MacGregorSailors.com

Hey Chip or Bill Heisey ,

I started this thread to avoid hijacking Normo's original tire size thread (http://macgregorsailors.com/phpBB/viewtopic.php?t=1802).

Could you give some more details (pictures would be nice too) on how you added a second axle. Did you move the existing axle forward and add the new one behind it? What about brakes on the second axle? Any problem areas to look out for?

Thanks.

I've promised to post the mod a few times and simply haven't gotten around to it. I promise to try to get it out in the next few days.

I'm not Chip or Bill, but I do have a second axle. I had mine mounted at an RV/Trailer sales a service center in southern Ohio. They ordered McGregor parts from CA. The second axle was mounted behind the existing original. The existing solid fender was replaced with a flimsy double. The rear spring bracket was replaced by a pivoting"V" with the front of the rear axle attached to the other side of the "V". I didn't put any brakes on the second axle. I did make sure the new axle had the grease points like the original. Despite that, I still have all four bearings replaced every spring. It doesn't trail any smoother or straighter than the single axle did, but I feel a whole lot safer hauling the loaded Mac long distances. For the past two summers, I've trailered to the North Channel (750 miles each way), and the tires stayed cool and show minimal, if any, wear.
Just an FYI,
Dave "Jac"
P.S. It was about $1200 out the door.

Dave X2000 Jac wrote:. . . It doesn't trail any smoother or straighter than the single axle did, but I feel a whole lot safer hauling the loaded Mac long distances. . . . about $1200 out the door.

Considering that you don't feel much trailing benefit, I'd just repeat my oft-expressed opinion that upgrading to larger 15" wheels/tires can add valuable capacity-margin at a fraction of the cost. Basically, one spends only the cost of adding the 2 wheels/tires needed for the second axle, plus some trivial tweaking for fender clearance on the original single axle.

This approach simply addresses the trailer's primary achilles heel - that of inadequate tire capacity. It doesn't attempt to add tread redundancy, extra brakes or springs or extra towing stability. It also avoids the weight, cost, time and complexity of those features ... whether they are worth the cost and complexity is an individual call.

Frank C wrote:Upgrading to larger 15" wheels/tires can add valuable capacity-margin at a fraction of the cost. Basically, one spends only the cost of adding the 2 wheels/tires needed for the second axle, plus some trivial tweaking for fender clearance on the original single axle.

What is the cost of a second axle?

Here's one in the mods section.
Trailer Mod

Oh no Frank...here we go again....

Hearing but what about the 3500# spindles echoing from the mountain tops.

Who wants to have a discussion about the shear strength of our stock Mac spindles? *running away very quickly as Chip and Moe sharpen their pencils*

Awww - not so bad.
Still learning somethin' by paging through, even when I don't subscribe!

I must have missed the previous debates of upgraded tires vs adding an axle. Here's my thoughts, based on years of towing large camper trailers, but only a few years of boat towing.

First of all, for some reason trailer tires are just a bit unreliable. My experience, that of my trailering friends, and numerous camper discussion forums have shown that trailer tires are much more prone to failure than car tires (on a car). I think the redundancy of 4 tires, which also reduces the individual load on each tire, should make them less prone to fail. If one does fail, the trailer should track better as you brake.

I had 2 sections of springs fail on a dual axle trailer. The main spring leaf did not fail, though it did bend alot. It turned out the springs were sized near their load limit. Having 2 axles allowed me to limp to a repair station. I was able to put a block between the axle and the frame. Again, reducing the load on each spring should reduce the probability of failure.

Going to a 15-inch tire raises the trailer at least an inch, which will add a little to how far you have to back the trailer into the water for launch.

I will add a downside to dual axles. Backing in a tight radius will cause large side loads and scrubbing of the tires. This could affect tire and spring life, how much I dont know.

I would like the cost of adding a second axle to be lower. But I think the cost is worth it. Will I ever need the extra redudancy? Dont know and hope I never have to find out. But thats the same reason we carry and wear PDFs, radios, etc.

If you will be launching in salt water don't waste your money on the Mac trailer. Get an aluminum, tandem with SS disc brakes. Some states' laws require brakes on both axles.

Dave wrote:The second axle was mounted behind the existing original.

By simply adding the new axle behind without moving the existing axle forward, you have shifted the effective axle pivot point so far to the rear that your tongue weight is probably in the 600-650 lb range. Fine if you've got a monster tow vehicle and hitch. I'm guessing you do, otherwise there's no way you wouldn't have noticed a difference in towing performance.

However, 600 lb tongue weight will exceed the capacity of many tow vehicles which would otherwise Be OK for towing the Mac.

Dave wrote:I didn't put any brakes on the second axle.

If you have single axle brakes on a tandem axle setup, those brakes should be on the rear axle.

Just a thought about the expence of putting on a second axel. I have a 1996 X with a 9.9 Nissan, so I'not carrying the weight at the back fo my boat , nor do I trailor it much either. For the most part it stays in a slip all summer, but I do haul it for an hour or so each way in spring and fall. The biggest problem as I see it( trucker here) is two things. Improper tire pressure, and not enought tongue weight.As I said , I have a small motor on mine so am not carrying the weight that a lot of you guy's are, but to avoid a lot of sway, get some more weight on the tongue to help balance the boat. Not sure what a 50 weighs, but you put that weight that far behind the axel, and your tongue weight is certainly minimised. Or so I see it..peaceful Christmas to you all....Jim in Canada

I towed ours, with the Suzuki DF50, back from SLC running 80-85 mph through Wyoming and Nebraska without a hint of sway, even with the crosswinds on the plains and changing lanes. So it seems pretty well balanced. However, the boat was new and empty, and the two 12 gallon fuel tanks were empty, so that additional 150 lbs behind the axle has me a little concerned. I really DO need to put it on the scales once loaded.

--
Moe

Jim wrote:. . . Not sure what a 50 weighs, but you put that weight that far behind the axel, and your tongue weight is certainly minimised. Or so I see it..peaceful Christmas to you all....Jim in Canada

Hear, hear!
I've said that for years, but it's nice to see it confirmed by somebody who oughtta know! My experience, Suzuki 60 @ 335# on the transom, was that sway disappeared completely by just correcting tongue weight. I put it on a Mayflower scale & found only 180#. Bumping that upwards to 280# (~7.5% of boat/trailer) completely fixed the sway problem.

Try it, you'll like it!

Frank wrote:Bumping that upwards to 280# (~7.5% of boat/trailer) completely fixed the sway problem.

I've been towing for over thirty years, and with the exception of the Mac owners' manual, nobody considers 7.5% adequate tongue weight. It should be closer to 10%.

I think the placard says to keep the tongue weight between 240-280 but not sure if that takes into account a heavy motor on the transom (or any motor on the transom). I usually keep mine at about 260 (using a bathroom scale pretty much to the max) and I don't have sway until going over 65. Perhaps having more weight on the tongue would make the sway limit be even higher. The hitch on my van is a bit lower than it would be on a pickup truck, so the trailer inclines down toward the van a bit.

Its not all that easy to get so much weight on the tongue IMO. To get 260, I've had to pretty much throw all the loose stuff into the V-berth. Since the last time I weighed though, I now have a spare wheel bolted up front so that probably adds some. Seeing as I've only been launching nearby lately, I also haven't gone over 60 with my new balanced marathon radials either, so I suppose its time for an Interstate trip soon. Got cold in Florida all of a sudden though, was in the 30's last night.