Dually Travel Analysis

In developing the new Ahrens Austin dual-suspension design, I set out to achieve a few broad goals for the suspension system.


  1. Minimum rear wheel travel ~5.5" [140mm]
  2. Shortish chainstay length for good handling and climbing ~16.9" [429mm]
  3. Neutral BB height that's just tall enough to avoid cranks/pedals hitting the ground under full load ~13.5" [343mm]
  4. Rear axle path traveling upwards/rearwards for optimal traction
  5. Leverage ratio ~3:1 or less to minimize shock overloading
In analyzing and refining the design, it became apparent very quickly that achieving these goals would not be easy! But with some diligence and great 3D modeling software, pivot placement was continually tweaked until all of the original goals were met. Below is a graph which details only the swingarm motion (from zero to full-travel). It does not take into account front fork motion at this time.


1. The rear axle path moves in an upward/rearward fashion without any abrupt direction changes. Smooth travel upwards, smooth travel downwards with progressive damping in both directions - simple and effective.

2. As rear wheel travel increases, so does BB height and crankarm/pedal clearance. This trait is unique in that most frame designs exhibit the opposite; more travel typically yields lower BB height and less crankarm/pedal clearance. And since the front fork will ultimately be part of the overall system, the BB height should hover near 13.5" which has been my sweet spot for many years.

3. The leverage ratio on the rear shock is 2.97:1 which is acceptable for this frame style. The frame will accept shock lengths of 7.875" x 2.0" stroke and my plan is to offer both Fox RP23 or DHX 5.0 options depending on the application.

4. Chainstay length is fixed at 16.9" and with a concentric rear axle pivot, no chain growth can occur which means pedaling efficiency should be excellent. This setup also minimizes 'brake jack' to some extent although the ideal solution is a fully-floating setup which hasn't been designed yet!

5. Overall travel tops out almost 6" (151mm) which is a nice bonus since it's more than originally planned.

In summary, the main objectives listed above have all been met and in some cases exceeded. When I envision riding this bike, I want the suspension to do it's job in a clean, quiet and effective manner. This design will inspire confidence with its stout construction, lateral rigidity and frame geometry that's proven to handle well in a variety of terrains.


Where is the NC Dually?

This is an email I get about once a week....when are you building the 'NC Dually' prototype and 'when can I order one?' Well, that time is almost here. And we're not sure of the name yet...but we are sure that it will have AHRENS AUSTIN on the down tube. The AHRENS part is obvious but the AUSTIN is my business partner Brandt's middle name. Without Brandt, this bike project would have died off for sure and since he'll be fabricating these frames in-house, his name is on the bike too! Through continual brainstorming and countless hours of design time, our team effort will yield a unique trail bike that incorporates many of the ride characteristics my bikes are known for.

As I mentioned above, I've partnered with people that share my passion for design, manufacturing, metal working and process control. We've setup a new shop in Livermore, CA to streamline operations while keeping all frame building tasks under one roof including heat treating. Our new venture is called DEVISE SOLUTIONS and since I'm a partner in the new company, I have a vested interest in its success. This new company will ultimately handle day-to-day operations of Ahrens Bicycles by acting as a primary distribution channel for the brand. Over the last two years, the company has seen explosive growth and this strategy should enable the brand to grow more cohesively moving forward. And hopefully the economic situation will deliver a new influx of cyclists! We've invested in very accurate Anvil machinery for tube coping/mitering with a dedicated Cincinatti horizontal mill that's central to this operation and truly vintage. There's also a new Miller Dynasty 350 TIG welding machine on the floor, huge granite surface plates and also a programmable Despatch heat treating oven. I even scored a 36" wide HP Design Jet plotter last week for free which is a great tool for printing out 1:1 scaled drawings.

So back to the NC Dually project This bike will be hand-built at the new shop using a process that emphasizes quality every step of the way. We are working closely with our network of high-end machine shops to produce the CNC parts required for the new dually....and there are almost two dozen parts that need to get made! Needless to say there is still a bunch of work ahead of us but in the end it's all worth it. I dream about carving down coastal singletrack on a this highly-engineered, handmade machine that's been optimized for performance. The first frames I ever designed were duallies and I'm VERY EXCITED to get back to my roots with this project.

Here is a brief overview:

  • Constructed with 7005 aluminum alloy
  • Compatible with both 26" and 650B (27.5") wheel sizes
  • 150mm rear wheel travel achieved through modified four-bar linkage
  • Rear axle path moves in an upward/rearward direction
  • Zero chain/chainstay growth is achieved through 'Semi-URT' design
  • Low BB height also achieved through 'SEMI-URT' design (as rear wheel moves through its travel, the BB height increases for additional crankarm-to-ground clearance)
  • Concentric rear-axle pivot minimizes brake jack
  • Designed around Fox 15QR front fork in 140-150mm travel range
  • Compatible with Fox RP23 and Fox DHX 5.0 rear shocks (7.875" overall length and 2.25" stroke)
  • ISCG-05 mount comes standard
  • Shimano Direct-Mount front derailleur (uses ISCG-05 mount)
  • Front derailleur follows swingarm path for superior front shifting
  • Shimano Press-Fit Bottom Bracket shell > 92mm width
  • Shimano Press-Fit bearings used within Main Pivot housing
  • Rock Shox MAXLE 12mm bolt-thru rear axle system for superior stiffness
  • 135mm rear hub spacing
  • Rear 'international standard' disc mount
  • Hand-formed rectagnular chainstays maximize heel clearance
  • Front triangle has low standover height and low center of gravity
  • Widest bearing spacing possible at every pivot point; ENDURO MAX bearings used throughout
  • Interrupted seat tube enables rocker arm to pass through for shock acuation
  • Swingarm components easily serviceable
  • Replaceable rear derailleur hanger


Enjoy and if you've read this far, thank you!

Beer Logo Generator

My wife found this 'beer logo generator' on the web....click here to try it out for yourself!


Sliding Dropouts

Recently displayed at the Rocky Mountain Bicycle Show, this Chris Kopp townie prototype features Sliding Dropouts from Ahrens Bicycles....click here for more info.


More Biketoberfest

This was our first year at the Biketoberfest event in Fairfax and it was great. Perfect weather, relaxing atmosphere and of course lots of great beer and food. We built a new display stand to show off some bikes including an aluminum/carbon road bike as well as a brand new aluminum 'cross bike. The 'cross bike received the most attention....and we even met Gary Boulanger, US editor of Bike Radar - dope!

Here's a detailed picture of Brandt's new road bike. Built up with Dura Ace 7900 and Zipp 404 wheels, this high-end machine weighs in at just over 16 lbs - not bad for a 57cm frame size! The pics from Biketoberfest don't give this bike the justice it deserves...


Cross Pics

Here are some pics of local racer, Isaias Job, on his new 'cross bike. White sex all over the place on this baby!



Bikes and beer - my favorite! Come see Ahrens Bicycles at the 2008 Biketoberfest event in Marin on October 18th....we've even made a special batch of WiseCracker LITE openers for the event. Click on image below:


Off to Vegas

We're off to Vegas for the Interbike trade show and to experience the Outdoor Demo, see tons of bikes and enjoy the one and only Las Vegas. I'm especially curious about the 650B offerings since I've really been enjoying this wheel size on my mountain bike for this past year. Expect to see new 650B products from WTB, Kenda, Schwalbe, Kenda and more....even though some of these companies told me last year they weren't interested!

When we get back from the show, it's 110% effort on the NC DUALLY suspension bike project. All of the 'cross bikes have been assembled for this season and it's time to finalize the dually! Prototypes will be built this fall and then the real testing begins. Here's a preview of the design features:

  • Full 7005 aluminum construction front/rear triangles
  • Low standover height
  • Frames are mitered, welded, aligned and heat-treated under one roof
  • 26" and 650B wheel size compatibility
  • Zero chain growth for efficient pedaling
  • 150mm true rear wheel travel
  • Rear axle path travels upward/rearward for superior traction
  • Maxle 12mm thru-axle compatible swingarm
  • Intelligent cable routing
  • Sub-30lb complete bike


Gate Slammers Galore

Here are pics of a recent Gate Slammer frame built for Gilles in Switzerland. This is his THIRD Gate Slammer frame in three years and is ultra sick. Final weight 19.6lbs as shown with carbon everywhere...yum.


WiseCracker LITES are Coming!

After recent WiseCracker press in Mountain Flyer magazine and Cycling News, orders have been streaming in for the WiseCracker LITE. Weighing in at less than 16 grams, it's "worth it's weight in gold" according to one rider.

As a result of this peaked interest, we're in the process of machining a huge batch of parts.....the box below is packed full with over 1300 parts! The profile of each bottle opener is cut using a water jet at Aqua Jet in Livermore, CA. This method aims at minimizing waste during the machining process by 'nesting' as many parts as possible into one sheet of material. After water jet cutting, the parts are then tumble-deburred, hard anodized, laser marked and packaged for shipment.
If you've been thinking about ordering custom parts for your club, team or business, please contact 'mike@ahrensbicycles.com' for more info. Below is a sample produced for Charlie the BikeMonger, a single-speed shop in the UK.


CyclingNews Reviews WiseCracker LITE

Scroll down to the bottom....


And special thanks to James Huang for the hookup!



I'm so excited about the recent press Ahrens Bicycles has been receiving. Inside and outside the bike industry, people all over appreciate the benefits that only handmade frames can offer. I guess so many years of hard work are finally paying off!

San Francisco Chronicle
July 5, 2008

"Cyclists Favor Handmade Frames" article by Nancy Davis Kho
SF Gate Video Link


Mountain Flyer Magazine
Issue #9
"Understanding Aluminum" article by Mike Ahrens
Alcohauler Singlespeed Frame Review by Brian Riepe


Dirt Rag Magazine

Issue #135
Whole Shot Cyclocross Frameset by Shannon Mominee


BC Bike Race

My friend Steve Woo is racing the BC Bike Race....here's the first pic. Good luck Steve! Check out his website for race updates.


Speed of Light

Back in my days of designing fiber optic products, I worked with a firmware engineer named Min. We share a similar interest in cycling and late last year Min signed up for a new road frame. This project has taken many months to complete and the final results are gorgeous - thanks Min for being patient! Special thanks to Jason Grove (El Camino Fab) for building this beauty to exacting standards. And special thanks to Ryan Bontrager for assembling it overnight for me!

Frame Details:
Columbus Spirit Steel Tubeset
Paragon BB Shell
Breezer Dropouts
Finish by Cycle Fantasy

Build Kit:
Reynolds Ouzo Pro fork w/50mm rake
King headset of course
Reynolds Attack Carbon Clincher Wheelset
SRAM Rival drivetrain/brakes
FSA carbon bar/post
Ritchey 4-axis stem
Fizik saddle/bar tape
Michelin Pro3 tires

As shown 16.25lbs without pedals. Holy sh*t that's steel too!


BC Bike Race Entry Available

My friend, Steve Woo, has a team entry for the BC Bike Race available. Please see his message below:

I'm selling my entry into the BC Bike Race, the 7 day Mtn Bike Stage race (June 28-July 4) in beautiful British Columbia (Victoria - Whistler). This is one of the "Epic" endurance stage races as featured in the April 28th VeloNews. This one is different than the Cape Epic in that is much shorter, however, more technical terrain and single track (fun!). The trails and scenery are supposed to be spectacular. Check out the website.

[LINK: http://www.bcbikerace.com/] www.bcbikerace.com

The entry is $4000 for the 2 person team (includes food and accommodations). The race is sold out and limited to only 200 teams. If you're remotely interested please let me know ASAP.


.22 Caliber with Gold Package

If you live in Marin, keep an eye out for this raw beauty which weighs in at 22 lbs. Look quickly because the bike's owner, David, is one very fast rider and he's bound to blow by you...uphill or down! It's one sweet ride equipped with high-end components from Fox, Shimano, King, Hope, Kenda, Race Face and Thomson.


Hayes Bicycle Group Hardtail

Below are pics of the Hayes Bicycle Group showcase frame. It's built from tried-and-true Easton tubing and our custom dropouts and upper yoke. The frame will be outfitted with the latest components from HBG including Stroker brakes, Sun-Ringle wheels and Manitou R7 fork. Weighing in a 3.5 lbs, this race bike is sure to turn some heads. Special thanks to VC Graphix for the custom decals.


WiseCracker LITE Now Shipping

I now have inventory of the WiseCracker LITE bottle opener. This device fits onto any 1-1/8" threadless steer tube for a very clean installation. Unit price is $19 including domestic shipping via USPS. Preferred payment method is Pay Pal (mike@ahrensbicycles.com). Cheers!