To help folks spot and show a "vintage" of the Sunline bumper, see here
The mounts on the camper vary pending model and frame size. This is the mount is on the larger campers with I shape main frame rails. The slotted bracket is welded to the frame.
Then... the bumper. It is made like this on purpose to only hold enough weight and once exceeded it will literally bend backwards or tear off. This same setup was on my T2499 and the bigger T310SR
Here is breakaway plate
That small thin plate ~ 1/16" thick, is welded to the 4 x 4 tube bumper. There are carriage bolts that start inside the bumper protruding outwards. There are holes in the 4 x 4 OD tube so the bolt only holds the thin 1/16" plate. When the bumper is bolted up to the camper, this 1/16" thin plate acts like a breakaway device. When the load on the bumper is exceeded, this plate will bend in the center allowing the bumper to twist backwards with the weight. The larger the weight, the more this plate setup fails to the point of complete tear off.
Now why did they do this? I do not have this confirmed by the factory folks but here is my deduction on why. Sunline was very good about creating campers that are properly balanced with good weight distribution on the tow ball to create a stable towing camper. Adding weight to the back of the camper can change the loaded tongue weight and when the weight gets high enough, it can create an unstable towing camper. Since there are many floor plans and people do not all load their campers the same or put gear in certain places, they just declared, no more weight on the rear bumper than 100# which is barely enough to hold the spare tire.
The bumper is intended to help in rear collisions. The push is all towards the camper, not backwards. This break away mount allows the bumper to act as a bumper in a rear collision but limits the amount of weight added which may and can affect towing stability.
Over the years and on this forum we have seen at least 2 vintages of this break away bumper. The one I show is the newer/latest vintage. Do not know the model years, I speculate later 90's all the way to 2007 models. I think it was Steve Collins who had a camper with the older style as someone had pics showing it. The concept was similar but accomplished different. And then some may have a bumper of very long ago made differently before Sunline caught on about people adding too much weight on the back of the camper.
We have also seen some bumpers that the prior owner did weld the bumper to the main frame rails. This was not Sunlines doing, but someone modifying it. As we have many new folks to the forum or even some of us long time folks, we may or may not know unless you bought your Sunny new, is this the factory setup or did someone modify it?
So this is some on the history of the bumper and the concerns of weight on the back of the camper. Not all floor plans have the same weight and balance to the camper. Some floor plant have very low effect by weight on the rear of the camper and some have a very large issue with much weight back there.
And then there is the bounce factor. Most Sunline TT's never had shocks on them like most all TT's. The lack of shock extremely aggravate a very large road caused bounce on a bike rack some 4 to 8 feet behind the rear axle of the camper. That bounce and impact can kill a bike rack or your mount if not accounted for.
Hope this helps
Current Sunlines: 2004 T310SR, 2004 T1950, 2004 T2475, 2007 T2499, 2004 T317SR
Prior Sunlines: 2004 T2499 - Fern Blue
2005 Ford F350 Lariat, 6.8L V10 W/ 4.10 rear axle, CC, Short Bed, SRW. Reese HP trunnion bar hitch W/ HP DC
Google Custom Search For Sunline Owners Club