Truck and Trailer

[SteveH]

No mistake, I don't really advertise it, but thought you knew.

[slowmover]

I was helping keep you off radar.

[SteveH]

I'm not ashamed of where I live, or even trying to hide it. The location I list is just my little "statement" of how I feel about some things, if you know what I mean.

[BoldAdventure]

I spent some time researching the brakes on the 3/4 ton RAMS compared to the 1/2 tons.

I would like to clear some misconceptions up and lay to rest this forum myth that 3/4 tons somehow stop better than a 1/2 ton.

The 3/4 ton's 'heavy duty' brakes vary only slightly in comparison to the 1/2 tons. You get a hydroboost in placement of the vaccum boost and 3 piston calipers upfront.

The half ton features standard vacuum boost and 2 piston front calipers.

The 1/2 ton has an 13.230 in rotor and the 3/4 ton has a 13.855 in rotor.

The rotor thickness difference between both of them is very slight.

The reality being, that both vehicles actually have similar stopping power and stopping distance. The hydroboost just provides better equal line pressure to the brakes.

If you're load is appropriate to your vehicle, both should perform well. There is no 'heavy duty' braking. It's more marketing. Yes I am claiming it's marketing, because the reality is it's engineered properly for the task. Take it how you will. Greater mass, needs more rotor. But they're equal for the jobs being done. It's literally scaled up. But know I talking about proper application. (Not will my Jeep Cherokee stop 11,500lbs as effectively as a 3/4 ton, because the math says NO)

I'm saying they are about equal. And that when a half ton is towing an appropriate load, it will stop shorter of the 3/4 ton with equal load because of less mass.

That being said, let's explain some physics to you guys.

Assuming proper operation of the brakes, the minimum stopping distance for an automobile is determined by the effective coefficient of friction between the tires and the road. The friction force of the road must do enough work on the car to reduce its kinetic energy to zero.

he bracking force is

Fb=ksFn


the normal force is the weight which is proportional to the mass.

Fn=mg


where g is the acceleration of gravity. so the braking force is

Fb=ksmg


and that braking force is proportional to the deceleration a of the vehicle

Fb=ksmg=ma


so the deceleration due to braking is

a=ksg


independent of the mass of the vehicle. the increased mass increases the braking force, but it also increases the momentum by the same factor. if the vehicle was on a slippery surface, ks would be less and the vehicle would decelerate more slowly. if the vehicle was on the moon, g would be less and the vehicle would decelerate more slowly. also if the vehicle is pulling a trailer which does not have braking on its wheels, that increased mass from the trailer and load contributes to the momentum, but not to the braking force because only the pulling vehicle weight is pushing down on its wheels (that have brakes), so it decelerates more slowly.

if you know the velocity when the brakes are applied, the braking distance is:

d=vt−12at2


and since the final velocity is zero

0=v−at


then you can calculate the braking time

t=v/a


and

d=v(v/a)−12a(v/a)2=v22a=v22ksg


In laymen terms, it's simple. Proper vehicle application. But please don't go around claiming a 3/4 ton stops better than a half ton because of 'heavy duty' braking.

End of rant.

[slowmover]

Look to tire tread area. Stopping my solo 9,000-lb truck is no easy task. A 5500-lb half ton with tires better for handling/braking is a Corvette by comparison.

[tjdonahoe]

you guys should go to the post about the better brakes on the BMW , crossover SUV ,they are capable of going 130 mph and therefor need better braking....

[slowmover]

We have. In some cases many times on the subject.

[BoldAdventure]

So many components and variables to the whole suspension/performance equation. It's not all black and white, but some think it is. Lots of Apple and Oranges.

[tjdonahoe]

All I can say is all of the newer diesel 3/4 ton up have an exhaust brake,don't need to use the service brakes much on the down side, that is one over the light pickups..Now there Bold adventure how come you are worrying about the brakes .. Last I heard your toilet wasn't quite up to par???

[slowmover]

Exhaust brake is a strong recommendation when the trailer weight is in excess of 10,000-lbs per the upfitter and bodybuilder guides published by the OEMs. Not otherwise.

Lagniappe for us, especially as the automatics now available can more than handle grade descents without one.

Granted that an auto trans diesel truck with integrated brake is sweet.

[Lucky Tom]

This may be the best place to put this question, since it seems like there are a lot of people familiar with Arizona on this thread. My question is what kind of road is I 17 from Phoenix to Flagstaff. I may be going that way when I leave Alumafiesta in Tucson. Is it curvy, hills, etc? And does anybody know if it is in good shape?

[tjdonahoe]

it is a good highway, up hill all the way, why would anyone go that far to look at snow??

[Lara Me]

Originally Posted by BoldAdventure

In laymen terms, it's simple. Proper vehicle application. But please don't go around claiming a 3/4 ton stops better than a half ton because of 'heavy duty' braking.

End of rant.

Car & Driver tested both a 2013 RAM 1500 and a 2014 RAM 2500 Cummins Diesel. Both were crew cab 4x4 models. The 1500 weighed 5600 lbs, nearly 2400 lbs less than the 2500.

The 1500 stopped from 70mph in 195 feet. The heavier Cummins? It took only 7 feet more to stop from 70 mph, at 202 feet.

Now load both trucks with a 8000 lb loaded Airstream, hitched up properly. I am pretty sure that is when you'll really find out whether the extra braking components on the 2500 HD models prove their worth. Add some real world experience in: say you're descending on a long steep pass, like I5 over the Sisykous or the Grapevine. The 2500, in tow haul mode, will not need to ride the brakes near as much given that the built in engine brake on the Cummins diesel will do a credible job keeping speed in check, and when it comes time to step hard on the brakes, an extra piston and wider calipers will likely do a much better job in controlling the braking.


Not taking issue with your math, but in my experience actually hauling the Airstream through these passes, both the extra power and extra cooling and extra braking capabilities make a noticeable difference.

There are lots of reasons to choose a 1/2 ton truck over a 3/4 ton truck, but I don't think the lack of extra HD capability in braking and cooling components is one of them, especially when pulling the kinds of loads the 3/4 HD trucks were built for.

[J. Morgan]

The power of the Cummins aside, the biggest difference in a 1/2 ton and a 3/4 ton truck is the floating rear axle and its associated bigger wheel bearings.

I don't think these come into play much towing an Airstream because there isn't really that much extra (if any) weight added to the axle especially when WD is used.

As stated above, the limitations of modern vehicles when stopping is determined nearly solely by the friction the tires generate against the road. Bigger brakes will heat more slowly, but the difference in size, and ability to heat slower are very marginal. (In the above comparison of the 1/2 and 3/4 the difference in the circumference of the front Rotors is less than 5%)

Hydroboost and a vac booster do the same thing, they both add physical force to the piston in the master cylinder. (I.e. they literally help you push the pedal down), other than the method of applying this mechanical force, both systems are otherwise identical.


1/2 Ton 4WD Truck, 72 Sovereign Hensley Arrow

[Lara Me]

Originally Posted by J. Morgan

The power of the Cummins aside, the biggest difference in a 1/2 ton and a 3/4 ton truck is the floating rear axle and its associated bigger wheel bearings.

Bigger brakes will heat more slowly, but the difference in size, and ability to heat slower are very marginal. (In the above comparison of the 1/2 and 3/4 the difference in the circumference of the front Rotors is less than 5%)

Hydroboost and a vac booster do the same thing, they both add physical force to the piston in the master cylinder. (I.e. they literally help you push the pedal down), other than the method of applying this mechanical force, both systems are otherwise identical.

Not to nitpick, but the choice of a 1/2 ton over a 3/4 ton diesel is made on factors other than which truck operates as the best tow vehicle. They are different, but when judged purely for their ability as tow vehicles, the 1/2 ton is never the equal of the 3/4 ton diesel, and cannot match its capabilities.

3/4 HD trucks have many more differences over their 1/2 brethren, including frames, suspension, and axles. Grab a creeper and crawl under both and look around a bit. You can easily spot the differences.


The HD rotor's surface area is actually closer to 10% larger per wheel than the 1/2 ton's rotor, not 5%. A three-piston caliper is a noticeable differences over a two piston model. Having ridden both motorcycles and track cars with upgraded brakes, you feel notice the difference immediately. One has better grab and sustained pressure, and does not fade after repeated applications. Add in boosted pedal pressure, and the feel of braking on a loaded HD truck is noticeable.

The real test of differences between the two trucks would be done with the same trailer on the same driving conditions. My own experiences suggest the HD truck performs significantly better under load in most scenarios involving towing a heavy Airstream, except perhaps one: handling very twisty roads at higher speeds. That is where the added weight and extra height of the 3/4 ton trucks counts against them, and makes them slower and more ponderous in twisty corners. You see that in the measured skid pad measurements in the magazine reviews. The 1/2 ton trucks post a .78 lateral g force versus the .70g forces for the 3/4 ton trucks, and any driver will easily sense the slower handling of the bigger trucks pretty quickly.

Other drawbacks? 3/4 ton trucks are not great as daily drivers; they are tough to park and turn around, and nowhere near as efficient as a V6 diesel. They require more costly maintenance for two main reasons: (1) their engines use more oil (about 25% more oil than the V6 diesel), and (2) the fuel filter requires more frequent changes (the 2013+ RAM CTD's use 2 fuel filters which get replaced every 10k miles at a cost of $90-120). Both of these services are both very easy DIY driveway projects, but if you take them to the dealer, you'll pay more than the V6 service.

Their larger diesel engines also aren't happy when regularly driven unloaded in stop and go traffic with lots of idling which can tend to clog their particulate filters and force them into regent modes if done regularly. A Cummins in particular is happiest and at its best when it is towing under load, in contrast to most V4 and V6 passenger truck diesels, which are really built for efficiency and not heavy duty hauling of large payloads/trailers. If you aren't hauling a heavy Airstream or larger trailer, you really have no need for a 3/4 ton diesel.

However, judged primarily as a tow vehicle for the bigger Airstreams, I'd never choose a 1/2 ton eco-diesel over a 3/4 ton diesel. In my case, I was fortunate to be able to dedicate the 3/4 ton truck to mostly tow duties, and I bought a smaller efficient used car for regular commutes after driving the 3/4 ton for a few months and recognizing its inherent limitations beyond its towing prowess.

The OP wanted to know whether a 1/2 was enough truck for a 30' AS, and IMHO, the answer is no. It is a compromised choice for a TV, and if the OP can live with the limitations of a 3/4 diesel, he will be much happier with the 3/4 ton truck as a TV in the long run. That said, the 1/2 truck is certainly the better all-around choice, if hauling a 30' AS is not its primary role.

[J. Morgan]

I don't have the patience to address that whole post, all I am going to say is that as a current owner of several one ton trucks, some of them diesel, I am more than happy with the way my 1/2 ton handles my Airstream.

I choose it over my bigger pickups, even the diesels.

It never makes me impatient or uncomfortable. It stops, it goes, it steers, and it pulls.

Not so long ago I used a nice Cummins powered one ton to haul some equipment from Miami to Little Rock, I weighed just over 26,000 lbs gross in a rather tall box trailer.

It was a great trip, the truck pulled lite the trailer was empty, but my 1/2 ton and 31' AS don't weigh half that, and it is much more aerodynamic.



1/2 Ton 4WD Truck, 72 Sovereign Hensley Arrow

[J. Morgan]

I was going to leave it there, but I cant help myself....

Using BoldAdventures rotor measurements I don't come up with 10%... I ran the figures earlier,,, but thinking I might have made an error I ran them again.

Diameter 13.230
Circumference 41.56


Diameter 13.855
Circumference. 43.53


Diameter 95.52%
Circumference. 95.47%

The number of pistons has little to no effect on caliper clamping force. The force is determined by the hydraulic ratio, (total volume of caliper cylinders per circuit divided by the master cylinder volume per circuit) not the number of pistons.

I will grant that the surface area of the pads can be a factor in the general braking force equation, but I don't feel like looking these up now. I suspect that the difference in pad surface between 1/2 ton and 3/4 ton brakes exceeds the 5% difference in rotor diameter, but I cant say for certain.


(Note 1; "per circuit" means that American cars have a front brake circuit, and a back brake circuit, each with a respective piston in the master cylinder)

(Note 2; above I state cylinder volume, the term should be exchanged with piston surface area and or piston displacement as applicable)

1/2 Ton 4WD Truck, 72 Sovereign Hensley Arrow

[moosetags]

We tow our Airstream with a 2011 one ton Duramax single rear wheel. As we tow the Airstream with our truck camper rig, we need a one ton diesel to do the job. Our Outfitter pop-up truck camper weighs about 3,200#, making the tow vehicle 11,600# towing a 7,400# Airstream. We travel grossing right at 19,000#.

Between the truck camper in the bed and the hitch weight on the receiver, we are right at the one ton's cargo capacity. I also think that diesel is an absolutely necessity for this kind of load.

Brian

[J. Morgan]

I tow up to 26k with Ford one tons with V10s.

My DMaxes will out pull the Fords up St. Augustine Pass when they are running right,,, but...

My Ford gas motored trucks have proven more reliable and a lot cheaper to fix when they do break.

We had to put a motor in one of the Fords, the cost for a reman long block was $3,300 plus tax.

You can barely get the hood open on a DMax for $3,300. I have been kind of disappointed with my DMaxes.

Turbos and head bolts have proven the most problematic with my DMaxes, that and one of them never has run right past the first 20k miles, even the dealer could never get one of them to pull right. The other one pulls hard though.

1/2 Ton 4WD Truck, 72 Sovereign Hensley Arrow

[moosetags]

We also have a 6.0 gas 3/4 ton Suburban that we tow the Airstream with. It has always done OK, but it doesn't pull uphill anywhere near as well as the Duramax even with it's heavy load.

The 2500 Suburban is a 2005 with 140,000 miles on it. The Duramax is a 2011 with 80,000 miles. So far, all we have done is service it.

Brian