Cyclocross Fork Chatter

Great minds think alike. Lennard Zinn just published a diagram of the causes and an article on the solutions to cyclocross bike fork chatter that looks very much like ours.

Giant TCX Cross Bike

You know how I was ranting about tapered cyclocross forks? Well, I tried one, and it wasn't half bad. In fact, it was mostly good. This thing was so stiff, it carved like a scalpel. I bet it could really rail a grass corner with the right set of tires at the right pressure.

Unfortunately, it had an integrated headset. The beating that a cyclocross fork takes on a jungle-cross course drive the bearings into the soft (relative) aluminum head tube, eventually yielding it, resulting in a throw away frame. For this reason, traditional headsets are the best choice for longevity since most of the stresses of riding are internal to the headset itself and when and if it fails, it can be replaced.

Other details about the Giant TCX cross bike that may be of interest to our readers:

• It came with Kenda Small Block 8 tires which seemed to work great during a limited ride


• All top tube cable routing


• A nice flat spot for easy shouldering

Of course, all that stiffness comes at a cost in the form of less compliance on rough terrain. Less compliance results in more bouncing which means lost energy. So, if you're used to riding hard and fast trails, this bike and fork would make an awesome rig. Roots rocks and other such things? Maybe steel with a traditional straight carbon fork.

BTW - this bike I rode had a ~60cm frame and the name Vanessa on the top tube. Vanessa, whoever she is, is a big girl.

Tapered Cross Forks

I noticed at a cross race this weekend, that Van Dessel is now making cross frames with a tapered head tube. Looks like a 1 1/8" bearing on the top and a 1 1/2" bearing on the bottom, as is becoming popular in pro level road race bikes and suspension forks. Although it may stiffen the front end of the bike and result in more precise steering, the improvement has to be negligible given the amount of lateral flex that results when 700c road wheels are ridden hard off road. Still, I haven't ridden one, so I can't say, but I'd like to know more. The Van Dessel fork must then be proprietary, because to my knowledge, no one else is doing this with their cross frames.

Photo stolen from http://www.vandesselsports.com/

Fork Chatter Solution Proven

nippleworks reader Matt from Vermont implemented one of our suggestions to minimize cross fork chatter and had good results. Read Matt's report here. Read our suggestions here.

Cross on.

Wireless Fetish

Why put a wireless cycle computer on a road bike? The front wheel doesn't move much in relation to the handlebars as on a suspended mountain bike, and the thin wire can't possibly weigh more than the battery required to run the transmitter. Trek is now integrating wireless transmitters into the forks of their road bikes. It seems wrong to have to use a screw driver to change the batteries on your bike. Bikes don't need batteries. However, Shimano seems to think so.

I do dig that Gary Fisher road bikes have fender mounts now...

And, what is this? A stealthy pie plate?

Lawyer Lips in the TDF

What's this? Do I see Lawyer Lips on the fork of Alberto Contador's Trek Madone? What's going to happen when the Mavic Neutral Support mechanic jumps out of his Saab estate car or off the back of his BMW GS bike, front wheel in hand, and kneels down to quickly change Contador's puncture just to find the wheel caught behind some stupid metal tabs? Lost seconds, that's what.

Cross bike fork chatter

Every year as cross season dawns, this subject becomes a major mailing list chatter. Why does my very expensive, carbon fiber, heavily engineered, modern cross fork chatter under braking load? Answer - it's an inherent flaw in the design of traditional cross bikes with cantilever brakes. Although cross season is a few months away, I've seen some traffic on the question, so I'll discuss it.
The diagram above shows what's going on when your braking with the front brake.

1) The brake cable comes under tension
2) The brake pads apply braking force to the rim
3) The ground applies backwards force to the tire
4) The fork deflects backwards
5) Fork deflection causes brake cable tension to increase
6) Brake pads apply more force to the rim

At this point, something has to give way:

a) The brake pads stop the wheel cold and you go over the handlebars
b) The ground gives way and you have a front wheel skid
c) The brake pads slip on the rim and the vicious cycle of (1 to 6 + c) repeats

The rapid repetition of that cycle is 'chatter'.

How do you solve it?

• Decrease free brake cable length by mounting the hanger on the fork (like older front suspension mountain bikes: http://www.sheldonbrown.com/harris/images/tektro1257.jpg
• Install linear pull brakes which don't promote this behavior: http://nippleworks.blogspot.com/2008/12/linear-pull-brakes-with-drop-bar-levers.html
• Monkey with toe-in and otherwise change the mechanical advantage of the brakes to minimize the effect
• Install a really compliant cable hanger to deflect under cable tension?
  
• Disc brakes?

Happy Remounting

Wacky Fork @ Cat's Hill

This is the first time I've ever seen a split carbon fork like this. Aerodynamics, light weight, vibration absorption? Reminds me of the new Ridley split fork. The Ridley fork is all about aerodynamics, I'm assuming this is about compliance and that the void in the fork may actually create extra drag.
Also of note, Chad Gerlach of TV fame was in the lead of the men's pro race for a while (guy leading in the picture above).

Niner W.F.O. 9

Besides forks, I also got to see what's hot in dual suspension 29ers at the Niner booth.  TheW.F.O. 9 is a 140 mm travel bike and according to a Niner representative, one of the only two 29ers to accept the HammerSchmidt internally geared crankset.  What makes compatibility difficult?  Besides some mounting tabs, the suspension linkages have to be arranged to make room for the unit and the suspension must also be optimized to work with the chain constantly in a granny gear position.  The suspension on the WFO. is unique in that the Constantly Varying Arc that the rear wheel travels on results in no chain growth after sag.  This improves power transmission through the chain during full use of the suspension travel range.  According to Niner, the dw-link suspension just can't handle it.  You'll also notice that the bike features a tapered head tube and this model has the longest travel fork available for 29'ers, a Marzocchi that was a collaboration between Niner and the Marzocchi company.

Niner Forks

Niner had a huge display of 29" mountain bike forks in their tent at Sea Otter both rigid and suspended.  What's big in big wheels?  Tapered steerer tubes.  Note the conical steer tubes in the three suspension forks in the picture below.
As dual suspension 29ers are being developed, people are taking them places the big wheel has never been before, like downhill courses.  The larger wheel is ideal for rolling over obstacles at high speed but larger frames and longer spokes suffer from a stiffness problem that makes steering under load less precise.  A larger lower headset bearing is one way to stiffen the front end assembly of a bike and not something that is necessarily needed for the XC designs that have so far dominated the 29er market.  What might go good on an XC 29er though, is a compliant carbon fork.  Check these babies out:

That first one on the left is colored 'Tang' and matches the paint job on my Niner MCR.  Not that I would replace the fork, I'm very happy with my Rock Shox REBA.  Speaking of rigid, check out this carbon shell saddle.

The rails are an integral part of the shell making this one light weight piece of gear.  It was, however, stiff as hell.  Most saddles form a sort of hammock because you have a flexible plastic and leather shell supported at the tip and tail by the rails.  This allows for flexure in the middle.  The carbon saddle was supported right in the middle and the shell was stiffer than usual.   On a hardtail MTB no less.  Most cyclists don't have a ton of extra cushion in that region but maybe some people like the pain?  It would be perfect for this Rabobank rider.

Update on the new Rigid Ritchey

Some new details have come to light regarding the rigid Rithcey fork blogged on 4/19.  Someone @ Ritchey marketing is checking in on nippleworks and let us know the following:

 "Hey this pictured fork is actually the new PRO Mountian Fork. It will be available in 26" and 29" wit ha 445 axle-crown for the 26" and 485 axle-crown for the 29". IT has a 50mm crown diameter, forged hollow crown for light weight and full carbon dropout and disc brake tab - Ritchey Marketing Coordinator "

The distinction there is that the new fork is of the PRO class and not the higher end, WCS class (for which they already have a product).  With full carbon dropouts and disc brake tabs though, the PRO model is going to be very competitive from a weight standpoint.  The rigid 29er fork market is really heating up with this new offering from Ritchey and the much publicized Niner carbon fork (to be blogged about soon).

Specialized Shock Fork Cutaway

This nifty shock fork cutaway was up on display in the Specialized booth @ Sea Otter. It's confidence inspiring to see a company that is proud of their product's internal design. It indicates they put some brains behind the function as well as the obviously visible form.

The reason I'm posting this picture is to highlight the yellow foam inner seal. While it may not be standard practice, or suggested by suspension manufacturers, I always store my MTB upside down (easily done if you hang it from hooks in the garage). This soaks the seal with oil and keeps it swollen, retaining oil and keeping out debris. I once met a mechanic who would oil the outer seal after every wash, for more or less the same effect. How much oil got down there, I don't know. However, it seems intuitive that you would want oil leaking out from the inside and not seeping in from the outside to keep the internals debris free (as long as you replace the oil at the suggested maintenance interval).

New Ritchey Rigid MTB Fork

Not even on their website, so you see it here first kids, the new Ritchey carbon mountain bike fork:

Right now, all they're advertising is this model which appears to meet the same needs but has a significantly more sculpted look and no claimed weight. I wonder if they'll come out with a 29er version where rigid forks are pretty common? I tried to get some facts from one of the ladies in the booth but she turned out to be PR and didn't know a ton of product detail. Friendly though.

My 'Roubaix' bike

In the wake of Sunday's Paris-Roubaix, much has been made in the popular cycling press about the equipment used to carry the riders over the very long and very rough course. In addition to travelling over many kilometers of cobbled road, the race can be wet, muddy and very hard on equipment and riders. James Huang and the gang at cyclingnews.com have published at least two reviews of Roubaix bikes. One before and one after the race. By the way, the manner in which the pro mechanics are setting up the race bikes totally validates my comments on equipment for the Boulder Roubaix (back in August of '08).

Anyway, on Sunday morning, I went out for a ride of my own on my custom steel creation and thought I'd share the technical specs with readers hungry to know what a local club pack rider is sporting this year.

Nothing but the best shock absorbing 25mm tires on box section, hand-laced aluminum rims.

Top tube cable routing - keeps cables clean and shifting performance high. If that finish gets nicked by a rock - just add more clear coat.

Lugged steal construction. Really absorbs the shock as I speed over the cobbles (or more likely, poorly paved mountain roads).

All new high tech Campagnolo Mirage 3x9 drive train. I've got more gears than Texas has steers.

Custom badging indicates that this is a special build.

Plenty of mud clearance between the Tektro brakes and Nashbar carbon cyclocross fork. The combo of the carbon fork and steel frame makes it pretty supple.

More clearance out back. I could suck a small animal through my spokes and keep on rocking.

There you have it folks. Don't tell the pro tour mechanics what I'm doing. Got to keep that competitive edge.

Gary Fisher's personal mtb

As seen on Gary's twitter page, here's his carbon fiber 29'er superfly with rare (in this country at least) Answer fork. I can't find that fork on the Answer-Manitou website, must be available only in Europe. It uses a linkage and shock assembly instead of a linear spring. Claimed weight is 1260 g which is significantly lighter than the 1698 g for my Rock Shox Reba. However, the price is $1000 which violates the liberal $/gram rule on road bike components.

Here's a link to the bike.


And here's a picture of the crazy fork:
Photo from http://mig-cycles.co.nz/products/offroad/suspension.html

What's 100 lawyers at the bottom of the ocean?

A good start.

Lawyer Tab Removal... A Pictorial

The fork

The tabs

The tools

The procedure

The end result

I took someone's front wheel off their bike the other day, beginning to spin the quick release, and was told - "Hey - you don't have to do that on my bike!". What a revelation. This bike was built pre lawyer tabs and removing the front wheel was as easy as flicking the brake release and opening the quick release lever. I was so used to unscrewing a quick release by now, I thought that's what they were for. No, they were meant to be quick releases. Read slowly, quick... release... If we wanted to spin things to remove them, we'd buy bottles of Michelob. Instead, we have invented bottle openers and speedy bra removal.

I think Ray Jardine wrote in one of his books (and I'm paraphrasing here) - don't be afraid to modify your stuff, void your warranties and remove labels. You're not as dumb as the lawyers who are involved in retail products think you are. That being said, Nippleworks claims no responsibility for someone who removes the tabs from their forks, then forgets to secure their quick release and actually loses it. Nor, are we advocating the removal of said tabs from a mountain bike, specifically one with a front disc brake. Read this article for an explanation of why that may be a bad idea. We're also not going to buy someone a new fork if they end up taking off their entire dropout, or a new eyeball if they put it out with a tool.

But, if you're mechanically inclined, and steady with a file or power tool (which for us comes from years of working on surgical instrument prototypes), give your bike all the functionality of a 1930 Campagnolo.