Tuesday, July 10, 2007

Experience > Lab

I post somewhat frequently on a couple cycling forums. Typically I avoid the "he said she said" threads where a new response pops up every 4 seconds. On the other hand, if I have something I think might be of interest to say, I'll say it.

A while ago I posted something on Spinergy Rev-X wheels. You probably know of them - the 4 pair carbon spoke aero wheel.

I pointed out that the X-Beams, little H shaped plastic pieces which stick into the V of the spokes (making it into an A), help increase stiffness.

Someone promptly posted that this is not true according to Damon Rinard's site. I was thinking of posting but then decided that would create a "he said she said" thing. So I refrained.

I had dismissed the counter-claim because I felt the X-Beams helps increase Rev-X wheel stiffness. I've ridden the wheels a lot - from the first generation on - and even took part in a user feedback program. I even had some experience with the wheels in a semi-controlled environment. I was raced the same bike with the same tires on same course and did the same sprint for many weeks in March and April. Although week to week smaller variables changed (wind, temperature, etc), I noticed a radical change in the firmness of the bike's handling when I put the X-Beams on my wheels, especially the front wheel. It made the bike easier to track using my aggressive side-to-side sprint, the rim didn't hit the brakes, and the bike seemed stiffer laterally.

However, I didn't quantify this in an objective manner. I simply jotted down in my training diary that the X-Beams helped stiffen up the wheel.

So who's right? Is Damon (whose work I respect - and in fact I still use his spoke length calculator) correct and I'm smoking crack? Or did Damon miss something?

I have two illustrations of why either question might be answered a resounding "Yes".

Spinergy, with their Rev-X wheels, sponsored a lot of pros back in the day, but one stood out above the rest - Mario "The Lion King" Cipollini. His astounding take of Tour stage wins (along with his PR antics) meant front page pictures for the fledgling wheel company.

Naturally the King required wheels which complemented his megawatt sprint. Likewise, an outfit like Spinergy was able to accommodate him by building custom wheels.

Virtually his only complaint was that the wheels weren't stiff enough. So Spinergy, looking to please their star racer, promptly sent out some X-Braces with instructions on how to install them.

Word filtered back from the Boot country. "Better. Want stiffer."

Spinergy decided to go a bit deeper. They built some wheels with double the carbon in the spokes (eventually they'd sell this version as Super Stiffs) and air shipped the wheels to the Lion King.

The wheels came back.


The Spinergy engineering crew was at wits end. There really wasn't anything else they could do to make the wheels stiffer without compromising some other aspect of the wheel - production, aerodynamics, etc.

In a fit of desperate genius, they painted the wheels red, put "LION KING" on the side of the rims (four times on each side), and sent the wheels back.

The response from Italy?

"E fantastico!"

Or something like that. I don't know what Cipollini actually said (I don't even speak Italian) but he was happy. He put the wheels on his Cannondale. And went out and won a stack of Tour stages.

So that last "modification" didn't make a stitch of engineering difference. The red paint wasn't made with carbon paste or anything, they didn't change any material thing in the wheel, but the rider's feedback indicated that the wheels were better.

That's the story that would show that a laboratory can illustrate when perceived differences are in fact illusion.

But let me expand a bit.

That same company had a ferociously dedicated engineer who tested and analyzed things to extremes. He eventually left the company and now analyzes products on his own, helps run wind tunnel tests for certain really big teams, and the whole time insists on complete anonymity - no pictures, his name is not to be mentioned, etc etc. To respect that I'm not naming him or his last name or anything.

Such is his dedication to the whole sport of cycling that he stood on some very cold pavement, only his bike and backpack for company, for something like five hours and helped marshal a race in a little town called Bethel, CT. This after riding a couple hours up to the course - and looking forward to an equal ride back.

Then he hopped on his bike, raced the Pro/1/2/3's, and proceeded to tear the legs off everyone out there.

He is the reason why I use Ritchey WCS (and regular) aluminum stems - in the course of testing he found a lot of weak stems but discovered the Ritcheys were particularly well made.

Does your stem ever slip? Has it cracked? My Ritcheys have not. 'Nuff said.

He found that certain rim characteristics had less to do with aerodynamics than, say, the seam between the tire and the rim. (Incidentally T-Mobile seems to agree as they put some stuff there between the tires and rims on their TT bikes.) That the way they shaped the trailing edge of the aero rim made a huge difference. He found that perception (of things like wheel bearing friction) could not be duplicated in a controlled environment - but they still got "faster" bearings (lacking dust seals) because that's what the shops craved. Inside though Spinergy knew that the bearings weren't any faster - it was the red paint and decals all over again.

This engineer's engineer tested and signed off on the X-Beams and the double layer of carbon on the spokes. And not for marketing purposes - he's one that would not have compromised his integrity for marketing purposes. So I feel like I have some technical backing in my very amateur "Hey X-Beams make Rev-Xs stiffer" statement.

I have a car which I enjoy driving a lot - apparently it's the first production car that came with suspension braces front and rear. Basically the manufacturer uses a big piece of metal to bridge the gap between the left and right wheels. Normally cars are made which resemble a big U if you looked at them from behind - the passengers, drivetrain, and luggage sit in the U, the wheels, sheetmetal, etc., side on the outside of the U.

The problem is a U wants to get squished until the tops touch. I'd type the letter but I can't find anything resembling a squished U so you'll have to imagine it. Riding in a convertible is usually illustrative of this idea - the lack of a roof makes the car more flexible. If you put a cross piece on the U (and made it into, say, an O) it would be a much stronger, err, letter. Or if you put a hard roof on a convertible, the chassis stiffens up.

Likewise, when you put a brace on which link the left and right wheel of a car, it stiffens up the car's chassis. This makes it easier to engineer the suspension geometry, shock and spring rates, and makes the car more predictable to drive when going over uneven pavement.

Of course at some point someone had to ask on a forum, "Does the brace really make a difference?" After all, it might be all marketing hype.

No one really came back with a solid answer until someone wrote about their experience when installing something in the engine compartment. They had to unbolt the brace to install it. When they finished up, they forgot to tighten the brace bolts on one side.

If the brace didn't do anything, nothing would have happened.

But when they went out driving, every time they went around a hard turn, the front end of the car clunked. It was the brace (with its loose bolts) hitting the mounting studs.

This indicated that the frame was flexing enough to move the bar around. And if the brace was tightened, well, either the brace flexed, the frame flexed less, or (what's probably the case) some combination of the two.

Regardless, there was some empirical proof that the brace actually contributes to making the car stiffer.

Back to the X-Beams.

They stick in place. There's double stick tape, you clean the inside of the carbon spoke, and you stick it on.

Sometimes it got dirty or unsticky or some rubbing alcohol was still left on the inside of the spoke. The result - the X-Beam got unstuck.

And when it did you'd get this awful racket whenever you sprinted or rocked the bike aggressively from side to side. It sounded like someone jammed a screwdriver into your front wheel.

It was simply the X-Beam, stuck on one side, trying to stick to the other side. And not succeeding.

The racket clearly indicated that the spokes were moving more than they were before (or that the X-Beams really stretch a lot when properly installed). Therefore the X-Beams must be doing something.

A second bit of evidence - if you put the X-Beam in crooked, it would bend quite severely. It's apparent that the X-Beam is holding a lot of force in its thin crossmember.

I'd also notice the rim would rub the brakes without the X-Beams. The rim was so stiff that the whole rim would tilt around the hub (instead of simply flexing the lower part of the rim). And this is where the lab test comes into play. Damon's test was based on the rim flexing down away from the hub. He didn't measure if the rim rose on the other side. And that's what causes the perception that the wheel is flexy. If you rub your brakes on every downstroke you're not going to be really happy whether your a Cat 3 or the Lion King. X-Beams don't necessarily help the rim flex less between the hub and the ground. But the rim stays better centered between the the brake pads above the rim.

Therefore X-Beams make a difference.

And that's that.

Well until a better Rev-X expert says something...


Ray said...

They work. I know that when i was running the wheels my cyclocomputer would drop out at times during a sprint or standing on a hill. With the x-eams the problem went away...

GOB said...

I worked at Spinergy. Cross beams work. I weighed 160 pounds at the time, and they still stiffened up the wheels significantly.

Spinergy in the early days was an amazingly frustrating blend of venture capitalist backing and engineering alchemy/genius. Some of the stuff the engineers did was voodoo. Some of it was bullshit. Much of it was brilliant, but hard to reproduce in a production, for-profit setting.

The sales team were salesmen. Bike wheels, used cars, whatever, they would sell it. A large amount of horseshit flowed from the office of the over-paid and over-qualified sales-VP.

Spinergy had a lot of defective wheels, and the warranty service wasn't the best. "Revenue" wheels would be shipped before warranty wheels qute often, a practice I found quite shady on a product that was averaging 10-15% defective every month.

Changes and updates to the wheels and hubs often were shipped to customers before the sales team even were aware that the changes and updates had been made.

As frustrating a job as it was, I still enjoyed it quite a lot.

andrew said...

you should really post this info to seperate 'bike-tech-knowledge' sites. as modern cycling equipment has an abundance of reviews/opinions/diy/know-how, quirky turn-of-the-decade equipment such as the REV-X could really use the internet to share ideas/repairs and validate the self-destructive nature of these wheels.

it would also be put to good use in hopes that these wheels could live a new life with DIY on refreshed bearings installs, replacement shafts etc.

I consider these wheels the DELOREANs of the aero cycling wheel industry..

I am just saying this because these wheels are making quite a resurgance with the fixed-gear crowed pushing them up to $260 for just a front clincher on ebay.

I spent all of last week trying to source one in toronto, and i scored one in pristine condition, complete with epoxied x-beams installed.

fruit-of-my-labour can be seen here::

so much for the double-sided-tape.

cheers, would love to read more on these wheels.. im surprised popular-science never covered anything.

Aki said...

Thanks for the comments... To think I gave away a front Rev-X just before we moved, to someone I don't even know. Aye caramba. Nice looking bike btw.

andrew said...

funny thing, i was on bikeforums and read a posting with some very interesting info on spinergy hubs, what to look for in late model rev-x's etc by carpe diem? Found out it was you that posted!

I read some conflicting info that "late" model rev-x's had exposed bearings on the outer sides of the wheel, however you mentioned to look for 3-section aluminum hubs - these aluminum hubs versions have flush bearings.

let me know, this info is really great.

and to know you complimented my bike! wow! its only my first build! and everything except the bars + stem came from craigslist!

andrew said...

btw, like this on ebay currently:

My front hub looks exactly like this:

A friend of mine is looking for a suitable front wheel, is a hub such as this what he should be looking for?

however, these such wheel has some significant brake wear along where the carbon meets the rim..

Aki said...

That hub is the 4th gen, so it's good.

But that "rim wear" is actually from a maladjusted brake hitting the structural carbon. That's not a good thing.

trueno92 said...

hi Akira,

I just wanted to let you know that with the power of web.archive.org I have managed to pull many of Spinergy.com's old webpages referencing anything to the rev-x wheels. I know this is like beating a dead horse, but I'd like your feedback regarding the rev-x at speeds over 25mph. That and also your thoughts regarding their move to "outboard bearings" having the bearings positioned on the outer faces of the spokes, and not mounted in the hubs...



from reading/researching, I had found that this outboard bearing was introduced for 1997.. did this continue until the product was discontinued? I thought I had seen some post 1999 wheels with hub mounted bearings...?

Thanks again for your feedback, I will have the rev-x knowledge base up soon, and hopefully it will dispell some of the myth re these wheels.

also, blog has been updated!