Modern Vespa

...and girls, cuz you got 'em, too.

Luckily for me, this has been covered in other posts, so this is just a reminder: Your rear wheel axle nut (the bigun with the cotter pin) likes to come loose! Give that year wheel a rattle, while it's free-spinning, on the stand, and see if it has some play.

Turns out my dang shock nut had nearly fallen off, as well. This will now be an easy pre-ride thing to visually inspect.

And I have indeed been using a torque wrench on everything.

Really don't get what happened to good, old fashioned lock washers on these machines.... I used a little Loctite on the axle threads...hope that doesn't come back to bite me....

And now that I'm feeling paranoid, I just might open up my CVT and make sure everything is still tight in there.

all my nuts and bolts are rounded off, going to replace with copper grease and as you say locking washers

Even with proper tourqing and the castle nut and cotter pin properly installed, the wheel nut on my ET4 would loosen over time.

I eventually solved the problem by applying blue Permatex.

I'd still try to rattle the wheel from time to time just to be sure.

Thanks, this is a good reminder.

I've noticed that because a new scoot is just so easy to hop on and ride, I easily forget basic checks before riding.

Yikes!! I will remember to do this as well. Nothing more scary than having something fall when you are traveling!!

I don't understand why a properly torqued castle nut secured by a proper size cotter pin can loosen up.

Unfortunately it's not actually a castle nut -- it's a regular nut with a castle-style-cap that fits over it -- and there's maybe an 1/8" of space between the top of the nut and the hole for the pin. Poor design, me thinks, based on the fact that a quick search revealed them loosening frequently.

Is there supposed to be a washer under the nut?

Yeah, there is a maybe 3/8" thick shim (washer), but that and the swing-arm aren't thick enough to place the nut close enough the cotter pin hole.

With everything assembled I can't get you a good pic and can't find a simple diagram online.

Crap design. But, seriously, why not throw a simple spring lock washer on there?

...also wonder if it's different on the post-leader/GTS etc. engines...?
[/img]

Tom, is there an opportunity to replace it with a "nyloc" nut? Nylocs are nuts with a nylon ring on one side that create a friction fit on the bolt/axle. I've used them successfully on many things that would vibrate a normal nut loose. You could also use "blue" loctite. The blue version grips tightly but is easily removable with a wrench. Don't use the red loctite, it will lock on forever. Don't use the yellow loctite, it doesn't provide much grab.

Best
Miguel

How about putting a washer on top of the nut, to raise the castellated cap high enough to give a good snug fit for the cotter pin.

You and me both. I still can't understand it. It doesn't make sense.
But I couldn't argue with reality (Even though I often complain about it. )

The wheel nut would never come off, the castle nut cover thingy prevented that, but it will still loosen up enough to matter regardless of proper torquing.

I even remarked about it here back then and found a few solutions, but they were red herrings...I still ended up using Permatex.

I don't have my ET4 anymore, so the problem will remain a mystery for me.




As an aside: Whointhehell at Permatex decided that, while it was a good idea to put Blue Permatex in a blue squeeze tube, that it would also be a good idea to put the more permanent Red Permatex in...

...a blue squeeze tube.

Sure, the tiny lettering on the tiny tube is red, but it's easy enough to confuse someone who was not playing close attention....like me, for example. I didn't notice until the red stuff came out.

I don't think I'll ever get that license plate unbolted now.

It cant. Function is same as castle nut if assembled correctly. If loose either not torqued, or missing or damaged parts.

Yeah, apparently some wine-drunk, cost-cutting, Sino-Italian manufacturing engineer agreed with you and thought pressed tin had the same structural qualities as machined steel, which is why this problem pops up so frequently; if 90 lbs of torque isn't going to keep this nut tight, no way a loose-fitting tin cap will do it.

Yeah, that or a simple spring washer. But I'm waiting for one of the experienced mechanics to chime in. It's like the variator nut; I honestly don't get why they chose some disposable nut over a more traditional design.

Wait a minute. Nyloc, lock washers, cotter pins and loctite are not there to prevent nuts coming loose. They are there to prevent losing the nut, resulting in a catastrophic event after your bolted connection has already failed.

All bolted connections can fail under dynamic loads. It's part of the design process to come up with the right size and torque to prevent this for the estimated loads. If the nuts still come lose, something is wrong.

I'd much rather notice a loose nut than have all the load on a castle nut and cotter pin.



Sorry, if I'm not using the correct technical terms. My engineering classes were in German.

Nuts and bolts come loose for a variety of reasons, due to such things as wear on the threads or someone using lubrication when it's not needed, or simply using the wrong torquing technique or value. But this is particularly true of parts that have been 'overtorqued' or overtightened by someone without a torque wrench. It stretches the threads. Even if torqued correctly afterwards, the part may still come loose due to this threads stretching which alters the torque values needed, and prevents proper torquing. It's worth noting that many folks use lubrication on threads (grease mostly) in the belief that it's needed. Well, mostly it's not and you must check your manual for instructions on whether to use lubrication or not. Mostly (nearly always) you must not use lubrication (even coppaslip) when torquing a high value item. Torque values shown in manuals are usually 'DRY' torque values. If you add lubrication to prevent seizing for example, this alters the torque value as you apply the pressure and this will result in 'OVER-TORQUING' of the component and WILL stretch the threads which can resulting in parts coming loose. If lubrication is necessary the manual will tell you. In our workshop we often noticed how frequently customers use lube without it being needed. Of course, always replace a nut or bolts if it's a one use item as listed in the manual.

has anyone tried using a proper castle nut ? it seems that may work better than the retainer that comes on them. I just went out and looked at mine, its tight and the cotter pin does engage the tabs on the cap. i have removed mine before to do tire changes and do use a new cotter pin every time.

Heed Stromrider's advice. The manufacturer's recommended torque values for a fastening are based on the fastening being configured exactly as the manufacturer designed it. Adding lock washers, nylocks, "lubricants", loctite and/or any other variations to the fastening changes the dynamics of the fastened components and will, quite often, result in improper securing.

As Oliver mentions, if a fastening is failing, it is rarely because of design error, but some other fault. Thus, coming up with your own jury rigged solution, such as nylocks, etc, is not, in any way, a prudent choice.

For what it is worth, I have had four GT's (still have three) that have well over 100,000 miles on the four. That nut has never come loose on any of mine.

You might want to get your torque wrench calibrated.

Ooh, I wonder if that's it. After a few stuck nuts I did get pretty liberal with the Liquid Wrench back in March when swapping stuff out, and didn't necessarily clean that stuff off (with brake cleaner etc) before reassembly.

Anyway, at this point, we'll see what happens over the miles.... Do you mean cuz I bought the cheapest one I could find? Yeah, hmmm....

The fact that the shock nut was loose certainly points to tool or user error, as well.

Regarding the castle nut, the service manual for my ET4 actually showed a real castle nut in the diagram. It looks like someone decided to cheap out at some point.

Not necessarily a "cheap out". Castellated nuts are not necessarily more expensive than a standard nut and castellated nut cover.

You will note, on inspection, that castellated nuts are adjustable in 60 degree increments, while castellated nut covers are usually adjustable in 30 degree increments. I'll let you reach your own conclusions as to how the nut cover might be preferred in a torqued application.

Yeah, I remember that about using the six foot bar to torque down VW axle castellated nuts...when you'd have push down a liiiiiittle bit mooooore to uncover the hole...jusssst a liiiiiittle morrrrre...cringe.

Apart from lubrication and torque wrenches in need of calibration, people overtorque their nuts simply because they are unaware of how to properly use a torque wrench. I often see them turning their wrenches bit by bit and then, once the wrench has triggered, go at it again for good measure.

The way I learned it is to tighten your nut in one uninterrupted motion until the wrench triggers and then leave it at that. This way, you stay in - again, forgive me for not knowing the proper terms - you stay in "slip friction", which is significantly lower than the "stick friction" that you get at rest. The torque values are based on "slip friction".