Tuesday, July 16, 2013

A2Z Components 68mm Post Adapter

Ok. So now I will finally shed some light on the utter ridiculousness that has become of my partybike build.  This started off as a pretty ridiculous idea and then due to a slight oversight on my part it went to ludicrous speed.

I was already required to do some weird adapting in order to get disc brakes mounted in the rear.  I found a pretty sweet period correct Manitou fork in great shape, titanium springs etc. on eBay and was able to snag it.  I was pretty pumped at how things were coming together and then I got the fork, installed it on the bike and then went to mount the brakes on the post mounts...

Disc brake standards have bounced around a bit, and suffered from some experimentation.  Especially back in the late 90's early 00's.  I knew there was some weirdness back then but I had forgotten about Manitou's random decision to make 68mm post mounts for a few years instead of the now standard 74mm that all brake calipers are machined to.  Go to mount the brake...6mm off. #sadtrombone


After a bit of internet'ing I found an adapter to get from the asinine 68mm to 51mm IS and go figure it was machine by the same folks who made the rear adapter I was using.  Long story short they were actually out of stock so the folks I ordered it from apparently had the same adapter made by A2Z components and shipped that one instead.

I was on my own with this adapter, no real instructions or description about its intended setup and things got a bit crazy pretty fast.  I don't have any calipers that mount directly to 51mm IS so I had to bolt an adapter to the adapter.  I'm not sure this is necessarily intended to be used this way.  If it was it would have been nice for them to machine in a bit more clearance in a few spots because stuff got REAL tight.  So tight that I had to get really weird.  Dremel tool weird.

We don't need no stinking clearance!

So in order for me to get the bottom bolt through to mount my second adapter to the 68mm post adapter I had to (in no particular order):

- Find a bolt to mount the 68mm adapter to the fork with the lowest profile head I could find.  The head on the standard brake mounting hardware was too big and would not let the second adapter sit low enough.  Luckily I found one at the local hardware store that bought me 1-2mm.

- Add an extra washer to the caliper mounting bolt on that side.  The standard bolt threads through the adapter just a hare so adding the washer makes the bolt not stick out and bought me another 1mm or so.

- It was still just a bit off so I had to literally Dremel metal off the 51mm IS adapter until it would sit low enough to allow that second bolt to thread through without cross threading.

- I then had to find another special bolt that was shorter so that it wouldn't stick through too far and hit the rotor on the other side.

It took a lot of troubleshooting but it all technically "fits" and feels solid (for the most part).  This setup requires you to increase the rotor size to make up the room added by the adapter.  So I had to purchase a 180mm rotor as well.  I now wish they made a 182 or 183mm rotor.

I would feel a tad better if this was grabbing just a bit more of this rotor.  But I don't weigh that much and its a 180mm rotor so braking power should be fine right?....RIGHT?!

I might try and mess with some more of those washers to see if I can get some better spacing but the shed was so hot and I had already poured so much time (and sweat) into this that as soon as I rode it around the yard and got it to successfully stop me I called it good for now.

I'll be honest, the sound of this brake 'working' is horrible.  Hard to explain in print but I'm sure anyone who rides probably knows what a horrible disc brake sounds like.  While it does stop me (on flat ground in my yard) I'm sure that the first thing going through my head at speed on an actual trail will be "I wonder if I'm about to die."  Initial testing will have to be done gingerly.

But thats it.  You could ride this thing.  You might not survive but you can ride it, go forward and then 'stop'...maybe.  Partybike doesn't really care about details like that, its mostly about the party.

Rock 'N Roll


  1. Great message. This article is really very interesting and informative. I think it would be useful for us. Thanks for sharing your good post.

  2. Anonymous7/28/2015

    Just encountered exactly the same problem, and sorted it out more or less the same as you - then I discovered your article! Good to know I'm not alone anyway... :-)


  4. Anonymous9/23/2015

    That yellow Manitou fork looks horribly familiar..., as does that 68mm post mount, arrrgh! Over the past few days I have been wrestling with the same issue, that is, trying to figure out how to mount a new disc brake onto my old, regular (non-party!) mountain bike, a 1999 Marin Wolf Ridge. Having searched the net your solution is about as good as it gets! I used to have Hope C2s front and back, but these were faff-tastic so I switched to V-brakes. Now (for vanity reasons!) I fancy some shiny new discs…, but proving very troublesome. I thought one easy improvement to your solution would be to just use an IS mount calliper and do-away with the 2nd adapter, but they seemingly (also) no longer exist (even on eBay). Another solution I am contemplating is using a Hope Post to Post Disc Brake Adapter (from CRC). This is a 74mm to 74mm “disc extender” adapter, but looking closely at it I think it might be possible to drill a new hole and convert it to a 68mm to 74mm adapter (an engineering drill would be useful for this!). I’m slightly concerned about structural integrity, but my guesstimate is that it would be okay; my other concern is what size disc I’d end up requiring…, tricky!!

    On a side note, I have just stripped down, cleaned and re-assembled my Manitou X-Vert E, although it is 16 yrs old it is still in perfect working order! Just a shame about the stupid 68mm mount!