The Golden Wrench

A blog about bicycle repair and maintenance by the mechanics at Freewheel Bike.

Thursday, September 29, 2011


Thanks to David "The Main Event" Mainguy

New and Improved Midtown Rental Shop

Over the last month or so we've been re-vamping our rental shop at the Midtown Bike Center.

If you've used the shop in the past, you'll find double the amount of tools at every stand.

If you haven't used the shop, and don't know how it works, it's easy. $16/hour gets you a stand with all the tools you see in the picture, lubes, rags, degreasers, greasers, and use of the parts washer.

A person can use the rental shop any time we're open as long as there isn't class going on so it's not a bad idea to call ahead.

And speaking of classes, we have a variety of classes that cover everything from changing a flat to setting up and servicing your full suspension mountain bike.

Winter is coming up soon, and as those who ride know... Winter is the season of messy bikes. The salt and sand that they spread all over the roads gets all over your bike, and your bike hates it. Hates it bad.

One of the best way to make your bike feel better is to give it a shower. We've got an official Bike Shower that you can use for only $5. Spray off the gunk, wipe it down, lube it back up. It's like a spa for your overworked friend.

And lastly, if you're riding by and have a loose something or a maladjusted something else or even just a low tire; we've got a free stand in the front of the store with basic tools attached that anyone can use and pumps that pump up both kinds of tubes.

They Claim This Will Stop Brake Squeal...

I intend to find out and let you know.

Tuesday, September 20, 2011

Bring in your Fox FiT forks!

Here at Shockspital I finally got the chance last week to do a full overhaul on a Fox fork equipped with their new FiT cartridge damper. We haven't seen many of these come through for service yet because they're so new--Fox only starting putting FiT dampers in their 32mm forks in 2010. But if you're following Fox's recommended service intervals, those 2010 forks are due for some love.

But back to my story: At the Murphy Menace 50-mile MTB race that Freewheel sponsored at the end of August we gave away several fabulous door prizes. Among them were some gift certificates for a full suspension fork overhaul! One of these lucky winners brought in his Fox F-series FiT RLC for us to freshen up. Here is a shot of the FiT damper once we got everything apart:

The shorter gold rod on the left is the coupler that holds the bladder assembly together. Just to the right of that is the black bladder which allows for volume changes as the fork moves through its travel. Just under that is the compression piston and the shim stack which controls oil flow through said piston. On the right is a longer gold shaft which is part of the rebound assembly. But of course that's not all one big piece; here's the guts:

At the top right, sporting the pink glide ring, is the rebound piston. At top left is the adjuster which is the only part of this assembly which is visible from the outside of the fork (though typically it's mostly covered by the red rebound adjuster knob on the bottom of the fork leg). As you spin that knob it moves the threaded portion of the adjuster, which in turn pushes the small silver shaft up through the larger gold shaft. As you thread the adjuster further in it causes the needle on the opposite end of the shaft to close the central port of the rebound piston, which increases the rebound damping and causes the fork to rebound slower because of the restricted oil flow.

I'm not going to go into the procedure necessary to get this entire assembly back together with no air bubbles in it. I'm sure you can imagine. But that's one of the benefits of this closed-cartridge system: it's much better than an open-bath system at resisting cavitation and contamination, both of which affect the performance and longevity of your suspension components.

One important point here is that this fork was still performing fairly well. The damper was still in good shape and the oil was pretty clear. But now with fresh oil and new seals this fork should run smoothly all through next season, too. And by having his fork serviced before any major problems manifest, this customer is helping ensure that it will perform at its best for many seasons to come.

Friday, September 2, 2011

A tech bulletin from Trek regarding carbon assembly paste

Trek has recently learned that carbon paste (of any brand) can damage a carbon steerer.

With most parts, correct clamping prevents any relative motion between the parts.  For example, the  stem firmly clamps the handlebar and the frame firmly clamps the seatpost; there is no movement. In these cases, carbon paste performs the valuable function of reducing the amount of torque required to affect a solid attachment of the parts.

However, with a headset there is movement of the parts. In normal usage of a threadless headset there is some slight movement of the compression ring relative to the steerer. This movement occurs when you hit a bump or apply the front brake. Normally, the movement of the compression ring does not hurt the fork. However, if there is carbon paste between the compression ring and a carbon steerer, the paste works like an abrasive to remove carbon material from the steerer. If enough material is removed, this could lead to breakage of the steerer.

What Trek is doing

The Trek Owner’s Manual and Assembly instructions say this about assembling carbon parts:

The carbon part can be assembled in a clean, dry state. As an alternative, we recommend the following special carbon prep products:
  • Tacx carbon assembly compound
  • Fiber Grip™ carbon fi ber assembly gel from Finish Line
All Trek publications will be amended to say that carbon paste should never be applied to the steerer.

What you should do

Stop applying carbon paste to carbon steerers. Although it might seem possible to only apply paste under the stem where there is no movement of the clamp, we have seen that paste can migrate down the steerer. This might happen on its own, or through exchanging parts or positions of existing parts. In any case, we recommend avoiding any contact between carbon paste and any part of a carbon steerer. Instead, clean both the steerer and the compression ring with rubbing alcohol and a shop rag; clean until the rag shows no discoloration.

Educate your customers. If a customer brings in a bicycle with a carbon steerer, inspect the steerer and if necessary, clean it. Also please explain this information to the customer. Trek is committed to the safety of our riders, so if you find a steerer with significant scoring, please contact your Rep for a free replacement fork. You will be asked to follow normal procedures, and the jpeg image you submit must be reviewed by Trek before any further action can be taken.