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AA7

What pressure should my tyres be?

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I'm guessing I'll get lots of different opinions on this. I was chatting to a friend yesterday and he told me that pumping my tyres up to about 110psi for a race is too high. Not exactly sure why I do 110psi, I guess I read it somewhere at some time. My weight is about 50-51kg, so enlighten me. 

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According to the Sram TyreWiz.

If you're 50kg, 10kg of bike/water, 700cx23 tyres you're looking at about 78F/80R

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110 was the default wisdom passed down to me when I first started riding.

I generally do for 100 nowadays, but I have double your non bike weight and a bit.

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26 minutes ago, Tyno said:

110 was the default wisdom passed down to me when I first started riding.

I generally do for 100 nowadays, but I have double your non bike weight and a bit.

I am the same. For me running on anything under about 95 feels like I am on flat tyres..... 

I always ride 100PSI -110PSI.

If I was to Use Slunnie's formula I would be slight higher than that as I am normally about 75KG. 

But there are so many different views these days on tyre widths and pressure and rolling resistance. These expert tests..... to me defy normal logic... but thats another story.

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I run about 90 psi. Just because it is comfortable. And am around 90kg plus bike.

I have run road tubeless down to 70. Psi but cornered like had a flat

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Depends on tyre width and road surface. Also the newer tubeless tyres run with significantly less pressure.

I'm 75kg.  On my roadie with 25mm clincher tyres I run about 95 psi.  My tri-bike has 23mm tubulars - 105 psi for Beach Rd races, 100 psi elsewhere like Geelong.  And I probably drop around 5 psi for wet conditions

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Yeah road surface is important. 

Lots of variables. There's a youtube video of TDF guys being asked what tyre pressure they ran and the range was 90 - 110, most (all?) on tubs I'm guessing. Track guys are running tubs on 160+. I messed around with tyre pressure when I first switched to tubs, not noticing much difference between 100 and 120. I did a sprint with tyres at 140 and noticed it had a negative impact. Generally I run them at 100 now. 

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Bit of rain near the roundabout & u-turns at Robina tomorrow, probably drop another 5 :)

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2 hours ago, IronmanFoz said:

I am the same. For me running on anything under about 95 feels like I am on flat tyres..... 

I always ride 100PSI -110PSI.

If I was to Use Slunnie's formula I would be slight higher than that as I am normally about 75KG. 

But there are so many different views these days on tyre widths and pressure and rolling resistance. These expert tests..... to me defy normal logic... but thats another story.

The Sram Tyrewiz has for 75kg rider, 10kg bike, 700cx23mm at 82F/85R

Like you though, I've always just run 100psi.

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I run about 80-85psi front and back but run 23mm front and 25mm rear. Think I read it somewhere on slowtwits that is better/ quicker for the tyre to conform around the small bumps in the road than to bounce over them. I’m a 70kg rider

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I’m approx 71kg and I run Continental 28cc clincher tyres (which actually measure 30cc) at 90psi rear 80psi front. I live in Bathurst so the roads are rougher and I could probably go less psi but it seems to be a sweet spot that I’m comfortable with.

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I must be very old school. at 75-77kg rider plus whatever for bike, for training tyres I have 700x23 and I run 100 front and rear. For race wheels, ZIPP 440 front and either a 440 or 950 disc rear I run Continental GP's, 19mm and at 150psi for both front and rear. 

I do hear talk of better rolling resistance at some lower pressures but that might be tyre dependent. I like the feel on the road at 150psi and lower pressures, say around 100psi. seem a bit flat. less responsive.

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13 minutes ago, Peter said:

Jezz.  I run 110psi.  In every condition.  

Me too.

I struggle with the logic that wider tyres and lower pressure are faster. Logically the harder the tyres the less tyre is touching the road which equals faster. 

Anyway....my experience tells me they are wrong.

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So now I'm even more confused. Think I'll just stick with what I've been doing, it goes ok.

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14 hours ago, dazmuzza said:

I run low, it's far more comfortable. 

pinch flats?

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1 hour ago, AA7 said:

So now I'm even more confused. Think I'll just stick with what I've been doing, it goes ok.

Tyre pressure needs to be quite low or very high for there to be a significant adverse affect on performance. The difference between 90 and 100 is negligible. I didn't notice much difference from 90 - 130 psi, past 140 I started seeing some performance degradation. So if you ride them at 90-, 95, 100 its not really going to matter a whole lot, especially when you consider differences in road surfaces.

Edited by zed

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19 hours ago, IronmanFoz said:

Me too.

I struggle with the logic that wider tyres and lower pressure are faster. Logically the harder the tyres the less tyre is touching the road which equals faster. 

Anyway....my experience tells me they are wrong.

It's not logic, it's science... 😉

I'll try and find the source doc, but anyway - there is a really good study that was comparing tyre pressure and subsequent performance with athlete's perception of speed/effort.  Turns out that higher PSI had athlete's reporting that they felt faster - but they were actually slower (or using more power for the same speed).   Interpretation was that the 'bouncing' of the rock-hard tyres over minor road imperfections 'feels fast', even tho its actually slowing you down.

Personally - I very rarely pump my tyres over 100.  I run 23 front/25 back, and will usually pump them to roughly 85/90psi (+/- 10psi).

 

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42 minutes ago, Abby said:

  Turns out that higher PSI had athlete's reporting that they felt faster - but they were actually slower (or using more power for the same speed).  

 

Which is exactly what I experienced, I kept on jacking up the psi as it felt fast until I did a race and my bike split was shit. 

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21 hours ago, IronmanFoz said:

Me too.

I struggle with the logic that wider tyres and lower pressure are faster. Logically the harder the tyres the less tyre is touching the road which equals faster. 

Anyway....my experience tells me they are wrong.

For a given pressure wIder tyres produce lower rolling resistance. Rolling resistance is caused mainly by deformation of the tyre sidewall.  You can think of this as how long the flat bit is where the tyre touches the road, not the how wide it is.  So, for a given area a wider tyre has less "length" and more width than a narrower one, hence lower resistance.

You can counter this by increasing the pressure which reduces the "length" also but causes other problems.

Don't overthink it however. Like all things in triathlon it really won't change things much, even though we wish with all our heart that a simple change will get us on the podium.

IMO you should run singles and pump them up with a track pump pre-race in the TA to 150 psi.  You will look awesome....

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16 minutes ago, BC_J400 said:

60 on my mountain e-bike and 120-130 on the racer.  No less 🙂

I assume the ebike is a super commuter and you're not off roading at 60 psi?

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6 hours ago, Abby said:

It's not logic, it's science... 😉

I'll try and find the source doc, but anyway - there is a really good study that was comparing tyre pressure and subsequent performance with athlete's perception of speed/effort.  Turns out that higher PSI had athlete's reporting that they felt faster - but they were actually slower (or using more power for the same speed).   Interpretation was that the 'bouncing' of the rock-hard tyres over minor road imperfections 'feels fast', even tho its actually slowing you down.

Personally - I very rarely pump my tyres over 100.  I run 23 front/25 back, and will usually pump them to roughly 85/90psi (+/- 10psi).

 

Yep, impedance is the term they use. Feeling every bump feels fast, but uses more energy to move the bike and rider. The rougher the surface, the lower the pressure should go within reason to reduce the impedance. The zippcast link I posted above explains it really well.

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19 minutes ago, BC_J400 said:

60 on my mountain e-bike and 120-130 on the racer.  No less 🙂

Wow my mountain bike I run at 20 psi.  Used to be 35-40 but was crashing.  Now 20 I’m killing it. 

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Lots of different theories on here. Like Pete, I run 110 psi on clinchers all the time. On my race wheels I run the singles at 120. Mountain bike 40. 

Some races have such shit road surface I've adjust pressures to prevent punctures. Places like Forster, Nowra, Warnambol and Yeppoon (especially Yeppoon) I'd run singles at 100. Didn't get any punctures the times I did that. Could have been luck or good management. 

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9 hours ago, zed said:

Which is exactly what I experienced, I kept on jacking up the psi as it felt fast until I did a race and my bike split was shit. 

How much could tyre pressure affect performance that you noticed it to the extent your split was shit? Are we talking 5mins on a 70.3 for example? 

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9 hours ago, zed said:

Which is exactly what I experienced, I kept on jacking up the psi as it felt fast until I did a race and my bike split was shit. 

How do you know it wasn't just a bad day on the bike, tired/fatigued etc, went too hard.

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59 minutes ago, IronmanFoz said:

How do you know it wasn't just a bad day on the bike, tired/fatigued etc, went too hard.

yeah it could have been. I felt fine, it was a sprint and I was fit, yet getting passed my everyman and his dog. Easy to blame tyre pressure, maybe it was the engine! 

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1 hour ago, more said:

How much could tyre pressure affect performance that you noticed it to the extent your split was shit? Are we talking 5mins on a 70.3 for example? 

it was just in a sprint. It would be interesting to see some kind of scientific data/experiment. Not sure if it was the tyres or me. Road surfaces were good.

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On ‎12‎/‎01‎/‎2020 at 7:48 PM, Slunnie said:

This may be interesting to some on the tyre pressure topic.

https://podcasts.apple.com/us/podcast/lets-talk-tire-pressure/id1462294309?i=1000456901735

 

I listened to it..... didn't give me a real lot though i did get the logic when the tyre widths are starting to move from 28's and up.

And they admitted on a perfect road surface the higher PSI the better. We know that we don't get perfect road's but not all are the type they seems to be talking about. In Sydney, you get a real mixture, but nothing too bad. 

So i reckon somewhere between what Peter and Bored @ is about right. 

90/95 on the front & 100 on the back - Bored@Work

Jezz.  I run 110psi.  In every condition. - Peter 

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Roads in Perth I would run 110. Busso you would run 120 and then drop to 90 (if you could) on the rough roads.

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That Zippcast was interesting but it was like listening to a stoner tell you about engineering :lol: 

I used to live by the motto, if the tyre has a recommended max pressure then that was what I pumped it to, but these days I ride 25’s at 90 psi. In the end if the speed differential really is negligible (which seems to be what we are saying here)  then why not err on the side of comfort and safety with lower pressures. 

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14 minutes ago, zed said:

Roads in Perth I would run 110. Busso you would run 120 and then drop to 90 (if you could) on the rough roads.

Have they fixed the roads up? 
 

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3 minutes ago, Bored@work said:

Have they fixed the roads up? 
 

nah, not out the back. But roads leading into Tuart forest are smoother than my arse.

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51 minutes ago, zed said:

nah, not out the back. But roads leading into Tuart forest are smoother than my arse.

What’s the % of good road v bad road?

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12 minutes ago, Bored@work said:

What’s the % of good road v bad road?

The 172km of that downhill section is still good apparently

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1 hour ago, Bored@work said:

What’s the % of good road v bad road?

on that 90km loop I reckon 30 great, 20 good, 10 average, 30 shit. Unless you're mark Robson and it would be 30 great.

Edited by zed

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