Inner tube installation

I'm installing new tires on my 1977 R100S. I've changed many tires over the years, but one thing has been bugging me. I'm using new Metzeler inner tubes. The valve stem has two jam nuts and a conical shaped washer on it. I know the washer goes between the tube and the rim, but does one of the jam nuts go inside the rim between the washer and rim? Or does ONLY the washer go inside the rim and BOTH of the nuts go outside the rim? It seems if I put one nut inside the rim the tube would have to distort to form around the nut. The rubber is very thick at the valve stem, and the nut would put undo stress on that part of the tube. Any thoughts?? Joe

What was on the old tube when you removed it?

One nut inside, one nut outside. This will keep the stem moving up and down and all around. Some dirt bikers leave the outside nut off or just barely on, giving the stem some 'slack' to go inside the rim if the tire happens to spin on the rim, pulling the tube with it. This hopefully keeps the stem from ripping away from the tube. YMMV

queretaro said:

What was on the old tube when you removed it?

Click to expand...

nothing on the inside, and a knurled nut on the outside.

I think this is a great question,r.e.TR-4/TR-6 inner tube metal stems, both of which are metal. The nuts I see on MC's are hex, not knurled like bicycles.
When I have disassembled OEM tires from old Hondas ,etc., they seem to have the washer on the inside & one nut on the outside. Who knows if they had the tube replaced and when I just checked a parts schematic the stems are not shown. I think the idea is to have the tube stationary if the tire slips. On bicycles there is usually one nut on the outside to keep the tube available for inflation and stationary too-my guess. When you buy most brands of MC tubes these days, you get a washer and 2 nuts. I've wondered the same OP question. I see the washer as staying inside as it's obviously curved to fit concave into the inside of the rim, i.e., not to get :mashed into the outside surface. As for 2 nuts , typically in a mechanical assy when you have 2 nuts it for one to be the lock nut, so why not the same on an inner tube?
I looked until I lost interest & google was drifting away from topic toward British engine valve stem installation. I did run into other people asking the same question on various forums. I cannot think of a purpose for a nut inside the rim other than as a spacer & why have the washer if that's a need?One guy that worked in his family Brit bike dealership yrs ago said one nut outside but that doesn't explain why they all come with 2 nuts.FWIW, he also commented that it's important to not use a wire wheel on the inside of rims as you take away the edges of the striations that are to keep the tire from rotational slipping-I can see that this would be even more important on airheads as they are alloy , thus softer.
I suspect Darwin could explain why(two nuts) humans & probably some other primates are so equipped. I have a nephew that has three kids from a "onesy situation" as he sadly got testicular cancer in his late twenties when he was in med school.

Perhaps you'll find the attachment interesting ...

valve stem nuts

lkchris said:

Perhaps you'll find the attachment interesting ...

Click to expand...

Thanks for the service bulletin attachment! I put the washer on the inside, and both nuts on the outside slightly away from the rim tightened against each other. Another of lifes little mysteries solved. Joe

oldnslow said:

One nut inside, one nut outside. This will keep the stem moving up and down and all around. Some dirt bikers leave the outside nut off or just barely on, giving the stem some 'slack' to go inside the rim if the tire happens to spin on the rim, pulling the tube with it. This hopefully keeps the stem from ripping away from the tube. YMMV

Click to expand...

You may be old & slow but according to the Kenda inner tube box(I had a new one on my workbench) your on the money. One nut inside other outside the rim. I looked online earlier & read a blurb from Michelin on how their tubes are better due to the splice being a taper , not a butt joint as others.
FWIW, the Goodyear tubes I watched made were all with tapered splices too. They doped the green rubber with cement after skiving(tapering) the edges with what looked to be the same thing as a tube patch cement then rolled them down with the same stitcher as a tube repair then vulcanized the splice under a heat thing kind of like a shirt press @ the dry cleaners as I recall.

FWIW, when I changed my rear tire a couple months ago, it had the washer & a nut inside and a nut outside. It had been on the wheel for quite a while with no issues.

Also FWIW, I had my front wheel into the local airhead guru the other day to have the wheel bearings replaced. He tightened down the valve stem nut mumbling something about people who read BS on the internet. I will probably loosen it before I re-install the wheel. Maybe I should show him the bulletin that Chris posted. Oh well...

As always, YMMV...

The nut on the inside keeps the stem from pulling through the hole, and putting stress on the joint between stem and tube. The nut on the outside's only purpose is to prevent the valve stem from being pushed into the hole.

The service bulletin advises a nut placement based on improper inflation-why would you say something like that in a tech publication? I'm thinking a nut placement based on a PROPER!!! inflation makes more sense? The washer is curved in such a way that it allows for the round shape of the tube and rim as well . Having a nut inside & out would keep the pressure of the nuts off the stem base where it meets the tube but having 2 nuts on the outside will allow the locking of the stem in a certain relationship with the rim/tube allowing positioning of the stem.
Do we go with BMW & assume improper inflation-maybe the person there was a poor writer?

MARKAZ said:

FWIW, when I changed my rear tire a couple months ago, it had the washer & a nut inside and a nut outside. It had been on the wheel for quite a while with no issues.

Also FWIW, I had my front wheel into the local airhead guru the other day to have the wheel bearings replaced. He tightened down the valve stem nut mumbling something about people who read BS on the internet. I will probably loosen it before I re-install the wheel. Maybe I should show him the bulletin that Chris posted. Oh well...

As always, YMMV...

Click to expand...

Show him the bulletin. Let us know what he mumbles.

With one nut on the inside, one on outside, how would it be different for Mr. Tube? Except that Tube would now be slightly pushed away from seating up against the rim hole? Have always pulled the valve stem and thus the tube right up to the rim hole, with hole properly lined with tape all'round. The tube if trying to move in the tire may have more leverage to do so, the further it sits away from stem hole? For the tube/tire to move on/in rim, guess you'd have to be doing massive wheelies, burnouts every day, and drag racing all week long? the never ending saga on the double nuts. 2cents.

kantuckid said:

Do we go with BMW & assume improper inflation-maybe the person there was a poor writer?

Click to expand...

No, in your case it's rather a matter of poor interpretation.

If it were my bike, I'd do NOTHING to lock the tube stem into position.

The nut is there simply to aid in installation. After that screw it up to touch the valve cap as BMW specifies. No nuts inside, either.

You ever going to reduce pressure for riding in sand?

:no on the sand, I ride asphalt,concrete & some gravel all which require normal air
Hard to figure that as a "sand tech bulletin"?
Has this become the BMW vs. Kenda thread

I installed another Kenda tube yesterday. I had one in a red box & another in a white box. The red box instructions are worded a bit differently & suggest that the way the nuts are used is for "road use" and lacks the specificity of the white box in that regard, sort of leaving it up to the user to decide. Also on the FWIW I'll ad that both sets of instructions are written by someone with exceptionally good English, not the garbled instructions we sometimes read on Asian items. The Kenda tubes do come from Taiwan.

Read it and weep boys...

Top

User avatar
alan.moore
Holder of a Silver Anorak
Holder of a Silver Anorak
Posts: 604
Joined: Sat Jul 19, 2014 1:29 pm
Location: Leicestershire UK
Contact: Contact alan.moore

Re: Inner Tube Failures

Quote

Postby alan.moore » Mon Mar 23, 2015 10:06 pm
A bit of further info which may be of help to members.

The Michelin tube came with a conical washer and two lock nuts on the stem. A search of many motorcycle forums shows that there is a lot of misunderstanding of where the nuts are fitted, some people advocate one is fitted inside the rim against the washer and the second on the outside. Many people also think they should tighten the outer nut tight against the rim. Such advice is incorrect.

I have checked with Michelin to make sure their advice has not changed and have received the following email from them:


The conical washer sits over the inner tube valve stem and should follow the contour of the valve so that the convex side sits against the wheel rim when fitting.

Once fitted to the wheel the two lock nuts sit on the valve cap side of the wheel rim. After fitment and inflation to the correct pressure, the two nuts should be backed up towards the valve cap, and locked against each other.

This is not usually an issue on correctly inflated road going tyres, but should there be any slippage of tyre on the rim, during heavy braking or acceleration for example, the inner tube could be pulled around slightly with the tyre and if the inner tube is bolted to the rim the valve can be ripped out. If the lock nuts are raised towards the valve cap then inner tube has some leeway to move before this happens. Any movement is thus obvious as the valve stem will no longer be straight and pointing at the centre of the hub, but will be pulled round at an angle.

motorcycle valve fitting.gif
motorcycle valve fitting.gif (4.76 KiB) Viewed 2997 times



I have also seen similar info from Continental tyres who say that the threaded collar should be screwed back up against the valve cap following fitting and inflation.
1939 VH Redhunter;1951 Triumph 6T Thunderbird;1970 BSA B175 Bantam;1986 Yamaha SRX600 single
http://cloggymoore.wix.com/triumph-pre-unit-6t

Welcome to the forum! This is an old thread, but probably something that needs reminding once in a while. Thanks for the blast from the past!

Kurt, This is current SOP for Airheads.

Friedle
Airheads BoD

I know...Snowbum talks about it all the time!

If talc was used to install tube, wouldn't it act as lube to allow tire slip without tube slip? And how hard would a rider need abuse an airhead to get tube/tire slip anywho?