I Wouldn't Buy One

[Serge]

Hmm, it does look a bit odd, but I suspect that it is a perfectly sensible setup. Give me a few minutes ...

Ok, with a bit of photo-manipulation, I give you 'My bike with the Planet X bike superimposed'!

View attachment 425504

Most of the apparently stupidly extended seatpost is due to the compact design of the Planet X frame. I have my saddle slightly nose-down for comfort. If I had the saddle level it would only be about an inch below the Planet X's saddle. Note - I have short legs for my height - only 32", which is not a lot for someone who is 6' 1" tall. If I had legs more in proportion to my torso, I would easily need my saddle as high as the Planet X bike's!

Excellent illustration, but it kind of reinforces the point @Drago made. That Planet X bike's frame is more likely to fail than yours.

 

[ColinJ]

Excellent illustration, but it kind of reinforces the point @Drago made. That Planet X bike's frame is more likely to fail than yours.

My bike certainly seems to be robust for lightweight aluminium. I have been riding it for 16 years at weights up to 17-and-a-bit stone and it is still soldiering on!

 

[Pale Rider]

Excellent illustration, but it kind of reinforces the point @Drago made. That Planet X bike's frame is more likely to fail than yours.

Brompton would give you an argument.

The seat tube/seat stay junction of which @Drago speaks is not even welded on a Brommie - it flops about.

The rear triangle is tiny, and the amount of exposed seat post could double as a broom handle.

Nothing to suggest Brommies are anything other than robust.

 

[Serge]

My bike certainly seems to be robust for lightweight aluminium. I have been riding it for 16 years at weights up to 17-and-a-bit stone and it is still soldiering on!

If that's the same bike that's in your avatar then it looks a perfect fit. I think with the Planet X, 90% of my weight would be on my arms and shoulders.

 

[FishFright]

I don't claim to be an engineer though I have had some training in the subject, but this looks like a poor design to me. That rear triangle is structurally unsound IMO, particularly if you have this much seat post exposed.

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That rear triangle design has been around for many years now and works fine.

 

[Oldfentiger]

My Merida carbon bike has that design rear triangle. I believe it’s to give more compliance to the ride.

 

[simonali]

Every time I see something like that all I think is "how the hell do you not go straight over the bars under heavy braking?".

Use the back brake?

 

[dan_bo]

could it be argued that is it's a race frame it's only gonna last a couple of seasons anyway?

 

[NorthernDave]

When I bought my last road bike, I was actually asked how much seat post I wanted exposed when trying one for size.

I'm a 'M' (53cm), but was advised to drop down to an 'S' (51cm?) if I wanted to ride with more seat post showing....fashion, eh?

I bought the 'M'.

 

[rualexander]

If it's been designed and engineered properly to be that shape with that amount of seatpost exposed, then there should be no problem.

 

[dan_bo]

If it's been designed and engineered properly to be that shape with that amount of seatpost exposed, then there should be no problem.

and there's the if.

 

[SkipdiverJohn]

...or just tall people. My full inside leg is 36".

So you need a 25" frame. A proper old-school steel one with a horizontal crossbar. None of that carbon rubbish.

 

[simon.r]

Unless your height is more towards leg than torso as is the case for lots of women

And some men, me included!

It’s taken me a while, but I’ve eventually come to the conclusion that top tube length is the most important measurement on a frame. I have bikes with seat tubes between 56cm and 65cm, but they all have similar top tube lengths.

Some have lots of seat post exposed, others less. I’ve not broken a frame yet (touches wood).

 

[Johnno260]

My Merida carbon bike has that design rear triangle. I believe it’s to give more compliance to the ride.

My Merida is a similar design but the seat stays aren’t as thin as those.

But if mine breaks I have a lifetime frame warranty, if the failure doesn’t kill me.

 

[Deleted member 1258]

That rear triangle design has been around for many years now and works fine.

Yes, but it looks far too flimsy, it's not a frame that I would be keen to ride.