A post by Lord Sugar on twitter made me think about some experience recently with my bike;
Just done a 60 mile bike ride up coast in Florida(total 280 miles this week) no flats since I changed to Continental Grand Prix 4000 tyres
I also use Continental GP4000 tyres, and have done for a couple of years. They are brilliant. Everyone I know who rides a bike I’ve evangelised about them to – and quite a few have moved to them. The current set on the bike have been on it now for nearly 2 years. They were the new type (GP4000S) that had just come out when I got the bike replaced when the rear mech decided to self destruct.
The bike has now done near enough 5000 miles on the same set of tyres. In fact, I’ve not had a puncture since I put them on. (They’re the 700x23C road bike type, although to look at them they are much rounder than normal tyres – at first look, they seem like a 25).
However, I did find an issue – but not with the tyres.
I went in the garage early on a saturday morning a few weeks back ready to go on a ride to find the tyre flat at the front. Oh sod. But I couldn’t believe I’d got a puncture – because I have the tyres pumped up so high (usually 120psi) if I get a flat it manifests itself very quickly – Usually whilst I’m still on the bike as I’m not a light kind of guy. I use conti tubes too – again – both in my MTB and Road Bike. It’s not just the bright yellow dust caps (I know – thou shalt throw them in the bin according to ‘the rules’) but they also seem to be bombproof.
So I whipped off the wheel and tried to re-inflate the tyre to see if I could find where the issue was. I screwed down the end of the presta valve after inflating but there was a definite hiss coming from what seemed to be the valve hole in the rim. I wonder if 2 years of riding had weakened the valve seat or there was a slow puncture somewhere.
So I deflated it all and took the tube out, pumped it up a bit, and filled a bucket with water. I immersed the tube section by section to see where the hole was.
No hole.
How bizarre. Yet I could hear it hissing.
I submerged the valve – and a little stream of bubbles appeared from the valve. But it was screwed right down. How strange.

When presta valves were first put on bike tubes, they didn’t have removable cores like a schrader valve (like the one on your car) does. This caused problems for tubeless tyres, so people like continental and specialized came out with removeable cores. I didn’t know this, so was puzzled as to why what I thought was a sealed valve was leaking. So a bit of googling and I found that a valve that has flat bits on either side of the cap thread is a removeable core, like the picture on the left. The conti tubes I have had these flat bits.
So I got a small pair of pliers, popped out the core, put a tiny bit of lube on the o-ring (the diver coming out in me here!) and popped the core back in. Once tight, putting the tube back into the tyre it inflated perfectly and has stayed inflated since.
In a twist of fate, my rear tyre was flat a few days later and it was the same symptoms – I did the same core remove / lube / replace and it’s been fine too.
Even funnier is that I’ve recently measured my chain with a chain gauge, and I need a new 9-speed chain. So my tyres have outlasted my chain.
And better than that – I’d only had the bike with these tyres in a few weeks when it threw a spoke at the rear. The aerodynamic spokes were such a pain on the Miche wheels and with my local bike shop struggling to get stock in (and with me hating the wind shear I got from aerodynamic spokes) I relegated them to the turbo trainer and bought a nice set of Halo Rims which have done me proud for the best part of 4000 miles – with these tyres and tubes having survived that too – so without a puncture I’ve changed wheels and chain!
Continental GP4000′s rule.
Note – I bet I get a puncture before the weekend having written this now