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E-Bike Tires · CST

CST BFT (Big Fat Tire) 26x4.0

CST's BFT (Big Fat Tire) is a widely fitted original-equipment tire on 26x4 fat e-bikes and one of the cheapest ways to replace a worn one. The tread is a medium-knob all-rounder: it handles hardpack, sand and snow acceptably and hums a bit on pavement, which is the normal deal with fat tires. Wire-bead versions are the common, inexpensive ones; folding versions exist at a higher price. If you spend most of your time on the road, a smoother fat tire will roll easier, but for mixed use the BFT is a sensible default.

Replacing stock tires on 26x4 fat-tire e-bikesMixed pavement and trail ridingBudget-minded riders

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Key considerations

  • Confirm 26x4.0 (ETRTO 100-559), not 26x4.8 or 27.5x4
  • Rim width of 65–90 mm suits a 4.0 tire
  • Expect road hum and lower efficiency than a street tread
  • Check for a puncture-protection version if you ride debris-strewn roads

Pros

  • Inexpensive OEM-style replacement
  • Decent all-round grip
  • Easy to find

Considerations

  • Road noise
  • Heavy wire-bead construction
  • Not the fastest-rolling fat tire

Features & specifications

Size26x4.0

Specifications are manufacturer-published figures or our own notes; confirm on the current listing before purchase.

Compatibility notes

  • 26-inch (559 mm) fat-bike rims, typically 65–90 mm wide

Goes well with

Related accessories

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Replacement parts

Confirm fitment on your bike before ordering — see each part’s compatibility notes.

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Inner Tubes

26x4.0 Fat Tire Inner Tube, Schrader Valve (generic)

The 26x4 tube is the full-size fat-bike counterpart to the 20x4 folder tube, and it is what most 26-inch fat e-bikes run. Generic butyl tubes in 26 x 3.5–4.5 (or 4.0–4.9) are widely sold; the branded ones from Kenda, Sunlite and CST are not meaningfully different from house brands. Schrader is the common valve on these bikes. Because a 4-inch tube holds a lot of air at low pressure, pinch flats from running too soft are the usual cause of death, so check pressure weekly and carry a spare on long rides.

Best for: 26x4 fat-tire e-bikes · Spares for the trail bag or garage · Riders replacing a pinch-flatted tube

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E-Bike TiresFeatured

Kenda Krusade Sport 20x4.0 Fat Tire

The Kenda Krusade is one of the most common 20x4 tires on folding fat e-bikes, which makes it both a like-for-like replacement and an easy place to start when the stock tire wears out. It is a street-leaning tread with a shallow center and small side knobs, so it rolls quietly on pavement and still grips on packed gravel. Kenda sells versions with a puncture-resistant layer; look for that on the listing if flats are your problem. It is a wire-bead tire, so it will not fold for storage, and it is heavy like every 4-inch tire.

Best for: Folding fat e-bikes (Lectric XP, Heybike, Engwe and similar 20x4 bikes) · Mostly paved riding with some trail · Riders replacing a worn stock 20x4 tire

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Fenders

26x4 Fat Tire Fender Set, Front and Rear (generic)

Full-size fat e-bikes on 26x4 tires need fenders at least 4.5 inches wide, and the sets sold for them are wide alloy or plastic guards with adjustable stays and, usually, a bracket for a rack tail light. Universal sets fit most rigid and hardtail fat bikes with eyelets, but suspension forks and frames without eyelets need clamp-style stays or a model-specific set. Alloy fenders rattle less and survive better than plastic. Installation takes an hour the first time; take the time to set stays so the fender does not rub the tire under load.

Best for: 26x4 fat e-bikes ridden in rain or mud · Commuters who want full coverage rather than clip-on guards · Replacing worn or bent OEM fenders

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