Presta (not schrader) issues

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YMFB

Well-Known Member
Last weekend I’d rode my road bike on three consecutive days. Saturday 18 miles, Sunday 18 miles followed by 67 on the Bank Holiday Monday. On the Saturday evening I’d replaced the valve core and refreshed the sealant on my slow leaky rear tyre had it had been no further problem. Yesterday , nearly a week later I had to top up both tyres before heading out but thought nothing of it.

All was good until Amesbury, about 15 miles where i realised my rear needed a top up, which I did with my mini hand pump. We got to Upavon and it needed another, at Pewsey after coffee and cake another top up, in the end it seemed every 8-10 miles it needed attention, somewhere I tried changing the core, but they appeared to have different threads. We called in at The Marlborough bike shop, they looked at it and at my suggestion changed the valve core and as there was no obvious leak suggested I change the rim tape later. As the tyre was properly inflated it lasted a lot longer, but still leaked.

60 miles in and near Devizes, time for lunch at the highly recommended Rowdey Cow. The Sausage ciabatta was excellent. I topped up the rear as we were leaving, in the village of Keevil I topped up again and thought it hadn’t lost as much air, wrong ! Only a few miles later somewhere near Steeple Ashton it gave up. We found a gateway, removed the wheel and fitted a TPU tube, that bit was easy. Inexplicably my pumps hose would not screw onto the valve stem, luckily my friends.

Are there different threads for Schrader valve cores and can TPU tubes have a different thread or am unlucky that I had these issues when it was raining on my longest ride.
 

Punkawallah

Veteran
Have you checked for leaks with a bucket of water?
 

oxoman

Senior Member
As punkawallah suggests, check for leak in water. I've had replacement valve cores purchased from the bay of plenty not seal properly when I've fitted them. The little rubber seal looks to be cheap and nasty on the ones that have failed. Perhaps the machining on your replacement cores is poor as well. Also are you sure on the valve type. See the pic. Plus there's the new schwalbe clik ones.

1000024044.png
 

Dogtrousers

Kilometre nibbler
Are there different threads for Schrader valve cores and can TPU tubes have a different thread or am unlucky that I had these issues when it was raining on my longest ride.
I'm confused. Did you mean Schrader? or did you mean (as the thread title says) "Presta (not schrader)"

Presta and Schrader valve cores look different (Presta on the right below). I've no idea what the threads are.
1756640193804.png

fitted a TPU tube, that bit was easy. Inexplicably my pumps hose would not screw onto the valve stem, luckily my friends.
Did I dream it or did I read that some presta valves are unthreaded (for the pump)? Maybe the TPU tube was one of these So if you have a screw on pump rather than a clamp on pump you may be stuffed.*

Sounds you have a leaking tyre, and are focusing on the valve core as being the cause. But maybe it isn't that. As suggested above check for all kinds of leaks. Small punctures, rim tapes, and also the valve stem itself. Maybe the cores are blameless but there's a flaw or gunk in the stem or the bung thing at the base is leaking.

* Edit: I didn't dream it. I found something to this effect on t'internet. It may or may not be true, it's just something I've read. Personally I have zero experience of TPU tubes:
The main drawbacks for TPU Tubes are that they don't have a threaded Valve Stem. They just have a small amount for the Dust Cap. So if you have a mini-pump that threads on to the Valve Stem (I have a Topeak Race Rocket), you'll need to buy another pump. I've been on numerous bike rides where other non-thread on mini-pumps, looking at you Lezyne, were tried, but invariably, the Race Rocket is always whipped out to get proper pressure into the tyre.
Maybe you're thinking, "sure I'll just use CO2 to inflate the TPU Tube". Be warned, if you use a CO2 Cartridge and Inflater, it'll freeze and crack the Plastic Valve Stem.
 
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YMFB

Well-Known Member
Definitely Presta.

The core on the LHS fits, the core on the RHS does not.

whilst I can’t see any obvious defect, I think the RHS has a bad thread. It was in a bag, but I do not know where it came from.
 

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YMFB

Well-Known Member
This is TPU tube that I couldn’t inflate with my mini pump.

I haven't used CO2 on anything but a tubeless setup
 

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YMFB

Well-Known Member
This morning I removed the inner tube, cleaned up the tyre and valve stem. I haven’t got the correct rim tape so will drop it in to the LBS tomorrow to reassemble.
 
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