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Old 10-21-10, 08:30 AM   #1
SortaGrey
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LONG seat post.. custom or ??

I have a Raleigh Gruv 2 I need to make/acquire a seat post for. Given my height and that I am
now using an old style seat that clamps to what I believe is a 7/8" end diameter.. the ones I can
to date do not go into the frame far enough. My stem now is around 8"+ out of the frame.. the
mounting tube allows 13" of length inside for post length. Occurs to me now given my weight to
use a stem that goes the length of the inside tube.. plus the stem length needed to give me the
riding height.. possibly using a blank of sorts inside at the bottom to adjust for length if need be.

Dont care about weight or perfect cosmetics... something practical that'll last is the idea.

Anybody make something custom? Or.. where could I acquire the 27.2 mm~1.07" stock needed
have one fabricated?

Thanks for looking in at my question.
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Old 10-21-10, 08:51 AM   #2
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SortaGrey, Look at mountain bike seatposts, they're typically longer than those for a road bike. Likely not going to find one with the post at the top like you describe. If the seatpost inter connector can't be removed you'll need a new saddle.

Brad
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Old 10-21-10, 08:59 AM   #3
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MTB seatposts are available up to about 400 mm in length and will include a much better saddle clamp.
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Old 10-21-10, 09:55 AM   #4
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My guess is that your "old style seat" has a clamp that mounts to rails allowing it to mount to a 7/8" diameter seat post. Removing that clamp should leave you with rails that will mount in modern seat post clamps.
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Old 10-21-10, 09:56 AM   #5
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I have found the BMX Chrome Moly seatpost quite strong, as sold by SBS, under the Red Line brand.
in both 7/8" continuous , diameter, or as I bought 7/8 on the end, and 1 inch on the rest of the post.
Shims may be found for frames that are needing a different diameter. ask at LBS.

A series of Lower Outside diameters with the 7/8'' top diameter in common are made in aluminum,
Kalloy brand common.
I'd consider regularly replacing those to be prudent, but at $15 each, no great expense ..

I have discovered Brompton's Penta clip, to be the best saddle clip made for
using on the plain top type seatposts ..
they cost a bit, but are infinitely adjustable ,and mostly aluminum.

can be arraigned in several configurations, ahead or behind the seat post,
rails higher or lower in the clamp portion..

I note Rivendale bought a Nitto 22.2/27.2 seat post which costs more ,
nicer finish ,
I don't know what the alloy difference is, and their relative strengths .

Last edited by fietsbob; 10-21-10 at 10:06 AM.
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Old 10-21-10, 10:28 AM   #6
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I looked up the Raleigh Gruv 2 only to find that the pictures were of a low slung "Harley" looking cruiser bike with the cranks set well out in front of where the optimum spot should be.

THis is very plainly not a good choice of bike for someone overly tall. You don't need a longer seat post, you just need a different bike.

The tubing that is sized for these seat posts is not something that you'll find at any hardware store or even a usual industrial metal supplier. It's custom drawn for the bicycle industry from aircraft alloy. I have never seen any of it advertised for sale. Not even on the rare web sites that sell tubing sets and components to be used for custom bike frames.
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Old 10-25-10, 08:39 AM   #7
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Many Thanks to everyone for all for the info and insights... I do appreciate it!

Yes... to the frame style and angle of the tube holding the stem per tall riders. I see now my original stem is bent somewhat at the end.. those last 8" or so proturding from the tube. I hope no one reads this & faults Raleigh for this.. that is my height.. vs the soft nature of the steel used in those stems. I added a few pounds this summer not riding.. and it appears like I found the upper limit of this stem vs rider height & weight. Yet I do see the tube and frame around this critical area is fine.. the design strong and well made.

I measured 14" of inside tube length for a stem.. I need around 8" of stem height out of the tube.. considering a custom stem.. turned on a lathe. I'd have to leave some room for height adjustment.... first thing that comes to mind is using a system that employs some media... something that flows to occupy space down tube. Easier to remove I'm thinking..what exactly that agent is I don't have a good idea now.

Far side idea: a wood stem.. turned from something like good hickory... or similar tough grained wood that has a little spring/give. The height outside the tube.. could be metal with the wood dowel clued into it.

Not looking for a cheap way by any means... I like the bike style and bike very much. And I want to get some serious mileage on it.
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Old 10-25-10, 10:37 AM   #8
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Maybe a Banana seat , or something functionally like that,
so the back of saddle is also supported down to the rear axle,

sharing the load with some of it coming off the bending force on the seat post.
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Old 10-25-10, 11:11 AM   #9
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At my community bike shop someone donated a bike with a solid aluminum rod that had turned down on a lathe to 28.2. (or whatever he needed) with the end brought down enough to fit an old-school seatpost clamp on. The guy that donated said he made it at work since he was a machinist. If you know a small shop they might do it for you without too much hassle... just bring in your current seatpost and explain your needs. There might be a thick-walled aluminum tubing that could be turned down (go for heat treating too) and still be strong if money is really no object

The funny thing was that despite being rather long and solid, it is not the heaviest seatpost we have.
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Old 10-26-10, 08:40 AM   #10
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Spend a good hour yesterday studying on the frame angles of the Gruv 2. My height makes for a weight placement just barely forward of the rear axle. Noted this effect last summer climbing a short hill in the woods.. as I standing up on the ground quickly as the front wheel came up with the weight shift behind the rear axle.

My original reason for the Gruv was less knee strain.. this seems to be helping. I do not have serious knee issues.. just minor strain in the right one especially.. and I want to keep it minor.

So.. with the need for a custom stem.. I am considering something that would correct this weight being placed so far back... and possibly experiment with how far behind the petals is ideal. From this perspective: my conventional 10 now 14 speed Schwinn Traveler takes some weight off the 'caboose' area.. my more upright handle bars forces some weight onto my hands. And this seat to petal relationship makes one lift your body in a minor way while applying the downward stroke to the petal. The effect being I'm working the leg muscles in a different way vs the crank forward Gruv... and not having this continual weight setting on my ass.. putting that critical area to sleep. Now my thinking is attempting to fabricate a stem that negates the stem going back towards the axle as it is raised. And then.. possibly.. making it possible to move the seat to and fro.. per adjustment on a top rail.. to experiment with some 'sweet spot' per distance behind the pedals vs continual weight on the butt.. ie.. getting those muscles in play and not constantly subjected to weigt.

I seem to remember someone posting per a system allowing seat adjustment forward and back but can't find it archived. Anyone have a link.. or input on these ideas?

Yes to the heat treatment per one suggestion.. or some similarly strong end product. I raised the idea of wood... I chuckle at that now.. . Nothing sez the stem once out of the frame has to be.. or would be round either. This is beginning to sound like some engineering challenge.. or some new invention.

NOTE: I use conventional platform petals.. anything tying my foot to a petal is out for me.

Last edited by SortaGrey; 10-26-10 at 08:45 AM.
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Old 10-26-10, 09:17 AM   #11
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Rans also offers the crank forward frames too , the stop and have feet flat is more secure for some,
but yea front wheel has a small % of the weight.

part of the reason bike frames look like they do, achieving balance . 68~73 degree seat angles..
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Old 10-26-10, 09:32 AM   #12
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Quote:
Originally Posted by SortaGrey View Post
My original reason for the Gruv was less knee strain.. this seems to be helping. I do not have serious knee issues.. just minor strain in the right one especially.. and I want to keep it minor.
You can put as much or as little strain on your knee with the Gruv as with a conventional bike. It is all a matter of how you use the gears.

I just came off a serious bout with knee pain. Could barely walk for a couple of weeks and still can't push very hard with my right leg or my knee lets me know it is not happy. Just got back on my bike this past weekend and did 10 miles Friday and 20 on Sunday. I have to start out in a lower gear than I normally would and can't get out of the saddle to pedal but it isn't too hard to lessen the impact on knees even on a fairly serious road bike.

As propelling most bikes forward requires pushing on pedals with your legs, the amount of stress the knee takes is based much more on how hard you push the pedals than the angle your leg is at.
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Old 10-26-10, 10:10 AM   #13
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"You can put as much or as little strain on your knee with the Gruv as with a conventional bike. It is all a matter of how you use the gears."

True of course in one sense. Wrong in another.. angle of the work being done with the knee makes the range of motion more/less stressful to the knee from different angles.

Sooner or later.. you have to apply some torque to get the job done... unless your toddling along at walking speed... spinning away minus much if any resistance. From my experience.. a position farther behind the petals means less knee strain for me. Not really as simple as gearing I'd suggest...
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Old 10-26-10, 11:03 AM   #14
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No, he was right. You likely picked the Gruv because you are able to extend your legs out and the joint of your knees are almost straight out when at the furthest reach of the pedals, right? Setting things up that way produces the least knee strain. Setting up a normal bike frame with that same reach by raising the saddle will do the same thing for your knees. The difference would be that you won't be able to reach the ground while in the saddle any more. Instead you'd have to do like the rest of us and shift forward off the saddle when coming to a stop where you need to put a foot or feet on the ground. The upside is that your pedalling efforts won't be trying to push you off the back of the saddle on hill climbs. The Gruv is likely a fine bike if you want to just ride around on flat roads or trails. It ain't worth a pinch if you have any mild to serious hills to climb due to the position of the pedals on the thing.

Getting back to your seat post.... There's a number of good quality seat posts for mountain bikes that are 400 mm long. That's almost 16 inches. That'll give you the 8'ish inches of exposure you need along with a whopping almost 8 inches of bury to seat well in the frame. And no need to get into making something custom.

If you do go custom then the long rod idea from solid aluminium or extra thick wall tubing sounds not bad. If you use tubing then forget about heat treating it yourself. Aluminium isn't like tool steel for heat treating. It has to be the proper alloy for starters and the process is more complex than with steel so it has to be done during the manufacturing of the alloy and not afterwards by someone with a torch and a dunking tank. So if you go with tubing it would need to be an aircraft alloy with the proper "T" number on the end of the alloy number. If you go solid rod it won't be so important.

But frankly given the cost of shop time to turn such a rod I'd suggest you just pay the premium price for a 350 to 400 mm mountain bike seat post.
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Old 10-26-10, 11:35 AM   #15
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I just disagree... per the knee issue and bike styles. That is my conclusion... works for me.

Hill climb is again same.... if anything.. the Gruv climbs somewhat easier for me. Could be my handle bar adjustment.. I pull myself into the petals. The Day 6 CF design has the back set to push off of... whiich I only rode 10 mi or so... didn't care for that design overall. Bike too long.. HB's too high... lack of gearing.

Shop time.. for sure. But there's allot of guys around with lathes.. minus the high hourly rates. This turning very simple... this route considered per adding other features to the stem. MB stem an option if I stay with this configuration.
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Old 11-19-10, 04:53 PM   #16
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http://i54.tinypic.com/slgx8i.jpg

Fixed my seatpost.. took the two I had and made one good one. Changed the angle of the post... moving in effect the center of the weight forward around 4". BIG difference cornering... the seat shown is temporary... that still needs work.

I'm 6'3".... extending the seatpost to fit my legs meant not enough post in the seatpost down tube. And... made the weight too far back on the bike.

NOW.. to get the right seat.............
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Old 11-19-10, 05:54 PM   #17
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Quote:
Originally Posted by SortaGrey View Post
http://i54.tinypic.com/slgx8i.jpg

Fixed my seatpost.. took the two I had and made one good one.
I can just see that modified post breaking at the bend and embedding the rest of it far up into certain body parts...
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Old 11-20-10, 01:38 AM   #18
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This has all kinds of bad written all over it. Did you say you were a heavier rider, as well?


As I look at how you've attached your saddle and "bent" your seatpost to put you further forward of the rear wheel, it seems strange to me you say you "don't like the riding style" of an MTB. You're effectively trying to curve the geometry of the bike frame to go from a laid-back position to a more upright, classical riding position. It seems to strange to me to do that by creating serious structural weaknesses in the part you're putting all your weight on, rather than just trying out some more conventional frames. If anything, I'd say your body's telling you the bike just doesn't fit its preferred riding style.

Last edited by peripatetic; 11-20-10 at 01:45 AM.
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Old 11-20-10, 07:29 AM   #19
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This has all kinds of bad written all over it.
I agree that looks dangerous. and at 6'3" I would think you need a bigger frame.
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