Just to take a break from uploading all those pictures from our recent mountain ride to Montenegro (couple of days left to write up, then there’s the hiking holiday on Durmitor to tell you all about!) - here’s a bit of bike techie stuff, which I don’t usually bother with that much with on this blog. Was idly chatting with a friend the other day - I had got a snakebite puncture the day before and we got talking about tyre pressures. And I realised I have got really sloppy this summer about tyre pressure: I have been too lazy (well, too busy cycling up steep hills, hardly lazy) to go to the bike shop and pump my tyres up properly, rather I have been just topping up with the hand-pump all the time, with the result that over the summer my tyre pressures have got lower and lower, hence the snakebite puncture, caused by a relatively innocent bump whacking the rim against the ground and pinching the inner tube.
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Does tyre pressure matter?
Thought I actually try and learn something about this, so have had a quick look around various biking resources. Basically it boils down to a trade-off:
higher pressure = less friction, easier pedalling, easier progress, but also less traction, poorer control
lower pressure = more friction, harder pedalling, more energy expended, but better control, especially downhill, on technical stuff etc.
Seems at the end of the day that it’s a matter of riding style, like everything else, together with a question of taste. Probably if you are a fearless downhill rider who doesn’t expect to make up much time on the climbs, then you will be happy with a lower pressure. If you are a lily-livered coward on the downhills, like me, but have got some fitness for those uphills (or you are mostly riding on the flat, or on tarmac), you might be better off with a higher pressure that will help you eat up those climbs. So it seems it does matter. The advice seems to be: start with a fairly high pressure, like over 3 bar, and then gradually let off the pressure bit by bit to find the highest pressure that suits your riding style.
Benefit of hindsight
So, had a go today, pumped up to around 3 bar (about 40 psi, I think, seemed incredibly hard compared to how I had had it before!) and went off to try my favourite training hill (from Paragovo on the approach to Fruška gora, up to the first official marathon checkpoint at Stolovi, quite an evil climb). Shaved my time down from just under 27 minutes for the climb, to about 25m 30s! So I was well impressed with my new discovery! If only I had thought a bit more about this early on in the year, I might have found all those epic treks across Serbia a tad easier! But then you could see it as a sort of effective resistance training too..!
I must also add that I then tackled a rather steep and rutted descent and could definitely feel the loss of traction, but then I would probably take it easy anyway down those.
Update: I tried a real tricky, steep descent with a sharp turn at the bottom a day later and discovered that I WILL have to let the pressure off a little! I couldn’t descend too fast because of the turn, but the high pressure in the tyres was making them bounce around all over the place, especially as I was braking, and I really lost traction. It was quite hair-raising, since I HAD to maintain a higher speed in order to keep control of the bike, but that turn at the bottom nearly wiped me out…!
So I have definitely learned something this week - erm, pump up your tyres, but not too hard! More words of wisdom soon!
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Posted on September 1st, 2008 by markowe
Filed under: Bike repair, Biking - general, MTB Serbia (All)
he, he, I told you so!
Yes, I’m “all pumped up” to ride now