## Gravel Tire Pressure

Especially for light weight issues concerning cyclocross / touring bikes & parts.

Moderator: Moderator Team

MikeD
Posts: 480
Joined: Thu Dec 11, 2014 9:55 pm
As I was riding my gravel bike on a bumpy gravel road the other day, and getting beat up because of the rough road, I realized I should have used much less tire pressure. I set my pressure using a spreadsheet that goes by 15 percent tire drop. This works great for pavement but not off road. Any recommendations here or a recommended calculator based on tire width and weight? Also, the ride was about 1/3 dirt and 2/3 pavement. Obviously, I wouldn't want to have underinflated tires on pavement either. Guess I need to carry a pressure gage too for these types of rides so I can let pressure out or pump up.

kervelo
Posts: 459
Joined: Wed Jan 21, 2009 6:58 am
Location: Finland
MikeD wrote:
Mon Apr 19, 2021 3:08 pm
... recommendations here or a recommended calculator based on tire width and weight?
SRAM calculator is good.
https://axs.sram.com/guides/tire/pressure

Singular
Posts: 229
Joined: Mon Jul 27, 2020 8:59 am
I really like the Silca pressure calculator; https://info.silca.cc/silca-professiona ... calculator

MikeD
Posts: 480
Joined: Thu Dec 11, 2014 9:55 pm
kervelo wrote:
MikeD wrote:
Mon Apr 19, 2021 3:08 pm
... recommendations here or a recommended calculator based on tire width and weight?
SRAM calculator is good.
https://axs.sram.com/guides/tire/pressure
That looks like a good calculator. Thanks.

Sent from my iPhone using Tapatalk Pro

pdlpsher1
Posts: 3150
Joined: Thu Jul 19, 2012 6:09 pm
Location: CO
I run 30psi/35psi F/R for 650Bx40 with 80% gravel. I ran the Sram calculator and it gave me 32psi/34psi F/R. That's pretty close. I generally like to run quite a bit lower pressure on the front since when I wash out on loose gravel it's always the front tire that goes first.

MikeD
Posts: 480
Joined: Thu Dec 11, 2014 9:55 pm
pdlpsher1 wrote:I run 30psi/35psi F/R for 650Bx40 with 80% gravel. I ran the Sram calculator and it gave me 32psi/34psi F/R. That's pretty close. I generally like to run quite a bit lower pressure on the front since when I wash out on loose gravel it's always the front tire that goes first.
The SRAM calculator must assume a front/rear weight distribution; probably 55/45. It would be nice to be able to plug in your own numbers for this, but that's a minor nit pick.

Also, it says to use the labeled tire width. Shouldn't that be the actual, measured width? As everyone knows, the labeled width can vary significantly from the actual width.

tritiltheend
Posts: 13
Joined: Sat Jun 02, 2012 2:42 am
I prefer the Silca calculator to the SRAM one, it gives more granular results and as someone else pointed out, the distinction between measured and labelled width is very important. But in my limited use of the SRAM one it gave fairly similar results. While it's possible to go too low, I think a lot of people err on the side of overly high pressure - old habits die hard. I use the "Category IV" setting for most of my gravel riding, which often involves easier MTB trails, and only go higher if I know that the gravel is going to be smooth and I'm riding a lot of pavement.

MikeD
Posts: 480
Joined: Thu Dec 11, 2014 9:55 pm
tritiltheend wrote:I prefer the Silca calculator to the SRAM one, it gives more granular results and as someone else pointed out, the distinction between measured and labelled width is very important. But in my limited use of the SRAM one it gave fairly similar results. While it's possible to go too low, I think a lot of people err on the side of overly high pressure - old habits die hard. I use the "Category IV" setting for most of my gravel riding, which often involves easier MTB trails, and only go higher if I know that the gravel is going to be smooth and I'm riding a lot of pavement.
The Silca one is nice. I like the selections for surface condition and weight distribution.

Marin
Posts: 3799
Joined: Wed Jan 22, 2014 11:48 am
Location: Vienna Austria
For road & gravel: Deflate the front tire until you get understeer when braking hard into turns, then add 0.1 bar. Rear tire pressure a little higher.

For mostly gravel on tubeless: Deflate until you get *slight* hits to the rim in the roughest sections. Brake a bit earlier for turns on asphalt.

You're NOT losing any speed running the tires soft on the road!

ms6073
Posts: 3497
Joined: Fri Jul 23, 2004 8:24 pm
Location: Houston, Texas
Marin wrote:
Wed Apr 21, 2021 12:47 pm
You're NOT losing any speed running the tires soft on the road!
Isn' that somewhat antithetical given that on the harder road surfaces, aren't under inflated tires going to have higher rolling resistance?

Now I am the last person to preach about being OCD about things like tire pressure, but back in my cross racing days, 'proper' tire pressure was derived from a process of sucessive trial and error rides while adding/remiving air until the appropriate level of performance was achiived. From this, multuple baselines were established for varying conditions as tire pressure for racing on a dry day on a long, mostly grass course could vary quite a bit from the lower pressures used to race on a highly technical mixed surface course on a cold, wet/muddy day.
- Michael

tanhalt
Posts: 258
Joined: Wed Dec 27, 2006 6:36 pm
Marin wrote:
Wed Apr 21, 2021 12:47 pm
You're NOT losing any speed running the tires soft on the road!
Well...actually, you are...but " 'Tis far better to err on the side of too low of pressure than too high"

Travelbytaco
Posts: 2
Joined: Tue Dec 22, 2020 1:34 pm
Just tried the Silca calculator and it's spot on to what I run; 40psi, f/r.