Geometry questions

by Miles253   April 15, 2014  

Hey guys

I've got some rather specific geometry questions

The Cannondale Synapse 2014 has a head tube angle of 73 degrees and a wheelbase of 102.8cm in my size. The other bike I'm looking at continuously is the canyon SLX range. Comparatively it has a head tube angle of 73.25 degrees and a wheelbase of 101.4. Now in my understanding, a steeper head tube angle and shorter wheelbase often denote a more aggressive frame. Now in this instance am I wrong in saying that looking at geometry alone, the canyon is not any more aggressive then the synapse? If so then that's great, as I worry whether I'm flexible enough for a really aggressive frame.

Are there any other geometry factors I should be looking at before eventually choosing?

Thanks

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Are there any other geometry factors I should be looking at before eventually choosing?

It depends what you want to do with the bike

If you want a fast bike for real racing then you might rate faster steering
If you want to ride long distances then you want something more stable
I always want a more comfortable bike so I get a longer head tube and shorter top tube
If you want to do time trialling on it then there are probably factors for geometry for that

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posted by vorsprung [290 posts]
15th April 2014 - 14:45

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Reach and stack are the two main fit related geometry factors you could look at, which are related to horizontal top tube and head tube length (but also affected by frame angles).

Greater reach and lower stack height usually is what is meant by more aggressive geometry.

Speed of steering is only loosely related to head tube angle, trail and fork offset are more relevant.

From my reading of it the Canyon has about 25mm less stack height than the equivalent reach Synapse carbon, although the sizing is not directly equivalent. This suggests a more aggressive geo fit wise plus the Synapse has a huge conical spacer on top of the headset. So more flexibility and core stability needed for the Canyon, probably.

The usual suggestion is to go ride them but with Canyon that may take more effort?

posted by Nixster [73 posts]
15th April 2014 - 15:25

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I agree with Nixster. Of all the stats, I would look at stack and reach.

Cannondale Synapse Stack 631 Reach 402
Canyon Stack 598 Reach 406

if I have worked out the right bike sizes you were looking at.

I suspect you are comparing two different style of bikes. The Cannondale Supersix would be nearer the Canyon geometry. Why not have a go on the two Cannondales and you would know what style of bike would suit you.

Ride more, ride better

posted by Sniffer [126 posts]
15th April 2014 - 16:05

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Head tube angle and wheel base has little influence on the position that you can attain on a bike, its much more about handling.

As mentioned, reach is really important, as is the height of the front end.

The synapse has been developed with a high, short (ish) front end, so bodes well for a more relaxed position, however the Canyons are known for having a higher front end than most manufacturers.

There are a host of factors to take into account when looking at geometry, but not easily described here...

Seat tube and top tube length are self evident, as to a degree is head tube length.

Seat tube angles will often dictate a bikes handling as much as the head angle, as it will dictate how your weight is distributed on the frame.

Your reach (distance from bars to saddle) and saddle lay back (distance saddle is behind the bottom bracket) should be fixed no matter what bike you ride, so all that changes with differing geometries is how far forward, or far back your weight is distributed on the frame.

posted by Jimmy Ray Will [269 posts]
15th April 2014 - 16:59

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Jimmy Ray Will wrote:
Head tube angle and wheel base has little influence on the position that you can attain on a bike, its much more about handling.

As mentioned, reach is really important, as is the height of the front end.

The synapse has been developed with a high, short (ish) front end, so bodes well for a more relaxed position, however the Canyons are known for having a higher front end than most manufacturers.

There are a host of factors to take into account when looking at geometry, but not easily described here...

Seat tube and top tube length are self evident, as to a degree is head tube length.

Seat tube angles will often dictate a bikes handling as much as the head angle, as it will dictate how your weight is distributed on the frame.

Your reach (distance from bars to saddle) and saddle lay back (distance saddle is behind the bottom bracket) should be fixed no matter what bike you ride, so all that changes with differing geometries is how far forward, or far back your weight is distributed on the frame.


Also worth mentioning that bottom-bracket drop has quite an effect on standover height and centre of mass... near-horizontal chainstays on some bikes mean the CoM is higher and the bike will feel less stable.

Boardman CX Team '14 | Cannondale CAAD8 '12 (written off, SMIDSY) | Scott Sportster '08

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posted by Gizmo_ [827 posts]
15th April 2014 - 17:32

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Stack and reach is only about how your body fits the bike e.g is your position comfortable.

Bike handling (how it feels; is it twitchy) is governed by other factors. Check out this site for an easily digestible explanation.

http://calfeedesign.com/tech-papers/geometry-of-bike-handling/

Even if the stack and reach are good for you, don't buy it without riding it first.

Good Luck

posted by wellcoordinated [76 posts]
15th April 2014 - 20:53

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I think you're wise to suggest trying both the Dales. However being 194cm the chances of my local dealers having my size, probably 63 or 61, is slim. I originally took note of all the stacks and reaches of all the bikes I was interested in but couldn't easily differentiate between the figures to arrive at a level of aggression. For example, aesthetically the canyon I think looks, and I've heard feels higher than other brands, but it's stack is similar to the SuperSix 398 and 396 respectively.

What really there me off, and bear with me here, is the BMC slr02 .Now reviews say this is plenty comfortable blah blah, but it's stack is 601cm , does that mean I am still looking at race geo and comfort is more reliant on the particular riders anatomy and flexibility?

I know many would suggest horses for courses, but I really want a bike that is able to put in the long miles keeping me comfortable, for sportive say, but that I can easily ride in a rode race and be competitive. I think it comes down to a poor fit on my current bike, which leads to believe my flexibility is also poor. (I haven't had a bike fit yet, so presumption only) so I really don't know what kind of geo I should be looking at, and being my height, test rides are tough.

Specialized Allez 2009, Campagnolo Centaur 10, Campagnolo Shamal Wheels. 8.3kg

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posted by Miles253 [199 posts]
15th April 2014 - 21:50

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I had worked out you were a tall lad.

After a lot of prevaricating I went for a Retul bike fit in December. Not only did I get my existing bike set up better, but the fitter gave me a recommended stack and reach for any new bike I was looking at. It changed my view on what would work for me. I learnt that my proportionally slightly longer back didn't suit the 'endurance' road bikes as well as I thought it might. Something like that may be worth a try.

I agree with the comments on stack and reach really being about fit, but fit is probably the most important aspect as riding a bike that fits you makes you happier to ride.

Ride more, ride better

posted by Sniffer [126 posts]
15th April 2014 - 23:09

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Have you considered a Ti bike for comfort? If you are thinking of keeping a bike for a few years then this should be you choice.

posted by wellcoordinated [76 posts]
15th April 2014 - 23:21

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wellcoordinated wrote:
Have you considered a Ti bike for comfort? If you are thinking of keeping a bike for a few years then this should be you choice.

Not really relevant with the OPs question.
More than just frame material to bring comfort as well, fit is equally if not more important.

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posted by glynr36 [370 posts]
15th April 2014 - 23:24

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I have not considered Ti actually but I don't appreciate the looks actually so I wouldn't buy one.

@sniffer
I have considered a retul fit actually, as well as specialized bg fit. Does retul encompass all fitting processes? Cleats an all? Did you find you needed long and low geometry to be comfy?

Specialized Allez 2009, Campagnolo Centaur 10, Campagnolo Shamal Wheels. 8.3kg

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posted by Miles253 [199 posts]
16th April 2014 - 0:43

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I think comfort on a bike is related to 3 things:
1. The compliance and vibration absorption of the bike
2. The match between frame and rider dimensions
3. The match between the preferences and capabilities of the rider and the characteristics and demands of the bike

Of these 2 and 3 are probably dominant. 1 is strongly influenced by tyre width, carbon bars, trick seatposts or even thickness of bar tape. When reviews suggest the Canyon is comfortable it is probably 1 that is being talked about and even then it's for a bike of its type i.e. A race bike. Frame material is not a consistent indicator of comfort here.
2 is about fit, mainly reach but lots of other things influence e.g. Saddle setback. If a frame is about the right size fine tuning of stem length, type of seatpost, crank length etc can improve things.
3 is about the rider's expectations and preferences and flexibility and strength. It seems to be often assumed that a more upright position is inherently more comfortable. If flexibility is a struggle and core strength not up to holding a low position for long periods then this may be true but if you want to race then trying to get low on an upright bike could well be equally uncomfortable.

I'd suggest you take it in reverse order. If you want all day comfort, are not as flexible or have the core strength you would like then a bike shaped like a Synapse is probably going to work better than one shaped like the Canyon. Once you know your preferences on shape then go to fit and only then what it's made from or what reviews say about how comfortable it is. Fat tyres and bar tape go a long way to addressing the last point anyway.
Have to come clean though, I didn't do this as well as I should have (being honest with yourself is important!)

posted by Nixster [73 posts]
16th April 2014 - 4:10

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Also good advice. As for being honest, well I know my flexibility isn't great, as I can't comfortable touch my toes immediately, I can if I've been at the gym, but not otherwise. I know what I want to look like, and what I want to ride. The inherent question is whether I can or not.

Any true tests of flexibility and core strength? That I can do off the bike?

Specialized Allez 2009, Campagnolo Centaur 10, Campagnolo Shamal Wheels. 8.3kg

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posted by Miles253 [199 posts]
16th April 2014 - 4:50

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Core strength - plank position. Can you hold it for a minute reasonably comfortably?
Flexibility - don't know but touching your toes comfortably probably a good start.

Watch out for your back though. Maintaining a flat back puts a load on lower and mid back muscles so strengthening these will also help but if you're achieving the flexibility by stressing your back rather than lengthening hamstrings and glutes then you'd better have Bupa!

Strength and flexibility can be improved of course but will need maintenance once you've got there, so it's also about how much work you want to have to do to keep on the bike you want to ride.

I should probably ride something like a Synapse or Scott CR1 but actually have a Supersix, which while I can maintain position while riding it I tend to pay afterwards. Great bike though. Working on flexibility and back strength religiously now!

posted by Nixster [73 posts]
16th April 2014 - 5:33

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Time to get to work on core and flexibility then, and perhaps consider something a touch less races! Nobody likes the idea of a SuperSix with loads of spacers!

Thanks for the help

Specialized Allez 2009, Campagnolo Centaur 10, Campagnolo Shamal Wheels. 8.3kg

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posted by Miles253 [199 posts]
16th April 2014 - 8:16

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@sniffer

I have considered a retul fit actually, as well as specialized bg fit. Does retul encompass all fitting processes? Cleats an all? Did you find you needed long and low geometry to be comfy?

There is a good review on this site about Retul. Look in Sam Shaw's blog. I went to the same place and my experience was very similar. My cleat position was checked and the fit seemed to be very comprehensive. There was also a flexibility and core strength test done (plank).

I did go longer from my fit. My stem length was increased to 120mm and my saddle was originally too high. This position does appear to be more comfortable.

Ride more, ride better

posted by Sniffer [126 posts]
16th April 2014 - 8:44

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