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Fat Camp Show #3 – Fat-bike Geometry
Show Notes:
- There is a good diagram and calculator for the “trail” of a bike at: Bicycle Trail Calculator
- Mike Curiak – “Mikesee” on MTBR – http://forums.mtbr.com/fat-bikes/things-dont-always-have-so-black-white-927381-post11439866.html#post11439866
- “Progressive”/“New School”/”Trail” Geometry
- Slack (69 degrees or less), low (under 12.5”) and tight (16.5-17”)
- Fat Bike “Snow” Geometry
- Slack, low and tight – Hey, isn’t this the same as above?
- Singletrack race geometry
- Steep (over 71 degrees), tight (16.5-17”) and high (over 12.5”)
- “Normal” XC Geometry
- Neither steep nor slack (70ish degrees), Medium length (17.25-17.5”) and medium height (12-12.25”)
hello love the show!! I have been fat biking for about 4 years now. just got into racing this past winter really got the tire pleasure figured out in the fat bike and my zombie wheeled 29 but my question just got a sarma 29+ I will be going tubless needing to know about what tire pressed to start running my fatbike I run 3.5-9LBS my 29 18-25 so my 29+ ???? also I weight in at 155-165 thanks for everything and again love the show
I would suggest starting around 13-14psi and going down from there. There are a ton of variables that come into play for what is the optimal tire pressure for any given rider and trail and personal preference also plays a big role.
Your experience may be very different but for perspective I run similar pressures in my fat and 29er tires to what you listed and run around 12psi front/13 rear for all of the “true” 3″ 29+ tires and 13psi front and 14.5psi rear on the tires that are a touch smaller (Dirt Wizard and Fat B Nimble).
Enjoyed the show, lots of good information. The bike I had with the best frame geometry for me and the way I ride was a 1984 Panasonic ATB. A nice laid back 68 degree head tube angle.
I recently got a fat bike, a cheap and heavy Mongoose Malus. I wanted to try fat without spending a lot of money. The first thing I noticed riding was that the bike has a lot of oversteer. If I turn the handle bars past about 15 degrees, left or right, they just want to keep turning. Not the bike to ride no hands. What in a geometry would cause this? Is it common in fat bikes? Thanks.
Thanks Bob!
I am guessing you are experiencing “self steer” from the tires and not a geometry thing based upon what you describe. Certain tires are especially prone to self steer and lower pressures and harder surfaces exacerbate the degree of self steer you feel.
I would recommend running a bit higher pressure (2-4psi should do it in most situations if you are running 7-10psi currently) and seeing if what you are feeling decreases in effect. If the thing you are feeling isn’t as bad, you know it is the tire and not a geometry issue.