Inner tubes with AVon tubeless tyres

[Jollyharbour]

Hello, hoping someone can help. Following my 1st puncture in my 1972 911, i find i have inner tubes in my Avon "tubeless" CR6ZZs. Original Fuchs. Is this ok/usual? I am guessing inner tubes may be necessary with this age of wheel but thought best to check. Thanks.

[Lightweight_911]

I've never fitted tubes to Avon CR6ZZ tyres - I've had them on 356C steel, 904-style steel/alloy, deep six & flat six Fuchs wheels without any problems over the past 10 yrs or so.

[fetuhoe]

The problem with using tubes with Tubeless Tyres is concerned with the risk of tube failure.

Tubed tyres used to be manufactured with very smooth inner walls and were always finished by being dusted with French Chalk which served to ‘lubricate’ the tyre to tube interface.

In use there is significant relative movement between the tyre and the tube and the very rough finish inside a modern Tubeless Tyre means that tubes will either chafe and potentially rub into holes or heat up significantly causing more than usual pressure variation.

In extreme cases the chafing can lead to the tube being punctured and then as the valve doesn’t seal well into the rim deflation can be quite rapid.

I am not sure that Tubes fitted in Tubeless tyres is the best policy.

[Nick Moss]

Are your rims tubed or tubeless? Most, if not all 1972 911s, will be on tubeless rims

[George Eakley]

I wouldn't ever (again!) put tubes in tubeless tyres having suffered two punctures whilst competing, for exactly the reasons stated above.
The inner faces of the Cr6 ZZ tyres that I was running punctured the tubes via chafing.
My advise would be to remove the tubes without delay!
Good luck......

[PhilipB]

The issue with getting rid of the tubes is that it's very hard to get hold of valves that will properly seat in Deep 6 rims. The TR415s you can get easily don't seat properly. I haven't found anyone who can mod the valve holes.


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[inaglasshouse]

Hi Philip,
Quite right about the problem of course, but I know various folks have had the rims machined to allow the TR415 valve to properly seat.
Andy lightweight and Darren, off top off head. Rich Murphy as well, I think.
Over to you, experts - who did the machining for you?
Cheers, Richard.

[Lightweight_911]

I think Philip is talking about finding somebody here in the UK - the deep six & 7R Fuchs wheels I've had machined were all done by Harvey Weidman during refurbishment.

[inaglasshouse]

Aha, I see.

Relevant thread here with pics of the machining posted by Darren and Rich. All done by Mr Weidman I think.
viewtopic.php?f=2&t=51006&p=436832#p436796

But it doesn't look like rocket science? Magnus did his own machining:
viewtopic.php?f=2&t=56757&p=495245#p495245


I would have thought that many machine shops could handle it? Or am I missing something tricky?

[Darren65]

Correct that Harvey W also restored wheels for Richard and I....consequently I've done over 8,000 miles in mine without issue.

As you say it looks fairly straightforward, I'm sure Nick Moss could help

[911SE]

Correct, there's no rocket science to this. The hole diameter doesn't need changed, you're just after getting some parallel surfaces to get the valve to seat. I don't remember the diameter used on the mill bit as this was a couple of years ago but from memory I used one with slightly smaller diameter than the valve itself.

Tip, don't be tempted to machine the recesses deep enough to get perfectly looking paralell seating surfaces, in my opinion there won't be enough material left with would affect the integrity of the rim, the valve is pliable enough to seat.

[Nick Moss]

I'm sure any machine shop could do this if told the dimensions, but they should be wary of any legal comeback. I would not want to be involved, and I won't refurbish 3 piece rims either.

[PhilipB]

Until Harvey Weidman emigrates to the UK I think I'll carry on with the inner tubes!


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[inaglasshouse]

While enjoying the irony that the only person not worried about product liability is American...

[Jollyharbour]

Thank you all for your replies - not straightforward. I am going to stick another tube in for now to get me back on the road, and later to look at the valve seating for tubeless.