RADBMX.CO.UK
Technical & Reference Section => Tech and Restoration => Topic started by: spadey99 on December 28, 2013, 09:19 PM
-
Hi guys
having a mare finding a decent seatpost for my 82 pro star so what shim size would I need to convert ot 22.2mm so I can use normal bmx seatpost???
http://www.ebay.co.uk/itm/160879520092?var=460114003048&ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
Steve :daumenhoch:
-
That doesn't sound right. A Hutch Pro Star is the same frame as a Pro Racer. The only difference is the Pro Star came with all the Hutch goodies on it, like the Aero speed cranks, stem, bars etc....
It should be a 22.2mm post. They used thinner tubing to get the weight on the frame down so you should be able to fit a 22.4mm to 22.6mm post in it. Nothing as big as what you are trying to up size to.
-
This is what I have done to my supergoose, I've had 4 mongoose frames in total, all of them had slight crushing of the clamping area.
BITD as kids we didn't really notice or care and just crushed the clamps until the seat stopped moving and this is why most of them are split now, the seat post tube on a mongoose measures 22.6mm and a standard seat post is 22.2, 0.4 of a mm is enough to split or crush the key way when tightened
I bought a USE seat post shim from wiggle 25.4 and cut down the length so when fitted around the seat post it has a slit the same width as the key way in the frame when fitted, the shim is 0.4 mm.
2 of my mongooses also had slight weld showing through from the top tube inside the seat post tube,(worth checking on any frame) this would make a 22.2 fit tight in the tube but only in that raised area, the rest was loose so i carefully ground the high spot so the tube is the same all the way down.
Better than the coke can trick and it has a nice lip on the top so you don't loose it when fitting the post.
I fitted this because a hutch layback only comes in 22.2 or you can fit a hsin lung post like i have on my fatgoose (pictured below) which also come in 22.6mm standard
You require a digital vernier gauge to get it spot on though
From BITD if I remember some Redlines were supplied with a 22.2 seat post and a shim from new.
(http://i1293.photobucket.com/albums/b588/hooliganbbb72/IMG_8587_zps2406976e.jpg) (http://s1293.photobucket.com/user/hooliganbbb72/media/IMG_8587_zps2406976e.jpg.html)
(http://i1293.photobucket.com/albums/b588/hooliganbbb72/T2eC16RygE9s7HJFgBR9B-e1JvQ60_12_zps2c835405.jpg) (http://s1293.photobucket.com/user/hooliganbbb72/media/T2eC16RygE9s7HJFgBR9B-e1JvQ60_12_zps2c835405.jpg.html)
-
Hi mate
Pro star as in diamond back pre viper... not hutch sorry should have said.... ::)
-
Ah that makes sense now :LolLolLolLol:
I,ve used the same trick with the seat post shim. I hate knowing that it's in there but like snoopy72 said it is more important to prevent cracking.
-
Ah that makes sense now :LolLolLolLol:
I,ve used the same trick with the seat post shim. I hate knowing that it's in there but like snoopy72 said it is more important to prevent cracking.
You need to check this measurement especially if you have a creaking sound when out on a ride
-
Ok guys but what shim should I buy. .. what size would convert 24.8mm seatpost to 22.2mm :(
-
Ok guys but what shim should I buy. .. what size would convert 24.8mm seatpost to 22.2mm :(
Since the difference is 2.6mm, that would require a material thickness of 1.3mm
I'm pretty sure I used a 25mm to 22.2mm shim and it worked fine and I've built several Pro-Stars. :daumenhoch:
http://www.unicycle.uk.com/seatpost-shim-25-0-to-22-2mm.html
-
Cheers mate :D
-
Cheers mate :D
You can see some here https://www.facebook.com/groups/OSDBBMX/ :daumenhoch: