Trail numbers in 14" kids bike

[Daniel_Y]

@BS_Industries

When designing kids bikes (and adult bikes), I find it helpful to compare geometry of different frame sizes through ratios. For instance, look at the ratio of trail to wheelbase as compared to your preferred geometry and size to get a better understanding of how the handling will compare.

Thanks for that, I never thought of relating trail to the wheelbase, but it makes a lot of sense:

• Trail is a lever used to “move” your wheelbase

@Brad

They have a big name 12” strider bike with a lot of offset and 71 HTA. I have not calculated trail. That bike is so awful handling they have struggled to get used to it. The front flops so badly that the whole bike falls over with little steering input. It’s so bad that I had to make a rubber steering damper inside the head tube to make the bike rideable.

I have always wondered why my niece and nephews bikes looked so unstable. I always assumed it was pilot error

Here is an estimate with 71HTA and 30mm offset fork. I have no idea of the real diameter of a 12" tire.

FYI, @BS_industries does these sorts of bikes professionally. There is some great info on kids bikes in their thread:

BS Bikes Build Log

My first bike design just hit shop floors: I spent the last few years managing and designing products at Strider bikes, the 20X was my final project at the company. I learned a ton developing the geometry and fit for this bike, it was designed using anthropometric data to drive fit. The bottom of the adjustment range is a median sized 8 year old and the top of the range is median sized middle aged woman. The fit worked surprisingly well for the entire range of users with the only adjustabi…