Interaction of thru-axle dropouts and dummy axles

I've got a situation with the fit-up of some dummy axles and their apparent corresponding dropouts that I'd love to have the illuminati weigh in on. I've already contacted the major players contributing parts and tools to my scenario, but I'd like some fresh eyes on the caper.

I purchased the new all-in-one 15mm thru-axle front dropouts from Paragon (DR2056) and the custom DT thru-axle. I also purchased the modular Nova 12mm thru-axle rear (NOV_DROP_MSET_12D). Lastly, I purchased both indexed and non-indexed dummy axles from Anvil.

Here's the situation with fit-up: Out of the 4 dropouts, I can only get the non-threaded front to seat onto the indexed dummy axle. The all-in-one threaded side for the front doesn't have a counterbore to allow the full seating. On the rear, it seems the slot width isn't the same (narrower) than the spec for the dummy axle, so neither of them will seat.

Don at Anvil says that he was unaware of the new Paragon dropouts without the counterbore until I had linked it in my email query to him, and also that he can't vouch for anything Nova produces, but that his tools correspond to the same spec as that used by Paragon.

Fair enough, I can see myself swapping over to the Paragon rear dropouts (DR2065 plus inserts for DT thru-axles), a little more expensive, but likely worth it.

For the front, I had contemplated grinding the "nub" that would nest into the counterbore on a normal 15mm dropout, knowing that I'd negate any warranty claims. The shoulder slot for the hub would still be there. Any input on that plan?

Lastly, I'm concerned about having the aluminum dropout inserts in place when brazing up the dropouts on the dummy axles to the fork blades and chain/seat stays. I've done the modular sliding dropouts from Nova a couple times (NOV_DROP_115_SLR) and brazed them up without issue, figuring there was enough separation between the heating zone and the aluminum to be fine, but I'm not so sure about the Paragon rear dropouts. Any inout on that?

And if any one has any other input on indexing and brazing up thru-axle dropouts (pics appreciated!), I'm all ears.

Thanks!

Where to start.

You mention the aluminum inserts for the front drop outs. The front drop outs you referenced do not have the inserts and they are in fact threaded for the skewer and not the 22mm left threaded for aluminum inserts. Which drop outs are you using? The aluminum insert ones have a brass insert available which acts as a heatsink and is excellent for using during the fixturing process.

What is this counterbore you are talking about? The backside of any 15mm thru axle front drop out has a 3mm (0.118") deep slot in the backside which is for the axle of the hub. It should be 22mm (0.868") wide. If the indexed dummy axle does not key into the slot on the backside of the drop out then measure the slot and measure the drop out. Which one is not on spec? Paragon is running on a +-0.005" on those two dimensions.

The rear spec that Paragon runs is on the loose end of the spectrum compared to the Shimano spec. If the Anvil is made to Paragon spec it is 0.790" slot for a 12mm thru axle hub. If the dummy axle is made for this it does not surprise me others do not fit. Shimano spec on a hub is 19.5mm +- 0.05mm which yields 0.7519" for the largest axle diameter. I made my drop outs to be 0.775" which would obviously not work on your mentioned product. Get the Paragon rear if you want to use that dummy axle.

Using thru axle drop outs requires a very good assembly. There is no fixing these set ups (except the ones that do allow you to fix it which opens up another can of worms IMO). Nothing worse than a thru axle bicycle that the skewer does not drop right thru and thread right in. Make sure you have a very good system.

-Drew

The front dropouts I have are the ones without the aluminum insert (DR2056) -- fully steel, but the threads go all the way through. The counterbore I'm talking about is on the threaded dropout, just a couple mm deep, before the threads start, on all the other DO's. Not on these.

The proximity of the aluminum was in regards to the rear dropout, but the same would go for the front. If using the heat sink on the Paragon front DO's that take the aluminum inserts, that would preclude using the dummy axle at all to braze them up.

Thanks for the info on the Paragon rear DO spec being "loose". That might explain why the

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Originally Posted by David Tollefson

The front dropouts I have are the ones without the aluminum insert (DR2056) -- fully steel, but the threads go all the way through. The counterbore I'm talking about is on the threaded dropout, just a couple mm deep, before the threads start, on all the other DO's. Not on these

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@David: Paragon's DR2056 is a fairly new part. If I am understanding correctly, the threaded side has the thread going all the way through unlike their DR2051 which has a step basically before the threads start? The small step on the ends of the Anvil indexed dummy will interfere with DR2056 (as you have found out) if I am reading that correctly hence the problem.

First we should alert Mark at Paragon of the interference issue.

Second would be to solve the problem on your end: Depending on how much thread is actually existing on that threaded DR2056 dropout and if you have the means to counterbore that 2-3mm deep step, you can add the step yourself. (If you can't or do not have the means, I can help you do it).

The other fix would be to remove the step from one of the sides of the dummy axle as you mentioned but I'm more of a mind to modify the part than the tool as the tool is the reference point.

If using Paragon's DR2051 (the front dropouts with the inserts), it is advisable to use the heat sinks and I would use a dummy axle when welding/brazing them to keep things in phase and do not remove the heatsinks and dummy axle until things have fully cooled. The pair of heat sinks I received did not have the counterbored steps for Anvil's indexed dummy axle so I added those in addition to a through hole so I can use them with an Anvil Indexed and non-indexed 15mm dummy axle (the new ones appear to have a through hole, which mine did not). I can't imagine welding those particular dropouts without the heat sinks as you really have to have your heat management game on point to keep them round.

I have made forks with both drop outs and also the first ever thru axle version 1. All have had dimension changes and all have had a need for a different dummy axle. It is just part of the job. Tools always need modification to suit your needs. This is why I make almost all my own tools including my dummy axles.

The fixed thread drop out does not have enough thread to remove any and allow for a 15mm relief. The skewer is not made to use a relief either. The insert style drop outs where designed around suspension fork skewer dimensions but the new ones are much slimmer. Either way the dummy axle only needs the 15mm section to be turned down to the minor diameter of the 15mm thread and not completely removed. Also it is much smarter to modify the tool since it requires one effort instead of going ahead and changing every part you want to use. Fix the problem once not every time. Making modifications to tools is just the way it is. If you want to use both style drop outs it will ultimately require two dummy axles.