Frequent rear wheel punctures from Brompton rim

[rogerzilla]

On a couple of Bromptons over the years, I've had irritatingly frequent rear punctures, always when the bike is parked, that are traceable to a badly-finished rim hole. The sharp edge chafes at the base of the valve stem, presumably as the tyre deforms under pedalling forces, and then deflates shortly after the ride. The tube, of course, is unpatchable and ruined.

I have run a small round file in the hole to remove burrs, but the problem is that the two walls of the rim are pushed together in the middle, leaving a small gap between them. These are the rims used until a few years ago, not the latest type.

Any suggestions for a workaround to line the hole? I really don't want to rebuild the wheel unless I have to.

 

[Ian H]

Are Brompton-sized tubes available with Presta valves? If so you could use a plastic adaptor to reduce the hole & protect the valve stem.

 

[cougie uk]

There must be some tape you could run around it ? Insulation tape maybe -. Couple of wraps ?
That said you should also be able to file it smooth.

 

[u_i]

I have run a small round file in the hole to remove burrs, but the problem is that the two walls of the rim are pushed together in the middle, leaving a small gap between them. These are the rims used until a few years ago, not the latest type.

Any suggestions for a workaround to line the hole? I really don't want to rebuild the wheel unless I have to.

What about using an L-shaped hex key, wire or old spoke bent into an L with a short arm and putting it through the hole to the space in-between? Turning it around you might be able to remove any burrs sticking to the inside. I actually even have a Dremel burr bit that is an inverted cone, specifically for dealing with burrs when there is no access to the other side of the hole.

 

[Bee]

On a couple of Bromptons over the years, I've had irritatingly frequent rear punctures, always when the bike is parked, that are traceable to a badly-finished rim hole. The sharp edge chafes at the base of the valve stem, presumably as the tyre deforms under pedalling forces, and then deflates shortly after the ride. The tube, of course, is unpatchable and ruined.

I have run a small round file in the hole to remove burrs, but the problem is that the two walls of the rim are pushed together in the middle, leaving a small gap between them. These are the rims used until a few years ago, not the latest type.

Any suggestions for a workaround to line the hole? I really don't want to rebuild the wheel unless I have to.

I suppose you are using the stock Brompton inner tubes (or similar)? You might try switching to Schwalbe AV4 which has an all-metal valve stem. These are also lighter than the stock tube, and the valve stems are threaded for a lock-ring. Currently available on Amazon for under 6 quid with free delivery.

 

[presta]

The solution is so simple I've never understood why anyone would have more than one of these punctures.

1. De-burr the hole. My tool of choice for de-burring aluminium is the back of my scalpel blade, it leaves a shiny polished finish.
2. Fit leather washers around the base of the stems. An old shoe will do if you don't have any other leather to cut them from.
3. Don't use direct fitting pumps with no hose. They cause unnecessary wear by ricking and twisting the stem as you use them.

It's 20 years since I had my one and only puncture of this kind and there's no sign of any wear on the leather washers yet, in fact they've actually acquired a high polish.