torquewrenchles

I need to set my seat back 2+ inches, and as there are no normal setback seatposts available to do that, I'm considering this skanky world of cooking-pot-metal BMX seatposts:

https://www.amazon.com/gp/product/B001RZFVHO/
https://www.amazon.com/gp/product/B000AO9ZPW/
https://www.amazon.com/gp/product/B001CTBGME/


Unlike some of the Amazon reviewers reporting the metal bending under them the first time they ride around block, I do weight well under 220lbs. Note the last product URL -- a reviewer describes reporting a bent seatpost to the company, and their response was to update the Amazon product info to state: "This post cant be sat on and is for jumping not ridding". :|

The other concern is the leverage of the seat post cracking the seat tube. I'd be using it on a reasonably hefty alloy comfort bike, for casual riding on paved streets. An issue is that the seatpost has to be shimmed -- and the available shims are only 10mm long.

Anyone have any experience with this?

P.S. a "larger" frame won't help -- the sole issue in moving knees relative to pedals is effective seat tube angle. And I'm finding a slight undersupply of bikes with the 66º seat tube angle I need, at any frame size.

pierce

I didn't follow those links, but the Wald steel BMX seatpost I used for a bike with an unusually skinny seatpost bent rather easily when I had it setup rather tall, and I hit a bump with my 200 lbs bouncing against the seat.

When I bent two of them, I retired that bike. Sad, as I'd had that bike for 30+ years, its original seatpost was fluted alloy, which was very strong and light, but eventually developed cracks. the Wald was the /only/ seatpost I can find in 13/16" (a very old BMX size).

ThermionicScott 

What bike do you have that can't be adjusted to fit you properly?

torquewrenchles

The one with the 72º seat tube angle that already has a 15mm setback seatpost, and only about 20mm available on the saddle rails.

I need about another 2 inches of setback from somewhere (saddle rails + switch seatpost), in order to get my knees properly positioned over the pedals.

That means a replacement seatpost with 45mm setback.

I've SCOURED the web. It just does not exist other than these flimsy BMX ones (which are actually probably too much setback).

Did exist (although wrong diameter and this post isn't long enough for me):

https://www.yellowjersey.org/SRMTE100.html

The Nitto Wayback comes close (40mm)... but totally wrong style for the bike, not long enough post, and half the cost of the bike.

Bike industry selling bikes with steep seat tubes and no means of adjusting them for a wide range of human femur-to-leg proportions. Bike shops unethically selling bikes without checking the customers' knee position. Lots of clueless people riding badly-fitting bikes. Lots of clueful people posting messages on forums looking for seatposts with extreme setback.

I'm returning one of those badly-fitting bikes today, due to inability to make a 1 inch adjustment. Very frustrating.

ThermionicScott 

Hmm, I ask because these seatposts seem like a band-aid fix. Is your saddle high enough to allow your legs to be almost straight at full extension? Do you have large feet that are too far back on the pedals?

If nothing else, KOPS isn't an inviolable law -- it's a rule of thumb that grew from tradition, and triathletes regularly end up with their knees ahead of the pedal spindle.

CACycling

Needing excessive setback and seatpost length points to a bike with too small of a frame for you. Sounds like your LBS sold you a bike that doesn't fit and have left you to try to make it fit. I'd return everything and find a new shop.

FMB42

Here's a link to "Custom Motored Bicycles." This outfit has a braced layback post that might work for you (scroll down about 1/2 way down the page).

https://custommotoredbicycles.com/bic...s_seatssaddles

I, of course, can't say for sure if your aluminum frame seat tube, or this seat post, will hold up tho...

fietsbob

If you must Only get Chromoly Steel .. they, are I expect 7/8" OD.. need shim sleeves to reduce
the frame seat tube to that the OD to fit.

another trick..

I have adopted the Brompton Saddle adapter pin It goes on top of a standard plain top seatpost.ala Kalloy in all sorts of diameters.

and offers a horizontal Tube to clamp a saddle cliparound , sitting above the horizontal Tube.
its good for about 2.5" + what amount you can shove the saddle back on its rails.


Of course going to a crank Forward Frame really puts the seat back ala Trek Pure.

surreal

Sad. I used this on an old schwinn; very long, chromoly, strong... definitely a step up from the Wald. (I love Wald, in general, but some of their stuff is jenky.): https://www.porkchopbmx.com/CR-MO-13-...m-POIMSP07.htm

Here's a pricier option: https://genuinebicycleproducts.com/parts.html Aluminum; i've never used it.

BITD, the clunker guys just used a solid length of true 13/16" aluminum stock: https://www.clunkers.net/tips/tips.html

OP: please tell us what frame you have, so we can better assist you.

pierce

yeah, I found that genuinebicycleproducts website, and ordered one.

the old alloy post the bike had lasted 30 years.



(film picture from about 10 years ago)

this bike is a unknown brand of 1960s/70s cruiser that in the mid/late 70s was converted to a 5 speed using a pile of color anodized early BMX parts. circa 1980, I built that back wheel with a sturmey archer drum and 6 speeds. some time in the late 80s(?) the front wheel was destroyed, I used a decent mountain bike front wheel I scrounged. around 2000 I powder coated it red. about 4-5 years ago the drum brake axle bent then broke, and was unobtanium, so I replaced the back wheel with another mountain bike wheel, and we brazed V brake bosses onto it and it became a 7 speed.



since then, the fluted bars developed cracks (I was warned up front they would, they lasted 25 years!), so I put some black cruiser bars with a similar bend, maybe a bit narrower reach, also replaced the gooseneck.. the fluted seatpost cracked, so I replaced that with the wald. maybe when I get the alloy one, I'll take a new picture

hueyhoolihan

OMG those look like they are designed for 60 lb. kids, not adults.

surreal

pierce, your bike looks pretty rad. Looks like it may've started life as a monark middleweight; i'm just guessing from the rear triangle, but i guarantee that there are perverts online who can ID it accurately, and probably cannot wait to do so.

OP: I left these out: https://www.ratrodbikes.com/forum/vie...hp?f=2&t=59700 $15 plus shipping; the first post says it's 1" solid stock, but he made me one in 7/8" with a 90degree bend, and it's held up well under my 250# thus far. (tbh, it ain't been long). He'll do custom bends in 1", 7/8, 13/16", etc. If you follow the thread, he's got other designs as well, and even offers stainless now (at twice the price; I'd have sprung for that if they were available when i ordered mine).

Which isn't to say it won't fold under ya, but if you want bulletproof durability, Thomson makes a layback version of their elite post for $90 and a layback masterpiece for $130... The solid steel jawns weigh about a ton, but it seems exceedingly solid. All the rat guys have reported trouble-free experiences so far, from what I've seen.