Geo Question: Does top tube length matter anymore?

[slowpoke]

Are you talking about TT length, or effective TT length?

Because with sloping TTs, basic TT length has become a useless measure unless both frames have the same TT slope.

But it's easier to just compare geometries on BikeInsights; esp when they have a nice visual reference.

[Alistair]

Originally Posted by bicycletricycle

Yes, if you care about what your seat post looks like

You don't find this attractive?

[fourflys]

I still look at TT (effective if needed) as it seems relevant to me.. I do look at stack and reach, but, as said by someone else, you have really consider the stack and then, it starts to blur for me..

[Bob Ross]

Originally Posted by XXtwindad

But, in theory, if I ride a bike with a 580 TT using a 110 stem, then I should be able to ride a bike with a 570 TT using a 120 stem. Is that accurate?

My (admittedly very limited) understanding of bike geometry tells me that while both of those bikes will "fit" you, they will handle differently, because those two scenarios put the wheels and steering axis in a different location relative to the rider's contact points.

[Dave]

I pay no attention to TT length anymore, but I do correct the reach so it's measured at the same stack height. I also know that 74 or 74.5 degree STAs will work best for me. If it's 75 degrees, I'd need a 32mm setback post.

[fourflys]

Originally Posted by Bob Ross

My (admittedly very limited) understanding of bike geometry tells me that while both of those bikes will "fit" you, they will handle differently, because those two scenarios put the wheels and steering axis in a different location relative to the rider's contact points.

not sure if this is exactly what you were getting at, but I think the idea that a "too long" or "too short" stem affects the handling of a bike to any great degree is way overplayed.. as far as where the rider is placed on the bike being a matter of a CM here or there, I think that only matters if you get on the bike and never change your position while you ride.. that pretty much never happens on a road, gravel, or MTB.. maybe on a TT..

at least that's my .02 and worth almost that much..

[wallymann]

you cant get to reach w/o TT.

[Dave]

Originally Posted by wallymann

you cant get to reach w/o TT.

Reach is a horizontal length from a vertical line through the center of the BB to the top-center of the upper headset bearing. STA only affects your choice of seat post setback needed to achieve your desired position relative to the BB center. The top tube length plays no part in this.