Monday, August 27, 2012

A Discussion on Suspension: Gravel Bikes

Hey there! Hope you all had a great weekend. Today I'm kicking off a two part series on suspension. Today's discussion will focus on suspension for the gravel road rider.

Suspension can be derived in two different ways for anyone on a bicycle. First is pneumatic- suspension from the tires. The other way is to use a mechanical means to absorb vibrations, either passively, by way of frame flex or component flex, or by an active, purposeful means involving some form of moving parts.

Either way, absorbing vibrations is the order of the day. Vibrations are important to consider, because if the energy causing the rider to feel vibrations is not absorbed by the tires, frame, or a passive/active mechanical means, then the rider has to absorb those vibrations which eventually can cause fatigue, numbness, and other issues.

It's not just about width, it's about volume.
Without getting overly technical here, I want to explore why a rider on gravel roads would want to consider suspension. Obviously- everybody is going to run tires, so let's start there.

Tires are essentially air springs. Whether you choose tubed, tubeless, or tubulars, your tires are springs that can be adjusted. Furthermore, the tire casing, tube, (if any), and tread pattern also affect the way the "spring" will work.

Springs can be stiff, soft, linear, or they can "ramp up" in spring rate quickly due to volume available and/or tire pressures used. You as a rider can greatly affect the ride quality of your bicycle in a number of ways by your tire choices and tire pressures that you choose.  Go to a higher pressure and you get a stiffer spring rate. Use a lower volume/narrower tire and you may also have to move pressures higher and the volume of that tire will affect the ramping up of the spring rate as well.

Typically, you would not want to run maximum pressures as rated on a tire on rough roads because this affects how your tires can absorb vibrations. Higher pressures in tires make vibrations that the tire could normally absorb go past the tires and into the frame/rider.Likewise, the narrower/lower volume your tires are also affects the way you can adjust your spring rate, (ie; tire pressure), and this may affect your ride quality. Finally, things like frame clearances, terrain demands, rider weight, tire construction, and more will start to narrow down choices.

If you don't remember anything else though, remember this- a tire with a reasonable amount of air, but still at a point where it can conform to road irregularities, will be faster and provide more rider comfort and control than a tire at maximum, or close to that, pressures. (I would only add that a higher volume tire provides the rider with a wider range of adjustability in this respect.) A tire at higher pressures has to bounce up and over trail/road irregularities instead of conforming to, and rolling over them. Those little bounces have to be absorbed, and don't forget- overcome by- the rider. Yes, higher pressures result in more rolling resistance on rough roads.

The smoothest line is less fatiguing
 Obviously, tires should be a component of your ride that you pay close attention to. Especially on the longer events. They are your first, (and in most cases- only), line of defense against vibrations that can steal away your energy, cause you to be slower, and possibly cause longer lasting side effects like numbness or other physical maladies. Not only that, but a wider, more voluminous tire can also ward off pinch flats that would otherwise cause a skinnier tire to flat. Spend less time fixing flats, or use a tire that is lighter, but may flat more often. Oh the decisions!

Mechanical Suspension: Oddly enough, mountain bikers would never think twice about accepting the benefits of suspension, yet gravel/back road/rough road riders almost never consider such things. Too heavy? Too complex? Not worth the trouble? At one time, the answer to these questions was no. The proving ground was the cobbles of Europe, specifically the course of Paris-Roubaix.

Early 90's road suspension bike
Many folks may remember Rock Shox foray into the realm of road bike suspension. The overgrown Mag 21 specimen was called the "Ruby", and was actually used to win Paris-Roubaix. Many say Greg LeMond was at the fore front of the use of a suspended road bike for these cobbled races.

Probably the most outlandish example of suspended road bike design has to be the Bianchi piloted by Johan Museeuw at Paris-Roubaix, which you can read all about here. Said to have cost $20,000.00 to produce, the bike did not reach the final desired result when a flat tire ended Museeuw's chances near the end of the course.

So much for road bike full suspension, right? Well, the idea has not gone away entirely. Just take a look at Trek's Domane bike which has already won events like Strade Bianchi, a stage in this year's Tour de France, and most recently won at Gravel Worlds in Lincoln, Nebraska. The Domane takes a subtler approach than the overtly suspended bikes from the early to mid-90's, and hides the suspended component for the most part at the junction of the seat tube and top tube. (Which are in fact, decoupled) The fork is made to flex more, and in so doing this, Trek has retained a traditional look to the road bike, at a fantastic light weight, without resorting to an offensive assault on the eyes and sensitivities to bicycle overall weight.

Is there a place for such a beast on the dusty gravel roads? Is it even necessary to go that far with suspension, or are voluminous tires enough? It'll be interesting to see if folks can even envision needing such a device, much less having the option.

Okay, tomorrow I will explore the opposite end of the spectrum regarding suspension with fat bikes.

8 comments:

Ari said...

I think tires make the biggest difference. I think most gravel riders don't want a mechanical suspension because of weight and fear of it getting trashed in wet gravel. I agree that bikes should have the clearance for bigger tires. The classic 700x35c just does not cut it any more.
Ari

Jon said...

I don't use a suspension fork on my mountain bike, any more, and I haven't really missed it. The 29" wheels roll over stuff pretty well, and I have lost my love for the weight and cost of the add-on suspension.

I am looking forward to reading your thoughts on suspension for fat bikes. I rode my Mukluk to work, coincidentally, and i was pondering that very issue as I ran through a pothole which would have been pretty jarring on my normal commuter (with 26x1.35" tires.

"Who would ever need suspension on one of these?" I thought to myself, as I rolled over the hole in the pavement with a barely noticeable thump-thump of the big tires. Even at 22 psi, the tires take up al ot of shock. (I have ridden this bike off-road in Fruita, a bit, and I feel the same way about rocky, technical trail riding, btw.)

Looing forward to your take on that...

rideonpurpose said...

It's all about the tires...

But I've got a very different opinion of what that means. To me the fastest answer is 32c tubulars at pressures in the 30s. There is no doubt in my mind that they roll faster than anything wider.

I did ride a ton of gravel a few weeks back on my Cannondale Flash with a lefty. I was pretty happy with the performance but it would be ridiculous in a race situation.

I know people will dismiss me as being too "racy" when it comes to this topic etc., but in the end it's always easier to get done sooner and what works is what works. There is no most comfortable fastest bike, but it is plenty possible to choose a bike that lets you be 2% more comfortable and slows you down enough that you end up hurting far worse.

Guitar Ted said...

@Jon: There will always be rigid mtb riders, and I was expecting to hear from one. The thing is, faster, more comfortable riders are going to use suspension when racing off road. Your wheels off the ground, (even for those micro-seconds that can not be necessarily felt from the cockpit of a bicycle), are not helping you go faster, further, with more comfort and control. You may choose to ride otherwise, which is your prerogative, but the fact is that suspension is a benefit almost all the time.

Guitar Ted said...

@rideonpurpose: Glad you like tubulars and think they will work best for you. I can say, from experience and observation, that you are definitely a minority.

I can not imagine carrying an extra tubular for events like DK 200, Trans Iowa, or even Almanzo 100. The time it would take to swap out a tubular, and the expenses incurred in running them make this a niche of a niche when it comes to gravel road riding, especially in self supported races, which the majority are. (For now)

As for "getting it done sooner", I have heard that line plenty over the 8 years I've run Trans Iowa and been around gravel racing. It works for the hundies and lesser distances, but it isn't always the best option for everyone in every event. Racers looking to win are no exception.

Using your logic- "It is always possible to choose a bike that is 2% faster and ends up slowing you down and hurting you worse after the event is over." I've seen it work both ways.

I think you are extrapolating my point out to absurdity. Of course, there is a balance that must be ascertained by each rider, but my point is many choose what they perceive as "speed" over what actually is faster, and that is something to consider thoughtfully.

Ari said...

Maybe to make a frame wider we have to get away from the archaic bottom brackets of 68 and 73mm. This perhaps would allow wider frames. I think the Surly Crampus is going that route being just between a 29er and a fattie.
Just thinking,
ari

Guitar Ted said...

@Ari: Yes- but a lot of folks would cry foul about a wider "Q" factor. Hard to change some of those old standards due to perceptions and beliefs.

MG said...

As one who needs every advantage due to 20 screws in my forearm, I often ride the line on low pressure, which is why I always run tubeless, both gravel and mountain.

Jay's ride on the Domane at Gravel Worlds was an impressive feat, but it was about more than the bike. He was a machine that day and the bike complimented his strength. He couldn't have done that on any road bike... It was rough.

Even in the Midwest, I choose to race my 4" travel 29"er more often than not because it's my fastest bike that beats me up the least, and I crash it the least too. I win the most on it. Stats don't lie...

People can ride whatever they want... Whatever makes them feel good.