Tri BIke Sizing Question (Shiv)

I have a 2010 Cervelo P2, size 56, that I am likely to be selling to a friend. I loaned it to them to try out, and don’t have the bike to take all the typical XY dimensions for fit. But here is what I know for now with regards to sizing.


  • I am 5’ 10" [178 cm], with 34" [86 cm] actual inseam length (Long Legs with a Short Torso).
  • The P2 has a 80 mm X +25 deg stem (short & high angle), and is installed with 25 mm of spacers between the HS cap and the stem.
  • Arm pads have the taller spacers (maybe 20 mm tall). I end up with about 70 mm drop from the saddle to the top of the pads, based on a 770 cm saddle height.
    • Pad X (center of the pad) = 460mm
    • Pad Y (top surface center of the pad) = 670mm
  • I have the saddle mount installed in the forward hole of the seat post.
  • Sitero saddle installed rearward with about 15 mm of the leading saddle rail exposed, and much more than that behind the clamp. Effectively a fairly rear mount location.
  • It fits, but might be a bit on the long side for the TT length.

I am looking at the Specialized Shiv Tri for the next bike and torn on sizing.
The Specialized chart has me on the bubble.

  • I know these are generally just a starting point for sizing.
  • I seem to remember reading on Slowtwitch forums that you usually size down when you are between sizes.

I made a geometry comparison between the Cervelo 56cm and the Shiv in Medium and Large. I am missing some info on the Cervelo since it is older and I have issues finding more detailed charts.

The Cervelo seems to be about in the middle of the Shivs for the most part.

I am looking for some guidance, as I have to buy without the ability to test fit in person.
I can get my Cervelo for more detailed measurements and pics of me on it for reference.

Thanks for any guidance you can offer.

Is there someone around you that will do a pre purchase fit? They put you on a performance cycle or guru or something like that and adjust it until your comfortable/position you want. After they have that it spits out dimensions/bike thats will fit you. Some places will take the price of the fit off the cost of the bike if you buy through them. I’d be a little weary of that because I’m paranoid they would make me fit one of the brands they sell but that’s probably unrealistic. Definitely worth doing if you have that option around you. I didn’t do that and it ended being much more of a pain in the butt and expensive.

Oddly enough, I am actually a fitter. I just don’t have access to an adjustable sizing bike to play with for testing. Best I can do is grab some random road bikes and try to match fit, and they are very different for seat tube angle.

No tri bikes on the floor in my shop or the local area in other shops. So I am left to go from current bike fit and comparing geo charts. I’ve done it with other bikes, but I know tri bikes far less than road and MTB.

Gotcha. Might be worth trying to find a shop with some sort of fit cycle. The measurements don’t really transfer all that well sometimes because of all the angles and the different contact points. I won’t buy another without getting pre-fit.

Hi Chad. I’m a similar height to you at 177cm. I have access to a great deal on a second hand current model Shiv Expert. It’s a medium.

What size did you end up going and how did it work out?

I am on the Medium and very happy with the sizing. I’m in the final stage of setup before finishing the build.

Thanks Chad that’s reassuring :slight_smile:

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Hi Chad. I have my Shiv now and did a fit on it, but I’m unable to get my elbows stacked under my shoulders on the medium using a 90mm -6 stem. I just ordered a 70mm -17 which should bring the pads a little closer. Since we’re similar proportions I’m wondering what size stem you settled on for your Shiv. So far I’m loving the bike and it handles really well.

I am on the stock 90mm stem, 1 main spacer under it. Here is a pick of the bike and saddle position (forward post and saddle), for reference

I agree, the bike handles really well. I love the upgrade from my old Cervelo.

Yours looks very tidy. Is your basebar level or tilted up slightly? I have some 60mm deep carbon hoops for mine not installed and I’m just about to install some 165mm cranks. Unfortunately, mine came with the steerer cut. My cables are a dog’s breakfast but I plan to do a Di2 update shortly.

Base bar is up, parallel with the stem (and it’s at -6). I can’t stand level as my elbows slide forward and I have to clamp on the extensions.

This tip up locked me into position with minimal effort, and has the benefit of better aero from the closed position that keeps more air out of my chest area.

Thanks for the props on setup. I tried hard to nail the position first on the trainer. Then optimized cables to match. I’m very happy with the final setup.

Sounds like some great wheels headed tour way to finish it well.

Thanks for sharing Chad. I’m going to try tilting my base bar too as I get a similar sensation to what you describe and I might not need that super short stem.

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Certainly worth a test. I find that most people I fit do like some up angle on the extensions and pads.

Edit, are you hiding a new 2020 Top fuel in the back? If so. I gotta hear how you like it.

Good spotting. A brand new 2020 Top Fuel 9.8. Hopefully first ride this arvo. I picked it up
at the end of last week and have been waiting for the local trails to dry out. I will provide a full review. I’d been hankering for an SB100 but when the new Top Fuel came out I thought it had even more on offer and pulled the trigger.

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Awesome. Congrats and I am excited to read your feedback on the bike. Enjoy NBD. :smiley:

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First ride on the Top Fuel

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Sounds a fair bit like the old 2016 Trek Fuel EX 9.8 I had. It was an awesome bike with similar specs. Only issues were the 2 x 11 drivetrain and heavy wheels.

This new TF looks really good.

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