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Old 25 April 2007, 15:57   #21
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I have seen tread blocks peel away from tyre as they have become too hot and gone too fast. A blowout is only seconds away - ask Richard Hammond!!!
really was not thinking of hamster sort of speeds.... just done the bearings and the black round rubber things look brand new so all should be fine. think we will settle with 60mph nice and steady.
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Old 27 April 2007, 05:27   #22
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think we will settle with 60mph nice and steady.
Yeah, I always intend to travel at sixty as well
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Old 27 April 2007, 12:45   #23
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ok but really was not thinking that 80mph would be big or clever so will leave this for someone else to test.
Hmmm... got me thinking, fastest caravan tow currently 139.113mph (and it still wouldn't move over!!). Can't find anything about fastest RIB towing!

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Old 27 April 2007, 13:08   #24
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I'd heard the "stress" argument before and but never saw any science behind the figures, it wouldn't surprise me if load rose like this on the bearings.

OK – simple physics lesson.

Newton’s second law of motion is force equals mass multiplied by acceleration, commonly expressed as F=ma. In rotational motion the acceleration (a) component is the rate of change of angular velocity over time usually denoted by the Greek letter alpha. This can be calculated (for motion in two dimensions) from the formula alpha = angular velocity (usually denoted by the Greek letter omega) SQUARED multiplied by the radius (distance from axis of rotation).

Now, the squared bit is the interesting bit ‘cause this means that every time you increase the velocity (speed) you have to square it (multiply it by itself) to calculate the angular acceleration and hence force (assuming the mass is unchanged). So double the speed, four times the acceleration (2 x 2 = 4). Treble the speed, nine time the acceleration (3 x 3 = 9), and so on.

Interestingly, as you see angular acceleration includes a multiplication of the radius, in this case the size of the wheel. So a bigger wheel means higher stresses on the tyre! (You probably proved this to yourself when as a kid you stood on a roundabout - it was easier to stand in the middle than at the edge) Also FOR THIS REASON ALONE the wheel bearings are not subject to higher stresses (because they are so close to the centre of rotation) but have many other factors to contend with.

Hope this helps (good for insomniacs if nothing else!!).

Andy
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Old 27 April 2007, 13:58   #25
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from my experience ......as for tow speed i would say what ever speed and conditions you are comfortable with, reason i say this, it is nicer to tow on a roads and dual carridge ways than the motorway at times cos the motorway has those annoying ruts that can swing the car and boat all over the place.
have towed the large caravan, largeish boat and the rib, the rib is the most stable and just sits there at any speed, i wont say what i tow at but it always feels very very stable. for example i hate towing the hard boat on double axle trailer faster than 50 but the rib just sits there solid as a rock on a single trailer at any speed. the caravan can wag around a bit as richard quite kindly knows!!
when you come to hills it is sometimes better to drop you speed a bit while going down to keep control, i often go up hills faster than i go down em.

make sure your tyres and bearings and pressures are good, jockey wheel is tight as they can rattle down, boat well strapped as they can flip or bump round and your nose weight is suitable for the car, for the beemer i keep the nose weight very light, just heavy enough so it does not rattle

have fun
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Old 27 April 2007, 17:18   #26
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And to confuse the issue even more, if you're towing at 50mph, the top of the tyre is travelling at 100mph and the bottom is standing still.
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Old 27 April 2007, 17:41   #27
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And to confuse the issue even more, if you're towing at 50mph, the top of the tyre is travelling at 100mph and the bottom is standing still.
doesnt that depend on the diameter of the said wheel?

i'll have a pint of what he's drinking please
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Old 27 April 2007, 17:52   #28
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Old 30 April 2007, 18:23   #29
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I found a bit of a speed wobble sneaking when you hit the 120MPH mark, however it could have been coming from the bubbles in the side walls

I sorted it out though, I disconnected the safety and the break and then it was fine....
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Old 02 May 2007, 08:25   #30
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I found a bit of a speed wobble sneaking when you hit the 120MPH mark, however it could have been coming from the bubbles in the side walls

I sorted it out though, I disconnected the safety and the break and then it was fine....
I thought they say the best way to avoid that is to accelerate ?, You should have lost it by 150
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