In The Press


This one-time "chromo only" builder takes a stab at aluminum and comes up with a definite winner!

Taken from January 1993 issue of Mountain Biking Magazine, pages 59-62.

The bike is named after the trail, but the trail is named after the ride. Ergo, the bike is named after the ride. Yeah, right!

In the Santa Clarita Valley, just north of Los Angeles, is the famed Six Flags Magic Mountain amusement park. Forget the "kiddee" and "sing-song" rides, Magic Mountain is for thrill seekers. Just look at some of the names of their rides: Colossus, Drop Out, Tidal Wave, Psyclone, Free Fall, and Ninja.

About two years ago, they unveiled an outrageous roller coaster. Named "Viper" it begins with a 14-story climb, followed by high-G turns, loops, and barrel rolls. Not only that, it's built with just a few skinny supports, allowing the tracks to sway under the forces of the ride. One of our editors got to ride it the week it opened. His quote, "Hands down, the best ride I've ever been on."

A mere five miles from Magic Mountain is a lonely firebreak; the semblance of trail that drops off sharply from the highest mountain in the area, and works steeply down to the valley floor via steep dusty switchback after steep dusty switchback. Its name, appropriately enough, is "Viper".

The Curtlo shop, coincidentally, sits at the Santa Clarita Valley floor just a stone's throw from the bottom of Viper (the trail), and only a few miles from Magic Mountain. So when Doug Curtiss (the maker of Curtlo custom mountain and road bikes), teamed up with Mike Troy and John Buell to work on a new aluminum design, "Viper" was the most natural name for the bike.

Same Name, New Stuff

Troy, Curtiss, and Buell adopted the name of "T.C.B. Design Werx", and went to work with Easton aluminum. Now if it seems that you've been reading a lot about Easton and how they've been working with a lot of people lately, you're right. Easton is both picky about who they work with, and anxious to open up new liaisons with bike builders. This is all thanks to their Varilite ProGram tubing, which uses "taperwall" technology for strengthening and lightening 7000 series aluminum.

The Viper was more than just a bike made from an Easton tube kit. It would involve re-thinking all the tubing specs, but then that's something that Easton is pretty good at, since they've created an entire bicycle tubing design team to work with bicycle designers.

Our biggest complaint of this test can be aired right now. It's not with the bike, it's with the tubing. Easton's aluminum, ProGram taperwall tubing, has impressed us more in the recent months than any other aluminum tubing. It's light, it's strong, and it's some of the best aluminum we've ever ridden on. The only problem is, ProGram has become sort of a generic name for the taper technology tubing, but nearly every company using it has designed dramatically different specs for it. That means that even though the same sticker is displayed on an Alpinestars, Wheeler, Yeti, Curtlo, and a host of others, they're probably all very different from each other. It seems pretty evident that some new name or sticker system is necessary to convey the notion that not all of these tubesets are the same.


This was never as evident as with our testing of the Curtlo. We tried the Alpinestars a while ago, the first bike we tested with ProGram tubing. We like it. Then the Wheeler came along with ProGram, and we liked that, too. Then came the Yeti A.R.C., a most impressive improvement over their previous bikes. And finally comes the Curtlo, by most of our riders' accounts the best Easton ProGram bike we've tested. All ProGram tubing, but definitely not all the same ride.

Frame Facts

The Viper is a Curtlo bike, but uses several things that haven't shown up on other ProGram bikes. A number of these are from the T.C.B. Design Werx (hence the T.C.B. designation on the chainstays). So in effect, it's a T.C.B. Designed Curtlo bike. The bike will be sold, for the most part, as a frame, so let's spend most of our time there, shall we?

First off, the frame is made entirely out of Easton 7005 series ProGram aluminum. Some bikes bearing the sticker use ProGram in the main frame, but not in the stays The Viper is 100 percent ProGram.

Next, you'll notice the main triangle uses big diameter tubes, similar to the Yeti A.R.C. While the outside specs are similar, inside they're different. The down tube is a big 1-3/4-inch diameter tube, and the top tube is 1-1/2-inch. They're slightly thicker in wall thickness than the A.R.C., which Curtlo believes will increase stiffness and durability, plus it's less susceptible to dents than the thinner walled tubing.

What was really trick was the ovalizing at the bottom bracket of both the down and seat tubes. This technique, a la Ritchey, is new to aluminum bikes, at least as far as we know. It increases the surface area for welding, plus helps to reduce bottom bracket flex. Not only that, it's quite distinctive and looks cool.

Back in the rear, you've got stays which have a lot more going than they appear to. The nice, double bend chainstays are free of crimps, something chromoly users take for granted. Now this design comes to aluminum via the T.C.B. "Chicane Stays." They're also quite trim at just 16.75 inches. The seatstays were thinned out a bit from the earlier prototypes of the bike. In working with Easton, they determined that since the seatstays bear little stress, thinner walls would be advantageous. It wouldn't hurt durability, it would lighten the bike, and it would improve shock absorption.

Now brake flex might be an issue, or so you think? Curtlo welds a beefy brace across both the chainstays and seatstays. The seatstays also receive the signature Curtlo single-arm brake stop. All said and done, unwanted flex is nowhere to be found, and braking performance is not only good, it's very good.

Numbers? The Viper gets a 71-degree head angle and a 73-degree seat angle. The top tube on our "medium" size bike was 22.5-inch (23-inch effective horizontally), and the wheelbase as a tight 41.25-inch. (For the record, the Viper comes in "small", "medium," and "large" sizes).

Easy Ridin' Hard

The Viper was available as a frame (for about $1500), or as a frameset (with a Manitou 2 fork, Aheadset headset, and stem for about $1950). Parts packages are also available, but the Viper is not currently available as a complete bike. For the sake of the test Curtlo and the T.C.B. boys equipped our bike with an XTR drivetrain using Grafton cranks, Specialized bar ends, SPD pedals, Mavic rims, Fast Feathers seatpost, Avocet saddle, and a Hyperlite handlebar.

We took the bike out for its first ride and were immediately impressed with its light weight. Frame weight is just three lbs., and our complete (fully dressed) bike weighed just 25 lbs.

As is the case with lightweight bikes, lateral movements were very quick, and overall responsiveness of the bike has to be rated as "excellent".

Climbing was very good, both seated and standing. Neither one seemed to be better than the other, but rather they both were equally impressive. This, in our opinion, is one of the signs of a well-balanced bike. the tight chainstays helped out in the climbing department, as did the ovalized tubing in the main frame, eliminating power-robbing flex at the crank.

The Viper got a lot of help on the downhills from the Manitou 2 fork, a fork that some of our riders are really taking a liking to. What seemed to work so well for us was that the beefed-up front triangle made for a very responsive, quick steering, and quick handling bike, though not one that pounds your fillings out. The rear end, on the other hand, was much looser. It moved around somewhat behind you, and a quick blip of the rear brake and you could square off just about any corner. The rear end's best asset, though, has to be its shock absorbent qualities. For a rigid bike, the rear end felt pretty darn compliant.

A lot of shock absorbent bikes seem to suffer in flat hammering and fast single tracking. One test rider found the Curtlo to be much quicker than he expected on single tracks, almost to the point of being squirrelly. One of our Expert class test riders thought it spot-on for single tracking, not being "too whippy" as he expected based on its very good downhilling.

Rider positioning is definitely aggressive, with a full 23 inches of top tube to work with. The sating and performance of this bike shout out "RACING" all the way, but it's not a bad all-around bike at all. In fact, that was our biggest surprise. Most really fast race bikes aren't good for "just ridin' along," but the Curtlo made the cross-over very nicely.

Down 'N Dirty

The worst part of the Curtlo Viper is the price. At $1500 for the frame, there are a lot of riders who would love this bike but who just can't afford that kind of money. That's too bad, because the Viper, if it holds up in the long haul, could be the bike to answer a lot of rider's dreams.

Of all the recent aluminum bikes we've tested, it's by far the closest to what we like. It seems to posses the strength and stiffness we like in tough chromoly bikes, and matched the weight of the lightest chromolys. It also offered much of the same shock absorbing qualities of titanium, but without the "over flex" found in some T-metal bikes.

Aluminum looks to be a big contender at the high end this coming year. Easton's ProGram tubing and some high-end builders are pushing pretty hard with it. We must point out that aluminum hasn't had the best track record throughout it's past, either for handling or for durability. Based on six months of testing ProGram bikes, we'd say that aluminum's rep might be about to change. Check back with us in another six months and we'll let you know. Until then, let's go ride the Viper; bike, trail, or roller coaster, we like them all!