Community Forums

Flattrip · 02-24-2009, 07:24 AM

Hi, I'm new here and to the rv world in general. We bought a motorhome last fall.

I bought a class c with a chevy express van workhorse chassis and while going down a steep grade in NH I could smell the brakes near the bottom of the mountain. I was in low one and trying to let the motorhome go to 35 mph then bring it down to 30 and repeat that cycle.
Everything seems to be ok and I have gone over the Smokey Mountain ok doing the same thing.
There is a slight pulsating during heavy braking. Is this normal?
Should I change the pads? There are only a few thousand miles on the coach so far.

I don't know if I glazed the factory pads any or not. When I am braking normally it seems to be fine.
I googled truck/rv pads and found some severe duty pads made by hawk which sounded pretty good. Should I change the pads to something like the hawk severe duty pads? I would guess the factory pads were semimetallic?
Any help or suggestions for brake replacement pads would be appreciated. Thank you, Pete

bdpreece · 02-24-2009, 07:37 AM

The pulsating is caused by overheating the rotors which then warp. You are doing the right thing by gearing down and only using the brakes every so often to bring the speed back down. You didn't say if this is a new or used coach. If used I would probably have the brakes checked. If new I would not mess with them unless the pulsating is real bad and bothers you.

Flattrip · 02-24-2009, 08:35 AM

Thank you, It is a new coach. Pulsating just occurs if I push the brake really hard and not really severe I don't think - I have nothing to compare it with, -- It does have abs I believe - my small car just has regular brakes.
It was a leftover 2006 chassis - model year 2007 for body.

I am thinking of heading west and I was worried about the brakes heating up as I hear the mountains are much worse out toward glacier park montana or more south toward yellowstone. That is the main reason I was wondering if I would be smart to put something like those severe duty brakes in as they say they handle heat better?

Alan_Hepburn · 02-24-2009, 09:04 AM

We need some more information:

* How heavy is the rig? Is it at or over the GVWR?
* Were you towing anything? If so, does the towed vehicle have brakes? What does the towed vehicle weigh? Are you exceeding the GCWR of the rig?

If you overheated the rig's brakes I would have the brake system inspected - the pads and rotors might be compromised, and I'd definitely have the brake fluid replaced - once it boils it's time to replace it.

DriVer · 02-24-2009, 09:09 AM

Quote:

Originally posted by Flattrip:
It is a new coach. Pulsating just occurs if I push the brake really hard and not really severe I don't think - I have nothing to compare it with, --

Flattrip, What you are describing to me is what you should be feeling when the ABS circuit cuts it. It is normal for the brake pedal to pulse quite rapidly within a short period of time.

If you slowly apply the brakes and the pedal pulses you may have warped a rotor otherwise I would say you're doing just fine.

Flattrip · 02-25-2009, 06:15 AM

I haven't weighed the coach yet. I was towing a 2700 lb car with about 50 lbs of wood leveling chocks in it.The car does not have a sup. brake sys installed yet.
I am looking into supplemental brake systems now, boy is there alot of reading to do on that.

If I keep it at 35 mph in low one down a 6 to 9 percent grade, and step on the brake fairly hard and bring it down to 30, it climbs in speed to 35 pretty rapidly. I guess this is normal, but it makes me worry about overheating again.
Correct way is to apply brakes fairly hard to bring it down fast to get my foot off the pedal as quick as possible or should I gently apply to slow down. I feel like I do an aweful lot of braking even in low one on some of these grades.
The brake for the tow car I take it will help dramatically?

bdpreece · 02-25-2009, 06:22 AM

Have to agree with DriVer on this one. I assumed you were getting the ABS pulsating to keep one or more wheels from locking up.

bdpreece · 02-25-2009, 06:26 AM

Oops lost a line in the last post. It should have read.
Have to agree with DriVer on this one. I assumed you were getting the pulsating all the time. If it only pulsates when you press hard it is probably ABS system pulsating to keep one or more wheels from locking up.

Alan_Hepburn · 02-25-2009, 10:14 AM

I would try and get some weight readings to find out what you've got. If it's a Class C rig you might well be overloaded. The dealer may tell you that you have a tow rating of 3500 lbs but that assumes a LOT. You need to load up the RV as if you were going on a tip and drive over a scale. Get weight numbers for the front axle, and the rear axle separately, and the tow car too if possible. Now you can do some figuring.

Front axle plus rear axle equals gross vehicle weight. Subtract this from the posted GVWR of your vehicle and the result is how much you can load up the axles of your rig. If the number is negative, you're overloaded.

Front axle plus rear axle plus tow car weight equals the gross combined weight. Subtract this figure from the posted GCWR of your rig and you'll know how much you can tow behind your rig.

The brake system on the RV is designed to work up to the GVWR of the RV - if the actual weight is higher than the GVWR then you're overworking the brakes. If your tow vehicle doesn't have a working brake system, then the weight of the vehicle is being added to the load that the RV's brakes must handle - this will usually put you over the GVWR if you're not already there.

As far as braking technique - there are two schools of thought: hard braking followed by coasting and constant light braking. I won't offer an opinion on which is better, although I tend to use the hard braking technique myself with my Class A rig. It works for me - I recently returned from a trip that took me over the Tehachapi Pass in Southern California. Using the Grade Brake in my Allison transmission I was able to maintain a steady 55 mph down the 6% portions of that grade with very little brake input.

If your transmission cannot maintain 35 mph down a similar grade I would suspect that you're getting some torque converter slippage, possibly due to being overloaded. In addition to changing the brake fluid I would take a close look at the transmission fluid as well as it may have been overheated as well.

Forest Grump · 02-25-2009, 02:31 PM

I have a Class A, F53, and go down the back way from Big Bear to Lucerne all the time yanking my jeep. It is a 16 to 18% grade. I put it in low gear and it never goes above 25 mph. I only use the brakes to slow down before the hairpin turns.

Your pulsating is due to the rotors being warped, change all the pads you want your rotors are still warped. Turning the rotors should solve the problem. Allow your brakes to cool before uses. Are you sure you are in low gear or are you in second. 35 mph in low gear your engine should be hemorrhaging. Do you have a tach if so what does it say in low range at 25 mph. If you don't have a tach have one put in.

If you continue to have problems and are really in 1st gear there are high performance ventilated rotors available. Some dually's only have brakes on one wheel, hope that isn't you.

NeilV · 02-26-2009, 12:45 AM

Quote:

Originally posted by Flattrip:
I was towing a 2700 lb car with about 50 lbs of wood leveling chocks in it.The car does not have a sup. brake sys installed yet.

BINGO!

Get those toad brakes installed before you hook up again.

Depending on the grade you were on you could have warped the rotars or you may just be getting ABS back pedal that you are not used to.

Having the fluid, pads and rotars checked would be the safest course instead of just guessing or hoping for the best.

Alan_Hepburn · 02-26-2009, 08:28 AM

Quote:

Originally posted by Forest Grump:
Some dually's only have brakes on one wheel, hope that isn't you.

I'm assuming you're referring to a tag axle here. In the vernacular a "dually" is a configuration where there are 2 wheels on each side of the rear axle. Since the brakes are usually installed on the axle and not on a wheel you'll have one brake assembly on each side of the vehicle, but you'll never have a separate brake assembly on each wheel of a dually...

On the other hand, I suppose some cheap tag axle systems might be installed without brakes...

Forest Grump · 02-26-2009, 09:35 AM

you're right I had a senior moment, brain fart.

Flattrip · 02-26-2009, 09:44 AM

Thanks everyone.
I have a scangauge and never let it get above 4000 rpm. engine temp maxs at 235 on climb and then stays steady. I think the transmission came close to 235 the day they smelled , it was in the 90's outside. They were not visibly smoking as I brought it immed. to a stop and didn't see any smoke,but I could smell them. It was a two lane road so I couldn't pull over and also it leveled out. I have 1800lb ccc and 3500lb tow cap. I will see if I can find someplace to get it weighed. I don't think I was at capacity. I had maybe 30 gals of water between the tanks and a half tank of fuel( 55 gal) _ I would guess 500 - 700 lbs of clothes and food but I can't really be sure.

It's a 4 wheel abs disc brake class c -

Would there be visible bluing on the rotors? or would they look normal if they were warped?