Tow dolly: pivot vs fixed

So, back on the hunt for a tow dolly. 

Theres pivot and fixed types in my Price range around here with brakes. 

One im looking at in particular is a fixed unit, with brakes and a winch and a tilt deck. 

Ive only ever used uhaul dollys, and honestly cant remember if they are fixed or pivot. 

Whats the difference from them? Im guessing it boils down to steering being locked or unlocked for the car to be able to follow, right? Pivot can have sized steering, fixed cannot. 

Uhauls pivot. 

Thanks john. 

Ever used a fixed? This one is branded kar kaddy...

You're looking at one that has a winch?  That could be handy.  Years ago I pulled a dead Fiero, rearward, onto a Uhaul dolly but I got it done with a come-a-long.  

The tow dolly I borrow happens to be here.  It is a Master Tow brand.  I snapped some pics.  It has brakes.  A couple of years ago, I replaced the straps with some Amazon units that I seem to remember were $25 or $35.  Mostly I remember them being pretty inexpensive.  My former regular mechanic but still good friend got the unit for free.  On a Saturday, years ago, an RV stopped in with a seized wheel bearing.  This resulted in the shop telling them they couldn't do anything until Monday.  The RV owner then retorted with, "can you tell me where to buy an new tow dolly?"  And that ended with, "can you get rid of this one for me?"  

In Ohio, much to my surprise so much that I verified it, tow dollies do not require plates and therefore do not require titles!  My buddy ultimately did a cut and reweld job to get the old bearing out and put a new bearing in.  I took some pics.

Good bearing side

Formerly bad bearing side

I have not used a fixed.  For me, just Uhaul and Master Tow

The Kar Kaddy dolly I used to have had pivoting wheels instead of deck. It had a pin to lock them while empty but they were free to steer while towing. 

Ok... threadjack hardcore.  Disclaimer... I have never used a dolly before because I always had flatbeds at my disposal.  But.... how... wait... they make them that don't' pivot????  How does that work?  That's unpossible.  It's like a hay wagon that doesn't steer in the front.

My physics is hurting.  What is the flex/give point?  Do the dolly tires just scuff sideways really bad?  Does it just shred the car's suspension bushings?  Does it just fold the car in half?  Does it rip a hole in the space-time continuum?

In reply to Curtis73 (Forum Supporter) :

The steering is left unlocked on the car.

eastsideTim said:

In reply to Curtis73 (Forum Supporter) :

The steering is left unlocked on the car.

That doesn't work when the dolly turns..... unless the steering radius is half the car's width.

If the car's steering has to remain unlocked doesn't that mean that the ignition tumbler needs to remain advanced so as to not engage the locking steering column?   Doesn't this mean you are leaving the keys in the car?   

Perhaps I am wrong, but that is how I was told for a dolly that doesn't pivot. 

GAAHHHH.... Losing my brain here.

The towed car's steering doesn't fix anything.  When the tow vehicle turns, the whole dolly turns.  The tie downs where the tires sit in the dolly move forward and backward.  Allowing the steering to turn the wheel is on a tiny radius compared to the motion of the dolly.  How does this work?????  What I actually want to say is... how does turning not simply rip the entire front subframe out of the car, make the side of the car into a crushed soda can, or otherwise rip the tie downs?

In reply to eastsideTim :

Not doubting you for a minute... but my brain is in a feedback loop.  Physics, man  :)

Curtis73 (Forum Supporter) said:

In reply to eastsideTim :

Not doubting you for a minute... but my brain is in a feedback loop.  Physics, man  :)

No worries, I'm here racking my braing trying to figure out what the practical difference is between having a platform on the tow dolly that pivots vs. having the cars front wheels turn.

Curtis73 (Forum Supporter) said:

In reply to eastsideTim :

Not doubting you for a minute... but my brain is in a feedback loop.  Physics, man  :)

Wierdly it doesn't work as badly as one might expect.  I mean, it's not good but, it does work. Sort of. With a sufficiently large tow vehicle the dolly gets dragged sidways on tight turns. With smaller tow vehicled the tow dolly slides and the back of the tow vehicle get's pushed straight. It's really only a problem on tight turns otherwise it works OK.  Unless it's slippery out, or the straps have loosend up from tight turns.

Get one that pivots.

eastsideTim said:

Curtis73 (Forum Supporter) said:

In reply to eastsideTim :

Not doubting you for a minute... but my brain is in a feedback loop.  Physics, man  :)

No worries, I'm here racking my braing trying to figure out what the practical difference is between having a platform on the tow dolly that pivots vs. having the cars front wheels turn.

The wheels turn on a super tight radius.  They don't move fore/aft much during steering.  A non-pivot tow dolly turns on a radius closer to 4'.  So when the dolly turns, the place where the towed car's tires sit moves way forward and way aft compared to the steering tires.

If you turn the car's tires 45 degrees, they might move forward an inch.  If you turn the dolly under the car 45 degrees, the dolly tire moves forward 2-3 feet.

eastsideTim said:

Curtis73 (Forum Supporter) said:

In reply to eastsideTim :

Not doubting you for a minute... but my brain is in a feedback loop.  Physics, man  :)

No worries, I'm here racking my braing trying to figure out what the practical difference is between having a platform on the tow dolly that pivots vs. having the cars front wheels turn.

Here, revised my picture for what I'm talking about.

Watch this one on a pivoting dolly.  Even in just a gentle turn, notice how the tire of the dolly is all the way parallel with the front bumper of the car.  The car's steering doesn't do that.

In reply to Curtis73 (Forum Supporter) :

Makes sense.  But the tow dolly wheels will always have the same relation to the towing vehicle, regardless of whether the platform pivots, won't they?  The rear wheels of the towed vehicle will be the ones that change their relation to the tow dolly wheels, and I think with a pivoting platform and locked front wheels vs locked platform and unlocked front wheels, I think the path the rear wheels will take is substantially similar.  Again, though, I could be completely wrong.

Btw, DO NOT back up a tow dolly. Destruction will follow. I've done it. :/

eastsideTim said:

In reply to Curtis73 (Forum Supporter) :

Makes sense.  But the tow dolly wheels will always have the same relation to the towing vehicle, regardless of whether the platform pivots, won't they?  The rear wheels of the towed vehicle will be the ones that change their relation to the tow dolly wheels, and I think with a pivoting platform and locked front wheels vs locked platform and unlocked front wheels, I think the path the rear wheels will take is substantially similar.  Again, though, I could be completely wrong.

Another quick picture.  Picture this as a non-pivot dolly.  What will happen when the tow vehicle moves forward?  The outside dolly tire will move much faster than the inside tire and try to rip the suspension off.  Since the towed vehicle's wheels are affixed to the car by the suspension and can't move fore/aft, how does it all work?  I'm genuinely curious.  The only way it can work is if the dolly tires slide sideways.

It's like a hay wagon that you welded the steering axle straight.  When you turn, you're just going to slide the tires.  The radius that the towed car's tires take is just a couple inches.  The dolly's radius is 4 feet.

Right now is when I wish I had animation skillz

I hate tow dollies. I owned a nice Master Tow tilt and swivel deck for a couple years, but it was such a hassle I just started driving my racecar on the street. They are difficult to load for anything low to the ground, such as racecars, which is the primary use case for most of us. I had to put a stack of 2x6s under the ramps of the tilt deck and still sometimes scraped. 

I can confirm, the Tow Master is not great for lower nose or lowered vehicles.  Another issue, the ramps are fixed and they tilt with the car.  For a very low car the end of the ramp could come into contact with the rocker panel once it tilts upward (level)

Curtis - I'm with you.  Flat-towing a car has a similar issue. 
 

i think that a fixed dolly acts the same as a flat tow and when you turn, the dolly slides/skids sideways.  But it does so at a cost of high side-loading of the front suspension/subframe of the towed car. 
 

there is obviously a reason there are pivoting dollies and why that's what the uhaul ones all are.  

Mine is a pivoting dolly that I picked up for almost nothing. It works fairly well. Doubling the line with a snatch block works wonders. 

I use the Warn Drill Winch to load cars. It also works fairly well but occasionally needs some help.