BMX to MTB conversion - Redline Mini

When I was looking for a "real" kids bike about 5 years ago It came across a closeout sale on Redline Mini Pro LE BMX bike. I was light and equipped with good solid components.

As a kids bike for bike path riding it was awesome. So light and fast. The single speed rear hub with shimano compatible freehub meant I could easily change the gear ratios and get the gears right for the riding we did.

Unfortunately, the single speed held my kid back when we hit the single track. Its pretty much up or down where we live, so gears are all but essential. So with a bit of machining and tweaking I added gears .

After a while, the kids were getting faster and faster offroad and the small 20" wheels combined with the rigid front end were makings things hard through the rough stuff. I modified an old Manitou 26" fork to work with the 20" wheels .

I then removed the front triple chainring which was just really confusing for a young kid, added some lighter components I had lying round and settled on the current configuration that has seem many hundreds of happy single track kilometres ridden.

Components as at October 2012

  • Frame: Redline Proline Expert LE (Light Edition), 6061-T6 aluminium in candy apple red;
  • Fork: Manitou Sport modified to suit 20" wheels, custom made elastomers to suit 20-30kg rider;
  • Crankset: FMF 140mm square taper, 110mm BCD with 36t AC chainring;
  • Wheelset: Redline hubs, lightweight Sun ICI-1 rims, front radially laced;
  • Cassette: modified XT 9-speed cassette 17-32t 5 speed;
  • Gears: Deore 9-speed shifter with gear indicator, full length shift cable housing, XT rear derailleur;
  • Brakes: Promax levers, promax low profile v-brake rear, STX canti front;
  • Saddle: Odyssey junior - lightweight and perfect for those little backsides;
  • Pedals: Wellgo WR-1 - lightweight and grippy;
  • Chain: KMC 9-speed with quick link;

Some more pics:

From the back:

From the front:


BMXs although having very low stand over height are long in the top tube - even the mini/micro frames. For this reason I had to turn the offset seat post that the farm came with around so I could get the seat further forward. I also had to tilt the handlebars back to further shorten the cockpit. A zero offset post would be best for this application.

Related articles:

1 x 9 conversion

I was running a 2 x 9 setup on my daughter's bike with 36 and 24 front chainrings and a 7 speed 14-28 tooth rear cassette.

Missing link chain tool

Get a set of needle nose pliers and grind the ends thinner so they can fit between the chain side plates. Then add a curve to the inside of each jaw that matches the chain roller diameter.

Going 1x10 - the essentials

The key to getting the best out of your 1 x 10 setup is to have the right mix of components. Everything is a compromise and going 1 x 10 is no exception.

Racing BMX Tyres

This is just a quick round-up of tyres in the 20" x 1 3/8 size (451mm ERD) that may be suitable for kid's use for offroad riding (not BMX track racing).

Redline rigid 20" BMX forks

These have a brake mounting hole for a road type caliper.

Converting Jetblack Rocket front hub to 15mm

Quick facts: