Re: Suspension losses

On 1/2/2025 5:45 AM, Roger Merriman wrote:

Frank Krygowski <frkrygow@sbcglobal.net> wrote:

Good article from Jan Heine on benefits of wider, softer tires for
absorbing vibration and lessening suspension losses:
>
https://www.renehersecycles.com/the-missing-link-suspension-losses/
>
At the time the rumble strip test was published, I expressed some
skepticism because its roughness is fundamentally different than the
random roughness of either a rough road or a gravel road. In particular,
the rumble strip is all "negative," cut into the smooth surface, while
rough or gravel roads have both "negative" holes plus "positive" patches
or rocks that protrude above the surface. One practical difference is
that when dealing with only "negative" roughness, higher speeds reduce
losses. The opposite is true with "positive" roughness.
>
But I suppose for demonstrating the fundamental effect, the consistency
of the rumbles is useful. And the measurements seem valid as long as the
test speed is also consistent.

 Not that convinced to be honest, for a starters folks aren’t going to be
riding rumble strips but by mistake!
 And if you’re going to be real world testing, testing on dirt roads with
all of the inconsistencies that brings is what gravel riders do. With the
dips as well as the bumps, plus ruts etc.
 Rumble strip testing seems somewhat misleading ie it’s not that controlled
nor what riders do.
 As ever claims that they influence pro athletes etc and started the wider
tire use, IMO it along with disks was adapted by consumers/commuters with
pro racers lagging behind with adoption and haven’t gone quite as wide, ie
stopped at 28 for the Pros where as 30/32 are fairly common among club
riders.
 

>
BTW, Jobst Brandt is mentioned in the article. I recall that in
discussing rolling resistance here, he insisted that "rolling
resistance" should be defined _only_ as the losses generated by tire
rubber's hysteresis. I disagreed, because that implied that solid rubber
tires a la 1880, or near infinite tire pressure, or even metal rims with
no tire, would be best. Anyone who has ridden an antique solid tire
"safety" bike knows how slow those tires were.
>

 As ever is a what you want as well, on the old school road bike, I commute
on, 28mm felt on the twitchy side 32mm much more planted, the speed
difference I’m less concerned about, though at that level maybe wider is
faster? What is faster would depend on road/bike/rider.
 Roger Merriman
 

I don't have a coherent argument either way but a rumble strip test introduces a repeatable experience so that various data may be compared.  Each rider on a dirt or gravel path, and each ride experience by any given rider, is an unique set of impedimenta such that data cannot be as readily compared.
In short you make an interesting point but it's not measurable for comparative purposes.
--
Andrew Muzi
am@yellowjersey.org
Open every day since 1 April, 1971