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esther-L 11-24-13 09:11 PM

How to determine how geometry changes the feel on a hybrid bike
I have been riding a road bike for about 8 years, and am shopping for a hybrid to use on gravel trails. I am not comfortable riding on gravel with drop bars. I am 5' 6" with a very short torso. I have a leg strength problem, and have been working on figuring out which muscles need to be strengthened so that I can do the "power position start".

I test rode a Jamis Coda Femme 16", and a Specialized Vita medium. Both have 700c wheels, same crank length.
Although the Vita is 2 lb heavier, it was easier to get it started from a stop.
Bikes are not at the same dealer, of course.

I am trying to figure out how geometry works with my leg strength problem. Starting from a stop is a problem for me. What is it about the Vita that makes it easier for me to get started (apply force to the pedal when it's at 3 o-clock), where I cannot do that on the Coda?

The geometries of these 2 bikes are very similar. I am wondering if the fact that it was easier to start the Vita is due to something that can be adjusted on a bike, or due to something basic like BB height or chainstay.

Jamis' website says BB height is 285mm. The geometry chart for the Vita says B-B drop is 70mm. To calculate BB height on the Vita, would that be 350mm-70, giving 270mm?
Chainstay on Vita is 10 mm longer, wheelbase is 29mm longer.

I know that one difference is the Jamis has 10 degree stem rise (stock) and the Specialized has 20 degree.
I suspect the seat on the Jamis was too far back for me (didn't look at that on test ride).

I really like Jamis bikes. My lovely well-fitting road bike is a 51cm Jamis femme model with an adjustable stem to get the handlebars a bit closer to me.

Does anyone have advice about whether my 'stronger start' is better on the Vita because of factor X in the geometry, or advice for how I can determine this on the next test ride?

Darth Lefty 11-25-13 12:53 PM

Just being lower / longer is going to make the Vita feel more stable.

Since the Vita is lower it might just be that your knee is less folded up on the one side when your foot is down on the other side.

Also, the gearing might be different between the versions you rode, giving you either more speed or less resistance from a start.

esther-L 11-26-13 09:11 PM

That is a good point about the 3cm longer wheelbase on the Vita. I was not certain if I had figured out the BB height correctly.

My ability to push down is more about my position on bike. I think the lower BB height may be what is helping me.

The gearing is different between the 2 bikes. I was not in the lowest gear on the Vita (lowest is 21.7 gear inch from Sheldon Brown gear calc). I think I was in 26 ring and 24 sprocket. On the Coda I was in the lowest gear, which is 23.4 gear inches.

Road Fan 11-29-13 06:28 PM

How well you can push down on the pedal could be affected by seat tube angle. If you have the saddle height (essentially your leg extension ability) set the same on both bikes, and one of them has you placed a little farther behind the BB than the other, that could affect how your leg and gluteal muscles combine to give some initial push.

Recycle 12-04-13 01:35 PM

Check the height of the handlebars. The head tube length is 105 on the Jamis , and 150 on the Specialized. If the difference in handle bar height is also 45 mm (1.8 in) it could be that you are able to get more support with your arms on the Specialized.

Here are two other thoughts on making it easier to step down on a pedal in the power start position:
1) To echo DarthLefty's comment, it might help to drop down a gear or two on the cassette. That way there isn't as much resistance when starting.
2) It might help to put the pedal in the 3 or 4 o'clock position rather than the 1 or 2 o'clock position. That way you don't have to step up as far to get rolling on the bike. A shorter step up might also be the case if the BB was really lower on the Specialized.

esther-L 12-10-13 08:17 PM

Thanks for the input.
I bought a Specialized Vita. Just before several days of cold wet weather! Hope to have some non-rainy weather on Sunday.

fietsbob 12-11-13 03:18 AM

and there's trail .. HTA/ fork steerer axis line, to the ground crosses the plumb line down from the axle ,
above the ground, the difference, between those 2, as seen on the ground, is the Trail .

Road Fan 12-13-13 02:39 PM

I'd agree with Fiets, and not just on the techy side of trail. Trail can affect how stable the steering feels, and that can affect how confident you are in cranking down on the pedal.

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