Building a Trailer and Towing with the USDM SJ Forester

[baipin]

I'm looking to fab my own trailer (it's by far the cheapest option for me - and the most fun)! It'll do double duty as an overland trailer and utility trailer, since I do a lot of river cleanups and community gardening/helping a friend build a homestead.

I don't expect to tow more than 500-1500lbs on the regular, but from everything I've read, the Forester can safely tow up to 4409lbs (2000kg) so long as the trailer is braked and you keep your speed low (this is a UK rating, where lower towing speeds are legally mandated). To my knowledge the UK and Canadian Foresters are the same, except the UK have a transmission cooler, stronger hitch (my DIY hitch/rear tire gate was build to this spec) and possibly higher spring rate in the rear. I don't suppose there'd be something completely different with the unibody or suspension that'd make towing more with the USDM foz impossible? Being stuck with 1500 lbs when international Foresters are rated for nearly triple is a bit underwhelming...

So basically, does it make sense to build a trailer that could tow 3500lbs, even if I do that very rarely, or is that just a bad idea with the Canadian version of the Forester XT, and thus it makes no sense over-building it?

 

[Kevin]

To my knowledge the UK and Canadian Foresters are the same, except the UK have a transmission cooler

Maybe an external cooler is added in a "tow pack". In winter you probably wouldn't need it but rather rely on the warmer/cooler already in the bottom of the radiator.

I don't suppose there'd be something completely different with the unibody or suspension

I think there is no difference in body or suspension just that you guys have the steering wheel on the wrong side!

So basically, does it make sense to build a trailer that could tow 3500lb

Yes, it makes sense to me as it gives more versatility even if it's towed by a larger vehicle.

 

[Ben Up North]

The larger the load capacity you want, the heavier the trailer is going to be unladen no?
For a Subaru, I'd keep it as light as possible.

 

[Kevin]

However, it is an XT so won't be a problem. My son's 2012 S (similar to an XT) can still throw you back in the seat when towing a heavy trailer. One of our members TroyXT regularly towed a rather large Jayco camper van.

 

[baipin]

The larger the load capacity you want, the heavier the trailer is going to be unladen no?
For a Subaru, I'd keep it as light as possible.

Technically yes, but I'm not sure if it makes that much of a difference now that I think about it; i.e. it's the difference between 290lbs unladen for a 2000lb axle 4x6 trailer vs 350 lbs unladen for a 3500lb axle 5x7 trailer, using the most bare-bones, no-frills steel tube frame trailer I could build (note that I'm changing axle size and trailer size between the two). This would essentially be a M101 military trailer, minus the tub.

Thanks for the input guys. If you think I could tow larger loads every now and then, then I may as well take a hit to the tare weight and go with something both larger and beefier, eh?

 

[baipin]

Hmmm I can't seem to modify my post, but I meant to add: If I add hydraulic brakes on the trailer and monitor CVT temps, that should go a ways to making sure everything stays safe and within the working limits of the transmission, I suppose.

 

[Ben Up North]

If I add hydraulic brakes on the trailer

As soon as we go over about 1650lb in Oz, we are required to have brakes fitted. So hydraulic brakes are a great idea!

The other thing to consider is what your GCM is. Not much point in having a 3500lb trailer loaded if you can't carry what you need in the car.
From what I've read (and it's surprisingly hard to find) the GCM on the 2013 Forester is 3550KG, with a GVM of just over 2000kg.
This leaves 1500kg total carrying capacity.
if the trailer weighs 200kg, we're down to 1300KG total weight. If you're a bit like me, you're probably pushing 90-100kg around and driving's no fun on your own so take another 180kg off. plus your camp setup at a wild guess being 100Kg we're down to about 1000Kg of total carrying capacity in the trailer.
Add the trailer weight back in of 200kg and and you end up with a GTM of 1200kg or 2600lb.
Load up the car a bit, and before you know it, you're down at around 800kg that that you can put in the trailer, even with decent brakes etc.

as yours in a newer XT, the towing capacity seems higher, at 1800kg. couldn't find the GCM but the GVM might have increased as well, if it's closer to the 2019 forester.


Of course, I could be completely wrong.

 

[Ben Up North]

Maybe an external cooler is added in a "tow pack".

It's mandatory in Oz according to this. A bit out of date but probably still useful.

 

[baipin]

Looks like the curb weight is of the FXT is 3600lbs (1640kg) or so. GVWR (max vehicle weight minus any trailer weight) is 4651lbs (2110kg). The max weight I've been at is 4200lbs (1905kg); that's with a fully-loaded gas tank, water tank, fridge, and a literal kitchen sink back there in my camper, plus the bumper and spare, one 150lb dude (me) and a load of steel from the junkyard. So for an average weight loaded up for camping, I'd put myself at 4150lbs (1882kg). Still 501lbs (227kg) under the GVWR weight limit. Max tongue weight is rated at 200lbs in North America, but about double that in the UK or Australia (no exact numbers except "it's double" and that falls in line with the "8%-15% of trailer weight as tongue weight" rule), which I could still do with 100lbs to spare. I doubt I'd have all the crap in the back that I do now, if towing that much anyways. Normally I'd be towing 500-1500lbs (228kg-680kg) total trailer weight (this is going off of what I haul with my gardening and river cleanup stuff, and what another guy with a SJ Forester tows offroad).

So in short, I should be safe in terms of GVWR and, max towing capacity, within the listed limits, assuming my calculations here are on point?

 

[Ben Up North]

Does your total trailer weight include the weight of the trailer?
Assuming it does, the only thing that's missing from your equations is the dreaded GCM, well at least in Australia.
Catches people all the time here, they go out and buy hulking big 4wds, tow caravans the size of small shopping centres (about the same level of attractiveness too, with a toilet in the middle of it) behind them and put a massive tinnie on the roof of the 'cruiser.
All looks good on paper until you work out that you can only fit two small adults and enough toilet paper for three days in it before exceeding the GCM.

But from the figures you've given and with a bit of rounding, you'd need a GCM of around 2800kg.
Considering the 2013 forester has a GCM of 3550kg, I reckon you'd have oodles of leeway, assuming GCM is a thing in North America.
Good brakes are considered a must if you're going up and down hills a bit. which is what I need on my trailer, but too much else to do at the moment, especially at my glacial rate of knots.
Sorry, gave up on the lbs..!

 

[baipin]

GCM = GCWR in North America I believe (Gross Combined Weight Rating). Subaru does not give one and this seems to be an issue with all sorts of vehicles; for whatever reason a lot of brands don't give it out. In any case, there's also the 2200lb GAWR (max weight over a single axle). I don't think that'll pose an issue for me though. All that I've read says that you only need to worry about tow vehicle GVWR and trailer weight being both within their respective bounds - i.e. you could max out on both trailer weight and GVWR and still be in the clear. (tare weight of empty vehicle (except for fuel and oil) + passenger and driver weight + tow vehicle cargo weight + trailer tongue weight) = GVWR.

Sorry for stickin' to the freedom units - Canada is a weird mix of the two systems. Anyways, sounds like I'll have a healthy margin to tow a few thousand pounds of my toilet paper horde out into the boonies until this whole coronavirus thing blows over. Ha! Thanks for the help, man!

 

[Kevin]

I can't seem to modify my post,

Once your "New Member" status changes to "Forum Member" you will be able to edit your posts.