Adam, have you weighed the wheelsets?
On Wednesday, April 7, 2021 at 12:52:34 PM UTC-5 lconley wrote:
> It is rotating weight that matters for acceleration. I could bore you with
> a bunch of physics equations or you could Google "rotational inertia" if
> you are interested - the rotational inertia is a function of the square of
> the distance from the weight to the axis of rotation (lightweight
> derailleur jockey wheels don't count for much more that non-rotating weight
> because of the small radius). Drag racers know it (look at the teeny tiny
> front wheels and tires on all manner of rear drive drag cars), autocrossers
> know it (serious autocrossers use the lightest wheels they can find),
> automobile manufacturers know it (the one commonality of the stock tires
> that come as standard equipment on most cars is that they are lightweight -
> better mpg on the EPA test results). Look at a Formula 1 or other racing
> car's wheels - are they relatively big or small diameter compared to the
> wheels you see on street cars? - they are small - they use the smallest
> wheel they can for the brakes that they use and that the rules allow -
> for a given tire diameter, the wheel-tire combination that gives the
> lightest weight uses the smallest wheel (talking automobile tires here). If
> you have ever ridden a Bike Friday or similar small wheeled bike, you know
> how "zippy" they are - smaller, lighter weight wheels.
> Taking 1 lb. off your wheels helps more than taking 1 lb. off your frame
> (or dumping 1 lb. out of your water bottle).
>
> Laing
> Delray Beach FL
>
>
>
> On Wednesday, April 7, 2021 at 12:36:48 PM UTC-4 philipr...@gmail.com
> wrote:
>
>> On Wednesday, April 7, 2021 at 11:11:44 AM UTC-5 Patrick Moore wrote:
>>
>>> I think I understand the concept of unsprung weight, but I thought that
>>> it affected handling, ie lateral forces and their control, and not
>>> acceleration; wouldn't a vehicle with a very great unsprung weight
>>> accelerate as fast on a horizontal and straight surface as one with very
>>> little unsprung weight? I am thinking for example of a bike and rider with
>>> suspension seatpost and stem, compared to a bike and rider with suspended
>>> wheels. Would the latter system have an advantage in simple straight line
>>> acceleration?
>>>
>>> Not that this is not (double negative!!) an interesting conversation!
>>>
>>>
>>> Yes, lots more to unsprung weight than just acceleration & my theory in
>> bicycles is loose as presumably part of the tire would have to be
>> considered as sprung depending on the construction? Also, the fork,
>> chainstays & the frame overall will flex (that lateral stiffness all the
>> bike reviews mention) so we should take that into consideration too.
>> Especially as Rivendell's penchant for steel (a fairly flexible material)
>> and long chainstays may impact that more than other designs. The math gets
>> PhD hard at this point but in the case of the OP the Salsa looks to be of a
>> similar geometry to the SH so we might be closer to apples to apples there
>> at least.
>>
>> For sprung weight the suspension (in whatever form) will absorb some of
>> the input force as deflection, binding/friction, shock aeration, heat etc.
>> so there is a disadvantage. The lighter the components acted upon by that
>> remaining force, the faster they can transmit that into acceleration. Many
>> modern race series allow some form of suspension lockout to aid quicker
>> starts ("holeshot" devices), a little Googling has informed me that some
>> MTB systems offer a similar process.
>>
>> The overarching conclusion here may also be that no suspension is better
>> than cheap or badly set up suspension.
>>
>>
>>
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