Nylock Nut Myth.

**Bonez** · 4th February 2020, 08:57

Popped in to Steel Masters today to get a couple of smaller bolts for the XF650s risers. The young chap was adiment that my nylocks needed to be replaced aka a one use item. I politely told him as long as you can not screw used nylocks up by hand they are perfectly fine for reuse. I also showed him that the nylock I had wouldn't twist on by hand past the nylon. Is this an industry wide myth becuase I've heard this a number of times over the last year or so. I was in the RNZAF engineering feild for 23years and never heard such bollocks.

**HenryDorsetCase** · 4th February 2020, 09:12

Originally Posted by Bonez

Popped in to Steel Masters today to get a couple of smaller bolts for the XF650s risers. The young chap was adimit that my nylocks needed to be replace aka a one use item. I politely told him as long as you can not screw used nylocks up by hand they are perfectly fine for reuse. I also showed him that the nylock I had wouldn't twist on by hand past the nylon. Is this an industry wide myth becuase I've heard this a number of times over the last year or so. I was in the RNZAF engineering feild for 23years and never heard such bollocks.

I've found nylock nuts to be perfectly acceptable for use on conrods.

**Bonez** · 4th February 2020, 10:08

Originally Posted by HenryDorsetCase

I've found nylock nuts to be perfectly acceptable for use on conrods.

That's one place I would use nylocks. But if it works for that's cool.

**sidecar bob** · 4th February 2020, 16:35

Originally Posted by HenryDorsetCase

I've found nylock nuts to be perfectly acceptable for use on conrods.

On an air compressor only i hope?

**Kickaha** · 4th February 2020, 16:58

Composition on the nylon component has changed over the years, they originally recommended them as single use only, depending on what it is for I'll also use coneloc or K-nut/jet-nut

**Bonez** · 4th February 2020, 18:03

Originally Posted by Kickaha

Composition on the nylon component has changed over the years, they originally recommended them as single use only, depending on what it is for.

Must have been over 40 years ago. At basic engineering it was one of the first things you were taught in the fasteners class.

**HenryDorsetCase** · 4th February 2020, 18:41

Originally Posted by sidecar bob

On an air compressor only i hope?

and VFR400s

**pete376403** · 4th February 2020, 19:24

I would use, or not reuse *any* fastener based on the criticality (is that a word) of potential failure of said fastener, eg probably not reuse con-rod bolts, absolutely reuse screws that hold the fairing on

**Bonez** · 4th February 2020, 19:40

Meh. The CB550 has over 90,000kms up on original conrod bolts since I rebuilt it. They were still in tolerance.

**Grumph** · 4th February 2020, 22:00

Originally Posted by HenryDorsetCase

and VFR400s

Oh please, fuck no. Not an appropriate use at all. Between the heat and the centrifugal loadings, sooner or later you'll have the nylon insert on the oil pump pickup screen. Conelocs with the metal insert would at least be a safer choice there.

You can get away with reuse of rod bolts and nuts in a lot of older motors - eg CB550 - as they are not torqued to yeild point when installed. But crack testing as a minimum would be advised if you have to reuse.
Modern stuff where both the head bolts and rod bolts are toqued to yeild I would always use new. With engines becoming an ever greater source of frame stiffness, head bolts are becoming more critical as the loads fed through them get bigger.

No-one is as picky today as a guy I used to know. Specialist in Rolls Royce car engines. They have the nuts on rod bolts retained by cotter pins. He would hand lap the nuts so as to get the correct torque at the point where the cotter pin holes lined up....

**Bonez** · 5th February 2020, 07:51

Originally Posted by Grumph

Oh please, fuck no. Not an appropriate use at all. Between the heat and the centrifugal loadings, sooner or later you'll have the nylon insert on the oil pump pickup screen. Conelocs with the metal insert would at least be a safer choice there.

You can get away with reuse of rod bolts and nuts in a lot of older motors - eg CB550 - as they are not torqued to yeild point when installed. But crack testing as a minimum would be advised if you have to reuse.
Modern stuff where both the head bolts and rod bolts are toqued to yeild I would always use new. With engines becoming an ever greater source of frame stiffness, head bolts are becoming more critical as the loads fed through them get bigger..

Using the engine as a stressed member of the frame is not as new thing. Honda did it on ther CX and CBX1000 series. Also specilised frame builders like Harris and the like on modified production engines. In fact you can't get a stiffer component than the engine.

**Grumph** · 5th February 2020, 09:01

Originally Posted by Bonez

Using the engine as a stressed member of the frame is not as new thing. Honda did it on ther CX and CBX1000 series. Also specilised frame builders like Harris and the like on modified production engines. In fact you can't get a stiffer component than the engine.

In theory true...But there are some outstanding examples where that doesn't hold. XV yamaha family is a good example. To use one of your examples, have you ever talked to someone who's turbo'd a CBX ? Fine for drag racing, use it on a bendy road and you're into head gasket problems.

What I doubt you know is just how high are the loadings modern tyres feed into a frame on say, a 120mph lap of the IOM.
The current superbikes are all now made with the barrel in one with the top engine case - thus making them stiffer.

But then the critical load path is via the head bolts. Steering head loads into frame high up, engine bolted in to stiffen the frame so loads then travel to the rear engine mounts which are designed to take them.

Talk to someone about the problems encountered in the IOM by the BMW teams. It's an eye-opener.

**Bonez** · 5th February 2020, 09:11

Originally Posted by Grumph

In theory true...But there are some outstanding examples where that doesn't hold. XV yamaha family is a good example. To use one of your examples, have you ever talked to someone who's turbo'd a CBX ? Fine for drag racing, use it on a bendy road and you're into head gasket problems.

What I doubt you know is just how high are the loadings modern tyres feed into a frame on say, a 120mph lap of the IOM.
The current superbikes are all now made with the barrel in one with the top engine case - thus making them stiffer.

But then the critical load path is via the head bolts. Steering head loads into frame high up, engine bolted in to stiffen the frame so loads then travel to the rear engine mounts which are designed to take them.

Talk to someone about the problems encountered in the IOM by the BMW teams. It's an eye-opener.

I don't really care about bikes runing in the IOM or drag racing. The bikes are set up specially for those purposes. I care about day to day use which is more appropriate to my application aka day to day road bikes. For that purpose an engine is stiff enough.

**F5 Dave** · 5th February 2020, 12:11

I replace nylocs when the wear out and they do. Exhaust pipe mounts youd get 2 or 3 reuses out of them but they would turn on with little resistance after that. Heat, vibration, oil the usual suspects.

A friend (ex reconditioner) relayed his tutors example of a car block on a jig. Piston with no rings drops through bore. Decent spanner on strategic point, minor pressure = piston gets stuck. Wasn't a fan of stressed engine frames.

Of course as Greg points out, they have thought about load paths to isolate issues. Not to say it is always appropriate. Ducati poor old Pantah cases got increasingly tortured as they grew into well beyond their original remit.