Why am I getting flats?!?

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Why am I getting flats?!?
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flag iamhans
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Posted: Feb 28, 2022 at 9:46 Quote
I’ve got a new (to me) fat bike. This winter I have gotten burp flats any time I ride with my pressure below 6 psi. Both times it was on my rear wheel which is a 27.5 Mulefut 65. The first time I was running a Vanhelga 4.0 tire which had come with the bike but had new sealant in it (Orange seal standard mix). Thinking that the tires might have been too worn, I replaced them with new Vee Tire Snow Balls in 4.0 and Orange Seal Subzero and it happened again. I talk to people on the trail who are running 4 psi or less and they don’t have any issues. What could be going on with my setup?
flag mark027
Posted: Feb 28, 2022 at 10:20 Quote
Those are awesome rims, I have a set of those for the summer. Running low pressure hasn’t caused any burp for me ever.
First make sure you have a dedicated gauge, they typically only go up to 15psi so you know your running 4 psi or whatever.
The obvious thing jumping out at me is if the tire bead is seated properly around the rim? You can still have the tire hold air and look fine with it being seated incorrectly. Have a look and make sure, there’s normally a line running along the wheel by the bead, check that it’s the same distance from the rim running all around your tires.
flag zeeino
Posted: Feb 28, 2022 at 16:28 Quote
I would've guessed that your rims are too narrow, but if they're working for mark027, then it must be something else. If you don't end up finding a fix, an option is to go with revoloop tubes or something similar. They're pricey, but comparable in weight to tubeless, and very durable.
flag iamhans
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Posted: Feb 28, 2022 at 19:33 Quote
zeeino wrote:
I would've guessed that your rims are too narrow, but if they're working for mark027, then it must be something else. If you don't end up finding a fix, an option is to go with revoloop tubes or something similar. They're pricey, but comparable in weight to tubeless, and very durable.

You might have something there RE the rim being too narrow. The front is 80mm and the rear is 65mm. I don’t know why they are different. Maybe the previous owner was trying to skinny up the rear tire to fit between the chain stays. I’ve only had burp flats on the rear. I was thinking that was because that’s where all of the weight from my fat butt was carried, but it might be the narrower rim. I also didn’t have any issues with the rear when I was running Minion 3.8s this summer even though I was riding much harder.

New plan is to rebuild the rear rim to 80mm.

I liked the way the minions rode in the summer, so maybe I build a second wheel set at around 65mm rim width for them.

I can’t seem to find Mulefut 65s anywhere. Were they discontinued?
flag mark027
Posted: Mar 1, 2022 at 3:01 Quote
Hopefully that fixes your problem.
Check out borealisbikes if you want another 65, im pretty sure they only sell them as a set of 2 though
flag iamhans
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Posted: Mar 1, 2022 at 7:33 Quote
mark027 wrote:
Hopefully that fixes your problem.
Check out borealisbikes if you want another 65, im pretty sure they only sell them as a set of 2 though

I saw that. $1k is pretty steep for a pair of alloy rims. I wonder how good their hubs are.

I thought about buying a pair from them that are the inverse of what I have so that I end up with two wheel sets: 65mm to run 3.8 minions in the summer at 80mm to run 4.5 something-studded in the winter. We'll see.

Thanks for your help!
flag mark027
Posted: Mar 1, 2022 at 8:32 Quote
iamhans wrote:
mark027 wrote:
Hopefully that fixes your problem.
Check out borealisbikes if you want another 65, im pretty sure they only sell them as a set of 2 though

I saw that. $1k is pretty steep for a pair of alloy rims. I wonder how good their hubs are.

I thought about buying a pair from them that are the inverse of what I have so that I end up with two wheel sets: 65mm to run 3.8 minions in the summer at 80mm to run 4.5 something-studded in the winter. We'll see.

Thanks for your help!

Yea man it’s expensive, I got a discount when I got them, i have their hubs on my hed wheels too, pretty nice hubs. I’ve only used borealis so I can’t compare much but I like them a lot.
That’s what I do, 65 with 3.8 summers and 80 with Studded cake eaters 4.5 winter. I didn’t want the 29 plus for summer cause I thought it would look too ugly but I do have a lauf suspension so maybe you can’t trust me.
Two wheelsets are worth it.
flag zeeino
Posted: Mar 2, 2022 at 17:36 Quote
I have studded 27.5x4.5 Bontrager Gnarwhals on mulefut 80, and studded 27.5x4.5 Dillinger5s on the same rims. Here are some numbers that might be helpful for determining what might fit:

Dillinger5 is 111.5mm at the widest point, and 383mm from floor to axle center.

Gnarwhal is 107.5mm at widest point, and 381.5mm from floor to axle center.

I have a 29+ summer wheelset that I run with 120mm travel Pike. Very few people notice that my Fatcaad is a Fatbike with that setup, and it''s so much fun and capable that I often ride it instead of my FS.
flag iamhans
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Posted: Mar 3, 2022 at 14:00 Quote
zeeino wrote:
I have studded 27.5x4.5 Bontrager Gnarwhals on mulefut 80, and studded 27.5x4.5 Dillinger5s on the same rims. Here are some numbers that might be helpful for determining what might fit:

Dillinger5 is 111.5mm at the widest point, and 383mm from floor to axle center.

Gnarwhal is 107.5mm at widest point, and 381.5mm from floor to axle center.

I have a 29+ summer wheelset that I run with 120mm travel Pike. Very few people notice that my Fatcaad is a Fatbike with that setup, and it''s so much fun and capable that I often ride it instead of my FS.

Thanks for these numbers. They are very helpful! A friend has those Dillinger 5s on 80mm rims and they looked HUGE to me. I'm surprised to learn they are only 111.5mm. Looks like the Gnarwhal is a better option for me, anyway.

How wide are your 29+ rims? A buddy is selling some built on i35 rims, but that seems too narrow. I thought that i40 was about as skinny as I'd want to go to run 2.8-3.0 tires.
flag zeeino
Posted: Mar 3, 2022 at 15:28 Quote
My rims are Duroc 40 (36mm internal width). The Duroc is a good option because the spoke holes are a little angled which reduces the steep angle to the hub a bit, and you can get a boost front if you decide to go with a boost fork. I'm just under 200lbs and running 29x3.0 at 12 and 13 psi, and the front burps a little from time to time on technical terrain, but not enough for it to be an issue! I just notice sealant on the sidewall at the end of the ride.

I considered going with the Duroc 50, which is likely ideal, but I wanted to keep the option of running narrower tires when it gets muddy in the spring and early fall.

The 29x3.0 also looked ok and worked on a 30mm internal width wheelset I have, but I didn't dare to set them up tubless.
flag iamhans
O+
Posted: Apr 5, 2022 at 7:04 Quote
Has anyone used Fatty Strippers? http://fattystripper.com/index.html

These look like they would take care of the flats I'm getting on my Mulefut rims set up tubeless.
flag AndrewDClfL6
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Posted: Apr 6, 2022 at 13:19 Quote
iamhans wrote:
Has anyone used Fatty Strippers? http://fattystripper.com/index.html

These look like they would take care of the flats I'm getting on my Mulefut rims set up tubeless.

I used a set on some Surly Nates mounted on the OE wheels on an old Charge Maxi last year. I had no problems with burping tires with pretty low pressures.
flag bazz77
Posted: Oct 23, 2022 at 16:57 Quote
I have experienced this exact same problem running mulefut 80s with dillinger5s. I also experienced this on stock 90mm rims on my giant Yukon and terrene cakeeaters. The only way I can avoid it is by running 10psi or higher. I'm very experienced in setting up tubeless wheels, so I'm confident it was done right. I did redo it multiple times nonetheless.
I've tried ethirteen plasma sealant as well as stans (BTW, I prefer the plasma as it does not sweat out the sidewalls like stans). Same problem with both brands.
Front seals up fine; it's just the rear that burps due to my body weight coming down on it over bumps (I'm 175lbs). I gave up mid-season last year and put a revoloop in, but I've since tried going back tubeless and it seems to be still burping, although I set it up a month ago and it does seem to be getting a bit better although I haven't ridden it much yet. Time will tell once the snow flies!
flag tfdhusker
O+
Posted: Dec 7, 2022 at 7:28 Quote
iamhans wrote:
Has anyone used Fatty Strippers? http://fattystripper.com/index.html

These look like they would take care of the flats I'm getting on my Mulefut rims set up tubeless.

I use them on my wife’s bike with Mulefut 80’s. I’ve never had a problem with them slipping or burping and we ride sand/snow at low pressure exclusively. Watch the YouTube vid and use the spray glue on the rim method.
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