Small Bikes - Handling

DaveH said:

I am about to buy a road bike for my wife. She will need a
bike in a frame size about 52cm. However I note that
manufacturers now seem to be using one fork rake for all
their bike sizes, with head angles varying from 71 to 74
degrees, eg Giant (XS - 71 deg and 45mm rake), Fuji (52cm,
72 deg and 43mm rake) Colnago (52cm 71deg and 43mm). This
leads to high trail figures of 65mm to 69mm. The ideal
trail is (apparently) around 56mm.

Quoted message said:

Such trail must really negatively affect the handling
of these bikes, making it slow and with a self
centering action.

Doesn't the Giant use 650c wheels on the XS size? That would
reduce trail a bit compared to a 700c wheel.

Obviously toe overlap is an issue with small frames. But I
don't see why they wouldn't use more offset (aka "rake"😉 to
bring the trail number into line when using slack head
angles. More offset would also improve toe clearance.

Art Harris

DaveH said:

I am about to buy a road bike for my wife. She will need a
bike in a frame size about 52cm. However I note that
manufacturers now seem to be using one fork rake for all
their bike sizes, with head angles varying from 71 to 74
degrees, eg Giant (XS - 71 deg and 45mm rake), Fuji (52cm,
72 deg and 43mm rake) Colnago (52cm 71deg and 43mm). This
leads to high trail figures of 65mm to 69mm. The ideal
trail is (apparently) around 56mm.

Such trail must really negatively affect the handling
of these bikes, making it slow and with a self
centering action.

There must be riders out there who are using these bikes.
How do you find the handling? What are you thoughts?

Mine - Colnago so-called 54 cm frame (actually 52,5 cm from
centre of bottom bracket to top of top tube, so this
particular frame might be good fit for your wife but I'm
going to ride this one until I break it ;-). Geometry is 74
deg seat tube, 71,5 deg head tube. Fork blades are straight
but are angled from the steerer to cause effective rake.

I find the handling very stable, almost lazy in feel. By
this, I mean the *opposite* of nervous or twitchy. Very
nice bike for long distance competitions or credit card
touring. Relaxing.

I have had quite twitchy frames in earlier years (e.g. a
custom 73,5 deg seat and 73,5 head, with short-rake forks,
or an Alan 75 deg seat and 74 head, similar short forks).
Both were much fun in the crits I rode but slightly
irritating on longer rides (always spent some energy making
sure I rode in a straight line, for some reason).

Unfortunately I cannot help you on the evaluation of trail -
I have not yet read up on it to understand the correlation
with handling characteristics.

/Robert

"DaveH" <[email hidden]> wrote in message
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Quoted message said:

I am about to buy a road bike for my wife. She will need a
bike in a frame size about 52cm. However I note that
manufacturers now seem to be using one fork rake for all
their bike sizes, with head angles varying from 71 to 74
degrees, eg Giant (XS - 71 deg and 45mm rake), Fuji (52cm,
72 deg and 43mm rake) Colnago (52cm 71deg and 43mm). This
leads to high trail figures of 65mm to 69mm. The ideal
trail is (apparently) around 56mm.

Such trail must really negatively affect the handling
of these bikes, making it slow and with a self
centering action.

If I calculate it correctly, the Bianchi Brava 52cm, with
fork rake of 50mm and head angle of 72 degrees, has a
trail of 61. Still a bit high, but better than on the
bikes you note.

The way to reduce this is to go to 650mm wheels, but these
are only used on very small frames.

The problem is that the manufacturers don't want to make a
bunch of different forks.