Home » Public Forums » GMCnet » Toad brake issue (Flat spotted tires)
| Toad brake issue [message #265750] |
Sun, 09 November 2014 21:41  |
kerry pinkerton
Messages: 2565
Registered: July 2012
Location: Harvest, Al
Karma: 15
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My cousin came in for a visit in his (to him) new diesel pusher. He tows a Lincoln suv and when he came in he told me that he had run up on the exit and gotten on the brakes pretty hard not to miss it. He heard some noise and looked back and saw a huge cloud of smoke. After he got off the interstate, he pulled over and checked out his toad. Both the rear tires were flatspotted.
When he got here, we looked at it and in one spot, the tires had at least an 1/8th ground off in one spot. I've never seen anything like it.
He was going to get new tires anyway before winter so he just got 4 new Michelins here.
He purchased a new "Brake Buddy" brand system and the dealer he got the coach from installed a new tow plate on the Lincoln. I suggested he had the sensitivity set WAY too high and he agreed. The brake buddy is a box that sits in the floor in front of the seat. It has a onboard compressor and presses on the brake pedal. You are supposed to press a button on the box 5 times to cause it to stroke the toad brake pedal down and dump all the vacuum from the booster.
A few hours later, he said he had stopped just up the road at a truck stop and had started the ignition on the Lincoln for a few minutes (like the manual says). We quickly realized what had happened. When he started the engine, it pulled 18 inches of vacuum in the booster. As he was pulling out, he MAY not have even touched the brake before he got on the interstate. When he did the hard stop a few miles later, the brake buddy did it's normal pedal press of X pounds on the pedal but since the booster still had vacuum in it, the effect was MUCH amplified and locked up the tires. While his Brake Buddy might have been set a bit too much, the PROBLEM was literally amplified because the booster had vacuum in it.
As I got thinking about it, this is an issue for most of the brake systems on the market. I use a Ready Brake which is a mechanical system that pulls the brake cable proportionally to how hard the coach is stopping. I have never manually dumped the vacuum before pulling out and because I've usually started the Saturn while hooking up, the booster is always got vacuum in it. I guess the reason I've never noticed it is because I probably ease on the brakes a few times before I ever have a HARD stop. Plus, I don't have it set very tight.
Being relatively new to all this, it's quite a sobering piece of knowledge. Has anyone else ever run into this? Or is it common knowledge that I've just missed in drinking from the GMC firehose fount of knowledge?
Kerry Pinkerton - North Alabama
Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L
[Updated on: Sun, 09 November 2014 21:41] Report message to a moderator |
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| Re: Toad brake issue [message #265752 is a reply to message #265750] |
Sun, 09 November 2014 23:23  |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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You are correct if the toad had a good vacuum in the power booster the brake buddy would have been way too much. Ditto for a roadmaster and a blue ox. I would suggest he press on the brake peddle a couple of times before he takes off or an early hard stop would likely be excessive . Wouldn't anti lock breaks keep the tires from locking up though?
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: [GMCnet] Toad brake issue [message #265755 is a reply to message #265750] |
Sun, 09 November 2014 23:58 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Kerry,
You've probably got most of the answer right there. But there's one other
thing to check: If the tow bar is too high at the coach, it with cause the
toad to nosedive, lightening the rear wheels. Of course it also raises the
rear of the coach, increasing the possibility there. All disregarding
which has the "better" brakes, of course. :-)
Ken H.
On Sun, Nov 9, 2014 at 10:41 PM, Kerry Pinkerton
wrote:
> My cousin came in for a visit in his (to him) new diesel pusher. He tows
> a Lincoln suv and when he came in he told me that he had run up on the
> exit
> and gotten on the brakes pretty hard no to miss it. He heard some noise
> and looked back and saw a huge cloud of smoke. After he got off the
> interstate, he pulled over and checked out his toad. Both the rear tires
> were flatspotted.
>
> When he got here, we looked at it and in one spot, the tires had at least
> an 1/8th ground off in one spot. I've never seen anything like it.
>
> He was going to get new tires anyway before winter so he just got 4 new
> Michelins here.
>
> He purchased a new "Brake Buddy" brand system and the dealer he got the
> coach from installed a new tow plate on the Lincoln. I suggested he had the
> sensitivity set WAY too high and he agreed. The brake buddy is a box
> that sits in the floor in front of the seat. It has a onboard compressor
> and
> presses on the brake pedal. You are supposed to press a button on the
> box 5 times to cause it to stroke the toad brake pedal down and dump all the
> vacuum from the booster.
>
> A few hours later, he said he had stopped just up the road at a truck stop
> and had started the ignition on the Lincoln for a few minutes (like the
> manual says). We quickly realized what had happened. When he started
> the engine, it pulled 18 inches of vacuum in the booster. As he was pulling
> out, he MAY not have even touched the brake before he got on the
> interstate. When he did the hard stop a few miles later, the brake buddy
> did it's
> normal pedal press of X pounds on the pedal but since the booster still
> had vacuum in it, the effect was MUCH amplified and locked up the tires.
> While his Brake Buddy might have been set a bit too much, the PROBLEM was
> literally amplified because the booster had vacuum in it.
>
> As I got thinking about it, this is an issue for most of the brake systems
> on the market. I use a Ready Brake which is a mechanical system that pulls
> the brake cable proportionally to how hard the coach is stopping. I have
> never manually dumped the vacuum before pulling out and because I've usually
> started the Saturn while hooking up, the booster is always got vacuum in
> it. I guess the reason I've never noticed it is because I probably ease on
> the brakes a few times before I ever have a HARD stop. Plus, I don't
> have it set very tight.
>
> Being relatively new to all this, it's quite a sobering piece of
> knowledge. Has anyone else ever run into this? Or is it common knowledge
> that I've
> just missed in drinking from the GMC firehose fount of knowledge?
> --
> Kerry Pinkerton
>
> North Alabama, near Huntsville,
>
> 77 Eleganza II, "The Lady", 403CI, Manny Brakes, 1 ton, tranny also a 76
> Eleganza to be re-bodied as an Art Deco car hauler
> _______________________________________________
> GMCnet mailing list
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: Toad brake issue [message #265760 is a reply to message #265752] |
Mon, 10 November 2014 05:28 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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I think you need the ignition turned on for ABS to work.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Toad brake issue [message #265762 is a reply to message #265750] |
Mon, 10 November 2014 07:16 |
kerry pinkerton
Messages: 2565
Registered: July 2012
Location: Harvest, Al
Karma: 15
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Senior Member |
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So this is important with ANY toad brake system on ANY coach? I just have not heard or observed any of us doing this. I certainly will in the future.
Upon reflection, I might have experienced this a bit myself. When Ken Henderson and I were headed up to the GMCMI rally, I pulled out from my cousin's place (same cousin) there is a height difference in the main road and the side road . As the rear of the coach went and I turned and the Saturn was still climbing the hill, I felt a pretty significant pull back. I assumed the unusual orientation of both vehicles pulled the Ready Brake cable and just set the brake for a moment. I still believe that was what happened but also that because there was vacuum in the booster, it set the brakes harder than normal.
As far as the tow bar being level, I believe that is more important on our coaches and other smaller motorhomes than his 32000 lb beast. It's really important on the Ready Brake because you don't want the mechanical mechanism to bind which was a problem with the early versions.
Kerry Pinkerton - North Alabama
Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L
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| Re: Toad brake issue [message #265765 is a reply to message #265762] |
Mon, 10 November 2014 08:57 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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kerry pinkerton wrote on Mon, 10 November 2014 08:16So this is important with ANY toad brake system on ANY coach? I just have not heard or observed any of us doing this. I certainly will in the future.
Upon reflection, I might have experienced this a bit myself. When Ken Henderson and I were headed up to the GMCMI rally, I pulled out from my cousin's place (same cousin) there is a height difference in the main road and the side road . As the rear of the coach went and I turned and the Saturn was still climbing the hill, I felt a pretty significant pull back. I assumed the unusual orientation of both vehicles pulled the Ready Brake cable and just set the brake for a moment. I still believe that was what happened but also that because there was vacuum in the booster, it set the brakes harder than normal.
As far as the tow bar being level, I believe that is more important on our coaches and other smaller motorhomes than his 32000 lb beast. It's really important on the Ready Brake because you don't want the mechanical mechanism to bind which was a problem with the early versions.
Kerry,
There is a lot more going on with all these systems than most people will intuitively gather....
Your Ready Brake is Strickly Mechanical and neither the presence or absence of vacuum or the attitude (physical, not emotional) will matter. All that matters to it is if the towd is catching the tow-er(?).
All the others that sit on the floor (except KenH's simple brake) use a pendulum accelerometer to decide if/how much towd brake is required. These come in lots of different flavors and I will not try to break them down here.
An interesting unit by all standards is the USGear brake that uses the vacuum assist and a flexible cable to pull the brake cable. The sensing accelerometer in these mounts on the tow vehicle instrument panel.
Now, a distinct problem for the all the floor placed "pendulum in the toad units" is that the whole system is now sensitive to the the towd attitude (see above). While this does not matter most of the time, if cousin's towbar had much angle at all, it could significantly affect to application of the towd brakes. So, if you are using a "floor" brake unit, start out with the tow bar as close to parallel with the pavement as you can get it. Actually being truly horizontal is not that big a deal, but the towd needs to follow the coach in a level fashion.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] Toad brake issue [message #265768 is a reply to message #265765] |
Mon, 10 November 2014 09:34 |
Arthur Mansfield
Messages: 290
Registered: April 2010
Karma: 0
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Senior Member |
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Thanks for all the info on brake systems. I use a brake buddy and never have thought of some of the issues. The only issue I have run into is I ran the towd battery down.
If I understood the description below as to how a brake buddy works it will not work the same going up or down a hill. Going down a hill the brake may either come on from the hill or will change the ratio of braking proportional to how much breaking the coach has. Now if it use accelerometer then the affect on hill will not be significant when climbing or going down a hill. If it uses a pendulum then it would be affected by a hill. Today I would expect then too use accelerometers.
Art & Doris
76 EL
Decatur AL
On Nov 10, 2014, at 8:57 AM, Matt Colie wrote:
> kerry pinkerton wrote on Mon, 10 November 2014 08:16
>> So this is important with ANY toad brake system on ANY coach? I just have not heard or observed any of us doing this. I certainly will in the
>> future.
>>
>> Upon reflection, I might have experienced this a bit myself. When Ken Henderson and I were headed up to the GMCMI rally, I pulled out from my
>> cousin's place (same cousin) there is a height difference in the main road and the side road . As the rear of the coach went and I turned and the
>> Saturn was still climbing the hill, I felt a pretty significant pull back. I assumed the unusual orientation of both vehicles pulled the Ready
>> Brake cable and just set the brake for a moment. I still believe that was what happened but also that because there was vacuum in the booster, it
>> set the brakes harder than normal.
>>
>> As far as the tow bar being level, I believe that is more important on our coaches and other smaller motorhomes than his 32000 lb beast. It's
>> really important on the Ready Brake because you don't want the mechanical mechanism to bind which was a problem with the early versions.
>
> Kerry,
>
> There is a lot more going on with all these systems than most people will intuitively gather....
> Your Ready Brake is Strickly Mechanical and neither the presence or absence of vacuum or the attitude (physical, not emotional) will matter. All that
> matters to it is if the towd is catching the tow-er(?).
>
> All the others that sit on the floor (except KenH's simple brake) use a pendulum accelerometer to decide if/how much towd brake is required. These
> come in lots of different flavors and I will not try to break them down here.
>
> An interesting unit by all standards is the USGear brake that uses the vacuum assist and a flexible cable to pull the brake cable. The sensing
> accelerometer in these mounts on the tow vehicle instrument panel.
>
> Now, a distinct problem for the all the floor placed "pendulum in the toad units" is that the whole system is now sensitive to the the towd attitude
> (see above). While this does not matter most of the time, if cousin's towbar had much angle at all, it could significantly affect to application of
> the towd brakes. So, if you are using a "floor" brake unit, start out with the tow bar as close to parallel with the pavement as you can get it.
> Actually being truly horizontal is not that big a deal, but the towd needs to follow the coach in a level fashion.
>
> Matt
> --
> Matt & Mary Colie - Members GMCMI, GMCES
> '73 Glacier 23 - Still Loving OE Rear Drum Brake with Applied Control Arms
> SE Michigan - Twixt A2 and Detroit
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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| Re: Toad brake issue [message #265769 is a reply to message #265750] |
Mon, 10 November 2014 09:44 |
kerry pinkerton
Messages: 2565
Registered: July 2012
Location: Harvest, Al
Karma: 15
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Senior Member |
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I don't understand Matt? If the toad brake is set to push/pull x lbs on the pedal, won't any vacuum in the booster cause that to be amplified just like it is when we push the pedal driving down the road?
The reason my ready brake engaged is because the cable gets bound up a bit by the structure of the tow bar when their is an angle between the coach and the toad. I tested that to my satisfaction. It will be a VERY rare occurance and since it only lasts a couple feet until the toad gets to the same road, it's not an issue.
Kerry Pinkerton - North Alabama
Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L
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| Re: Toad brake issue [message #265770 is a reply to message #265769] |
Mon, 10 November 2014 10:08 |
midlf
Messages: 2212
Registered: July 2007
Location: SE Wisc. (Palmyra)
Karma: 1
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Senior Member |
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kerry pinkerton wrote on Mon, 10 November 2014 09:44I don't understand Matt? If the toad brake is set to push/pull x lbs on the pedal, won't any vacuum in the booster cause that to be amplified just like it is when we push the pedal driving down the road?
The reason my ready brake engaged is because the cable gets bound up a bit by the structure of the tow bar when their is an angle between the coach and the toad. I tested that to my satisfaction. It will be a VERY rare occurance and since it only lasts a couple feet until the toad gets to the same road, it's not an issue.
Kerry - unlike the brake buddy and similar systems that rely on deceleration, the ready brake actuates by how hard the toad is pushing on the GMC. The difference in that "push" with or without vacuum is just the difference in force on the pedal. I doubt if the difference in braking "push" is even noticeable in the GMC. In any event the ready brake cannot lockup the toad brakes. (While it can but only if the GMC can stop in a significantly shorter distance than the toad, unlikely). So why can't ready brake lockup the toad brakes? At lockup the toad would be pulling on the GMC, not pushing, and a pull on the towbar is what releases the ready brake system.
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI
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| Re: Toad brake issue [message #265788 is a reply to message #265770] |
Mon, 10 November 2014 12:23 |
kerry pinkerton
Messages: 2565
Registered: July 2012
Location: Harvest, Al
Karma: 15
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Senior Member |
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midlf wrote on Mon, 10 November 2014 10:08kerry pinkerton wrote on Mon, 10 November 2014 09:44I don't understand Matt? If the toad brake is set to push/pull x lbs on the pedal, won't any vacuum in the booster cause that to be amplified just like it is when we push the pedal driving down the road?
The reason my ready brake engaged is because the cable gets bound up a bit by the structure of the tow bar when their is an angle between the coach and the toad. I tested that to my satisfaction. It will be a VERY rare occurance and since it only lasts a couple feet until the toad gets to the same road, it's not an issue.
Kerry - unlike the brake buddy and similar systems that rely on deceleration, the ready brake actuates by how hard the toad is pushing on the GMC. The difference in that "push" with or without vacuum is just the difference in force on the pedal. I doubt if the difference in braking "push" is even noticeable in the GMC. In any event the ready brake cannot lockup the toad brakes. (While it can but only if the GMC can stop in a significantly shorter distance than the toad, unlikely). So why can't ready brake lockup the toad brakes? At lockup the toad would be pulling on the GMC, not pushing, and a pull on the towbar is what releases the ready brake system.
Ok, I'll buy that Steve but how about all the other break systems out there. Shouldn't they dump vacuum before heading out just in case their first break application is a hard stop from speed?
The break buddy actually says to press the test button 5 times to do just that. What my cousin forgot and wasn't in the instructions was that you need to do that every time you start the car while hooked up.
Kerry Pinkerton - North Alabama
Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L
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| Re: Toad brake issue [message #265793 is a reply to message #265750] |
Mon, 10 November 2014 12:51 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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I had a similar experience with my Brake buddy a while back. We were on a trip from Tucson to San Antonio, towing our '03 Tracker, equipped with a Brake Buddy. The first night, we parked in front of Hal K's business at the Las Cruces Airport, and continued from there to Ft Stockton, TX by way of Carlsbad Caverns. I had not run the Tracker the whole distance and decided to start it and get a fresh charge in the battery while camped in Ft Stockton.
The next morning, we proceeded on to Del Rio, making several stops in between. I have my Brake Buddy sensitivity set somewhat low due to the excellent Chuck Aulgur reaction arm and six wheel disc brake system I have on the coach, and all the stops were of a gradual nature...until I had to make a sudden stop, in traffic, in Del Rio. The brakes on the tracker locked up, smoking the tires and making a bunch of noise. It didn't take me long to realize that I had forgotten to relieve the vacuum on the brake booster when I shut down the Tracker the night before.
Freaked the wife out for a second until I had a chance to explain the situation to her and assure her I wouldn't make that mistake again. If I remember correctly, the instructions that came with my Brake Buddy say to pump the brakes at least five times after shutting down the towed vehicle. Pressing the test button would accomplish the same thing, but put unnecessary wear on the Brake Buddy. The point is to drain off that Vacuum before towing the towed.
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member
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| Re: Toad brake issue [message #265797 is a reply to message #265788] |
Mon, 10 November 2014 14:38 |
midlf
Messages: 2212
Registered: July 2007
Location: SE Wisc. (Palmyra)
Karma: 1
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Senior Member |
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kerry pinkerton wrote on Mon, 10 November 2014 12:23
Ok, I'll buy that Steve but how about all the other break systems out there. Shouldn't they dump vacuum before heading out just in case their first break application is a hard stop from speed?
The break buddy actually says to press the test button 5 times to do just that. What my cousin forgot and wasn't in the instructions was that you need to do that every time you start the car while hooked up.
Yes - all others need to follow the specific directions for that unit. Some systems have an aux vac pump. The sensitivity on those would be set up with the vacuum on.
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI
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