Road bike recommendations

Yea but we are bike people, my misses isn't ;)

But she is married to a "bike person". As generally amongst hunting and gathering societies Its YOUR job to bring home tires and other game.

Also it got a very steep 76 degrees seat tube - meaning top tube is theorically longer (more like 53-54cm than 50cm) if you set it as a road/commuter.

Fuji is indeed strange. Their XXS with 650c has about the same equivalent reach as their XS with 700c wheels. Its not a good contender for a petit cyclist of average morphology.

Fully slick 26" tyres are available in halfords, they're that easy to find.

They'll all be shitty wire bead tyres with no road feel and a harsh ride.

Fuji is indeed strange. Their XXS with 650c has about the same equivalent reach as their XS with 700c wheels. Its not a good contender for a petit cyclist of average morphology.

Reach does NOT take seat tube angle into account, which is ever so important.

By the way, there is a huge small people 650 bike thread on this very forum.

Reach does NOT take seat tube angle into account, which is ever so important.

Yes it does

Yes it does

Lé no

Think again, you set your saddle position in relation to BB i.e. saddle setback. Therefore reach DOES take seat tube angle into account. And if you look at how the reach and stack are mathematically calculated it should ne pretty evident that the seat tube angle is taken into account...

STACK = BB_drop + (Axle_crown_ht + Head_tube_ht) * sin(Head_tube_angle)
REACH = Effective_top_tube – STACK / tan(Seat_tube_angle)

To be able to compare frames with different headset types one has to also take headset stack height into account when calculating stack.

Think again, you set your saddle position in relation to BB i.e. saddle setback. Therefore reach DOES take seat tube angle into account. And if you look at how the reach and stack are mathematically calculated it should ne pretty evident that the seat tube angle is taken into account...

To be able to compare frames with different headset types one has to also take headset stack height into account when calculating stack.

I really want to believe you

BUT!

The world is against you - everyone on the internet defines reach as this

Frame reach is the horizontal length from the BB to the center of the headtube

I really want to believe you
BUT!

Your quote is correct, that is how the reach is defined. However, I already presented you how reach (as per you quote) is achieved mathematically. Calculating reach and stack is simple trigonometry after all. You don't have to believe me, you can do the math by yourself.

Yeah trigonometry is always right :-)

BUT applied to the real world, things get funky
http://i256.photobucket.com/albums/hh167/edscoble/Photobucket%20Desktop%20-%20Edward%20Scobles%20MacBook%20Pro/6326849846_eba5a1c0da_b_zpsc904dc7c.jpg

I'm drunk and don't understand trigonometry, but even I can see that every bike on the right hand column has the same reach.

What's you're point?

Yeah trigonometry is always right :-)

BUT applied to the real world, things get funky
http://i256.photobucket.com/albums/hh167/edscoble/Photobucket%20Desktop%20-%20Edward%20Scobles%20MacBook%20Pro/6326849846_eba5a1c0da_b_zpsc904dc7c.jpg

But see, in the example image you posted you prove my point. On the left, when you keep the effective top tube length the same and change only the seat tube angle the reach is affected. On the right you have to alter both effective top tube length AND seat tube angle to preserve the same reach. I still don't understand how you can claim that seat tube angle does not affect reach when you post evidence that it does? :)

AFAIK 'reach' is specifically the measurement from the BB forward.

...therefore you need to look into BB height, saddle height and ST angle along with reach and all that.

But see, in the example image you posted you prove my point. On the left, when you keep the effective top tube length the same and change only the seat tube angle the reach is affected. On the right you have to alter both effective top tube length AND seat tube angle to preserve the same reach. I still don't understand how you can claim that seat tube angle does not affect reach when you post evidence that it does? :)

Note how the saddle has a different setback on every picture, to compensate for the different horisontal length to the BB, dependent on ST angle.

Note how the saddle has a different setback on every picture, to compensate for the different horisontal length to the BB, dependent on ST angle.

Saddle has the same setback on every picture (116mm). Now, how do you like your pie?

Saddle has the same setback on every picture (116mm). Now, how do you like your pie?

YES! - and therefore the the set back on the seat post is different on every picture to cancel out the effect of a different ST angle <== this

Saddle has the same setback on every picture (116mm). Now, how do you like your pie?

#nothelping

YES! - and therefore the the set back on the seat post is different on every picture to cancel out the effect of a different ST angle <== this

I guess I need to spell it out... People often say that Surly Steamrollers are low and long. Let's calculate reach and stack for size "59":

REAL:
STACK = 70mm + (375mm + 163mm) * sin(74) = 587.2mm
REACH = 587mm – STACK / tan(73) = 407.5mm

Now let's only change seat tube angle (from 73 -> 72 degrees) and see if that affects reach:

IMAGINARY:
STACK = 70mm + (375mm + 163mm) * sin(74) = 587.2mm
REACH = 587mm – STACK / tan(72) = 396.2mm

We see that one degree change in the seat tube angle is pretty close to 1cm change in reach when we don't change the effective top tube length as well. In this case reach is less, because more of the top tube is behind the bottom bracket. This is pretty well know fact and many bike fitters use it as a rough guideline.

Usually one wants to achieve the same fit triangle between different frames if the intended end use for the bikes is the same. In the example above, let's imagine that the saddle and handle bar are at the same level to make calculation more simple. To achieve the same fit triangle between the two Steamrollers above (real and imaginary) one would position the saddle to the same position in relation to bottom bracket (height and setback). We can use 80mm setback as an example. Then we would like to maintain the reach from the saddle nose to the center of the bars equal as well. Let's say that 600mm would fit the rider. To achieve this we would need different length stems for real and imaginary Steamrollers to compensate the difference in reach:

REAL: 600mm – 407.5 – 80mm = 112,5mm (roughly 110mm stem)
IMAGINARY: 600mm – 396.2 – 80mm = 123,8mm (roughly 120mm stem)

Seat tube angle clearly affects reach and one can easily see this from the formula. Seat tube angle is one of the variables ffs. Thuekr we are probably talking about the same thing but from different perspectives. However, if you claim that seat tube angle doesn't affect reach you are wrong. If the difference in reach between the two Steamrollers would be cancelled out by just using inline or offset seat post then we wouldn't need to change the stem length, right? But this is not the case because we want to achieve the same saddle setback and to achieve the same setback we (might) need different seat posts. To maintain the same saddle to bar reach we still need to compensate the change in reach with different length stem as well.

But you don't have to believe me, you can wait for some like mdcc_tester to come here and give he's input.

retard.gif

#nothelping

Nice attitude, read the previous posts as well. There is plenty of help there. Maybe I should return the favor ;)

STACK = BB_drop + (Axle_crown_ht + Head_tube_ht) *
sin(Head_tube_angle)
REACH = Effective_top_tube – STACK /
tan(Seat_tube_angle)

This equation is to derive reach from ETT, and vise versa. Its the ETT part that is STA dependent. Which is exactly what makes it less useful. If you keep the ETT constant, and change the STA. The only way this can happen is by moving the BB forward. Thus it will obviously change reach. Because reach is BB positon dependant.

So if you know the ETT. Yes, you need to know the STA angle to calculate reach. Which is why its a less useful figure. If you know reach, you dont need ETT or STA. The fit of equal 'reach' frames will be the same regardless of them.

Not arguing, just discussing ;)

Of course "reach" (as defined by Empfield) takes seat-tube angle into account since with a fixed top-tube as one increases the angle one shifts the orthogonal projection of the BB onto the top-tube backwards. With a constant stem length and saddle set-back as one increases the seat-tube angle-- which demands that the saddle be pushed back on the rails to keep the same constant set-back--- the distance to handlebars increases. The "Empfield reach" is, in this light, a good proxy for the personal reach as defined as the distance from saddle to handlebar: more "reach" generally means, assuming a constant saddle setback, more reach to the handlebars. The point of the Empfield "reach" was to define a proxy reach that could be measured on each frame.

The counter factor is the observation that as one steepens the seat-tube angle one also tends to shorten the stem, reducing the reach which allows one to look at the top-tube length as a parameter for comparison.

Everyone is right. We're just looking at it differently (friday love, peace, and double rainbows all round).

If you have a selection of frames with the same reach. They will all fit the same regardless of STA. You will always set everthing up to be sat in the same position to the BB.

Its when companys start quoting ETT that you need to bring in STA. I guess you could argue that if youre given reach, you need STA to calculate ETT. But why would you do that when reach is a better figure than ETT.

..... when we don't change the effective top tube length......

..... with a fixed top-tube.....

Stop fixing the ETT. It needs to change with the STA.

The argument is that reach is STA independant. But you need to be comparing frames of the same reach, and varying ETT, and STA as needed to illustrate this. As soon as you only vary one. Its no longer a relavent example.

This discussion could go on all day.

I'd rather drool over some mud pie........filthy.....gooey....stodgey....mud pie......hmmmmm