Need advice - seatpost past minimum insert

[joseelias]

(Rant mode on)

Today I was reminded again why I hate so much going into Bike Shops these days. Went into one and asked if they had 27.0 seatposts and the imbecile behind the counter guaranteed me that 27.0 seatposts do not exist and that he knew because the shop has 20 years, bla, bla bla. Well not 20 years around here that's for sure...

After my insistence and after saying that Ritchey, BBB, Thomson and other brands have them he asked a colleague in the back of the store. He asked me who measured the seatube size in the frame, and when I answered "the frame manufacturer" he still didn't looked convinced. Then he finally said to the first guy that those seatposts do exist but it was necessary to be ordered. After this, the first guy basically shut down and when I said it was for a 1996 Kona the attitude was even worse. He basically shut down and ignored me!

None of them made an effort to check the availability on the brands they sell, prices or anything!

So, buying 27.0 seatposts may be easy in the UK, but it seems it's not only a more difficult task here it may make you feel like an outcast and slightly undesirable client! I already avoid another shop by their similar attitude. For those a client buying a square axle BB (that they do have on stock) almost isn't worth the hassle to look for it. I guess that if you're not buying a carbon 29er or flashing one you're like scum to these newer guys.

Luckily there's 40/50 year old store which has a great guy that may help me, but today it was closed. He even has an early 90's Peugeot/Grisley hanging on the wall in amazing condition with a RS Mag and I think I even saw it with a Tioga rear wheel sometime ago.

Sorry for the rant, but I really hope you guys get access to better stores than what I have access to.

(Rant mode off)

 

[joseelias]

@half cog and mynchiboy (and others too)
But if the bottom of the seatpost is under the bottom weld of the top tube, what difference does it make for it to be longer in terms of the frame?

Considering that the seat-stays support the backward movement of the seatpost (no matter the length), and the area of the seat-tube under the top-tube welds stops the movement of the bottom of the seatpost forward, what would be the advantage to have a longer post?

Unless the frame just under the top-tube is weaker than a lower part for supporting the pressure of the bottom of the seatpost, or it deforms a lot allowing for the seatpost to bend more than if it was inserted deeper even if it had the same exposed length, I'm having some trouble visualizing the reason why a longer seatpost offers an advantage for the frame.

These are honest questions. I'm just trying to understand the mechanics/physics of it.

As for my height I'm 1,85m (I guess +-6' 1") and my inseam 87cn (+-34.25").

I think I' have proportionally longer limbs (?). So I think my height may place me equally between a 19" and 20" frame but maybe my legs may really be better for a 20" frame?

@FluffyChicken
I understand what you're saying about the shims. They are short and unless the seat-tube barely extendeds the top-tube the bottom of the shim would not even reach the welds in the bottom of the top-tube.

**************

Here are some images of the bike with the 400mm post that snapped the clamp.

I beg the purists for clemency, but in my defense I've had to keep the bike functional since it's to only one I've owned in about 20 years.

 

[FluffyChicken]

Re:

Yes a 20" frame with them stats.

Having a real inseam of 34" myself, but only 5'10" my 20" frame is lovely to ride and so comfy. My 19" is a commuter and also fine, though not quite as comfy to ride ask have ridden it off road.

If I ride 18" frame I find them quite cramped and not as easy to ride as my larger frames.

Keep your eye out for a larger frame. The front on a 20" is much higher up too.

 

[joseelias]

Finding a frame like this one in size 20" in Portugal will be almost impossible. In the last years I've seen less than 10 Konas from the 90's on sale in the main site people sell here and they were all size 18". Recently I saw two Cinder cones and a Sex One or two. But few bikes are in comparable condition to mine.

Even from other brands it's very rare, and all asking two, three or four times the price people here say they pay for similar frames/bikes.

I still remember as if it was today when I went to order the frame and mention that I was i doubt if the best would be a size 19 or 20 and getting little to no help from the seller. Ended up choosing according an advice I read in a magazine that in doubt buy the smaller frame... Guess I choose wrong.

I'll manage for the time being and see what comes up.

 

[joseelias]

Just found this in a Kona Owners Manual. I think the manual is from 2016 which may invalidate the information regarding a 1996 frame, but it specifies that a seatpost minimum insertion should not exceed the top of the seat-tube. Anyway, several of the current Konas look a lot like the ones from the 90's.

It has been mentioned in this thread that the seat-tube extension is not considered structural. At least, by the time this manual was written it seems to be strong enough. But then again it may not apply to an older frame, especially aluminum.

"2. Step-through frame bicycles
Standover height does not apply to bicycles with step-through frames. Instead, the limiting dimension is determined by saddle height range. You must be able to adjust your saddle position as described in B without exceeding the limits set by the height of the top of the seat tube and the ”Minimum Insertion” or “Maximum Extension” mark on the seat post."

http://downloads.konaworld.com/docs/2K1 ... Manual.pdf

 

[cce]

Re:

Period correct or not, that's a good looking bike.

 

[joseelias]

Re: Re:

Period correct or not, that's a good looking bike.

Thanks!

I know it's not a top of the line bike, but it's common for people that entered more recently into MTB and barely seen a steel MTB to stare a little to it when we cross.

The only steel bicycles usually seen are the extremely cheap and in terrible condition ones used around, so when other riders see one that it's not totally wrecked and it actually looks like a proper MTB they tend to take a peek.

Plus a bike with the name Kona in the frame literally reads in Portuguese the exact same as if you'd have a bike named K*nt (yes that word) in an English speaking country. That may also attract some attention...

 

[Ian Raleigh]

Re:

What 'can' happen with a seat post when higher than the max limit marker!

Note the kinked section at the lug also the clamped section had cracked badly.

 

[joseelias]

@ Ian Raleigh

I see what you mean. At the moment the 350mm seatpost does not have the limit mark exposed, and goes about 1cm under the bottom of the top tube weld than on the first photos I've posted. Hopefully there will not be any problem until I buy a new one or repair the 400mm BBB I have.

Also, I have been looking at some photos from the late 90's to see for how long I may have used it before, and I think it was on the bike for about 2 or 3 years without damage to the seatpost or the frame. Later I've replaced it for a suspension seatpost from Rock Shox that had the dame length with same results.

Thankfully I do not detect anything like what you've shown in your photo.

 

[Ian Raleigh]

I see what you mean.

Glad you can spot kink in the metal :shock: As long as the seat post sits an inch below the lug/seat stays, the frame may never suffer from
any buckling, imagine the force implied by a very long seat post against a tiny bit of round metal, two parts may give eventually..

Bend the seat post or buckle the frame or even worst it snaps clean off, it has happened.

I purchased the bike because of the knackered seat tube extension, the frame was my size so I had it 'fixed'