SmithCo SX3, SX4, SX5 or SX6: which configuration fits your work?
Understand SmithCo axle counts, compare four listed frame-and-tub configurations, and prepare the details that matter for a side-dump quote.
By Working Iron·5 min read
Published
The starting point
Yes—the number in SmithCo’s SX3, SX4, SX5 and SX6 model names identifies three, four, five and six trailer axles respectively. Use that as your starting point, then compare frame length, tub length, axle placement and installed options. More axles alone do not establish the right trailer or its legal payload for your route.
Read the model family, then the complete configuration
SmithCo’s SX range includes several axle counts. This comparison focuses on SX3 through SX6 because those families appear in Working Iron’s side-dump listings. They are part of a wider manufacturer range, rather than the only SmithCo trailers available.
A longer model designation adds useful context, but the written specification controls. For example, our SX5-49-38 listing describes a five-axle trailer with a 49-foot frame and a 38-foot tub. Do not assume every SX5 has those dimensions or the same lift-axle equipment.
Source references for this section are listed at the end of this guide.
Four configurations to compare
These are configuration examples described in individual Working Iron listings reviewed September 22, 2026. Dimensions and options are not universal specifications for each model family. Follow the listing links below for current details, then confirm availability and the complete build in writing.
| Model family | Trailer axles | Listed example | Frame / tub | Listed lift-axle detail |
|---|---|---|---|---|
| SX3 | 3 | SX3-42-34 | 42′ / 34′ | Third lift axle |
| SX4 | 4 | SX4-49-36 | 49′ / 36′ | First lift; fourth steerable/liftable |
| SX5 | 5 | SX5-49-38 | 49′ / 38′ | First and fifth liftable/steerable |
| SX6 | 6 | SX6-53-40 | 53′ / 40′ | First, second and sixth lifts |
Source references for this section are listed at the end of this guide.
SX3 and SX4: compare length and the axle package
SmithCo offers the SX3 in multiple lengths. The manufacturer associates shorter and mid-length builds with construction work and longer builds with line-haul use. That is a useful starting point for a conversation, not a guarantee of fit for a particular job.
For the SX4, SmithCo identifies lift and steerable axles as common options. Our four-axle example has a longer frame and tub than the featured SX3, but it is the complete build—not simply the extra axle—that you should compare.
Bring the dimensions of tight entrances, turning areas and unloading locations to the discussion. Ask how the proposed configuration works with those constraints and your existing tractor.
Source references for this section are listed at the end of this guide.
SX5 and SX6: axle placement deserves a closer look
SmithCo describes the SX5’s forward liftable/steerable axle behind the landing-leg area as a way to help distribute weight between the tractor and the rear trailer axle group. The featured SX5 listing specifies liftable/steerable equipment at both the first and fifth axles.
The OEM describes the SX6 with three fixed axles and three steerable lift axles. Our featured SX6 listing specifies a 53-foot frame and 40-foot tub, compared with the featured SX5’s 49-foot frame and 38-foot tub.
Ask for the axle layout, actual empty weight and proposed loaded combination. A large tub, a component rating and an allowable road weight describe different things. Confirm the usable payload for your equipment and routes with the manufacturer or a qualified transport professional.
Source references for this section are listed at the end of this guide.
Five details to put beside the model name
A useful shortlist records the same facts for every trailer. These are buying questions to take into the quote discussion, rather than operating instructions or a substitute for an approved configuration.
01
Material and tub
Name the material, typical load and loading method. Compare the specified tub construction and lining or other options, where applicable.
02
Frame and access
Record frame and tub lengths separately. Describe yard access, turning space and the receiving site.
03
Axles and suspension
Confirm spacing, fixed/lift/steer positions, suspension, tires and controls. An option shown on one listing is not standard on every trailer.
04
Tractor and connections
Provide the tractor configuration. Ask for the hydraulic, electrical, air and coupling requirements for the exact build.
05
Quote inclusions
Identify the tarp, controls, wheels, accessories, location and delivery scope. Compare written inclusions alongside the price.
Common SmithCo buying questions
01
Does SX4 mean four axles?
Yes. SmithCo identifies the SX4 as its four-axle side-dump model. The SX3, SX5 and SX6 correspond to three, five and six trailer axles.
02
Is an SX6 automatically the best choice?
No. Compare the work, route, tractor, dimensions and operating costs. A higher axle count alone does not establish a better fit or legal payload.
03
Are all trailers in one family identical?
No. Frame and tub lengths, lift/steer arrangements and installed equipment can vary. Compare the complete specification for the trailer being offered.
04
Where do I find current pricing?
Use Working Iron’s SmithCo listings for displayed prices and request a quote for the exact configuration. Confirm availability, inclusions and delivery scope before committing.
Source references for this section are listed at the end of this guide.
Send a buying brief that gets to the right questions
Start your inquiry with a model or listing link, then add the material you haul, operating states, tractor setup and any access constraints. If you are comparing configurations, say which tradeoff you are trying to resolve.
For example: ‘I’m comparing the SX4-49-36 and SX5-49-38 for aggregate work. Here are my operating states and tractor details. Please confirm the axle package, tub construction, available configuration, pickup location and delivery options.’
Put your shortlist to work
Browse the equipment, open a listing and use its inquiry form to ask about that specific configuration. Include the questions from your worksheet.
Sources & editorial notes (9)
Manufacturer references checked September 22, 2026. The comparison questions and worksheets are Working Iron’s buying guidance; they do not replace the exact equipment specifications, an inspection or an operator’s manual.