i have a sondors bike that comes with a 4.0 fat tire. i am tring to find a street tire for my fat boy i only found one and its 3.5 not 4.0 STREET TIRE

  • What Moz said -- "Probably". Most of us here are not familiar with common practices for fitting fat tires, so we're going on the assumption that the rim will be, as typical for other widths, somewhere between about 60% and 80% of the width of the tire. So long as you stay below 80-90%, you should have few difficulties (though performance may not be ideal). Jan 22, 2017 at 21:26
  • A lot of fat bike rims are 70-80mm wide external (4" = 100mm so right in the ratio range you are describing). 3.5" is 88.9mm so it may be cutting it close.
    – Paul
    Jan 23, 2017 at 5:48
  • Probable duplicate of bicycles.stackexchange.com/questions/52587
    – Criggie
    May 16, 2023 at 18:19

3 Answers 3


A 26"x3.5 tire should work on any narrow 4" fat bike rim. That is: 60mm-70mm wide rims. It might work on an 80mm rim depending on the actual width of the tire. But will definitely not work on a 5" fat bike rim which is 100mm wide.

Surly does not recommend their Black Floyd (listed at 26"x3.8" but actually narrower) road tire for rims wider than 65mm, for comparison.

I tried to find the actual specs for a the rims on a Sondors Fat eBike, but it looks like there are a couple versions. One comes with 59mm rims, which should work for a smaller tire. However, the other version (with the 4.9" tires) might have a rim that is too wide for those tires.

The Apache Fatslick http://veetireco.com/listings/fat-tire-apache-fatty-slick/ is the only option I know of a "road" tire for a 5" rim.

  • Yea there original tires was 4.9 but there newer ones are smaller fat tires
    – BroManz
    Jan 23, 2017 at 20:55
  • @BroManz I would recommend measuring the inside width of your rims if they are less than 3" (80mm ish) then those 26"x3.5" tires should work.
    – JP May
    Jan 24, 2017 at 18:11

What matters is the width of the rim. It's unlikely that you rim is 4" wide, so you will be fine with a 3.5" tyre.

If you search for "narrow tyre" or "tyre width" here you will see quite a few questions about this, and the very general rule is that the rim should be narrower than the tyre. But I think yours is the first fat-bike question.

  • from my research i got a 59mm wide rim here
    – BroManz
    Jan 24, 2017 at 11:12
  • Yeah, then a 60mm wide tyre would be pushing it, but even 75mm/3" should be fine.
    – Móż
    Jan 24, 2017 at 20:40
  • thanks for all your help buts its more confuising cause u guys talk in mm vs3.5".... sooo its a little hard for me 2 figure out what size i can and cannot use
    – BroManz
    Jan 25, 2017 at 6:55
  • That;'s why I said "75mm/3"", so that you could hopefully read the "three inches" part and it would mean something to you.
    – Móż
    Jan 25, 2017 at 7:58
  • 1
    What do you think "you will be fine with a 3.5" tyre" means?
    – Móż
    Jan 25, 2017 at 21:51

Yes it fits easily, I use a 26x2.125 tire on a 26x80mm wheel. Gives a nice low profile look. Just use the non puncture proof tubes, so it can shape itself to the inside of the tire. I'm going to use 26x3.0 tires on my 26x4.0/100mm wheels

  • don't you mean : "I use a 26x2.125 tube on a 26x80mm tire" ? Jan 13, 2020 at 16:07
  • I'd be interested to see photos of this - I would suspect the bead hook, or crochet hook is not engaging very securely in the matching rim's hook.
    – Criggie
    Jan 16, 2022 at 6:55

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