Front-end shimmy comming down the mountain

[fishingguy303]

New to fifth wheel hauling here and experiencing front end shimmy when braking at normal highway speeds (45-60mph) going downhill and hauling. I am hauling a 2013 Dutchman Voltage 3 axle with a 2013 Chevy 3500HD 6.6 Diesel dually and cant figure out what's up? I had the TV brakes checked by the dealer, all is fine, weights are fine. engine brakes are working and the shimmy is still there with a high or a low gain setting, newby here needs help/advise. Thanks, Frank.

[larry_barnhart]

rhagfo wrote:

Me Again wrote:

rhagfo wrote:

larry barnhart wrote:
We don't have an EB brake and for what we tow it is not needed but I can see it would for a much bigger fifthwheel and I know I would like it. Starting slower down steep mountains is the key.
chevman

Really, you think that 35' Alpenlite is that lite? Maybe you feel you don't need one if you don't have one, but after installing mine, life is far better coming down a long steep grade.

The hills in the Oregon Coast range have some good grades in them, I can be traveling down at 60, drop to 4th (5 speed manual) and be down to 45 without touching the service brakes! If anywhere along that downgrade I need a panic stop, I still have COLD brakes both TV and 5er!!

I see an EB to be like 4X4 you don't need it UNTIL you need it!!!

Russ Larry's GM has grade braking unlike our Dodges that did not lock the TC in OEM trim! V8's seem to hold back better also. BIG difference!

I have the exhaust brake on a secondary switch to my smart controller and even with the TQ locked, the mighty Cummins just free wheels. Chris

If my Pacbrake worked that poorly, I would demand my money back. I have the advantage of a manual 5 speed, and I also bypassed the ECM, so my Pacbrake is also instant on no delay.
It is also activated by compressed air @ 150psi. I very seldom need to even tap the service brakes on a down hill.
Maybe someday soon I will get a chance to come down the west side of Lookout Pass on I90 in Montana's Bitterroot range!

22,920 combined lbs is the weight so it is not thinking what it is but what it is. Alpenlite is under 15000 lbs loaded for the winter's trip south.

chevman

[Me_Again]

diesel man 03 wrote:
My thoughts are front brake rotors.

Glazed or Wrapped? Again, wrapped rotors will be felt on most stops. Glazed rotors willing act up when heated up under heavy braking.

[diesel_man_03]

My thoughts are front brake rotors.

[rhagfo]

Me Again wrote:

rhagfo wrote:


If my Pacbrake worked that poorly, I would demand my money back. I have the advantage of a manual 5 speed, and I also bypassed the ECM, so my Pacbrake is also instant on no delay.
It is also activated by compressed air @ 150psi. I very seldom need to even tap the service brakes on a down hill.
Maybe someday soon I will get a chance to come down the west side of Lookout Pass on I90 in Montana's Bitterroot range!

Russ the point I was trying to make was if I turn off my Banks EB then the Dodge Cummins on compression does little to hold back on hills even with the TC locked(aka grade braking). For some unknown reason the V8 diesels with grade braking do provide a fair level of hold back on hills. Not as good as a EB, but for many years owners like Larry have found it acceptable.

I went down Washington pass eastbound in second gear on the EB without touching my service brakes at 20k+ combined. After the hair pin corner I went up to 3rd and ran that next section and used service brakes once at the corner at the bottom of that section.

Once one tows with an EB, they work never want to not have one. Chris

My bad! Misread your post! Very true, there is some resistance without an EB, but nowhere near enough to feel that you can count on it to slow a load.

[Me_Again]

rhagfo wrote:


If my Pacbrake worked that poorly, I would demand my money back. I have the advantage of a manual 5 speed, and I also bypassed the ECM, so my Pacbrake is also instant on no delay.
It is also activated by compressed air @ 150psi. I very seldom need to even tap the service brakes on a down hill.
Maybe someday soon I will get a chance to come down the west side of Lookout Pass on I90 in Montana's Bitterroot range!

Russ the point I was trying to make was if I turn off my Banks EB then the Dodge Cummins on compression does little to hold back on hills even with the TC locked(aka grade braking). For some unknown reason the V8 diesels with grade braking do provide a fair level of hold back on hills. Not as good as a EB, but for many years owners like Larry have found it acceptable.

I went down Washington pass eastbound in second gear on the EB without touching my service brakes at 20k+ combined. After the hair pin corner I went up to 3rd and ran that next section and used service brakes once at the corner at the bottom of that section.

Once one tows with an EB, they work never want to not have one. Chris

[rhagfo]

Me Again wrote:

rhagfo wrote:

larry barnhart wrote:
We don't have an EB brake and for what we tow it is not needed but I can see it would for a much bigger fifthwheel and I know I would like it. Starting slower down steep mountains is the key.
chevman

Really, you think that 35' Alpenlite is that lite? Maybe you feel you don't need one if you don't have one, but after installing mine, life is far better coming down a long steep grade.

The hills in the Oregon Coast range have some good grades in them, I can be traveling down at 60, drop to 4th (5 speed manual) and be down to 45 without touching the service brakes! If anywhere along that downgrade I need a panic stop, I still have COLD brakes both TV and 5er!!

I see an EB to be like 4X4 you don't need it UNTIL you need it!!!

Russ Larry's GM has grade braking unlike our Dodges that did not lock the TC in OEM trim! V8's seem to hold back better also. BIG difference!

I have the exhaust brake on a secondary switch to my smart controller and even with the TQ locked, the mighty Cummins just free wheels. Chris

If my Pacbrake worked that poorly, I would demand my money back. I have the advantage of a manual 5 speed, and I also bypassed the ECM, so my Pacbrake is also instant on no delay.
It is also activated by compressed air @ 150psi. I very seldom need to even tap the service brakes on a down hill.
Maybe someday soon I will get a chance to come down the west side of Lookout Pass on I90 in Montana's Bitterroot range!

[fishingguy303]

Thanks to everyone for all the great input. Looks like I have to adjust my driving technique and will do so. I will have to see how to correctly engage the engine brake feature and use that to keep my speed constant going down hill and start at a slower speed. I have the truck being checked out at King Chevrolet in Longmont where I bought it and will discuss warped rotors, computer, torquing the wheel lugs, etc. Thanks again!! Awesome site!!

[d-mac1]

To the Op. I'd say you've got your answer.

Perhaps deglaze the rotors but otherwise it sounds like you just need to go slower on the hills. Get over in the right lane and start down the hill close to the speed you intend to descend at and let it speed up a little, then get the exhaust brake going to hold that speed. I'm guessing you're starting down too fast and then have to slow down via the brakes. Downshift if you need to hold it back more. Sometimes I'll end up going too slow (e.g. from the tunnel to Silverthorn) and will give it fuel to speed up some vs upshift to another gear that will run too fast. I suggest you err on the slow side especially when you're a new driver.

Watch the loaded trucks. Some of em just crawl down those slopes and they aren't touching their brakes. Then theres the fast ones who come down with brakes smoking. You don't wanna be them!

[ChuckV1]

Like the OP stated, you down the hill the same way
(gear)you came up the hill in. If that is 45mph so
be it. As well check your ait presure in the tires
and make sure they are correct, if low they will
make the front end shimmy when braking. Never, ever
let air out of a hot tire's (tires gain some air
pressure when hot), best to check tires after they
are cold. I check mine in the mornings after sitting
for the night or if I stop for more that 45 minutes
to a hour.

[shadoow]

Cummins12V98 wrote:

Water-Bug wrote:

Cummins12V98 wrote:
Op use your exhaust brake and down shift to the same gear you came up a similar hill. You should rarely need to touch your brakes. 28+K here combined and it is rare I touch the service brakes descending a grade.

The instructions have already been posted

And you just did again.

OOPS I did it again. :R

only way to use the same gear in a Chev/GMC automatic (allison) is to place the trans in 'manual' mode. The trans will then stay in the selected gear until you select another or go back to 'auto'. When the trans is in the 'manual' mode the exhaust brake does not function. Maybe it works different on dodges.

[Water-Bug]

Befor I retired, I worked for a company that had a large fleet of 3/4 ton and 1 ton pick-ups and vans. Working 2nd shift, I spent a lot of time BSing with the mechanic that maintained the fleet. Company policy required him to purchase OEM parts. That meant that he had to buy the OEM Chinese disc rotors. He turned ALL the replacement rotors befor installing them, because he swore that they came from China warped. He clamed that turning them doubled the life of the brakes, and cut his work load in half.

[Cummins12V98]

ol Bombero-JC wrote:

Cummins12V98 wrote:

Francesca Knowles wrote:

Water-Bug wrote:

EDIT Darn Chinese brake rotors. They are OEM on just about everything.

:h

Will brake rotors produced elsewhere yield a different result in the same circumstances? And if so, what Country of Origin/brand do you recommend?

Yes! US or Canadian made quality brands.

No!

Rotor brand choice is secondary to proper hill descending technique..:S

If you've been behind the/a wheel long enough - that "event" would/could (did) occur *before* off-shore parts became the norm.

.

Sorry but a quality rotor is less likely to do as the op has described. Those are usually US or Canadian made.

[laknox]

tsetsaf wrote:
Drilled and slotted look cool but actually hurt braking performance for heavy hauling. Op has the answers he needs: 1.check the computer 2 check the rotors 3 use the eb more and service brakes less.

Forgot to say to also check the controller setting. May simply need to be more aggressive with the trailer brakes.

Lyle

[laknox]

Water-Bug wrote:

RAS43 wrote:

Red-Rover wrote:
When my front wheel brake rotors overheat I get steering wheel shimmy and yes, the brake mechanics will check out okay after cooling.

My thoughts also. I have experienced the same symptoms in our mountains.

Simply said, your front brake rotors are warping under temperature. They may have been seriously over tempt at some point or suddenly cooled while hot. Driving into standing water with hot brakes will do it.

EDIT Darn Chinese brake rotors. They are OEM on just about everything.

That was also my first thought. Have had warped rotors a couple times in the past 40+ years. Also, bent drums, but that's way old-school. 🙂 Another thought... What about the ABS system malf'ing?

Lyle