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Thread: VT Shim

  1. #1
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    VT Shim

    [SIZE=5]Fellow Vt riders that have opted to switch out the stock seatpost (w/ shim) for a fitted seatpost from Thomson etcc.. I am thinking of doing the same thing - but am wondering if anyone has experienced and negative effects, like seat tube deformity, flex etc... I mean Giant had the opportunity to make the seatube to fit without a shim if they wanted to, so WHY???... Just a thought, any input would be great.. [/SIZE]

  2. #2
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    The reason for the shim is simple....no matter how short the owner runs his post(how high), the shim insures that the proper overlap is still intact at this critical juncture for overall frame strength, as the post/shim is part of the overall design regarding strength. This fact is also the reason why Giant demands that if one goes to a 30.8(or 30.9) dia post, they MUST(at least if you want ot keep your warrenty valid) run a 410mm or longer length...since even if one runs extra post(say a racer that sometimes rides a smaller then called for frame and then runs lots of post and a longish stem to make it all work)length, they'd be hard pressed to run out of the required post/frame overlap.

    The larger dia seat tube is also stronger then a smaller dia, which is great for alum frames in general. The shim also makes possible the use of the more popular smaller dia posts in 25 and 27.2mm posts.

    Thats why.

  3. #3
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    Thank you for the very concise info. Do you own a VT? If so do you run it without a shim w/ the length you described in your response? Thanks

  4. #4
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    No, but I have 2 race spec NRS's which are the same size ST, shim, and such. One weighs a true 21.5lbs and uses the shim with a carbon 27.2 Alien post with a carbon Flite Evolution saddle(pic down under "NRS top tube durability" post). The other one is 24lbs (spec'd for Pisgah epics and such)and uses either a 30.8 Thomson 410mm(cut down to 385mm)or a 350mm 30.9mm carbon Syncros post. I'm not sweating the warrenty deal. I'm running both setups obviously, and personally I like not running the shim. First, its heavy at around 44gms(so this weight is added to your posts weight). 2nd, its not as strong as a longer bigger dia post IMHO. The bummer about the larger posts, is not many good light race type posts avail really. USE makes a lighter plastic shim, FWIW. Like 25-30gms.

    Heres the carbon 30.9 Syncros on my epic ride. Retails like $100. I snag'd this one recently on Ebay for $39.95 from a big power seller. I think is listed too cheap, as his other adds for the same post is $69. Weight is claimed at 200gms.


  5. #5
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    Hey thanks - sweet rides... I appreciate the advise - I as well will go for the wider diameter longer length vs the shim deal. Thanks for your time and input.

  6. #6
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    Mine's ok, never have any probs with it, no noise no worries. Just got to tight tight them up and align the channels of the shim to the frame and Bob's your uncle or is it Harry?

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    I am having a issue with my new '04 VT3

    My seat post keeps lowering over the course of a ride. I usually set it so that they 7 on the post is at the clamp, a hour or two later and it has dropped to the 8. Could that be shim releated?
    '93 DB Ascent HT, Manitou front shock, XT Der's, SRT500's, SS7 with 987's
    '04 Giant VT3, bone stock

  8. #8
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    Quote Originally Posted by lamrith
    I am having a issue with my new '04 VT3

    My seat post keeps lowering over the course of a ride. I usually set it so that they 7 on the post is at the clamp, a hour or two later and it has dropped to the 8. Could that be shim releated?

    I only experienced that on one occassion. Just as wannaberacer stated above, even when you think it is tight, increase the angle of the QR lever and twist the knob of the QR a few more times then close the lever. This prevented any more movement from my seat post. I have not paid attention whether I aligned the tabs of the seat tube and shim(as stated in the previous thread), but it makes sense. Try it all. Good Luck!

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    Being a former mechanic I know the QR is tight, in fact too tight to be honest. I seriously wory if I tighten it any more I might break the collar, QR or deform a shaft. I might take everything apart and see if maybe something is not lined up like mentioned.
    '93 DB Ascent HT, Manitou front shock, XT Der's, SRT500's, SS7 with 987's
    '04 Giant VT3, bone stock

  10. #10
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    Quote Originally Posted by Dirtman
    I only experienced that on one occassion. Just as wannaberacer stated above, even when you think it is tight, increase the angle of the QR lever and twist the knob of the QR a few more times then close the lever. This prevented any more movement from my seat post. I have not paid attention whether I aligned the tabs of the seat tube and shim(as stated in the previous thread), but it makes sense. Try it all. Good Luck!
    yeah, i found tightening the QR & lining up the shim properly managed to reduced movement and squeky noise that the post was making

    BUT i have given up with the stock set-up, i just can't get my seat low enuff for comfortable technical rides and steep downhills.... so i have order a Titec Knock Sooper... will report on how it turns out

  11. #11
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    Quote Originally Posted by Duckman
    The reason for the shim is simple....no matter how short the owner runs his post(how high), the shim insures that the proper overlap is still intact at this critical juncture for overall frame strength, as the post/shim is part of the overall design regarding strength. This fact is also the reason why Giant demands that if one goes to a 30.8(or 30.9) dia post, they MUST(at least if you want ot keep your warrenty valid) run a 410mm or longer length...since even if one runs extra post(say a racer that sometimes rides a smaller then called for frame and then runs lots of post and a longish stem to make it all work)length, they'd be hard pressed to run out of the required post/frame overlap.

    The larger dia seat tube is also stronger then a smaller dia, which is great for alum frames in general. The shim also makes possible the use of the more popular smaller dia posts in 25 and 27.2mm posts.

    Thats why.
    410? wow. I have a VT small frame and with a long seat post like that i can't adjust my rebound out very far as the seat post comes down below the rebound knob.

    Mine squeaks like crazy and would like to switch it out but haing no warranty kind of worries me.

    Any suggestions?

  12. #12
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    Quote Originally Posted by lamrith
    I am having a issue with my new '04 VT3

    My seat post keeps lowering over the course of a ride. I usually set it so that they 7 on the post is at the clamp, a hour or two later and it has dropped to the 8. Could that be shim releated?
    Yes, it is shim related. I went through the same thing w/ my VT2. The company authorized cure is to go to a standard clamp instead of the QR. Guess what? that doesn't work either!! This issue & the tires are the only flaws in a really great machine.

    As far as a real cure goes, change the post. I went to the 30.8 Thompson, but if the 30.9 posts will work - and everything I read in the forums say they do - then your choices are greatly expanded. Just watch your post length - the post has to extend to the bottom of the tube at minimum! And stay with aluminum, the few grams you save with carbon don't count for much on a 29-30 pound bike, but the strength does.

    After you get the change made, go out and ride. I'm writing this after 5 1/2 hours of hd trail riding today. The VT is great - I won't give mine up for any thing!!

    Best of luck,

    Dave

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    Well, been on vacation (san bike ) Now I am back, I just looked at my post/shim and it turns out that the shim was not lined up with the frame, so I will try that as my 1st fix. I was SURE it was the seat rails creaking, but I will check as you can't really tell when riding. I could pull up the nose of the seat and it would creak, then same thing when I pulled up on the rear, but that could have been the post also..
    '93 DB Ascent HT, Manitou front shock, XT Der's, SRT500's, SS7 with 987's
    '04 Giant VT3, bone stock

  14. #14
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    Well, I still have a creakin the seatpost/seat assembly. Not sure of it is the post or the rails of the seat that are doing it. I like the seat I have, but I might try swapping out the seat itself 1st to rule that out. If that does not do it then I will be getting a new post.

    I am riding a 20.5" and have post sticking out the bottom of the seat tube, do I will have to get a super long post to maintain the warranty?? Anyone know what length post the 20.5" uses stock??
    Last edited by lamrith; 07-18-2004 at 09:33 AM.
    '93 DB Ascent HT, Manitou front shock, XT Der's, SRT500's, SS7 with 987's
    '04 Giant VT3, bone stock

  15. #15
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    Dump it !

    Get rid of the stock post and shim garbage, and buy a Thom.son 30.8 or 30.9 post.

    You will never have any more problems with squeeks again, and the Thom.son will outlast you and the bike.


    R.

  16. #16
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    Thompson

    I had a ton of trouble on my VT1 using a carbon seatpost. It kept twisting and slipping off of jumps no matter how hard I tightened it.

    I switched to a Thompson 27.2 and kept the shim. It has not slipped yet and I have put it through hell. The Thompson has ridges on the post and this prevents the slippage.

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