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Inner tube & tire alternatives for RW4

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As many others, my front tire inner tube exploded while parked under the sun for less than 30 mins.

Rad does not have stock on tires and inner tubes, so I am left without bike for the foreseeable future, which sucks.

I followed the advice of other posters here and on r/radpowerbikes and purchased motorbike inner tubes (Michelin Airstop Butyl 18ME for 9?).

They are significantly heavier (530g vs 290g of the stock ones) and are a good third larger, but they seem to fit, though I'd not inflate them past 20-25PSI.

I am also looking at the Kenda 2.75/3.00-18 TR4 inner tubes, and the Michelin 18 MC 2.50-18 in case they are lighter / narrower.

Unfortunately the explosion damaged the tire or was caused by a tore defect, so I'll be looking at a replacement for that, too.

Michelin City Pro / City Extra tires look extremely heavy (>6kg) based on somewhat unreliable data found online. Duro HF918 or similar also look heavy at 2.5kg.


Similarly to this post on reddit I've measured the tire width and shoulder height, and though I also don't have a caliper for very precise measurements, I get 75mm x 75mm, which roughly equates to a 70/100-18 or 80/90-18 or 80/100-18 or 3.00-18 or 2.75-18.

As a reminder, bicycle tires are measured differently than motorcycle ones, so RW4 tires are reported as 22"x3.0" but the bike wheel is actually a 18" one (as written on it as ETRTO 457mm-45mm or 18"-1.77").

The stock inner tube width measures 65mm or 2.55in when flat, so it looks like a 2.50-18 motorcycle inner tube would fit well, something like Michelin Airstop 18MC - 2.50x18. I purchased a Michelin Airstop 18ME and it fits well, but it's also relatively large at 90mm or 3.54in.

One additional point of info regarding the tire dimensions: looking at the image below the markings on the sidewall report it to be 76/100-457 M/C 43B MOPED.

76/100 means that the tire is 76mm wide and 76mm tall, consistent with my measurements.

457 is the rim size in mm, which amounts to 17.992" or simply 18".

M/C stands for MotorCycle (same as MOPED), to distinguish from other types of tire usage.

43B indicates the max weight and max speed, with "43" being 155kg, and B being 50 kmph / 31mph.

With the information above it's clear these are 3.00-18 motorcycle tires.

I found a close match to the spec at a very reasonable price (25?): CST C-916 3.00-18 TT 47P

TT stands for TubeType, as opposed to TubeLess, so it's designed to work with a inner tube.

The speed rating and weight rating are both higher (175kg - 150kmph/93mph), so I expect the tire to be heavier than the stock, but also more durable.

That picture of the tire looks like a perfect blend of smooth tread and the ability to be used on sand, gravel and even snow/slush. Good choice for the RW4.


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