Lighter, Stronger and tougher is what Truvativ had in mind when developing their OCT crank system
. Combining structural theory, finite element analysis, and extensive testing is how they made it happen.
Some of you might not know this, but Truvativ are leaders in the DH and FR market. They have approximately 65% of the bicycle market when it comes to cranksets on bikes that have over 130mm of travel. As you bring up the travel, the percentage gets stronger.
Truvativ is also one of the few bicycle component companies that forges many different types of alloy. They forge all three levels of really forgable high strength alloys in the market place today – e.g. AL-6061, AL-6066 and AL-7050.
Truvativ is also now doing 3D forging or OCT (Open Core Technology). OCT is a process whereby a single mass of AL-7050 premium alloy is pushed, pulled and squeezed into a hollow crank arm. Truvativ’s AL-7050 is 75% stronger than commonly used 6061. The process is exclusive to Truvativ and has been refined over the last year producing a robust process with great results.
It’s taken Truvativ a little bit of time to master this forging process, which is much harder to do with a hard alloy like AL-7050. OCT cranks were almost ready to be released last year. But having a high quality standard, a few niggling finishing issues forced Truvativ to push their release date. The main problem they were facing is finding a way to properly close/form the end or tip of the crank arm. To address this they had to optimize the shaping process and then use a softer piece of alloy (like 6066) at that area to hold the shape during the final forging. This way they are making sure that the area they are cutting and shaping the end is only 7050 while discarding the softer alloy.
Since the cranks are made from AL-7050, they don’t require the use of a pedal insert anymore.
The Mission was to design the lightest and strongest freeride crankset system on the planet. Not just the cranks, but the entire system including the spindle, BB, bearings, etc..
Obviously the first thing Truvativ focused on is reducing weigh. By going with OCT they were able to considerably reduce the weight of their crankset. Case in Point – right now Shimano Saints are the lightest freeride crankset weighing in at 1164 grams. The next target Truvativ had were the Race Face Diabolus crankset which weighs in at 1310 grams. These weighs are for the full system – e.g. double chainring, bashguard, and BB system.
The new Holzfeller OCT crankset system: 1124 grams. System includes the Howitzer Team BB and 22/32/bash ring setup. Not a huge weigh difference when compared to the Saint crankset, but every little bit counts!
Many of you are probably thinking that because the crankset is lighter, that they aren’t as strong as the Saint’s. Well Truvativ didn’t not sacrifice any strength/stiffness simply to save weight. During Truvativ’s Stiffness, Yield strength, Ultimate strength and Energy tests they found out that Saint cranks aren’t as strong as you might think. Before we go on, here is a little definition of Stiffness, Yield, Ultimate and Energy.
Stiffness: How much the crank will displace under a given load.
Yield: Increasing the stress above a certain limit will give rise to inelastic deformations, known as yielding. In other words, when the stress is removed, the strain does not return to zero (and the original shape is not fully restored) since some deformation has permanently set in. The stress level at which this occurs is referred to as the yield stress or yield point.
Ultimate: Max load that the crank arms took when it broke.
Energy: The area under load vs. displacement curve (i.e. graph) will give you the amount of Energy that was stored in the crankset.
Holzfeller OCT: **4043 lbs (went to the limit of the machine)
Race Face Diabolus: 3659 lbs (didn’t fail)
Shimano Saint: 2364 lbs (spline split)
**Just for comparison, 4043 lbs is approximately the weight of a Toyota Tacoma!!Stiffness Test:
Right side Arm
Holzfeller OCT: 741 lbs
Shimano Saint: 732 lbs
Race Face Diabolus: 654 lbs
Left side Arm
Race Face Diabolus: 496 lbs
Shimano Saint: 482 lbs
Holzfeller OCT: 469 lbs
The new Holzfeller OCT system will be offered in 51mm, 56mm and 66mm chainline configurations. The Howitzer uses pretty burly purposed built bearings
– none of those tiny ISIS or Road BB bearings. The bearing carriers have larger and ticker races (both inner and outer) and the ball bearings themselves are bigger. Each using 8 seals – on the bearings, outside of the cup, and on the inside to keep everything sealed. I would like to point out that they aren’t really rebuildable sine the bearing is glued in the cup – that doesn’t stop you from cleaning and repacking the bearings with grease thought. CNC machined AL-6061 cups and chromoly spindle round out this stout BB.
The new Holzfeller OCT cranks will come in 175 or 170 (sorry no 165) and only comes in Mirror Black.Prices:
Truvativ Holzfeller OCT All-Mountain 2 ring config.: $235 USD
Truvativ Holzfeller OCT DH 1 ring config.: $225 USD
Truvativ Howitzer Team BB replacement: $47 USD
No real changes for the Hussefelt cranks other than a new color called “Gang Green”. Pretty cool color – different than gloss/blast black.
Ahhh…it’s hard to honestly give performance impressions of a Crankset that you’ve only ridden twice. But hey, they were stiff, didn’t bend, didn’t come loose, didn’t cause any chain deflection and didn’t creak – so I guess that’s a good start! One other thing going for the new Holzfeller OCT crank system is that they look pretty damn nice all dressed up in high gloss back and branded with etched logos.
I should be getting a set soon for evaluation. That’s when I’ll be able to give more accurate impressions and also comment on how easy/hard they are to setup, what kind of maintenance they require (if any), compatibility with chainguides and how they hold up on the long run – which I think are all very important things to consider when shopping for a new crankset system.
If you want to see the entire gallery CLICK HERE
2007 will be another exciting year for SRAM. Last year we saw the introduction of new X.0 componentry
, Air BoXXer, Carbon Juicy, and Truvativ Firex/Stylo and redesigned Holzfeller to name a few. This year is no different with a slew of new innovative components.
This was also my first time riding in Moab, but definitely not the last! I plan on going back there again as soon as possible – most likely later in the year when things cool down a bit. Even if the heats exceeded 100 degrees both days, it wasn’t that bad since it was a dry heat – way more bearable than humid heat! And I’ll take 100+ degree weather over rain any day ;o)
We stayed at the bike friendly Gonzo Inn
located in downtown Moab. He place was super nice, clean, had a pool and most importantly coffee 24-hours a day ;o) Also big thanks to Western Spirit Cycling Adventures for the shuttles
to and back from the trails. Kyle
, our shuttle driver, was super nice and modest. I got to ride Porcupine with Kyle, and let me tell you - he’s lethal on a bike! Excellent rider! If you’re thinking of doing a cycling vacation, I highly recommend that you check them out at www.westernspirit.com
as they offer killer guided bike trips that will suite you’re skill level.
A big thanks to the SRAM wrenches Pat and Jim who kept our bikes running smooth and problem free. They were also really helpful during the bike fitting sessions, helping us dial in the cockpit and suspension.
Last but not least - thanks to Eric Schutt for inviting me to the ride camp!