nycebo wrote:Backdoor, that's a cool photo. Given your weight and that photo, I think you could even get away with 75-80. Might be worth replicating the test and photo to see the differences. Thanks for sharing.
If I remember I think 60-65psi was the cushiest ride for me with a decent cushion for the rim with the 28c. Great for full on gravel or mixed rock trails. But it's a slog on harder pack dirt, gravel or road if you are on the flats or climbing.
I'm on the road for another week or so, when I get back home, If I remember I'll take some more photos at multiple PSI levels.
For speed on the tarmac, I've got a good section of downhill that's about 2.4 miles long. It's a section that I can ride from top to bottom without pedaling and I'll hit speeds from 35+ mph to 6mph and anywhere in between. It has sections from -15% to +4%. I've done this ride using multiple pressures to see if the different pressures make a difference in speeds going down the hill.
In reps of 3, I have found that between 85 and 95 psi on the 28c tires gives me the best speed. If I drop below 85 psi then I start to lose speed and above 95 there is very little if any measurable difference.
Keep in mind that my weight, bike weight, road conditions, road type (its chip sealed), weather and tire type (Conti Grand Sport 28s) all play into this number. I didnt save any of the data and cant recall any of the exact numbers.
I do remember the differences were minimal but repeatable using 10psi increments. (I think I used 100, 90, 80 and 70 then tried 85 and 95 without reps as riding up this hill 14 times (30 miles of climbing) was exhausting)
Not super scientific but was suprised at the repeatability of the results and it was fun to do just to see how the pressures of the tire made a difference. So many articles talk about tire pressures but never mention the weight of the rider.
I see posts all the time that riders are like - I keep my tires at 20psi. But they never mention that they weight 120lbs and are riding 40c tires.
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