|Now that I'm fitted... do I really have to go custom?||SJMatt|
Jun 20, 2002 10:42 AM
|Going through the whole fitting process on the Serotta machine was great. It makes it so much more clear how to approach finding the right bike.
But alas, there was one little detail that I do have a question about. Apparently, I have something of a long femur (back off ladies, I'm a married man) for my body size.
Stock bike geometry typically has a 73.5 to 74 degree seat tube angle (for a 54 cm frame), and I would be properly fitted at 72.5 to 73 degrees. The effect of this is that on a stock bike, my knee is out ahead of my foot when the crank is parallel to the ground.
So, for a "proper fit", I should be getting a custom bike. I haven't even been looking at custom bikes up to this point, and there may be a wonderful world out there for me to discover now, but what I'd really like to know is how significant would this "problem" be if I was on a stock bike?
Is the problem only going to be a loss of pedal efficiency? Will I find some discomfort on long rides? Is it likely to actually cause me pain and injury? I know that TT bikes have a much MORE agressive tube angle, so is this slightly forward position not as big a deal as other "fit"-related issues?
Any and all opinions appreciated.
Jun 20, 2002 10:55 AM
|It comes as no surprise that a Serrota size cycle told you that you needed a custom bike, but you don't.
Unless I'm completely missing something (which would be because you haven't told it), you should be able to get KOPS by using a set-back seat post (ala Campy Record), and jamming the seat all the way back. The top tube length can then be compensated for with a different (shorter) stem length. You'd have to be really disproportionate to make this impossible, and I don't think I've seen anybody in the 54cm bike range that's a complete mutant.
Some people really stress out about STA, but in reality, seat tube angle can be manipulated pretty effectively by using different seat posts and saddle rail positions. My rudimentery trigonometry shows that moving the saddle back by 1cm, with a 54cm seat tube, would yield a change from 73.5 degrees to 70 degrees- so you can see that you have quite a bit of leeway. (Having not taken trig since 8th grade, I only have ~85% confidence that this is right- but it is close.)
Jun 20, 2002 11:15 AM
|The whole seat tube angle thing has always baffled me. The angle may impart some ride characteristics, but as long as you can get your seat in the correct location, does it really matter? Slacker seat tube angles only move the seat further back if you don't move the seat on it's rails. I have bikes with 72.5 and 74 degree seat tubes, and I can achieve the KOPS position on both bikes using a straight seatpost. All i have to do is slide the seat forward or aft on it's rails.|
Jun 20, 2002 11:48 AM
|you can probably get to a perfectly reasonable body position by manipulating seatpost, crank length, and stem on a standard non-custom bike. A good place to start is on a bike with a slack seat tube, but you can probably work it out on any bike without a long top tube. Doesn't the Lemond line have a laid-back seat tube?? Just thinking out loud here....
I have seen and heard the opinion expressed that it really doesn't matter if your knee is directly above-it has merely been a traditional starting point when fitting. I do know that if you go too far one way or the other way-your foot out ahead of the knee, for instance, that it might create a problem, but everyone is different, and perhaps others wouldn't have been as bothered as I was. Still, there is a darn good chance. you can get a comfy, efficient, all-day-in-the-saddle postion w/o a custom job.
I like to be back a bit farther on my bike, anyway, for riding the twisy bits of road. I do slide up as needed, but I enjoy being back there a bit. The rear wheel doesn't lock up as readily, and that can be unwelcome at times.
Additional component ideas: Thomson makes a lay-back seatpost that is first class, and there are any number of long saddles that give you a wider (longer?) range of positions on the bike to cover various conditions. I have been using the Selle Italia seats like the TransAm/Max/Prolink series and I like all of them. When you slide forward there is still something to sit on and lean on your legs for control while manuevering.
|Why change seatposts when you can buy a whole new frame?||djg|
Jun 20, 2002 12:10 PM
|No, wait, I pretty much agree. There's a pretty broad range of available set-back between normal posts. Start looking at special posts (like the Thomson set-back post or the Look Ergopost) and you open up even more possibilities. KOPS may or may not be what you are looking for. And I'm not saying you wouldn't enjoy a custom frame from a good builder. But if the only "problem" is that a standard STA and a standard post leave you wanting a couple extra cm, that is easily fixed by changing posts.|
|agree on post||cyclopathic|
Jun 20, 2002 7:25 PM
|1deg corresponds to 10mm offset with 610mm BB to saddle top. You get ~60mm of rail space to play with, plus seatposts have up to 1.5" offset. And if it isn't enough, take a look at this one|
|re: Now that I'm fitted... do I really have to go custom?||VW|
Jun 20, 2002 12:22 PM
|Hi, me again!
You mentioned in previous post that you already had a few bike in mind before your bike fitting. I'm not sure what they may be, but I found LOOK makes frames with very slack seat angles (72.5 degrees). Also, LEMONDS frames are 73.25 degrees (pretty close). Good luck!
|not enough info....||C-40|
Jun 20, 2002 1:10 PM
|I suspect that you may not have received the thorough fitting that is really needed to justify the extra cost of a custom. To be completely accurate the fitting should be done with the type of saddle, seatpost and pedals that you intend to use. The seatpost clamp and saddle rail position can have a substantial affect on the STA.
You must also realize that STA and top tube length cannot be considered separately. A different style of seatpost or saddle can move the saddle back in the same manner as a slack head tube angle, but this movement ADDS to the top tube length.
If you find a frame with a 73 degree STA, add .6cm to the TT tube length to compare it to the TT length of a frame with a 72.5 degree STA.
As long as you can get the saddle in the proper position and obtain the desired reach to the bars with a mid-sized stem, you don't need custom.
Post some more specific info (TT length and stem length) for some more help.
|how important is weight distribution ...||koala|
Jun 20, 2002 2:50 PM
|in all of this? Or maybe the proper question is if its significant?|
|re: Okay, you asked, so here's the complete lowdown...||SJMatt|
Jun 20, 2002 2:08 PM
|First, I want to thank everyone. The feedback from my two posts related to fitting have really been outstanding.
Since "more information" was requested, I'll be happy to provide it.
Height: 5' 8"
Inseam: 81 cm
Size: 54 cm
Seat Angle: 73 to 72.5
Tob Tube: 53 cm
Tob Tube & Stem: 63 cm
Crank Length: 170 mm
Seat Height: 73 cm
It looks to me like something more important than seat angle would be the length of the top tube. The 54 cm bikes I've looked at have typically had a top tube 54 cm or larger. I'm very concerned about feeling stretched out and getting shoulder and lower back pain. Someone pointed me to the Look specifications which do indeed show a very slack seat angle, but I notice the top tube is then notably longer.
The bikes that I've been looking at (this is all pre-fitting) are the Trek 5200 and Litespeed Tuscany.
So there it all is - hmmm... might I be able to elicit some opinions?
|re: I have a 55cm Litespeed Catalyst in the classifieds for sale||litespeedcat|
Jun 20, 2002 2:38 PM
|It is Ultegra with a new profile AC fork, Cane creek s-5 headset, Dura Ace rear derailure, and will have a set of new (never ridden) Velocity Spartacus wheels. I'm asking $1699 or best offer and I am will ing to split the boxing and shipping expenses. Let me know if you are interested. The frame looks new except for the stickers (normal rack mount wear, saris B.A.T. rack). Send me an e-mail email@example.com|
|re: the bike above comes with a new Look Ergopost as well!||litespeedcat|
Jun 20, 2002 2:41 PM
|That will give you plenty of adjustment.|
Jun 20, 2002 2:50 PM
|First, are you sure about each of those numbers, particularly the top tube and top tube + stem lengths? I'm about the same height and inseam, and my top tube + stem (yes, confirmed by a Fit-Cycle fitting) is 66 cm. And I'm not very flexible, so that number should be close to "normal" for someone with "our" height and inseam. The difference between 63 and 66 cm would be very noticeable, in terms of comfort and efficiency, and would substantially affect your position on the bike. So if 63 cm is substantially different from your "usual" top tube + stem set-up before you had a fitting, be careful about relying on that number. Especially if you're thinking about buying a very pricey frame.
Other than that, there are differences between the Trek OCLV and Litespeed geometries (I've ridden both). The Trek seat tube measurement is a bit odd; what they call a "54 cm" frame is more like 51 cm center-to-center, though it has a top tube of 54.5 cm. It's a very long top tube for that seat tube size, which is why nearly every 5200/5500/5900 you see in a showroom has about 5 or 6 cm of spacers between the headset and the stem -- because they're putting people on a shorter-than-normal frame to get them to fit a "normal" top tube. At your size, you probably can't fit on Trek's "56 cm" frame because the top tube will be way too long, so you'd have to ride their "54 cm" frame and use a lot of spacers, like the bikes in their showroom. It's not "wrong", but it is something to consider.
The Tuscany has a more normal "American" geometry. Their "53 cm" frame is actually 53 cm center-to-top and about 51.5 cm center-to-center. With a 54 cm top tube, it should be compatible with your size. (Again, I think you need to double-check your top tube + stem measurement.)
My personal opinion is that the Tuscany has a better road feel, and the frame should last close to forever, and I think it's a better choice if you only have enough $$$ to get one or the other and not both. But it is just my opinion. If you love the feel of the OCLV frame, and it fits you well, and you're gonna want to ride it every day, then go for it. Good luck.
|you're close to my size...||C-40|
Jun 20, 2002 3:46 PM
|I'm 5'-7" with a longer 83cm inseam, which means I have a shorter torso, but still ride a 54.3 TT/74 STA or a 55.5 TT/73 STA (they fit the same). I also use a longer 11cm stem.
I restrict my c-t frame size to 54-55cm.
Double check your inseam using a bike as a measuring tool. Block up the wheels until you get saddle like crotch pressure when you stand over the bike in bare feet. The distance from the floor to the top of the top tube is an accurate cycling inseam. Shoot for 3-5cm of standover clearance in bare feet.
Also consider possible future changes to your knee position. If you haven't experimented with it before, just remember the setting the knee over the pedal is just a starting point. I place mine nearly 2cm behind the pedal spindle.
|Try a bike set up that way||kenyee|
Jun 20, 2002 6:54 PM
|...that's what Ben Serotta suggested I do after I said I had a really weird fit result. Go back to the shop and ask them to configure any bike they have on the floor to match your fitting and go for a test ride and see how it feels.
You're actually pretty close to a square 54x54 (c-c) frame. There are a few companies that make stuff in this size: Serotta, Colnago, Gios, Aegis for a start. Trek/Lemond seem to like long top tubes (there was a discussion on how Lemond convinced all american makers to do this about a week ago, so you might want to look it up).
If you find a 54x54 frame, all you have to do is bump the stem size down 1cm (standard is 11cm) and you'll have your 54x53 size. Should be trivial for the shop to set up this way on a 55cm Colnago (they're C-T) MXL or a 54cm Serotta.
|re: Okay, you asked, so here's the complete lowdown...||VW|
Jun 21, 2002 9:22 AM
We are almost exactly the same size! I still have not pull-the-trigger and get the Serotta fit, but it seems my bike set-up is pretty much the same as your fit numbers.
I'm 5'8 inches with 80.5cm inseam.
I use a 172.5 crank length. My seat height might be a little short at 71.5cm ... but I'm a spinner, longer crank length, and my Speedplay pedal might be a little lower than the standard setup.
Currently, I'm riding with top tube plus stem at 63.5cm and I think I might be a little stretched. I think 1cm shorter would be ideal for me. I just checked my riding position on a mirror the other day, and I found my back is a little bit less than 45 degree (more flat back) when I'm on the hood. I'm about 45 degree when I'm on the handlebar top with a slight elbow bend. No wonder I feel most comfortable on top of the bar!
I agree with the guy posted above saying Trek has long top tubes. I'm currently riding a 54cm Trek OCLV with tons of spacers at the stem so I wouldn't kill my back. I am looking to replace the OCLV frame with one that has a shorter (effective) top tube, so that I can have a larger frame. Yes, the LOOK frame does have longer top tube, but the 53cm effective TT length (taking into account of the slack seat tube angle) is 1.2cm shorter than the current setup on my 54cm OCLV, 0.7cm shorter than a 53cm Litespeed Arenberg (I don't think Litespeed sells a 54cm), and 0.4cm shorter than a Colnago C40. I think the Tuscany has the same up-front geometry as the Arenberg.
Don't trust my calculation though ...do your own. My calculation took into acount of seat tube angle and head tube angle. I assumed the handlebar is 3cm below the seat. I also made other assumptions that I have no desire to explain or defend.
|assuming you really are fitted||ET|
Jun 20, 2002 2:22 PM
|I do not take for granted as many here do the accuracy of the Serotta size cycle fitting. I had it done, and yes, by a certified tech who is also the owner of an LBS and an avid racer, and a bike legend to anyone who knows him. Gave me almost three hours of time. I too was told that I needed something in the 72 to 73 range, but don't dare go over 73. Bought a Lemond 57 c-c with a 72.5 STA upon his recommendation. After riding for a while, it turns out my STA is really more like a 73.2. Now how can that be, you ask? Well, for one thing, the seat only started hurting me later. So for the stock setback my saddle is now pushed forward around a cm on its rails. And the size missed by several: while the tech even wanted me to consider a 59 c-c (I'm 5-9, 84.2 CC inseam), I refused, valuing my family jewels among other things, and my true size should be more like a 55 c-c. So the size cycle fitting wasn't really close, certainly not for $100. The bikes's not a waste, though: I came down one stem size, and due to very good flexibility, I can reach, although it's a stretch to the brakehoods.
Sure the size cycle, with infinitely adjustable everything, is a great idea in concept. But just riding for a while, e.g. on a previous cheaper purchase or friend's bike, is a better idea, and then a little math savvy or help from someone who has it and you can zone in better for future. Many seem to take the size cycle as gospel to buy their first road bike (on this forum, typically a Vortex or Legend--why not the best?) based on it.
For first timers there are easy guidelines I claim for the most part are just as good if not better than the Serotta size cycle (I posted them a while back--there are very good instant rules of thumb even for things like top tube length that will get you very close). People have posted a few sites that give good starting points too upon entering some data.