Big Brake kit.

[Commodore]

My wish is for a higher quality, better braking system with a smaller rotor, compact caliper, and stainless lines. It’d be really nice to be able to fit 16” rims without pretty of caliper clearance and no reduction in braking performance.

That's a big ask. Hard to make them smaller and maintain performance without spending a fortune on something like carbon ceramic rotors and those might not be a great idea for off road use. Ultimately you need the mass of the rotor to dissipate heat.

 

[viperlincoln]

In terms of the weaknesses of the the Grenadier for my use cases, since I frequently tow a 6500lb trailer in mountainous areas) the inability to do meaningful engine braking (like you could with a diesel) is probably the second most frustrating weakness of the vehicle (the most frustrating is the anemic fuel range, I am forced to plan on no more than 100 miles between fill-ups when towing, but the upcoming Long Ranger tank should solve this issue).

I did a trip ten days ago where on the way home I had a 7% grade for a very long time (about 4 miles iirc). My approach in those situations is to use the engine braking to keep the rpms right on the border before the rpm gage turns yellow, when it does I brake for a few seconds to get it about 1000 rpm lower, let off the brakes to let them cool as the vehicle speeds back to yellow, then rinse and repeat until I'm at the bottom of the hill. So far this seems to work fine, but its pretty stressful and if I am on single track, the vehicles behind me are probably getting frustrated.

As a result, I frequently debate whether I should sell the Grenadier and get a big diesel truck (like an F250 or Ram 2500) which would probably be worlds better for towing, but would not have anywhere near the trail ability once I get to my destination. I'm sure I would regret that when I wasn't towing so keep avoiding making that call, but....

Long intro to my question: I wonder if one of these brake kits would be useful to help remove some of that overheating risk and mental stress of mountain down-hills while towing?

in Europe we have a diesel engine.Then the ineos is amazing towing car.I don't understand why the diesel is not an option in Us.

 

[LRNAD90]

in Europe we have a diesel engine.Then the ineos is amazing towing car.I don't understand why the diesel is not an option in Us.

If I remember correctly, BMW wouldn't provide stateside certification, since they decided to pull BMW diesel options form the NA marketplace in 2018. I have an e70 X5 with the M57, awesome engine, damn shame we don't get the diesel option stateside!

 

[Commodore]

in Europe we have a diesel engine.Then the ineos is amazing towing car.I don't understand why the diesel is not an option in Us.

Because the VW diesel fraud that faked the federal emissions testing cost the manufacturer $15B in damages. BMW rightfully decided to steer clear of that potential mess and US consumers are afraid of foreign diesels.

 

[DaveB]

Nice. I’m not sure they are needed though.

I agree.
Brembo brakes are some of the best in the world and I have found the brakes on my Grenadier to be fantastic.
It is a 3 tonne truck so I don't drive it like a race car anyway.
Offroad there is engine braking and gears as well as hill descent control

 

[parb]

Because the VW diesel fraud that faked the federal emissions testing cost the manufacturer $15B in damages. BMW rightfully decided to steer clear of that potential mess and US consumers are afraid of foreign diesels.

The VW execs in charge of the diesel program are still fugitives from justice in the united states. Eiser left Germany to go on holiday in croatia and got arrested while they tried to extradite him to the US. As far as i can tell none of these guys, Eiser, Winterkorn et al can leave Germany without risking arrest and extradition. There is an interpol warrant out for their arrest, i just checked and they are still considered fugitives from the US justice system.

EPA Fugitives | US EPA

provides information about individuals who are wanted by the EPA after being charged and fleeing the jurisdiction

www.epa.gov

 

[LeeroyJ]

in Europe we have a diesel engine.Then the ineos is amazing towing car.I don't understand why the diesel is not an option in Us.

Yeah its sad, I 100% would have chosen the diesel if it was available. That being said, the petrol is quite peppy and responsive (and very thirsty) when I'm not towing.

 

[LeeroyJ]

I agree.
Brembo brakes are some of the best in the world and I have found the brakes on my Grenadier to be fantastic.
It is a 3 tonne truck so I don't drive it like a race car anyway.
Offroad there is engine braking and gears as well as hill descent control

Towing a ~6500lb trailer (with new good quality trailer brakes) from Ouray Colorado to Durango Colorado really changed my mind on the Grenadier's brakes (at least with the petrol engine and its poor engine braking). Despite me going much slower than the speed limit, not riding the brakes, keeping engine braking at ~5,000 rpm, and making sure the trailer brakes were carrying their share of the load, the brake fade was so bad that I had to take multiple breaks to let the brakes cool. The last time I pulled into a stop it took me about 200 meters to stop from 35 mph and most of that braking came from the trailer.

I have the Agile Big Brake Kit installed now but haven't actually towed with them yet. Around town though, they just feel so much more responsive. Better braking with faster response and better pedal feel.

The two piston front brakes and one piston rear are just not adequate for the towing loads the Grenadier is rated at. Sadly, it is only a matter of time until someone learns this the hard way.

Ouray to Durango

maps.app.goo.gl

EDIT - All that being said, I wish someone would create a brake kit for the rear axle that maintains use of the handbrake.

 

[Agile1]

Towing a ~6500lb trailer (with new good quality trailer brakes) from Ouray Colorado to Durango Colorado really changed my mind on the Grenadier's brakes (at least with the petrol engine and its poor engine braking). Despite me going much slower than the speed limit, not riding the brakes, keeping engine braking at ~5,000 rpm, and making sure the trailer brakes were carrying their share of the load, the brake fade was so bad that I had to take multiple breaks to let the brakes cool. The last time I pulled into a stop it took me about 200 meters to stop from 35 mph and most of that braking came from the trailer.

I have the Agile Big Brake Kit installed now but haven't actually towed with them yet. Around town though, they just feel so much more responsive. Better braking with faster response and better pedal feel.

The two piston front brakes and one piston rear are just not adequate for the towing loads the Grenadier is rated at. Sadly, it is only a matter of time until someone learns this the hard way.

Ouray to Durango

maps.app.goo.gl

EDIT - All that being said, I wish someone would create a brake kit for the rear axle that maintains use of the handbrake.

A rear brake is not off the table with Alcon, it's just not an easy off-the-shelf part for them.

 

[Clark Kent]

Towing a ~6500lb trailer (with new good quality trailer brakes) from Ouray Colorado to Durango Colorado really changed my mind on the Grenadier's brakes (at least with the petrol engine and its poor engine braking). Despite me going much slower than the speed limit, not riding the brakes, keeping engine braking at ~5,000 rpm, and making sure the trailer brakes were carrying their share of the load, the brake fade was so bad that I had to take multiple breaks to let the brakes cool. The last time I pulled into a stop it took me about 200 meters to stop from 35 mph and most of that braking came from the trailer.

I have the Agile Big Brake Kit installed now but haven't actually towed with them yet. Around town though, they just feel so much more responsive. Better braking with faster response and better pedal feel.

The two piston front brakes and one piston rear are just not adequate for the towing loads the Grenadier is rated at. Sadly, it is only a matter of time until someone learns this the hard way.

Ouray to Durango

maps.app.goo.gl

EDIT - All that being said, I wish someone would create a brake kit for the rear axle that maintains use of the handbrake.

I'm interested in what's happening here. You clearly know what you're doing @LeeroyJ so this is me rambling trying to figure out what's going on. I'm not suggesting you're doing something wrong but it sounds like the trailer brakes are not optimal so there's a few things here you could check before jumping into a front brake upgrade.
I've added some extra fluff in here because it may be of use to others trying to set up and test their trailer/van electric brakes.

Sidebar: MadMatt did a downhill test recently to highlight the difference on brake temperature and performance between the use of gears and engine braking versus wheel braking only. It was dramatic.

In the USA the Grenadier is rated to tow 7716lbs. You're at ~6500lbs which is a decent load but within spec. Trailers above 3000lbs need hydraulic surge or electric brakes.

Q: Which type of trailer brakes do you have?

I also see some references to a requirement for brakes on all wheels for trailers above 6500lbs. I assume at ~6500lbs loaded your trailer is a tandem axle.

Q: Do you have brakes fitted on each wheel?

The tow rating relies on the vehicle and the trailer producing sufficient braking force to stop the vehicle and trailer, but a rating test may not consider sustained downhill braking performance (I don't know).

It sounds like despite your technique, the trailer is still pushing you down the hills. The vehicle brakes are overheating and fading because they're being worked hard without enough time to cool and recover.

Q: Have you considered a higher temperature/performance ceramic pad for your towing application? This might be a worthwhile upgrade without committing to a front brake upgrade. You can do rear pads also.

You say you have good quality trailer brakes and have checked that the trailer is carrying it's share of braking.

Qs:
1. How have you determined the trailer brakes are earning their paycheck?

2. If you're using an electric brake controller are you sure all brakes are operating?

A quick operational test can be done by: engine running; trans in park; handbrake on; trailer plugged; have an assistant apply and hold the brakes. Place a small steel object like a nut against each (cold) trailer brake drum. The drums should be lightly magnetised when the brakes are applied.
If you're using a Redarc Towpro the control knob may also change colour when the brakes are applied (model dependent).

3. If you have a Redarc style proportional controller, are you increasing the braking force before commencing the downhill sections?

Automatic (inertia) control mode creates a brake force according to how hard you brake (how much inertia is generated). If you're relying mostly on engine and gearing with a gentle but extended brake application to control speed, automatic mode will apply a corresponding light braking force so the trailer is not doing a lot of braking to assist you. Try manual mode and set a mid range brake force (50 to 60% point). You should be able to feel through the tow hitch when the trailer brakes bite. Set it so it's firm but not aggressively snatching. Increase the setting at higher speeds and weights.
On some controllers you can override automatic mode by pressing the button. You then get a brake force according to where on the scale the control knob is rotated to. That's a useful technique if you want a momentary extra stab of trailer brakes, like a slippery off-road downhill, or sudden trailer sway on the highway.
I have avoided mentioning specific Redarc model names like TowPro Elite because the US market has different models and features.

Brake effect and balance can be coarsely checked with a laser temperature scanner. If all trailer brakes are (1) working, and (2) working evenly, they should increase in temperature with operation and by approximately the same amount at each wheel. To do this test, first run the trailer on a flat grade for 20 minutes or so to let the wheel bearings and hubs heat up to normal temperature. Aim for minimal brake operation during the warm up. Stop and take a reference temperature reading at each hub and drum. Then do a series of normal stop brake tests. Emergency stops are not required.
Stop and test for an increase in temperature at each brake drum and look for a change in temperature with roughly the same temperature at each wheel. No step change in temperature means that brake is not functioning. A large variation in temperatures across the wheels (minus the starting temps), indicates that not all brakes are working at the same level. For a lower brake temperature this could be incorrect brake adjustment (shoe to drum clearance), a worn electromagnetic brake puck (e-brakes only), contaminated shoes or drum or worn or glazed brake shoes. For a higher temperature this could be a worn out or damaged brake puck (e-brakes), binding shoe linkage or damage to the puck running surface inside the drum (e-brakes). Note that a dragging brake would have shown up during the warm up phase readings.

 

[TCMColorado]

I'm interested in what's happening here. You clearly know what you're doing @LeeroyJ so this is me rambling trying to figure out what's going on. I'm not suggesting you're doing something wrong but it sounds like the trailer brakes are not optimal so there's a few things here you could check before jumping into a front brake upgrade.
I've added some extra fluff in here because it may be of use to others trying to set up and test their trailer/van electric brakes.

Sidebar: MadMatt did a downhill test recently to highlight the difference on brake temperature and performance between the use of gears and engine braking versus wheel braking only. It was dramatic.

In the USA the Grenadier is rated to tow 7716lbs. You're at ~6500lbs which is a decent load but within spec. Trailers above 3000lbs need hydraulic surge or electric brakes.

Q: Which type of trailer brakes do you have?

I also see some references to a requirement for brakes on all wheels for trailers above 6500lbs. I assume at ~6500lbs loaded your trailer is a tandem axle.

Q: Do you have brakes fitted on each wheel?

The tow rating relies on the vehicle and the trailer producing sufficient braking force to stop the vehicle and trailer, but a rating test may not consider sustained downhill braking performance (I don't know).

It sounds like despite your technique, the trailer is still pushing you down the hills. The vehicle brakes are overheating and fading because they're being worked hard without enough time to cool and recover.

Q: Have you considered a higher temperature/performance ceramic pad for your towing application? This might be a worthwhile upgrade without committing to a front brake upgrade. You can do rear pads also.

You say you have good quality trailer brakes and have checked that the trailer is carrying it's share of braking.

Qs:
1. How have you determined the trailer brakes are earning their paycheck?

2. If you're using an electric brake controller are you sure all brakes are operating?

A quick operational test can be done by: engine running; trans in park; handbrake on; trailer plugged; have an assistant apply and hold the brakes. Place a small steel object like a nut against each (cold) trailer brake drum. The drums should be lightly magnetised when the brakes are applied.
If you're using a Redarc Towpro the control knob may also change colour when the brakes are applied (model dependent).

3. If you have a Redarc style proportional controller, are you increasing the braking force before commencing the downhill sections?

Automatic (inertia) control mode creates a brake force according to how hard you brake (how much inertia is generated). If you're relying mostly on engine and gearing with a gentle but extended brake application to control speed, automatic mode will apply a corresponding light braking force so the trailer is not doing a lot of braking to assist you. Try manual mode and set a mid range brake force (50 to 60% point). You should be able to feel through the tow hitch when the trailer brakes bite. Set it so it's firm but not aggressively snatching. Increase the setting at higher speeds and weights.
On some controllers you can override automatic mode by pressing the button. You then get a brake force according to where on the scale the control knob is rotated to. That's a useful technique if you want a momentary extra stab of trailer brakes, like a slippery off-road downhill, or sudden trailer sway on the highway.
I have avoided mentioning specific Redarc model names like TowPro Elite because the US market has different models and features.

Brake effect and balance can be coarsely checked with a laser temperature scanner. If all trailer brakes are (1) working, and (2) working evenly, they should increase in temperature with operation and by approximately the same amount at each wheel. To do this test, first run the trailer on a flat grade for 20 minutes or so to let the wheel bearings and hubs heat up to normal temperature. Aim for minimal brake operation during the warm up. Stop and take a reference temperature reading at each hub and drum. Then do a series of normal stop brake tests. Emergency stops are not required.
Stop and test for an increase in temperature at each brake drum and look for a change in temperature with roughly the same temperature at each wheel. No step change in temperature means that brake is not functioning. A large variation in temperatures across the wheels (minus the starting temps), indicates that not all brakes are working at the same level. For a lower brake temperature this could be incorrect brake adjustment (shoe to drum clearance), a worn electromagnetic brake puck (e-brakes only), contaminated shoes or drum or worn or glazed brake shoes. For a higher temperature this could be a worn out or damaged brake puck (e-brakes), binding shoe linkage or damage to the puck running surface inside the drum (e-brakes). Note that a dragging brake would have shown up during the warm up phase readings.

Great job detailing trailer brake setup and trouble shooting. This deserves its own thread in the resources section.

 

[Clark Kent]

Great job detailing trailer brake setup and trouble shooting. This deserves its own thread in the resources section.

Thank you. I'd be happy to do that with a bit more top and tailing to make it standalone. Give it a few days and see what others think of my ramblings. One thing this place is not short of is opinions, mine included!

 

[LeeroyJ]

Thanks for the detailed response @Clark Kent - Here's the answers to your questions:

Q

: Which type of trailer brakes do you have?

I also see some references to a requirement for brakes on all wheels for trailers above 6500lbs. I assume at ~6500lbs loaded your trailer is a tandem axle.

Its an Imperial Outdoors X22. It can be viewed here.

Yes, it's a tandem axel with drum brakes at each wheel. I had the brakes serviced about 3,000 miles prior to the drive I mentioned above. I run it through a RedArc brake controller. You can see my post about installing the brake controller here. The brakes on the trailer are definitely working, in fact I was worried they would overheat first because I could "feel" the trailer pulling me back (as opposed to pushing me forward).

Q: Do you have brakes fitted on each wheel?

The tow rating relies on the vehicle and the trailer producing sufficient braking force to stop the vehicle and trailer, but a rating test may not consider sustained downhill braking performance (I don't know).

It sounds like despite your technique, the trailer is still pushing you down the hills. The vehicle brakes are overheating and fading because they're being worked hard without enough time to cool and recover.

Yes brakes on each wheel. I would be inclined to agree with you that its the trailer pushing me downhill because that makes the most sense. However, the reality is that the trailer is only "pushing" when I am solely engine braking. Once I put my foot on the brake, I can feel the load switching from the trailer pushing, to it pulling (i.e. it is helping to slow the Grenadier down). I was worried the trailer brakes would overheat first, but it was 100% the Grenadier brakes that faded fastest. I don't know why. It doesn't seem to make sense to me.

Q

: Have you considered a higher temperature/performance ceramic pad for your towing application? This might be a worthwhile upgrade without committing to a front brake upgrade. You can do rear pads also.

You say you have good quality trailer brakes and have checked that the trailer is carrying it's share of braking.

I didn't try other pads, but I did already have the Agile (Alcon) brakes installed in front. I just haven't towed with it yet since installation. Around town though, the brakes feel much more responsive.

Qs:
1. How have you determined the trailer brakes are earning their paycheck?

2. If you're using an electric brake controller are you sure all brakes are operating?

A quick operational test can be done by: engine running; trans in park; handbrake on; trailer plugged; have an assistant apply and hold the brakes. Place a small steel object like a nut against each (cold) trailer brake drum. The drums should be lightly magnetised when the brakes are applied.
If you're using a Redarc Towpro the control knob may also change colour when the brakes are applied (model dependent).

I answered most of this already above. I did adjust the trailer brakes (increasing their contribution) at the top of the hill, and again during one of my cool down stops. I can absolutely tell they are working, I can feel them pulling the Grenadier back when braking.

Automatic (inertia) control mode creates a brake force according to how hard you brake (how much inertia is generated). If you're relying mostly on engine and gearing with a gentle but extended brake application to control speed, automatic mode will apply a corresponding light braking force so the trailer is not doing a lot of braking to assist you. Try manual mode and set a mid range brake force (50 to 60% point). You should be able to feel through the tow hitch when the trailer brakes bite. Set it so it's firm but not aggressively snatching. Increase the setting at higher speeds and weights.
On some controllers you can override automatic mode by pressing the button. You then get a brake force according to where on the scale the control knob is rotated to. That's a useful technique if you want a momentary extra stab of trailer brakes, like a slippery off-road downhill, or sudden trailer sway on the highway.
I have avoided mentioning specific Redarc model names like TowPro Elite because the US market has different models and features.

I think you are right here, when engine braking alone (i.e. foot not on the brakes) I don't think the trailer brakes are contributing at all. I think on the petrol version, the engine braking is so weak that it doesn't cause the inertia sensors to recognize braking.

I guess the only way I could get the trailer brakes to contribute during engine-braking-only times is by pushing the button occasionally. But pushing the button seems to be all or nothing, not progressive (I can actually lock the trailer brakes if I hold it forcefully and long enough).

Brake effect and balance can be coarsely checked with a laser temperature scanner. If all trailer brakes are (1) working, and (2) working evenly, they should increase in temperature with operation and by approximately the same amount at each wheel. To do this test, first run the trailer on a flat grade for 20 minutes or so to let the wheel bearings and hubs heat up to normal temperature. Aim for minimal brake operation during the warm up. Stop and take a reference temperature reading at each hub and drum. Then do a series of normal stop brake tests. Emergency stops are not required.
Stop and test for an increase in temperature at each brake drum and look for a change in temperature with roughly the same temperature at each wheel. No step change in temperature means that brake is not functioning. A large variation in temperatures across the wheels (minus the starting temps), indicates that not all brakes are working at the same level. For a lower brake temperature this could be incorrect brake adjustment (shoe to drum clearance), a worn electromagnetic brake puck (e-brakes only), contaminated shoes or drum or worn or glazed brake shoes. For a higher temperature this could be a worn out or damaged brake puck (e-brakes), binding shoe linkage or damage to the puck running surface inside the drum (e-brakes). Note that a dragging brake would have shown up during the warm up phase readings.

Thanks I'll give this a try next time I tow. I don't have a temp scanner, I'll need to order one. I do however put my hand on the trailer hubs each time I stop for fuel, I do this just as an unscientific way to make sure the wheel bearings aren't getting too hot. The all four have the same approximate temperature.

I appreciate the effort you put in this reply!
[/QUOTE]

 

[Tom109]

I didn't try other pads, but I did already have the Agile (Alcon) brakes installed in front. I just haven't towed with it yet since installation. Around town though, the brakes feel much more responsive.

Sounds like a good upgrade for towing. Your experience reminds me of towing with my D1, and then towing with a RRC (and vastly superior braking).

 

[Clark Kent]

Thanks for the detailed response @Clark Kent - Here's the answers to your questions:


Its an Imperial Outdoors X22. It can be viewed here.

Yes, it's a tandem axel with drum brakes at each wheel. I had the brakes serviced about 3,000 miles prior to the drive I mentioned above. I run it through a RedArc brake controller. You can see my post about installing the brake controller here. The brakes on the trailer are definitely working, in fact I was worried they would overheat first because I could "feel" the trailer pulling me back (as opposed to pushing me forward).

Yes brakes on each wheel. I would be inclined to agree with you that its the trailer pushing me downhill because that makes the most sense. However, the reality is that the trailer is only "pushing" when I am solely engine braking. Once I put my foot on the brake, I can feel the load switching from the trailer pushing, to it pulling (i.e. it is helping to slow the Grenadier down). I was worried the trailer brakes would overheat first, but it was 100% the Grenadier brakes that faded fastest. I don't know why. It doesn't seem to make sense to me.

I didn't try other pads, but I did already have the Agile (Alcon) brakes installed in front. I just haven't towed with it yet since installation. Around town though, the brakes feel much more responsive.
I answered most of this already above. I did adjust the trailer brakes (increasing their contribution) at the top of the hill, and again during one of my cool down stops. I can absolutely tell they are working, I can feel them pulling the Grenadier back when braking.

I think you are right here, when engine braking alone (i.e. foot not on the brakes) I don't think the trailer brakes are contributing at all. I think on the petrol version, the engine braking is so weak that it doesn't cause the inertia sensors to recognize braking.

I guess the only way I could get the trailer brakes to contribute during engine-braking-only times is by pushing the button occasionally. But pushing the button seems to be all or nothing, not progressive (I can actually lock the trailer brakes if I hold it forcefully and long enough).

Thanks I'll give this a try next time I tow. I don't have a temp scanner, I'll need to order one. I do however put my hand on the trailer hubs each time I stop for fuel, I do this just as an unscientific way to make sure the wheel bearings aren't getting too hot. The all four have the same approximate temperature.

I appreciate the effort you put in this reply!

[/QUOTE]

You've already done the BB front upgrade so that should help. Alcon and Agile know their game but it's a shame neither have published any data (that I can find) that includes deceleration tests measured with a brake force meter. But bigger is better, right?
I can see you're pulling a nice offroad RV camper. There's no info on Imperial's website about the type of wheel brakes used. I did see an instruction manual for a hydrastar actuator. Are your wheel brakes electric or electric-over-hydraulic?
It doesn't matter how the brake shoes get expanded but electric-over-hydraulic does make a difference with troubleshooting if the brakes are under-performing.
Electric brakes have wires passing through the backing plates.
Hydraulic brakes will have pipe or hose connections with a bleed screw on the backing plate and there will be an actuator/brake fluid reservoir mounted somewhere. The actuator might be controlled by your Redarc.

I have picked up something in your explanation of how you're using the brakes. I suspect, but tell me different, you're relying on the trailer brakes being applied automatically when you're getting pushed downhill? And you probably have the controller knob set too low.

"I think you are right here, when engine braking alone (i.e. foot not on the brakes) I don't think the trailer brakes are contributing at all. I think on the petrol version, the engine braking is so weak that it doesn't cause the inertia sensors to recognize braking."
"I guess the only way I could get the trailer brakes to contribute during engine-braking-only times is by pushing the button occasionally. But pushing the button seems to be all or nothing, not progressive (I can actually lock the trailer brakes if I hold it forcefully and long enough). "

Rehash:
The Grenadier unbraked towing capacity is 1653lbs. (USA).
The braked towing capacity is 7716lbs.

The factory brake package is rated for the vehicle GVWR plus an unbraked trailer up to 1653lbs. GVWR includes towball down weight but not the trailer weight.
Braking at a combined weight above GVWR +1653lbs without the use of independent trailer brakes will exceed the vehicle brake performance.
Therefore, if you attach a trailer >1653lbs the trailer brakes must contribute the balance of the braking force every time you apply the brakes.

In your scenario you're getting punted downhill by a heavy trailer. The combined mass is exceeding the vehicle engine and gearing brake effect and you're speeding up. The trailer is pushing forwards on the tow hitch). The Redarc controller will not apply the trailer brakes unless the vehicle brakes are operated. The controller waits for an electrical signal from the brake light circuit before it sends power to the trailer brakes. This signal is generated if the brake pedal is pressed by the driver or if active cruise control operates (where fitted).
The Redarc does not sense a load at the tow hitch by the trailer pushing against the vehicle (that's how hydraulic surge brakes operate). With an electric brake controller for the trailer brakes to operate at all the vehicle brakes must operate first.

So that gets the trailer brakes activated . The rest of the magic is getting them to apply enough brake force to assist the vehicle so the brakes can function normally

Redarc automatic mode (normal mode)
The controller has a deceleration sensor which is sensitive to inertial forces. It will automatically adjust the trailer brake force to approximate the brake force being applied at the tow vehicle, i.e.:
- you apply light braking to slow down during approach to an intersection. A small inertial force is generated in the controller and a small brake force signal is sent to the trailer brakes.
- you step hard on the pedal. A large inertial force is generated in the controller and a large brake force signal to the trailer brakes.
The force generated is in proportion to how hard you applied the brakes hence modern controllers are called 'proportional' brake controllers. In automatic mode the driver should feel a light tug when the trailer brakes first apply but then the pedal effort to slow down and stop should not be all that different when towing versus not towing. That's the trailer brakes automatically doing their share of the work.

Redarc manual mode (user-controlled mode)
Instructions for changing modes on the Towpro Elite are here.
Manual mode generates a fixed trailer brake effort regardless of how hard the brake pedal is pressed. It takes away the proportional signal generated by the deceleration sensor. The brake force is a factor of the knob setting between zero and ten on the dial. The numbers are just divisions between minimum and maximum effect.
User controlled mode is typically recommended for your long downhill scenario. You want a relatively high braking effort at the trailer to help wash off speed and keep the excess load off the vehicle brakes.

User controlled mode can also be applied as a manual override by pressing the controller button down. This is recommended when:
- descending slippery offroad slopes (higher braking at the trailer helps keep you pointing straight)
- highway sway. Immediate application of the trailer brakes (without the vehicle brakes applied) pulls the trailer back behind the vehicle. This must be done within a few seconds of the sway developing to be effective.*

The fix?
My recommendation is whenever you need to take on long steep descents:
- Switch your Redarc across to manual mode, set the knob to about 6 or 7 and use the brakes as required to control excess speed. Adjust the control knob to get a balance that feels about right.
- In case you're not already, use manual mode on the transmission to hold lower gears.
- Don't be too kind to the trailer brakes. They are typically less effective than vehicle brakes so they need to be worked a bit to get the most from them.
- Come down a hill in the same gear you would use to go up is a good rule of thumb for maintaining safe speed control but it can annoy anyone stuck behind you on a single lane road.
- If necessary, stop at the bottom to let the brakes cool and recover before continuing on your journey. Drums take longer to cool than discs. Where safe to do so, leave the vehicle park brake off while cooling so the rear inner pads don't stick to the hot discs.

MadMatt again:

View: https://youtu.be/BImBq9qJd4g?si=xvVypdNNsb3BYMhB

Redarc: https://www.redarcelectronics.com/u...lectric-trailer-brake-controller-effectively/

* I recently did another towing education refresher course because there is a lot to forget. The delivery team emphasised the importance of placing the brake controller button centrally in the vehicle and practicing how to put your finger on it quickly (including at night) so either the driver or passenger can operate the manual override in a genuine white-knuckle emergency. Their last point was: Educate your passenger including your spouse/partner what a calmly spoken "Press the f*ing button!!' means