Home » Public Forums » GMCnet » Rear wheel lock up (survey of GMCer who have experienced Rear wheel lock-up)
| Rear wheel lock up [message #273847] |
Mon, 16 March 2015 21:00  |
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John Sharpe
Messages: 71
Registered: February 2006
Location: Porter, TX
Karma: 0
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I have had heard descriptions of flat spotting the rears during panic stops. My question to those who have experienced this: Were the only wheels loosing traction the rear axle? I have had my GMC since 2006 and it was incapable of locking up any wheels except on wet roads. After installing a Bob Stone hydro-boost on my coach, the rear stock drum brakes do lock the rear axle as well as the front 80mm calipers. The stock mid axle drum brakes do not seem to lock. However, there is significant deceleration going on. The front end actually nose dives. I was toying with the idea of replacing the mid axle wheel cylinders with 1 1/8" cylinders and the rear axle with 7/8" cylinders to better balance the braking. So again, have you experience front and rear axle wheel lock-up or only rear wheel lockup?
John Sharpe
Porter, TX
78 Eleganza II, TBI
40 Ford Panel, TPI
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| Re: Rear wheel lock up [message #273851 is a reply to message #273847] |
Mon, 16 March 2015 21:23  |
C Boyd
Messages: 2629
Registered: April 2006
Karma: 18
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Yes I experienced rear axel lock up, specially when pulling a trailer without brakes. I had all new stock brakes carbon metallic pads and shoes. Good brakes except would slide rear axle, worse when wet. I installed the drum brake reaction arm kit and a sensitized booster from Mr. Lenzi and now I have very good brakes and no sliding except when wet. Totally different feel when stopping. The rear squats. I really have not tested the system as to a sevier panic stop and hope I never have to.
John Sharpe wrote on Mon, 16 March 2015 22:00I have had heard descriptions of flat spotting the rears during panic stops. My question to those who have experienced this: Were the only wheels loosing traction the rear axle? I have had my GMC since 2006 and it was incapable of locking up any wheels except on wet roads. After installing a Bob Stone hydro-boost on my coach, the rear stock drum brakes do lock the rear axle as well as the front 80mm calipers. The stock mid axle drum brakes do not seem to lock. However, there is significant deceleration going on. The front end actually nose dives. I was toying with the idea of replacing the mid axle wheel cylinders with 1 1/8" cylinders and the rear axle with 7/8" cylinders to better balance the braking. So again, have you experience front and rear axle wheel lock-up or only rear wheel lockup?
C. Boyd
76 Crestmont
East Tennessee
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| Re: [GMCnet] Rear wheel lock up [message #273852 is a reply to message #273847] |
Mon, 16 March 2015 21:19 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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John,
After JR, Bobby Moore, and I installed 6 wheel disc brakes on my 23', we
rode around the block in Bobby's residential neighborhood. I locked up the
rear brakes at 30 mph or so. I had that problem until I installed Manny
Brakes a couple of years ago, except for the 5+ years I drove with NO rear
wheel brakes.
I've never been able to lock any middle or front wheel, even with the big
1-Ton discs ('though I must admit I haven't really tried with those).
With nothing but intuition & what I've heard of REAL old-timers doing, I'd
say your cylinder changes do make sense.
Ken
On Mon, Mar 16, 2015 at 10:00 PM, John Sharpe
wrote:
> I have had heard descriptions of flat spotting the rears during panic
> stops. My question to those who have experienced this: Were the only wheels
> loosing traction the rear axle? I have had my GMC since 2006 and it was
> incapable of locking up any wheels except on wet roads. After installing a
> Bob Stone hydro-boost on my coach, the rear stock drum brakes do lock the
> rear axle as well as the front 80mm calipers. The stock mid axle drum
> brakes do not seem to lock. However, there is significant deceleration
> going on. The front end actually nose dives. I was toying with the idea of
> replacing the mid axle wheel cylinders with 1 1/8" cylinders and the rear
> axle with 7/8" cylinders to better balance the braking. So again, have you
> experience front and rear axle wheel lock-up or only rear wheel lockup?
> --
>
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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: Rear wheel lock up [message #273854 is a reply to message #273847] |
Mon, 16 March 2015 21:31 |
kerry pinkerton
Messages: 2565
Registered: July 2012
Location: Harvest, Al
Karma: 15
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I slid my rears once on a downhill approach to an intersection when a light changed. I was pretty impressed because my brakes really sucked. After I installed the Manny Brakes, I have not slid the brakes but on gravel our tests show that the mids lock up first and the rear are ALMOST locked up.
With the increased PSI available with the Hydroboost, when the nose dives, the rear is going to 'pole vault' and the rears slide in a heavy stop. Reaction arms will solve that either disk or drums.
I want to check out your Stone brakes at Patterson.
Kerry Pinkerton - North Alabama
Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L
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| Re: Rear wheel lock up [message #273856 is a reply to message #273847] |
Mon, 16 March 2015 22:28 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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When I got my coach, it had adequate stock brakes. With 66,000 miles on it, I suspect the pads and shoes had been replaced, but the brakes worked well. I did have a few incidents of sliding the rear wheels when a light suddenly changed. I figured since I was driving a 40 year old, 12.000 pound motorhome among modern cars and trucks with modern ABS brakes, I'd better upgrade. After driving Rick Flanagan's test coach, at a Western States rally, I knew I needed to have the Chuck Aulgur reaction arm, disc brake system from Jim K. It was THE most expensive upgrade to date, but it has saved me from a certain accident several times since. I still am in the habit of planning my stops, but I really don't need to. My coach has six, very effective brakes which is two more than most other vehicles on the road. In my opinion, one of the reaction arm systems would be the best safety upgrade anyone can make to one of these coaches
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: Rear wheel lock up [message #273858 is a reply to message #273847] |
Tue, 17 March 2015 00:39 |
George Beckman
Messages: 1085
Registered: October 2008
Location: Colfax, CA
Karma: 11
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John Sharpe wrote on Mon, 16 March 2015 19:00I have had heard descriptions of flat spotting the rears during panic stops. My question to those who have experienced this: Were the only wheels loosing traction the rear axle?
John,
Our first coach was a '23 with those steel sided Goodyears. I locked up a left back tire ( drum brakes) and that sucker thumped for the next 20,000 miles. Drove me nuts.
'74 Eleganza, SE, Howell + EBL
Best Wishes,
George
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| Re: Rear wheel lock up [message #273882 is a reply to message #273847] |
Tue, 17 March 2015 11:53 |
bwevers
Messages: 597
Registered: October 2010
Location: San Jose
Karma: 5
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Senior Member |
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My two rear wheels lock up very easily, especially on a hot day on an old asphalt road. Tire smoke billowing out...
I can lock the inside front wheel on a sharp turn (one ton brakes).
Bill Wevers GMC49ers, GMC Western States
1975 Glenbrook - Manny Powerdrive, OneTon
455 F Block, G heads
San Jose
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| Re: Rear wheel lock up [message #273912 is a reply to message #273847] |
Tue, 17 March 2015 18:51 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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Before I fitted the floating backing plates and arms, my 23' would skid the rears under light to moderate braking. I squared the rears in a hard stop in Florida - ask Robin Hood about that set of tires. With the Pryor designed torque system, they can be skidded but only in a panic stop. This modification is a desirable mod, it enhances safety substantially.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: Rear wheel lock up [message #273926 is a reply to message #273847] |
Tue, 17 March 2015 22:38 |
bhayes
Messages: 263
Registered: March 2010
Karma: 1
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Last fall, some college students pulled out in front of me in a tiny Honda while I was rolling along at about 30 MPH. I locked up the rears, which resulted in some pretty impressive skid marks and smoke. I have 80 mm calipers on the front, stock drums on the mids and rear, and stock master cylinder. No noticeable squaring of the Transforce tires.
I don't think I would have enjoyed seeing what a GMC vs. Honda Civic mashup would have looked like.
Bryan Hayes
'76 Eleganza II
Salt Lake City, Utah
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