished? I would think that if it was in lockup there would be no heat buildup in the trans. I amasking because I am currently converting to an auto.   

I believe the other poster is referring to a transmission retarder, not Jake Brakes.
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Brian Elfert - 1995 Dina Viaggio 1000 Series 60/B500 - 75% done but usable - Minneapolis, MN
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« Reply #29 on: January 01, 2010, 07:42:45 PM »

If you have a normal HT740, it usually locks up in the upper end of 2nd gear and stays locked up all the way to 4th.  When using the Jake brake, the transmission will stay in lockup and down shift at low rpm's till it falls out of torque converter lockup at around 20mph.  You can keep the engine rpm higher by down shifting manually at an earlier time-but don't allow the engine to go above 2400rpm-because the transmission will upshift to protect the engine even if you have it locked in a lower gear selection.  You can also get lockup in 1st by pulling it down into 1st, but many times will drop out of lock up still at around 20mpg.  On the HT740, you can have a solenoid installed that gives you a manual lockup switch on the dash to keep it locked up whenever you want-but then you have to watch that too since you can stall the engine if you don't release it in time.

No matter what your throttle position is on the Allison transmissions, there is always going to be heat to dissipate through the transmission cooler since Allisons produce heat just with the natural dragging of the clutches through the transmission fluid.  About to the tune of 20hp worth of drag more then a manual transmission-and that's directly from Allison.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #30 on: January 02, 2010, 08:41:49 AM »

I have the Jake manual and read it but must admit that I am not getting a bit confused on how to use them effectively.  I have an MC9 with 8v71, Allison automatic, Jakes, and a manual foot switch to activate the Jakes when I want (there is also a dash switch with off/low/hi). 

Any recommendations on how to best use these and not hurt the transmission/brakes/engine?

Thanks,
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« Reply #31 on: January 02, 2010, 09:07:15 AM »

The engine brake can be thought of as increasing the effect of regular engine compression.
It is another variable, or tool, that you can choose to throw into the mix of slowing down.

So, to slow down, sometimes, you just lift your foot off the throttle.

Sometimes you gear down, to increase the effect of engine compression.

Turning the Jake on will increase the effect of engine compression choices.

So, you use it when you want these effects to be stronger, with the added choice of low or high on the Jake controls. With some practice, you will be able to manipulate all these variables to get the desired slowing, or holding speed on a downhill.

HTH
happy coaching!
buswarrior
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« Reply #32 on: January 02, 2010, 09:59:18 AM »

My Jake manual says I can leave the jake on all the time, especially for in-town driving to reduce the need for use of the service brakes, the only thing it recommends against is leaving the jake on after shutting down the engine. When I first brought mine home, the toggle was broken off in the high position and made for some hard starting. Didn't know enough until reading the advice here about wiring the jake to correctly repair it. (Thanks BW for that). Will
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« Reply #33 on: January 02, 2010, 10:32:16 AM »

Jim, that is not true in all case some of these older buses need all the help you can get to whoa it up even here in AZ and TX on flat ground. 
A lot of folks with the early 01 and 05 Eagles with crappy brakes from Eagle use the Jake's for assist in stopping on level ground. 
I for one before upgrading my brakes would have bought several cars without my Jake's in Houston or Phoenix


good luck

What are some of the differences between the different brake designs?  (chamber size, drum width, etc)
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« Reply #34 on: January 02, 2010, 10:44:58 AM »

Dave, it was the width on older Eagles with the std 4 inch on the front and tag or boggie, and with 6 inch on the drivers not enough shoes or drum I now have 6 inch on the front and boggie with 9 1/2 inch on the drivers big difference in stopping now.  



good luck
« Last Edit: January 02, 2010, 11:16:08 AM by luvrbus » Logged

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« Reply #35 on: January 02, 2010, 10:46:56 AM »

Drums and linings smaller than modern sensibilities consider adequate.

Increasing chamber size isn't very effective, it's the surface area of your brake friction materials that make the difference.

Small surface area heats up sooner and has less "traction" than larger surface area.

happy coaching!
buswarrior
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« Reply #36 on: January 02, 2010, 11:07:02 AM »

Drums and linings smaller than modern sensibilities consider adequate.

Increasing chamber size isn't very effective, it's the surface area of your brake friction materials that make the difference.

Small surface area heats up sooner and has less "traction" than larger surface area.

happy coaching!
buswarrior

Thanks, I wasn't suggesting that chamber sizes would fix things, just fishing for what the differences were. Clifford answered that, makes all the sense in the world.
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buswarrior
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'75 MC8 8V71 HT740




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« Reply #37 on: January 02, 2010, 11:18:55 AM »

I was typing while you were, I was cutting that concept off at the pass, not commenting on your good stuff!

Some folks mistakenly think larger chambers will be their salvation.

happy coaching!
buswarrior
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Frozen North, Greater Toronto Area
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