Wednesday, January 30, 2013

Equipment - Thomson Ti Seatpost Bolts

In the off season I think about both small and large improvements I can make to the bike. Usually these things are much less significant than any improvement I can make to the nut that holds the seat down (aka me) but it's fun thinking about the technical stuff.

For me large things means things that usually impact aerodynamics, like wheels or a frame or maybe an aero road helmet.

I consider any weight savings over half a pound significant also, so being able to get a BB30 Cannondale SI SRM crankset, with a complete weight of about 675 grams, was a nice move from my then-current Campy Record cranks that came in at just under 1000 grams for a combination of the square taper BB and the cranks themselves.

For those keeping track every 45 grams is a tenth of a pound. 90 grams is two tenths. 225 grams is about half a pound. That's rough but it's close - it's 454 grams per pound so you can do the conversions on any weight savings you do on your bike.

A bonus on weight savings is if the weight savings transfers from one bike to another. Saving weight on a saddle that I might use for 5 or 8 years is better to me than saving weight on a chain that will wear out in a season or two.

Back in the day I used to really hone the stuff on my bikes, really push them to the limits. I experimented with drilling out chainrings (remember that Mike?) and found, to my dismay, that my drilled out chainrings were so flexible they were virtually unusable.

On the other hand I found that using lighter titanium bolts throughout the bike would save me about 100-200 grams. If I could replace some big steel bolts, at that time in parts like the bottom bracket bolts, pedal axles, or brake center bolts, then the savings would hit 200 grams. If I only did the surface bolts, like water bottle screws, cable anchoring bolts, stem bolts, stuff like that, then I'd be closer to the 100g number.

My current favorite post, one that I've been using since about 1997, is the Thomson Elite seat post. It's well designed, it's been through a few saddle failures, at least two crashes, and it's worked super well. It's reasonably light (just over a tenth heavier than the lighter Masterpiece), and I played with the idea of trying to lighten it up.

On the black Tsunami, with the integrated seat post set up, my Thomson lost a lot of weight when I cut it down to about four inches. For the now-red Tsunami I have something like 18 cm of post showing - cutting it down won't help much.

I looked at a set of Ti bolts for the Thomson. I don't remember what it saved, something paltry like 14 grams, but I put it in my favorites just so I'd remember it existed.

At some "incremental improvement" level it appealed to me. It worked with a number of my seat posts (I have at least three Thomsons in use right now). It transfers from bike to bike. It saves some rotating weight (because it's up high I notice significant weight changes in the saddle when sprinting).

All those things made it cool.

Then, at some point, I decided to clear out my favorites of all the nonsensical whimsical stuff I saved, like a pair of bolts that would save me 14 grams. I mean, seriously, I'll pee more than that before a race.

So imagine my surprise when a package showed up.

Ti bolts for a Thomson seatpost

Apparently I didn't delete it from my favorites but added it to my cart instead. In my standard "click-click-click" I didn't notice it in my cart and now walla, it's here at the house.

I'll install it. I mean, what the heck. Lots of anti-seize, lots of care, and some weighing before and after to see if it really saved me 14 grams.

And now I gotta check my order history because I had also put a wicked cool wireless Cannondale SI SRM PC7 equipped crankset in my favorites. $15 bolts I can excuse. $3500 cranksets not so much.


6 comments:

John said...

You could also replace the Thomson clamps that sandwich the saddle rails with lighter versions, I'm not sure if it's worth it, but heh.

I've seen them in Ti and also carbon, I'm yet to do it myself, the weight to price ratio just doesn't justify it for my CAAD9

Aki said...

You know I saw them too, in carbon. I'd rather replace the cleat bolts and two extra bolts on my shoes with Ti pieces. Like you I'm working with a "regular" weight frame so no 700 gram uber flyweight frame. For now though I just need to build the freakin bike.

John said...

How's the build on the new Tsunami going by the way? Haven't seen any updates online. I've been looking at them since I saw them on your blog, could be my next frame if the CAAD9 implodes.

How come you're moving away from the wheel cut-out? Weight and the tire-rubbing issue?

Aki said...

I'm getting the build done in dribs and drabs. I've been incredibly sick for most of the month and have only recently regained most of my mobility, limited by a particularly bad few weeks of back spasms.

Right now I'm in the middle of finalizing the brake caliper selection (I have an assortment laying around), I got a new set of Nokons (the old ones looked too beat up for a new build). I was hoping to get it done over the weekend but I had my hands full just doing regular life stuff.

I have to do the cabling, install the cranks (no biggie), and find one more head set spacer. After that it's just finalizing lever position, tape, and it's done.

I've decided to cut my forks a bit long and use a spacer on top. This allows the stem to have 100% clamp surface vs not clamping the top few mm. The problem is that I misplaced my cool carbon headset spacers.

Just to be clear the "new" Tsunami is the first Tsunami modded with shorter chainstays. I never built the orange Tsunami up after building the black one (I stole the parts off the orange one in SoCal) and I'd like to have two full bikes at hand.

The "new" Tsunami is about 400g lighter than the black one so that's considerable. It's a combination of a lot of factors but the biggest thing is the aero seat tube and all the work that's required to make that work. I think a non-integrated post would shave a lot of weight.

I also decided against my aero strategy on the black bike - not using bottles and using CamelBaks instead - so the aero is not as effective.

However I still think that the black bike has its redeeming features. My ideal bike would include many elements off the black bike including the internal cables (because it's easier to clean), the cut out seat tube (just because), the shorter chain stays (39cm on black vs 39.5 on "new"), and probably the aero down tube - it's lighter than the oval one on the "new" Tsunami and lends itself well to internal routing of the derailleur cables.

I would do a regular seat tube, not the integrated. I found I missed being able to mount both a taillight and a saddle bag - with one inch of seat post showing that's impossible. I'd also increase the chainstay diameter/size as much as possible, reduce the seat stay as much as possible (try to increase stiffness without compromising ride), and I'd want to see if there's any way to shorten the head tube length, perhaps by doing an integrated version.

alloutofexcuses said...

Life does have a habit of getting in the way of things...At least it's still off season, you have a bit of time.

Day dreaming about a Tsunami frame, the aero down tube with internal cables would be pretty nice. What's that run? About $800? It would be interesting to go from the really beefy CAAD9 downtube to that (which is more like the aluminum Cervelo S1 with the aero shape I think?)

Speaking of cables, my front DR cable is stretched out AGAIN, I've been using regular bulk cable from the bike shop since the end of the season, this stuff just keeps stretching. Thinking of going with Yokozuna (decent price, Nokon is a little much for me ATM). Do you really see that much of a difference, I have the new style 105 shifters (cables under the tape) and I find they drag quite a bit.

Cheers

Aki said...

Sorry I forgot to approve the comment. Tsunami - yes, about $800. I don't remember what I paid exactly because I think that Joseph shortchanges himself and I try to add a bit more.
I'm still not done with the now-red Tsunami so I won't be riding it until either Saturday or the morning of the races on Sunday. Since I plan on bringing both bikes I can ride them both. It'll be interesting to note whatever differences between the two bikes.