Originally Posted by
Moyene Corniche
All the bike measurements still don't illustrate how you are sitting / fitting on the bike.
The assumption with the stem length bit is that the contact points remain consistent. Any problems with the body's position is a separate one, meaning fit isn't the issue (since the different bikes presumably fit the same, once properly fitting bars/stem are selected and everything is adjusted).
The bar/stem thing concerns weight distribution over the front wheel. A shorter stem will almost always put the rider further back from the front axle (I suppose a 90 degree derny racing bike might be different).
Interestingly enough my top tube length is just 1 cm shorter than yours. I probably have a steeper seat tube angle (75.5) and even with that my saddle is forward. I imagine our reach is very similar, but my saddle height is much lower, about 67 cm from saddle top to center of BB. 175 cranks with Look Keos so about 16.5 cm to the pedal top, give or take, giving me about 83 cm saddle height. I'm 5'7" so 8" shorter than you in height.
Originally Posted by
thechemist
I won't ever go back to anything less than 110mm stem. Stability has been a huge confidence booster with a longer stem.
@
tetonrider it is interesting that you found a difference between the tarmac and venge descending/cornering. My future plan was always to drop a bike size and go with the venge over my current tarmac for several reasons. However, since adding length to my stem, I wonder if I had judged the tarmac too severely and perhaps will just drop a size for another tarmac.
Originally Posted by
tetonrider
this is interesting. your posts have really made me think. traditionally i've tweaked stem size in order to keep hoods in the same spot (same distance from the nose of the saddle). didn't really think about the curve of the drops when switching bars and how that affects weight distribution.
thanks for making me think!
with my crashes this season i've had lots of time to think about descents--and some issues with descending/cornering. some of the issues are mental and others are mechanical (e.g., my hip doesn't quite have the same fluidity of movement). i've noticed that despite the same geometry, one of my bikes (venge) seems prone to understeering just a bit whereas another bike (Tarmac) is spot-on. i currently have different-but-similar bars on them, but i suspect it could be some other property of the bike aside from pure geometry.
Personally I found that once a stem gets below 100mm it's a bit short for stability. This is based on troubleshooting the Missus's bike as well as test riding countless repairs and new bikes while at the bike shop.
There's a reason why I spec'ed out a 120mm stem as my base stem for a custom frame - it was to place my hands properly
relative to the front wheel. I figured out the top tube length based on that 120mm stem.
Of course that was with a normal bar. With a compact I really a longer stem. I've gone with a 145mm stem and it's been good (the bars are I think technically 28mm shorter in reach). With the compact I also needed to move the bars down 3 cm, so I had to do that as well. For me the only way was to do a custom stem.