Giant Defy 3 (2010) vs Trek Domane AL2

[531colin]

We were, at one stage, trying to compare the steering geometry of 2 bikes. I think the Trek is fairly well documented, i accepted that my misgivings about their trail figure were unfounded.
Giant, in the link above, don't give either trail or fork offset. If we assume the offset is 45mm, using Brucey's table the trail values come out.....
XS...69
S..63
M, M/L, L, & EXL...60
Not very different to the Trek.
So it seems to me that the 2 manufacturers have used slightly different ways to arrive at broadly similar steering characteristics.....hardly surprising as they are broadly similar types of bike.
So, again, Big Bird, if you are still out there, get a test ride.
We have had several contributors to this thread who say the bike they bought has good handling. All this means is that the handling suits them, it doesn't mean it would suit either me or you.

[Paulatic]

We were, at one stage, trying to compare the steering geometry of 2 bikes. I think the Trek is fairly well documented, i accepted that my misgivings about their trail figure were unfounded.
Giant, in the link above, don't give either trail or fork offset. If we assume the offset is 45mm, using Brucey's table the trail values come out.....
XS...69
S..63
M, M/L, L, & EXL...60
Not very different to the Trek.
So it seems to me that the 2 manufacturers have used slightly different ways to arrive at broadly similar steering characteristics.....hardly surprising as they are broadly similar types of bike.
So, again, Big Bird, if you are still out there, get a test ride.
We have had several contributors to this thread who say the bike they bought has good handling. All this means is that the handling suits them, it doesn't mean it would suit either me or you.

It's been fascinating watching you and Bruce number crunching.Sadly I can never seem to get my head fully around them and I've been lost along the way.
I too thought both bikes were designed to deliver a similar ride.
In your first response to the OP you said

Head angle.....combined with a 45mm offset, 73 degrees will see me in the ditch PDQ. 72 degrees is Ok, but I prefer 71.5 deg. (Yup, small differences)

Am I right in thinking that those characteristics you refer to are only, roughly, true if the offset is 45 mm?
So, with the two bikes with different head angles, am I right in thinking it is the trail which is perhaps important?

[Brucey]

I think it is probably fair to say that two bikes with slightly different head angles, but the same trail, are going to steer more similarly than two bikes with the same head angle, but a different trail value (and of course fork offset to achieve it).

cheers

[531colin]

As a specie, we are always looking for "one number" to compare 2 different things.
If we are looking to compare the steering of 2 different bikes then that "one number" is trail.**
My initial assumption that I could compare the 2 bikes based on head angle is only sound if the other variables (offset, wheel size) are the same.

Well, more or less. You can add in tyre drag, and presence/absence of a front load before you get to the contentious stuff like any effect of wheel size (apart from its effect on trail) and whether the same trail achieved by different variations of offset and angle handles exactly the same.....I'm happy with Brucey's "more similar than...." approach.

[Big-Bird]

Thank you all for your replies and input. Having looked at so many different figures and spec sheets to the point of total confusion I decided to instead to look at it from a viewpoint of what single thing was it that made me feel uneasy on riding the Giant. After thinking about every aspect I realised for me personally it was probably more to do with tire width than anything else. Having worked that out I took a gamble on the Jarmis Renegade Exile and although not strictly a roadie it is perfect for the type of cycling I enjoy. Only picked it up today and had a quick 12mile ride but initial findings are it's very comfortable, quick enough for an out-of-shape 40+ year old to still feel like I am getting a move on, grip (although not tested properly) seems to be plentiful with the clement tires and gearing appears to be just right for my needs. Best part for me though is I managed to get several personal best sector times on the ride today which I was taking it fairly easy on being a new bike

[531colin]

............ I am looking for a less race inspired road bike.........

..................
So, now for the numbers........
Fork offset or rake is almost always 45mm, thats sort of the "racing standard" that eg. carbon forks tend to be made to.
Head angle.....combined with a 45mm offset, 73 degrees will see me in the ditch PDQ. 72 degrees is Ok, but I prefer 71.5 deg. (Yup, small differences)................
You might find "cross" or "gravel" or many other strange "types" of bike have more forgiving handling.
Happy hunting!

Look at the geo. table here........http://www.jamisbikes.com/usa/renegadeexile.html