Reaming 27.0 - 27.2mm Seat Tube

[claret73]

So, the spec sheet in the '94 Rocky Mountain catalogue states 27.2mm seatpost requirement. Got one but it doesn't fit. I've been told 27.0 is the Blizzard size, so should I ream the seat tube 0.2mm? I did this on my Lobster (Good Job I have a Spare). Any implications? 0.2mm is dust not heaps of metal...

I need to get the calipers on it again to check it's not 26.8mm. Really want to use the 27.2 as it fits with the rest of the CockPit parts but not if it's detriment to the frame.

 

[silverclaws]

Sandpaper the seat post and keep trying to fit, as soon as it fits stop sand papering. Personally something disposable like a seat post get's the treatment, not the frame.

 

[claret73]

With you, except the seatpost is Black & not sure of height...I'll hang on & get the diameter measurement right...

 

[silverclaws]

With you, except the seatpost is Black & not sure of height...I'll hang on & get the diameter measurement right...

That would make sense.

 

[tintin40]

Shim it. I bought a shim in brass which is 0.002 from a modeling hobby e-bay seller.
I have a plastic shim the same just in case.

Plenty different sizes on the bay

 

[poweredbypies]

Shim it. I bought a shim in brass which is 0.002 from a modeling hobby e-bay seller.
I have a plastic shim the same just in case.

Plenty different sizes on the bay

Shim it to make it smaller??? new one on me

 

[FluffyChicken]

Well it's 0.1mm of metal you're removing, anyway...
Ask the frame person doing your frame, they should be able to see if it doesn't damage anything.
I'd say if you want to and can, then go for it. It is 'suppose' to be 27.2 in the first place

 

[tintin40]

Shim it. I bought a shim in brass which is 0.002 from a modeling hobby e-bay seller.
I have a plastic shim the same just in case.

Plenty different sizes on the bay

Shim it to make it smaller??? new one on me

Now i know why i'm having problems with getting posts to fit

 

[unkleGsif]

Sandpaper the seat post and keep trying to fit, as soon as it fits stop sand papering. Personally something disposable like a seat post get's the treatment, not the frame.

Done this. 27mm to 26.8mm
10-15 minutes with some 800-1000grit wet and dry, wrapped around the post, up and down and in circular motions... ahem.... :shock: following a bit of careful measurement. Its a Thomson post that has that machined ribbing for grip inside the seat tube, so only needed to take off the very peaks of the ribs

My post is black too, and you would never know to look at

G

 

[Anthony]

It's not impossible that the catalogue is correct, but I should be very surprised. It has an Ultimate Ultralight frame, as did the 93 Equipe and I know for a fact that the 93 Equipe takes a 26.8 post. As does the 96 Blizzard. The external diameters of the seat tubes are the same, so for the 94 Blizzard to take a 0.4 bigger post, they must have specified a 0.2mm thinner gauge tube. It may not sound a lot, but that is basically reducing the weight and strength of the seat tube by c30% for 94, which is a lot, and then going back to the stronger tube by 96. Not impossible, but it would surprise me.

I would always make the seat post fit the frame, not change the frame to fit the seat post.