The Mysteries of Tube Replacement

[jb]

Funny things valve nuts, they don't really serve much of a purpose any more. Once there was a nut on both sides so you could tighten them up proper like.

Although they do stop the valve disappearing down the hole when pressing the pump nozzle on but this is easily prevented by pressing into the tyre.

[rogerzilla]

The only lever I'd use for fitting would be the VAR "bead jack" type. I have one but have only ever needed it once, on someone else's tyre.

[gregoryoftours]

I fit one side of the tyre to the rim, then put the tube (with a little air in it to give it shape) in the tyre starting at the valve, then the other tyre bead ideally without tyre levers. Before you fully inflate the inner tube first push the valve back into the body of the tyre so there's only a stub showing through the rim valve hole. Then manipulate the tyre beads at the valve. Once they're seated properly the valve can be pulled back out again and the nut fitted/tightened if you have one. Most bulges at the valve are caused by this step being missed. If the valve is pulled fully through the rim the tube doesn't allow the tyre beads to seat properly where the valve is. By pushing the valve back you are moving the inner tube out of the way up into the tyre as you seat the bead at the location of the valve.

[jacobean]

I fit one side of the tyre to the rim, then put the tube (with a little air in it to give it shape) in the tyre starting at the valve, then the other tyre bead ideally without tyre levers. Before you fully inflate the inner tube first push the valve back into the body of the tyre so there's only a stub showing through the rim valve hole. Then manipulate the tyre beads at the valve. Once they're seated properly the valve can be pulled back out again and the nut fitted/tightened if you have one. Most bulges at the valve are caused by this step being missed. If the valve is pulled fully through the rim the tube doesn't allow the tyre beads to seat properly where the valve is. By pushing the valve back you are moving the inner tube out of the way up into the tyre as you seat the bead at the location of the valve.

I'm learning all new things here....

After fitting to the inside of the tyre, I've always pulled the valve out, far as possible, sometimes even securing it with a spacer. Then I would inflate. I always thought that once air gets into the tube (and assuming one had not been a complete idiot in positioning tube inside), that the air would make the tube would take shape inside the tyre?

[PH]

Something I was taught to do as a child, and until recently assumed everybody did, was once you get to the tight part of re-fitting, remove about a quarter of the bead and carry on, so that the last part had already been on once. Anyone else? Am I the only one...

[MikeDee]

A friend of mine mounts a tire by inflating the tube just enough to give it a donut shape and placing it in the tire, then mounts the tire to the rim. Seems to work for him and looks like you would be less likely to pinch the tube that way. I'm gonna try it next time I change tires. When I'm dealing with a flat though, I'll stick with the tried and true method; i.e. removing the whole tire rather than one bead seems like extra work to me.

[Jamesh]

A friend of mine mounts a tire by inflating the tube just enough to give it a donut shape and placing it in the tire, then mounts the tire to the rim. Seems to work for him and looks like you would be less likely to pinch the tube that way. I'm gonna try it next time I change tires. When I'm dealing with a flat though, I'll stick with the tried and true method; i.e. removing the whole tire rather than one bead seems like extra work to me.

Why didn't I think of that!!

Cheers James

[gregoryoftours]

After fitting to the inside of the tyre, I've always pulled the valve out, far as possible, sometimes even securing it with a spacer. Then I would inflate. I always thought that once air gets into the tube (and assuming one had not been a complete idiot in positioning tube inside), that the air would make the tube would take shape inside the tyre?

The tube can get in the way when seating the tyre beads in the area of the valve, so it's best to push the valve and tube up inside the tyre at this spot. Once the tyre beads are properly seated at the valve, the valve can be pulled out again and inflated fully as normal.

You can see what I mean with these cross section views of rim, tyre and tube.

In this first one the left hand tyre bead is seated and locked in where it needs to be, but with the valve pulled down the right hand bead is obstructed by the thicker rubber around the tube valve (painted white to see easily).

If you push the valve up into the rim it gets the tube out of the way and there is a clear path to seat the bead without the risk of the tube getting caught underneath it:

Then you can pull the valve back down and fully inflate as normal with both of the tyre beads seated properly:

[jacobean]

@gregoryoftours

That is brilliant - thanks.

I will never be pulling the valve down again!

It looks like a heart valve in medical textbook. I wonder if heart surgeons good at fixing punctures...

[gregoryoftours]

@gregoryoftours

That is brilliant - thanks.

I will never be pulling the valve down again!

It looks like a heart valve in medical textbook. I wonder if heart surgeons good at fixing punctures...

To clarify, I think that it's a good idea to push the valve up out of the way inside the tyre while seating the bead at the valve, but then a good idea to pull it back down again before final inflation, as otherwise you can get problems with the tube doubling in on itself at the valve. Yes I bet that heart surgeons are sh*it hot at fitting tyres!

[jb]

After fitting to the inside of the tyre, I've always pulled the valve out, far as possible, sometimes even securing it with a spacer. Then I would inflate. I always thought that once air gets into the tube (and assuming one had not been a complete idiot in positioning tube inside), that the air would make the tube would take shape inside the tyre?

The tube can get in the way when seating the tyre beads in the area of the valve, so it's best to push the valve and tube up inside the tyre at this spot. Once the tyre beads are properly seated at the valve, the valve can be pulled out again and inflated fully as normal.

You can see what I mean with these cross section views of rim, tyre and tube.

In this first one the left hand tyre bead is seated and locked in where it needs to be, but with the valve pulled down the right hand bead is obstructed by the thicker rubber around the tube valve (painted white to see easily).received_273080204295637.jpeg

If you push the valve up into the rim it gets the tube out of the way and there is a clear path to seat the bead without the risk of the tube getting caught underneath it:received_146640560722267.jpeg

Then you can pull the valve back down and fully inflate as normal with both of the tyre beads seated properly:received_299830548376098.jpeg

I don't know if that example in the picture is just for demonstration but its best if the tube is almost the size of the tyre, otherwise it can get very thin even if the box says its ok. Properly sized tubes tend to be harder to fit as its easier to nip them but having the extra thickness is worth it.