Idle musings on what makes a bike ride 'smooth'

[NHAero]

I have work I should be doing but oh well...

This past week the weather has been perfect and I've ridden all four of my drop bar road bikes. I put the 700C wheels on the Bingham for the first time since the Supersix Evo Hi-Mod showed up in December. My totally subjective butt-o-meter says that the Supersix is a smoother ride than the Bingham.

Here's what's the same between the two bikes:
- Running 700Cx25 tires with light butyl tubes (GP5000 on the Bingham, Panaracer Agilest on the Supersix)
- Same carbon railed Bontrager saddle
- Same R9100 shifters
- Same Eggbeater pedals
- Contact points set up the same

So I sit on the bike the same and my body touches the two bikes with the same hardware.

Here's what's different:
- The Bingham is a relatively lightweight titanium frame made for me, with flat mount disc, and a Whisky No. 9 Road+ disc fork, whereas the Supersix is a very light, stock carbon rim brake frameset with matching fork. The frame geo is similar in terms of ETT and angles, the Supersix has a 20mm shorter chainstay and commensurately shorter wheelbase.
- The Supersix has a 25.4mm carbon seatpost, with less showing than on the Bingham with a Thomson Masterpiece.
- The Bingham has an Uno 90mm -7 stem, the Supersix has an Uno 100mm +17 stem. Bars are alloy Zipp XPLR on the Bingham, and Specialized carbon on the Supersix.
- Wheels on the Bingham are BTLOS 24/24 bladed spokes on 35mm deep carbon rims (22mm inner width). Wheels on the Supersix are Farsport Feder 20/24 bladed spokes 25mm deep carbon rims (21mm inner width).

The Supersix is my first carbon road bike and I kinda expected a harsh ride but it's just the opposite. And I feel that the rear end is more plush than the Bingham, less shock through the saddle. Am I feeling something real, and if so, what is (are) the cause(s)?

[eddief]

so you can keep making money to buy more bikes so you can keep wondering. don't lose your job due to idle imaginings. if you can really tell the difference between the rear end of two bikes you're a better man than I.

[fa63]

Many will agree that particular iteration of the SuperSix is one of the nicest riding bikes. I had one myself and found the ride quality to be sublime. While there isn't a lot of give/flex in a traditional double-diamond frame, there are things engineers can do with carbon layup and taking advantage of its anisotropic characteristics to make frames that are not only stiffer but can potentially ride better than a titanium frame. That doesn't mean titanium is bad; every material has its pros and cons.

That said, the Thomson Masterpiece is probably one of the stiffest seatposts in the market. You might want to try a different seatpost on the Bingham and see how it feels. The alloy vs. carbon handlebar could also be contributing to the difference, as well as the fork. Same for the wheels. Can you swap wheels between the two bikes and see if your assessment changes at all?

[Elefantino]

I'm waiting for someone to ask how you can ride on 700x25s.

[eddief]

it's the handlebar bag.

[thwart]

Since you mention the rear end specifically, the Thomson straight post vs a smaller diameter carbon post is likely playing a role.

Disc forks are stiffer than a similar fork designed for rim brakes. And at least IME carbon h’bars feel just a little ‘smoother’ than a similar aluminum bar. And 35 mm deep rims usually ride stiffer than a 25 mm rim.

Nice bikes either way.

[NHAero]

Originally Posted by fa63

Many will agree that particular iteration of the SuperSix is one of the nicest riding bikes. I had one myself and found the ride quality to be sublime. While there isn't a lot of give/flex in a traditional double-diamond frame, there are things engineers can do with carbon layup and taking advantage of its anisotropic characteristics to make frames that are not only stiffer but can potentially ride better than a titanium frame. That doesn't mean titanium is bad; every material has its pros and cons.

That said, the Thomson Masterpiece is probably one of the stiffest seatposts in the market. You might want to try a different seatpost on the Bingham and see how it feels. The alloy vs. carbon handlebar could also be contributing to the difference. Same for the wheels. Can you swap wheels between the two bikes and see if your assessment changes at all?

I should find a 27.2 to 25.4 shim and just move the seatpost and saddle from the Supersix to the Bingham.

I could swap wheels but I wouldn't have any brakes. Actually, one bike is QR and the other is thru-axle

Do you think the shallower rim flexes more? Spokes are the same count.

[fa63]

Duh on the wheels Haven't had enough coffee yet...

There is debate on whether there are meaningful differences in vertical compliance between properly built wheels... I typically find shallower rims to ride a little softer, but this hasn't always been the case. So who knows without actually testing them

Here is an excerpt from an article on Escape Collective by Rob English:

A wire-spoked wheel is a tension structure – an engineering marvel because of the load it can carry relative to its weight. The spokes must always remain under tension as they have little compressive strength. If a wheel was to absorb any impacts, that would mean the rim at the bottom moving towards the hub, so the tension on those lower spokes would reduce. This is only possible within a narrow band without inducing a fatigue load on those spokes that will lead to failure.

So typically, the wheel is considered a rigid structure within our system. If there is a claim that a wheel is offering vertical compliance, then I would suggest asking for deflection data to support this. Note that Zipp’s adoption of a single-wall, motorcross-style rim for mountain biking that allows “ankling” is a different type of compliance with the goal of allowing the tire to better track off-road terrain.

Originally Posted by NHAero

I should find a 27.2 to 25.4 shim and just move the seatpost and saddle from the Supersix to the Bingham.

I could swap wheels but I wouldn't have any brakes. Actually, one bike is QR and the other is thru-axle

Do you think the shallower rim flexes more? Spokes are the same count.

[NHAero]

Originally Posted by eddief

it's the handlebar bag.

Actually, the Supersix has been sporting the identical handlebar bag for the last few months...

[NHAero]

Originally Posted by fa63

Duh on the wheels Haven't had enough coffee yet...

There is debate on whether there are meaningful differences in vertical compliance between properly built wheels... I typically find shallower rims to ride a little softer, but this hasn't always been the case. So who knows without actually testing them

Here is an excerpt from an article on Escape Collective by Rob English:

A wire-spoked wheel is a tension structure – an engineering marvel because of the load it can carry relative to its weight. The spokes must always remain under tension as they have little compressive strength. If a wheel was to absorb any impacts, that would mean the rim at the bottom moving towards the hub, so the tension on those lower spokes would reduce. This is only possible within a narrow band without inducing a fatigue load on those spokes that will lead to failure.

So typically, the wheel is considered a rigid structure within our system. If there is a claim that a wheel is offering vertical compliance, then I would suggest asking for deflection data to support this. Note that Zipp’s adoption of a single-wall, motorcross-style rim for mountain biking that allows “ankling” is a different type of compliance with the goal of allowing the tire to better track off-road terrain.

I recall that article as well. It's great that EC has snagged Rob for the occasional article.

This could all be fabricated in my tiny mind. I'm not riding these bikes on broken pavement, so the inputs are small cracks rather than potholes. We're blessed with very good pavement, due to a well-drained base mostly. I do wonder about the difference in tires. The Agilest is 190g and the GP5000 is 225g. Same floor pump, same pressures.

[tellyho]

Originally Posted by Elefantino

I'm waiting for someone to ask how you can ride on 700x25s.

It's because NHAero is a small human. His 25s are your 32s.

[HenryA]

Carbon seatpost and handlebar is likely part of what you are feeling.

[vespasianus]

Originally Posted by thwart

Since you mention the rear end specifically, the Thomson straight post vs a smaller diameter carbon post is likely playing a role.

Disc forks are stiffer than a similar fork designed for rim brakes. And at least IME carbon h’bars feel just a little ‘smoother’ than a similar aluminum bar. And 35 mm deep rims usually ride stiffer than a 25 mm rim.

Nice bikes either way.

I would go with this. Thompson posts are notorious for being stiff. And carbon does a great job of reducing road buzz and harsh feel.

[NHAero]

Originally Posted by vespasianus

I would go with this. Thompson posts are notorious for being stiff. And carbon does a great job of reducing road buzz and harsh feel.

Just ordered a 27.2 to 25.4 shim, that will be a low cost experiment to put the Supersix set-up on the Bingham.

[Mark McM]

Originally Posted by fa63

Duh on the wheels Haven't had enough coffee yet...

There is debate on whether there are meaningful differences in vertical compliance between properly built wheels... I typically find shallower rims to ride a little softer, but this hasn't always been the case. So who knows without actually testing them

Here is an excerpt from an article on Escape Collective by Rob English:

A wire-spoked wheel is a tension structure – an engineering marvel because of the load it can carry relative to its weight. The spokes must always remain under tension as they have little compressive strength. If a wheel was to absorb any impacts, that would mean the rim at the bottom moving towards the hub, so the tension on those lower spokes would reduce. This is only possible within a narrow band without inducing a fatigue load on those spokes that will lead to failure.

So typically, the wheel is considered a rigid structure within our system. If there is a claim that a wheel is offering vertical compliance, then I would suggest asking for deflection data to support this. Note that Zipp’s adoption of a single-wall, motorcross-style rim for mountain biking that allows “ankling” is a different type of compliance with the goal of allowing the tire to better track off-road terrain.

I started riding when shallow section aluminum rims (with many spokes) were standard, and deep section "aero" wheels were only just becoming into common usage. These new deep section wheels had a reputation of being "harsh" riding, while shallow section wheels were considered "comfortable." I bought my first deep section wheels (34mm deep Campagnolo Scirrocos) in the mid '90s, and in my first ride with them the wheels gave me an impression of being smooth rolling. How could this be? Everyone told me that they should be "harsh" and buzzy, why did I find that they rode smoother than my shallow section wheels? While pondering this contradiction, I noticed something else - these wheels also rolled a bit quieter than my other wheels, possible because they had 20 bladed spokes instead of 32 - 36 round spokes, or maybe the cross section of the rim was less prone to resonant vibration. I think what likely happened is that my mind had made a sub-conscious connection between sound and ride smoothness/compliance, to give me the impression that quieter wheels must roll more smoothly.

Since then, I've never really been able to distinguish a difference in the vertical stiffness of wheels. I can tell the difference between tire widths/pressures, and between compliant tires (like lightweight TT tires) and uncompliant tires (like Conti Gatorskins), and I can often distinguish wheels that have too much lateral compliance. In quick steering motions and when out of the saddle rocking the bike I can tell the difference between heavy and light wheels. But I can't tell the difference in (vertical) ride compliance between wheels.