sierra_skier

Hi everyone,

Fairly new to gravel biking (came from MTB a couple months ago) and I live in the Bay Area where I usually have to go 15-20 miles on road to get to the trails. Because of this, I’ve been running fairly high tire pressure to make the road section faster, since it does end up being at least half if not more of my mileage. But I did a couple rides with lower tire pressure and the difference while riding trails is huge. What do you all do in this situation? Keep pressure high for the road, drop it when you get to trails, and then pump back up for the road back home? Or deal with lower tire pressure on the way home, or just the whole time?

Also, wouldn’t mind help with good tire pressure starting points:
165lb with clothes, 18lb bike, about 5lb other stuff on the bike. 2.1” 650b tires

Thanks!

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Angstrom
It depends a bit on how smooth your pavement is.  If it's crappy pavement, using the "trail" pressure might be the simplest approach.  If the pavement is smooth, changing pressures might be worth it.
Where I live, the pavement often isn't much smoother than the dirt roads, so I use what I  like on dirt.  I'm still experimenting. 155lbs, 38mm 700s, pressures in the mid-high 30s.

A couple of articles you might like -- both suggest that it's better to go low than to go high.

https://blog.silca.cc/part-4b-rolling-resistance-and-impedance

https://www.velonews.com/news/gravel/optimal-tire-pressure-gravel/

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sierra_skier
Thanks! Generally when I'm on pavement it's pretty smooth, but based on those articles maybe I wouldn't be spending that much extra energy running a lower tire pressure while on pavement than I think it will- probably mostly a mental thing that I feel so much slower with these big tires and lower pressure.

The pressure/tire combo you mentioned is similar to what I run on my non-gravel wheelset (mostly road with bits of easy off road)- 38mm 700c 40psi. So sounds like that's maybe in the right ballpark.
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chas
Thanks! Generally when I'm on pavement it's pretty smooth, but based on those articles maybe I wouldn't be spending that much extra energy running a lower tire pressure while on pavement than I think it will- probably mostly a mental thing that I feel so much slower with these big tires and lower pressure.
.


Yeah, lower tire pressure on the road doesn't hurt as much as we once thought, but higher pressure off road certainly hurts more than we thought.  I used to think 120psi road, and 60psi on a mountain bike tire was fast.  Well, it felt fast!  Felt sketchy is more like it.  

I'm about your size.  When I'm running 2.1" tires I'm running low 20's in the front, maybe 25 rear.    I'm really looking at how much the tire deforms when it is weighted, &how well it corners.  I like to ride through a puddle and see how large my contact patch is.  If I'm on a 20mm contact patch on a 50mm tire, its got too much air in it.  While that might be OK on the road, its not good for mixed terrain.  
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sierra_skier
chas wrote:

I like to ride through a puddle and see how large my contact patch is.  If I'm on a 20mm contact patch on a 50mm tire, its got too much air in it.  While that might be OK on the road, its not good for mixed terrain.  


Nice, that's a good way to test it out. Thanks a lot for the input.
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ccand51997
I've tested tire pressure a number of times and I was amazed each time that it did not make any difference.  Twice, I tested up a hill at approximately 50psi, 25ish and then probably around 8-10 psi.  The first felt really hard for a 2.2 tire, the last soft, bouncy and unstable.  None of the times varied for the same wattage.  Now, some smart folks have tested on a drum and found rolling resistance differences for variations in pressure, but they are quite small.  As such, I run my tires at 20 psi (47mm Byway front, 50-57mm G-One Speed or Conti Raceking rear) and probably do about 50/50 road/dirt.  Most of my roads around here are not very smooth so I love riding low pressure. 
Quote 1 0
epzamora
I have my 650b x 2.1 tires aired for dirt (18/20?) and keep it that way for the pavement too. I run tubeless. Often 50/50 pavement/dirt on a 25 mile ride. I'm 6'-0" at around 206 lbs.

eric/fresno, ca.
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sierra_skier
Tried 20/25 this morning on a ride that was 80% road/fire road 20% singletrack including some rocky/rooty sections, the lower pressure was way better on the singletrack not so noticeable on the road. Thinking I'll find a short section of trail and do some reps at different pressures to see what feels best.
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flowbie
I'm 200lbs and ride pretty much 30psi front and 32psi rear all the time with Gravelking SK's 650bx1.9's. On my enduro bike I'm running 20psi front and 21psi rear with Maxxis DHF 2.6 front and DHR 2.4 rear. I'm in the Pacific Northwest where it's often wet so I like my traction at the expense of rolling resistance. 
Quote 0 0
Zurichman
You didn't say if you were running tubes or tubeless big difference. I am running tubeless. Everybody IMHO has to find their sweet spot or at least what their comfort level is.

At my end running tubeless and  200 lbs. I run 40 rear 35 front for gravel. If it's more roadie I run 45 rear and 40 front. Good luck

Zman
If it was easy it wouldn't be a memory. You just hope you don't have all your memories in the same ride. been there dun that Zman
Quote 0 0
flowbie
Zurichman wrote:
You didn't say if you were running tubes or tubeless big difference. I am running tubeless. Everybody IMHO has to find their sweet spot or at least what their comfort level is.

At my end running tubeless and  200 lbs. I run 40 rear 35 front for gravel. If it's more roadie I run 45 rear and 40 front. Good luck

Zman


People run something other than tubeless??
Quote 0 0
widerisfaster
Silca Tyre pressure calculator recommends 24psi front, 25psi rear for your system weight and tyre width: 
https://info.silca.cc/silca-professional-pressure-calculator
Quote 1 0
Zurichman
flowbie wrote:


People run something other than tubeless??


Yeah some people still run tubes while riding gravel or on a gravel bike.

Zman
If it was easy it wouldn't be a memory. You just hope you don't have all your memories in the same ride. been there dun that Zman
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morenow
I run 35 front and 38 at the back. 
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smoothmoose
epzamora wrote:
I have my 650b x 2.1 tires aired for dirt (18/20?) and keep it that way for the pavement too. I run tubeless. Often 50/50 pavement/dirt on a 25 mile ride. I'm 6'-0" at around 206 lbs.

eric/fresno, ca.


Damn - that's low.

I'm in the bay area.  On my 27.5 x 2.1" I ride 22/25psi based on 150# riding weight.  Maybe I should try even lower - but find that to be good for both road and singletrack.  My 650b/27.5 wheels see mostly singletrack/fireroads...maybe 20-30% road.
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sierra_skier
Zurichman wrote:
You didn't say if you were running tubes or tubeless big difference.
Zman


I am running tubeless- but does that make a difference for how a specific pressure feels? Didn't know that, I just thought that tubeless means you can run lower pressures without worrying about pinch flats
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chas


I am running tubeless- but does that make a difference for how a specific pressure feels? Didn't know that, I just thought that tubeless means you can run lower pressures without worrying about pinch flats


I can't friggen feel the difference (other than changing the pressure).
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Turbogrover
I've run 40 psi on the road using 700 x 42 tires and it didn't slow me down one bit, but lowering it down to 32 caused a lot of bobbing while doing some high cadence pedaling.
I'm 5'8" 176lbs in full gear.
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Turbogrover


I am running tubeless- but does that make a difference for how a specific pressure feels? Didn't know that, I just thought that tubeless means you can run lower pressures without worrying about pinch flats


It can make a difference if you're using pretty low tire pressures. The tube will squirm more with less psi in it. It's a noticeable and irritating thing for me to run tubes and low pressures. You REALLY notice it on fatbike tires.
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