Not being a mountain biker I never thought about through axles before reading this thread. I have done a little reading about them and they seem to be stronger and stiffer but with some possible weight penalty. Seems like a marginal design gain that requires a large new investment.

Through axles appeal to me but I am not a big weight weenie and it seems like a good idea to use the best technology to keep the wheels on the bike. It seems like tandems should move toward though axles but my investment in wheels and tandem frames will keep me using my adequate steel skewers for some time to come.

Now if I wanted the lightest tandem I would use Ti skewers and a cable shifting double chain ring.

Totally agree with what-I-got-is-what-I-got... for now.

Before studying up on this topic, I was all for the notion of using Ti skewers on our tandem. Afterward, no way. For starters, Ti is too elastic for very long skewers (145mm+ spacing) especially when using 5-6mm thick QRs. The head mechanic at my LBS (a shop heavily into mtn bike racing setups) demonstrated to me the diff between a long Ti QR vs a steel vs a 12mm Alum TA. Toss in disc brakes and the torque they impose on the dropouts is a major factor to stick with at least steel QRs.

Ti is a great material but my understanding is that no matter the alloy it is about twice as flexible as steel. In cases when the design is the same diameter rod as the steel version like skewers, square taper BB spindles and pedal axles it will flex about twice as much as the same size steel rod. I guess that applies to stretching a skewer as well.

I'm wondering if this result is reproducible on other tandems...

The other day I was curious about side-load flex and did a quick test of sorts in the parking lot after a ride. Standing beside our tandem I clipped in one foot on the captain cranks and applied a good amount of side load while observing frame, wheels and tires. To my surprise, the front wheel hub (White Industry Mi5) actually shifted in the dropouts to the point where the wheel rim now sat pressed against the rim brake pads. I reseated the front wheel in the fork dropouts, tightening the steel Salsa skewer as much as I dared with carbon dropouts (3T Rigida fork) and retested... same results from both sides of the tandem. Perhaps this is an issue with carbon vs metal dropouts?

A quick search online indicates this may be a known issue:
ie:
https://mmba.org/forum/viewtopic.php?f=11&t=124556
https://www.bikeradar.com/forums/view...396&p=18859891

I find it a bit scary to think side loading a tandem can actually shift a front wheel hub that seems to be installed with an adequate amount of quick release force. Although we may not ever load those forces in the same manner while riding the tandem, it does demonstrate some limits and potential for the problem to occur. Discussions in the links above indicate this slippage can happen under certain conditions, and on single bikes which have far less front end loads than tandems. This has me revisiting my curiosity of going with thru axles (fork & hub) instead of quick release. That change would obviously mean disc brake is the only option for the front.

So, I am curious if anyone else can reproduce this same type of hub/skewer slip with their QR setup engaged firmly?

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Dag nab it, not another winter rebuild project...

I dunno, but we were riding with a brand new disc-braked Erickson steel tandem a few years ago. Their rear popped completely out of the dropouts under hard braking. I never rode with them again, so don't know what they did about that. I can't get my front to move on its aluminum dropouts.

Guessing the axle end cap is not "textured" enough.

Consider the clamping force is responsible to clamp each dropout into the axle end cap and QR at two locations.

Tightest QR ever will not hold if the axle end cap is too smooth.

Our next tandems, either MTB, road or both will run a through axle in the rear.

Currently the Ventana ECDM runs a 20mm front axle. Rear wheel on both is typical QR. Both are fairly consistent, but will move (creep) at some miles.

PK

Agree about the need for "texture". The WI Mi5 is technically one of WI's mtn hubs and does have a good amount of texture on the facing. Likewise for the Salsa skewer.

As carbon dropout forks do not come with any torque setting (and near impossible to determine what a QR is producing) tightening force is just a best guess and hope you don't crush the tabs... something that would not happen with metal dropouts(but then other issues arise with bonding to carbon fork blades, etc). Anyway, just an observation while we have this 3T fork installed. Have not yet verified if the same occurs with our original ENVE fork but imagine it would be no different.

If it were me, a front wheel slipping would require attention. I am speculating to say this, but my idea if it were my own would be to drill two holes per dropout. Sizes at approx 1.5mm. These would be drilled straight and 180 apart based on the axle centerline. In these four holes I would bond with hysol 956 or known similar unfilled system (and certainly not aluminum filled such as JB weld or 934), two stainless steel trimmed spokes. The spokes will offer two protruding anchors for the QR only. 1.5 to 2mm should be fine. So each dropout side needs to remain flush or slightly recessed. The QR and QR nut will need to have 2mm holes or better yet a 2mm slot cut across the QR clamping face. Ensure the holes or slot are deep enough to allow the QR face to seat without bottoming the pins.

Done right this will help prevent major movements and provide a failsafe to retain the wheel.

PK

You've replaced "Lawyer Lips" with "Prosecutor Pins"! :-)

How would you get the right tension adjustment on the QR? You would be limited to 180 deg increments.
I also think the traditional style skewer with an internal cam (like shimano) clamp a lot better than the external cam ones that seem to be around a lot now.

Slot the QR handle for best position, double the number of slots on the QR nut.

Just an idea. If it seems to extreme for some, sorry. It is obvious the greatest load on a fork or frame is certainly not the drop out.

PK