Will: What size tires on the Cannondale?
Just to confuse the issue, my Atlantis can develop wobbles going fast downhill if loaded more heavily in the rear than front. The Atlantis' mission profile is touring bike primarily and Rivs are said to be "rear loaders". My Atlantis came with full rear rack eyelets and no provision for a front rack, which suggested Riv meant it to carry the load in back. After years of touring & playing around with loadings, the most stable set-up is primary weight up front in low riders and lighter, bulky stuff (tent, sleeping bag, etc.) on the rear. Lodging tours only require front bags. Bike has Mavic A 719 rims (pretty heavy) and 35 mm Schwalbe Marathon Supremes. dougP On Aug 7, 9:24 pm, Will <wpm...@gmail.com> wrote: > Michael, > > Impeccable timing. Last weekend I was descending on my Rambouillet > and noticed something similar (tires = 700x27 Rolly Poly). Above 35 > mph, it's not exactly the shimmy/speed wobble you describe but an > unnerving twitchiness/skittishness in the front end. At speeds of > 40-50 mph descending 7 Colorado Rocky Mountain passes in 2008 the > Rambouillet felt so consistently twitchy that I was anxious making > even the slightest movements, like shifting hands from brake hoods to > drops. Lowering the bars 2 cm hasn’t helped. > > By comparison, the other bike that I've ridden for the past 12 years > is a 1998 Cannondale T1000 touring bike with rake, trail and wheelbase > specifically designed for loaded touring. This bike can descend any > grade at any speed with any load with motorcycle-like confidence. > > I realize that there are dozens of variables that effect front-end > stability (headset tightness, tires, wheels, rake, trail, wheelbase, > rider’s fore/aft weight distribution, winds, rider skill/experience); > I’d also be grateful to hear from others who experienced and then > dialed down the twitchiness/speed wobble/shimmy factor. > > Will > > PS Michael, it sounds like you were going *really* fast. I’ve > experienced such speed wobbles on motorcycles when going too fast, > especially motorcycles without steering dampers. Once the shimmy was > induced by a side wind; another due to irregular pavement. (Were > either of these issues?) I also wonder if you were squeezing the top > tube with your knees at the time (this is known to quell wobbles). > > On Aug 7, 5:37 pm, Jim Thill - Hiawatha Cyclery <thill....@gmail.com> > wrote: > > > > > It'd be interesting to lower your stem a little and try again. > > > On Aug 7, 2:37 pm, MichaelH <mhech...@gmail.com> wrote: > > > > In five years of riding my Rambouillet I have never experienced any > > > front end shimmy - until this morning. I was coming down VT 108 from > > > Smugglers Notch and as the bike hit 45 mph I shifted my hands from the > > > drops to the center, to get into a tuck, and all of a sudden I got > > > this slight, but unnerving front end shimmy. As soon as I returned to > > > the drops it quieted down. I have had this bike up to 50 before so it > > > wasn't just the speed. Clearly, shifting my weight backwards seemed > > > to unweight the front enough to cause the shimmy. I had an Acorn > > > Rondoneur bag on the front but it didn't have much weight in it. > > > > My son gave me a pair of Continental Grand Prix tires, which are only > > > 23 mm and have proven to me that they need to be up around 110l bs to > > > avoid pinch flats. That's the only difference I'm aware of. Has > > > anyone else run a Rambouillet with very skinny tires, and did you > > > experience any hi speed shimmy? > > > > Other than that, I'm feeling pretty good that I can still make that > > > climb (2800 ft up from my home). > > > > BTW, as I started up the mountain road I ran into three heavily loaded > > > senior citizens from, of all places, Walnut Creek! They spotted my > > > bike right away. > > > > michael- Hide quoted text - > > - Show quoted text - -- 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-bu...@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.
