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Gravel Tire Pressure on Pavement? (40+mm tires)

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Cyclocross and Gravelbiking (Recreational) This has to be the most physically intense sport ever invented. It's high speed bicycle racing on a short off road course or riding the off pavement rides on gravel like : "Unbound Gravel". We also have a dedicated Racing forum for the Cyclocross Hard Core Racers.

Gravel Tire Pressure on Pavement? (40+mm tires)

Old 11-16-21, 08:53 AM
  #26  
franswa
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Sure, a wider tire will still have cushion for paved riding but for me personally, I prefer even lower pressure for even more comfort on out terrible chip seal roads. I am not bothered by any rolling resistance penalties that may come with this decision. I suppose I have a preference for maximum comfort over speed. It's good to exercise preference and that we have this ability to.
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Old 11-16-21, 02:15 PM
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Tire Pressure

Originally Posted by chas58
This is the original 15% tire drop chart. Still valid today. I guess you can interpolate a little for 40mm. This is wheel load (not rider weight). This was mind blowing when it was originally published, but all these years later, it is still pretty applicable.
I thought I'd used this as a reference before, but perhaps not. I run 700x32 at around 45-50 pounds on pavement, 700x30 50psi, 700x28 55-60, and 700x 25 at 60-65. My 700x42 RH tires on gravel are typically 30-34 pounds. I rarely put them above that for pavement...maybe I should try, lol, but seldom ride a pavement only ride on that bike anymore. I weight in the 150 range.
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Old 11-16-21, 02:59 PM
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Originally Posted by Craptacular8
I thought I'd used this as a reference
that's in the ball park for me
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Old 11-17-21, 08:55 AM
  #29  
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Originally Posted by mstateglfr
I just ran the silca tire pressure calculator.

It suggests 41rear 40front for my total weight on 43mm tires.
I run 45rear and 40front when on gravel/mixed surface, as mentioned earlier.
So pretty darn close.


But for pavement only? I am pretty surprised to see some of the low numbers mentioned in this thread since it's about gravel tire pressure for pavement. There is just no downside to bumping the pressure up a bit- a wider tire will still have plenty of cushion to deform over road imperfections and it'll roll faster than if it's at a low pressure.
I am not suggesting a 43mm tire be pumped to 90psi, to be clear.
Same here. The smoother the road the higher the pressure I use.
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Old 11-18-21, 11:54 AM
  #30  
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I'm 155# and running 42 mm Teravail Cannonballs on my gravel bike. The other day, I was riding on pavement but it was icy and I wanted the tires on the soft, grippy side, so I ran at 38 back/35 front, and that was good. Yesterday, dry roads and riding with a group where the others were on road bikes, so I wanted fast. I ran 46 back/42 front. That worked for fast, but also the road buzz was considerable. Based solely on comfort, 46/42 was too much.

That Silca calculator seems about right. It suggests about 42/39 for "fast group ride".
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Old 11-18-21, 12:40 PM
  #31  
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Also, it may be that the Silca calculator reproduces what some of you find is exactly right for your rig, no such calculator is going to be perfect. Tires, rims, road surfaces, and riders all introduce objective and subjective factors.

At times, what I wish I could calculate is the "plausible pinch flat" value. That would be the calculator that says, for a given setup and speed (say 20 mph), what's the minimum pressure to avoid one?=
(No smug comments about pinch flats and tubeless please. That's been done already.)
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Old 11-18-21, 12:43 PM
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That Silca calculator is very impressive, it comes up with numbers for me that are very close to what I have slowly evolved to with many experiments. It is the only calculator I have seen with so many road surface choices, I was winging that part.

I would say just punch in your numbers there, pump up, and go.
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Old 11-18-21, 02:49 PM
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Man, that Silca calculator seems way off for me. The front pressure seems too high and the rear seems too low. It recommended 44F/46R for 100% road on 40mm tires, but for that I'm at ~40F/60R. I'll drop to 35F/50R if I'm on mostly gravel, and I'll adjust the pressures somewhere in between if I'm mixing it up.
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Old 11-18-21, 04:16 PM
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Originally Posted by Phatman
Man, that Silca calculator seems way off for me. The front pressure seems too high and the rear seems too low. It recommended 44F/46R for 100% road on 40mm tires, but for that I'm at ~40F/60R. I'll drop to 35F/50R if I'm on mostly gravel, and I'll adjust the pressures somewhere in between if I'm mixing it up.
I don't know what the absolute values should be, but 40/60 seems like a really large F/R difference. Do you have an unusual weight load (such as loaded rear panniers)?
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Old 11-18-21, 04:55 PM
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Originally Posted by DarKris
I just wanted to get an idea of what you all run when it comes to tire pressure with larger gravel tires in the 40-50+mm size for primarily pavement. I’ve been testing tire pressures with the Fleecer Ridge tires which are 55mm but roll nice on pavement. I’ve gone as low as 25-30psi and up to 40-45psi which is high but I’m also ~250lbs. Honestly I didn’t think I felt that much of a difference, but I think the bigger test would be doing longer rides than my short 15 min. test rides 😅

Still, I was curious to see what others ran, and the reasoning behind why you settled with that tire pressure.
Something I didn't fully grasp until quite recently is that Rene Herse tires actually need a bit higher pressure than less supple tires of the same dimensions, due to the fact that they are completely supported by air rather than sidewall rigidity. Having said that, you can get away with running them low without taking a big hit in terms of rolling resistance. If you are running the air pressure too low, you will feel them squirm or even collapse a bit, and you get a telltale crosshatch marking on the sidewalls, which means the threads are getting stressed. So 40-45 psi is not that unreasonable. If you put in too much air, they will be a bit like basketballs.
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Old 11-18-21, 09:16 PM
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Originally Posted by MinnMan
I don't know what the absolute values should be, but 40/60 seems like a really large F/R difference. Do you have an unusual weight load (such as loaded rear panniers)?
All of the tire charts/apps are not for much weight change between front and rear. But, experiments show the weight distribution is in fact more like 40/60. Here is some science to back up the 40/60: https://www.vernier.com/vernier-idea...-on-a-bicycle/.

Why do the charts all seemingly advocate for less % drop on the front tire? There is probably an explanation but I never got a clear one. One reason I heard is when standing your weight is more forward so it is not good to make the pressures too different. I don't really buy that, and I put a slightly bigger difference front vs rear than the charts say to.. a ~5 psi front vs rear difference for gravel tires. The Silca chart is for a 47/53 weight distribution on gravel, and gives only 2psi pressure difference for me.

Last edited by scottfsmith; 11-18-21 at 09:20 PM.
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Old 11-18-21, 11:13 PM
  #37  
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Originally Posted by scottfsmith
Why do the charts all seemingly advocate for less % drop on the front tire? There is probably an explanation but I never got a clear one. One reason I heard is when standing your weight is more forward so it is not good to make the pressures too different.
I certainly find a difference in how I setup my tire pressures relative to how I use the bike.
For riding where I'm typically seated for most of the ride, ie road and gravel, I'm typically inflating the rear tire 20% more than the front, primarily for hand comfort.
For riding where I'm typically standing for most of the ride, ie mtb, I'm typically inflating the rear to 10% more than the front, as the bike feels more stable in the turns.
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Old 11-19-21, 12:41 AM
  #38  
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Originally Posted by Phatman
Man, that Silca calculator seems way off for me. The front pressure seems too high and the rear seems too low. It recommended 44F/46R for 100% road on 40mm tires, but for that I'm at ~40F/60R. I'll drop to 35F/50R if I'm on mostly gravel, and I'll adjust the pressures somewhere in between if I'm mixing it up.
As already stated, that is a significant difference R to F. If you've been riding this way for a while, it might feel "normal" because you are adjusted to it. Have you considered giving the slice pressures a chance, and seeing how they feel/ride? It's just air and a 2 minutes of your time to adjust the pressures. Or, look up "15% drop" and find a chart.
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Old 11-19-21, 09:40 AM
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Originally Posted by Badger6
As already stated, that is a significant difference R to F. If you've been riding this way for a while, it might feel "normal" because you are adjusted to it. Have you considered giving the slice pressures a chance, and seeing how they feel/ride? It's just air and a 2 minutes of your time to adjust the pressures. Or, look up "15% drop" and find a chart.
Yep, no extra load being carried on the back tire other than my giant guads.

I've tried dropping the rear, but below 50 or so it feels squishy and bouncy when standing to climb. My method of establishing tire pressures is basically to drop them until they feel squishy, then raise them back up a smidge until they stop feeling sloppy. For some reason, there's less of an issue with the front wheel being sloppy at lower pressures than the rear.
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Old 11-19-21, 03:53 PM
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Originally Posted by Craptacular8
I thought I'd used this as a reference before, but perhaps not. I run 700x32 at around 45-50 pounds on pavement, 700x30 50psi, 700x28 55-60, and 700x 25 at 60-65. My 700x42 RH tires on gravel are typically 30-34 pounds. I rarely put them above that for pavement...maybe I should try, lol, but seldom ride a pavement only ride on that bike anymore. I weight in the 150 range.
I just read an article on one of the pro teams that did the ParisRobaix.
They used 50F/65R with 30mm tires (for what is it worth)


Originally Posted by Phatman
Man, that Silca calculator seems way off for me. The front pressure seems too high and the rear seems too low. It recommended 44F/46R for 100% road on 40mm tires, but for that I'm at ~40F/60R. I'll drop to 35F/50R if I'm on mostly gravel, and I'll adjust the pressures somewhere in between if I'm mixing it up.
40/60 makes sense as the weight distribution is typically 40/60
I wonder if most people realize this?

often, when I ride through a damp spot (or anything that leaves a mark on the tire), I make sure the damp spot on my tire is the same width on the front tire as it is the back tire. Realistically, the front tire needs a LOT less pressure than the rear to get the same tire drop (or width of the tread in contact with the pavement).

your numbers look right on.
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Old 12-01-21, 05:41 AM
  #41  
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So first time hearing about the Silca calculator so I plugged my weight & tires in: at 260 loaded weight the 42mm 700c tires I can run 41/44 F/R and slightly less for rougher roads or slightly higher for smoother roads. For 55mm tires I can do 25/27. That…… is honestly close to what I was noticing when I would hop on my bikes w/o checking pressure. Obviously the 42mm UD tires were way more sensitive to pressure changes, but I was riding the 55mm RH and not immediately realizing how low the pressures were. I guess when you’re so used to running high pressures due to weight and running tubes it feels different when you can finally dial down to lower pressures, but I digress.
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Old 12-07-21, 08:01 PM
  #42  
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I’m 143lbs and I run 28/26 road/mix and 25/22 gravel on Donnelly strada uhs wc tires. My average speed on the road drops at higher pressure. I also run 70/65 on my 25mm tubed tires on my road bike, higher pressure than this is slower and more painful for me. Though I rarely ride the road bike anymore, even on all road rides, the gravel bike just feels better.
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