FG shaking front end while braking

[Dellorto]

Hey everyone. Last May we purchased a 2015 FG with a 16 foot Bigfoot camper. It has been an excellent rig and I only wish we had more time to use it last summer. This is our first FG and first heavy Japanese truck, so I have been learning as much as possible about our rig before we start any serious adventure. ExPo is an amazing resources and most of my newbie questions have been answered somewhere in the forum. The problem that I cannot find in the forum is a shaking front end during braking.

I have 16” Outback Accessories rims with newish Toyo tires and due to the minimal clearance between the rim and the drum, the previous owner used DynaBeads to balance the tires. However when I brake, during certain conditions such as a downhill, the front end shakes and there is a pulsing that comes through the steering wheel and can shake the entire cab. This doesn't happen every time I brake, but when the shaking does occur, it makes braking feel unsafe. Quizzing the previous owner, he attributed the shaking to the DynaBeads in the tires acting oddly during braking. Though, I'm beginning to suspect it is warped drums and I feel like the problem is getting worse. Also, I scoured forums searching for complaints about DynaBeads and I've never seen anyone complain about shaking during braking. Before I go and replace the drums, what else should I check? What am I missing? The previous owner said he recently had the drums turned, too. Thanks everyone for taking time to help me with this problem!

 

[IdaSHO]

I would certainly assume warped drums/rotors.
Contaminated pads/shoes could cause similar effects as well.

A slight warping of both front brake surfaces can come and go, and not happen all the time.
When they are synced, and brakes applied, the effect is magnified.

Don't forget about worn front end components and wheel alignment. Steering and suspension components should also be looked at.

 

[SkiFreak]

Don't forget about worn front end components and wheel alignment.

Unless the truck has had a hard life I would not expect component wear on a three year old truck.

Before forking out money on a drum replacement you might want to talk with a Fuso dealer/service centre to get their opinion.

 

[IdaSHO]

Life and miles have little to do with simple curb smacks.

And that's all that it takes to wipe out a TRE, especially with a heavy truck and mediocre front end components.

All plenty reason to cover your bases. Assuming anything with a dangerous brake/steering problem is foolish.

 

[gait]

some simple (silly) questions. Do you feel anything through the brake pedal? With wheel jacked up is brake adjustment "uneven" .... can you feel it grab as wheel rotated. How violent is the shaking? (Someone recently described shaking front end as being "quite bad" which really meant "impossible to drive" - the panhard rod with coil springs had come adrift). Is the shaking a pitch, or a yaw, or both? Does the shaking cause steering wheel to rotate, or just column vibration? Does the shaking occur only in straight line, or corners, or both? Are all the rubber bush things ok? Any protective rubber things torn? Any obvious sign of dings or bends in steering bits? Are bolts for steering box tight? How much free play in steering wheel? Are wheel bearings and king pin bearings good? Tyre pressures. Etc.

 

[kerry]

If you could find some spare rims and tires, you could swap them on and see if the problem continues. That would answer whether it is a tire/wheel issue or something else. There are proportioning valves in the Fuso braking system. Since it's happening when going downhill, I'm wondering if that orientation exacerbates a problem with the proportioning system by putting too much braking load on the front axle? I'd at least look at that system. If the drums have been or are warped, it suggests they might be overheating. If they are, that might be caused by insufficient braking power on the rear axle. When I had my front brakes adjusted at the dealer after they redid them and I was getting a hard pull under heavy braking, the service manager said to me that there was a side to side proportioning valve on the front brakes. I find that very hard to believe but if it is true, perhaps some pulsating failure in that valve might produce your sysmptoms.

 

[Dellorto]

Thanks everyone for the great recommendations and ideas. I’m taking the FG out for the remainder of the long weekend and will pay closer attention to my inputs, topography, and reaction of the FG shaking. I truly appreciate all of your time in helping me diagnose this problem.


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[javajoe79]

I find it unlikely that a braking issue would come and go based on heading downhill. I also think you would feel the vibration in the pedal.

 

[skippythedog]

The advice from Kerry and Gait is spot on.....First and foremost, establish whether your're getting feedback through your pedal. It's unmistakable, a pulsing of the pedal. One thing you cannot do in a FUSO is easily isolate if it's coming from the front or rear. This is due to the design of that system...Nothing to worry about as your problem is definitely in the front end now, based on your symptoms.

My Dynabeads (in 17 steel rims) do nothing funky during braking. They do give a little side to side wobble (static balance), felt in the steering wheel, as you accelerate through 20-30 mph. I surmise this is because they're trying to establish their position. My experience with balancing beads is far and away superior to trying to find a shop that can competently balance tires on these trucks. I'm never, ever looking back on that issue. However, if your wheels are alloy, they are substantially lighter than steel and it is possible that balancing beads act differently. My wheel tire combo weighs about 145# and I use 8oz of beads. Any idea how many oz in yours?

I'm curious about these "Outback Accessories" wheels. I can't find 'em online. Are they alloy? Are they the same ones (Hong Kong sourced) that are sold by Earthcruisers? If so, there have been some relatively serious issues with those that have gone unaddressed by Earthcruiser even though they were challenged directly on this forum about that. They were very evasive on the phone too....I even got into a bit of a skirmish with them and some other unknown party who defended them (and was apparently involved with sourcing them) right here on the forum.
I chose not to get their wheels solely because of that (and because I chanced to get a hold of an EC shop technician who told me the story of these wheels.)... Hell, I even spoke to the technicians and store managers at the Les Schwab in Bend, OR. to investigate. (They mount EC's tires) They were not helpful but only because they only mount the brand new, loose tires and wheels and have never seen one of the trucks.
I'm not interested in re-hashing that here and raising anyones' hackles, so PM me and I can give some particulars....direct info from 2 owners of these wheels. In fact, even if your wheels are not theirs but are 16" alloys, the info may be useful.

 

[Dellorto]

Update from my weekend tour and brake check. I could not replicate the braking issues this weekend and I suspect it was because we encountered no hills. When I was intentionally braking hard to test some of your recommendations, I could feel slight pulsing in the front end. However, it wasn't shaking that would alarm me and I received little feedback from the FG. When I reflected on the braking issue that drove me to write the initial post, I think the grade has something to do with the magnified shaking. I was on a mountain pass (Highway 410 over Cayuse Pass past Mt. Rainier) and I suspect the slight gradient of the highway is what magnified the shaking. The pass is of a sufficient gradient and speeds where gravity slightly pulls the FG downhill, but the exhaust brake scrubbed too much speed, so light braking was the best way to scrub 2 to 5 mph before a fast corner. I believe it was sustained light to moderate braking for several hundred feet that intensified the shaking in the cab. I definitely recall numerous instances of swearing as the cab shook and rattled, all while descending a slight downhill. We're heading back to the mountains in a couple weeks for a long weekend, so I will take all of your helpful suggestions, test them on our tour, and report back.

 

[skippythedog]

It stands to reason that your front end wobble could be exacerbated under braking downhill as 70% of a vehicles weight shifts to the front under braking.

 

[IdaSHO]

It does, and is why I brought up steering, suspension, and alignment.
They can all act differently when pointed downhill, or under heavy braking, or both.

Also, it may very well be the attitude of the truck when simply pointed downhill.
Does the truck have any brake proportioning valves? Front to rear or left to right?

 

[kerry]

I'm pretty sure my 99FG has a front to back proportioning valve controlled by a rod connected to the rear suspension (unless I am completely imagining this). You can crawl underneath and see if you see a rod connected to the brake tubing/valve in the vicinity of the rear axle. As I mentioned above, the service manager told me there is a side to side proportioning valve on the front axle brakes. I find this extremely hard to believe since any failure in a valve like that on the front axle would be so dangerous as to outweigh the benefit. I once had warped rotors on our 94 Land Cruiser. Not noticeable much under most driving circumstances on level ground where the truck wanted to slow down when I let off the gas. However it was definitely noticeable and irritating on long downhills where the truck was always trying to accelerate and the brakes were holding it back. I've never had warped drums, only warped rotors so I don't know what exactly warped drums feel like. I'm under the impression (probably mistaken) that warped drums are less frequent than warped rotors at least partly because a warped drum is really an ovaled drum which seems slightly harder to produce than a warp in a rotor.

 

[gait]

is any brake fluid being lost (however slowly)? Any signs of oil leaks or grease or fluid around the back of the drums? Any creek crossing before shaking? A source of pulsing can be brake shoes grabbing. I assume the hubs were free?

 

[skippythedog]

I'm going to take the liberty here to fill in the blanks..... This trucks wheels are most certainly bent: Read on....

I bought my truck 2.5 years ago and immediately started looking for a viable SRW setup....I left no stone unturned....I finally settled on the alloy 16"s from Earthcruiser.....I was just about to order when I heard about some problems that a Denver forum member was having with the wheels. He communicated with me directly on this issue. (I really should throw this guy under the bus as he did not disclose everything to the current owner, the original poster of this thread, when he sold it.
I find that to be wholly unscrupulous and reprehensible.)

The EC wheels have so little clearance between the drum that a simple tape weight when placed anywhere other than the outermost plane will get squished and bend the wheel when you tighten the lugs. This is apparently what happened to this truck...in Denver.

I made inquiries directly to EC about this problem, presented my findings on this forum, and was berated on this forum by some guy (dealer of their wheels) and told to look him up at the SEMA show in Nevada 8 months later if I wanted an answer. I found this whole approach to be quite evasive and swore then and there to never patronize EC or their affiliates. Dishonesty is the one thing that will skeeve me off to no end.

The Denver owner simply told the new owner that he must use balancing beads as weights wouldn't fit. He knew the wheels were tweaked when he sold the truck. Or is it possible that he had someone half-ass bend them back into shape? We may never know. Apparently the wheels were straight enough to pass a road test and normal driving but the problem turns up as the weight shift is amplified during downhill braking.

EC apparently never investigated fully, took no responsibility for a defect, took no responsibility to make clear what type of tape weight would work for static balance and have never published a finding. Hell, they wouldn't even give me
(a prospective customer) a straight answer, not on the phone; not when queried on this forum.

Challenging me to show up personally in Nevada 8 months down the road to get an answer was absurd on it's face.

This is most certainly what's going on with this truck. Now, the only question that remains is; Are the drums bent too?