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Tire temps? Anyone else?
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dkarnath
Posted 2017-09-27 11:11 AM (#5008)
Subject: Tire temps? Anyone else?


Location: Medford, OR
(204.10.247.1)
Has anyone checked their tire temps with an infrared gun like me? I've been out a few times this year, usually, and unfortunately the ambient outside temps were in the high 90's and even 100 degrees on travel days. HOT. I run the original 17" bias 8 ply tires like a lot of other owners out there...

70 psi in the rears, temps averaged 145 degrees.
60 psi in the steers, temps averaged 155 degrees.

#850 rolls incredibly smooth (like a caddy) when cruising down the highway at 60 mph. That's even with 20-25?? year old shocks.

Now, the reason I pulled the temp gun out on my last couple trips, was because of a stupid thing I did (I'll explain)...My first trip of the season, around June, I was not liking my brake feel, they were unusually stiff/fading/unresponsive as I approached a stop sign? Hmm..AND they were pulling ever so slightly to the right...(I completely rebuilt all the hydraulic system for the brakes going on four years ago this month, but 98% of the last four years, 850 sat in the driveway as I fixed all the other things getting it ready for the road).

S000...on this first trip of the year, after I got to the RV park, I checked the brake fluid in the MC, and the reservoir for the front brakes was a touch low, now I know I have a leak somewhere, but don't see any signs of one....I figured that maybe I'll adjust them up a bit tighter for the drive home? Couldn't be anything else...Right? (I tell myself in denile), so on to traveling back home, probably a 100 mile jaunt, I stopped just before the only down grade I had to deal with, 6% for 8-9 miles, about 30 miles from home, and jacked up the front end and checked brake adjustment, well I didn't find either brake out of adjustment? They were actually adjusted up pretty tight, and "maybe" I clicked them and click tighter??? (dumb a$$ move)......so right then and there I knew it was time to pull wheels and do a visual on the brakes...BUT I got to get her home first! Everything was really hot under the coach, the rear brakes seemed a bit hot too, it was 98 degrees out too...F'n hot. I didn't try and adjust them because I could tell they were already adjusted up pretty tight...too tight. I cruised down the 6% grade with ease...only had to touch the brakes two maybe three times and maintained a nice 50-53 mph's...all good I thought..I had to make a couple turns at some stop signs etc, and I began to smell brake? The pulling to the right was getting more pronounced too...I'd roll up to stop sign and to really press hard on the pedal before she would stop...(I knew 850 wasn't going to leave the driveway until I found the problem). So I parked 850 in front of my house, left the engine running, I had to move a car out of my driveway before I could back 850 into it's parking spot, well as I was getting the keys so I could move the car, I heard Pssssssshhhhhhhhhhh! I thought "What the hell was that???" I looked out to where 850 was setting, and noticed the front end was practically sitting on the ground!! Holy $hit! one of the front tires just blew! Never in my life had I seen that. A tire blow just setting idle, after you just parked it. Well I got the jack, and rolled out a spare wheel/tire combo I have from behind the shop, jack it up expecting to find a bolt or something that maybe I parked on top of? After getting the wheel off the ground, I could barely turn the wheel...I could smell strong brake smell, and low and behold NO bolt or anything on the exterior of the tire that I could see. I put the spare on and backed 850 in the driveway, I was wearing thick leather gloves when I changed the tire, and I rolled the flat tire into the back yard, when I took the leather gloves off, grabbed the flat tire to move it out of my way, and DAM!! It was smoking hot!! I knew right their, that I eff'd up on adjusting these brakes, over compensating for different internal brake problem that it REALLY has, and I created a ton of brake drag and HEAT, I will never know if the hot ambient 105 degree at my house, heat soaked the front hot wheel/brake while it sat there? or if it would of blown driving down the road? I think it heat soaked. The rolling wind cooled it just enough to stay afloat... So anyway I pulled that brake apart and found the brake wheel cylinders pistons were corroded and sticking. I rebuilt both steer axle brakes, the front right was the leaker. Soooo remembering an old thread written by Lesly R.I.P, I went back and searched the archives and found what he had wrote about brake adjustment on the FMC, FIVE clicks out!! I had mine 2 maybe 3 out, TOO TIGHT, like I said, over compensating for another issue.

So, I wasn't going to tell anyone this (because of my stupidity on this issue), But I want others to maybe think twice about "tightening" up them brakes to "maybe get a little more out of them"...

AND before anyone says anything about "That wasn't safe to drive" or "I'm glad I wasn't on the road when you were" blah blah blah...
I was born and raised in the heavy equipment transportation world, I've driven almost everything HEAVY you can imagine, regularly pounded down the big highways, back roads, steep logging roads, high upon cliffs, next to ponds and rivers, your back yard....you name it.... in 105 THOUSAND pound monsters..I'm very educated on safe distance driving and being aware of my surroundings, and I'm not afraid to drive anything. With or without brakes, or even without a clutch cable at times...Sometimes you got to reach down and pull the throttle pedal back up because it starts sticking??? You get the point...

I didn't spend a ton of time editing this, I hope it reads ok.

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BigRabbitMan
Posted 2017-09-27 11:24 AM (#5009 - in reply to #5008)
Subject: Re: Tire temps? Anyone else?



Location: Cottage Grove, OR
(97.94.227.253)
Thank you for the detailed description and post. It will be helpful for some others at some point in time.
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5Dollar
Posted 2017-09-27 12:56 PM (#5012 - in reply to #5009)
Subject: Re: Tire temps? Anyone else?


Location: Bethune, SC
(204.116.151.110)
I thought the proper brake adjustment was all out. Then six clicks back. Is this correct?

Henry
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hemi354az
Posted 2017-09-27 4:38 PM (#5013 - in reply to #5012)
Subject: Re: Tire temps? Anyone else?


Location: Scottsdale, Aridzona
(24.251.160.88)
There is no "magic" number of clicks back. Please understand how drum brakes are adjusted. After service (drums, shoes, springs, cylinders, etc) the shoes are NOT "centered" in the drum. So . . . they are mechanically adjusted with a star wheel (that has a little notched leaf spring that sometimes "clicks" as it goes into the next cut of the star wheel - hence the term 2 "clicks", 3 "clicks", etc). They are adjusted OUT until they contact the drum all the way around. You know they are all the way OUT because the star wheel won't turn anymore, and the wheel will NOT rotate. Thus the are "CENTERED". Then they are adjusted back "IN" with the star wheel until the wheel slightly turns.

Simple right ? Well that works OK for a single servo drum brake system. Single servo ? Means ONE wheel cylinder. Each shoe is attached to a fixed pivot pin on one end and the "servo (wheel cylinder) pushes the OTHER END of the shoe "out" against the drum. The servo (wheel cylinder) is TWO sided. Fluid goes in the middle to push both pistons OUT, one OUT one way and the other OUT the opposite way.

But, but, but . . . the FMC has a DUAL SERVO brake system at each wheel ! Please see and PRINT the pictures of a FMC Brake at the wheel and Figure 9-4
- http://www.fmcowners.com/mbbs22/photos/photo-thumbnails.asp?albumid... -
and refer to it as you read this entry.

There is no "fixed pivot pin". There are TWO SERVOs (wheel cylinders #5) at each Brake assembly. Each shoe #3(one on the left, one on the right) is connected AT EACH END to one end of a wheel cylinder (one at the top. and the other at the bottom). There is a steel tube #15 that connects the two wheel cylinders. That tube is "inside" and cannot be seen from the outside if you look at the outside of the backing plate #1. The star wheels #17 is what gets turned CW or CCW with a special tool called a BRAKE SPOON that gets inserted from the outside thru a slot in the backing plate to move THAT end of the shoe IN or OUT. The Spring #18 is the "clicker" that you may or may not hear, as the star wheel is rotated, as the bump on the spring moves from slot to slot of the star. Note that there a TWO star wheels and springs . . . one at the top another at the bottom, but they are opposite to each other.
The return springs, #20 and #21, are what pull the shoes away from the drum when you take your foot OFF the brake.

So how are DUAL SERVO brakes adjusted ? Well . . . the same as single servo brakes but with "double" variables. You don't know where the shoes are relative to the drum when you start. So with all four wheels OFF the ground (Use JACKSTANDS !) and you laying on your back you reach up and start TURNING one wheel (makes no difference which one you start with) by turning down on it, and start adjusting the star wheel with you brake spoon , in the right direction to move the shoe OUT. . . listening for the slight sound the shoe makes as it just touches the drum. BUT there are TWO adjusters (star wheels) ! So start with one . . . and as soon as it just touches . . . switch to the OTHER adjuster . . . until it too just touches. Now, both shoes should be just touching the drum, but you still don'y know that they are CENTERED. Now comes the part that varies from mechanic to mechanic. While turning the wheel . . . adjust one star wheel in one, two, or three clicks in . . . still turning the wheel . . . and then switch to the other adjuster (star wheel) and adjust it IN the SAME number of clicks. Obviously the fewer clicks made the longer it will take to get the shoeS centered. You listen to hear if the shoe you are adjusting makes more noise or gets harder to turn . . . than the other one (that you haven't even adjusted yet !)
You continue this back and forth . . . all the while turning the wheel . . . until you think that one adjustment pretty much equals the previous adjustment with respect to the "noise" and how hard it is to turn. When you think they are "even" . . . then you can go one or two clicks at top or bottom then switch . . . all the time turning the wheel . . . until the wheel will NOT TURN ANYMORE. NOW, hypothetically, the two shoes are CENTERED IN THE DRUM ! Hooray !

But, but, but . . . you did this laying on your back, one arm is stronger than the other, and one guy is stronger that another . . . so what does "until the wheel will NOT TURN ANYMORE" mean. That is one of the variables.

So, the shoes are centered. Now pick one adjuster (top or bottom makes no difference) and back it OFF . . . how many clicks ? One, two (like Dan K.), three . . . more ? I think two clicks at top then two clicks at bottom, but ALWAYS the same number of clicks. THEN, turn the wheel. How hard is it to turn ? Real hard ? Go two more clicks, top and bottom. Turn the wheel . . . This is where it gets really weird. Each guy has his own feel for how hard the wheel should turn. IT SHOULD STILL DRAG SOME ! But how much ? That "little(?)" bit of drag is going to wear off in a couple blocks. Don't leave them too tight . . . but the wheel is not supposed to "free spin" either.
That is another variable. Each guy has a different feel turning the wheel. In all cases . . . count the clicks out (same number top and bottom). That "magic number" depends on YOU. Then YOU have adjusted one brake assembly to center the shoes (tightly)and then adjusted that one brake assembly to where the shoes are lightly dragging on the drum.

Now . . . go try to lay on your back in about the same position at a different wheel, use the same arm to turn the wheel, and center the wheel adjusting till it won't turn with the same input you gave that first one . . . then click both adjustments back the same number of clicks and turning the wheel . . . convince yourself that the new wheel takes about the SAME force to turn as the first wheel took . . . therefore the must both be adjusted the same ! Then move to the third wheel and repeat, and then finally the forth wheel and repeat. Did they all feel about the same WITH THE SAME NUMBER OF CLICKS ???

Obviously, two clicks is not enough as Dan found out. Henry says 5, Les liked six . . . it is some where around there but there is NO FIXED NUMBER. YOU ARE THE COUNTER BASED ON WHAT YOU FEEL TURNING THE WHEEL(s) OF YOUR FMC. JUST MAKE THEM ALL THE SAME.

There is some combination of bleeding and adjusting that gets the shoes OUT there centered and as close to the drum as possible. If done . . . the FMC takes ONE application of the foot brake to fully engage the brakes. No two pump, three pump. Just one.
Bleeding, and moving the rear hose from the top to the bottom cylinder, and changing to DOT 5 fluid (which takes care of "sitting" corrosion of the wheel cylinders) have all been discussed and explained in this and the Yahoo FMC websites.
Click ON ! Lou #120

Edited by hemi354az 2017-09-27 4:57 PM
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dkarnath
Posted 2017-09-27 5:29 PM (#5014 - in reply to #5013)
Subject: Re: Tire temps? Anyone else?


Location: Medford, OR
(204.10.247.1)
Here's another one for you Lou.

After rebuilding a wheel cylinder on any style drum brake, not just FMC, Do you prefer to bleed before adjustment? Or after you adjust? My reason for asking is, I had a wheel cylinder push rod (link) fall out of position from the brake shoe end on my steer axle of #850, this was from my original brake job. The brake started grabbing real bad. I wondered if it happened when I adjusted the brake out before I bleed the system? Technically, I like to set/slide the brake drum back on over the shoes with as little "play" as possible, so I'm not sure whether my situation had anything to do with adjustment, I'm sure when I rebuilt the brakes in the PO's driveway four years ago, I did what I normally have done successfully in the past. The last couple drum brake jobs I've done, I bleed, then adjusted. Seem to work fine. I also use a "one man" bleeder tool, so I don't need to "pump" up the brakes between bleeding. So adjustment doesn't play a role. Thoughts?
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hemi354az
Posted 2017-09-27 5:41 PM (#5015 - in reply to #5014)
Subject: Re: Tire temps? Anyone else?


Location: Scottsdale, Aridzona
(24.251.160.88)
I bleed, adjust, then bleed again.
Lou #120
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andy1canada
Posted 2017-09-28 8:43 PM (#5030 - in reply to #5008)
Subject: Re: Tire temps? Anyone else?


Location: Victoria, BC. Canada
(75.155.181.152)
When I bought #509 from Dale down in Santa Cruz a few years back, the whole episode became a thoroughly scary treatise in FMC brakes and how they should and should not be set up.

Among other things, I learned that you need to be sure you have the correct master cylinder with the correct H-vacs. I learned that if you didn't have the correct combination, you surely had to have a firm grip on the wheel with both hands when you hit the brakes, or, you could do an unscheduled lane-change.

In retrospect, this all was a blessing as I then resolved when - and if - I got the coach home, I would learn all I could about the brakes on an FMC Motorcoach so I could do the work myself. I submit that this is important that all FMC owners learn about the brake system, whether they do the work themselves or pay someone to do it.

Peace of mind is everything and for me it certainly put to rest any BS about the brakes being overly complicated or inadequate. A trucker that I just bought an engine from - whose logged over 1,000,000 miles in his professional career - told me he would take drum brakes over discs any day of the week, or, at the least, a disc-drum combo.

Keep a sharp eye on the flex-lines to the wheels, fluid levels in the master, any changes in pedal effort or travel, change out the fluid every 3 yrs or so (unless you are running silicone) and you should be good to go without any issues.

Terry
#846
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LCAC_Man
Posted 2017-09-29 10:29 AM (#5034 - in reply to #5030)
Subject: Re: Tire temps? Anyone else?


Location: Oceanside, CA
(70.183.105.121)
What's a HydroVac...?? :D
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