Formula (FS) to Post mount disc brake adapter

[Pionir]

I've seen the thread on the custom FS to IS adapter group buy, but I was wondering if anyone does a straight FS to Post mount adapter which I reckon would be much stronger.

 

[Pionir]

I've also just emailed this chap in Germany who supposedly makes adapters. They're a slightly different (better?) design - it bolts onto the inside of the tabs and is a Z profile to allow an IS adapter or caliper to be fitted without spacers.

http://waldmeissler.de/fahrradteile-bremsadapter.html



Not too dissimilar from the original Magura adapter

 

[Pionir]

So i'm going to try and make (or rather get made by a friend) a straight FS to Post mount adapter rather than mess around with the hammerhead adapter and spacers. Hopefully it'll be quite simple as it should just be a rectangular plate with 4 holes drilled and some bits cut out.

I've worked out the dimensions starting from the FS -> IS .dxf file for the hammerhead adapter off the facebook post facebook post and superimposed/rotated IS and PM dimensions on it to fit

I'll report back if successful, but if anyone else wants to have at stab it, below is what I've worked out. I've sanity checked it with measurements from my fork and it looks in the right ball park. There isn't much clearance at the lower tab, so some filing may be required.

It's not the most elegant shape but it should allow everything to fit (fingers crossed)

Oh and it's based around a 160mm disc

The dxf is available on my Dropbox

 

[Dtowntx]

Re: FS to Post Mount

Did you ever finish the adapter? I tried to download the dxf but it did not let me

 

[Pionir]

Funnily enough it just arrived in the post this morning from a friend who kindly made it for me.

The dimensions seem correct and the pad touches the 160mm disk properly so I'm happy to say it fits! It's a bit on the heavy side as it's quite chunky compared to the modern adapters, but as it does the job I'm happy.

 

[Dtowntx]

Re: FS to Post Mount

Do you know what material he used. Do you think it would lighting us is you removed some of the excess material looks great

 

[Pionir]

It's 10mm stainless plate and it's over-engineered for sure, so there's scope for saving a few grams with a bit of drillium here and there. I'm not too bothered about the weight so didn't go too deeply into trying to make it super light.

 

[Dtowntx]

Re: FS to Post Mount

Thank you for the dxf file. I am going to have one made out of 7075 T6 aluminum so it should be a little lighter. No fitment issues. Going to use shimano disc. What is the strap on the fork for.

 

[Pionir]

The P-clip is just for a mudguard so you can ignore that

If you have some adjustment from elongated holes in the caliper, you could actually use 10mm thick plate and drill the holes centrally. This is what is mine is because I couldn't get 12mm S/S plate

For example, there's a good 4mm of lateral play in the TRP Spyke that can be used to line it up with the disc - https://cdn.bike24.net/i/mb/8a/dd/08/22 ... 431456.jpg

 

[Dtowntx]

Re: FS to Post Mount

I only have access to 9.55mm - 3/8" and 12.55 1/2" aluminum. Would the 9.55mm be to thin?