[Closed] Small frame - Seat post- reverb quandary

This is because there is a slight narrowing inside the frame 6inches from the top where the first pivot is where its butted. So the guy in the shop cut the seat post.

i can only insert about 2 inches of seat post into the frame which i assume isn't enough. Will this damage the frame/post/me? Even if having only a bit of saddle inserted what if someone taller than me were to use it? They'd have no saddle in at all, bad news tall people.

I'm a bit confused, but I interpret the above to mean that you can slide your seatpost into the frame 6 inches w/o forcing it, and that the LBS cut off the seatpost which only leaves about 2 inches of it in the frame if you raise the saddle for a person taller than you. If that is correct, then...

Trek's website says that the Lush is a 31.6 dia seatpost (2012 model). If so, you may be able to get around the tubing butting issue by buying a 30.9 Reverb and shimming it in your frame. Shims are usually about 4 inches long. The 30.9 dia may then fit in the narrower butted area of the seat tube.

I'd certainly try a regular 30.9 seatpost and shim to be sure before I ordered the Reverb!

From what I've been able to find from some measurements [url= http://www.cambriabike.com/Rockshox-Reverb-Remote-Adjustable-Seatpost-Black-006815065130.asp ]here[/url] is the following:

For a 100mm drop Reverb the total length is either 355 or 420mm; so use the 355 version. It says that the minimum exposed post is 165mm which is the 100mm of drop + the seat clamp + the reverb's fixed collar that sticks out of the seat tube. So the maximum amount in the frame would be 190mm, and that would only be if your current saddle is at the Reverb min of 165mm.

What is the measurement from the top of your seat clamp to your saddle rails? Subtract that from 355 and that's how far the Reverb (or 30.9 seatpost) would have to go into your frame.

HTH...

JoeG that is an incredibly informative geeky and technical response with a cracking idea - top marks sir.

Email Treck about the problem of the narowing of the seat tube by the first pivot from the top of the seat tube, it my be a structural design and therefore a bad idea to ream the seat tube. If it is not structural then they may say go ahead with getting it reamed or help you out in some way.

Thanks, was thinking about a shim, but would only be able to go above the defect, not sure how long they are. Good idea about trying a narrower seat post, will be good to get an idea how narrow things are down there.

The discrepancy between the 6inches and 2inches is because i put the seat up and down during riding: not much seat post in when i'm on the road, but put it right down to go downhill.

I agree Rusty Mac I'm not keen on having it reamed, am also not keen on riding around with only 2 inches of seat post it!

Shims are generally about 10cm long, it would however be very easy to trim a shim down if it was too long.

Good idea and exactly what I'd have suggested but... Rock Shox clearly state in their bumpf that comes with the Reverb, NOT to shim it!

I suspect this is a downside to have a teeny tiny frame with a rocker on the seat-tube for which normally means some kind of intrusion into the seat-tube itself.

What you could do is look for a post with less drop (Joplin 3?) which also has lot of 'nothing' at the bottom of the post which would all you to cut it down to a size that could fit your frame.

I ride in the Peak district. A Joplin would last about 5 minutes in this wicked (god's own) mud. But good idea.

I've just replaced my Joplin with a Reverb and I rode that for 2 years in the mud and grit of Calderdale. OK, needed servicing now and again but I thought it was ok. Needed a remote version but it wasn't too bad. Get a Fox seal on it and I'm sure it'd last through some real abuse.

Either that or get the shorter of the two Reverbs and see if you can shorten the drop on it (sure I've read you can?) so it fits?

What's the minimum amount of Joplin that needs to go into the frame? Surely it must be more than 6 inches?

I think I'll get in contact with Trek, i'm worried riding about with such a small amount of post in the frame will damage it.

Surely this is a defective frame and should be replaced under warranty? IMHO by cutting the seatpost so that with the saddle at xc/road height there's only 2" of post inserted the shop have bodged it and it's now unsafe to ride in that condition. God knows you see enough cracked frames at the top tube junction as it is without putting the extra stress into it. If it were me I'd get onto Trek UK today and ask them about it.

Thanks. That's what i thought.

Unfortunately when i got the bike i wasn't as knowledgeable as i am now, and i think being a laydee doesn't help. I still feel pretty stupid when i go in there as they've done some more shoddy work since then. Now i do things myself or take it to a real bike shop.

Hum, think i have to go through the bike shop. Why didn't i buy it from a good bike shop?

Try these guys first see what they say - Trek UK - 01908 282626 (this number comes up on a previous thread on here - no idea if it actually works)

Good luck

I ride in the Peak district. A Joplin would last about 5 minutes in this wicked (god's own) mud. But good idea.

As a Peak riding Joplin owner I think you're giving Crank Bros too much credit there, it's more like 3 minutes. The other lads with their Reverbs have never touched them and they still work perfectly.

Riding with only 2 inches of seatpost in the frame is crazy. LBS that cut it should give you a new one (unless they warned about it but you insisted)!

If the frame allows for 6 inches of seatpost in the frame with no issue, then I hardly think that it is defective. You're just running into one of the compromises that need to be made in order to make a 14 inch full suspension frame with 5 inches of travel.

Again, how far is it from your saddle rails to the top of your seat clamp? That measurement will help a lot in determining what may work.

If the frame allows for 6 inches of seatpost in the frame with no issue, then I hardly think that it is defective. You're just running into one of the compromises that need to be made in order to make a 14 inch full suspension frame with 5 inches of travel.

Joe this is a mountain bike not a road bike therefore the seat needs to be adjustable over a range of 4 to 5 inches to accommodate climbing and sensible descending. At best 6" max insertion will give a 2" drop and that's not "fit for purpose". Sounds like the seat tube didn't get reamed after welding and it'd be a simple warranty job. Trek are pretty good on that front from what I hear.

Thanks for the advice.

Seat clamp to rails: 15 cm
Seat clamp top to first bit of trouble inside the tube 14cm.

Will go in tomorrow and see what they say, it's great to have a bit of stw knowledge before you go in, am really grateful.

You could go for a 27.2mm Gravity Dropper plus a shim. That'll fit past where your seat tube narrows and you can have 3" or 4" drop.

You need the exact post my OH has (but hers is 30.9) - KS i950R 300mm length with 75mm drop. Bottom of collar to rails is 150mm, bottom of collar to bottom of post 150mm. Can send you pics with measurements if you like?

Trek Fuel EX is the same.

Rubbish for normal seatposts but fine with a Reverb.

[i]You're just running into one of the compromises that need to be made in order to make a 14 inch full suspension frame with 5 inches of travel.
[/i]

+1

Seat clamp to rails: 15 cm

If that measurement is correct, then it is going to rule out the 100mm Reverb. You need 165mm to fit it, but only have 150. So unless you can come up with some sort of fix like a lower height saddle and/or thicker pedals, you can't fit the post that you are looking at.

I have a 125mm drop KS Lev, and it measures 185mm from the bottom of the collar to the saddle rails. Remove 25 mm from that and you're still looking at 160mm though. So its a little closer than the Reverb, but still not enough.

And it sounds like you're manually dropping your saddle somewhere in the 3.5 to 4 inch range, so you may not find a 75mm dropper post to be enough. Some posts may be able to have a spacer installed to reduce their travel (and therefore extended length), but I'm not aware of any myself.

Sorry!

Shims are generally about 10cm long, it would however be very easy to trim a shim down if it was too long

I wouldn't trim a shim on a whim...

DrP

Thanks for all your advice. Really helpful and i imagine i wont be the first person to having this problem.

The LBS were really helpful today, and agreed that the problem is (at least in part) due to the frame build itself rather than any imperfection inside the frame, so i imagine it is similar on Trek Fuels too. Will give trek a call to see if anyone else has had this problem yet. Fortunately i think i just have enough post in the frame given my weight. I accept some compromise is needed but on a bike that price it does seem a shame, it's not as if i'm riding to the shops and back.

LBS suggested an X-fusion 27.5 dropper post and shim it, which is possible as there is 15cm between the top of the post and the part of the frame that is narrow. This rules out a reverb anyway so i'll have to consign myself to a different post.

Ho hum, back to the drawing board, anyway, i don't think it is exactly the limiting factor in my riding!

Like I said, KS do the i900 and i950 in 31.6mm diameter, 75mm drop and 300mm length which sounds like it'll be the only thing to fit without a shim.

i was just googling your suggestion. thanks.

I still think there's something wrong with your frame. From what I can see from trek's website your frame has an uninterrupted seat tube with the top pivot welded to the side of it. The reason for having a full seat tube will be so it can be used as such and the fact that you can't, as I read it, is that the weld has deformed the tube somewhat and it's not been properly reamed following this.

Could you post a pic so we could see the situation as I feel either I'm missing something or these guys that are saying "that's just how it is "are.

Gaz

Have you thought about using a saddle with a smaller height/surface area that is not so intrusive when riding downhill?

Maybe you could play with the saddle position and stem length to get the saddle out the way as well?

OP - per my earlier post above, you only need 15-20 mm to fit a 100mm Lev or maybe even a Reverb. A few thoughts...

Are you certain that you are running your seatpost at the optimum height when fully extended? If you got fitted, and the seatpost has measurments on it [url= ]like this[/url] then you may be fine. If you're manually dropping the post and then guessing on the return position, you may be off a bit (either too long or too short) especially as you're probably rather conscious of only having 2 inches of post in the frame! A rough check is that your heel should be on the pedal with your leg fully extended while seated. I'd doublecheck this way or even more accurately if I were you; you may be able to pick up some more exposed seatpost length as a result. And its free.

How long are your cranks? I would hope that Trek put a shorter crank on such a small bike. Most MTB cranks are 175mm, 170 is less common, and some 165s are available as well. If you fitted shorter cranks, you would have to raise your seatpost by the same amount. You may be able to pick up 5-10mm here. To some extent, crank length is personal preference. Probably not cheap, though, unless you can find some on ebay or something.

What kind of pedals are you running? If you run flats, it would be pretty easy to switch to a thicker pedal and gain 5mm. If you run clipless pedals, it may not be worth trying. Could be cheap or pricy depending on your taste in pedals.

What kind of saddle is on the bike? From the photo on the Trek website, it looks rather tall from rails to seating surface. Its not just the thickness of the saddle's padding, but how much bend is in the saddle's rails as well. If you can find a comfortable saddle that isn't as tall, you'd have more seatpost showing. I don't know anything about women's saddles, but something like the WTB Deva may get you some of the millimeters that you need. Cost could be small or large.

Last resort in my opinion would be to cut the seat tube. Unlike everything above, this can't be undone. It would also almost certainly void the warranty on your frame. From the photos on the Trek website, there is not much of a seat tube above the triangular gusset, so a big enough cut to resolve the whole situation in one shot is probably not possible. Though I haven't seen the bike firsthand, I'll bet that you could probably cut 5-10mm.

So, you might be able to make it work by using some or all of the above. Just be aware that you would be on the very edge of what is possible fit wise, and that may make it difficult to change one of these components or even something else like riding shoes in the future. But it may make a 100mm dropper post possible...

HTH.

Is the seat tube actually butted 6" down or is it just that the weld has deformed the tube so the post won't go past?

I can't believe any company would internally butt a seat tube especially at that height - I suspect you're just getting duff information from the LBS to fob you off.

This image seems to show a Lush with the seat all the way down - why should your's not be able to achieve that?

[img] /[/img]

Have taken some lovely pictures and annotated them. Note the new spoky-dokies. I don't have a flickr account so i've put them in a dropbox. Hope it's clear. I don't hold out much hope of any solution other than taking up potholing.

[url= https://www.dropbox.com/sh/5sntufiegiguegv/etaJ-6D_xU/Trekerama.docx ]Drop box[/url]

Off for a run but will look at answering the other questions.

Using SPDs
I think the seat seems quite narrow compared to my hardtail.

Are the cranks measured from pivot to pivot? If so, think they are 170mm.

Was using an ikea tape measure and now found my real one so will check all my measurements are correct.

First thing - ONLY 42mm OF POST INSERTED??? THAT'S ONLY AN INCH AND 5/8!!! DON'T RIDE IT THAT WAY!!! AT ALL!!! You have a real good chance of damaging the frame or yourself! And I have spent to much time on this for you to die. 🙂

Crank length is center to center. It is usually stamped on the back side of the crank arm as well. I should have told you that!

Drop box, second photo. If your saddle is at the proper fully extended height and your 163mm measurement is correct, then you have just barely enough seatpost showing for a 100mm KS lev, and you are only a few mm short of what you need for a Reverb. (Lev needs 160mm, Reverb 165).

Unfortunately, the dropper post still needs to fit inside the seat tube. Your third photo clearly shows a weld intruding into the seat tube. I don't know if Trek considers this to be normal or acceptable; you'll need to ask them. And of course you can't tell from the photo how much the weld sticks out. I think you should try a shim with a 30.9 and 27.2 seatpost and see how far each will go w/o forcing it at all. It looks like you would need 190mm of post in the seat tube to fit the Reverb, and 175mm for the Lev.

There was a similar problem with another bike discussed [url= http://singletrackworld.com/forum/topic/seatpost-hitting-something-in-frame-normal ]here[/url] but the thread is left unresolved. So, a shop may or may not be able to ream out the seat tube to remove the weld. Reaming the butted portion would certainly not be recommended.

There is still hope for you (if you quit riding with 42mm of seatpost in the frame!) 😀

As Joe says DO NOT ride the bike with 42mm of seatpost in the frame AT ALL!

There's no way that frame should look like that on the inside it is almost certainly defective, please send these pics to trek themselves along with the story and get a non biased opinion (you can't trust a shop that cut the post to fit around what looks to be a problem with the frame and left you with an unsafe bike). Please call Trek UK and get to talk to a Trek rep about this there's a number on here - [url= http://www.bikebiz.com/news/read/new-address-for-trek-bicycle-uk/011128 ]BikeBiz Link[/url]

Once you've got the frame issue sorted we can work out how to get you an uppy downy seatpost to fit but that does look like it could be tricky as joe has pointed out. Out of interest what is your leg length? Sorry if that's a rude question, just that seat is really low for full extension and that's from someone with a 29" inside leg.

Gary

In defence of the shop they did warn before i bought the bike that it might be too big for me so i took a risk buying it.

Called Dave at trek who was really helpful. Suggested i take the bike back to the shop and they'd have a look at it. He thought the minimum insertion distance was 140ishmm for the 15.5inch frame which is much more than what i'm putting in. He also said this problem had been an issue.

Needless to say i shall be solely riding my hardtail with a whole seat post until this gets fixed. 😀

From the measurements you've given, you technically have room for a 296mm long post (163mm rails-to-clamp + 133mm clamp-to-weld). The KS 300mm post is obviously only 4mm longer which I think you'd barely notice to be honest.

Granted it would only give you 75mm drop, but I think with the limited amount of seatpost you have showing at full height anyway you'll struggle to find a 100mm drop post that will fit even if the internal weld on the seat tube were reamed out to allow more post inside.

http://www.pinkbike.com/buysell/1136501/ - one for sale on PB in Canada that they might ship internationally if you ask nicely.

Whereabouts are you btw? If you're anywhere near the South East you'd be welcome to try my OH's one (with a temporary shim) to see if it suited?

Have been looking into the KS. It's only £125 from hibike. It's currently my number two choice after the reverb. I agree that 75mm drop would probably be enough given my height.

Thanks for the offer, and the help, i'm a way away from you in the grim north.

here's a response from Gareth @ Trek on the issue (I pointed them to the thread)

[i]Hi Gary,

Thanks for pointing me to this forum post. I believe the store (name removed in case) have been in contact with us already regarding this issue (I can’t see there being two 14.5” Lush’ with post insertion queries!) and I believe the insertion depth has be found to be correct and it is the welds for rocker mount etc. that are preventing the post dropping any further. Please advise this is NOT reamed! This could damage the structural integrity of the frame. We are happy to get the bike back in house if needed to take some measurements and advise on our findings, so please let me know if this is route you / they would like to take, and confirm the place of purchase and I can arrange this.

Please let me know if this issue has been resolved / dealt with, or if I can be of any further assistance,

Regards,

Gareth Whitehouse[/i]

The store and trek have been very helpful and whilst i'm kind of back to square one at least we've explored every avenue. Don't worry all those who said i'd die if i rode it with a short post, this will somehow have to be resolved, though without a dropper post it will mean i can't drop the saddle much.

They have concluded i have 158mm clamp to weld so i think i'll order a KS and hope for the best. They suggested a 27.2 hilo and a shim but I'd like to keep things as simple as possible.

I like the idea of building up my pedals, maybe i could ride in platforms: groovy! 😆

Thought i'd update you on my progress and to help other small people with silly frames. Bought a 300mm KS supernatural as recommended by you guys. Fitted it last night. Really pleased with how it fits and looks. Just need to go out and ride it like i stole it! Thanks for the helpful tips. 😀

Hi,

I'm in same boat with OP.
Yesterday I bought Lush SL 16.5" for my wife.
She's currently riding Skye S 16".

Due to same problem that seatpost is not going into the seattube yet enough for her even fo to be able seat on the bike.
I think we'll cut the post for about 100mm too.
She's 165cm tall by the way.

I plan to buy RS Reverb 355mm lenght - 100mm drop - 31.6mm diameter
Do you think is this good fit for what we need?

Thanks

Quick update for reference for people with interupted down tubes/ small people.

So after all the faff I bought a KS dropzone from Hibike. (they sent me a supernatural (same post, just no layback) and i stupidly didn't send it back). After two failures on the post, 5 months back with the manufacturers and a total of 3 rides where it worked I have claimed the money back through my credit card. Hibike are a waste of time. I then bought another one out of desperation, failed after 2 rides, went back, refunded (thanks bike24 for a good service).

So then, it came to me. I bought a reverb 30.9 and shimmed it to 31.6. Yes perhaps this is dangerous and I'll die but so far it has been great and I'm really please with it.

So conclusions:
KS dropzones and supernaturals are shite. Don't buy them. Their quality control is appalling.
Hibike and it's relationship with KS is dubious, don't go there.
Reverbs are fab, i'm sure someone will come along and say what i've done is wrong, I guess the thompson 27.2 could be shimmed too.
I'd seriously consider avoid frames that aren't reverb compatible in the future.

evh22, I have the same bike as you (Trek Lush 2013 14.5") and hence the same problem. Although, when my seat is set for riding uphill, there is around 5" in the frame, as opposed to your 2".

I have ordered a 30.9 reverb and 31.6 shim and will hopefully get them fitted tomorrow, as long as I've ordered something that fits / works.

Thank you for posting your update. It's not often that you find that, in forums. Usually, once the quandary is resolved the OP will forget that they had promised to give an update 😉

I'll try not to forget to let y'all know how I get on.

So, the first shim that I ordered was the wrong size. I had misunderstood the OP. But, not to bother. I ordered the correct one:

Code: EV204355
Description: EV204355 316-NA WMFG SPOST SHIM 30.9MM 316
QTY Total: 1
Cost £10.79
TOTAL £10.79

From Evans Cycles.

But then, when I went to pick up my bike, I was told that they 'hadn't needed' the shim, and they promptly refunded my £10.79. I must admit, I was a bit worried, having read the above, about how a shim is necessary for the Trek Lush. But, today I went out on a 19 mile bike ride around Widdop, Worsthorne, Hebden Bridge and the like, and it was absolutely fabulous. I wouldn't be without one, now. I was operating the switch all the time, and the reverb allows the seat to go lower and higher than was ever possible using the bog standard seat.

The only thing I found was that if I knocked the seat from one side, it would move. I was worried that this was due to there being no shim, but my pal tightened the seat post clamp, and the problem was resolved.

If anyone has any thoughts re: my riding the bike without a shim in place, do let me know, but I must say that I'm very happy with the product and the service that I received. 🙂

Glad to be of help! I am fast becoming a world expert on biking for small people. Great to see someone else is having fun on that bike.

If your seat post is moving around then that suggests it isn't in tight enough, which suggests you need a shim.... I'm no expert but this is what I'd do. There is a suggestion that using a shim invalidates your warranty. Not sure of the truth of that. You can get a nice UST shim for about £6. Feel free to get in contact if you need any more small person help.

How have you routed your hose? I have had problems with the amount of slack you need rubbing on my rear tyre wearing it out.

I'm thinking of solving all of these problems by buying a Pivot Mach 🙂

Thanks for replying 🙂

I've just spoken to the people at Evans, who say that, actually, the shim that I ordered didn't work... it was too big, and so the guy fitted it without, test drove it, and thought it was OK. However, they agree that my seat shouldn't be rotating left/right if knocked, and so have asked me to bring it in again at my convenience and they will find a shim to fit.

I can send you a photo of how they have routed the hose, if you'd like?

Thank you for your small person MTB help!

Sorted the routing now thanks. Great to see Evans at their very best. The USE ones will fit.