Planet X Stealth Pro Carbon - BikeRadar

Whether you're on a budget or want to spend a little more, Planet X offers a variety of builds for its popular Stealth Pro Carbon time trial frame. Here Jeff Jones takes an upper end 'pimp build' through its paces.

The Planet X Stealth Pro Carbon is fast, which is exactly what you want in a time trial machine. It also handles well and is relatively cheap, with prices starting from £999. And while it could be tweaked for better aerodynamics, it's a bike that will suit the needs of even the best testers, including a certain Tour de France podium finisher.

Frame

The Stealth Pro Carbon is Planet X's only time trial frame, although its design has been used by several other manufacturers for their machines. The front end features a slightly elongated headtube to assist in aerodynamics.

Image:

The downtube is not a pure aerofoil shape, it's more rounded-triangular, but its horizontal cross section does come close to a proper aerofoil. The top tube is rounded-triangular, but not overly thick. There's no point moving more air out of the way than you have to. The seat tube is moulded to fit around the rear wheel and the seat stays have small fins, both aids to reduce drag on the rear wheel. The straight forks taper towards the skewer and have narrow leading edges.

Although it would be nice to see internal cable routing, on the whole this is a fast frame. It will be interesting to see how it evolves over the next few years.

The bonus is that it's also affordable, with Planet X selling complete bikes (they don't sell the frames separately) for as little as £999. The 'pimped' version that we tested - weighing 8.2kg and specced with Ultegra, Planet X Carbon 50/101 wheels and an Ergomo power meter - sells for £2499.

The frame comes in four sizes, ranging from 48cm (S) to 57cm (XL) seat tube lengths. We tested the 54cm L model, which features a 55cm top tube and weighs 1.3kg. On all models, the seat angle is 76 degrees and the head angle 72.5 degrees. This helps you get a forward position without making the handling too twitchy. It comes in four colours: glossy black, white, blue and pink. I have also seen a rare bright red one.

The frame was used by 2007 Tour de France runner up Cadel Evans: a glance at any of the photos from the time trial stages will show that, and it's also stated on Planet X's website. If it's good enough for someone as particular about their equipment as Cadel, it should do for mere mortals like us.

Ride

Where time trial bikes excel is going fast in straight lines, as this is where you will benefit most from improved aerodynamics. The Stealth Pro Carbon is no exception. When analysing my time splits between two 'in line' points in a time trial, I was amazed at how fast I was travelling. It was a good 3-4km/h quicker than I could do on a normal road bike, a real testament to the Stealth Pro Carbon's speed. In the four races that I did on it, this translated to four top five placings, including a close second in the journalists' world championships.

With such a forward position and steep seat angle compared to a normal road bike, I was worried about how this bike would handle. But it didn't take long before I realised that these fears were unfounded. It's different, yes, but it doesn't feel nervous at all. The relatively relaxed head angle of 72.5 degrees - common in time trial frames - plays an important role in keeping the steering stable. This is obviously critical when you're riding on a technical course, as you need the maximum confidence to take the bends at speed. Laying the bike over on a tight corner won't feel right, but as you're not going to be racing criteriums on one of these, it's not a big issue.

Climbing was also better than I expected. I found I could comfortably stay in the aero position without losing power on gradients up to about 3%. This position was also OK for steeper hills, providing they were short. On longer, steeper climbs, it was necessary to ride on the bull horns, but this was no worse than riding on the hoods on a normal road bike. So much so that I intend to ride the Stealth Pro Carbon in the British national hill climb championships at the end of October. The course goes up the not particularly steep Cheddar Gorge, and I believe it will be advantageous to use the aero position for at least half of it.

Overall, I really enjoyed riding this bike, and had no qualms about taking it out for long rides. It's comfortable and fast - what more could you ask?

Equipment

Our machine came specced with Shimano Ultegra, with a few upgrades. The cranks were the Stronglight Pulsion CT², one of the lightest cranksets on the market. The hollow carbon crankarms and aluminium 53/39 tooth chainrings don't add up to very much weight: Stronglight claims 430g for their 172.5mm crankset.

Image:

The bike came with an Ergomo Pro power measuring device. German-made, the Ergomo measures power through the torque on the bottom bracket. It's a finicky piece of kit that, like all power meters, has to be adjusted before each ride. This only takes five minutes or so, and the rewards in terms of feedback are great. Combined with the CyclingPeaks Ergoracer software, you can analyse your training and racing to the tiniest degree. Power meters are still relatively expensive (the Ergomo Pro retails for around £900) but they are the one of the best training aids available.

The rest of the equipment is Planet X brand, save for the brake levers which are carbon Tektro RX 5.0. The Stealth Pro seatpost continues the aero carbon theme and is topped by a very comfy PX saddle. The stem (aluminium) and bars (carbon) complete the package, with the extensions available either as straight or angled versions. The extensions do have to be cut to measure, but Planet X will do this if you go to get fitted.

Wheels

Planet X offers a range of wheels with their bikes depending on your budget. Ours came with Planet X's own Pro Carbon 50 (front, 16 spoke)/Pro Carbon 101 (rear, 24 spoke, two cross). Each wheel is finished with a shiny marbled surface, going nicely with the frame. They're handbuilt using Sapim CX Ray spokes, American Classic hubs and deep dish tubular carbon rims: 50mm for the front, 101mm for the rear. The front weighs 640g and the rear 945g - not a super light combination, but one that's certainly aerodynamic and affordable. This pair would cost in the region of £500. Planet X also makes the Pro Carbon 82 which features an 82mm carbon rim, a full disk wheel, and offers Xentis four spoke and standard spoked Reynolds Alta Comp wheels as part of its bike builds.

The Pro 50 front handles like most deep dished front wheels (including Lightweights) that I've ridden. In a crosswind, it requires a bit more effort than a normal spoked wheel to keep straight, but nothing that you won't get used to after a few rides. The only wheels I've come across that are immune to this effect are Zipps, with their flared aerofoil rims and golfball-like dimples.

The Pro carbon 101 rear is absolutely fine in a crosswind, because you've got most of your weight over the back wheel. It's almost-but-not-quite a disk, so it's great for hillier, technical courses where lighter weight and better handling come into play. But if money is no object, a disk is still going to be your best option.

Both wheels were fitted with Continental Competition 22 tubulars. These are tried and trusted by the pros. They give a great ride and have a good deal of puncture resistance, but don't cost the earth.

Summary

Planet X's Stealth Pro Carbon is an excellent choice of machine if you're after a medium-budget time trial bike. With so many speccing options available, you should be able to find one that works for you, bearing in mind that it can always be upgraded. But the heart of the bike is the frame, which is not too heavy, handles well and is aero enough to satisfy a podium finisher in the Tour de France. It's an amazingly good performer for the price, and right up there with the very best time trial machines.

Manufacturers description

For 2007 we've completely re-vamped our range of Stealth Pro Carbon build specs to offer the highest performance tri bikes at incredible prices. All bike builds also now available with optional ergomo power meter upgrades!

User Reviews

There are 9 reviews on this post

Submit Your Review: