RAS - What am I missing?

Ok, what am I missing about Roadmaster Active Suspension? I'm just not sold on them. I've literally added them to my cart a dozen times, but every time I dig in to the nitty gritty of how they work and what I'm gaining from them, I come to the same conclusion:

RAS won't make the spring pack stronger.

What do I mean by stronger? I'm speaking mostly of load capacity. For example, an Add a leaf will add more spring rate to the leaf pack and make for a stronger leaf pack. A new leaf pack will be tuned differently than stock but almost always be designed to carry more weight by increasing the number of leaves even if they are thinner. So they are stronger. Airbags don't necessarily make the spring pack stronger, but take load off the spring pack by adding a variable rate spring dependent on air pressure, so the end result is stronger leaf suspension. Sumos and the like do the same thing - take part of the load off of the spring and make for a stronger suspension package overall - the main difference being they are wheel travel dependent, making them more progressive.

So why do I say the RAS doesn't make the rear springs/suspension stronger? Every writeup, anecdote, testimonial, review, etc, says the same thing: I installed the RAS, it lifted the back end of the vehicle, now the rear doesn't *squat* when I hitch up a trailer. Sounds like it made a stronger spring, right? Nope. You are simply setting the suspension to a higher static ride height so that it doesn't sit as low at the end. I put asterisks around the word 'squat' because almost every tow vehicle review defines squat as the rear sitting lower than the front - NOT how much the rear end drops.

For nearly every review I've looked at that lists fender measurements before and after, the total suspension change after hitching up is almost identical before and after installing the RAS. It appears to simply add rake back in to the truck stance - JUST LIKE IT CAME FROM THE FACTORY - to limit suspension squat. That squat is exacerbated when we level the front of the truck and eliminate that factory rake (cuz only old men drive raked trucks). Heck, I'm guilty of it. I tow every week and have been running around 2" of lift in the front for the last year; I ran a little over and inch of lift for 100k miles before that. What did I end up doing last year to improve my towing experience? Searched like mad for a leaf spring solution and ended up adding strength and height to the rear leaf pack.

Restoring the rake improved the towing experience. That appears to be what the RAS is doing by adding tension to the spring curve instead of adding strength to the spring pack. Thus my conclusion that RAS doesn't add spring strength - it only adds suspension height.

Furthermore, that coil spring that is put under immense tension to recurve the stock spring is working against a huge leverage disadvantage. Since it is adding tension the curve of the spring it's not directly bearing any load. Leaf springs need a shackle to adjust for the difference in spring length as they go from curved to flat; the distance that that shackle travels is the only distance that the RAS has to act in. Compare that distance to the total wheel travel and you have the leverage disadvantage it has to act on.

Lets say the shackle is 4" long and is designed to swing a total of 22.5 degrees to make the math easy. You don't want the shackle going completely vertical since it might invert, and you can't go completely horizontal as it will hit the frame, so 22.5 degrees seems reasonable. It lets you start at say 17.5 degrees if inclination and end at 40 degrees before you might hit the frame. I think that gives you some 1.5" of travel. I've got a stock spring sitting hear that measures ~62" eyelet to eyelet and ~63.25" following the spring itself. It is a worn spring so we'll be generous and use the 1.5" travel.

If the rear suspension has ~9" of travel at the spring from full stuff to full extension. That's a a 6:1 leverage ratio that the RAS has to work against. That's a very inefficient way to add spring force to a leaf pack. The advantage is you only have 1.5" of travel at the shackle, so to preload the top leaf, you don't need a crazy amount of spring force on the RAS coil. The huge disadvantage is that in doesn't add much spring force through the suspension travel. You would need to use a coil spring preloaded with 1000's of pounds of force to affect an appreciable change in leaf spring rate. Thus, again, the RAS isn't making for a stronger spring - it just changes the starting ride height of the rear suspension.

I'm not saying they are a total waste. I can see how they help with spring wrap and anti-sway. But for towing and squat, they appear to be barely more effective than a block or extended shackle.

I'm not trying to knock the RAS system or disparage the system design or those who own them. I'm simply asking what I'm missing? They don't appear to do much of anything for towing.

 

I mean, you seem to have your mind made up and it doesn't sound like folks will be able to change it. Either order the RAS based on all the folks that have and love it, or go with something different that you will be happy with.

I personally love the RAS. I removed my rear sway bar when I put it on and it definitely rides a hell of a lot better. With the sway bar both sides would "jar" when I hit a bump or something on one side, not anything terrible but I always felt like I was tying my hands behind my back with the sway bar since it felt like the sides couldn't really act independently and instead both took impact together. With the RAS, I get the benefit of the anti-roll but the sides are free to move independently. I'm so much happy with my daily on road performance of the truck and this alone has made it worth while.

I've only used the truck once with the RAS with high loads. I agree that it squatted less, but to your point was that due to just starting "higher" or not? I didn't measure or weigh what I had, but it definitely felt like the difference in unloaded to loaded changed less then when I was without the RAS, so to me it felt like the truck didn't squat as much while loaded. But, the big difference was once driving. Pre RAS, once loaded down I could feel that I was heavy and the truck rolled more and didn't respond as well when hitting bumps or issues in the road. With the RAS, I really couldn't tell I had weight based on driving characteristics, yes the truck accelerated/decelerated slower, but I didn't notice more body roll and hitting bumps felt basically like I was unloaded. A few times I had to remind myself I was fully loaded cause I honestly forgot.

I like that you can also tune the RAS to your load if you go with the HD, as is you can tighten it up if you want or loosen it (to some extent) as well. Not as easy as air bags but you do have adjustability unlike with a new leaf pack (once you install them you can't change them). That's my 2 cents, should line up with all the previous info you've seen so I doubt it will change anything for you, but you got to do what you are happy and comfortable with. My only useful advice would be to hit up @memario1214 and talk about your needs and expectations. You know he won't bs you and will help identify the correct solution for your needs.

 

Again, I'm not trying to pee in anybody's cheerios. If I had made up my mind already, I wouldn't bring it up for discussion. I've spoken with Colton on several occasions and have purchased suspensions through him for both of my vehicles. He is one of the folks suggesting the RAS system, which is why I have been exploring the option.

Here is an example of what I'm talking about.

https://www.youtube.com/watch?v=BE3YAYLKWiI

At the 25% setting, the vehicle dropped the exact same amount from the same pallet in the bed - it just started at a higher static height.

I don't have an axe to grind with RAS by any means; I'm just failing to see the actual usefulness of it in combatting sag. The only ways I see to actually combat sag given the same initial ride height would be to increase the spring rate or bind the spring in a way that prevents it from deflecting - the latter putting more stress on the springs.

 

Nice find. Shame they didn't test at different settings.

 

RAS is an add a leaf, Just in a different form. It’s a coil instead. And it doesn’t just change your static ride height so it squats less, it changes your loaded ride height also, so it actually is squatting less. Is it the same as an add a leaf? No. Does it add spring rate? Yes.

 

If it makes any difference.
When I loaded the bed with about 900lbs of tile I didn’t get much sag and it drove very controlled. However prior to the ras it would sag dramatically and just felt like a ship wallowing around.

it’s the same with my trailer. Loaded down it wallowed and just felt a bit unnerving on windy roads etc but after the ras it is like it rides on rails with the loaded trailer.

Don’t know the mechanics of it but it just works. Yes I gained about an 1/2-3/4 inch of lift but the over all amount of sag is much less with it than without it.

and it stiffened up the rear significantly but not in a harsh way.

When I was buying my suspension Colton asked me specifically about the rear and I told him I alsready had the ras hd and he said that was basically their number one way to deal with the rear of the tundra.
I am a firm believer now.

 

I’m not sure that’s accurate. The coil itself doesn’t appear to act in conjunction with the spring pack like an add a leaf, coil, helper spring, air shock, etc. There isn’t a pivot for it cantilever, either. So I’m left to surmise that it simply binds the top leaf spring. The coil tension just varies the amount of bind and adjusts for the leaf spring length as it flattens out. This makes the forward half of the leaf spring flex more; some OE’s bias the axle mount forward or rearward off the spring center to adjust the spring curve for a cushier ride or less squat when loaded. But this appears to simply put loads more tension on one half of the spring than the other.

Once that spring flattens out, the coil can’t add any more spring force to the system, so it would appear to only add preload and not spring rate like an add a leaf or more progressive pack, as illustrated but the video above. The latter would add an increasing spring force with increasing load whereas the RAS doesn’t appear to behave well with heavy loads as they suggest to avoid towing ‘at the extreme ends’ (gonna have to look up that paraphrased quote but it was a RAS executive in an interview).