recombinant cruzLike

thadolius

New Member
This is a conversion of a conversion of a Next kid's 20" dual suspension 21-speed BMX bike.

The 1st conversion was a SWB modification with a front boom, crossover drive & sling seat on 1/2" EMT seat frame. Although it rode fairly well due to a step-up ratio on gthe crossover drive, the steering position was too "preying mantis" for real comfort. It is shown below.
 

thadolius

New Member
recombinant cruzLike [part 2]

Originally, I was planning to use the Cruzbike kit on the conversion of the 1st modification, but almost nothing fit without extensive rework or buying more conversion parts, so I just built it in the same style as a Cruzbike, chopping, splicing & welding. I did use the seat from the kit however & tried to copy most of the good geometry, like low seat height & TFT steering tube, from the Silvio. The URT was modified slightly (the original shock pivot was relocated for a better action line & moved to the front. This keeps the same brake, front derailleur, bottom bracket, crank, rear derailleur & drive wheel mounting as the original bike.

The only parts of the original frame remaining are the steering tube & downtube. Since it is all steel, the thing weighs 42# as you see here. Wheelbase is 46.5" & the seat angle is about 40 degrees unloaded. The Cloud 9 shock is very nice, being supremely adjustable, but is probably worth more than the rest of the bike.

I tried to keep similar steering geometry to the original bike. The pivot points on the URT are mounted forward enough that when adjusted to my x-seam, the wheel centerline is close to passing through the fork pivot axis. This keeps the steering effort reasonably light, as the trail is close to original. The fork has a couple of 3/8" flat washers tack welded on both sides of the dropouts to fit the pivot bolts through. The handlebar is the original steel one from Next, but I found a pair of MTB bar ends that I've mounted the brake & shifter levers to. This gives an adequate knee room tunnel, but still with a low enough bar height to see over. Further, the bar is far enough away for good comfort and steering leverage.

Interestingly, the bike rides quite well -- much better than I thought it would. Unfortunately, since I'm about 210#, the front fork is collapsed onto the inner bump stops most of the time yielding limited front suspension travel. This may change as the weather gets colder & the elastomers get stiffer. Due to the 20" wheels, I'm always in the big ring up front & the top 3 cogs in the back most of the time, even with 160mm cranks. I run 20 x 2.1 Maxis Hookworms on 406 rims at 90psi, even though the sidewalls say 116 max. They are quiet & almost bulletproof for commuting, until the tread gets too thin.

The handling is very nice also. Even with heavy steering, the thing feels very responsive to steering inputs to avoid potholes & road debris while in traffic. I originally tried the forks reversed, but like the standard position better. It seems as if I'm less cramped & the bike handles better (overall road feel). Although the riding position is not ideal, it is very comfortable & seems quite aerodynamic. I don't have a cyclecomputer on it yet, but it seems pretty efficient.

I originally built this since I was saving up for a Silvio & didn't know how long it was going to take. I may build a tilting trike rear end for this & use it for winter commuting. I'll post weight distribution info later.
 
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