Last August we bought a WOOM 4 to serve as a community bike to be shared by our 3 grandchildren as the grow into it. I did a thread covering the initial assembly and impressions HERE.

Several weeks back I ordered some upgrades.

The WOOM bikes as sold on Amazon have twist grip shifters by default. The one that came on the bike was stiff and imprecise. I ordered a SRAM X4 thumb shifter. This is what is available as an option if you buy directly from SCAM.



This required a change to 110mm grips.



I ordered a SRAM 4mm cable kit but it wasn't absolutely necessary. Since the ferrules that came with the kit fit the cable adjuster slightly better than the OEM cable housing, I went ahead and changed out the short section of the housing at the handlebars.


Since this would be the first bike with "gears" for the kids, I thought a derailleur protector would be prudent. I ordered a Sunlite derailleur protector.


And last but not least, our granddaughter wanted a mirror just like Poppie's bike, I ordered a Mirrycle MTB mirror.

Yesterday, it got warm enough to work in the garage comfortably W/O heat so I got to work.




First the order of business was to strip off the grip and twist shifter. (The Mirrycle mirror was borrowed from my bike to previously check compatibility with the bars)




The brake lever was removed to allow the SRAM X4 thumb shifter to slide onto the bars and then replaced.




Next, the grips were slid onto the bars with some soapy water as a lubricant. After making up a new piece of housing and routing the cable, the shifter was adjusted for flawless, easy shifting. The shiny new Mirrycle mirror was installed in the handle bar end.




IMO this is a huge improvement over the twist shifter. The SRAM uses thumb actuation for both up and down shifting and is much better for tiny fingers than a trigger shifter.



Finally, the Sunlite Derailleur guard was installed. It required a flat washer as a spacer under the bracket to allow clearance when the derailleur is in the smallest cog. Without the washer, the cage was just touching the derailleur.




There is yet one requirement left on the granddaughter's must have list. I need to order a side loading bottle cage. Thus one is available for $10 shipped on Amazon.

Looks great! We are searching for a WOOM 4 for our son - if you know of anyone selling or if for any reason you'd like to sell within the next couple of months I'd love to connect with you. (I know it's a long shot, but thought I might as well try). Hope the kiddos enjoy their upgraded bike!

Awesome! I didn't know you could put a thumb shifter on there, is he strong enough to shift gears with it? I might like to do that with my kid's Woom 4.

-MrScience101
Proud owner of a Woom 4 bike.

I need to upload some photos here, or make some measurements. But the new 8 speed thumb shifter is not moving the derailleur across the full distance from low to high gear (smallest to largest sprocket).

The limiter screws are fully screwed out, so no limiting happening.

is there such thing as an old sprocket that is wider than a modern 8 speed sprocket?

I have an early Woom 4, but not sure of the edition.

Any tips welcome, and I will upload a photo as soon as I can.

The derailleur seems too small for the block