seat tube angle

[veganeric]

I'm interested in getting my first tri bike. A LBS has a 2007 Specialized Transition Expert for about $1700. That seems like a pretty good deal for a DA/Ultegra setup. The only thing that has me worried is I went to another LBS that is more into the tri scene (MUCH more), and they (both times I've been in) insist that a tri bike have a 78 degree seat tube. The Transition, in my size, has a 75.5 degree seat tube. I have a hard time believing that Specialized would do this if 78 was THE magical number, as the other shop suggests. I know Trek has a more slack seat tube as well, and I've heard that is because it's designed more as a TT bike than a tri bike. Everything I've heard about the Transitions is that they are tri bikes, not TT. It seems odd to me that a knowledgeable shop would put so much focus on one aspect of a bikes geometry, rather than how the geometry as a whole works together. So what's the deal?

[HiYoSilver]

The 78 degree angle is based on saving muscles for the run and swim, it sacrifices a bit of power. The 76 degree angle is a tad more relaxed and uses more power muscles for faster riding. For tri events it would probably mean you'ld have a harder time on the other 2 legs.

NB: this is theory, I don't tri as swimming hurts too much.

You have your numbers wrong. Go to specialized and check. There isn't a 75.5 in any size. I see nothing wrong with the specs of the bike.

If you really want to know geometry issues, go to slowtwitch and read the technical articles.

[veganeric]

I understand the theory behind a steeper angle. That wasn't my question. My question is if 78 really is the magical number why did Specialized go with something other than that? According to this, which is the only place I've been able to find specs on the 07, they range between 76.75 and 75. http://www.thebikerschoice.com/instock_specialized_triathalon.htm

I just did a quick check and the horizontal shift between a 75.5 and 78 degree seat tube, with a 30" BB to saddle length, which is certainly longer than I'd need, is only 1.27" I have a hard time believing that is going to make a huge difference. I shift around on my road bike saddles a lot more than that. If the positioning is that sensitive couldn't I simply slide the saddle forward on the rails, effectively creating a steeper seat tube?

[geoffvsjeff]

I understand the theory behind a steeper angle. That wasn't my question. My question is if 78 really is the magical number why did Specialized go with something other than that? According to this, which is the only place I've been able to find specs on the 07, they range between 76.75 and 75. http://www.thebikerschoice.com/instock_specialized_triathalon.htm

I just did a quick check and the horizontal shift between a 75.5 and 78 degree seat tube, with a 30" BB to saddle length, which is certainly longer than I'd need, is only 1.27" I have a hard time believing that is going to make a huge difference. I shift around on my road bike saddles a lot more than that. If the positioning is that sensitive couldn't I simply slide the saddle forward on the rails, effectively creating a steeper seat tube?

First, 78 is relatively new for most big bike companies, because essentially what they have done in the past is take a TT bike and claim it is also a Tri bike, without focusing too much of the particular needs of each event. I know this is what Giant and Trek have done in the past, and this is part of the reason neither are huge on the tri scene. In both cases, in the last couple of years, that has changed as tri has become more popular, and their bike specs have changed accordingly. TT geometries are still more common (I think, I haven't taken a comprehensive look at brands' specs in the past year or so), so the geometry on that specialized doesn't surprise me that much.

I will guess you are going to Gear West. They are nice people, and they have good advice, but one question I would ask is: do you have a good road bike? If you have a good road bike, then you could throw a set of aero bars on the road bike and get nearly the same effect as the specialized. Therefore, if you do have a good road bike, then think more about getting a true tri bike with a 78 degree seatpost. If you do not have a good road bike, then I would strongly suggest getting a good road bike instead of a tri bike. A good road bike is significantly more versitile than a tri bike, and the performance differences are somewhat marginal. You are correct that there are methods (saddle position, angled seatpost) that will mimic a 78 degree seattube, so that should not be quite as big a deal as the one shop is making it out to be. That said, if you are after a true, dedicated tri bike, then frame geometry and that 78 degree seattube becomes a bigger deal.

Good luck

[Triguy]

First off, why the Specialized? $1800 is probably what the bikes MSRP should be(aluminum frame, stock basebar). The Cervelo P2sl is probably still a faster bike, nicer front end. If nothing else I would say try and save for a Cervelo P2C.

As far as Seat tube angles there is no magic number.

As of late I've been migrating my seat backwards and my run is still fast. I do believe there is a real difference between the two in
1. Comfort - slack riding allows me to get on my sit bones instead of my soft tissues
2. speed - aerodynamic subtleties between fore and aft positions such as:
a. overall, your back is lower because your saddle will be lower if it is farther back
b. elbows can typically be narrower if you don't have all your weight on them
c. it's easier to get your head out of the air and in front of your body which reduces your frontal area
d. eaiser to have shoulders farther in reducing your frontal area

I would still check out the Cervelo P2sl before commiting to the Specialized though.

Also talk with the guys at Gear West. No one knows triathlon more in Minnesota. They may be the ones telling you not to go with the Specialized but they do know their stuff.

[veganeric]

Thanks guys. I'll go check out the Cervelo at Gear West again. The other bikes in the Specialized price range seem to skimp on components though, particularly wheels. FYI the MSRP on the Specialized was $2400, similar to the P2C. While the Specialized may have a more TT geometry I still felt it working different muscles than my other bikes. Perhaps these are even more slack. While I don't remember the exact geometry, I know my old Lemond is very slack. I don't think the same is true of my fixed-gears. Anyway, I appreciate the advice. Hopefully a test ride on each will clear things up for me. For what it's worth, I don't plan on becoming competitive. I just want to do some tris for fun. Also, I was thinking of using this bike to commute on when the weather is nice. I realize that sounds insane, but at 32 miles each way cheating the wind as much as possible sounds good to me.

[WheresWaldo]

Lemond was notorious for slack angles and stretched out rider position. For Greg and his bikes it was all about comfort. If you didn't notice a difference between the two I would say there was something wrong with you. I find that as you mentioned a slightly steeper angle in the seat tube allows me to sit on my sit bones also. An additional reason TT bikes are slightly slacker than Tri bikes is the stupid UCI rule that forces the tip of the saddle at least 5cm behind the bottom bracket. This becomes much harder to achieve as the seat tube angle steepens.

Your last post is very telling, you are looking for an aero commute and only doing tri's for fun, I would suggest that until the bug has a firm hold take some of the other people's advice and try just adding aerobars to your Lemond. That accompanied with a zero setback or forward angled seat post and you can probably get in a very good tri position. When your disease has fully enveloped your very being then go out and get yourself the fastest tri bike you can afford.

[HiYoSilver]

The 08 ranges from 77 to 79 degrees, so they finally learned. Again if you check, the Euro's ride slacker and Americans ride steeper. If you're not consumed by the tri bug, it probably doesn't matter. But if tri is all there is, then the steeper angle riders average faster than the slacker angled riders.

[veganeric]

Let me clarify a bit...I do plan on taking triathlons serious, however my motivation is to have fun, not see my name at the top of the standings. A few years ago I was watching Kona on TV and told myself I'd do that by the time I'm 35. I realize a IM distance isn't something to be taken lightly, so I figure I better get working toward my goal ASAP (I'm 30 now). So, this year I plan do do a couple short tris and work up from there.

I appreciate all that suggestions that I could adapt my road bike to work. While I don't doubt that this suggestion would work just fine for where I'm at now, I'm hesitant to do this. To get a good tri fit I'd have to make changes that would be detrimental to my road ride. I don't want to have to spend half an hour wrenching every time I want to switch between a road and tri setup, and to be completely honest, I just want another bike.

Last night I went in to have the Specialized set up for me, so I can swing in tomorrow morning and take it for a test ride. He went through the whole fit, then stuck me on a trainer to fine tune it. I thought it felt pretty good but he wasn't thrilled about the fit. I certainly appreciated his honesty. It's good to know he is trying to get me on the right bike, not just make a sale. Anyway, we decided that I should really have a custom frame due to my odd proportions...short torso, really long legs and arms. Since that is out of my price range at the moment I'd still like to go with whichever off the shelf bike fits best. Perhaps in a few years I can throw down for a Landshark, Seven, etc.