Gt lightning seatpost size?

[daj]

Can anyone assist with what size a lightning seatpost should be? :? I thought and read (i thought i did) it was 27.2 but mine is bigger than that ... a 27.2 flaps around far to much :?

Cheers

 

[porkypaw]

Not sure about the Lightning, but recently purchased a new Avalanche frame, stated post size on spec is 27.2 and is way too slack.
I found 27.4 is a nice sliding fit, also had same issue a few years back with a Arrowhead, I think gt get carried away with the reamer now and again.

 

[SeeingisBelievingGTMuseum]

Having had more than a dozen in my hands over the past few years I can tell you that most of the 97's had 27.2's and most but not all of the 98's had 27.4's. It must have depended upon what seat tube material/size was available at the time of scheduled production. 98's had a Kalloy post with a Syncros style two bolt clamp in 27.4.

 

[daj]

Hmmm I have found something interesting, If you look on bikepedia for 1998 GT Lightining (same spec parts as mine originally came with) it states the seat post size to be 27.8 ?? :? Now this would make better sense as to why a 27.4 flaps around to much for my liking and actually pinches the seat tube when starting to tighten.

 

[SeeingisBelievingGTMuseum]

Daj if 27.4 is loose you must be missing the alloy insert collar that is usually in a Lightning frame seat tube?

 

[daj]

hmmm just had a look there isnt a sleeve or shim of any sort in there, just the collar?

Does that mean without this insert collar its 27.8 as bikepedia has stated or is that just wrong? I have ordered a USE shim in that size to try (only a £5 punt?) :?

 

[SeeingisBelievingGTMuseum]

Pull the black seat post collar off and see if there is a small allot ring around the top of the seat tube.
If not it's missing. I've never seen a Lightning without one.

 

[Alain C]

Hi RetroBikers !

Just have the same problem than daj...
As already discussed on FB with gm1230126, a seatpost in 27.2 flaps around too much and pinches the seat tube too much
I've purchased a USE shim post 27.2 to 27.8, and it doesn't work any more : I can't put more than 2-3 cm in the shim, as the seat tube was tapered !

I don't undarstand what the issue...
If someone have an advice !

 

[mk one]

Hi RetroBikers !

Just have the same problem than daj...
As already discussed on FB with gm1230126, a seatpost in 27.2 flaps around too much and pinches the seat tube too much
I've purchased a USE shim post 27.2 to 27.8, and it doesn't work any more : I can't put more than 2-3 cm in the shim, as the seat tube was tapered !

I don't undarstand what the issue...
If someone have an advice !

The post above states the frames came in 27.2 and 27.4, have you tried a 27.4 post?

 

[Alain C]

The post above states the frames came in 27.2 and 27.4, have you tried a 27.4 post?

Hi mkone,

I don't have a 27.4 in stock to test... :evil:

When looking inside the seat tube, I saw that the seat tube seems to be reinforced on the triple triangle zone. But don't understand why it seems to be tapered...

Here, some pictures :