Sunday, May 10, 2009

Kooka Cranks - The 'Exploded' View

Everyone has heard me harp and rail against Kooka Components. OK maybe not everyone, but the three of you new people following the blog, and the 4 people patient enough with me to still consider me their friend, and my family, of course, but they have to pay attention... OK, so maybe not so many people have heard me rail against Kooka before! Well, here's you chance to get up to speed. Take notes, there will be at test.

This crank set was on the old fleabay. As you can see, it's all pretty colors and woo! These are actually the second generation cranks, being different than the first generation by way of having a revised bottom bracket spindle mounting interface....in this case on the inside of the non-drive arm where the bottom bracket taper actually presses into the arm was beefed up in order to prevent the non-drive arms from continuing their very unfortunate design characteristic of dividing into two pieces at the bottom bracket spindle unexpectedly. You see, the first generation arms were so poorly conceived that they were the same exact arm side to side, just with a chain ring spider pressed on the drive arm. The drive arm was reinforced enough by the press fit spider to keep from splitting on a diagonal axis along the bottom bracket taper, but the non drive arm, lacking that reinforcement, split there with alarming regularity, almost as if perforated like an Elvis Presley postage stamp! Something had to be done, and hey, Race Face had the I-beam shape figured out, so surely the crack geniuses at Kooka could square it away without completely reinventing the wheel, right? Uhhh...

Moving on...On these second gen models, on both arms, the outside the 'I-beam' profile has been relieved to save weight, I guess to counter the weight gained by beefing up the inner taper area on the non-drive arm...probably in a lame attempt to keep the arm weight the same as the first generation cranks and thereby saving the company money on printing new product literature.




Here you see the backside of the drive arm, with the spider press fit over the bottom bracket taper area. Even with the reinforcement, this picture shows what looks like possible stress discoloration around the tapers. Save your receipt, buyer! The silver set screw on the lower left is a centering screw for the arm and spider assembly, nothing more.



This picture shows the beefed up non drive side arm taper area, about 2 mils or so thicker than the drive side, again because there's no spider on this arm to hold the taper area together and keep it from grenading into a billion little pieces. These arms proved to be marginally stronger than the first generation arms, but still feeble in comparison to Race Face Turbines. Also remember that the first generation arms were available in Cross Country style, 385gms with no rings, hogged out so much that the arms were almost too flexy to ride unless you were an 85lb girl, and 405gm Downhill style...Downhill! HA! Still, ANY improvement over first gen arms was welcome! The third gen arms went to a forged material rather than straight billet stock, and they were even more improved, but the bar had already been set so low that there wasn't anywhere to go but up, and by then the word was out and time was short for the little parts shop from Carson City.



The lesson here, with Kooka and with many boutique parts manufacturers from back in the day, is that there are many factors that go into manufacturing bike parts. Kooka believed somehow that their skill with a CNC mill and lathe meant that they didn't need to actually stress model any of their parts before release to the public, and that was surely their downfall. Were they pretty? You bet! Were they safe? Not on your life!

I remember when I first got my 385gm first gen cranks from Kooka, after meeting the fellas out in Vegas at Interbike. I put the arms on the Klein Rascal, and motored out in the parking lot. Something didn't feel quite right from the very start, as I could stand on the pedals, with the arms parallel to the ground, and bounce, and the cranks would flex so much that I could get the pedals to twist toward the ground about 15 degrees. I called Kooka right away and said there's no way these arms are safe, and they replied quite confidently that they'd never seen anything like what I was reporting in any of their product testing.

In their "product testing"...I'm sure they didn't...

I returned the 385 gm models and got the 405 gm Downhill arms. They lasted 4 months. Too bad really, as they sure were pretty.

4 comments:

Ryan Cork said...

Those original cnc'd Kookas are dangerous garbage as your asserting and it blows my mind that people are paying over $350.00 for sets on ebay.

Alas, the Canadian made(2nd generation) kooka cranks that I run on my MTB are cold forged from 7149-T7 alluminum. They're freaking light, freaking strong and freaking stiff. I'm actually adding a sick ass

FYI. It's very easy to identify the arms like I have as they say *Kooka forged* on all of em.

I wouldn't be caught dead running the original garbage Kooka cnc'd arms like you experienced(even if someone tried to pay me and film it on youtube) but the forged arms are amazing.

Anonymous said...

The difference between 1st generation and 2nd generation (all made in Carson City, NV) is that the 2nd gen were machined from forged blanks. NO 2nd gen ever broke (before the company sold and all production moved to Canada).

utahDOG! said...

First off, the "first gen" as you call them were revised many times prior to the change to forged material, as Kooka seemingly blundered in the dark to solve their embarrassingly poor design, using customers as test bunnies along the way.

Second, I've seen broken examples of many different Kooka arms, forged or not. No amount of convincing will make me change my opinion of Kooka. They are safe for use as doorstops and bookends only. Period.

Paul Ayoub said...

Hi ! I Bought my first used MTB in 1995 and it had the forged Kooka cranks on it. It was a Specialized M2 with Magura rim brakes. I ran these cranks through 3 frame sets and three sets of wheels and numerous parts. These cranks were the backbone of thousands of miles of bashing and rock hits here in the northeast USA. The ends of the arms were worn down from grinding agains rocks ....results of 2 decades of riding and racing. sold that Specialized M5 Hardtail finally in 2015 and those cranks spun true as the day I bought the bike 20 years ago !