I'm trying to figure out the right frame size for a possible next bike-project. I want a "Rivendell fit" with bars about level with saddle, and somewhere around "a fistful" of seatpost showing. I'm about 5ft 10in tall; PBH is 86cm in bare feet, 87cm in my SPD bike shoes; preferred crank length is 172.5 or 175mm. Saddle height on current bike is comfortable at ~77cm.
I'm reading Riv's fit guidelines at http://www.rivbike.com/article/bike_fit/choosing_a_frame_size and am finding some confusing points. Starting from "How to Size any Bike, Including Ours", they use an example PBH of 85cm, and suggest that a corresponding saddle height is 75cm -- or 10cm less than the PBH. So far, I'm OK with that: my saddle height is around 10cm less than my PBH (especially accounting for my shoes). Next Riv suggests that a good bike size is saddle height minus 15cm. In my case, that's 86cm - 15cm = 61cm, or accounting for shoes, 87cm - 15cm = 62cm. Again, I'm in agreement with that: Most non-Riv 62cm frames I've straddled have been a bit "snug" but not overly so in standover height -- that is to say, the top tube touches but not dangerously so. And I could definitely fit on a 60cm frame, but I'd need a taller quill stem, or some extra spacers in a threadless setup, and of course there'd be more seatpost showing. Now, on to the next section on Riv's page: "Sizing Rivendells (the bikes we design)".... If you look at the frame-size chart they provide, for 86-87cm PBH measurements, they recommend 59-61cm frame sizes! Here's where I'm confused -- most Riv frames have a lower BB than a typical/average frame, up to 1cm lower. Most of Riv's sizing theory says something like "you can straddle a bigger one-of-our-bikes than one-of-theirs", so I've always thought that a correct Riv size would be 1cm larger than a "typical" frame size (and by typical frame I mean 1980's UJB steel frame or similar). Taking the previous frame size result of 61-62cm, that'd put me on a 62-63cm Riv. HOWEVER that chart points to a 59-61cm Riv frame for my body size -- which is SMALLER than the first recommended "normal" size, and frankly sounds too small! For example, the 61cm AHH has an 8cm BB drop and standover is just under 87cm -- that'd maybe be slightly too big for me (no clearance, since it's the same as my shod PBH). I guess the "Riv Size = usual size + 1cm" formula doesn't directly apply to the AHH because the larger tires cancel out the added BB drop? The 59cm AHH frame has 85cm of standover, which seems about right (about an inch of PB/TT clearance)...BUT a friend of mine rides this size, and he's always been on shorter/smaller bikes than me...so a 59cm sounds too small somehow. In contrast, the 61cm Atlantis has a standover of 85cm, so that'd fit me with the right clearance. Why that frame would fit but the same-size AHH wouldn't, isn't clear to me -- looking at their geometries, both have the same BB drop, similar size tires, the same seat-tube angle, and both have slightly-sloping top tubes. The Legolas frame is more typical since it has a standard 70mm BB drop. (Ignoring the fact that it's intended as a CX bike, which might indicate more-than-usual SO clearance) I could ride a 62cm size since its standover is 86.2, but clearance might be tight. The next smaller size is 59cm with 84.3cm standover. The Quickbeam frame is also fairly "normal" with a 73mm BB drop. The 62cm frame size has a standover of nearly 87cm (too big), but the 60cm size's SO is about 85cm. Now let's compare those data points with a fairly typical non-Riv steel frame: A Surly Pacer (level top tube, 72.5-degree seat tube angle, 72mm BB drop). The 62cm frame size has a standover measurement of just under 86cm, and the 60cm size's SO is 84cm (based on 700x25mm tires). Riv's Rambouillet frame has similar values at the same sizes. Overall, it sounds like I could ride a bigger Pacer frame than most Rivendell frames -- which seems utterly counter-intuitive to me, since most Riv frames have lower BBs! If anyone has a PBH of 86-87cm, I'd be very interested to hear what size frame(s) you've chosen (both Riv and non-Riv) and why. Thanks! -Jim G --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To post to this group, send email to rbw-owners-bunch@googlegroups.com To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en -~----------~----~----~----~------~----~------~--~---
