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So my Sempre has exactly the same measurements - saddle to end of stem / bars etc - as my Defy, except for the following:
Headtube is 1.5cm taller on the Defy
Chainstays are 18mm longer on the Defy, as is the corresponding wheelbase
Bars are 2cm wider on the Defy
Head tube & seatube angles are 0.5 degree slacker on the Sempre
Now, the Defy feels planted but the Sempre twitchy - is this just the 2cm shorter (44cm e2e) bar thats causing the issue? its seems a drastic smount of nervousness in the bike for such a small thing...?
I can cope & ride with OK but I'll be using it tomorrow with TT bars so am nervous of it.
Thanks in advance
I wouldnt think it is handlebar length that makes it twitchy, more like geometry and lengths of the various tubes. Longer chainstay means generally more stable, and slacker geometry makes it stable to a point too, but you've got a mixture there.
I'd be more nervous about the impending low pressure system about to batter the UK and riding in 60+mph winds
Take & trail?
I wouldn't worry, more stable on tri bars
I wouldnt think it is handlebar length that makes it twitchy
Phew, I don't have another set so that's saved a purchase and keeps things a little more aero. Everything else such as stem, nose of saddle to stem etc is the same on both.
Take & trail?
?
think he meant rake, not take.
put a slightly longer stem on it - my equilibrium steering quickened up quite a bit with just a 10mm shortening of the stem.
I can cope & ride with OK but I'll be using it tomorrow with TT bars so am nervous of it.
Quick steering bikes with tri bars can be a handful (partly geo and partly the difference in weight distribution, i.e. lots over the front, i suspect.) They were hard work on my TCR, didn't realise how much so until I got the TT bike.
You practiced outdoors on it much?
I have tried taming twitchy bikes and as a result of my experiences I tend to think it is the frame and fork which are fundamental to the issue, so you won't rescue it. One man's twitchy is another man's sporty....I like planted.
So two completely different bikes handle completely differently.
Who would have guessed.
FWIW, it's angles and offsets you need to be looking at (which are fixed and frame specific), not your fit (which is you specific, but you seem to have changed it between the two bikes for some reason, ah well)
which is you specific, but you seem to have changed it between the two bikes for some reason, ah well)
Curious that people would think this unusual.
Most riders i know keep road bike set ups (training/race/spare/etc) the same, unless there is a very specific reason.
The bike coming with wider bars isn't a very specific reason. It's bad planning.
TBH I agree and do the same. Though I'd not find it unusual if someone set their bike up differently just for, say a 1hr crit as opposed to a much longer ride, trading off sustainability for aero.
Handlebar width seems an odd one though. Probably just what the bike came with!
Ah. But crit bikes are a specific reason.
Yes, I was just saying I agree 😉
The handlebar -44cm- was recommended after a bike fit vs my shoulder width. The OEM 46cm is on the Defy and only replaced the Giant OEM bar because it was lighter. I just never got round to buying a 44 for the Defy.
Mr Blobby - no, tomorrow is a 40k ride with several opportunities aka long straight ish roads on which I'll be trying it out. I'll let you know if I crash.
.
3 things:
I'd check the wheelbase, the offset on the fork may be different, thereby bringing the wheel closer to the frame, making it feel more twitchy.
Similarly, the head tube and seat-tube angles may be placing more of your weight over the bars than on the Defy, combined with the lower stack height on the new bike, you may have more weight over the front. If you have two sets of bathroom scale in your house, this can be checked.
Try altering the front tyre pressures +\- 10psi.
Mr Blobby - no, tomorrow is a 40k ride with several opportunities aka long straight ish roads on which I'll be trying it out. I'll let you know if I crash.
GoPro 🙂
Lol.
Daffy thanks - a quick measure reveals:
Wheelbase: Sempre 99cm, Defy 102cm
Fork at qr to crank centre : 60cm on both.
Handlebar height from ground: Sempre 94cm, Defy 96.5cm
Length of down tube from crank to outer heatube :Sempre 60cm, Defy 64cm
I think that makes the Defy a longer front centre at the top of the bike, yet the same at the bottom due to the 1/2 degree Steeper HA and longer head tube. Eg. It feels longer and slower to steer from the cockpit.
I'll try the tyre trick. I'm in 25's and usually run 100/100 psi some should be able to run 90psi in the front without too much damage to my massive pace 🙂
Note you'll have more weight over the front when on the tri bars so reducing the front tyre pressure will make a lot more difference than it might otherwise do.
You could try moving your hands slower?
I'm still upright!
Try altering the front tyre pressures +\- 10psi
Daffy thanks - I rode 90F/95R and the front was waaaay more confidence inducing.
Surprisingly the Bianchi feels more confident on the TT bars that the Defy did, despite todays wind. I am paranoid about things running out in front of me though (car doors, squirrels, people) and not being anywhere near the brakes. Fridays TT will be interesting as its in the streets of London... 😯
Obligatory pic of the setup:
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Kryton57 - MemberDaffy thanks - I rode 90F/95R and the front was waaaay more confidence inducing.
Glad it helped. I've found road bikes to be surprisingly unforgiving of seemingly minute changes from what we're used to feeling on them.