30.8 dropper post

foo606

Hi all well a small problem is all dropper post seem to be 30.9 and I have 30.8 mm .Want a reverb stealth .
Will 30.9 fit at a push ?

foo606

27.2 and a shim may be my only way .

02gf74

Hmm that is unusual size.

How do you know for sure it is 30.8?

Have you tried a 30.9, obviously don't force it.

foo606

Yeah I bought a 30.8 carbon fibre seatpost
That was a tad tight used gripper paste .
The El chulo frame I bought has internal seatpost routing so seems odd that its 30.8 .However specs cannot be recovered as Planet x has pulled all the Chulo frames .
I seen one on Gumtree with a 30.9 dropper fitted kind of curious as to why add internal routing and be a 30.8 diameter seat tube .

foo606

Just looked up El Chulo frame on Planet x and states .Dropper stealth compatible .
The 30.8 carbon was tight .Without calipers I cant measure it exactly .Could the carbon seatpost have been 30.9 and not 30.8 ?

02gf74

OK, I did search and 30.8mm seatposts are common, who knew..... Everyday a school day.
.. And as already stated, 27.2 with adapter shim since 30.8 dropper do not exist.

steve_sordy

Another solution would be to ream out the seat tube from 30.8mm to 30.9mm.

This is only removing .05mm per side, which in £sd is less than 0.002" per side.

The problem will be getting access to a 30.9 mm reamer. But as it is a standard seat tube diameter, the bigger bike shops may already have one. The job should not take long, so it should be cheap to do.

If all else fails then get a 1-7/32" reamer. This may be easier to get hold of (we do live in the UK after all) and at 1.21875" or 30.956 mm is only slightly larger than the 30.9 you require, but is still only removing 0,056mm on diameter or 0.0022" per side.

Subsequently, your seat post clamp will deal with that quite easily.

My advice would be to go to a bike shop and just say: "My seat tube is a bit tight, will you ream it out please?" and see what they say.

02gf74

Good call re. Reamer but not cheap to buy, unlikely that lbs has such an item but if you live close to a frame builder, they may have one.

steve_sordy

02GF74 wrote:

Good call re. Reamer but not cheap to buy, unlikely that lbs has such an item but if you live close to a frame builder, they may have one.

I'm willing to make a small bet that just about every seat tube on a quality bike has been reamed. Hmmm, maybe not quality bikes then, maybe only the cheap ones?

foo606

States Stealth dropper compatible which is 30.9 . So was the technical section wrong .I measured my seattube with a tape measure 31mm or near as damn it .
Not sure what to do to be honest may purchase some calipers and measure it see what it really is .

02gf74

Tape measure is not accurate enough.
. Find a 30.9mn seatpost and see if it fits. It should not be loose but may need twisting nd little bit of persuasion but not forced.

steve_sordy

I agree with 02GF74, 30.9mm is only 0.004" bigger then 30.8mm, or 0.002" per side. Its curved so you won't even get a 0.002" feeler gauge in there. Either borrow a 30.9 mm dropper from someone, or find someone who knows how to use a pair of internal manual calipers.

The problem is that the top section of the seat tube has a slot in it. This allows the top to flex and appear larger. The slot is long enough that the section where the slot ends is several inches down the seat tube. A standard pair of internal vernier calipers will be useless to you, as the measuring tips are too short. You need a pair of internal manual calipers that look a bit like a compass, like these:
https://www.zoro.co.uk/shop/measuring-a ... _gQAvD_BwE

You use them and then measure across the tips. They take skill and practice to use.

The Rookie

The irony is that my Planet X frame has a seatpost tube that’s about 0.2mm oversize, they had an issue with creaking and just use to suggest people do up the clamp tighter, as I was using a 27.2 post anyway I just used a 31.8 shim in the ‘31.6’ frame.

steve_sordy

The Rookie wrote:

The irony is that my Planet X frame has a seatpost tube that’s about 0.2mm oversize, they had an issue with creaking and just use to suggest people do up the clamp tighter, as I was using a 27.2 post anyway I just used a 31.8 shim in the ‘31.6’ frame.

The problem is that just doing up the clamp tighter will knacker your dropper! The dropper has workings on the inside, stuff sliding up and down etc, valves and very fine clearances on components. Squeezing them all together will wear them out rapidly. You may get a warranty claim refused if they can detect the failure is due to overtight clamping.

I use Finish Line Fibergrip Assembly Gel to reduce the clamping forces I need. (And my seat tube and clamp are fine).

http://www.chainreactioncycles.com/fini ... rd|93292UK

foo606

Thanks for your replies some good ideas for me .The seatpost I have installed is 400mm in length and 30.8 in diameter .(supposedly ) However at the moment I installing the sram Gx. gears .So this will be solved before I hit the trails .
I do think I need to measure the diameter of the seat post thats installed at present before I think on what way I will proceed .And thanks again guys .

foo606

Measured seatube 31
2 mm .
So I guess 30.9 dropper post will fit .And yes used a digital micrometer .
But how do you set the height of the dropper so its not fully extended everytime its in use .

cooldad

It's supposed to be fully extended. Then you drop it when you you want it lower...

slc123

I have a Titus el Chulo frame exactly the same as yours and I fitted a 30.9 stealth dropper post and have run for 9 months with no issues.

foo606

Thanks Sic123. Yeah was kinda wondering as I bought a carbon seatpost 30.8 and fitted ok .Just wondered if one would fit before making the purchase .Now which dropper Hydraulic or cable .

slc123

I had a KS Cruxi dropper on mine, which I am actually now selling as going to be building another bike and the seat post sizes are different. Brand X droppers are great value for money... Haven't tried one myself but everyone that I know that has one really rates them.

foo606

Was looking at the Brand x dropper .
Need a 1x lever tho .
Wolftooth for sram should be fine .