Puzzled...Jamis and Norco
09-05-09, 07:17 AM
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Puzzled...Jamis and Norco
Dear all, have a question for frame geometry folks here.
I bought a Jamis Quest last year, a Reynolds tubing bike, put carbon seatpost and a nicer set of Easton stem/handlebar on it (100mm/-6/42cm). It rides beautifuly, in fact I came third in a local criterium about two months ago. It's riding on OEM Mavic Aksium Race.
I have my old Norco CRR Ultegra, taiwan carbon frame, nothing special. I have more or less the same set up. EA70 all the way around. Mavic Cosmic Elite wheelset.
However, the Jamis is a 50cm, and I believe the Norco is their "M" frame, which means it's something like 54cm. I can't sprint like I have fire up my ass on one of them, not at all with the other one. Is this a feeling that is created by the steel in the Jamis? or is there something realistically messed up about the geometry.
the two frame's geometry are available on https://www.jamisbikes.com/catalog_ar...IS_CATALOG.pdf and https://www.norco.com/2006bikes/bike_...gra&col=carbon
Any help or suggestions would be greatly appreciated.
I bought a Jamis Quest last year, a Reynolds tubing bike, put carbon seatpost and a nicer set of Easton stem/handlebar on it (100mm/-6/42cm). It rides beautifuly, in fact I came third in a local criterium about two months ago. It's riding on OEM Mavic Aksium Race.
I have my old Norco CRR Ultegra, taiwan carbon frame, nothing special. I have more or less the same set up. EA70 all the way around. Mavic Cosmic Elite wheelset.
However, the Jamis is a 50cm, and I believe the Norco is their "M" frame, which means it's something like 54cm. I can't sprint like I have fire up my ass on one of them, not at all with the other one. Is this a feeling that is created by the steel in the Jamis? or is there something realistically messed up about the geometry.
the two frame's geometry are available on https://www.jamisbikes.com/catalog_ar...IS_CATALOG.pdf and https://www.norco.com/2006bikes/bike_...gra&col=carbon
Any help or suggestions would be greatly appreciated.
09-05-09, 10:29 AM
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One possibility is the "slow" bike has more (too much?) trail than the fast bike.
Of my two main road bikes, one has a steep HTA and the other is more shallow (don't know fork rakes, but I'm assuming they're similar). The biggest difference between the two bikes is how they respond out of the saddle (ie, accelerating hard and standing to climb); the one with the steeper HTA leaps forward the instant I push on the pedals, the slacker HTA takes two or three revolutions before it wants to get going.
Not sure if this perception actually translates to measurable differences in rate of acceleration, but it certainly feels like it.
The "slower" bike also has longer chainstays, higher bars, aluminum frame (vs carbon), and is somewhat heavier, but I'm convinced that it's the trail that makes the biggest difference.
From: https://www.dclxvi.org/chunk/tech/trail/
"Note that a more stable bike will help the rider stay upright, but cannot be steered with as much precision. One reason track bicycles have less trail is because they are made for a precise ride rather than an easy one. A racer would rather have greater control and take responsibility for keeping the bike upright. This is especially important when the rider is out of the saddle and pushing hard on the pedals. At this time, the bike is being flipped rapidly from side to side, and if it has a large trail, it will wobble as it does so because the front wheel will turn with the lean."
Of my two main road bikes, one has a steep HTA and the other is more shallow (don't know fork rakes, but I'm assuming they're similar). The biggest difference between the two bikes is how they respond out of the saddle (ie, accelerating hard and standing to climb); the one with the steeper HTA leaps forward the instant I push on the pedals, the slacker HTA takes two or three revolutions before it wants to get going.
Not sure if this perception actually translates to measurable differences in rate of acceleration, but it certainly feels like it.
The "slower" bike also has longer chainstays, higher bars, aluminum frame (vs carbon), and is somewhat heavier, but I'm convinced that it's the trail that makes the biggest difference.
From: https://www.dclxvi.org/chunk/tech/trail/
"Note that a more stable bike will help the rider stay upright, but cannot be steered with as much precision. One reason track bicycles have less trail is because they are made for a precise ride rather than an easy one. A racer would rather have greater control and take responsibility for keeping the bike upright. This is especially important when the rider is out of the saddle and pushing hard on the pedals. At this time, the bike is being flipped rapidly from side to side, and if it has a large trail, it will wobble as it does so because the front wheel will turn with the lean."
