Tandem Cycling - MTB Tandem Upgrade - questions (version 11)

For some reason the post below does not appear on the original post. I have no other option as to start a "new" post.

Firstly, Thanx for all the help.

Stapfam

I will have to go for Avid Juicy 7's. We do not have an agency for Hope disks in South Africia (my closest "civilised" country)

Also I am unclear as to what the mode of failure can be with a normal hollow Cromoly axle with a stressed skewer. Structurally this is a very sound union. Somebody mentioned the skewer might snap. The purpose of the skewer is surely only to keep the wheel in place. What extraneous forces are present???. The secondary purpose of the skewer is to act as a structural stiffener of the hollow axle thus further enhancing its soundness.

Has the failure of skewered axles with rotors large than 160-180mm been encountered before?? and documented explaining the cause or is this the manufacturers safeguarding themselves in a law suit crazy society???.

Big H

For some reason the post below does not appear on the original post. I have no other option as to start a "new" post.

Firstly, Thanx for all the help.

Stapfam

I will have to go for Avid Juicy 7's. We do not have an agency for Hope disks in South Africia (my closest "civilised" country)

Also I am unclear as to what the mode of failure can be with a normal hollow Cromoly axle with a stressed skewer. Structurally this is a very sound union. Somebody mentioned the skewer might snap. The purpose of the skewer is surely only to keep the wheel in place. What extraneous forces are present???. The secondary purpose of the skewer is to act as a structural stiffener of the hollow axle thus further enhancing its soundness.

Has the failure of skewered axles with rotors large than 160-180mm been encountered before?? and documented explaining the cause or is this the manufacturers safeguarding themselves in a law suit crazy society???.

Big H

Others will be able to provide the link but there is a risk that the wheel can be pulled out of the forks with the torque of a big disk brake and the position of the dropouts on some forks when a quick release is used. With a bolt through axle this problem does not exist.This has happened and design of fork dropouts- position of the caliper- size of the disc all come into it. This means that a conventional quick release must be really tight to stop this happening- hence causing a failure in some quick releases. I never had the wheel come out of any fork with disc brakes but I have snapped Quick release skewers by overtightening. My own experience with quick releases and other reports of wheel twisting out of dropouts, then the fact that we are now talking Tandems with more powerful brakes than most- means that I, along with many others, do not want to take a chance. There is also the situation where fork manufacturers have limited warranty to the size of the disc fitted on some of their models. I know that when I wanted to fit 200mm discs on my Marzochhis I contacted the Concessionaire and I was OK with the forks that I had, and that was with a quick release. The UK concessionaire would give me a good deal if I wanted to upgrade to bolt through axle- AND it was a very good deal.
Opened up a can of worms here, but others will be be able to confirm or contradict my thoughts on the subject.

On the Manufacturer of brakes- Avid make good brakes. Just get others to confirm that they are using Avids, and which model, on tandems and you will have no problems. In fact I am looking at Magura disc brakes for my solo, as there does appear to be some good deals around at present.

Thanx for the reply Stapfam, the snapping issue now makes sense. I have a Marzocchi Bomber fork. Do you mean they can be upgraded to 20mm bolt through???? What abot a conventional treaded Chromoly axle, something like the older bicycles had. In both cases, 20mm bolt through and treaded Chromoly axle I will have to upgrade the hub???
I am leaving to South AFrica through Zimbabwe tomorrow and eventually to Cape Town for the Cape ARGUS Cycling race on 12 March 2006. It will be a total journey of 7500km through AFrica for a race!!!!!!! I expect to spend some time in civilisation in local bike shops to see exactly what all this entails.

Two suggestions:

Read this thread: http://www.bikeforums.net/showthread.php?t=79230&highlight=disc+brake+fork+skewer

Send an Email to Alex@mtbtandems.com that describes your current fork/hub information, your team weight and riding style, and what your objective is with regard to adding disc brakes and see what he can offer in terms of recommendations. Given the nature of his business as a off-road tandem specialty dealer who deals with all of the current tandem-rated fork and disc manufacturers he'll be able to give you the current state of affairs on 9mm QR fork / disc compatibility.

Final note: Making the conversion from QR to bolt-on axles is not an inexpensive proposition in most cases unless you're lucky enough to have a fork that has replaceable drop-outs and one of the newer 20mm hubs from folks like White or Chris King that can also be fitted with a 9mm axle insert.

The Marzochhi forks can be upgraded to 20mm axle, but this does involve changing the lower legs.

QR's-- The case's of Wheels falling out cannot be ignored, but the incidents of this happening are few. What you have to do is look at how aggressive your riding and braking is. If you are at the extreme then think about changing to 20 mm. Most riders will not have a problem providing you take certain precautions. Really tighten that QR- make certain you have a good quality QR (I use XT now on the solos) and do not overtighten. If you really use force to tighten the QR-so that you almost have to use an extra lever to open it- then you are too tight. If you have an inkling that the rod of the QR is stretching- then you are overtightening. If on inspection you see a thin bit on the rod- then you are overtightening. If you see any damage- Don't use it.

I ride aggressively and I changed to 20mm but really changed to get a triple crown fork. Might aswell do both at the same time. BUT before I changed to 20mm- I used QR with no problems. Just a mental one that the problem may be there.

The idea of changing to a solid "Old school" bolt on axle seems a good idea to me. but will involve a hub rebuild to set up properly.