Compact frame geometry

father_jack

I have a Giant OCR-1 in medium. I'm generally ok with it, however I don't think it's perfect in szie, I can't quite get on with "compact" geometry. I have changed from 120mm to 100mm stem as I was too stretched out with 120mm stem. I can see the front axle whilst riding, and I feel like I'm riding "over the front wheel" I feel if I apply front brake I'll go arse over tit, since I'm already fairly over the front wheel. Also I cannot ride on the drops at all it's not comfy. I have tried the OCR-1 in large but my goolies rest on the top tube.

I have a Genesis Flyer 56cm and that is perfect, and riding on the drop is comfy.

Apart from buying a larger frameset and transferring everything over is there anything I can do? It has Campagnolo Veloce groupset so probably want to keep those components

giropaul

Raise your bars? If the steerer has been cut off too short to let you do this try an upward angled stem.

Your position on all your bikes should be identical ( except very specialist things like tt bikes obviously). Measure your Genesis and replicate the measurements, especially saddle height and setback, reach from saddle to bars, and drop from saddle height to bar height.

father_jack

Ground to saddle will be different on the two bikes, as one uses SPD and another SPD-SL. I noticed when I went from SPD to SPL-SL I had to raise saddle.

imposter2.0

Father Jack wrote:

Ground to saddle will be different on the two bikes, as one uses SPD and another SPD-SL. I noticed when I went from SPD to SPL-SL I had to raise saddle.

'Ground to saddle' height is not really a useful measurement anyway, as it assumes the BB height is the same on both frames - which it may not be. BB to saddle is a more sensible measurement.

darkhairedlord

Put the bike on a level surface and use a spirit level and tape measure. Measure centre of bb to saddle vertical then horizontal. Don't measure to the saddle tip unless both are the same. Measure horizontal to where the saddle has a width of 80mm. Cut a slot in piece of card to use as a gauge and mark the saddle with some masking tape. Measure to the bars from bb in the same way if they are both the same, if not use a jig on hoods in the same way as the saddle. Again, this should mimic the contact point. If you do this both will feel pretty much the same even with different components.

taon24

Imposter wrote:

'Ground to saddle' height is not really a useful measurement anyway, as it assumes the BB height is the same on both frames - which it may not be. BB to saddle is a more sensible measurement.

I would suggest that Pedal spindle to Saddle is more useful as Crank length can also vary in length. I must admit though this is likely only by a few millimetres, and this can be corrected for in the BB to saddle measurement.

imposter2.0

taon24 wrote:

Imposter wrote:

'Ground to saddle' height is not really a useful measurement anyway, as it assumes the BB height is the same on both frames - which it may not be. BB to saddle is a more sensible measurement.

I would suggest that Pedal spindle to Saddle is more useful as Crank length can also vary in length.

That doesn't make sense. How is it more effective if it introduces another variable (ie crank length) ?

StillGoing

Imposter wrote:

taon24 wrote:

Imposter wrote:

'Ground to saddle' height is not really a useful measurement anyway, as it assumes the BB height is the same on both frames - which it may not be. BB to saddle is a more sensible measurement.

I would suggest that Pedal spindle to Saddle is more useful as Crank length can also vary in length.

That doesn't make sense. How is it more effective if it introduces another variable (ie crank length) ?

Because crank length is relevant to seat height. If the crank length is shorter by 2.5mm at the bottom, it's effectively going to give 5mm more clearance at the top of the pedal stroke once the seat is adjusted correctly. The reverse is also true.

imposter2.0

philthy3 wrote:

Imposter wrote:

taon24 wrote:

Imposter wrote:

'Ground to saddle' height is not really a useful measurement anyway, as it assumes the BB height is the same on both frames - which it may not be. BB to saddle is a more sensible measurement.

I would suggest that Pedal spindle to Saddle is more useful as Crank length can also vary in length.

That doesn't make sense. How is it more effective if it introduces another variable (ie crank length) ?

Because crank length is relevant to seat height. If the crank length is shorter by 2.5mm at the bottom, it's effectively going to give 5mm more clearance at the top of the pedal stroke once the seat is adjusted correctly. The reverse is also true.

Well obviously, but the BB is a fixed point and the pedal spindle isn't (it follows a radius). Simply add or subract any crank length difference once you have taken the measurement.

First.Aspect

You sound confused to me. Being too stretched out with a 120 stem, and having your goolies on the tt of a size L, both to me indicate that a larger frame is not what you need. The compact geo is irrelevant.

Comparing the geometries of the two bikes, the Genesis has a significantly longer wheelbase and slacker head tube angle. This may be what's giving you that "over the front axle" feeling on the Giant. Perhaps just the difference between a touring bike and a racing bike? The Genesis should feel more stable, the Giant more nimble in the turns.

Genesis actually has a tt 1cm longer than your Giant. So, unless you have a 90cm stem on the Genesis, something else is going on to make you feel too stretched out on the Giant. Could be the drop, could even be the bars.

The only way to get further behind the bb and front axle is to push the saddle back, or get a layback seatpost (if you don't already have one). That will mean you have to shorten your stem (which is already pretty short, btw) and/or raise it (which would put less weight over the front of the bike). But again I'd urge you to figure out how the contact points compare between the two bikes first. It might bean idea to take both bikes to a decent bike shop and let them figure out what's going on, before doing anything too dramatic.