Sloping top tube?

and someone with 20,000+ posts says no.....you may want to question how serious they're being. :)

I agree. Someone with 20,000+ posts should always say yes.

Giant Bowery >

That's perfect. I'll take it. But I'm no fool. I won't pay a penny over 1,000GBP.

I agree. Someone with 20,000+ posts should always say yes.

I agree.

Fair enough, I can see where youre all coming from. It seems completely logical that the top tube angle and height of head tube bears no influence on HT ST angles and therefore no effect on handling of the frame. The reason for this whole thread is because I presented my idea to a shop that provides custom built frames only to be told in the most matter of fact way that what I'm asking for will simply not work. It sounded stupid to me too and made no sense, so I thought the people on this forum would set me right, and you have. thanks.

FFS....

You've just shown examples of the very thing you're asking if it's possible to achieve!

Not quite, the original illustration at the start of the thread has a taller head tube. I was told against my better assumption that extending the height of the head tube and relaxing the angle of the top tube would produce a crappy ride.

someone with 20,000+ posts says no.....you may want to question how serious they're being. :)

Hippys response and my gratitude were both kinda tongue in cheek

this thread is funny

:)

but on a serious note am a little worried that your frame builder said that..

who is it? how much? i would go somewhere else who has tube bending facilities.

I can see where the frame builder is coming from.

Compact geometry equals a really small/stiff rear triangle. Ride quality is still ok because the seatpost is relatively long. The plan set out in the OP is the opposite and would result in a really short seatpost, and maybe a pretty crap ride, with none of the aerodynamic benefits that lo-pros are all about.

I think the frame builder may have refused to build it because they can't see a good reason to.

It'll look good though!

I can see where the frame builder is coming from.

Compact geometry equals a really small/stiff rear triangle. Ride quality is still ok because the seatpost is relatively long. The plan set out in the OP is the opposite and would result in a really short seatpost, and maybe a pretty crap ride, with none of the aerodynamic benefits that lo-pros are all about.

I think the frame builder may have refused to build it because they can't see a good reason to.

It'll look good though!

+1

Frame builder has probably refused to build/said it's not possible as they do not want to have their name associated with a frame that has strange geometry that a lot of people will fail to see the point in and if anyone rides it they will think that the ride quality is pretty poor because of the shorter seatpost etc and presume this is the builders fault rather than realise that the frame has been built to specific requests.

The image in the OP is a bit misleading. Its just a pic I found & changed the angle of the TT- it only roughly illustrates the top tube and head tube. The actual seat tube will be between 59-63cm with 10-15cm of seat post.

I'm not getting my idea across very well.
Seeing the builder again tomorrow so we'll see...

this is a bit more accurate.

I have a curved seat tube going spare.

Look, let's have a quick pole. Who on here is a frame builder?

(no one raises their hands)

Ok, how many people told you this is possible, but you should... talk to a frame builder?

At least two.

Geek house or Affinity would be able to help you, hell, I reckon even 14 would be able to help you work out your exact bike.

Or go take Dave Yates' frame building course and see how it rides once you've built it.

Oh, and I want £150 for my 531 curved seat tube. I'll even throw in the top tube if you like. It's from a cracked 1960's Jack Taylor.

does anyone else think the curvy seat tube on the geekhouse looks all bulgy and wrong?

Yes. And after extensive research, I can tell you why. Partly it's because of the thicker tubing, KHS and Jack Taylor used skinny tubing.

Also, The curve ends exactly on the BB shell, the taylor keeps the curve running so that the line continues along the back side and looks like it creates the bottom bracket shell.

Any other theories?

I have a curved seat tube going spare.

Look, let's have a quick pole.

Was that a pun? Or is this just a pipe-dream...

.

Anti-capitalist.

Bump.
Because this thread is full of awesomeness, it deserves to be awaken from teh dead.
Another question regarding geo and slopingness.
I'm on the process of design my own frame, much inspired by this one; trying not to be a copycat...
this just happens to be one of my fav geos I've seen, and since I've managed to have someone custom building wha'eva I want, I've decided to give it a go.

Now,... this is what I've achieved so far: the ST and HT angles are the typical track (according to most track bikes found online), should I be using angles like 73 in order to get a more comfortable ride? The fork
has 15mm of rake, and the TT has a downward sloping (from the HT), of 3.5 degrees. I much prefer sloping like this 'cause of my standover-height is only 830mm (and i'm 6'1").
Any comments would be appreciated, flaming and mocking is also welcome, i just feel like a tool doing this for the 1st time with very little knowledge when it comes to geometry.
thanks
N

Anti-flame suit is on

1 Attachment

15mm of rake is unusual, but having never tried it can't comment.
I personally would go for a STA of 73 as 75 just pushes me too far forward and I need to put my seat past it furthest point on the rails.

That's what I was thinking, a 73 angle might be more appropriate... the fork rake might has to change, like i said, need some wisdom advice here...

Why have the seat stays joining at the top of the seat tube? Why not join them at the top tube?

Why have the seat stays joining at the top of the seat tube? Why not join them at the top tube?

Unless it means that it weakens the structure, the way I've put it, i won't change. I see what you mean, but aesthetically i prefer it this way.
That reminds too much of TT frames, where those seat tubes bits are very common.
Few examples of what I'm after:
here
here
here

You need to work out your trail. HT angle and Fork rake are linked for a given type of handling.

You want a trail of around 58-62mm for 'track handling'.

So, if you are set on a 15mm rake (where did you find one of those) then you need a HT angle of about 77 or 77.5

A 74 HT with a 15mm fork would be un-ridable, trail in the 80mm region, like trying to steer a shopping trolly

TBH it doesn't sound like you should be designing your own frame? Perhaps talk to whoever is building it about what you want, and let them figure out the geo?

TBH it doesn't sound like you should be designing your own frame? Perhaps talk to whoever is building it about what you want, and let them figure out the geo?

I won't, they asked me to decide the main lenghts/angles, and because the builder is outside the UK, this is my only way of doing iT.... Just decided to give it a go, they will never fully compromise with what i've done here.. Thanks for the advice ; )
Still i would like to understand what they'll do, if I can.

I've heard it said that this arrangement will make more flex/comfort for the rider. (I mean the stays above the TT)

asm you had a lo-pro Dave Yates frame with a similar arrangement, right?

i wouldn't say it would be unrideable with 15mm rake and 74 headtube, as my bike is close to that at the moment, with modified bmx style forks.

it sounds like a bmw gangsta with the seat stays further up the seat tube.