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  1. #1
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    Specialized Fat Boy: How I went tubless

    There is already plenty of information on how to convert to tubeless, but Specialized Fat Boy rims have special needs because of the 10 vent holes in the rims. If you don't cover these holes, the air will escape out from the seams. Here's a pictorial of how I did it. The objective was to keep it simple, light and inexpensive.

    I just got this Expert model 24 hours ago and did the modification before it ever hit the dirt.

    Here are the vent holes, there are ten total. I supposed they were drilled to vent gas in the manufacturing process, but I don't know for sure.


    The first thing was to deburr the holes as they had some rough edges.
    I used a countersink cutter. Just knock the sharp edge off.




    Using 91% alcohol, the rim and any area where the tape will contact was cleaned. Make sure to clean your finger tips with the alcohol too as this keeps the tape from getting contaminated.
    Tubeless rim tape was first applied at the seam of the rim. Trim with razor blade.


    A piece of rim tape is cut to span and cover the holes. Make sure the tape has no wrinkles as it tapers into the red rim band. It took a few tries for me.




    After all the small holes are covered, it's time to apply the Gorilla tape.
    One layer of 3" wide tape is all it gets. The first thing was to cut a hole for the valve stem. I used a cardboard hole cutter (from Harbor Freight) to make a nice hole.


    With a block of wood, apply a layer of tape. This keeps the wood debris out of the actual piece that will be used. Lay the tape over the tape covered block.

  2. #2
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    Drill the tape in the center with a 6" leader to the edge.


    Nice hole.


    Place the Stan's valve stem through the tape and into the hole of the rim to center the new rim strap.


    Start working the tape around the rim. Don't worry about the center, the edges are all that matter. Make sure there are no wrinkles here.


    Take out the valve stem and reinstall the tube and tire. Air it up to 25 psi or so and let the tape glue cure for a bit.
    I took off the tire at this point and you can see that the pressure pressed the tape in the center nicely.


    Take the tube out and reinstall the Stan's stem. Put the tire on and inflate. There should be very little air leaking out. If there is, find the problem and fix it. It's easier to fix the problem without the mess of the Stans goop to deal with.
    Once you are satisfied with the results, add 6 oz of Stans.

    After I added the Stans, there was only one tiny leak (at the seam) that the Stans quickly took care of.

  3. #3
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    Re: Specialized Fat Boy: How I went tubless

    Cool thanks.

    Have you ridden it yet? Any issues with running super low pressures on those hook less rims?

  4. #4
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    Specialized Fat Boy: How I went tubless

    Excellent write up thanks.

  5. #5
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    Great write up!

  6. #6
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    Quote Originally Posted by matto6 View Post
    Cool thanks.

    Have you ridden it yet? Any issues with running super low pressures on those hook less rims?
    I haven't ridden the bike at all. The maiden voyage will be this Thursday when I will be riding the entire 130 mile Mojave Road. Hope it works, but if there is a problem, I'll bring some tubes.
    I wanted to get this down while it was fresh in my head. I'll let you know how it worked out.

  7. #7
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    nice work raspberry, see you Thursday

  8. #8
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    I replaced the flat pedals with Ti clipless and removed the inner tubes.
    That's it. Here's where it's at.
    Attached Thumbnails Attached Thumbnails Specialized Fat Boy:  How I went tubless-dsc_0394.jpg  


  9. #9
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    The tubes came in at 2 lbs 7 oz. for the pair.

  10. #10
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    Awesome! Appreciate the walkthrough.

  11. #11
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    I tried to do tubeless with tape on the front of my Fatboy. I didn't cover those holes individually instead I ran two strips of tape around the rim, with the tape going almost all the way to the edge of the rim.

    I could never get the tire to hold air for more than an hour or so. I looked at it a week later (much riding in between with the tube back in) and found that the tape did not adhere to anything in there - rimstrip or rim. The tape had pulled back from the edge exposing those holes, which is where I was losing air. It was really easy to pull the tape off, which is not good - it wasn't stuck to anything.

    I am not sure if I got a bad roll of tape or there is something on the rim that makes the tape not stick. I did it inside at room temp, so it wasn't a cold thing. I ended up going split tube with the front (which worked great and is probably about the same weight as two layers of tape). I'm going to take your lead here and try the back tire with tape again, but this time I'll wipe the entire rim with alcohol, maybe there's something on the rim.

    I'll be interested to hear your longer term review, and if the tape stays in place.

    The rim has a good bead pocket and I expect that it should hold the bead in place better than some rims - no need for foam or anything else to create a ridge.
    Big Strings, Big Wheels, The Jisch Blog

  12. #12
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    I've been tubeless of my Fatboy since I got my in Dec. Basically the same setup. One strip along the left edge then right and one down the center. I've had it down to 2 psi. However I think the sweet spot is between 7-8 psi.

    Sent from my RM-893_nam_tmous_201 using Tapatalk

  13. #13
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    Excellent write-up and pictures.
    Thank you for posting!

  14. #14
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    Is that Kapton Tape?

  15. #15
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    Its Gorilla Tape
    Big Strings, Big Wheels, The Jisch Blog

  16. #16
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    No, the clear / orange'ish tape used to plug the 'vent' holes. Not the black gorilla tape. It was called just 'tubeless rim tape' i guess? It's not yellow like Stans tape, it looks like kapton tape to me.

  17. #17
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    gotcha, I don't know about that tape.
    Big Strings, Big Wheels, The Jisch Blog

  18. #18
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    Quote Originally Posted by drolic View Post
    Is that Kapton Tape?
    The roll says "Rim Tape DT Tubeless"
    Honestly, I don't know. The guys at the local bike shop gave me some for the project.
    I bet you could even use packing or gorilla tape for the holes.

    I thought about silicone for the holes. The problem is that if the silicone is on anything but in the hole, the tape will not stick to it.
    One might be able to use tiny self tapping screws to plug the hole. That would actually be a pretty solid way to do it. The biggest leak is at the seam.

    Both tires were flat this morning. I'm not worried because I didn't ride the bike after doing the job. I aired them up and shook them - they're holding fine.

  19. #19
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    great write up!

  20. #20
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    Let us know if they hold air in the long term.

    Sent from my HTC6500LVW using Tapatalk
    Big Strings, Big Wheels, The Jisch Blog

  21. #21
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    Update!

    Fail.

    The tires were holding air but I decided to dismount them to have a looksie.
    It appears that the Stan's doesn't agree with the gorilla tape glue. Mostly, the tape was sealing just fine to the aluminum rim. There were breeches where the sealant got underneath the tape


    I thought about redoing it with two layers of tape that would span the entire distance, but then there is still a seam where the Stan's could penetrate.

    I went ghetto. It wasn't worth messing with the tape anymore. I'm sure it works for some, but I didn't feel confident with it.

    In haste, I promptly sliced an inner tube to do the ghetto fix when I realized I cut a 26" tube. No bueno. I forgot you need to start with a 24" tube. Back to the store for 24" presta tubes. All they had were stupid thick down hill tubes, but at this point I gotta get it done.

    Here's the filleted 24" tube


    Of course, it ends up with these flaps.


    I know it's going to be more difficult to service, but I couldn't stand the flaps so I did a circumcision. The flap strips came to 140 grams per tire.


    This *should* take care of it. I'll let you know.

  22. #22
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    Split tube. Tried and true. Not the lightest but the best!

  23. #23
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    So is the hassle of doing all this worth it for a fatbike? What's your primary motivation?

    I know that on a skinnier tires tubless allows you to run lower pressures without pinch flatting. But is that even true on a fatty? Does burping kick in before or after pinch flatting?

  24. #24
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    Quote Originally Posted by matto6 View Post
    So is the hassle of doing all this worth it for a fatbike? What's your primary motivation?

    I know that on a skinnier tires tubless allows you to run lower pressures without pinch flatting. But is that even true on a fatty? Does burping kick in before or after pinch flatting?
    1. I'm riding the Mojave Road tomorrow. 130 miles through the desert with thorns hiding all over. The Stan's keeps me pedaling instead of fixing flats. I hope.
    2. Less rotating weight. Even with the split tube, I still lost at least a pound.

    Some say tires roll easier without tubes, I can't really tell the difference.

    I don't have any experience with pinch flatting on fatties or any experience riding fatties at all for that matter.

  25. #25
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    Yeah Excellent write up, thank you too. It starts to answer some questions that have been just theoretical in my head, until now.
    It's not dirt in my apartment --it's Earth.

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