GP on upcoming rivbike fits, sloping top tubes, trail, flex, rolling resistance - RBW Owners Bunch

Message from discussion GP on upcoming rivbike fits, sloping top tubes, trail, flex, rolling resistance

Murray Love

More options May 16, 1:24 pm

From: "Murray Love" <murray.l...@gmail.com>

Date: Fri, 16 May 2008 10:24:05 -0700

Local: Fri, May 16 2008 1:24 pm

Subject: Re: [RBW] Re: GP on upcoming rivbike fits, sloping top tubes, trail, flex, rolling resistance

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On Fri, May 16, 2008 at 9:29 AM, Ryan Watson <rswat...@nyx.net> wrote:

> Thanks for posting this.
> Lots of topics that interest me in this one!

> On Fri, 16 May 2008, CycloFiend forwarded what Grant P. wrote:

> > Trail is a stabilizing force, which means to some extent is can
> > make a bike safer to ride, less easily jostled-to-crash than a bike with
> too
> > little of it.

> I think he's got that backwards. Lower trail seems to be less bothered by
> jostling. I noticed that comparing my Bleriot to my Kogswell. The B was
> much more likely to get "off course" (due to wind, accidental bumping
> of the bars, inattention, etc) except at very high speeds, where
> they seemed equally stable, but with distinctly different feel. I've yet
> to crash on either one.

Agreed. Less trail = a less perturbable front end, but also requires
greater steering input to effect a change in direction. Having said that,
my current favourite bike ever (edging out the RB-1 on the versatility
front) is my '84 Specialized Sequoia, which has medium trail (~55mm) and
handles perfectly well. All else equal, I prefer lower trail, but it's not
the first thing I look at. These days, that would be...

> FLEX:
> > moderate frame. Too much flex is a problem when it causes "ghost
> shifting,"
> > which is real shifting caused by the fame flexing enough to move the rear
> > hub away from the upper pulley, resulting in the chain being de-railed
> to
> > the next hardest cog.

> I love flex and will never buy another stiff bike. Unfortunately this may
> rule out future Rivendells for me, unless I get a custom. Is this ghost
> shifting something unique to modern narrow 9-10
> speed clusters? I've ridden some very flexy frames up some very steep
> hills, but never had that problem with 6-7-8 speed systems.

I think Dave Mann over on iBOB reported ghost-shifting issues with his
early-80s 531 Treks, but he's the first to point out that this is probably
an effect of Trek using very light (probably .8/.5/.8) tubing on a very
large frame (he rides a 64cm). I expect the old ultra-flexy bonded-aluminum
Vitus 979s and the like might have experienced similar problems, especially
in larger sizes, but the typical non-OS bike feels perfectly solid,
especially in the regular tubesets and common sizes. My '92 RB-1 was
probably on the light side for steel production bikes in its size (59cm),
and never a hint of ghost-shifting.

Murray
Victoria, BC

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