Stem replacement

[Shiv]

Hi, I recently bought a 2nd hand btwin rickrider 500s mtb. I need some help to work out correct size for new shorter stem. Would any of the markings on the current stem be compatible with the stem found on the decathlon site?

[richardfm]

Can you post a photo of the bike and it's current stem and provide a link to the Decathlon stem?

[Will]

There is only really two measurements you need to pay attention to: The fork steerer diameter and the handlebar diameter.

Fork steerers come in two sizes, 1" and 1 1/8".

Handlebars come in two sizes: 25.4mm and 31.8mm. The latter is often referred to as oversize. If you see a stem that says it is oversize and it does not state the diameter of the handlebar it fits, then it is 31.8mm. If you see a handlebar that is oversize then it is 31.8mm.

If you have a 1" fork steerer, but want to use a stem that is 1 1/8", then you can use an adapter. If you have handlebars that are 25.4mm, but want to use a stem that is designed for 31.8mm, then you can use an adapter. You can purchase the two adapters from Decathlon for £6.99.

Will

[Brucey]

25.4 mm and 31.8 mm are undoubtedly the most common sizes in use today but there were plenty of (mostly dropped) bars made with clamp diameters of 26.0 mm and 26.4 mm.

[gregoryoftours]

Hi, I recently bought a 2nd hand btwin rickrider 500s mtb. I need some help to work out correct size for new shorter stem. Would any of the markings on the current stem be compatible with the stem found on the decathlon site?

There is a 95% probability that you need a stem with 1 1/8" steerer clamp diameter and 31.8mm bar clamp diameter, and then whatever length/angle of rise would fit you better than what you have. That model of bike is of a level and an age that is very unlikely to be of any other size. To be re assured 100% duck into any bike shop including decathlon and have it confirmed.