Got it; many thanks. Patrick, RR31 is 7 years old. We're up in the 40s now.
dougP On Dec 31, 8:25 am, David Faller <[email protected]> wrote: > Drink a little more coffee, Patrick... > > On 12/31/2010 8:15 AM, PATRICK MOORE wrote: > > > > > So RR 31 is out -- great, must buy it. Good article. Whatever G's take > > on trail, he's built me three excellently handling bikes. > > > On Thu, Dec 30, 2010 at 9:50 PM, Bill Gibson<[email protected]> wrote: > >> Did you know the pdf author was Milhouse Vanhouten? Cali is a mythical > >> place, you know...I have it, but I bought the pdfs from Rivendell...I > >> hesitate to violate copyright , but I will quote, assuming you are a loyal > >> customer..."Experiments With Rake& Trail" > >> Fork rake is how much the front wheel is offset from > >> the steering axis a straight line through the center of > >> the head tube. The aspect of the bike s steering geometry > >> that s affected by fork rake is called trail. Don t confuse > >> it with a trail you ride on. > >> Road bikes typically have between 2-inches (50.6mm) > >> and 2 1/2-inches (63.5mm) of trail, and bike journalists > >> who ve written about trail have said 2 1/4-inches > >> (57/58mm) of trail makes a bike not too quick, not too > >> slow, just right. > >> Trail theory says that more trail makes a bike easier to > >> control at high speeds and over rough ground. > >> Mountain bikes typically have between 2 3/4-inches > >> (69.8mm) and three inches 76.2mm) of trail. > >> Less trail, according to theory, makes a bike easier to > >> control at slow speeds, but harder to control when > >> you re going fast, hitting bumps, or both. > >> Trail is affected by: (1) the wheel radius; (2) the head > >> tube angle; and (3) the fork rake (offset).There are three > >> ways to increase trail: > >> Bigger front wheel. > >> Shallower head tube angle. > >> Less fork rake. Most folks who start thinking about > >> trail temporarily get confused at least three times, and > >> think more rake makes more trail. Nupe. > >> To calculate trail using arithmetic: > >> Trail = Wheel radius/Tan. of head tube angle minus > >> fork offset/Sin. of head tube angle. > >> If that s Greek to you, we should be in the same club. I > >> have it programmed on my computer here, so I just > >> plug in the numbers and there you go > > >> How Trail Affects Our Frame Designs > >> When I design a Rivendell, I find the typical tire the rider > >> will ride, and then the biggest. For all-purpose road riding, > >> I shoot for 60-61mm of trail with the most common > >> tire. That s more than what experts have said results in > >> neutral handling, but they are not the boss of me. Nor > >> should they be of you! > >> Then I see what the trail is with the largest tire. Normally > >> a customer will say, I ll ride a 700x28 most of the time, > >> but there are some fire roads here, > >> and I ll ride 700x35s when I go > >> there. Well, that works out just > >> fine, because the bigger tire will > >> increase the trail, making the bike > >> better for the fire road (so goes trail > >> theory). > >> Most frame designers have a trail > >> figure they re comfortable with, > >> depending on the bike s intended > >> purpose. But some copy other manufacturer s > >> geometries not a bad > >> thing to do, and I hope we haven t > >> reached the point where somebody > >> out there considers Xmm of trail to > >> be intellectual property. Finally, > >> some builders just know from experience > >> what works, and don t think about trail. That s > >> fine, too! > >> In Italy in the 80s it was common for the top makers to > >> put 45mm of rake on each fork, regardless of the > >> frame s head tube angle. The big bikes, which almost > >> always had steeper head tubes, didn t have much trail, > >> but the little bikes (with slacker head tubes) had more > >> than plenty. I wouldn t say that s all that fine; in fact it > >> seems odd to me. But these same Italian frames were > >> ridden to many prestigious victories, which will impress > >> those in the results speak for themselves camp. I m in > >> the trail doesn t win races camp. > >> When you first learn about trail, you may find yourself > >> getting obsessed. It happened to me and I ve seen it happen > >> to others. Trail is interesting, but it is not the sole > >> splainer of bike handling, something nobody knows better > >> than Waterford s Marc Muller (more on him later). > >> The Educational-Type Fun Begins > >> FOR ABOUT SEVEN YEARS I VE WANTED to experiment with trail > >> by getting some forks with adjustable rakes, so we did. > >> We also got non-adjustable forks with no rake, and with > >> 65mm (whopping lot) of rake. You can do that when you > >> have your own bike company and a publication to get > >> out, but it takes more than snapping your fingers. > >> The bikes are 59cm Romuluses. The Romulus is a road > >> bike with what I think is a perfect geometry for allaround > >> road riding. Pertinent to this story, it has a 73- > >> degree head tube with 42.5mm of rake, which, with the > >> stock Ruffy-Tuffy tire (343mm radius), results in 60mm > >> of trail. It is as familiar to me as it gets. > >> We equipped three bikes with different forks adjustable > >> rake, 0mm rake, and 65mm rake; and of course we have > >> a normal one, too (42.5mm rake), so really, four. I rode > >> it up and down Mount Diablo and the local streets and > >> roads. I rode it loaded and unloaded, on smooth and > >> rough ground, holding onto the > >> bars like you re supposed to, and > >> no hands; over speed bumps (with > >> hands and no hands), with a heavy > >> basket, and at different speeds. > >> The Problem With This Test > >> It combines objective numbers and > >> subjective feelings, and what I feel > >> may not be what you d feel, because > >> maybe we re used to different > >> bikes, or one of us is more sensitive > >> than the other. Also keep in mind > >> that describing bicycle handling > >> with normal language isn t always > >> satisfactory. What I call quick > >> might not feel so quick to somebody > >> who s used to a 1987 64cm Ciocc (rhymes with > >> poach ) Italian racing bike, for instance. > >> Then this: I headed into this test knowing it would make > >> a Reader story, and I found myself looking harder for > >> things that I might not notice normally. I went out hoping > >> to find hugely noticeable differences, and any > >> nuance of the bike that suggested that got pounced on > >> promptly and may be overplayed. I m not saying I couldn t > >> tell a difference, I m just saying there s a natural tendency > >> to overstate the differences for the sake of a good > >> story, even when I m aware of that phenomenon. > >> But After All That, Here s What I Think > >> I could get used to any bike here. Off the bat I d say I d > >> have a harder time getting used to a bike with too much > >> trail than I would to a bike with too little, but bikes are > >> fun to ride no matter what, so I d get over it. > >> Also, I suspect the differences in the extreme versions > >> tend to get neutralized when you re on the bike manhandling > >> it. I think this because the biggest difference > >> came out in no-hands riding the low-trail bikes were > >> easy to ride at slow speed, where the tons-o -trail bikes > >> were hard; and at high speeds it was just the opposite. > >> But at slow or high speed, as long as I had my hands on > >> the bars, it didn t seem difficult either way. > >> As a bike designer, I find that quite comforting, but I still > >> work hard to thread the needle. (Go to the next page now.)... > > >> There's lot's more and pictures that explain a lot, so if Grant& co. give > >> permission, or if we can do this in secret with nobody seeing... > >> or buy Part No. 24-127, RR 26-35! > > >> On Thu, Dec 30, 2010 at 9:21 PM, doug peterson<[email protected]> wrote: > >>> Does anyone have this as a PDF? Specifically looking Grant's article > >>> on the eternal trail question. The Atlantis& I have been out messing > >>> with loading again....the things you start mulling about during > >>> winter... > > >>> dougP > > >>> -- > >>> You received this message because you are subscribed to the Google Groups > >>> "RBW Owners Bunch" group. > >>> To post to this group, send email to [email protected]. > >>> To unsubscribe from this group, send email to > >>> [email protected]. > >>> For more options, visit this group at > >>>http://groups.google.com/group/rbw-owners-bunch?hl=en. > > >> -- > >> Bill Gibson > >> Tempe, Arizona, USA > > >> -- > >> You received this message because you are subscribed to the Google Groups > >> "RBW Owners Bunch" group. > >> To post to this group, send email to [email protected]. > >> To unsubscribe from this group, send email to > >> [email protected]. > >> For more options, visit this group at > >>http://groups.google.com/group/rbw-owners-bunch?hl=en.- Hide quoted text - > > - Show quoted text - -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. 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