Smallest tire on a fat tire rim?

[Cybersnow]

I am looking at a Velotric step through bike that is not really a MTB but would probably do for where I ride…except it is a fat tire bike. How small of a tire can I go on those rims or would I have to go buy new rims or wheels?

 

[Greg Watts]

I am looking at a Velotric step through bike that is not really a MTB but would probably do for where I ride…except it is a fat tire bike. How small of a tire can I go on those rims or would I have to go buy new rims or wheels?

@Cybersnow - the short answer is: fat bike rims are quite wide internally (typically 65 - 80mm+), and there's a practical floor on how narrow a tyre you can safely run on them.

The general principle is that running a tyre too narrow for the rim makes it splay open into a square, rounded profile rather than sitting naturally curved - you lose cornering support and, more seriously, risk the bead unseating. @steve_sordy's post noted exactly this kind of issue: a tyre too narrow for its rim rolled off on the first flat corner. The WTB tyre/rim fit chart (mentioned by @GrahamPaul) is worth checking - it gives optimal and compatible ranges for specific rim widths.

The snag is: without knowing the exact internal rim width of the Velotric's wheels, I can't give you a hard minimum. Fat bike rims vary quite a bit - a 65mm internal width is a very different beast from an 80mm one. If you can find the internal width (usually stamped on the rim or in the spec sheet), that's the number to work from.

What I'd suggest practically: • Find the internal rim width of the Velotric's rims

• Check the WTB chart (or Schwalbe's equivalent) for that width • Realistically, dropping from say a 4.0" - 4.8" fat tyre down to a 3.0" - 3.5" on a wide fat rim is where it starts getting questionable - though some people run 3.8" on fat rims without drama

• Going below ~3.5" on a proper fat rim is where I'd start worrying about bead stability, especially at lower pressures

If the minimum compatible tyre is still wider than you want, new wheels would be the answer. What's the Velotric model? I can try to dig up the actual rim spec.

 

[Cybersnow]

@Cybersnow - the short answer is: fat bike rims are quite wide internally (typically 65 - 80mm+), and there's a practical floor on how narrow a tyre you can safely run on them.

The general principle is that running a tyre too narrow for the rim makes it splay open into a square, rounded profile rather than sitting naturally curved - you lose cornering support and, more seriously, risk the bead unseating. @steve_sordy's post noted exactly this kind of issue: a tyre too narrow for its rim rolled off on the first flat corner. The WTB tyre/rim fit chart (mentioned by @GrahamPaul) is worth checking - it gives optimal and compatible ranges for specific rim widths.

The snag is: without knowing the exact internal rim width of the Velotric's wheels, I can't give you a hard minimum. Fat bike rims vary quite a bit - a 65mm internal width is a very different beast from an 80mm one. If you can find the internal width (usually stamped on the rim or in the spec sheet), that's the number to work from.

What I'd suggest practically: • Find the internal rim width of the Velotric's rims

• Check the WTB chart (or Schwalbe's equivalent) for that width • Realistically, dropping from say a 4.0" - 4.8" fat tyre down to a 3.0" - 3.5" on a wide fat rim is where it starts getting questionable - though some people run 3.8" on fat rims without drama

• Going below ~3.5" on a proper fat rim is where I'd start worrying about bead stability, especially at lower pressures

If the minimum compatible tyre is still wider than you want, new wheels would be the answer. What's the Velotric model? I can try to dig up the actual rim spec.

The Velotric model is the nomad, but I am looking for that full suspension, easy mount/dismount and enough power to get me up the 25 degree grade to my home in the mountains.

 

[Greg Watts]

The Velotric model is the nomad, but I am looking for that full suspension, easy mount/dismount and enough power to get me up the 25 degree grade to my home in the mountains.

@Cybersnow - right, you've quietly changed the question and that's a good thing - let me catch up to where you actually are.

You're no longer asking "how narrow can I go on a fat rim." You want a full-suspension, step-through, serious-climber. The Nomad doesn't deliver any of those three: it has only an 80mm travel front suspension fork (no rear), and even the current Nomad 1 Plus is rated for "even on 15-degree inclines". A 25° grade is roughly a 47% gradient - well past what a comfort fat-tyre hub bike is built for. So the Nomad's out for what you want. Good instinct to pause on it.

Two honest paths here, and they fork hard: 1. If you want to stay in the Velotric/fat-bike world - the one model that's actually full-suspension is the Nomad 2X.

It runs air suspension with 120mm front, 80mm rear, and while it shares the 750W nominal rating, the 2X boosts peak power to 1400W and torque to 105 Nm, making it the strongest in Velotric's lineup.

In testing, the 2X handled steep inclines (20% grade) without requiring the rider to stand on the pedals.

That's still short of your 25°/47% though - I can't promise it'll haul you up that without a fight, and it's a hub-drive cadence/torque bike, not a mountain-goat mid-drive.

2. If you want something that genuinely eats a 47% climb home - that's mid-drive eMTB territory, and the maths is on your side there. A mid-drive multiplies through the bike's gears, so steep, loaded climbing is exactly where it shines versus a hub motor. As an engineer you'll appreciate why: the hub motor gives you raw torque at the wheel and bogs as the grade steepens; the mid-drive lets you gear down and keep the motor in its happy rev range.

The snag: I can't hand you a verified step-through full-power eMTB from my database - that combination is genuinely rare, and the candidates I can stand behind (Mondraker Crafty, Norco Range VLT, Cube Stereo Hybrid) are all standard high-top frames. I don't want to invent a step-through that fits.

So, two things from you so the next answer is the right one: • Budget ceiling? That's the single biggest filter.

• Is the step-through a hard requirement, or "easy to get a leg over"? Some low-standover/mid-step full-power eMTBs get you 90% of the way without a true step-through frame.

Tell me those and I'll give you a proper shortlist rather than a guess.

 

[Cybersnow]

@Cybersnow - right, you've quietly changed the question and that's a good thing - let me catch up to where you actually are.

You're no longer asking "how narrow can I go on a fat rim." You want a full-suspension, step-through, serious-climber. The Nomad doesn't deliver any of those three: it has only an 80mm travel front suspension fork (no rear), and even the current Nomad 1 Plus is rated for "even on 15-degree inclines". A 25° grade is roughly a 47% gradient - well past what a comfort fat-tyre hub bike is built for. So the Nomad's out for what you want. Good instinct to pause on it.

Two honest paths here, and they fork hard: 1. If you want to stay in the Velotric/fat-bike world - the one model that's actually full-suspension is the Nomad 2X.

It runs air suspension with 120mm front, 80mm rear, and while it shares the 750W nominal rating, the 2X boosts peak power to 1400W and torque to 105 Nm, making it the strongest in Velotric's lineup.

In testing, the 2X handled steep inclines (20% grade) without requiring the rider to stand on the pedals.

That's still short of your 25°/47% though - I can't promise it'll haul you up that without a fight, and it's a hub-drive cadence/torque bike, not a mountain-goat mid-drive.

2. If you want something that genuinely eats a 47% climb home - that's mid-drive eMTB territory, and the maths is on your side there. A mid-drive multiplies through the bike's gears, so steep, loaded climbing is exactly where it shines versus a hub motor. As an engineer you'll appreciate why: the hub motor gives you raw torque at the wheel and bogs as the grade steepens; the mid-drive lets you gear down and keep the motor in its happy rev range.

The snag: I can't hand you a verified step-through full-power eMTB from my database - that combination is genuinely rare, and the candidates I can stand behind (Mondraker Crafty, Norco Range VLT, Cube Stereo Hybrid) are all standard high-top frames. I don't want to invent a step-through that fits.

So, two things from you so the next answer is the right one: • Budget ceiling? That's the single biggest filter.

• Is the step-through a hard requirement, or "easy to get a leg over"? Some low-standover/mid-step full-power eMTBs get you 90% of the way without a true step-through frame.

Tell me those and I'll give you a proper shortlist rather than a guess.

Great questions. I guess my budget is somewhere in the $5K range though I am not adverse to going a little higher. If the top bar is lower and the bike has a drop saddle that might be what I need to mount and dismount the bike. While I can still comfortably mount and dismount my roadbike while moving, at 80 am anticipating maybe some balance problems in the next few years. I did see that a ew European bike companies are going to start selling step through EMTBs but I am looking for something that I can take to my local bike shop if or when I break something.

 

[Greg Watts]

Great questions. I guess my budget is somewhere in the $5K range though I am not adverse to going a little higher. If the top bar is lower and the bike has a drop saddle that might be what I need to mount and dismount the bike. While I can still comfortably mount and dismount my roadbike while movin...

@Cybersnow - that's exactly the right way to think about it, and it changes my answer in a useful way: if the top tube is low enough and you've got a dropper to get the saddle out of the way, you don't actually need a true step-through frame. A low-standover, mid-step full-power eMTB with a dropper does the same job - saddle drops, you swing a leg over a low bar, you're on. That opens the door a lot wider than "step-through eMTB", which as you've found is a very thin field.

The "take it to my local shop when it breaks" point is the smart one, and honestly it's the biggest filter here. In Idaho, that means I'd lean toward brands with a proper US dealer network rather than European direct-sales bikes - a Canyon or a Cube is lovely until you need a warranty motor swap and the nearest service point is an ocean away.

Now - the honest bit. I can't in good conscience hand you a verified shortlist from my database for $5K, US dealer support, low standover, 47% climb. The bikes I can stand behind (Norco Range VLT, Cube Stereo Hybrid, the Yeti/Pivot end) are mostly UK/EU-priced, high-top enduro frames well north of your budget, and I won't dress one up as something it isn't.

What genuinely matters for your 25° grade, regardless of brand: • Mid-drive, not hub - a mid-drive gears down and keeps climbing where a hub motor bogs. Non-negotiable for a 47% loaded climb.

• Big torque + granny gear - 85Nm+ and a 10-50/52T cassette so you can spin, not grind. • Low standover + dropper - does the mount/dismount job without needing a unicorn frame.

Two things that'll get you a real answer rather than a guess: • Are you set on buying new from a dealer, or open to a shop-supported brand you order and they assemble?

• Roughly how far/how much climbing per ride? That sets the battery you need. Tell me those and I'll point you at brands with US service that fit - properly, not hopefully.