Air bags -vs- Sumo's

I have a 2018 w/towing and off road package and am/was experiencing bottoming out when going over a bump. The severity has decreased with shock replacement but is still there going over a bigger bump. I had been thinking of adding an air bag setup until joining this forum and now SumoSprings has thrown it's hat into the ring! I do not currently do any towing and if I do in the future it will be a small travel trailer. So right now I am driving around town with only a hard bed cover, bed mat and gas tank half full most of the time.
Are there any preferences/recommendations from the pros on here as to which one to go with? Thanks for the assist!

 

I don't know the setup in later model Tundras, but when mine was bottoming out without weight in the back, it was because my leaf springs were shot. But those were 20 year old springs. Not sure why your suspension would be blown out if you don't tow.

I think the blue Sumos would work well for you. Other things would work too, but at least as far as my experience goes with older trucks, airbags are only for people towing/hauling heavy weight.

But first I'd say always make sure your base suspension is in good shape. Covering up trashed leaf springs with Sumo Springs or airbags isn't the right approach.

For what they are Sumos are expensive. But I guess everything is. The blue Sumos worked great for me with my trailer, when I just had about 300 pounds tongue weight plus my topper and gear in the back. Once I went to a 900 pound slide-in camper, I needed airbags.

 

Roadmaster Active Suspension is the best bang for buck

 

Interesting…

Honestly, I don’t think you are experiencing the rear suspension bottoming out. Perhaps you can post some picture of your current springs, but I’ll tell you why I don’t thing it’s bottoming out - but rather the spring rate is increasing too rapidly from worn/sagging primary stages in the leaf spring.

Sorry if I get a little long winded, but basically your rear leaf springs are two stage progressive springs. The main leaf and two supporting leaves compose the primary stage; because of the two additional leaves, the spring rate is progressive, but these three springs together determine ride height and ride characteristics for normal driving including up to 600 or 700 lbs of payload.

The second stage of the leaf spring is that big fat overload spring that sits at the bottom of the spring stack. When you exceed the capacity of the primary stage - either by weight or travel (hitting a large bump) - the primary spring stage engages the secondary spring stage (the overload) and spring rate ramps up incredibly fast. Off the top of my head, the overload takes 4 or 5 times the weight to deflect an inch as the primary stage. This great for heavy loads, but here is the problem…

When your primary leaf springs start to sag, they rest on the overload or are very near it at regular ride height. Whenever you hit a decent sized bump, that overload is engaging and it feels like you are bottoming out. But you aren’t smacking the bump stop on the frame - the suspension is simply oversprung like a an empty dump truck. One of the neighbor kids bought a tundra last year and this was the case: it rode like it was on the bump stops because the springs were sagging on to the overload spring.

Adding airbags or Sumo’s is only going to increase the spring force and make the ride worse. New shocks help a little, but they need time (which to a shock simply means piston stroke/travel) to mitigate and dampen the spring forces.

So what ought you to do? Insect your leaf springs. I suspect they are shot and need to be replaced, so new leaves is the first (and probably best option, IMO). You could get by with an add-a-leaf if you are looking to add a little lift. RAS will improve the ride for the same reason - it will lift the primary stage off of the overload.

Personally, I removed the overload entirely, added an additional spring to the primary stage, and installed airbags in place of my overload spring. My bed is pretty loaded up most days and I tow regularly, so this option worked best for me. I purchase my ‘21 used knowing the rear springs were sagging on to the overload and it rode rough! I arrived at this solution after several spring and shock swaps on my ‘13.

 

I swear tundra leaf’s almost come worn out from the factory

but that’s super cool, never thought about modifying my factory leaf pack by taking one out instead of adding an add a leaf

 

Thanks. I did a little write up for it here:

https://www.tundras.com/threads/air-bag-over-load-conversion.160551/#post-3968228

I need to update it but it is behaving as expected. Unloaded the bed for a couple of days and it was still very tolerable. Loaded most of my typical load out today and it rode great. Still able to handle heavy loads and trailers with ease, while maintaining ride height in all conditions. Only took me 12 years and a dozen setups in the old truck to get it right

 

That’s always how it is! I think I’ve swapped suspension on my truck 3 or 4 times now

 

I tow a little and load the bed up fairly often but I am not not maxing out my payload. I should have done airbags day one. Even new I would hit the bump stops more than I thought I should. I could see the marks (clean spots) where the bump stops made contact. This is about a 6000 pound tow with a couple hundred pounds it the bed with air bags.

 

Bingo!! Made in Mexico garbage designed for a smooth test drive and hauling groceries. So bad they included adjustable headlights!

 

~1,000 pounds in the bed. Perfectly level. Airbags. Great thing about airbags is when you don't need them, you can air them down to almost nothing, and it's almost like they aren't there. The Sumo Springs are always there. That helps with body roll around turns, but limits travel offroad more than aired-down airbags. It's all a compromise.

But if you just tow a trailer and don't have more than...I don't know...3-400lbs in the back? Sumos would be fine. With properly functioning leaf springs.

 

I have had the rear suspension looked at by a mechanic. The leafs still have a nice "arch" to them and are not broken. There is frame evidence, shiny/clean spot, of bottoming out. I have read complaints about weak Tundra leaf springs too. Maybe that's why they are $1K at dealerships! (Have priced them for $200 at ATS.) Like I said, I have only had this truck for a year and know nothing about how it was used by the first owner. The truck bed is in very good shape, no bed rail dents and just a few scratches inside. The receiver looks like it has never been used but that could be a cover up job. Is there a way or test that can tell me if the leaf springs are shot? I don't want to just throw money at this.
Thanks for all the help!

 

Post a photo of your leafs so we can see

 

Post a picture of the leaf springs as they sit with the vehicle weight on them. You shouldn't be bottoming with such a small load unless you go Dukes of Hazard on it or the springs are W shaped.

@joseph_womack beat me to it!

 

Also for that price I would just get the icon rxt leaf pack and customize the load to how you would like it

 

Maybe had a truckbed camper in it and flattened the junk springs or as many people do, added lift shackles without extending bump stop height and then hauled a load. That will ruin them after just one time because they go into a negative arch and it's game over.

 

He brings up a good point - stock leaves are ok, but aftermarket leaves may be a better option. Unfortunately, I have not found any decent aftermarket options that don't include a lifted stance, so if you are looking to maintain the rear ride height, you are limited there. Speaking of ride height, what do your rear fender's measure from the ground? And what tire size are you running? On stock tires and empty stock suspension, you would be ~39" if memory serves.

Another option to look in to would be something like Icon's 3 leaf add a leaf kit; they replace the two supporting leaves in the primary stage but retain the main leaf and overload (if desired). With a small load in the bed, they should net you around an inch of lift after settling. They are much less expensive than a full set of leaves, but require your main leaf to be in good working order. The same type of kit is offered from a few different vendors such as Wheelers, Deaver, etc. I used the Icon kit in one iteration of my suspension mods with good results. I still use it as part of the leaf pack on my '13.

Icon kit: https://iconvehicledynamics.com/acc...toyota-tundra-rear-spring-expansion-pack-kit/

Deaver kit: https://performancelifts.com/deaver-spring-toyota-tundra-tacoma-3-leaf-mini-pack-f85.html

 

That could definitely be the case for the OP. I suspect that was the case for my '21. Completely empty bed and the overloads were almost touching. I knew it when I bought it, and also knew that I would be replacing it.

 

If you are indeed bottoming, you should fix the springs. But in the mean time, Peery Bumps make a much softer, more progressive bump stop to replace the hard rubber factory one. I like them a lot on my rigs.





https://www.perryparts.com/category/toyota-tundra-2nd-gen

 

They are buttered toast! Not factory bump either.

 

Grab a pic of the shackles and post

 

Whoa there partner! Those bumpstops are NOT factory - they are Timbrens - also known as hockey pucks. Looks like the previous owner mounted them because your leaves are definitely sagging. Remove them ASAP and replace with something like the PerryParts bumps and your life will improve an hundred fold...

To elaborate - you have virtually no suspension up travel before you hit that giant rubber hockey puck. It's rated for something like 3000 lbs - good for something like a slide in camper.

Also, look at the how close the tips of the fat overload spring are to the leaves above it. Also look at the witness marks (rust spots) on the bottom of the longer leaf spring from the overload spring hitting it. That truck was loaded HEAVY.

Completely unloaded, your ride would understandably be garbage. Remove the giant bumpstops ASAP. Look in to replacing your springs, but seriously, your ride will improve drastically just from ditching the Timbrens.

 

Dobinson's 5+2 or 7 leaf pack is a great replacement option if you want a little lift. I have them on my truck with both RAS HD kit and yellow Sumo springs, but I have been known to not worry about the mule and load the wagon while keeping the headlights in focus and not bottoming at all. Rides great loaded or empty and handles as if on rails too. I used Ironman 4x4 greasable shackles and poly bushings for great longevity and easy maintenance. Be advised, those springs are heavy and awkward, so an extra set of hands won't hurt if you want to do a DIY upgrade.

 

This was my truck with about 1000 lbs in the bed including a camper shell and bed slide and heavy duty leaf pack (basically an extra leaf spring and thicker overload spring). Note the overload is very close to the longer springs, meaning there is a significant amount of weight in the bed. But more importantly, note how much MORE room there is between the bump stop and frame. There is barely any in your setup, which is the first problem.

 

Not certain, but those look identical to SDHQ lift shackles

 

Lift shackle, short bump stop height, boom...flattened springs. Seen this a thousand times, no exaggeration.

 

Well, looks like I have an upgrade in my future! I will be good-to-go when I hook up my tow. Again, thanks for all the advice. Maybe I can pay it back sometime!
Now what can you do about gas mileage?!? (LOL)

 

Super charge it and put tape on the gas gauge

 

Seperate accounts and wife's debit card with 2 gas cans in the truck so you can fill her car for her early on Sunday mornings while she sleeps in because you are a nice guy! Shhhh!!!