The Analyzer Presents: Top Fuel Diet Series Seat Post and Clamp

As I mentioned last week, I’m going to ORAMM this summer and I’ve never climbed 10,000 feet before. I heard it’s better for climbing if you’re carrying less weight so I decided to put myself and my bike on a little diet to see how much weight we can shave off before the trip. Week one of putting my Top Fuel on a diet includes replacing the seat post and clamp. Here we go!

As this is the first in the series, we’re going to take baseline weight for the bike.  When I bought the bike I made a few tweaks: Swapped the Bontrager XR1 Team 29×2.2 tires for Specialized Renegade 2.3’s setup tubeless of course, stock Bontrager Grips for ESI Chunky grips, and dropped the SRAM X1 trigger shifter for a SRAM NX grip shifter. Adding a carbon bottle cage and a set of ISSI Flash III SPD pedals gives us a baseline weight of 24.14 pounds (10.950 kg).  This is how I raced and trained on the bike over the last 6 months, and the bike was good enough to get the CAT 3 series win in the Florida Endurance Series so I certainly can’t complain about that.  

During my first few months with the bike, I thought I might like to have the option to move a little further back when descending technical sections.  Instead of installing a dropper post, I decided to go with a 20mm Setback post.  As I previously had my saddle towards the end of adjustment range on my zero offset seatpost, this setback seatpost should give me a little more usable range of adjustment.  

The stock seatpost with the bike is the Bontrager Pro OCLV 5mm offset carbon seatpost, 31.6mm x 400mmm.  This carbon post weighs 272 grams on my scale, which isn’t bad for a stock seatpost, but is probably on the heavier end for a carbon fiber seatpost.  Since I wasn’t sure I would like the setback post, I didn’t want to spend $200+ for a beautiful Bontrager XXX or Enve seatpost.  I ended up going with a Hylix 31.6mm x 400mm setback post from Ebay.

It took 2 months to get here, got lost in customs, but it finally arrived as advertised.  At 183 grams it’s a pretty competitive option for under $60.  I’ve run Hylix posts on a couple other bikes and had great luck with them.  Swapping this post from the stock post saved 89 grams while giving me more usable adjustment range on riding position with a 20mm setback. 

While I was upgrading the seatpost, I looked at the stock Bontrager alloy clamp and thought there might be some opportunity there for weight savings as well.  Putting it on the scale showed it weighs 29 grams.  Since all the clamp has to do is hold the seatpost in place with ~8-10Nm of torque, some companies have developed some feathery carbon options.  I’d had good luck with carbon clamps using Titanium hardware with other bikes, so I ordered this 34.9 carbon clamp from Ebay.  At 12 grams, it does the same thing as the stock Bontrager clamp at 17 grams less, while looking quite sharp in my opinion.  

Two things to keep in mind when assembling carbon components is assembly paste and torque values.  I use Park Tool carbon assembly paste which has a nice fine grit to it ensuring the post doesn’t’ slip.  To make sure I’m not over torquing the carbon parts, I use the Tekton ¼ drive torque wrench which has measurements small enough for lightweight bike parts.  I’ve had a seatpost slip during a race, and I’ve broken carbon parts before from over tightening, so these 2 items are cheap insurance to prevent that from happening in the future.

So, for a total of $74, I was able to shave 106 grams off the bike while moving to a setback post to hopefully improve my position on the bike.  At $0.70 per gram, this is a baseline for the remainder of the Top Fuel Diet Series to see which weight saving options make the most sense.  This brings the bike weight down to 23.96 pounds (10.868 kg).  There’s something cool about getting under a whole number, so going from 24.xx to 23.xx in the first part of this series was pretty rewarding.  Can I get this thing to 22.xx pounds by the end (and before ORAMM)? I honestly don’t know, let’s find out…

 

Part Weight Difference Price $/gram
Hylix 31.8×400 Carbon Seatpost (eBay) 182g 89g $54 $0.61 / g
Carbon 34.9mm Clamp (eBay) 12g 17g $20 $1.18 / g
TOTAL 106g $74 $0.70 / g

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2 thoughts on “The Analyzer Presents: Top Fuel Diet Series Seat Post and Clamp

  • November 27, 2017 at 8:09 pm
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    Hello David,
    First of all congrats for the blog.

    I want to upgrade the seatpost clamp of my Top Fuel and i need to confirm the measure. Lot of places talk in 36.4mm but you refer 34.9.

    Which is correct?

    • November 27, 2017 at 8:11 pm
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      You know what, I bet it is the larger size. I was barely able to fit that clamp on there, so it makes sense it’s probably about a millimeter or 2 too small…

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