Confused on the stack and reach on 2 bicycles

[samsbike]

I need some help please.

I have some basic geometry information and I am trying to understand the differences in the actual stack and reach

Bike 1 Bike 2
Head Angle (°) 72 72.7
Head Tube Length (mm) 135 200
Effective Top Tube Horizontal (mm) 565 569
Seat Angle (°) 72.5 72.7
Seat Tube Length Centre to Top (mm) 540 566
BB Drop 66 69
Chainstay Length 415 435

From my limited knowledge given the specs I think the reach will be 4mm longer as the STA are virtually the same, although I dont understand how the the HTA will effect anything.

Also I will be showing a lot less seat post - 3 cm?

The big issues will be the headtube length which is long and even longer as bike 2 runs slightly more clearance up to 45 c tires rather than the 35c on bike 1.

Am I correct or am I missing something?

thanks

[RonK]

Plug your numbers into this calculator.

[531colin]

Within the degree of accuracy you need to worry about for these things, the 2 bikes are the same.
72 and 72.5 deg seat angle...no real difference....unless you are at the end of a Brooks saddle rails.
565 and 569 top tube.....a blind man on a fast horse would be very pleased to see the difference!

But just a slight conundrum on reach....
a taller frame (taller head tube) will have a shorter "reach" because its measured vertically from the BB, and the head tube isn't vertical....
But if you will put the bars at the same height, what happens is the spacer stack has the same angle as the head tube......

[Spinners]

The difference in head tube length gives me an uneasy feeling...

[samsbike]

as it does me. I just measured from the bottom of headtube to the bottom of my stem on the current ride and its about 18cm. Two cm more is a lot - I guess I may use the drops more

Although the other side of the coin is that I am running a 90mm stem and this may allow a longer stem say 100 with compact bars

[RonK]

Pretty clearly bike 2 has a taller stack and this will likely result in a higher bar position, effectively shortening the reach as illustrated in this article by Tom Rivendell. If you are looking for a comfortable fit, this is probably a good thing, and since you mention 35c and 45c tyres, we are are obviously not talking about a racing bike and an aggressive position is not required.

[531colin]

............... I just measured from the bottom of headtube to the bottom of my stem on the current ride and its about 18cm. Two cm more is a lot - I guess I may use the drops more .............

You can always use a "negative rise" stem (I hate that term!)


http://www.sjscycles.co.uk/cinelli-cinelli-pista-1-1-8-inch-stem-65-deg-318-mm-clamp-prod31617/

[samsbike]

I think I will ride the other bike when I can and see what it feels like. I have not had high bars for awhile and I may even enjoy it!

Oddly enough the specialized roubaix has a 19cm headtube which is huge as well (for a 56cm sized bike).

[RonK]

I think I will ride the other bike when I can and see what it feels like. I have not had high bars for awhile and I may even enjoy it!

Oddly enough the specialized roubaix has a 19cm headtube which is huge as well (for a 56cm sized bike).

What is odd about that?

The Roubaix is an endurance bike, so a higher stack is exactly what would be expected.

Here's a recent analysis I did of the current crop of endurance bikes compared to my road bike (Kuota Kredo) and tourer (Sabbath Silk Route). I'm developing arthritis in my shoulders and my road bike is becoming less and less comfortable, so I've been looking at bikes which are closer in fit to my tourer.



Oh, and if the manufacturer doesn't provide it, you can find stack and reach data for many other bikes in the Slowtwitch stack and reach database.

For your current bike measure the stack and reach this way: