rumrunn6

mine keeps slipping it's angle & a bike pro says any two-bolt post would hold the saddle at the angle I set. yesterday on a single ride I had ti stop twice to move it back in place

so looking for

27.2 mm diameter
300 mm length
two-bolt clamp design
but I don't know how much set back

I have a one-bolt clamp style now: pro xrp 27.5 mm for bottecchia alloy seatpost

but I can't find what setback it has so I can replace it w a two-bolt unit

this is how mine looks




I like the clamp mechanism on my Bontrager seatpost

rhenning

Almost the most common seat post there is. Any bike shop and on line retailer can get you that size. When you go to a shop bring the old one with you. The 2 bolts styles are no better and are harder to adjust. Roger

tomtomtom123

You could place a straight edge or ruler against the front face of the seatpost, then measure the horizontal distance parallel with the clamp between the ruler and the center of the clamp, then subtract half the diameter of the seatpost, to get the setback. Or take a photo of the seatpost from the side, bring it into a photo editing software, like photoshop, and measure the distance with a measuring tool, or just display the photo on your LCD screen and measure the distance with a ruler against your screen. If you also take the measurement on the screen of the seatpost, then you can calculate the setback by mulitplying with the scaling factor since you know that the real width of the seatpost is 27.5mm. So for example theoretically if you measured the screen and see that your seatpost is 3 units, and the setback (between the centerline of the seatpost and center of the clamp) is 5 units, then to get the setback would be 27.5/3*5. You have to take the photo perpendicular to the seatpost and as far back as possible while zooming your lens as close as possible to avoid measurement errors, since lenses have distortions and also if the camera is too close to the seatpost, then the perspective will get skewed and objects further from the center of the image will appear closer.

Brooks saddles have very short rails. I have mine all the way back but it's still around 2cm too far forward. I have a Thudbuster ST which supposedly has 11mm of setback, but it travels further rearward when sitting on it since it has a parallelogram. But as the load on the saddle is constantly changing, the average is usually not much further more than the stated static setback. So I have to accept it and raise the seatpost a little bit to compensate.

Also, for me, 2 bolts on the thudbuster worked much better than my old single bolt clamp which kept having the saddle slip backwards. The angle was stable on the single bolt clamp, but that's because it had matching teeth grooves between the post and the clamp. 2 bolts does make it easier to adjust the tilt angle (if it has no positioning grooves), since you can loosen the rear bolt, and then use the front bolt to make 1/8, 1/4, 1/2 turns to make fine tune adjustments. That's how the thudbuster works. The front bolt is a knob and can only be turned with fingers for fine adjustments, while the rear bolt can only be turned with a wrench for the tightening of the clamp. Also, be careful not to strip the bolt or barrel nut on a 2 bolt clamp since the bolts are usually smaller diameter than 1 bolt clamps. Thudbuster says 5 or 6 Nm on their M5 bolts.

AnkleWork

Shoppin' ain' easy (and apparently getting more difficult every day - curse this post-internet era!).

HillRider

Are you thinking of 27.2 mm which is a very common diameter. 27.5 mm? Not so much.

Also, I disagree that a single bolt saddle clamp is easier to adjust. I've used both single and two bolt clamps and find the two bolt type far easier to adjust precisely and to hold its adjustment once set. Notice that almost all the better quality seat posts (Thomson, Race Face, Easton, Ritchey, etc.) use a two bolt clamp.

DOS

Thomson Elite Setback or Veloorange grand cru.

DOS

Two bolts are far superior, no,doubt.

dsbrantjr

You need to know/measure the diameter to a precision of 0.1mm. If you pull the post it is often stamped on it, otherwise measure it carefully with a caliper or micrometer.

cyccommute 

The best “two bolt” seatpost I’ve ever used has been Race Face’s cantilever seat collar posts. You can see it on this bike


DSCN0164 by Stuart Black, on Flickr

Unfortunately, they don’t make them anymore but you can find them on Fleabay.

jimc101

It's a nice design, but you need to have enough clearance/flexibility on the saddle sides or you can't do up the top bolt.

cyccommute 

I’ve never had a problem. As you can see in the photo that’s a Brooks that has a lot longer side than most saddles. It wasn’t a problem getting the top bolt fastened.

Drew Eckhardt 

Don't buy a Velo Orange seatpost. Their bolts are too thin and fail due to fatigue, even when replaced with a higher grade.

DOS

Now I am going to have to go look at my bolts. So far I have not had a problem.

mpetry912 

you can buy replacement bolts of higher quality for those seatposts.

I recommend the Nitto 2 bolt seatpost, it's super strong and will not slip.

There are other designs that are "interesting" but few if any that are better

Mark Petry
Bainbridge Island, WA USA

rumrunn6

thank you it's 27.2 mm

jimc101

I tried mine (exactly the same model of seatpost as yours) with a Rolls, and couldn't get it to work, guess it depends where you have the saddle positioned, and Rolls have pretty inflexible sides (or at least I wasn't planning on bending mine out of shape), works with modern designs like Fizik saddles perfectly.

79pmooney

Your seatpost is very "normal" for setback. Probably very close to the 16mm of a setback Thompson post. That, a Nitto (I haven't checked them for setback though I do have the steel big setback Nitto that I love) or an old SunTour (all very high quality posts with very good clamps) would suit just fine as a replacement. And now that I see your diameter is 27.2, not 27.5, finding that post will be easy. Have fun hunting!

Those who say 2-bolts are a pain and those who say they are a joy are both right. One bolt posts are much faster for a shop mechanics to slap on the seat and get it showroom level. 2-bolt post allow you to make very small tweaks on the road, document the change in your head (1/8th turn down for example) and go back to the old position exactly later. Yes, messing around to get the seat on takes longer. My butt likes perfect tilt. I'll take 2-bolt every time. (Almost true. My commuter has a scratched Campy Chorus 1-bolt. Tilt is perfect and has been the past umpteen years.)

Edit: I've never owned a Thompson post but Thompson sells its clamp parts to framebuilders. I have two custom extreme setback posts with that Thompson hardware. Joys to use! So is the big setback Nitto steel post. I wouldn't put the SunTour in the same "joy to use" category, but I have ridden a couple of them for mny thousands of trouble free miles. (They use different allen wrench sizes for the front and rear bolts. I recall them being a little harder to juggle the seat into place. NOw, the adjustment with the front allen bolt completely accessible in front of the post is nice!)

Ben

AnkleWork

Shoppin' ain' easy especially when you don't know what you're looking for.

trailangel

This is the one you want:
https://www.universalcycles.com/shopping/product_details.php?id=18232&category=167
Only one other person mentioned this.
The people that complain about 2 bolt being a hassle are the ones that hear about older Campy. That would work too, just the bolt heads are on top. You won't find the Campy in 300mm length.

rumrunn6

$98!

trailangel

Only hurts one time, instead of continuing to purchase cheap again and again, when you find out there is a lot of junk out there.

Drew Eckhardt 

The new ones broke too when I did that.

The Velo Orange bolt diameter is too small for the application.

I gave up on two bolt seatposts after that, wasn't happy with the 16 NM it took for a Nitto S65 to hold its adjustment, and tracked down a 1995-1997 Campagnolo Record SP10-RE post which worked like the old C-Record Aero post I abandoned to get a round surface for clamping a rack to.

HillRider

I have Thomson set back seat posts on two bikes and they are the easiest posts to set up and most stable I've ever used. Both bolt heads face downward and are super easy to get to and adjust. Also, the top of the saddle clamp has a witness mark and the bottom of the has a degree scale so changes to the saddle angle are very easy to see and reproduce.

The only drawback to the Thomson setback post is you must have a specified minimum of post exposure (typically 90-100 mm) above the top of the seat tube to clear the "kink" in the post that gives the setback.

Cheap? No. Worth it? Every penny.

Sy Reene

Take a look at the Fizik seatposts (R3, R5).. The clamp surface is great and long, compatible with a number of rail shapes and sizes, and acts like a 2-bolt system, but one of them is actually a thumb wheel that sets the final angle, before tightening a single allen bolt to secure.

79pmooney

So the Fizik uses a thumb wheel instead of one of the bolts and saves using the allen wrench we already got out for the other bolt. Nice but hardly a "breakthrough". I've been using the rear bolt as the clamp and forward for the adjust the last 40 years. I actuallyu like using an allen vs a thumb wheel. I can track exactly how much of a turn I made with an allen wrench. I'd have to mark the thumb wheel and track those marks. (Not to downplay the Fizik post. I have not seen it.)

As a poster above says re: the Thompson - yeah! Those clamps, even on custom posts made by others, are really sweet! The comment on the Nitto being a pain surprises me. The big setback lugged steel Nitto post is as much a joy to use as the Thompson. The old SunTour posts had the very accessible front bolt forward of the post to use as the adjust. It was a 4mm instead of a 5mm so I needed both wrenches, but the mechanics and ease of adjustment were super.

Re: the VO posts. The company says specifically NOT to replace the bolts with aftermarket. I haven't used their posts and have no plans to do so. Too many other good posts.

And re: $$ spent for seatposts - my Nitto steel would outlast my grand kids if I had any. I've broken two Avocet posts on rides. One 40 miles from home long before cell phones. Painful ride home! The other on day two of Cycle Oregon. Spent the rest of the week and most of the next year on an ill fitting Laprade (sp) while my custom was being made. A few more bucks spent both times would have been so worthwhile!

Ben