Which Size Brakes?

[Section 8]

On a Torflex axle, using Dexter brakes:

If you can fit the 10 inch brakes, is there any reason not to specify them instead of the 7 inch?

Thanks.

[Alphacarina]

Added unsprung weight, which is never a good thing

Don't know if you can put the 10 inchers on any axle smaller than 3500 pounds - Are you using a 3500 pound axle?

Don

[Section 8]

No. I am looking at the #9, I think it is 2,200 pounds. Not being able to mount them would make this decision moot.

Unsprung weight is a good point. I am already going to have a 31 inch tire per side, why stick 3 more inches of iron in there.

[jimqpublic]

31" tire can exert a lot of torque on a wimpy 7" brake. Double check on the axle spec's but as long as you're running at least 13" trailer wheels (may be different for car wheels) I would suggest 10" for an offroad or heavy trailer. The 10"x2-1/4" drums have more than double the swept surface of the 7"x1-1/4" drums.

[Alphacarina]

No doubt they are twice the brakes that the 7 inchers are . . . . but I don't see a 2200 pound trailer needing twice the brakes

Maybe you CAN mount them, but my browsing of the Dexter website shows them only offered on 3500# and larger axles

If you're offroading, I would look to the stainless disc brakes if you feel you need something more than the 7 inchers

Don

[madjack]

Don, is correct(I believe) Dexter only offers the 7" brakes on the 2200# axle...............................

[jimqpublic]

Okay, good points.

I really appreciate the fact that my 2400 pound (loaded) Chalet has brakes rated for 3500 pounds when I'm going down the 26% grade on Sonora Pass here in California. Plus I wouldn't want to be that close to the spring and axle rating.

If the trailer really ends up hitting the road at 2000 pounds I would absolutely want 10" brakes, especially if you're towing using a smallish vehicle. On the other hand if the loaded weight is more like 1500 pounds it seems the 7" brakes are plenty.

As you step up through the sizes of running gear they add nice features like longer arms, bigger brakes, sealed hubs, etc. I guess it would be silly though to put an axle rated at triple the weight of the empty trailer just so you don't have to repack the hubs.

Question for the experts: Dexter shows the #9 as spanning 1000 to 2200 pounds, and the #10 from 2300 to 3500. If you order a #10 and specify that it will be used for 2300 pounds GAW do they cut the rubber short to give an appropriately soft ride?

[madjack]

...............Question for the experts: Dexter shows the #9 as spanning 1000 to 2200 pounds, and the #10 from 2300 to 3500. If you order a #10 and specify that it will be used for 2300 pounds GAW do they cut the rubber short to give an appropriately soft ride?

...yes, but that is somewhat of an assumption on my part, based on my talks with the folks at Dexter and SouthWestWheel(Flexiride)..............................
madjack

[brian_bp]

While excessively heavy hardware (especially unsprung) is not a good thing, once the 31" tall tires are selected I think you're committed.

Not only does the larger drum give you more swept area, it also fixes the leverage problem: a 7" drum with a 21" tall tire means the brakes work at a 3:1 mechanical disadvantage - the actual force at the tire/road contact is only 1/3 of the force at the brake linings. With a 31" tall tire, you need the 10" brakes just to keep the same 3:1 mechanical disadvantage... a 7" brake would be worse than 4:1.

My 10" Dexter brakes in a not-so-tiny travel trailer cannot deliver enough force to lock the tires with a trailer weight of about 3000 lb... so I think trailer brakes are generally pretty marginal, and if were selecting new hardware I would want to be sure mine were big enough. I have heard of other owners of my model of Boler trailer switching to the next level up of hardware to get the 12" brakes... the same idea as Section 8 is considering, scaled up to a different range for the larger trailers.

Yes, 10" brakes in the Dexter line are used with the 3500 lb hardware. And yes, several sources report that the lower ratings within a hardware range are accomplished with shorter rubber rods, although I have not seen this detail from Dexter themselves.

You could check the Dexter catalog, but I think both #9 and #10 Torflex arms are the same length (maybe 6").

[Skammers]

Dexter 7 inch break on left and EZ Loader 7 inch break on the right side. The drums appear to fit either one.

[Section 8]

Ugh. Building a trailer started out fun.

In the catolog/s only the 7 inch brakes are listed on the smaller axles. And both #9 and #10 axles have 6" arms.

I will have to call Dexter and figuer out weather or not the larger brakes can be fitted to the smaler axle (since they don't specify either in the catolog, I would guess against it). THe trailer, completely loaded, I am intending to weight 1200 pounds. There will be alot of room for acuiring extra junk to take along. THis is beside the once or twice a summer week or so trips where you pack heavy anyway. Using the recomendations of this site, by specifying a heavier axle than needed at 2000 pounds. So a 2300# axle wouldn't be that much of a stretch I guess.

I will be pulling with a Wrangler Unlimited Rubicon (the 2 door), so I can technically build a pretty heavy trailer, but for safety's sake, a 12v charging system, parking brakes, and the ease on decending steep loose hills with the traler not trying to jackknife I wanted brakes.

For the poster who mentioned not being able to lock the brakes, I asume that this was on pavement? Have you tried hitting the brake controller to see how mch power they have? Are they really weak?

I would really like the ability to stop on steep loose hill with everything digging furrows in the surface if it has to come to that, so with 31 inch tires it sounds like I have to get 10 inch brakes to accomplish the the hill holding that I want.

As far as the disk brakes go, I don't know anything about those. However, with my remedial understanding of surge brakes, they won't work backing down a hill, and they wil tend to push the jeep more and more the farther from following directly behind the jeep the trailer is when you apply the brakes since it has to push on the ball to actuate the brakes. The farther the trailer is off center, the closer it is to being jack knifed already, adding a rotation to the jeep that will aid this in occuring doesn't sound like a good idea. This is only my understanding, if its wrong, let me know.

Thanks to all.

[Alphacarina]

More points to ponder

After several lengthy discussions with an engineer at Dexter when I was building my boat trailer, they don't recommend you to use torsion axles unless the axle capacity is pretty near the loaded weight of the trailer. I was considering whether to use 2 or 3 of their 5500 pound axles and when we discussed my maximum weight (~8,000 pounds for the boat and ~3,000 pounds for the trailer) they strongly advised me to go with just 2 axles, as adding a third posed several problems, one of which was that it would ride terribly because the load wasn't heavy enough for 3 axles rated at a total of 6,500 pounds. 11,000 loaded pounds for 2 5500 pound axles was considered as 'perfect' by the engineer

For 1200 pound trailer pulled by a Jeep, I wouldn't bother with brakes at all as even descending steep grades, the Jeep will brake the trailer more than adequately just by selecting a lower gear. If you really want brakes (and I understand that completely) the 7 inch brakes recommended for the axle which suits the trailer load will be more than adequate in every regard - 10 inch brakes on a less than 2,000 pound trailer is really overkill, especially when you consider that probably more than half such trailers today are running no brakes at all

I regularly pull 1200 pounds with my smallish car (Mazda Protege 5) without brakes and have (so far) never felt I needed them. If I got above 1500 pounds with that car I would probably feel differently, but I've never towed anything that heavy. My utility trailer has a 3500 pound axle and the trailer capacity is rated at 2,000 pounds and there wasn't a single trailer on the lot when I bought it in that weight range that even offered brakes

I would buy the axle which is correctly rated for your load and then go with the brakes designed for that axle and not worry about it - It's all designed (by someone more talented than any of us) to work well together

Don

[brian_bp]

For the poster who mentioned not being able to lock the brakes, I asume that this was on pavement? Have you tried hitting the brake controller to see how mch power they have? Are they really weak?

That's me.

Yes, the test condition is on pavement.

This is a discovery from the controller setup procedure. The standard procedure calls for applying the trailer brakes with full application of the manual lever on the controller, while not touching the vehicle brakes. When this is done at the right controller gain setting, the trailer brakes should be on the verge of lockup, since it corresponds to the controller asking for maximum braking effort.

For the trailer to do its share of braking under normal conditions, I found that I need to use a gain setting which leads to about 7 volts to the brakes at full effort; however, even at much higher settings (and thus closer to 12 V), the brakes are never effective enough to overcome the tire traction... they're fine for normal conditions but there just isn't enough brake for the extreme.

My tires are only 26" overall diameter (P205/75R14).

To be fair, I first found this with brand new complete brakes (drums, shoes, magnets... the whole kit). Maybe now that they are worn it they're more effective.

[brian_bp]

... with my remedial understanding of surge brakes, they won't work backing down a hill...

True... any surge ("overrun" in Europe) system will not work in reverse. Many proportional electric controllers will not, either (except with the manual lever), although decent units (e.g. Prodigy) will.

... and they wil tend to push the jeep more and more the farther from following directly behind the jeep the trailer is when you apply the brakes since it has to push on the ball to actuate the brakes. The farther the trailer is off center, the closer it is to being jack knifed already, adding a rotation to the jeep that will aid this in occuring doesn't sound like a good idea...

Any trailer will push on the tug while braking. The tug carries some of the trailer weight on its hitch (such as the rule-of-thumb 10%), and should do about the same proportion of the braking for the trailer, and should be able to handle this proportion of force in the direction the trailer is pointing.

If you set electric trailer brakes too aggressively, they try to do too much and yank back on the tug, which is bad. I believe that the only time a trailer should pull on the tug by braking is when you manually apply the control, which I've never needed to do.

[brian_bp]

After several lengthy discussions with an engineer at Dexter when I was building my boat trailer, they don't recommend you to use torsion axles unless the axle capacity is pretty near the loaded weight of the trailer. I was considering whether to use 2 or 3 of their 5500 pound axles and when we discussed my maximum weight (~8,000 pounds for the boat and ~3,000 pounds for the trailer) they strongly advised me to go with just 2 axles, as adding a third posed several problems, one of which was that it would ride terribly because the load wasn't heavy enough for 3 axles rated at a total of 6,500 pounds. 11,000 loaded pounds for 2 5500 pound axles was considered as 'perfect' by the engineer

This is good information... but consider it in context. The Torflex problem in multiple-axle installations is that they - unlike leaf-spring systems with equalizer links - don't share load between the axles nicely. As a result, each axle needs to be over-spec'd to handle more than its usual share over bumps, and the load-to-capacity thing become an issue.

There's no load-sharing issue in a single axle trailer. Rubber or steel leaf, you still want the springs reasonably well matched to the load. You could get a Dexter D35 leaf-spring axle with only three leaves (5 is the full set), or a Dexter Torflex #10 with the shortest rubber rods, and in either case you have an axle sprung for about 2300 lb.