Flat mount discs and steel chainstays

[suhacycles]

So, anyone here build any steel frames with Shimano's new flat mount disc brake standard? Wondering what kind of braze ons to use or holes to drill. I take it the holes are not threaded? Are the usual steel chainstays with 12-13 tips and socket style dropouts ok to use? Photos are always nice... =)

Thanks,
Hansen Su

[Broady]

The holes are clear and slotted a few mm with a threaded bolt going up into the caliper.

The only steel / Ti frames I've seen with flat mount are the type with a fully machined dropout like so:



I've knocked up a jig for this purpose but it hasn't been used yet.

[Broady]

Paragon are doing a Polydrop insert too:

[Albert S]

Allotec are offering a few different cast options from the Far East:

C64-l.jpg

Dropout(C64) - Allotec Co., Ltd.

[incepi]

This is what I am considering as a rear Flat Mount caliper mounting solution. Simple 5/8" OD tubes with slotted discs attached at either end. They can be brazed or welded. Steel, titanium, or aluminum. They can be cut to any length, as per Shimano specifications. The round tubes allow you to notch the chainstay with a 5/8" hole saw or end mill.

IMG_1080.jpgIMG_1081.jpgIMG_1082.jpg

[Broady]

Yep, that's pretty much my plan but was going to machine from one piece as opposed to the seperate pieces.

[incepi]

Yep, that's pretty much my plan but was going to machine from one piece as opposed to the seperate pieces.

A piece of 5/8" bar stock could hollowed out from one end and slotted at the other. You just have to make sure that the thickness of the slotted end is at least 10mm. You could use a spacer as well to get the right overall thickness so that you are in compliance with the Shimano specification.

[incepi]

I've knocked up a jig for this purpose but it hasn't been used yet.

How does your jig maintain the orientation of the slots? How does it keep them parallel?

[devlin]

^It swings off a dummy axle.

[Will Neide]

Aesthetically, I haven't seen an elegant integration of the flat mount on a steel or Ti frame....yet.

[Broady]

^It swings off a dummy axle.

Yep, mounts on an Anvil dummy axle, sits 29.5mm from the inside dropout face.

[Broady]

Aesthetically, I haven't seen an elegant integration of the flat mount on a steel or Ti frame....yet.

The Cannondale is my favourite thus far, albeit Alu.

[incepi]

[QUOTE=devlin;733126]^It swings off a dummy axle.[/QUOTE

Obviously it attaches to a dummy axle. I asked how it keeps the slots parallel. Something like this?IMG_1084.jpgIMG_1083.jpg

[incepi]

The Cannondale is my favourite thus far, albeit Alu.

I like the Cannondale solution as well. It does not disrupt the integrity of the chainstay. In my system, the small tubes could be notched, rather than the chainstay. The same is true for the idea Broady has mentioned.

[Broady]

My thinking was to mill the slots after welding. Just have a round hole on the boss so it stays true to the jig and then open them out when they were fitted in position.

[Mike Mcdermid]

My thinking was to mill the slots after welding. Just have a round hole on the boss so it stays true to the jig and then open them out when they were fitted in position.

Untitled.jpg

simple as

[incepi]

Flat tabs in the horizontal position could also work if the chainstay was bent to provide clearance. It might be useful to investigate variations on the old Hayes 22mm standard, to see what solutions were implemented for that system. It was very similar to Flat Mount.

[mmoore]

simple as

Good idea Mike, though im wondering how I could do that with aluminum without totally washing the brake mount off when welding it on.


Have the flat mount shimano calipers made it to market yet?

[devlin]

[QUOTE=incepi;733185]

^It swings off a dummy axle.[/QUOTE

Obviously it attaches to a dummy axle. I asked how it keeps the slots parallel. Something like this?IMG_1084.jpgIMG_1083.jpg

Ahhh....yes. Of course. My apologies. Good question.

[Mike Mcdermid]

Good idea Mike, though im wondering how I could do that with aluminum without totally washing the brake mount off when welding it on.


Have the flat mount shimano calipers made it to market yet?

spindle time is cheaper than fudge time that was the first iteration of how the new ones work and the idea you can use should you so wish ,that one is steel the aluminium ones you wouldnt bother welding em up its less faff to solid it then bore and mill and stub weld the ends

its machined on a lathe then milled ,obviously for custom guys you weld a dropout on, we actually turn a bobbin and machine the dropout and stem all in one hit