A proportional controller brakes the trailer as hard as you are braking the truck. A time-delay controller brakes it the same amount every time, no matter how hard you are stopping. That is the whole distinction, and everything else follows from it.
What the guides answering this question do not tell you is that they were written a long time ago. The pages currently ranking for it date from 2014, 2015 and 2017, and the market has moved twice since: proportional controllers that mount in any orientation, and controllers that do not mount in the cab at all. The choice is three-way now, not two-way.
They also get two specifics backwards. Within one manufacturer’s own range, the cheap time-delay unit covers more axles than the mid-priced proportional one, and works with brake types the proportional one is documented as untested for.
The two-way answer, first
| What it handles | Time-delay | Proportional |
|---|---|---|
| How it decides braking effort | A preset ramp over a preset time, identical every stop | Measures the tow vehicle’s deceleration and matches it |
| Knows how hard you are braking | No | Yes |
| Needs a sensor inside | No | Yes |
| Mounting orientation matters | No — mounts in any position | On traditional units yes; on three-axis units no |
| Needs levelling after fitting | No | No — modern units self-level |
| Behaviour in a gentle stop | Can over-brake — the trailer grabs | Light braking, matched to the stop |
| Behaviour in an emergency stop | Ramps at its fixed rate regardless | Full effort, as hard as the tow vehicle |
| One setting suits every stop | No | Yes |
| Cost | Lowest in the category | Mid to high |
| Suits | Light, occasional, flat-country towing | Heavy trailers, hills, frequent towing |
How each one actually works
Time-delay is a timer. When the controller sees the brake-light signal it begins increasing current to the trailer’s brake magnets, climbing to the output level you set, over the delay period you set. Two knobs, and neither of them knows anything about the stop in progress. Tekonsha describes its Brakeman IV output as ramping “at a fixed rate”; the user sets the level and the aggressiveness, and the controller repeats that ramp identically forever.
Proportional is a measurement. An inertial sensor reads how quickly the tow vehicle is slowing and drives the trailer brakes to match, so trailer braking rises and falls with your foot. Tekonsha’s phrasing for the P3 is braking “based on the intensity and rate at which you apply your tow vehicle’s brakes”.
The consequence is the part worth understanding, because it is the entire argument and it is a matter of mechanism rather than of quality:
The third architecture, which no ranking guide covers
Every page currently answering this question describes a dashboard box. The newest thing in the category is not a box at all.
CURT’s Echo plugs into the tow vehicle’s 7-way socket, senses with a triple-axis accelerometer, and uses your phone as the display and the controls. It is proportional in behaviour and shares nothing else with a traditional proportional controller: no dash real estate, no vehicle-specific harness, and it moves between vehicles in seconds.
There is a related move on the dash-mounted side. REDARC’s Tow-Pro Elite is also a three-axis design, which is what lets its module hide behind the dash in any orientation with only a knob showing — the orientation constraint that older guides treat as inherent to proportional controllers has been engineered out. That pairing is covered in Tekonsha P3 vs REDARC Tow-Pro Elite.
So “proportional” no longer describes one kind of hardware. It describes a behaviour, delivered three ways.
Three controllers, three architectures
| Model | Sensing | Where it mounts | Axles | Price | Buy |
|---|---|---|---|---|---|
| Tekonsha Prodigy P3 | Inertial sensor — axis count not published | Dash box, any vertical angle, must face the direction of travel | 1–4 axles | $$ | Check price(opens in a new tab) |
| Tekonsha Brakeman IV | None — a fixed time ramp, not a measurement | Anywhere within the driver's reach, any orientation | 1–4 axles | $ | Check price(opens in a new tab) |
| CURT Echo | Triple-axis accelerometer | Plugs into the 7-way socket — no dash unit at all | 1–2 axles | $$$ | Check price(opens in a new tab) |
Two of these three are made by the same company, which is deliberate — it lets the control type be compared without brand quality confusing the picture.
What the older guides get backwards
Two claims recur across the pages ranking for this query, and both are contradicted by the manufacturers’ own documentation.
“Proportional controllers have to be levelled.” They do not, and have not for a long time. Tekonsha’s P3 manual: “The P3 will automatically acquire the proper level setting. It will also automatically adjust as you travel up or down hills.” The real constraint on a traditional proportional unit is orientation — the P3 can sit at any vertical angle but must face the direction of travel. That is a different thing from levelling, and three-axis units do not have it at all.
“Time-delay is the compromise option, so it does less.” On the axis that matters — braking behaviour — yes. On fitment, the opposite is true, and it is demonstrable inside one manufacturer’s catalogue:
| Brakeman IV (time-delay) | Primus IQ (proportional) | |
|---|---|---|
| Axles | 1–4 | 1–3 |
| Electric over hydraulic | Yes | “Have not been tested for the use on electric over hydraulic brakes” |
| Mounting | Any orientation | Self-levels only within a 90-degree vertical range |
| Price | Lowest here | Higher |
Both are Tekonsha. The cheaper unit fits more trailers and more brake systems than the dearer one. That is not an argument for buying the time-delay controller — the braking behaviour is still the main event — but it is an argument for checking the model rather than trusting the category, and for ignoring anyone who tells you the control type settles compatibility.
Where the two types are identical
- Both need the same setup, at the same speed. Tekonsha and CURT independently publish a 25 mph road test on dry, level pavement: apply the brakes fully, then wind the setting to just below wheel lock-up. Both need redoing when the load changes.
- Both need warm brakes to be set correctly. Tekonsha: “Warm trailer brakes tend to be more responsive than cold brakes” — a quarter mile at 45 mph with light manual braking first.
- Both are 30 A devices in the models here, both are short-circuit protected, and both drive the same trailer brake magnets. Neither is doing anything exotic to the trailer.
- Neither compensates for badly adjusted trailer brakes. Tekonsha says so about its own boost feature: it is “not intended to be used to take place of trailer brake adjustment or repair.” If the brakes you have are behaving badly, that is a diagnosis rather than an upgrade — and the fault is more often a ground or a magnet than the controller.
- Both need a manual override you can reach, which constrains where the hardware goes far more often than the electronics do.
Which one, for what you tow
Proportional, if you tow a travel trailer or fifth wheel with any regularity, tow in hills, or the trailer is a significant fraction of the tow vehicle’s weight. This is most RV owners, and it is the honest recommendation despite costing more.
Time-delay, if the trailer is light, the towing is occasional and flat, or the budget is genuinely tight — and be aware you are choosing one compromise setting rather than buying a worse-built product. Also worth a look if there is nowhere in the cab that faces forward, though a three-axis proportional unit now solves that too.
The 7-way plug-in type, if you move one trailer between several vehicles, or you refuse to drill a dash. Only for one- and two-axle trailers, and only if you are comfortable that the interface is an app.
Once you have settled the control type, the five controllers we hold records for are set out side by side — with the axle and brake-type ratings that decide which ones are candidates at all.
Proportional, for regular or heavy towing
Tekonsha Prodigy P3
Brakes in proportion to how hard you are actually stopping. Four axles, electric-over-hydraulic on a menu setting, lifetime warranty.
Time-delay, and not a downgrade on paper
Tekonsha Brakeman IV
Same maker, same four axles, same 30 A, also does electric-over-hydraulic — and mounts anywhere, because there is no sensor to orient.
The third architecture nobody's guide covers
CURT Echo
Proportional sensing in the 7-way socket instead of the dash, with your phone as the display. Two axles only, and the app has to stay in the foreground.
Questions worth answering
What is the difference between a proportional and a time-delay brake controller?
A proportional controller measures how hard the tow vehicle is decelerating and applies the trailer brakes to match, so a gentle stop gets gentle trailer braking and a hard stop gets hard trailer braking. A time-delay controller ignores how hard you are braking: when it sees the brake signal it ramps output up to a preset level over a preset period, the same way every time. Tekonsha's own wording for its time-delay unit is that output "ramps up, or increases over a period of time, applying braking power to your trailer at a fixed rate".
Are time-delay brake controllers any good?
For light, occasional towing they are genuinely adequate, and they are not the crippled option the category's pricing implies. The real drawback is inherent to the design rather than to build quality: because output does not vary with how hard you are stopping, one setting cannot be right for both a gentle roll-up to a junction and an emergency stop. Set it for comfortable stops and it under-brakes when you need it most; set it for hard stops and the trailer grabs every time you slow down gently. The heavier the trailer, the more that compromise costs.
Is a proportional controller worth the extra money?
For most RV buyers, yes — but for the reason above rather than the reasons usually given. It is not that proportional controllers are better made, support more trailers or fit more vehicles; within Tekonsha's own range the cheaper time-delay Brakeman IV covers more axles than the dearer proportional Primus IQ and works with brake types the Primus IQ is documented as untested for. What you are buying is braking effort that tracks the stop you are actually making.
Which type mounts anywhere?
Time-delay, and it is a structural consequence rather than a feature someone chose. With no inertial sensor there is nothing that has to know which way is forward. Draw-Tite states it of the class — timed controllers "can be mounted in any position - horizontal, vertical, even turned upside down" — and Tekonsha says of the Brakeman IV that "there's no requirement that it be positioned in the direction of travel". Traditional proportional controllers do have an orientation constraint. Newer three-axis proportional units have removed it, which is the point of the third architecture below.
Do proportional brake controllers need to be levelled?
No, and this is the most persistent error in the older guides. Tekonsha's Prodigy P3 manual states "The P3 will automatically acquire the proper level setting. It will also automatically adjust as you travel up or down hills." Levelling is not an installation step. What a traditional proportional controller does need is to face the direction of travel — an orientation requirement, not a levelling one.
What is a wireless or Bluetooth brake controller?
A third architecture that the standard proportional-versus-time-delay framing does not describe. CURT's Echo plugs into the tow vehicle's 7-way socket, senses with a triple-axis accelerometer, and uses your phone as the display and control panel. It is proportional in behaviour but shares none of the dash-mounted installation. The trade-offs are real: two axles maximum, and CURT's manual warns the app "must be operating in the foreground" because running it in the background "may cause delays in braking response when using the manual override button".
Does a time-delay controller work with electric-over-hydraulic brakes?
Sometimes, and the answer does not follow from the control type — which is the thing worth knowing. Tekonsha's time-delay Brakeman IV "works with electric or electric over hydraulic braking systems". Its proportional Primus IQ is documented by Tekonsha as designed for electric brakes and states these controllers "have not been tested for the use on electric over hydraulic brakes". Same manufacturer, opposite answers, and the cheaper unit is the compatible one. Check the specific model.
How do you set the gain on each type?
The same way, at the same speed. Both Tekonsha and CURT publish a road test at 25 mph on a dry, level paved surface: apply the brakes or the manual override fully, then adjust the setting down if the trailer wheels lock and up if braking is weak, until it sits just below lock-up. Tekonsha adds a step almost no guide mentions — warm the trailer brakes first, a quarter mile at 45 mph with light manual braking, because "warm trailer brakes tend to be more responsive than cold brakes". Redo it whenever the load changes.
Can I tell which type I have?
Apply the manual override lever or knob while stationary with the trailer connected. Both types will send power to the trailer brakes. Then note what happens when you brake normally while moving: a proportional controller's display output will vary with how hard you press, and a time-delay controller's will climb to the same level at the same rate every time. On a proportional unit the manual usually also states that the vehicle must be moving for the automatic output to work at all.