Rim & Brake Dimension Questions - Fiberglass RV

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Old 04-10-2012, 06:22 PM   #1
Senior Member
Name: Craig
Trailer: U-Haul
South Eastern Pennsylvania
Posts: 101
Rim & Brake Dimension Questions

In another thread I mentioned that I am preparing to replace the original suspension on my U-Haul CT-13 and asked about tire sizes.

A few additional questions concern the rims, offset, lug bolt pattern and brakes.

It looks like the most common lug pattern for 14 rims 5 x 4.5? I have seen 3 and 4 digit designations for lug patterns, would 545 be 5 x 4.5?

I gather that typically trailers use zero offset rims. I plan to use a Flexride axle and have copies of their data sheets that show the minimum distance from the edge of the frame attachment bracket to the hub face is 6.25, without brakes. That distance is just about what I need for the CT-13 to keep the tire in the same location in the wheel well with the change to zero offset rims however I will be adding brakes. I have been searching to find the dimensions of brake units but I am not having any success. Apparently Dexter brakes are used on the Flexride axles but I do not see any dimensions for the brake units.

Do the Dexter brake drums fit over the Flexride hub flange? Or does that get replaced with the brake assembly? I guess I am not searching correctly but I am not finding the drawings and dimensions I need to define the new axle / brake combination (Flexride axle with Dexter brakes).

As always, any help and input is most appreciated.

Craig T.

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Old 04-10-2012, 06:31 PM   #2
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Thomas G.'s Avatar
Name: Kinga DeRode
Trailer: For Sale Or Rent
Rooms to Let 50 Cents
Posts: 5,102
The brake drums are not free floating like those used on cars. The brake drum casting also holds the bearings in a single assembly.

You may find it useful to go to a local trailer parts / fabrication shop and look at the parts.

UHaul and Burro owners, join the UHaul Campers on Facebook. https://www.facebook.com/groups/529276933859491/
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Old 04-11-2012, 10:30 AM   #3
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Name: Russ
Trailer: Scamp 16' side dinette, Airstream Safari 19'
Posts: 588
One of the Flexride axle dealers should be able to set you up with compatible brakes and give you info on how the flange to flange dimension translates back to axle length. If you were to lay your stock 13" wheel and tire with its outer face laying on a flat surface and measure up to the mounting surface, and do the same with the 14" wheel and tire, you could then see if the offset is comparable. If the 14" is not a greater dimension you should be ok to fit under the wheel well. On my Scamp there is alot of inner clearance, but very close on the outside to the wheel well.
I may be doing the same swap, as my axle is 9 years old and doesen't have enough clearance up top to switch to 14's. My trailing arms are still angling down about 10 degrees when loaded, so the axle is not shot, but I would have to space it down about 1.5" to gain travel clearance.
Make sure to tell the Flexride guys how much your loaded trailer weighs, so they can get the proper spring rated axle. The axle is rated 125% of the laden weight. Verify the 125%, as I am senile and read this stuff a few weeks ago.
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Old 04-11-2012, 11:51 PM   #4
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Name: Ron
Trailer: 2008 13' Scamp
British Columbia
Posts: 325
I just started adding electric brakes to my Scamp 13 today. I bought my brakes from R and P.

There doesn't appear to be any difference between the two in terms of bearing location to the face with the wheel studs. The brake drum appears to occupy formerly unused space behind the original hub. Or to put it another way, it appears that the wheel remains in the same relative location.

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Old 04-12-2012, 04:11 AM   #5
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Name: Craig
Trailer: U-Haul
South Eastern Pennsylvania
Posts: 101
Thanks Ron. This is helpful to know.

Craig T.
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Old 04-12-2012, 04:49 AM   #6
Jeff Richardson's Avatar
Name: Jeff
Trailer: 1977 13-foot Scamp
Posts: 71
I'm currently modifying my 1977 Scamp frame to mount a Flexiride axle under it with the arms facing rearward. Originally the axle was mounted behind the drop floor with the arms facing forward. The new axle will be mounted so it goes under the drop floor.

I bought 7-inch Dexter brake assemblies and drums from etrailer.com. I was going to buy them locally but saved $100 by buying them online.

Shortly after I received them, I mounted them on the Flexiride spindles because I wanted to see if the hub face to hub face dimension would be the same as what it was with the idler hubs that came with the axle. To my delight it is the same!

I've attached seven pictures to this message so you can see in detail the Dexter 7-inch brakes on the Flexiride spindles. Just click on the thumblnail image to enlarge them.

The first picture shows the one-piece hub and drum on the spindle. I'm going to use my original wheels which are 4 on a 4-inch diameter hole pattern. They are still in good shape and I'd have to modify the spare tire mount on the back wall to mount the more popular 5 on 4.50-inch diameter hole pattern. I think my wheels will look good after re-painting them white and slapping on some baby moons and beauty rings.

The second picture shows the backside of the drum and the backing plate of the brake assembly attached to the Flexiride spindle arm. I had to buy the nuts to secure the backing plates on the arm. They did not come with the assemblies. I found an exploded view of the brake assemblies on the Dexter web site and it only shows a nut going onto the stud. I'd like to add a lockwasher but there aren't enough threads exposed.

I don't like the way the insulation of the wires is touching the backing plate as they pass through the hole. It could wear through with vibration and create a short circuit. There is a woven tube around the wires inside the brake assembly to protect them from the moving parts. Maybe I can slide it a little farther outside of the hole.

The third picture shows the large hex nut that holds the bearings on the spindle. It is 1.465 inches over the flats so a 1-1/2 inch wrench will fit it. I was expecting to see a cotter pin in between the slots on the castle nut. Instead there is a tang-type washer because these are EZ Lube spindles. I had no idea the Flexiride was an EZ Lube spindle. This is the first time I've seen these. I had to bend the tang out of a slot in the nut to get the nut to spin off.

The fourth picture shows the spindle, bearing and brake assembly after the hub has been removed. Since the axle is clamped upside down on two saw horses the magnet is up in this picture. Normally it is down when the axle is installed on the trailer.

I noticed the magnet is loose on a square-formed sheet metal shaft with a spring behind it. I have never seen or worked on electric trailer brakes before. Seeing how loose the magnet is I thought that it would rub on the inside face of the brake drum. After a little while it dawned on me that is how the electric brakes are actuated. When the magnet is energized with 12 volts it is attracted to the spinning hub face which pulls it and causes the brake shoes to expand against the drum.

There are shallow holes in the plastic or resin face of the magnet. These are wear indicators. When the holes go away the magnet needs to be replaced.

The fifth picture shows the inside of the brake drum so you can see the smooth face where the magnet rubs.

As soon as the UPS man delivered the hub and brake assemblies to me I opened the box and put an old 8-inch wheel on the hub to see how it fits. It is tight but it does seat on the hub face. This is critical. My trailer will be raised by the new axle and the 8-inch wheels and tires will allow me to get the Scamp into my garage through a 7-foot high door opening. Because this is a Flexiride axle I can adjust the ride height if needed in order to get it inside the garage.

The sixth picture shows the spindle with the hub and bearings removed. You can see the EZ Lube zerk fitting on the end of the spindle and the hole where the grease comes out just inside the seal on the hub. I'm not sure if I will use it. I think this feature is more important on boat trailers where the axles are submerged in water. Making sure the bearing cavity is full of waterproof grease would probably help keep water out.

The seventh picture shows the axle with the idler hubs that came with it. My axle is 63 inches hub face to hub face. The distance over the outside of the mounting brackets is 49 inches. This gives me 45 inches between the mounting brackets which is what the inside width of the Scamp frame is.

I ordered it with a 2000 lb rating. I had read that current 13-foot Scamp factory axles are rated at 2200 lbs. The original Henschen axle I just removed from this 1977 Scamp was rated at 1200 lbs.

I had been meaning to add this brake information to another discussion about Flexiride axles but felt is was more appropriate to this one. Here's a link to the other thread:

Anyone have experience with Flexride axles?

I hope this helps. Let me know if you need more information, pictures or measurements from my axle and brakes.

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Old 04-12-2012, 05:35 AM   #7
Senior Member
Name: Craig
Trailer: U-Haul
South Eastern Pennsylvania
Posts: 101
Thank you so much Jeff. Your description and photos are a huge help!

Now I really understand how the brakes install on the axle.

Your input is very much appreciated.

Craig T.

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