Confused abt tyre pressure

thomas_cho said:

Hi all,
This topic surely must have been discussed before, but I dont seem to be able to search out the threads.

Does a higher tyre pressure (120psi) help to eliminate punctures?

I am using Rubino pro 700x25 tyres, and while testing out my "freshly built wheels", picked up a puncture within 2km of home. A glass shard had attached itself to my tyre and pierced the tyre.

I had inflated my tyres to aprox 95psi in the front and 105psi on the rear.

I fixed up the puncture, and inflated the tyres to 120psi front and rear, and went out again. This time, 96km later, no punctures, even though I had to ride through parts which were littered with glass, and [censored].

The previous I had a puncture, I was also using a Rubino pro tyre, inflated to 105 psi.

On most weekend rides, I ride on my Giant OCR with tyres inflated to 120psi, and I never get a puncture. Its only on my commute bike, where I "under" inflate the tyres to get a better ride, that I experience the punctures.

Now, is this a tyre problem ( are vittoria rubino pros a poor choice? I got Michelin Pro2 race on the Giant, and have found glass embedded in the tyre, but they never pierced the tube), or a tyre pressure problem (lower pressure vs higher pressure)? Or I just have an affinity for glass that are shaped to penetrate the kevlar belt?

After doing the maths, the commuting has cost me about $12 and negated the petrol savings from commuting on bike. 😠

Higher pressures don't eliminate puntures and they may cause lower grip due to bouncing over the surface rather than conforming to it.
Tire choice makes a big difference. Try the Conti GP4000 as they seem to be fairly puncture resistant. We use the 28c Gatorskins on the tandem which are even tougher.
On your commuter bike, there is most probably more [censored] on the road than where you do your training.
FWIW I used to use speacialized turboS tyres that cost a bomb about $50 each. I used to go through a pair a month, so my tyre bill for the year was around the $1200. I was fit though!

Cheers

Geoff

thomas_cho said:

Hi all,
This topic surely must have been discussed before, but I dont seem to be able to search out the threads.

Does a higher tyre pressure (120psi) help to eliminate punctures?

I am using Rubino pro 700x25 tyres, and while testing out my "freshly built wheels", picked up a puncture within 2km of home. A glass shard had attached itself to my tyre and pierced the tyre.

I had inflated my tyres to aprox 95psi in the front and 105psi on the rear.

I fixed up the puncture, and inflated the tyres to 120psi front and rear, and went out again. This time, 96km later, no punctures, even though I had to ride through parts which were littered with glass, and [censored].

The previous I had a puncture, I was also using a Rubino pro tyre, inflated to 105 psi.

On most weekend rides, I ride on my Giant OCR with tyres inflated to 120psi, and I never get a puncture. Its only on my commute bike, where I "under" inflate the tyres to get a better ride, that I experience the punctures.

Now, is this a tyre problem ( are vittoria rubino pros a poor choice? I got Michelin Pro2 race on the Giant, and have found glass embedded in the tyre, but they never pierced the tube), or a tyre pressure problem (lower pressure vs higher pressure)? Or I just have an affinity for glass that are shaped to penetrate the kevlar belt?

After doing the maths, the commuting has cost me about $12 and negated the petrol savings from commuting on bike. 😠

No, the problem is not your tyre pressure or the tyres. Most people using those tyres are happy with their puncture resistance. Commuting can attract more punctues than training simply because you are riding on dirter road when commuting as distinct from training, where you are usually riding two abrest on a lane sweeped clean by the cars. There is also an element of luck, I have had exactly 5 flats per year for the last 3 years and this year I have had none so far.

In regards to pressure, how much do you weigh? the commuting pressures you are quoting sound a little soft.

I weigh about 95kg.

Thing is the state of the commute route is almost the same as the weekend riding routes. I ride over glass, and the muck as well, but no punctures on the weekend only during the weekdays.

I was about to slap on some GP4000s, but I am going to stay with the Rubinos for a while more, just to see if my luck changes for the better.

FWIW, I went without a puncture for almost 1 year, and almost always went out without a spare tube or pump. Getting the first puncture was probably good for me, as now I carry a tube (at least one) and a pump, even for 5km test rides.

thomas_cho said:

Hi all,
This topic surely must have been discussed before, but I dont seem to be able to search out the threads.

Does a higher tyre pressure (120psi) help to eliminate punctures?

I am using Rubino pro 700x25 tyres, and while testing out my "freshly built wheels", picked up a puncture within 2km of home. A glass shard had attached itself to my tyre and pierced the tyre.

I had inflated my tyres to aprox 95psi in the front and 105psi on the rear.

I fixed up the puncture, and inflated the tyres to 120psi front and rear, and went out again. This time, 96km later, no punctures, even though I had to ride through parts which were littered with glass, and [censored].

The previous I had a puncture, I was also using a Rubino pro tyre, inflated to 105 psi.

On most weekend rides, I ride on my Giant OCR with tyres inflated to 120psi, and I never get a puncture. Its only on my commute bike, where I "under" inflate the tyres to get a better ride, that I experience the punctures.

Now, is this a tyre problem ( are vittoria rubino pros a poor choice? I got Michelin Pro2 race on the Giant, and have found glass embedded in the tyre, but they never pierced the tube), or a tyre pressure problem (lower pressure vs higher pressure)? Or I just have an affinity for glass that are shaped to penetrate the kevlar belt?

After doing the maths, the commuting has cost me about $12 and negated the petrol savings from commuting on bike. 😠

Thomas, I don't think that your sample size of one puncture per tyre lifespan allows you to decide anything beyond how lucky you are.

thomas_cho said:

I weigh about 95kg.

Thing is the state of the commute route is almost the same as the weekend riding routes. I ride over glass, and the muck as well, but no punctures on the weekend only during the weekdays.

I was about to slap on some GP4000s, but I am going to stay with the Rubinos for a while more, just to see if my luck changes for the better.

FWIW, I went without a puncture for almost 1 year, and almost always went out without a spare tube or pump. Getting the first puncture was probably good for me, as now I carry a tube (at least one) and a pump, even for 5km test rides.

95Kg - I'd go for 120 in the rear and 110 in the front.

GP4000s - Have better rolling performance than the Rubino's, but they won't improve puncture protection.

Almost a year without a puncture is a very good run. One thing you can do is to check each cut in the tyres every day for glass or other foreign objects, as often the item causing the puncture can take several days to get to the tube.

mikesbytes said:

95Kg - I'd go for 120 in the rear and 110 in the front.

GP4000s - Have better rolling performance than the Rubino's, but they won't improve puncture protection.

Almost a year without a puncture is a very good run. One thing you can do is to check each cut in the tyres every day for glass or other foreign objects, as often the item causing the puncture can take several days to get to the tube.

I'm 90kg, use 700Cx23mm and ride on rough roads. I tend to inflate to 80-85psi on the front and 110-115 on the rear. I have had one pinch flat in ~9000km, when I hit a large rock (rear, although both wheels hit it). I think that your pressure recommendations, mikesbytes, are a little high for 25mm tyres, especially on the front. Too much pressure on the front puts you in greater danger of front wheel skidding or locking, and is less comfortable.

Arte, you are quite right, I have been lucky. Now I really should put some money towards the $21m lotto.

artemidorus said:

I'm 90kg, use 700Cx23mm and ride on rough roads. I tend to inflate to 80-85psi on the front and 110-115 on the rear. I have had one pinch flat in ~9000km, when I hit a large rock (rear, although both wheels hit it). I think that your pressure recommendations, mikesbytes, are a little high for 25mm tyres, especially on the front. Too much pressure on the front puts you in greater danger of front wheel skidding or locking, and is less comfortable.

I don't know what tyres you are using, What I'd put in Rubinos if I weighed 95kg is 110 front and 120 rear. At 90kg I'd put 105 front and 115 rear in Rubinos. With Pro race 2's I would go about another 5psi softer. It does depend on you experience, if you are less confident, then it is probably better to go a little softer.

If you are riding on rough roads, why are you using 23mm tyres?

Actually my experiance is slightly lower pressure reduces flats. It allows your tyre to "give" a little over sharp objects, not to mention the ride comfort on rougher roads. Im under 80 kgs which gives me a little more flexability with pressure than a 95 kg rider.

mikesbytes said:

If you are riding on rough roads, why are you using 23mm tyres?

There's rough and there's rough - these are ordinary sealed Sydney roads, not firetrails or gravel paths. 23mm work for me (although I have had some problems with spoke breakage). I don't want larger tyres because they would make the bike seem slower to me, even if it wasn't.

artemidorus said:

There's rough and there's rough - these are ordinary sealed Sydney roads, not firetrails or gravel paths. 23mm work for me (although I have had some problems with spoke breakage). I don't want larger tyres because they would make the bike seem slower to me, even if it wasn't.

I use 23mm as well. 23mm give better aerodynamics than 25mm but the 25mm tyres roll better, ie lower rolling resistance, so it depends on how fast you ride.

Where in Sydney to do you ride? Which tyres do you use? How have you gone with punctures?

mikesbytes said:

I use 23mm as well. 23mm give better aerodynamics than 25mm but the 25mm tyres roll better, ie lower rolling resistance, so it depends on how fast you ride.

Where in Sydney to do you ride? Which tyres do you use? How have you gone with punctures?

The rolling resistance of a tyre depends on the bumpiness of the surface. On the track, 19-21mm roll the best. On "typical" road surfaces (possibly not Sydney's!), 23 mm is said to offer the lowest rolling resistance. Off-road, or on very rough asphalt, larger tyres offer the lowest rolling resistance. Your point about wind resistance is definitely accepted. These points have been debated at length on this group and I'm paraphrasing my synthesis of the various arguments.
I commute between Erskineville and Randwick and ride in various directions for "leisure". I'm on to the last tyre of two pairs of ProRace, and have fitted my first GP4000. I've suffered one pinch flat and one glass flat that I can remember in 9000km. (I'm not counting one ruptured tube when I forgot to refit my rim tape after replacing a spoke). I've had many more broken spokes than flat tyres. My MTB, used much less, has had more punctures in that time! I won't bore you with stats for that old bike, even if I could remember them.
And you?

artemidorus said:

The rolling resistance of a tyre depends on the bumpiness of the surface. On the track, 19-21mm roll the best. On "typical" road surfaces (possibly not Sydney's!), 23 mm is said to offer the lowest rolling resistance. Off-road, or on very rough asphalt, larger tyres offer the lowest rolling resistance. Your point about wind resistance is definitely accepted. These points have been debated at length on this group and I'm paraphrasing my synthesis of the various arguments.
I commute between Erskineville and Randwick and ride in various directions for "leisure". I'm on to the last tyre of two pairs of ProRace, and have fitted my first GP4000. I've suffered one pinch flat and one glass flat that I can remember in 9000km. (I'm not counting one ruptured tube when I forgot to refit my rim tape after replacing a spoke). I've had many more broken spokes than flat tyres. My MTB, used much less, has had more punctures in that time! I won't bore you with stats for that old bike, even if I could remember them.
And you?

I use to think that too, that skinner gave lower rolling resistance, until I read up on the topic. At 40kmh we have 80% wind resistence and 20% rolling resistence, so a narrower tyre wins out for faster riders. Tyre sizes and pressures are a hot topic.

BTW, the recommended pressures for Rubino's is 100psi minimum 125psi maximum.

mikesbytes said:

BTW, the recommended pressures for Rubino's is 100psi minimum 125psi maximum.

BTW, Specialized All Condition Sport, Pro & Armadillo, tyre pressure rating is 115 Min 125 Max. The max I understand, but this minimum makes no sense to me at all. [if anyone has an explanation please post] If I use the max I feel more like a milkshake on rough roads so its [25mm] 95/100 front 105/110 rear, depending on the rough factor of the ride I’m going on

artemidorus said:

I'm 90kg, use 700Cx23mm and ride on rough roads. I tend to inflate to 80-85psi on the front and 110-115 on the rear. I have had one pinch flat in ~9000km, when I hit a large rock (rear, although both wheels hit it). I think that your pressure recommendations, mikesbytes, are a little high for 25mm tyres, especially on the front. Too much pressure on the front puts you in greater danger of front wheel skidding or locking, and is less comfortable.

Art, I've noticed your threads re spokes before & although you do not wish to use 25mm tyres, they may, given the extra height, take a little pressure off the spokes over the bumps🙂

A rough guide to tyre pressures from Sheldon Browns site

Wheel load 50 mm 37 mm 32 mm 28 mm 25 mm 23 mm 20 mm
100 lbs/50 kg 45 60 75 100 110 120 130
70 lbs/35 kg 35 50 65 80 90 100 110

Art, I'm 92kgs and there is no way I would ride a 23c as low as 80psi on the front. I would be terrified of rolling the tyre. I've had this happen on a corner doing 65km/hr and have no wish to repeat the experience.
I seem to suffer from pinch flats at pressures under 100 but it might be where I ride. I have my tyres around the 110 mark depending on the type of tyre. We tried using GP3000 23c on the tandem and had to run them at 140-150 to stop them from feeling squidgy.

Cheers

Geoff

mikesbytes said:

I use to think that too, that skinner gave lower rolling resistance, until I read up on the topic. At 40kmh we have 80% wind resistence and 20% rolling resistence, so a narrower tyre wins out for faster riders. Tyre sizes and pressures are a hot topic.

BTW, the recommended pressures for Rubino's is 100psi minimum 125psi maximum.

The minimum inflation pressure of a tyre is that which does not allow the tube to pinch on rough roads and does not allow the tyre to roll off the rim with heavy cornering. 100psi minimum seems wrong unless the bead is hopelessly unable to engage the rim or the tyre is substantially lower diameter than other "23mm" tyres. Certainly, for Pro Race tyres, 100+ psi is uncomfortable on Sydney roads on my bike.
The relative length of the chain stays determines the balance of weighting of the wheels. On a short stay bike like mine, with an XL top tube length, I'm quite happy with a relatively low pressure front as I'm sure that that tyre takes only 1/4 - 1/3 my weight under normal riding, although clearly more with heavy braking or riding out of the saddle or riding downhill.

geoffs said:

Art, I'm 92kgs and there is no way I would ride a 23c as low as 80psi on the front. I would be terrified of rolling the tyre. I've had this happen on a corner doing 65km/hr and have no wish to repeat the experience.
I seem to suffer from pinch flats at pressures under 100 but it might be where I ride.

Geoff, point taken about tyre roll-off - if I was about to ride a twisting descent I'd probably want to take it up to 90-95, although, as I've posted, I don't think that my front wheel takes more than 30kg. I've had no trouble with roll-off, ever, and the tyre minimum is 76psi.
I've never pinched my front tube despite hitting quite a few "big" bumps. The Pro Race, however, is a larger volume tyre than the gp4000.

Albert 50 said:

Art, I've noticed your threads re spokes before & although you do not wish to use 25mm tyres, they may, given the extra height, take a little pressure off the spokes over the bumps🙂

I'll try 36xDB14/15 spokes on a deep rim before I go to the dark side!