OP
OP
sannesley
Well-Known Member
- Location
- Northern Ireland
Tyre weight
- Thread starter sannesley
- Start date
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vickster
Legendary Member
There should be other sellers. I don't think they've been discontinued. Ribble have some of the coloured ones. The blue look lush on my SS
http://www.ribblecycles.co.uk/sp/ro...elin-pro-4-endurance-folding-tyre/michtyrf221
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OP
OP
sannesley
Well-Known Member
- Location
- Northern Ireland
Just a quick query. My tyres are marked as 700 x 25c. I take it 700 is the circumference of the wheel and 25c is what?
puffinbilly
Veteran
Width
vickster
Legendary Member
S.Giles
Guest
Wouldn't the act of inflating the tyre negate much of the difference in sidewall pliability? I can't see it being much of a factor, but then I've swapped tyre types on bikes I know well, and noticed no difference whatsoever, so maybe I'm just too stupid to care.
Dogtrousers
Kilometre nibbler
Can I join the stupid club? I've been thinking the same. I have ridden recently Durano+ 28s, Durano+ 25s and Marathon+28s and TBH not noticed any difference.
S.Giles
Guest
Welcome aboard! :-)
Yellow Saddle
Guru
- Location
- Loch side.
Oi, you two there in the corner with your silly dunce caps, here's your ticket outta there. Sidewall pliability and by implication rubber thickness of a tyre is the single biggest contributor to rolling resistance of a wheel at speeds where aero drag plays no role. Rubber suffers from poor hysteresis, which means that it absorbs a lot of energy and thus doesn't return all the energy put into flexing or squeezing it. An example is a rubber ball. If you drop it, it doesn't bounce back to the height it was dropped from. The difference is due to energy losses when the rubber was compressed and springs back. The same happens in a tyre. The tyre is squeezed and convert some of the energy into heat, noise, vibration and other stuff I can't think of now. Air on the other hand is better at that and returns more energy than rubber. In other words, an air-filled ball will bounce back higher than a rubber filled ball. The same for tyres, if you can create the same "compressibility" by filling with air rather than putting more rubber on it, you save energy. Thus, thin-walled tyres go faster. Thin walled is difficult to define though but you could weight the tyre (please don't do that, it is so naff) or you could look at the thread count. A higher thread count would indicate a thinner-walled tyre. This is because you can stack more thin threads next to each other in a given distance than thick ones. You need a certain collective strength of thread in the tyre to resist the air pressure and prevent the tyre from becoming bigger with inflation. You can achieve that by using lots of thin ones or a few thick ones. the latter requires more rubber to cover it but is cheaper to make. Indirectly, thread count is an indication of rolling resistance.
Rolling resistance in tyres is also dependent on the tyre's make-up. Tyres with silica (fancy word for sand) in it have less rolling resistance than tyres with carbon black in. However, the latter has better wet and dry grip. Silica tyres come in pretty colours, carbon tyres only in ....black.
Bicycle tyre manufacturers have decided we don't need to know that silica tyres have less grip and don't give us the choice between silica or carbon black - or don't disclose the compound if they do offer a variety. Car tyres all have carbon black in because it's the law.
Rolling resistance in tyres is also dependent on the tyre's make-up. Tyres with silica (fancy word for sand) in it have less rolling resistance than tyres with carbon black in. However, the latter has better wet and dry grip. Silica tyres come in pretty colours, carbon tyres only in ....black.
Bicycle tyre manufacturers have decided we don't need to know that silica tyres have less grip and don't give us the choice between silica or carbon black - or don't disclose the compound if they do offer a variety. Car tyres all have carbon black in because it's the law.
S.Giles
Guest
...all of which adds-up to a difference too small for me to notice!
Actually, I'm quite glad I don't notice these things. I can concentrate on more prosaic tyre qualities such as puncture-resistance, durability, ease of availability and price.
(Edit: Thanks for the explanation though, which is genuinely interesting. I think my original assertion is correct, though. The more air pressure there is in a tyre, the less the hysteresis of the rubber will come into play. For instance, if the tyre could be inflated to an infinite pressure, the rubber wouldn't flex at all, so the rubber's inherent hysteresis wouldn't matter at all. We're not in quite that situation, but it serves to illustrate my point.)
Actually, I'm quite glad I don't notice these things. I can concentrate on more prosaic tyre qualities such as puncture-resistance, durability, ease of availability and price.
(Edit: Thanks for the explanation though, which is genuinely interesting. I think my original assertion is correct, though. The more air pressure there is in a tyre, the less the hysteresis of the rubber will come into play. For instance, if the tyre could be inflated to an infinite pressure, the rubber wouldn't flex at all, so the rubber's inherent hysteresis wouldn't matter at all. We're not in quite that situation, but it serves to illustrate my point.)
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U
User6179
Guest
Wouldn't the act of inflating the tyre negate much of the difference in sidewall pliability?
No
Yellow Saddle
Guru
- Location
- Loch side.
No, you still have the rubber on the contact patch that compresses between the road and the air cushion. Air pressure has a linear effect on rolling resistance up to a point of about 8 bar, where the curve flattens out and you get diminishing returns. The difference in teeth rattling between 7 and 10 bar and the corresponding small reduction in rolling resistance makes the old practice of the harder, the better, moot. We still want the rubber (tyre and tube btw) to be as thin as possible.
But like you say, it really doesn't matter to most of us who ride for beer, not trophies.
winjim
Smash the cistern
I was merely pointing to the information. (OP paragraph 1)
I shall leave it to others to interpret it and debate its usefulness. (OP paragraph 2)
Globalti
Legendary Member
I would rather ride a light, supple tyre and risk a few punctures especially as I don't cover huge distances. I was a Pro 3 then Pro 4 fan for a few years but have now discovered the delights of Veloflex Corsas, which do cut up a little but they grip superbly, feel really well planted even on wet roads and are super comfy. They don't seem any more vulnerable to punctures than any other tyre. Today I fitted some latex inners that I got for my birthday and pumped the Veloflex to 110 lbs; superbly smooth and they feel very fast.
OP
OP
sannesley
Well-Known Member
- Location
- Northern Ireland
After all the discussion I was checking over the bike last night and found that a small section of the front tyre, about 3cm, has come away from the bead and is bulging out when pumped up to 80 PSI. It's probably because when I change a puncture some months back out on a run I didn't set the wheel back on the forks right and it was rubbing on something for a few miles before I figured out what the noise was. I reset the wheel but noticed that it had caused some wear damage to the tyre.
To be on the safe side I'm going to change the front tyre as I don't want to risk anything disastrous happening when out on a ride miles from home.
I was thinking of only changing the front tyre or would I be better changing both? There's plenty of life in the rear tyre yet.
To be on the safe side I'm going to change the front tyre as I don't want to risk anything disastrous happening when out on a ride miles from home.
I was thinking of only changing the front tyre or would I be better changing both? There's plenty of life in the rear tyre yet.
