Swivel preload again

Well, I drove into town and back today. Considering that all I did was remove a single thin shim (about 0.001" - I could measure it!), the difference is astounding.

Not only is the incipient shimmy I had been concerned about gone, but also gone is a slight steering vibration between 70-80 that I had decided was too high a frequency to be a wheel, had to be a prop shaft, and I had already had the front shaft off and carefully checked it. (must have been a low amplitude, high frequency shimmy, probably the lack of preload allowing slight sideways movement on the bottom bearing). Overall feel of the steering is also markedly improved, although I had not picked it as being deficient.

All in all, confirms the opinion I've held for some time that the first thing to check with any steering problem is the swivels.

John

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Originally Posted by JDNSW

All in all, confirms the opinion I've held for some time that the first thing to check with any steering problem is the swivels.

John

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Funny thing is, I've always found the panhard at fault so far, the most minute movement can cause all sorts of issues, keep in mind, most all things I play with have larger tyres than standard

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Originally Posted by rovercare

Funny thing is, I've always found the panhard at fault so far, the most minute movement can cause all sorts of issues, keep in mind, most all things I play with have larger tyres than standard

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I'll agree that the Panhard only needs a minute amount of play to cause problems, but in my experience this immediately shows up as wander, and is not hard to diagnose. But as you say, larger tyres may influence this as well.

I think the bottom line is that for steering to work as designed, everything needs to be up to specification - there is no one-to-one correspondence between symptoms and faults, and many symptoms can be caused by a number of different faults, or more usually, contributed to by a number of different faults. The problem is that you fix one thing and the symptoms disappear - but have you fixed the problem, or only part of it? I am reminded of a case I saw about 45 years ago - our company mechanic got the whole front end in tip top shape on a Series 2 - and it still had a severe shimmy. Remember that at this time, wheel balancing was not routine, in fact was rare, and few places had the facilities to balance light truck tyres easily. As a last resort, he got the local tyre place to balance the front tyres - and found that one front tyre was 26 ounces (nearly one kilogram) out of balance! Investigations showed it had a one quarter sleeve fitted.........

In this case, I am pretty certain I have - with the front jacked up, I checked for any free play in tie rod ends or wheel bearings, the tyres are near new and hence recently balanced, and I have recently replaced the panhard bushes, and when I was finding that source of wander checked all the other bushes. In correcting the preload, I was expecting to remove the incipient shimmy, but I was not expecting the other improvements - in particular, i was worrying about how I could have an out of balance front prop shaft with no play on unis. I even disassembled it and checked the alignment and replaced the rubber boot, all without any change.

John

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Originally Posted by JDNSW

I usually put a jack under it, but this time I did not expect it to leak as soon as I loosened the bolts - usually waits until you start to lift the top pin.

As for the brake hose bracket - first time you have to have it off, convert the hole to a slot. Then all you have to do is, as I did today, loosen the nut, crack the gland nut on the swivel, and just pivot it out of the way, tightening the gland nut to keep it there and not leaking.

By the way, it is all back together - I'm going into town tomorrow, see how it goes, but I expect the problem to be completely solved.

John

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Exactly what I did with my brackets, but you would think that the slot should have been there in the first place, Regards Frank.

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Originally Posted by Tank

Exactly what I did with my brackets, but you would think that the slot should have been there in the first place, Regards Frank.

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I agree entirely - this is probably one of the things that makes people reluctant to fix swivels - you have to bleed the brakes, and you invariably end up with spilled brake fluid.

Just one of the design details that shows the separation between designers and those who have to maintain their design. And this particular design detail has been round for over forty years, unless I am mistaken.

John