if having to buy a bike on frame measurements alone, whats MOST important?

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martinn
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Re: if having to buy a bike on frame measurements alone, whats MOST important?

Postby martinn » 27 Jul 2020, 10:33pm

fastpedaller wrote:
slowster wrote:
martinn wrote: i would be inclined to go with the steel except in the images it seems to have many bosses on it which as I will be running a standard drop rim brake, are a bit, for me superfluous, and i don't like the look of them

Does anyone have a Spa steel fork, or a better picture than the one on the website?

The steel fork for the Audax Mono is 725, whereas the steel road fork which Spa sell separately, but describe as suitable for use on their Audax bikes, is "quality cro-mo". That suggests that the 725 fork is new, and I suspect that it might not have the rack bosses.


It all looks a bit vague...... I'd ask Spa directly.



Thanks for pointing that out slowster, i hadn't seen that they were described differently, i made an assumption that it was the same as they currently offer.

De Sisti
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Re: if having to buy a bike on frame measurements alone, whats MOST important?

Postby De Sisti » 28 Jul 2020, 9:53am

531colin wrote:Seat tube angle is my "must be right" number..

How would the un-initiated know what seat angle is correct for them?

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531colin
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Re: if having to buy a bike on frame measurements alone, whats MOST important?

Postby 531colin » 28 Jul 2020, 12:15pm

De Sisti wrote:
531colin wrote:Seat tube angle is my "must be right" number..

How would the un-initiated know what seat angle is correct for them?

Heres what I wrote....
531colin wrote:Seat tube angle is my "must be right" number. It governs how much difficulty you will have in getting the saddle far enough back, or even if that will be possible at all......

If you have had a bike where you struggle to get the saddle far enough back, don't then go and buy a bike with a steeper seat tube angle than that.
As somebody posted, one degree on the seat tube angle is worth about 10mm of saddle setback.
If you never struggle to get the saddle far enough back, its happy days, modern bikes must be designed for you!
Where is the difficulty?

De Sisti
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Re: if having to buy a bike on frame measurements alone, whats MOST important?

Postby De Sisti » 28 Jul 2020, 1:17pm

531colin wrote:
De Sisti wrote:
531colin wrote:Seat tube angle is my "must be right" number..

How would the un-initiated know what seat angle is correct for them?

Heres what I wrote....
531colin wrote:Seat tube angle is my "must be right" number. It governs how much difficulty you will have in getting the saddle far enough back, or even if that will be possible at all......

If you have had a bike where you struggle to get the saddle far enough back, don't then go and buy a bike with a steeper seat tube angle than that.
As somebody posted, one degree on the seat tube angle is worth about 10mm of saddle setback.
If you never struggle to get the saddle far enough back, its happy days, modern bikes must be designed for you!

I think a lot of the 'experts' on this forum think everyone (eg, beginners and un-initatied) should know all
about seat angles. Perhaps all of the info above should be on noticeboards in bike shops to assist people
in buying an appropriate and comfortable bike for them?
Last edited by De Sisti on 29 Jul 2020, 9:06am, edited 1 time in total.

alexnharvey
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Re: if having to buy a bike on frame measurements alone, whats MOST important?

Postby alexnharvey » 28 Jul 2020, 3:22pm

That wouldn't be very good for sales...

Manc33
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Re: if having to buy a bike on frame measurements alone, whats MOST important?

Postby Manc33 » 28 Jul 2020, 3:32pm

For me personally it's the effective top tube.

Get that wrong and everything else that might not quite be an exact fit, pales in significance.

No amount of messing with stems, seatposts and saddles can fix it, ask me how I know :lol:
When two cyclists get married, they should throw anodized cable crimps instead of confetti.

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NATURAL ANKLING
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Re: if having to buy a bike on frame measurements alone, whats MOST important?

Postby NATURAL ANKLING » 28 Jul 2020, 3:51pm

Hi,
Stupid aint it :P

I have four bikes I ride
One has the saddle all the way back :?
Was originally 45 mm now 60mm because I always ride with same set back on all bikes.
Because it was the fashion to have the seat forward on that type of road bike in the eighties.......
Other three have the saddle all the way forward :?
Because I went a frame up on size and just scrape in, tourer.
The other two are LARGE mtb frames (24" ETT) with slack laid back seat tube angles as per the fashion of very long ETT, but I have long body and arms so I need a 6' 3" bike frame to get the reach or its 150+ stems :(

BUT the flippen BB is set in stone, so you have to work that as the datum...............?

Yes I know you can get far out seat pins to correct.
NA Thinks Just End 2 End Return + Bivvy
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PH
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Re: if having to buy a bike on frame measurements alone, whats MOST important?

Postby PH » 28 Jul 2020, 4:22pm

Manc33 wrote:For me personally it's the effective top tube.

Unless you know the seat tube angle you don’t know what that measurement represents.

mercalia
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Re: if having to buy a bike on frame measurements alone, whats MOST important?

Postby mercalia » 28 Jul 2020, 4:29pm

Brucey wrote:seat tube angle, ETT, head tube height above BB, in that order. Then other stuff like BB drop, front centres, etc.

cheers


Reach from saddle to the handle bars. If too short you will find you will be placing too much weight on the hands. Some saddles have limited adjustments to push back

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531colin
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Re: if having to buy a bike on frame measurements alone, whats MOST important?

Postby 531colin » 28 Jul 2020, 6:53pm

De Sisti wrote:.........
I think a lot of the 'experts' on this forum think everyone (eg, beginners and un-initatied) should know all
should know about seat angles. Perhaps all of the info above should be on noticeboards in bike shops
to assist people in buying an appropriate and comfortable bike for them?

Yebbut you need some experience of riding to know what works for you..
A 70 year old is a very different proposition to a 20 year old with fire in his eyes.
"Bike fitters" can charge over £100 for a "fitting".....and even then I have a suspicion that some bike fitters simply shoe-horn their customer into some sort of "average" riding position, using formulae based on body dimensions and other dubious practices.
Kind of difficult to put all that on a notice board.
Does anybody not have a cautionary tale of an absolutely appalling "bike fit" done by a random shop?

Manc33
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Re: if having to buy a bike on frame measurements alone, whats MOST important?

Postby Manc33 » 29 Jul 2020, 8:05am

PH wrote:
Manc33 wrote:For me personally it's the effective top tube.

Unless you know the seat tube angle you don’t know what that measurement represents.


You do, that's where the "effective" part comes in. It's effective from the top of the head tube, parallel to the ground, to however far up the seatpost that happens to end up being. In this case, the seat tube angle doesn't matter. If the seat tube angle is small then you're sat more behind the pedals, but that's another thing, separate from the reach to the handlebars.
When two cyclists get married, they should throw anodized cable crimps instead of confetti.

reohn2
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Re: if having to buy a bike on frame measurements alone, whats MOST important?

Postby reohn2 » 29 Jul 2020, 8:59am

Manc33 wrote:
PH wrote:
Manc33 wrote:For me personally it's the effective top tube.

Unless you know the seat tube angle you don’t know what that measurement represents.


You do, that's where the "effective" part comes in. It's effective from the top of the head tube, parallel to the ground, to however far up the seatpost that happens to end up being. In this case, the seat tube angle doesn't matter. If the seat tube angle is small then you're sat more behind the pedals, but that's another thing, separate from the reach to the handlebars.

To take that to it's logical conclusion,if you have a 90degree seatube angle it's OK so long as the ETT length is what you consider correct.
That clear isn't the case as it would place the saddle directly over the BB and throw the great majority of rider's weight onto the hands.

The body needs to be balanced which means the rider's weight needs to be behind the BB,the saddle to BB relationship is crucial to achieve this,it then follows that the first dimension to consider is seatube angle.
And as the many threads on the forum testify,that angle is often too steep for a lot of riders to get comfortable,throw a Brooks or similar saddle into that mix and things become even worse.
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rotavator
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Re: if having to buy a bike on frame measurements alone, whats MOST important?

Postby rotavator » 29 Jul 2020, 9:15am

the first dimension to consider is seatube angle.
And as the many threads on the forum testify,that angle is often too steep for a lot of riders to get comfortable


So can you give us the benefit of your experience and say what is your ideal seat tube angle for different groups of riders and bikes, e.g. old folk on drop bar tourers, youngsters on bikepacking bikes, mamils on racing bikes, commuters on hybrids?

I remember CJ recommending 72 deg as the ideal for touring bikes but that is as much as I know.

reohn2
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Re: if having to buy a bike on frame measurements alone, whats MOST important?

Postby reohn2 » 29 Jul 2020, 9:25am

rotavator wrote:
the first dimension to consider is seatube angle.
And as the many threads on the forum testify,that angle is often too steep for a lot of riders to get comfortable


So can you give us the benefit of your experience and say what is your ideal seat tube angle for different groups of riders and bikes, e.g. old folk on drop bar tourers, youngsters on bikepacking bikes, mamils on racing bikes, commuters on hybrids?

I remember CJ recommending 72 deg as the ideal for touring bikes but that is as much as I know.

It needn't ever be more than 73(small sizes,with the odd exception) or slacker than 70degrees at he other end of the scale.
Last edited by reohn2 on 29 Jul 2020, 10:41am, edited 1 time in total.
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PH
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Re: if having to buy a bike on frame measurements alone, whats MOST important?

Postby PH » 29 Jul 2020, 9:47am

Manc33 wrote:If the seat tube angle is small then you're sat more behind the pedals, but that's another thing, separate from the reach to the handlebars.

OK, I thought you'd misunderstood it, but you haven't.
The difference is I don't see it as a separate thing, the effective measurement for me is where I'm sat on the bike rather than the bike itself. I want to be in the same place in relation to the pedals and the bars, and to get that I need to match the combination of seat tube angle and ETT (+/- any adjustment in saddle/seatpost at one end and stem/bars at the other)