Vision Pocket Rocket bike test

Pocket Rocket

This is a modified version of a test of women's road bikes I wrote for Cycling Plus in August '99. All the bikes I tested (Cannondale R600 Compact Triple, Vision Pocket Rocket, Battaglin Bambino) were based on 650c (ISO 571mm) wheels. Since this was meant to be a test of bikes for women, and because not all the bikes fit me, I invited as many roadie women as I could find to ride the bikes and give me their opinions.

Introduction

The Vision Pocket Rocket frame is a new product by Steve Joughin (contact 01782 333736), aimed at children and small adults. The frame, including an aluminum fork, costs 295, and you can get it custom for an extra 50. This one is a custom version designed for 5'4" Clair, a fellow Cambridge resident. Clair says she spent a fair bit of time discussing what she wanted from the bike with Cycling Plus's Paul Vincent. She wanted to have a bike that would look cool and ride beautifully. She wanted a long aero carbon fiber seat post and aero carbon fiber forks for the looks, shock absorbing capability, and aerodynamics. In addition she wanted a short top tube so that she would have a shorter reach to the handlebars. Unfortunately most of this information got lost somewhere, and all that got transmitted to Steve Joughin were Clair's leg length and the desire for the long aero seat post.

When the bike came to me it was suitably kitted out with all the aero carbon fiber bits, including some very impressive Mavic Cosmic Carbone aero wheels. The stock aluminum fork was replaced by an aero carbon fiber one designed to work with a threadless headset. The steerer tube was left long, and a big spacer (38mm) was fitted. I presume this was to allow Clair to try it out before cutting the steerer tube down.

Feeling cranky. When I received the bike, it had 175mm triple cranks fitted to it. I expressed shock at this: why would such a tiny bike have such long cranks on it? Paul Vincent explained that Clair was using 172mm cranks on her mountain bike and seemed to get along with them, so he thought that the 175mm cranks would be all right on this. I complained that they were completely the wrong size, that 165mm cranks would be a more appropriate length. I also suggested that the triple chainset looked very out of place on this race-ready bike, and that a double would suit better. Paul relented on the crank length, but not on the number of chainrings: he said he wanted to see if a triple would work with such short chainstays. So they sent me a 165mm Ultegra triple. I swapped the cranks over, and appreciated greatly the self-extracting crank bolts on Ultegra chainsets.

Frame

Myra and Vision The frame looks stunning. The alignment is perfect. It has a sloping top tube, allowing a long seat pin to absorb road shock. The top and down tubes are a rounded off square profile, which I suspect is done for looks, as they offer no real advantages. There are no provisions for mudguards. The stops for the shifter cables are on the head tube, helping to protect the paint. However they are oddly positioned, with one pointing straight forward and one pointing 45 degrees up, and I found the adjusters hard to turn. There is only one water bottle braze-on. The frame and fork weigh the same as those on the Cannondale.

Clair had mixed feelings about this bike when she saw it. She'd been anticipating it for quite some time, and was very impressed with its appearance. The seat tube length was perfect for her when combined with the long carbon fiber seat pin, but the handlebars were too low and too far away. The effective top tube (the FL arrow in the geometry diagram) is 52cm long. This is 2cm longer than the top tube on the largest Cannondale Compact bike, and 1.5cm longer than the top tube on the largest Trek WSD bike. This is not good in a woman's bike: it stretches you out too much and puts too much weight on your hands. There is no reason for the top tube to be this long. With 165mm cranks there was ample toe clearance for all the riders (3cm for me).

Another problem is that the handlebars are too low. A longer head tube would help with this. The head tube is only long enough to allow the attachment of the top and down tubes. Many women's bikes have longer head tubes than strictly needed to allow the handlebars to be raised higher without using a very tall stem. Although the fork steerer was left long and a 38mm spacer inserted, the handlebars were still a fair distance below the saddle, putting even more weight on the hands.


Handling

I like a bike that goes where I want with little effort. I didn't feel immediately at home on this bike: I had to pay attention and focus on where I wanted the bike to go. I soon adjusted to it, but the need to adjust to it makes it a less enjoyable ride than the Cannondale or Trek for me.

Of course, not everyone likes the same thing, and some riders liked the quicker, less stable handling of the Vision. They felt that they would be happy riding the more frisky bikes in short road races or training rides, while they would prefer the Cannondale or Trek for longer rides, especially centuries.

Wheels

The Vision's wheels are real attention-getters. They are Mavic Cosmic Carbone, which consist of a narrow aluminum rim with a deep carbon section and 16 bladed spokes each. The result is a wheel with considerably less aerodynamic drag than the usual 28 or 32 spoke wheel. They are lighter than the wheels on the other test bikes but heavier than non-aero wheels like Mavic's (less expensive and less strong) Heliums. The wheels are great in a time trialer's bag of tricks but are not well suited to general purpose use, partly because of the replacement cost if they are damaged, but also because the large surface area of the rim makes the bike unstable in crosswinds.

The Mavic cartridge bearing hubs spin freely: they are the only wheels that pass the 'spoke wrench test'. This involves attaching a spoke wrench to a spoke and seeing if the wheel rotates so that the wrench goes to the bottom. The other wheels ignored the weight of the spoke wrench, while the Mavic spun slowly to put the spoke wrench at the bottom.

Equipment

Mirage front derailleur

The Vision is equipped with a Shimano Ultegra groupset, except for the Campag Mirage front derailleur. With the replacement 165mm Ultegra chainset the cranks were the right length, but the third small chainring clashes with the race-ready appearance of the other components. While the rear shifting worked fine, the front did not. Despite my best efforts I had the chain rubbing the front derailleur in the little chainring/big rear cog and big chainring/little rear cog combination. I suspect that the Mirage front derailleur is responsible. My final gripe was that the plastic bits on the front of the shifters rattle.

The long carbon fiber aero seatpost on the Vision was greatly appreciated by all who could ride it: they said it absorbed quite a bit of road shock. Unfortunately it is too short for me and too tall for the shorter riders.

The Vision has a threadless (Aheadset-style) headset. A large 38mm spacer was provided, but due to the long seat post the handlebars are still too low, even with a 90mm TTT Mutant stem installed upside down to provide some rise.

All the test riders found that the shifting and braking from the tops of the brake hoods was no problem with the Shimano shifters (nor with Campag either for that matter), but braking from the drops was difficult with both setups.

Comfort

Comfort is mainly determined by three things: the saddle, position on the bike, and how well the bike absorbs road shock.

I found I got along with the saddle, a Selle San Marco Rolls Due, but not everyone did.

Since the Vision is a racing bike with narrow high-pressure tires, you expect it to have a harsh ride in comparison to, say, a touring bike. Indeed it does, but the carbon fiber fork and long carbon fiber seatpost help to make the ride as smooth as possible given the constraints. Swapping the 20mm tires it came with for 23mm helps as well. Those who could use the carbon fiber seat pin liked it a great deal. I couldn't use it as it was too short. With a long MTB seatpost on the bike instead, the Vision and the Cannondale felt very similar.

In the Cycling Plus photos of the Vision it has a short stem with a fair bit of rise to it. Unfortunately when it came to me to test it had a stupidly long flat stem on it. It was completely unridable. I struggled to find a stem that would fit it. Eventually I found a 90cm TTT Mutant stem that, when installed upside down, helped make it ridable for short distances. The stem shown in the magazine would have been better yet, but it still wouldn't have been ideal. These measures were just attempts to redeem a fundamentally flawed frame design. At 52cm the top tube is simply too long for such a small bike, and the short head tube does not help bring the handlebars up.

You might think that with the handlebars so low it would be an ideal bike for a time trialer. I got in touch with a serious time trialer and asked her to check it out for me. After a ride around the block she didn't have any interest in it, as the handlebars were too low and too far away even for her. She liked the position on the Cannondale much better.

Summary

sketch of modified bike

This is a very well-made, smashing-looking bike that unfortunately doesn't fulfill its purpose. In order to allow the use of the long seat post, the seat tube had to be quite short. To raise the handlebars up further, the head tube would need to be lengthened and the top tube would have to slope radically. In addition to bringing the handlebars higher, the longer head tube would also bring them closer, since the seat angle is steeper than the head tube angle. The drawing to the left shows what lengthening the head tube would look like. The dotted line is the current top tube, and the solid line above it would be the new position of the top tube. In addition the effective top tube could be further shortened by moving the head tube closer to the seat tube (to reduce the gap between toe and wheel to 1cm instead of 3cm). This would result in a far more comfy bike, one that most of the testers would probably like.

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