Planet X carbon frames

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Planet X carbon frames

Post by Lapin » 24 Jan 2017 08:30

Hey all,

I've decided to have some fun and put together a hill climb bike this year rather than adapting my usual ride. I have a few options kicking around for some second-hand Alu frames but seeing as weight reduction and stiffness is the most fun part to play with I've been looking at carbon.

Planet X currently are flogging their 'Pro Carbon' for 300-350, the RT-57 for 400 and the RT-80 for 450:

Online forums seem awash with really contradictory stories about stiffness around the BB with PX frames - some say the noodliness is their forks, some say its bad batched and just needs a return, some say its PX in general. Does anyone here have any 1st hand experience of PX carbon frame stiffness? For info I'm under 60kg and will be going for a small most likely.


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Post by jdtate101 » 24 Jan 2017 11:42

Only had one PX bike frame and that was a Stealth TT. It was pretty basic and rode ok, however the frame was rather flexy under heavy load. This didn't bother me too much as how often do you really sprint on a TT? However for a hill climb bike with all the watts and torque going through the frame...I'd say the stiffer the better. See if you can find someone with an example, stand alongside it and grab it by the head tube and seat tube, then put one foot on the BB area and push with your foot whilst pulling back gently with both hands. It shouldn't flex and if it does then don't use it.

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Post by gmac » 24 Jan 2017 13:24

Hi David
At 60kg unless your knocking out 600w I personally wouldn't worry too much.

Best Gary

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Post by Tim » 24 Jan 2017 13:41

Agreed with Gary any would do the job. I hired a pro carbon for a day in Tenerife a few years back and loved it although I didn't do any max climbing effort.

John Hitchcock who won our club hill for years on the run until recently did it on a hillclimb specific bike with a fixed gear, think on a 1970s steel frame.

So the fixed gear which means no rear brake or derailleur or gears etc is what will really save you the weight I'm guessing but I'm no expert in this!

I've just bought a px track frame but not ridden it yet but a third of the bikes ridden in track leagues are px.
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Post by Yosser » 24 Jan 2017 14:32

I have never done any testing so this is anecdotal, with all the usual caveats.
Bought a used PX TT bike last year. I weigh 80 Kg. No perceptible flex. I put out a fair amount of power given my weight. Impressed enough to buy PX Stealth for my wife to ride the European and Worlds triathlon champs. Feel free to come and examine either of these machines and see what you think.

This year I am riding the track a lot. Vast amount of PX track frames around with a lot of power going through them. There is some criticism on line and I didn't go for the PX track frame but I am putting out over 1000 W in a sprint so bought a specialist track machine.

I am inclined to go with Gary on this. However "caveat emptor"


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Post by Rod Goodfellow » 24 Jan 2017 15:05

I use both PX carbon Pro road and Stealth bikes and have never noticed any flex,but then I am 76kg but old and weak. However my son Peter (who some of you may remember as a Beacon sprog member in the early 70s!) is now a national class triathlete and using a Stealth without problems.He is 6ft 5.5 and 80 kg and can churn out over 1200 watts uphills.

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Post by John » 24 Jan 2017 16:08

It depends on the course if a fixed gear is beneficiail.

With technological advances you can get incredibly like road bikes these days. A friend built on that weight 4.5kg!

My Scott Foil (aero frame) was sitting at < 7kg when I did the national hill climb and I don't have the lightest wheels.

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Post by George » 24 Jan 2017 17:52

I've got a PX Pro Carbon. I'm no powerhouse, and therefore not the sort of person who would feel any bendiness very much, but I barely notice any bendiness at all. I've never owned a very expensive frame, but my PX handles just as well as more expensive carbon and steel frames that I have ridden. The only negative I can think of is that it's not as light as some upmarket frames, which might make it worth spending more if you've got it. But, if you want value for money, I'd recommend PX every time.

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Post by Lapin » 24 Jan 2017 19:39

Wow, thanks for all the replies!

I've got plenty of time to mull this all over before the HC season starts so I'll see if I can't wrench around a friendly Beacon rider's frame if I come across one.

I agree about the hill determining whether fixed is a good idea or not - horses for courses and all that. I also agree that geared bikes these days can be insanely light but the cost really goes up too (not to mention actually having to pay for the groupset). Having said that I saw a second hand Trek Madone 5.5 that came in at 5.5kg go for 600 quid, guess if you're willing to take a punt on second hand carbon there are plenty of deals out there.

Lots of food for thought, thanks!

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