datlas 

The Hirame chuck is so good! I smile every time I use it. I know it’s not cheap but even this cheapskate thinks it’s worth it!

colnago62

After running through my stash of Victoria Corsas, I put on some 4 Seasons. Holy smokes, they seem as stiff as Gatorskins. I was under the impression they were closer to GP4000’s than Gatorskins. I haven’t rode them yet, so I will hold judgment.

Kapusta

The calculator is based on the 15% drop graphs described here.

I used to use the Dorky Pants Tire Pressure Calculator which is based on that, but now it appears to just be an excel spread sheet. I think the owner of it must be asleep at the wheel.

But keep in mind, any of the pressure calculators are just starting point. Though for me, those 15% drop graphs are in the ballpark for me. For larger tires, I end up lower than the chart. For smaller tires I go a tad higher or I get pinch flats (actually, I don't do tires under 35mm anymore)

Some tires deal better with lower pressures that others. You just have to experiment. each tire is different, even ones of the same size.

Symox

Went riding on my favorite hilly area. This time used 70 psi front and back. Was awesome. Bit more cushy and stuck to the road beautifully.

For those who don't like Gatorskins, you might want to drop the pressure and try again if you have not. I'm quite impressed with the performance.

Leinster

I have the GP 4000 sII on 2 bikes. I have another pair in my garage, bought just as the 5000s was announced, to install when one of the other pairs wear out. When the garage pair wear out, I will probably buy the GP5000.

blacknbluebikes 

I run Gatorskins on the "long trip" bike, because those western jersey roads have decent shoulders covered with an amazing amount of sharp crap - I was flatting once or twice a month. I run GP4000 on the "quick bike" because I'll trade up into some extra performance versus flat risk. Now, having run Gators for quite a few thousand miles, maybe I have Stockholm Syndrome, but I don't think Gators deserve the ill-will I sometimes see around here. - Not as nice as the GP's, but certainly a good ride and a great tire that lives up to its promise. I guess some riders are much more sensitive to that kinda thing. (insert rule#5 pls). I have to add a couple PSI of air to both tires every 3rd day or so, and at 155lbs, I run them "about 80" PSI without much thought. I have gotten a pinch flat on GP4000's at about 70PSI when I hit a small pothole at about 15mph. BANG. ooooh, getting squishy... yep, pull over. A pothole in New Jersey? Shocking. I'll keep 'em all around 80 going forward. Works for me.

Symox

Agreed. I don't claim to be a road tire connoisseur, but for the weekend 30+ hilly rides I do, the Gatorskin 28s at 70psi feel fantastic to me. Cushy and confidence inspiring on turns.

Just for kicks, I pumped them up to 110psi to test out. BIG difference in twitchiness and road feel (as in, I feel everything).

I highly recommend anyone who hasn't tried it to run Gatorskins at lower pressures and reevaluate.

Branko D

Every tire is going to feel way better if inflated to a pressure which is on the "comfort" side of optimal pressure rather than inflated to maximum possible, that holds for good tires as well as Gatorskins.

With good tires, you simply get more speed and comfort at the same effort and tire pressure; the differences between a Gatorskin and a GP5000 are big enough to actually be able to measure them pretty easily with a decent hill, GPS and a powermeter, you don't need fun with maths to tease out the data. They kind of made sense for people who really needed the flat protection but now road tubeless works well, that'd be my first port of call if I had big issues with flats.

Drew Eckhardt 

It's more than you need in your front tire.

https://www.quora.com/How-much-air-s.../Drew-Eckhardt

At 155 pounds with an all-up weight around 180 and 45/55% weight balance you might have 80 pounds on the front wheel which suggests 60 psi according to the 15% drop rule of thumb and 100 on the rear calling for 75 psi.

I'd leave the rear alone and see how the front feels with 10 psi less.

At your weight I start my week on 25mm GP4000SII tires at 85/95 psi and finish at 75/85 without pinch flat problems.

datlas 

I think this is very reasonable.

That said, is there really any science behind the 15% drop rule?? I suspect not. Why not 12%? Or 18%?? A different percent drop will of course give you a different pressure.

Drew Eckhardt 

Frank Berto determined it empirically as the point at which you got a good ride but rolling resistance did not increase appreciably.

Kapusta

I am guessing that the precise amount of optimum drop is going to change depending on the tire. I take 15% as a good ballpark. I reference that chart a lot, but I never treat it like the final word. With hard garden hose tires I run them higher, with high quality supple tires (like RH Superlights) I run lower.

Branko D

No. It's not an a well answered question how accurate are the pressures to achieve 15% tire drop across various tires, even.

Bicyclerollingresistance.com guys tested GP5000s and to achieve 15% tire drop with a 42.5kg (94lb) load the pressures were 108 psi (23mm), 100 psi (25mm), 90 psi (28mm) and 75 psi for the 32mm version. That's a big disagreement with the chart especially for the 32mm tires, about 15 psi which is a difference of 25%.

It stands to reason that tire drop would depend not only on pressure and wheel load but also on how stiff the tire sidewalls are (which would allow using more supple tires at higher pressures to achieve the same comfort), the overall shape and height of tire as inflated, rim width and so on.
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Symox

I was wondering how the tire construction and only width was factoring into this. That makes sense.

esasjl

I'm running 50 psi with WTB Exposure 30-622 (measures 32) and 200 lb train weight. This is a bit less than the Berto chart but seems to work very well. I also have 26-622 Cayuse Pass (widest that fits my Pug) at 70 psi.
Steve

DaveSSS 

Those quoting really low pressures might want to check their gage accuracy. I recently found mine to be off by 8 psi. Zipp's calculator recommends some really low pressures for tubeless tires, but they wouldn't go anywhere near 50 psi for a 200 lb rider.

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

kcjc

I normally pump it just under 80 psi and it's in the mid 60s when refilling two to three weeks later. At 170-180 lbs, I would say 70psi is my sweet spot and never had a problem with pinch flats.

SapInMyBlood

The tire pressure will decrease once the temperature lowers. So it will still be similar once outside

Symox

Did a bunch of experiments and am finding

75psi rear and 65psi front seems to be the sweet spot with 28cm Gatorskins, 700cm Mavic Open Pros, my bike weight of 18lbs, my weight of 155lbs, my style of riding and my road conditions.


thanks for everyone’s help, I have learned a lot and improved the quality of my ride due to the replies so far.

love this forum!

esasjl

Excellent point about gauge accuracy, especially at low pressures. SRAMs guide gives me 53 psi with tubed 32 mm tyres on 21 mm rims and 200 lb gross weight. Berto's chart gives about 58 psi with 100 lb per wheel for nominal 15% drop. WTB give 35 - 65 psi for the 30-622 Exposure (measures 32 mm). 50 psi seems quite low but seems to be working well so far.

nycphotography

At 160lbs, I run 80-90psi in 25mm tubeless tires.

If I were moving to 28mm tires, I'd be trying 60-70psi and see how they ride.

Symox

I have been riding 75psi rear and 65psi with Gatorskin 28s front for a while now and it is fantastic. Great grip in rain or shine as well as damping.

Don't know how Gatorskins compare to higher end tires but I am absolutely a fan of these tires!!!

am0n

What this guy said. I run my 25s at 80F/90R and I am 185. You could be running 28s even lighter than 80 if you are only 155.

And to add, I've never had any issues with running 80/90. In fact, I've run slightly less without any issue either.

force10

+1. 80F/85R here at 215 on 28's here w/o any problem.

phrantic09

I run 70/70 weighing 175 with an 18mm internal rim. Works great for me.