Fly2High

I ran across an article in Bicycle Quarterly about Tire Pressure Drop (https://www.bikequarterly.com/images/TireDrop.pdf)

They recommend optimizing the tire pressure base on your weight.

They even ask you to measure the weight differential between front and back into the equation.


How many ride this way or do you just max out the tires and go?

Any pros/cons to the BQ recommendation?

Would you also do this for a Hybrid? For a Mountain bike?

Thanks

Frank

playback2004

I used to inflate to 115 psi on 26mm tires. I have gone to 100 on 23mm tires. I also put on a ton of weight recently as I had not been riding. I weigh 220. I am back up to 110 on 23mm tires.

I experiment but I don't recommend dropping pressure below 95 without doing a lot of riding at that pressure.

gsa103

You definitely want to optimize based on weight. Don't bother measuring F/R balance, you'll get the wrong answer. The front normally doesn't have much weight, but under hard braking or cornering, it will suddenly get most of the weight.

BQ recommendations are a hair on the low side, and you want more like a 45/55 distribution to account for braking loads.

The best approach is to incrementally lower the pressure until the bike starts feeling sluggish, poor handling or pinch flatting, then add a little more pressure.

K100Fran 

Here's what Sheldon said...
Bicycle Tires and Tubes

Igualmente

I am on 28mm wide (nominal) tires that measure 26.5 to 27mm. Based on my weight, I set the rear tire at 85psi. I could and have set the front tire at 60 or 65 psi based on actual weight distribution, but it has a minimum rating of 70psi, so that is what I use.

rms13

my 700x23 are rated at 120. I generally inflate to 120 in rear and 110 in front and it works for me

biciklanto

Several years back, @Psimet2001 posted his formula for tire determining ideal tire pressures:

https://www.bikeforums.net/road-cycli...s-tip-day.html

I've found it pretty good, and because I haven't had a pinch flat in well over a decade, I'll even drop my pressure another 10 PSI in the rain.

JerrySTL

I'm around 215 lbs and ride 700x25s on my road bike. I put around 100 psi on them and have never had a pinch flat. I have had pinch flats on 700x23s at 120 psi.

79pmooney

I run front tires 3-5 psi lower than the rear (unless I am using loaded LowRiders in which case I have equal pressures). Pressure depends on tire size, tire make and model and the riding I'll be doing. I've stopped using 23s almost entirely but run them at 102 to 112. (I weigh 150.) 25s at 90-105. 28a at 75 - 95. 32s at 60-85. Lower off road, lower in the wet. Much lower on snow and ice.

Bouncing form too hard tires gets old (especially on chip seal and bad pavement. Pinch flats also get old. If I cannot find a good place between, I go to a bigger tire.

For me, life's too short and there is too much road to be explored to mess around with bikes that cannot handle at least 25c tires. And since I live in Oregon, that means 25c under fenders.

Edit: I've never pumped tires to the rated max. Never even considered it.

Ben

ThermionicScott 

+1. I'm not big on their 40/60 and 35/65 figures, even if they are "correct" for a static upright riding position. 45/55 works nicely to soften things up for your hands and keep enough pressure in the rear tire for bumps, though. Haven't gotten a pinch flat yet with the BQ chart and this weight distribution.


BTW, I'm pretty sure that Psimet's formulas are based off the BQ chart, just as this handy calculator is: Bicycle tire pressure calculator

K100Fran 

Thanks for the link to that thread. Good reading.

Lazyass

https://www.crw.org/safety/12safetyPg...v-pressure.php

EnsitMike

No idea what it SHOULD be, but I ride between 80 and 90PSI.

I tried 110 once and my tires were squirrelly. Overly responsive to the road and my movements. While lower on the other hand feels a bit sluggish.

Doge

I think he is overthinking it. It is nice to define drop but many riders use different pressure when they are near the same weight, on the same road and on the same tire. Tour de France teams keep pressure a secret to using very different pressures than other teams - for the same race. I also believe drop may be different based on tire - casing and certainly the rate of flex due to wheel rotation / durometer of the case material (hysteresis). Or - I don't give a lot of credit, although hard to do, to a static test.

Typically the rear is given a bit more. A 105/95 is common. A bigger tire is given less. So 100/100 when front is 23, rear is 25 is common.

Posters have dropped F bmbs on other forums over pressure. Several things matter.
Of course your weight.
The type of riding.
The type of road and conditions (wet, dirty etc.)
The type of tire.
What feel - comfort or responsive balance do you want
And other factors like risk of snake bites, wear, frame fit maintenance

From a rolling perspective only, you want the tire with as much pressure without causing a bounce (over little bumps in the road etc. If the tire is over-inflated and bounced it increases rolling resistance - think washboard at the side of highways.

A higher pressure tire is more responsive to an acceleration.

Lower pressure means more casing flex. That is mostly were the energy is lost. Better tires, lose less energy in the casing. They are often also less durable. A nice strong thick casing is likely also absorbing more energy when it flexes. For this reason a stiff tire - from a rolling resistance perspective needs more pressure than a supple tire.

You never want the pressure so low it will bottom out.
You never want pressure so low it will washout in a turn.
If you see folds in the casing the pressure is too low.

calyco

I am light at 140lbs and do 100PSI for 2 days on 700x23, never had problem yet

RoadTire 

The easy way to determine tire pressure is go with the opinions here on BF fitting your personality. Change pressure based on current BF tire pressure trends.

Doge

I don't like most lab tests as it is just super hard to test all the force directions and movement. I mentioned hysteresis in my post above. The resistance to deformation depends a lot on tire material. I found some stuff on auto tires just searching "hysteresis for tires". It somewhat applies.

When rolling (vs a static drop test) the material matters. Lower modulus materials bend better / absorb less of your riding energy.



This is hard to see but a graph that shows the energy loss based on the lag in deformation from a force.



I like this one. It shows more pressure only means lower resistance on roads.

xscottypx

i weight 140, ride 25's, usually inflate to 95 or 100 depending on temp. once warmer i may go 95F, 90R.