Understanding frame geometry

General cycling advice ( NOT technical ! )
martinn
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Re: Understanding frame geometry

Postby martinn » 14 Jan 2018, 7:49pm

Thanks for all the replies,very helpful.
I have a mental image of what I am trying to achieve.

Many thanks
Martin

Now the problem is which material!!!!!

elPedro666
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Re: Understanding frame geometry

Postby elPedro666 » 14 Jan 2018, 9:39pm

martinn wrote:Now the problem is which material!!!!!


haha, definitely a thread in its own right!

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martinn
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Re: Understanding frame geometry

Postby martinn » 15 Jan 2018, 12:19pm

you have no idea of how many times I have gone round in circles over that one! But to be frank I have narrowed it down to one of two materials based on cost/ and if I already have a frame with that material.
So its Carbon or Titanium. (He dons hard hat for mentioning the "C" word)
( seen a Great deal on a GT grade adventure road bike with hydraulic disc brakes)
Martin

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NATURAL ANKLING
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Re: Understanding frame geometry

Postby NATURAL ANKLING » 16 Jan 2018, 1:36am

Hi,
If you are uncertain then steel would for sure be most reliable.
The others are unpredictable or extortionately expensive.
OK if you are being sponsored.
But for normal use isn't it an over kill? If not then you are buying on purely aesthetics.
I have sent one text on my mobile in six months and its an 11 year old model :)

Apart from the corrosion resistance of Titanium, it has that dull stainless appeal.
We seem to have moved on very quickly from Aluminium to CF and now Titanium.
I wonder if exotic materials and leather saddles will still be en vogue in ten years time.
NA Thinks Just End 2 End Return + Bivy
You'll Still Find Me At The Top Of A Hill
Please forgive the poor Grammar I blame it on my mobile and phat thinkers.

elPedro666
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Re: Understanding frame geometry

Postby elPedro666 » 16 Jan 2018, 9:16am

"Normal use"...?
Now you want to start another rabbit hole inside the current rabbit hole!

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reohn2
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Re: Understanding frame geometry

Postby reohn2 » 16 Jan 2018, 10:48am

Someone tell me what's wrong with steel,reletively cheap,lasts and rides beautifully and can be repaired cost effectively :)
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martinn
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Re: Understanding frame geometry

Postby martinn » 16 Jan 2018, 2:43pm

Dare I continue :D

I like steel, I have 3 steel bikes already, all doing different tasks, and different steels.( A tandem, heavy, a fixed 531, and an audax bike 853.)
I have an aluminium bike, which is my snow/ ice bike, good tyre clearances, but a hateful ride.
So looking a n+1 which would have to have discs, and would be billed as a winter audax bike, I was looking to change frame material as well, to expand my experience, and if I don't like it I could sell it on.

Martin
PS what's normal use?

reohn2
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Re: Understanding frame geometry

Postby reohn2 » 16 Jan 2018, 3:11pm

martinn wrote:Dare I continue :D

I like steel, I have 3 steel bikes already, all doing different tasks, and different steels.( A tandem, heavy, a fixed 531, and an audax bike 853.)
I have an aluminium bike, which is my snow/ ice bike, good tyre clearances, but a hateful ride.
So looking a n+1 which would have to have discs, and would be billed as a winter audax bike, I was looking to change frame material as well, to expand my experience, and if I don't like it I could sell it on.

Martin
PS what's normal use?

If an expansion of experience is you goal,by all means do whatever floats yer boat :)
Personally I'll stick with steel for the reasons given,call me a Luddite if you like,I don't mind :D
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martinn
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Re: Understanding frame geometry

Postby martinn » 18 Jan 2018, 7:35am

OK,
going back on topic again.

to get a comfortable and injury risk reduced ride, there is an optimum reach and stack. If I match this then the bike should be able to be fine tuned to fit me?

reohn2
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Re: Understanding frame geometry

Postby reohn2 » 18 Jan 2018, 9:23am

martinn wrote:OK,
going back on topic again.

to get a comfortable and injury risk reduced ride, there is an optimum reach and stack. If I match this then the bike should be able to be fine tuned to fit me?

From a riding position POV what matters are the contact points,so getthose in the right places and youll be comfortable,of course there's an optimum frame size for each individual.
FWIW I like the handlebar to be high and most frames to have to low stack height for a desired reach but is I were to go a size up the stack would be higher but the ETT is longer but that's OK because I can use a shorter stem,some will say but then the stem's too short to which I'd answer,choose your compromise,a lot of spacers under a long steered or a shorter stem.
A full custom frame would eliminate such compromise.
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elPedro666
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Re: Understanding frame geometry

Postby elPedro666 » 18 Jan 2018, 12:22pm

Think Reohn really has the crux of it there - if the reach and stack are appropriate then you can use the length/rise of stem which suits the handling of the bike, rather having to compromise handling in order to afford you a comfortable riding position. Ditto your pedalling position - setting how far your bum is behind the pedals without compromising the reach (or vice-versa).

Just as an example I've got short thighs and a relatively long torso, so as a rule prefer long frames* which allow me to move the saddle forwards and fit a shortish stem (I enjoy the quicker handling) without ending up being cramped. In some ways the opposite of the example above: variety's the spice an' all that!


*what I should probably have said is a greater reach:stack ratio, which may actually be the real knubbin of the whole deal...

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horizon
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Re: Understanding frame geometry

Postby horizon » 18 Jan 2018, 2:24pm

martinn wrote:OK,
going back on topic again.

to get a comfortable and injury risk reduced ride, there is an optimum reach and stack. If I match this then the bike should be able to be fine tuned to fit me?


No (IMV). The optimum reach and stack is what you find comfortable (there are other reaches/stacks that you might wish to adapt yourself to if for example you were racing but that's a different matter).

So, the bike is fine-tuned to your most comfortable/effective position. The result is the optimum reach and stack (for you). So I've turned what you suggested on its head (if I had understood you correctly).

However, you do have to give the bike a fighting chance of matching your desired position - you don't want to run out of adjustment (as 531colin said above).

So my advice would be that you find a bike that roughly matches your style of riding, choose the most likely size and then tweak like mad at home. You may even want to tweak some more over time.
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Re: Understanding frame geometry

Postby PH » 18 Jan 2018, 2:43pm

horizon wrote:No (IMV). The optimum reach and stack is what you find comfortable (there are other reaches/stacks that you might wish to adapt yourself to if for example you were racing but that's a different matter).

The often repeated advantage of drop bars is the variable hand positions, each of these effectively changes the reach. Indicates to me that reach is a range rather than a precise measurement. Something as simple as bending your elbow will have more effect than a few mm's on the top tube. I know I'm comfortable enough to ride long days on bikes with noticeable reach differences, but far less tolerant to changes in saddle to pedal relationship.
I have doubts that anyone ever finds a single ultimate position, we eliminate what doesn't work, then usually stop (Why wouldn't we?) but who's to say there might not be other equally good options?