cyclehealth

How low can I go regarding the tire pressure? I am building up a Trek Elance 400 and have fitted it with ROL Volance wheels and 28 mm x 700c Continental Gran Prix 4 Season tires. I will be riding mostly roads with good pavement but also the occasional packed stone/gravel rail trail. I am hoping for somewhat of a cushy ride. At least what the 28 mm tires will allow. I weigh about 140 pounds suited up for a summer day of riding. Thanks in advance!

mpetry912 

depends on how many pinch flats you want to fix

based on the information provided

I'd say 60 psi minimum but what do I know ?

/markp

maddog34

you know that with that width tire, and the rider's weight, 60 lbs. is a good suggested minimum pressure.
Me too.... except, personally, i'd run about 75lbs.to carry my larger bulk... or 90 lbs. because i like to fly.

shelbyfv

SILCA chart

Iride01 

If you flat often and it's not actual punctures from something going through the tread, the rim shows signs of damage on the edges or the wheels feel like their slipping side to side or wobbly while you ride, especially when cornering, then you might be at too low a pressure. If the tire comes off the rim then it's very likely you have too little pressure.

So figure it out from trying.

cyclehealth

Thank you for the link. The chart recommends right around the 70 pound range depending on a few variables offered by the chart. It I read the disclaimer correctly the chart calculates tire pressure for the fastest ride. I will start at 70 PSI and go from there.
Thanks everyone!

mpetry912 

it's easy to throw a number but there are many variables.

Ideally the tire casing should be only minimally bulged when you are sitting on bike

and (Important) never, ever should the tire casing contact the rim on the worst pot hole of the ride

you should always have enough tire flotation to take you over the worst bump you're likely to encounter

the "apps" cannot possibly tell you this. it is up to you to empirically converge on your best tire pressure

larger or heavy riders run + 5 - 10 psi more on the back.

/markp

Andrew R Stewart 

One classic indication of too little air pressure (without a pinch flat having to happen) is the tire tends to creep around the rim and the poor valve caught in the rim hole can't travel with the tire and begins to get cocked/crooked. Andy

79pmooney

Another very real factor is the rider. There are riders who are murder on rims and riders of the same weight who can guide their wheels through "minefields" keeping both tires and rims intact. Ride in groups and I promise you, you will see both. Their minimum pressures for incident-free rides will be quite different.

I've used a 5-6 psi difference front and rear forever. I don't go less in front because when I am braking hard to stay off the suddenly braking car, I really don't want to bottom my front rim on that pothole I couldn't see coming (that darn car). Riding in groups - same thing can happen.

For me at 155 pounds and 28c tires, 70 psi is marginal. I'm much happier at around 90. I may do 70 in the wet or lower if below freezing because I really don't like crashing but am quite aware I might be sacrificing my rims.

Edit: Sorry, my "answer" isn't really to this post. I cannot just post to the thread in general because of the current BF software issues for Firefox users. Just graduated 3rd grade in the school of Firefox-BF workarounds. I can now multiply 2 times 3 and get 6! Wahoo!

LV2TNDM

You can't really set up a road bike with 28C tires for a "cushy" ride. That's why gravel bikes now afford much more space for far wider tires. A "cushy" ride will be achieved through riding a 44C tubeless tire! Well, let me correct my statement.... A "cushy" ride COULD be achieved with a 28C tire at proper tire pressure through appropriate frame geometry and spec design, but it would merely be "more comfortable" than actually "cushy."

If you're riding traditional inner tubes, then you're in for a very "non-cushy" ride. As already mentioned, you need to use enough pressure to avoid pinch flats, or worse, rim damage. Hit that deep unseen pothole and you're replacing both wheels because of pressure set too low (in addition to fixing two flats and maybe replacing both tires).

Per Andrew Stewart's post, another way to identify chronically low tire pressure is when you see "X X X X" marks on the sidewall of your tire. Non-tubeless tires do not tolerate excessive sidewall flex and quickly fatigue over time, causing sidewall failure (blowout).

SurferRosa

You should get a cushy ride on 28mm tires under your 140 lbs ... or what I would consider too cushy. Because required pressure is directly related to total weight (rider+bike), you won't have to pump 'em up much for your build. When using this calculator below, I get 64psi in the front and 68 in the rear. That's on 28's. And on pavement. Required pressure increases if you go down to 25's.

https://axs.sram.com/guides/tire/pressure

Canker

The correct answer is play around with it. You aren't going to die running 5 or 10 psi lower than what these calculators say for extra comfort. I prefer 55f/60r with my 28s and I'm 170lbs and I hit light single track and gravel occasionally.

Garthr

The Silca calculator is too high from my experience. At my combined weight of 190 and tire/wheel selection it suggests 55-57 psi. I ride Schwalbe Marathon Racers @33.5mm actual and I've never ridden them with more than 42 psi. They've been flawless. My road surfaces range from smooth to patch paved rutted hell with occasional township roads that are a mixture of gravel, rock, dirt and totally irregular.

I suspect the OP could go down into the 50's without issue. As been stated, do experiment on your own !

freeranger

I'm riding a different brand but same size tire as you and weigh around 12-13lbs. more. 65 to 72 psi is working for me. The Silca chart is a good recommendation.

Crankycrank

+1. All good advice so far but as Canker says you have to experiment for your riding. Start out with the 70 psi that was mentioned and try higher and lower pressures. I would like to use around 80 psi for my current tires for a nice juicy ride but the crappy roads I ride on make it necessary to use 100 psi to avoid pinch flats and bent rims which is just one reason to adjust any recommended pressure to what works for you.

79pmooney

Caution - pump gauges are often far enough off spec that comparing someone else's pressure and results to yours using different pumps and gauges can be comparing prices and not saying what country's dollar is being used.

Edit: I just looked back at my previous post and got reminded of my bike shop days. Our mechanic had a customer who could trash any wheel. The mechanic built him bulletrpoof ones he trashed. It was a shop running joke. I used to race on super light wheels on poor New England roads and only dented rims on a set of classic old railroad tracks in the finishing mile of a big race. (And yes, my tire pressure was too low! Purposely didn't pump them hard because I knew miles 90 to 102 was on a very rough old road. Raced the route the year before. Race start got delayed 2 hours. So my latex tubed sewups were 6 hours past inflation, not four when I hit those tracks.)

squirtdad

rene herse tool, not just for their tired https://www.renehersecycles.com/tire...re-calculator/

zandoval 

Just went out and checked my bikes... WOW!

It was pretty good match for my Kenda 184, and my Continental Ride Tour tires 32, 34...

frogman

Thanks for sharing squirtdad. Excellent resource !

pdlamb

Start with one of the calculators, go for a ride. Next week, add 5-10 psi and keep riding. If you're not getting shaken too badly, and it feels like the calculator pressure was riding on a muddy road, kick it up another 5-10 psi and try again. According to these calculators, I should be happy with 50-55 psi on my larger tires (with my heavier weight), but after pushing hard for 6 months, I tried adding pressure. At 70 psi I feel like I'm flying! Unfortunately, the roads haven't gotten any better, but they also don't feel much worse.

FWIW, if you can find a copy of Frank Berto's chart online, my 70 psi optimum is about what his chart recommends.

soyabean

Sounds like you want the minimum possible for maximum comfort.

May I suggest Schwalbe Big Apple balloon tires, they only need 2.0 bars.