VW IRS

[birddog1148]

Has anyone used the rear IRS from a VW to build a frame?

I have one and am thinking of using it, could use a surge brake actuator to keep the brakes functional and re index the rear for ground clearance just like the Baja.

[Endo]

It would be interesting. I like the idea that the suspension would match the tow vehicle.

The one downside that comes to mind are replacement parts. If you broke down while on a trip are parts easily found? Parts for a "standard" trailer suspension are easy to find. Leaf springs, bearings and tires are easy to locate for a standard utility trailer suspension.

[birddog1148]

Twas a grand idea, but my VW forum buddies talked me out of it, and they had valid points.
http://www.shoptalkforums.com/viewtopic.php?t=122909

[deepmud]

talked you out of it why/how? this compared to Harbor Freight? It's light years better. More like the AT Expedition Trailer.

I've run my Subaru rear axle trailer over 15 years, over 15 thousand miles and and overloaded as much as 2100 pounds on it. On the original, 1984 wheel bearings.



Something about the way a swing-axle works makes it great for trailers.

[brian_bp]

talked you out of it why/how?

I think that it's important to note that while both VW and Subaru share features such as automotive-grade hardware and torsion bars, they are quite different in the way they mount and the existence of driveshafts; in both respects the front-wheel-drive Subaru rear suspension hardware is clearly more appropriate. I think the illustrated Subaru setup is a good idea, and the VW system is of marginal usefulness.

Fortunately for someone who might go ahead and use the VW "IRS" system, it looks (from drawings) like the CV joint can be unbolted from the stub axle (the part which goes through the bearings) and omitted; with typical driven front suspensions, the outer CV joint housing is the same chunk of metal as the stub axle, and thus not readily left off.

Something about the way a swing-axle works makes it great for trailers.

I agree that this suspension geometry is good for trailers... but it's semi-trailing arms (or nearly trailing arms), and not swing axles. The earlier VW Beetle suspension without outer CV joints is a swing-axle, but the one the VW fans strangely* call "IRS" is not... the axle shaft does not form part of the suspension.

I think that an actual swing-axle suspension would be a poor choice for a trailer.

* - both swing-axle and VW "IRS" systems are Independent Rear Suspension, so using the term "IRS" to distinguish the non-swing-axle VW system has never made sense, but is very common.

[deepmud]

ah, I agree I misused the term "swing axle" in my hurried response. Some older IRS suspensions (like the famous Corvair) did use swing axles - not so good.

The good part about the VW would be only that he has it in hand - I favor the Subaru, as it is really easy to attach to a frame. The 2wd rear may or may not be common in the areas in the lower 48 states - they are a pain up here in Alaska, and if I was to use a 4x4 unit, I'd cut the CV cups off with a $25 angle grinder

Parts for both Subaru and VW are pretty common all over the world, I'd imagine. I would not say it's important to match the trailer parts to the tow rig - the tow rig can change a lot over the life of a trailer. I DO like them to match wheels/bolt patterns when possible. I had to take a couple spares with me from Alaska to Washington D.C. and back because my Subaru trailer didn't match my Aerostar Van. I didn't actually use them and it meant I had to carry extra weight for no reason. As for parts breaking - unless you can weld and cut, there isn't a lot you can do with either leaf or trailing suspensions. The inherent design of the trailing arms make them resistant to catastrophic failure as apposed to leaves which tend to break/crack/snap. Both systems need a good wheel bearing to hold the weight, and neither system will last long overloaded.

I read a lot of posts about people being happy to have a fixable suspension on long expeditions, but it's always been leaf springs breaking - or maybe the axle breaking off due to the suspension getting bottomed out repeatedly (see http://www.lonewolftransglobal.com/Vehicle.htm for instance). Not REALLY a fair comparison - I think 95% or better of trailers must be leaf suspended - it's not like 50% of trailers are trailing or torsion sprung and 90% of failures are leaf. However, AT trailers makes a good case for moving away from leaf suspension, and they have a lot of personal experience with trailers on rough roads to draw from.

Adventure Trailers articles on the various suspensions they have used:
http://www.adventuretrailers.com/suspension.html

their new site
http://www.atreport.com/

[ntsqd]

The shown IRS 'sub frame' is from a Bug and isn't a great candidate since it is part of the Bug's "pan" (chassis as it were). The IRS sub frame from a Type 3 VW is a much better choice because they are designed to bolt into the car. They have built-in mounting points.

Compared to the Sube parts it is still not as friendly to use, but it would work better than the bug parts.

If desired I have one at home that I can take a pic of. I was going to use it to build a trailer to carry my glass buggy with, but that is no longer needed.

[birddog1148]

From STF I see?

[birddog1148]

I sold that rear end, going to try to build something that will slide in and out of my 4x6 utility trailer. So I can pull it with my Baja.
I can get these fiberglass sheets from work that were rejects from circuit boards or something.

[cuyeda]

This is picture of teardrop that was fabricated to match the VW tow vehicle. Similar idea, but totally fabricated.

[ntsqd]

who, moi?


Yeah, I never saw that thread on STF or I'd have commented in the positive. I just don't think that the std off road prep for a VW trailing arm would be found to be lacking when used on a trailer. Loads are loads, doesn't matter what the source is. Time duration of the loading matters, size of the load matters, but not what did the loading.

Re: the comment about the narrow track width. The T3 (or T1 for that matter) torsion housing can be split at the center. Insert what ever length of tube is needed to widen the track width to the desired width.

T-Bars have a huge rising rate, so damping is critical if long travel is contemplated.

[deepmud]

Said to be 6000 pounds of trailer and load.

I found that here:
http://www.tractorbynet.com/forums/buil ... ers-2.html

The jist of it is he ran his trailer for years as a single axle (like mine) then liked it so much he added a second axle and it had been used for 34 years when the thread was up in 2006. He mentions making others, including a 3axle race-truck hauler, and welding spindles to on from what ever the tow rig was made of to end up with matching wheel pattern and hubs - and using type 3 VW axles to be able to split them and get the track width he wanted AND even flipping them to make "lowrider" versions.

Great ideas.

EDIT: birddog, you should post the pic and link to your original thread.

[Shadow Catcher]

If I am not mistaken the Subaru axle is the rear axle from a front wheel drive Sube. This is a true torsion bar suspension and has been used successfully in trailers. If I were going to build an off road light weight tear I would be looking for one.

[Shadow Catcher]

Look at some of the suspensions on some of the off road trailers.

[deepmud]

If I am not mistaken the Subaru axle is the rear axle from a front wheel drive Sube. This is a true torsion bar suspension and has been used successfully in trailers. If I were going to build an off road light weight tear I would be looking for one.

Yup. The 2wd Suby donated it's motor to a failed 4wd Suby and I got it's rear axle free.