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Tire pressure vs Speed Question

Old 12-06-21, 11:40 AM
  #26  
SpedFast
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Originally Posted by AJW2W11E
Rain is worse than snow.
Yes it is!
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Old 12-07-21, 01:48 PM
  #27  
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but is wet snow worse than rain?
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Old 12-07-21, 02:07 PM
  #28  
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All the cool people run lower pressure in their tires cause some Science(tm) article on a website, that makes money selling bike things, told them so.

What? You don't want to be uncool and an anti-science and evidenced-based denier do you? Well have fun riding to your meetings at the Flat Earth Society on rock hard tires, you heathen.

To show your bona fides you'll need to take the manufacturer's recommended pressure and cut it in half. Make sure to tell everyone what pressure your tires were run at and how "soft" and "smooth" the ride was just like the marketing Science(tm) told you.

Do be careful with lowering your pressure and telling the world about it. There's this other gang out there...the High Pressure Gang...and if they find out you went below 110psi they'll say bad things about your Rapha Handle Bar Bag (which we all just adore!).

Either way; the wrong choice is yours.

Last edited by ChamoisDavisJr; 12-07-21 at 02:13 PM.
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Old 12-07-21, 02:25 PM
  #29  
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One thing not discussed here is the effect of wet pavement on speed. Over the years I've noticed that the bike feels faster when the roads are wet. The OP was riding in the rain.


As far as tire pressure and speed are concerned, it all depends on the tire as to the optimum pressure. Also. for a long ride comfort is important. Over inflated tires will transmit more vibrations and shocks to the rider which will tend to tire you out quicker than tires inflated to a lower, more comfortable pressure.
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Old 12-07-21, 04:24 PM
  #30  
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Try the tire pressure calculator at zipp.com. Real world testing has shown that it's not necessary to use 23mm tires at 110psi to get low rolling resistance. Zipp recommends 62/64 psi for my 28mm tubeless tires and 135 pound weight.

Also don't assume that your pressure gauge is accurate - many aren't.

Last edited by DaveSSS; 12-07-21 at 04:33 PM.
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Old 12-07-21, 07:48 PM
  #31  
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Originally Posted by AJW2W11E
...what 32 to 35 mm inner tube can be pumped up to 100 psi like a road bike?
None. A tube doesn't resist air pressure. That's the job of the tire. The tube keeps the inside of the tire airtight so that the tire can support the air pressure. And as others have written, as tire size goes up, ideal pressures go down. I have 35mm tires on my hybrid and I don't take it over 80 psi.
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Old 12-07-21, 08:16 PM
  #32  
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Originally Posted by cjenrick
note that if you use wood rims, you will be the coolest cyclist on the block.
Especially when they flameout coming down the mountain.
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Old 12-07-21, 10:58 PM
  #33  
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Originally Posted by ChamoisDavisJr
All the cool people run lower pressure in their tires cause some Science(tm) article on a website, that makes money selling bike things, told them so.

What? You don't want to be uncool and an anti-science and evidenced-based denier do you? Well have fun riding to your meetings at the Flat Earth Society on rock hard tires, you heathen.

To show your bona fides you'll need to take the manufacturer's recommended pressure and cut it in half. Make sure to tell everyone what pressure your tires were run at and how "soft" and "smooth" the ride was just like the marketing Science(tm) told you.

Do be careful with lowering your pressure and telling the world about it. There's this other gang out there...the High Pressure Gang...and if they find out you went below 110psi they'll say bad things about your Rapha Handle Bar Bag (which we all just adore!).

Either way; the wrong choice is yours.
Unless the website is selling air or pumps, I'm not sure what the marketing angle is?

So, consider a tire with infinite pressure. The "contact patch" is infinitely small (assuming the road is a plane surface). I guess we can conclude that energy loss due to tire flex is zero. But if the road is not a plane, then there are other considerations. I guess we also have to consider the effects of slip on the rear.

scott s.
.
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Old 12-08-21, 10:45 AM
  #34  
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Originally Posted by scott967
Unless the website is selling air or pumps, I'm not sure what the marketing angle is?
Pretty sure it was a ham-fisted attempt at humor.
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Old 12-08-21, 11:10 AM
  #35  
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Originally Posted by LarrySellerz
The recent articles/studies saying that wider tires at lower pressures are just as fast as thin tires at high pressure is Big Gravel trying to n+1 roadies. Follow the money.

OP I'm 250 lbs and run my 33 mm tires at 100+ psi. They say 65 psi on them but they dont break.

If I ride with you I'm keeping 1 1/2 bike lengths and wearing hearing protectors.
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Old 12-09-21, 03:35 PM
  #36  
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Originally Posted by DaveSSS
Try the tire pressure calculator at zipp.com. Real world testing has shown that it's not necessary to use 23mm tires at 110psi to get low rolling resistance. Zipp recommends 62/64 psi for my 28mm tubeless tires and 135 pound weight.

Also don't assume that your pressure gauge is accurate - many aren't.
Yeah thanks for the reminder. That calculator does pretty well.

t calculated 58/62 psi for my 175 lb self riding 32s on crushed stone and dirt trails, which is about what I do, though I run 58-60 psi rear and don’t go over 60.

I ride my 26er on the same bike trails, paths and roads and could probably be running lower pressure on them, like 30 psi instead of 35.

And yes, the built-in gauge on my floor pump is just a rough guide compared to the accuracy of my Meiser gauge. Been using those since the 70s.

Otto

Last edited by ofajen; 12-09-21 at 07:26 PM.
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Old 12-09-21, 06:33 PM
  #37  
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A smaller contact patch means less resistance. I started racing as a kid, and remember experimenting with different tire pressures to increase speed. On a smooth surface like a track, I would run 140psi, which was 30psi higher than the maximum recommended pressure, but I was a good deal lighter in those days. The narrower the tire, the higher the pressure you must run to prevent the tire from compressing on bumps and such. Nowadays wider tires are more fashionable, I find I get the best performance on my particular tires at 105psi. There are a lot of silly stories and videos about tires, sizes, pressure, and rolling resistance on the internet today, many or most of them are bunk. I used to sell bike tires, and took classes held by Pirelli on “science” of tire design, it was very informative.
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Old 12-09-21, 07:46 PM
  #38  
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This article summarizes a lot of the newer thinking on tire width and pressure. The first paragraph has a link to a good podcast on the topic. This stuff is no longer news.

https://cyclingtips.com/2017/05/what...re-pressure-2/

Otto
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Old 12-09-21, 07:47 PM
  #39  
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I've always believed higher pressures equals less rolling resistance and GCN has a good video proving it on utube. I don't ride at optimal pressure to reduce resistance because I like a slightly smoother ride.
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Old 12-09-21, 10:04 PM
  #40  
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Here is Tom Anhalt’s article from back in 2009 where he describes how higher pressure lowers rolling resistance but at some point ( depending on many factors) increases suspension losses in the rider to the point of increasing the overall resistance to forward motion, which is what actually matters.

https://www.slowtwitch.com/Tech/What...ube__1034.html

Otto
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Old 12-09-21, 10:44 PM
  #41  
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Originally Posted by SpedFast
I've always believed higher pressures equals less rolling resistance and GCN has a good video proving it on utube. I don't ride at optimal pressure to reduce resistance because I like a slightly smoother ride.
I believe that in the last few years GCN has come around to the thinking that lower pressures are faster for most road conditions even as high pressure has lower rolling resistance:


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Old 12-10-21, 12:00 AM
  #42  
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Originally Posted by cxwrench
Stop it Larry.
Dude you should really look into the UCI they do some sketchy stuff. Spinergy rev x wheels and other one piece wheels were banned from mass start racing in conjunction with a French wheelmaker competitor, and descending on the top tube (not dangerous!) was banned to sell roadies dropper posts.
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Old 12-10-21, 12:01 AM
  #43  
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Originally Posted by billridesbikes
I believe that in the last few years GCN has come around to the thinking that lower pressures are faster for most road conditions even as high pressure has lower rolling resistance:

https://youtu.be/E3C5RzQrTvw
Propoganda, they are perverting your sport
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Old 12-10-21, 03:28 AM
  #44  
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I run a Giant Toughroad on 44mm WTB Byways, running 40psi front and 48psi rear (corrected from 50psi front, 60psi rear, used on 32mm tires!)
The bike it fast, perhaps faster than my drop bar bike when I use the aero bars on the Toughroad.
A problem I have had in the past is when you run really high pressures, theres no give, and you start breaking things like spokes...

Heres my setup!

Touring bike test setup front

Last edited by SquishyBiker; 12-11-21 at 02:41 PM. Reason: Wrong tire pressures!
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Old 12-10-21, 08:11 AM
  #45  
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Originally Posted by LarrySellerz
Dude you should really look into the UCI they do some sketchy stuff. Spinergy rev x wheels and other one piece wheels were banned from mass start racing in conjunction with a French wheelmaker competitor, and descending on the top tube (not dangerous!) was banned to sell roadies dropper posts.
Stop it, Larry.
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Old 12-10-21, 11:57 AM
  #46  
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Originally Posted by SquishyBiker
I run a Giant Toughroad on 44mm WTB Byways, running 50psi front and 60psi rear.
The bike it fast, perhaps faster than my drop bar bike when I use the aero bars on the Toughroad.
A problem I have had in the past is when you run really high pressures, theres no give, and you start breaking things like spokes...

Heres my setup!

Touring bike test setup front
And butts! I find with higher pressures also that there is a loss of cornering ability at high speeds (loss of traction) and God forbid you hit a patch of loose gravel in that corner (been there, done that). Softer tires do grip the road better. In my opinion.
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Old 12-10-21, 11:49 PM
  #47  
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Originally Posted by SquishyBiker
I run a Giant Toughroad on 44mm WTB Byways, running 50psi front and 60psi rear.
The bike it fast, perhaps faster than my drop bar bike when I use the aero bars on the Toughroad.
A problem I have had in the past is when you run really high pressures, theres no give, and you start breaking things like spokes...

Heres my setup!

Touring bike test setup front
Thats the same bike I have. I love it. Thanks for the warning. Another thing I notice is if I am pedaling up a really steep incline slowly , the bike pulls sharply to your dominant arm.
I just got some new Kenda Kwest Hi pressure tires, rated at 100 psi. Dont know what to do now.
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Old 12-11-21, 10:37 AM
  #48  
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Originally Posted by SquishyBiker
I run a Giant Toughroad on 44mm WTB Byways, running 50psi front and 60psi rear.
The bike it fast, perhaps faster than my drop bar bike when I use the aero bars on the Toughroad.
A problem I have had in the past is when you run really high pressures, theres no give, and you start breaking things like spokes...

Heres my setup!

Touring bike test setup front
nice setup! running 50 & 60 on those 44s is really a quite 'solid' (prolly would be way 'hard' for me) pressure...
i'm considering the 34s for my 'Multipurpose' Roubaix conversion...
ZIPP calculator is telling me , at my weight, to use 45ish PSI for the 34s - must be way lower for a 44...
might be worth the experimenting...
Ride On
Yuri
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Old 12-11-21, 02:40 PM
  #49  
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Originally Posted by cyclezen
nice setup! running 50 & 60 on those 44s is really a quite 'solid' (prolly would be way 'hard' for me) pressure...
i'm considering the 34s for my 'Multipurpose' Roubaix conversion...
ZIPP calculator is telling me , at my weight, to use 45ish PSI for the 34s - must be way lower for a 44...
might be worth the experimenting...
Ride On
Yuri
Right you are - I got my pressures mixed up!

I typically run the following pressures, based on me at 110kg/243lb:
32mm road: 50f, 60r
44mm road: 40f 48r
44mm gravel: 35f 42r

You might see a pattern here - I've settled on starting with a front pressure, and adding 20% to set the rear pressure - it works for me for just about everything.

I created a sidewall tension spreadsheet with a guide from GCN to help give me a starting point, then I tweek from there:
https://docs.google.com/spreadsheets...it?usp=sharing
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Old 12-11-21, 05:38 PM
  #50  
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Originally Posted by AJW2W11E
I've been riding for two years. I have a Giant Toughroad, which is not a fast bike. I am not that fast either.
My tire pressure was getting low and today I put some air in. Before, you could squeeze them and they were hard as maybe a beachball, 60 psi, but today I had them slightly less than rock hard, maybe 80 psi.
When I went out, it was raining like hell and windy and cold and starting to freeze . My feet were soaked then feeling funny and I got concerned so I jacked up my speedto get home fast.
With the higher pressure, I noticed I was moving pretty briskly and then I noticed was able to use the big ring and smallest cog the whole 30 miles and cut 20 minutes of my time.
That being said, what 32 to 35 mm inner tube can be pumped up to 100 psi like a road bike?
Next, at what psi does this effect wear off. I'm guessing 120 is the limit? Because after that, rock hard is rock hard?
Sure had some fun today...or was it my imagination? BTW my lower legs and feet were purple and my hands were too.
Above about 80 psi for a 25 mm tire and considerably less than that for a 32 mm tire, more pressure has no significant improvement and on rough roads can actually slow you down. You were 20 minutes faster because you rode harder, not because you pumped your tires up. I don't know your gearing but if you were able to spin a 50/12 you were going over 30 mph. Were you, or were you just grinding along and pedaling squares?
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