Surly black floyd fat-tire: Lowest tire pressure?

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thunderstorm80   1 kW

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Surly black floyd fat-tire: Lowest tire pressure?

Post by thunderstorm80 » Sep 05 2017 10:58am

I have just finished a new E-fatbike build, which uses Crystalyte TC4080 as the front motor.
Let's put a side the front/rear discussions and why I chose the TC4080 - I want to focus on the tire pressure:
The tires are Surly black floyd 26x3.8 (or more closer to 4.0) on 80mm rims.
The max pressure is indicated on the tyre as 30PSI.
The bike is intended for urban commuting, and I chose Fat-Bike as we have many deep pot-holes and as I need to get off/on sidewalk crossings alot which I would like to pass without coming to a near-stop every time.
I started riding with 15PSI - The tire was quite stiff and bouncy and I felt it's still too much for going on/off sidewalks without coming to a near stop.
I lowered to 9-10PSI: At this point the cushioning was perfect, but the rolling drag has became significant, as expected. Also the self-steering, with the added rotating 9kg motor mass became very noticeable, but I don't care. My goal is the cushion and the suspension. (You can damage a standard MTB motorized-rim (with standard 2inch+ tires and with a 9KG motor) when you jump on/off sidewalks, even if you use full-suspension bike, since the weight of the motor sits below the suspension(s) so it's unsprung weight)
My question is how low can I get with the pressure, without causing increased wear and tear on the tire?
At 9-10PSI the tire is already "audible" - you can actually hear the drag, :D but I am still very far from squishing it to be even close to the rim, which means I can go down more - rim perspective.
The combined weight is around 130Kg, with all the electricity and including loaded panniers.

botz244   10 W

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Re: Surly black floyd fat-tire: Lowest tire pressure?

Post by botz244 » Sep 30 2017 4:00am

yep ive been down that road and it sucked ass on the front. used them on the front for like 2 days. a great short term tire. a short tire life and too prone to flats. i killed a rear tire in like 6 weeks 24 miles a day 6 days a week. my bike weighs 80 lbs and im 240, i have a Salsa Ti mukluk and front and rear carbon rims and front carbon fork. you have alittle rirt on the pavement and the front is goin to wash out. 90 % of the time im on the runnin 35 psi on the rear but with the hookworm and its only 2.5 wide and on a 65mm rim. the front is a 80mm and with a v rubber 4.0. at 15 psi. the fornt is right at the point were theres no self steer for pressure

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Johne-bike   10 W

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Re: Surly black floyd fat-tire: Lowest tire pressure?

Post by Johne-bike » Sep 30 2017 8:48am

I'm running Chaoyang 26x4.9 Big Daddy tires on 80mm front rim and 100mm rear rim, with a rear mounted Mxus 3000w hub. I run the fronts at 10psi and 11psi in the rear.. Bike and rider about 110kgs.
I have covered nearly 3000kms on these tyres.. About half worn now, and my riding is on road and hard pack trails. Apart from being pretty noisy, they are great tyres for my use. Very cushioned ride, no self steering, great on road and gravel and sandy trails, and no punctures! I highly recommend them!
If I could only find anyone in Thailand or even Asia that could supply a replacement set.. Impossible to find.. Even the tire manufacturers office in Thailand admits that don't import them.. Yet they are the most widely fitted OEM tires around.. Crazy world.. I'll end up having to import a replacement set from Ridewill in Italy, when these give up the ghost!

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Drunkskunk   100 GW

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Re: Surly black floyd fat-tire: Lowest tire pressure?

Post by Drunkskunk » Sep 30 2017 1:38pm

I run as low as 3 pounds on sand and mud, on the rear. I keep the front up around 6 for better steering. 3 pounds on the street would lead to pinch flats, though. I run in the 20s on the street, but i bet I'm running heavier and faster.

If you have a tubeless setup, 8 pounds is about the minimum.

Most of the good fat tire brands are either made under contract by Innova tire, or Vee Rubber. the tires i've tried are all very different, but share a few characteristics based on the original manufacturer.

In my experience, lower pressure on the Innova brands (Surly, and a few others) increases their lifespan. they wear more evenly at lower pressure, and wear out the center quick at higher pressures. The Vee rubber brands (Vee, Sterling, a few others) seem wear out their sidewalls at very low pressure, but are made of a harder rubber that wears longer at higher pressure.

Take that with a grain of salt, though. I tend to get 150 miles out of a tire on my monster.
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fechter   100 GW

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Re: Surly black floyd fat-tire: Lowest tire pressure?

Post by fechter » Sep 30 2017 2:45pm

I have some Kenda Juggernauts on my fat bike and found I like about 10 psi in the front and about 12 on the rear. I'm surprised by how low the rolling resistance is compared to my other bike that runs moped tires at 40psi. I tried running them at 30psi and they were way too bouncy
"One test is worth a thousand opinions"

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