crushing carbon rail saddles....

[blue151]

Hi,

I was just wondering whether anyone has heard any stories or have had the unfortunate pleasure of crushing a carbon rail saddle.

Reason i ask is the my saddle (prologo scratch nack) requires that my seatpost clamp (dorico ltd) to be tightened to the point where it makes a small indent in what appears to be the clear coat... if i tighen it less, the saddle comes loose on a ride...

should i be concerned about the indents.. or is it superficial?

I have torqued it to approx 7nm (depending on accuracy of torque wrench)

cheers

[Calnago]

I also have the Dorico LTD and a Scratch Nack Pro saddle. Are both bolts torqued to 7Nm? I have not had to apply 7Nm of torque to a saddle rail. I did find the Dorico a little finicky to adjust however. The key is to get the torque relatively even on BOTH bolts. This can be tricky. But essentially, I went back and forth loosening and tigthening one or the other until at some point you'll have about the same amount of torque on both bolts and a level saddle (or whatever tilt you prefer), all at the same time. I would try around 5Nm max for both bolts and that should be plenty. If it seems that one bolt has way more torque on it than the other, then go back and forth some more until they don't. Loosen the tight one some, tighten the loose one more, repeat until you get it right. I suspect this might be your issue (uneven torque on the two bolts), but not sure. Report back and let us know how it goes.

[thisisatest]

the dorico post HAS to have one bolt tighter than the other, as one bolt is much closer to the "fulcrum" than the other. Less-than-stellar design IMO. Especially since it's the front bolt that gets overloaded when tightening, and the front bolt is under increased strain from bumps in the road.
some companies come up with engineering solutions that make me say, "WTF?!"

[Calnago]

the dorico post HAS to have one bolt tighter than the other, as one bolt is much closer to the "fulcrum" than the other.

Not so. When I first started the install I instantly realized that one bolt was much tighter than the other. As you so eloquently put it I immediately thought "WTF!". So, I loosened the overly tight bolt and tightened up the looser bolt while trying to keep the seat angle constant. The "fulcrum" is in fact rounded and will pivot freely. It took a bit of trial and error but you can eventually get a very even torque on both bolts and the saddle tilt you desire simultaneously. With a digital level on a straight edge across the top of my saddle I was eventually able to get the saddle at 0.0 degrees (level) with the same torque on each of the bolts. And getting the torque even is very important for securing carbon bits, be it saddle rails of handlebar clamps. Liken the process to building a very fine wheel... It is a process of small even adjustments with constant stress relieving that will build a fine wheel in the end. And I love the relatively wide base that the Dorico mount has for the saddle rails to settle upon. A very good design in my opinion. Be patient and you will get there.

[blue151]

cool thanks calnago.. will try and get it to the same torque...

i do notice that when i adjust the front bolt to fix the angle.... and subsequently tighten the rear bolt.... the rear one keeps torquing at a similar torque and the front bolt just keeps getting tigher.. bit odd i know.. and hard to describe.. but yeh.. will try and even out the torque...

[blue151]

half and hour of tinkering..... finally doing alternating 1/4 turns of front and rear screw i think i have it at the same torque...

tis a bit hard to believe the wrench purely because when i tighten the rear bolt.. that seems to increase the tension on the front bolt.. but yeh..

will give it a good ride during the week and willsee howit goes...

Cheers!

[LouisN]

Make shure you bring your hex key along...

I had to adjust my saddle (with Ti rails, but I'm thinking about getting the Scratch Nack) about a zillion times with the Dorico LTD.

tis a bit hard to believe the wrench purely because when i tighten the rear bolt.. that seems to increase the tension on the front bolt.. but yeh..

Normal I think

I found that I had to adjust also the angle (fore/aft) of the front clamp correctly (that was more important than the tension IMO) on the rails. Then adjust the rear clamp with the same attention to angle, then tightening the rear bolt to adjust saddle tilt. This way, the saddle wouldn't "slack" after being stressed by the rider. Maybe the carbon rails are not prone to "slide" like metal ones...
And that is just on the trainer, didn't even go outside yet...


Louis

[blue151]

yeh.. its not easiest post to adjust.. or get right for that manner...

hopefully it stays put this time...

[thisisatest]

i must disagree... the fulcrum, or pivot point, is the saddle's cradle. one bolt is much further away from the cradle's pivot axis than the other. assuming properly lubricated threads and spherical head seats, the front bolt MUST have a higher tension than the rear bolt, equal to the ratio of their respective distances from said pivot. the only things that can cause a torque wrench to read even values are related to excessive friction. Of course, if you have a "clicker" style torque wrench, and you tighten the rear bolt to, say, 5nm, the front bolt will click as well. But I will assume that is not the malfunction.

[thisisatest]

oh, and back on topic,
I have never seen a carbon rail get "crushed". I believe most, if not all, carbon rails are solid, not hollow. It would be very hard to crush the rail into itself.
I have seen some broken, but mostly on mountain bikes.
If the rails are shiny, it's probably just the clear outer that is taking a beating. I feel the saddle is fine, but the edges of the rail clamps on the Dorico are thin and sharp. I would consider swapping rail clamps with another brand's version, unfortunately the Dorico uses m6 hardware instead of the more common m5, and the bolt heads are unique. Worth a search, though. Or get some thin stainless sheet, or at least sand the clamp edges some. It would make the clamps slightly narrower, but at least they wont be as sharp.

-Greg

[itsacarr]

I have ridden maybe three different relatively fancy carbon railed saddles in the past few years and have yet to ever crush or see a crushed saddle - im not heavy by any means but I have shared the same worry for a while but have yet to see anything bad happen ... yet

[boss155]

Buy yourself a cycle torque wrench, never need to worry then. Also, solid carbon is strong when built in this way.

[leosantos]

resuscitating this thread, Im having a sworks toupe installed on a dorico ltd on the weekend. I actually played a little with it earlier today and a couple of things were in my mind

1) its about impossible to use my torque wrench (a BBB like this http://bbbcycling.com/accessories/tool-boxes/BTL-73/" onclick="window.open(this.href);return false;) to torque the front bolt, since the wrench's head is scratching the shaft and won't fit fine in the bolt's head. even if I didnt care about scratching my post, it just doesnt seem to fit or titghten right r enough.

2) the wrench was set for 2nm torque, and in tightening the rear bolt, it seemed as I never reached the 2nm. I was scared to crush it, but now I read here it is not gonna happen, so I might try again. However - and my wrench is well calibrated for sure, Ive never had problems with stem, bars and seat tube clamps , so I have a bit of a clue of what 4nm feels like in my hand, and no way I havent put 2nm on that bolt. This issue resembles what I experienced with my previous seatpost (USE alien cyclops, the one bolt designg), it never seemed to have reached the torque because that designed also made it a bit difficult to correctly fit the wrench's key on the bolts head, no matter how much I titghtened it. once i crush the alien's bolt itself, what a pain!

since no one mentioned this issues before (problem in actually tightening the front bolt at all and chance of braking the bolt, not the rails), I must assume Im doing something wrong! again, I was just playing with it.. when doing for real, Im using carbon paste on the clamp and rails, greasing the bolts (does it have to be that much grease since they are so big?) and maybe sanding the yokes as someone suggested.

tks, and sorry for my spelling!

[artray]

You could try putting some clear coat where your clamping , then you will not have to use so much force to tighten.

[motorthings]

and a ball-end allen socket works wonders for tight fits like that.

i made one from a L shaped allen, cutting off the short end, and dropping the non ball-end into a socket of the right size.