Post to Post adapters for rear

muskimo

muskimo

Likes Bikes and Dirt
hi guys this might seem like a bit of a silly or NOOB question, though ill ask it anyway.

there are quite a number of bikes coming out this year and next that utalise a post mount caliper adapter. some of which are 6" standard some 8" for the 6" version i need an adapter. here is the tricky bit. with IS to POST adapters an 8" rear is the same as a 7" front and so on down the sizes 7" is 6" front etc. with POST to POST are the front the same as the rear?

some look like they are just spacing brackets 7". Though the 8" are off set. my understanding is that they would work as the frame post mount sets the angle of the adapter and/or the caliper and the adapter either spaces or spaces and offsets.

180mm post to post


183mm post to post


7" post to post


203mm post to post


203mm post to post


203mm post to post
 
muskimo

muskimo

Likes Bikes and Dirt
fantastic. i had a good feeling they were the same front and rear. as there was no real reason from a design point of view that the couldnt go front or rear. cheers
 
Landon

Landon

Likes Dirt
Rear Post Mount Frames

Yeah, both front and rear post mounts will naturally be the same if the caliper bolts straight on with the same size disc.

I think post mount frames are a good idea as it should result in manufacturers designing better and stiffer brake mounts on frames. Let's hope some of the lower end manufacturers who adopt the system have good quality control. At least with an IS mount, there's a certain degree of adjustability & facing that can be done to correct misalignment.

With the 180/185/7" adaptor types, a little weight might be saved by using the "spacing" type adaptors and a set of conical washers under the bolt heads to correct the inherent misalignment with the bolts. They generally put front calipers in a better, higher, position on a fork. All 203/8" post mount adaptors will be an offset type.
 
Reubs

Reubs

Likes Bikes and Dirt
Interesting comment, Landon. I feel the opposite and see post mount rear as being a bad thing (at least for the general masses). I've seen a few too many stripped out fork lowers to think that adding more threads to a frame is a good idea- unless its done in the way Turner have it set up on the new DHR with replaceable threaded inserts.
 
Landon

Landon

Likes Dirt
Stripped Post Mount Threads

Yeah, stripped threads are certainly an issue with the post mount system and angry mechanics. Possibly the best idea would be for a manufacturer to install a Heli-Coil system in frames, and forks from new. Shimano have been using this on their derailleurs for a few years now which is awesome. Giant also prepare the pivot bolts on their frames with steel Heli-Coil inserts which is freaking unreal. It's practically impossible to strip a Heli-Coil if it's installed correctly and used with a proper length bolt.
 
muskimo

muskimo

Likes Bikes and Dirt
how often do you strip threads? i think ive done one in the past 4 years.

stripping comes from rushing.
 
Reubs

Reubs

Likes Bikes and Dirt
Stripping does indeed come from rushing, but it also comes from cross-threading, damaged screw threads, bolts that are too short and sometimes even downright incompetance.

I didnt say I was the one doing the stripping, but I was the one who had to tell the bike's owner to not work on their own equipment and that they would need to purchase new lowers.

I havent seen the Giants but pre-installed helicoils are awesome. I tried to find a picture of the turner system. It is a round insert that slots into the side of the mount and the bolt screws into that forming a T shape. simple and elegant.
 
You must log in or register to reply here.
Top