Mountain Bike Tech Q&A with Lennard Zinn

Published October 30, 2009 03:33PM

Editor’s Note: This is the first of Lennard Zinn’s weekly tech Q&A’s on Singletrack.com. If you have a mountain bike tech question, send it straight to Zinn. Lennard is continuing to answer road bike (and some mountain bike) technical question in his weekly column on VeloNews.com, as well.

Dear Lennard,
Last year I purchased a new Trek Fuel EX8. The bike came equipped with Hayes HFX9 brakes. This is my first bike dealing with hydraulic brake systems. I’ve ridden motorcycles for years so I have no problems servicing my brakes. What has annoyed me is the brakes lever “feel” and travel. I’ve bled the system numerous times, front and rear, cut down lines to a reasonable length and still can’t get the brakes the way I would like them.

This may have something to do with “safety” issues so riders don’t endo from brakes biting hard. I like a firm lever and can’t get it.

I’ve been thinking of trying Avids but it would seem to me just because the lever has a dial to move pads closer to the rotor it’s still going to have a lever feel which can’t be firmed up?

I rode a friend’s bike last summer that had XT hydraulics and was impressed with the lever travel on his set up. I guess this is a long-winded way of getting to my question.

The stock Bontrager wheels on my bike are for six bolt rotors. I don’t want to spend more money on a wheel set to accommodate Shimano’s center lock design. In your opinion what rotor could you recommend to use with Shimano XTR calipers and levers? Or, as Shimano likes to always create systems for their components, do they not recommend using aftermarket rotors for Shimano brake systems?
Peter

Dear Peter,
I don’t think it matters. I think the braking performance will be indistinguishable between most common rotors.

I’ve used Avid and Hayes six-bolt rotors, as well as old Shimano six-bolt XT rotors, with XTR brakes on many setups over the years without problems. There was a time when the Avid rotors were slightly larger in diameter than the others for the same rated size, and they would drag in the crotch of the caliper, but I don’t think you’ll find that to be the case anymore.
Lennard

Dear Lennard,
I have a Pivot Mach 429er. Love it. I’ve had it 15 months now and the bearings in the BB are already shot (according to Pivot website it is a “92mm wide integrated BB with internal Shimano XTR bearings”). I’ve never wasted a BB that fast. I brought it into my shop. They pulled the cranks. Then tried to get the bearings out. No luck. So they called Park Tools. They said they don’t have a tool for it. Then they called Shimano.

The first tech rep had no idea about this BB. They finally got a tech rep on who did. That was when they learned that indeed there is a special tool for removing this BB. Although I was surprised that this BB was shot in such a short time (especially as compared to past bikes I’ve owned), I was even more surprised when my shop told me that the Shimano tech rep told them that this “special tool” to remove the BB still isn’t for sale on the open market!!

You’ve got to be kidding me. Fortunately Shimano is holding good on their 3-year warranty on the BB and sending a new one, and they are also sending the “special tool.” Is this common for a huge company like Shimano to not have such a tool readily available to their shops? And what about these bearings getting toasted so quickly? Is that just a downfall of this BB design? I ride a good amount, but no more than I have on other bikes and BB setups that lasted much longer.
Tom

Dear Tom,
No, it is not common for Shimano to not have a tool readily available to shops for its parts.

Dear Lennard,
Thank you for e-mailing me. I am sorry to hear that this customer has had this experience. I am glad Shimano is getting it taken care of.

Regarding the longevity part of the question, the BB is an XTR unit with the same exact bearings and seals as the thread-in version. It also has a 3-year warranty. We have sold thousands of frames with this system and we have only seen five warranties on the bottom bracket. This is way better results then the outboard bearing percentages. Shimano has confirmed that with their other 92mm BB customers they are seeing better then average longevity due to the better protection and support of the bearings within the frame. For this individual, I am going to guess that he just had a less-than-perfect bearing to start with.

Regarding removal, he is half right on the assessment of the situation. Shimano has just released the tool and it is hard to come by. However, it is actually very easy to remove the BB without the special tool. A basic punch will drive the BB right out. It will damage the resin cups, but these cups are not designed to really be removed, serviced and re-installed. If a bearing is bad, it is easier and relatively inexpensive to replace the BB. Even if the BB is out of warranty, we sell the replacement for about $40 MSRP. With the special tool, the BB comes out very cleanly, but if it is being replaced anyway, then it really does not matter if the resin cups sustain some damage.

As for Shimano with the special tools, I have had some frustrations with this over the years. We would rather have the tool readily available to our dealers, rather than instructing them to use a punch. Fortunately, this has been almost a non-issue (one of our riders has raced Lu Ruta and has continued with the same BB for two seasons — no other bearing on his bike has lasted that long). Shimano should have the tool in greater supply soon and we plan to offer it to our dealers when available.

I also want to add that Enduro is now offering a nice replacement ceramic BB. FSA has one as well and Race Face is working on a BB that will be available shortly.

Zinn’s regular column is devoted to addressing readers’ technical questions about mountain bikes, their care and feeding and how we as riders can use them as comfortably and efficiently as possible. Readers can send brief technical questions directly to Zinn.