Zombie Cyclist

[If anyone has a suggestion for a better forum for this thread, I'd love to hear it.]

Going back and forth between my 1960 Bianchi Specialissima and my 2010 Surly Cross Check my first impression is how similar they ride, but with time, i've started to notice and wonder about some differences. One of the most dramatic is that when I move from the Surly to the Bianchi, the Bianchi feels "squirrelly", the steering seems less stable. Given their intended purposes, this makes sense, the Bianchi is a racing bike, the Surly is not, but I wondered what about them was responsible for the difference. I don't have any special tools for measuring frame dimensions and in particular do not feel like I can measure frame angles with adequate precision, but most of the distances I was able to measure seemed fairly similar. (For example, the "size" of both frames is 52 cm.) The one exception, one that would explain the difference in handling, is trail. (Trail is how far the contact point of the front wheel is behind the point where a straight extension of the head tube of the frame would touch the ground.) There has been a fair amount of discussion of the effect of trail on bicycle handling lately, especially in the Randonneuring community. Also, it seemed like it would be fairly easy to measure: simply put a yardstick with one end on the ground so that it lines up with stem-head tube-top of the fork and mark that point on the ground. Next, without moving the bike, mark the point where the front tire touches the ground. Measure the distance between them. If that measurement is in the 40s of millimeters, this is considered low trail, a characteristic of certain randonneuring bicycles, and if it is in the 50s or 60s it is considered medium trail, characteristic of most road bikes. I measured the Surly, which is considered a medium trail bike, and as expected came up with a measurement of 57 mm. I measured the Bianchi, and came up with 92 mm, which is a number larger than I have ever seen reported for any road bicycle. This sure would explain the difference in handling, but is so large I figure I must be doing something wrong. In case I am on completely the wrong track, I am throwing it out here for someone on this forum who knows about trail and/or old Bianchis who can quickly tell me either that this very long trail is a known characteristic of these bikes or alternatively that this is totally impossible.

THANKS!!

gaucho777 

Welcome to the forum! Firstly, it is extremely bad form to start a thread discussing a 1960 Bianchi Specialissima and not include any photos! We'd love to see your bike. Most people upload photos to a photo hosting site such as photobucket and then copy & past the "IMG" code directly into the thread text.

That said, your method of measurement is sound.

cyclotoine

Just make sure you are on a flat surface and your measurement tool for the contact patch is square and lining up with the center of the front axle and you should be good.

GrayJay

92mm is a lot of trail for a road bike, that would require either an unusually slack HTA and/or a fork with very little rake. I really dont think such a bike would have any redeeming handling qualities, it would just feel unpredictable. The wheel flop would be quite pronounced, hard to get a turn initiated and then it would flop and suddenly pull sharply further into the turn. You might consider adding more rake into the fork if you want it to achieve more neutral handling.

bradtx

ZC, Smaller sized bikes sometimes have slacker HT angles, sometimes more fork offset and sometimes a combination of both when compared to a larger bike of the same manufacturer and model (For tire/down tube clearance?). 52 cm is a grey area where either may or may not change from larger siblings.

I'd measure two places along the fork's straightest length and halve that for measuring rather than using just the head tube's center line.

Brad

repechage

Welcome. Two nice steeds.
Do keep in mind a few things, the decades apart the two bikes were built and the frame size.
52cm is small, no matter how you measure; center to top or center to center for the seat tube.
Small bikes have historically had compromised geometry up front and sometimes the seat tube angle too.
Often the head tube is slackened to achieve a reasonable top tube length and maintain a no toe overlap front center dimension.
Also, Bianchi of the early 60's was still built anticipating poor road conditions, strada blanche still being quite prolific in Italy back then.
In addition, older bikes for a given frame size had longer top tubes than what is convention today.

It would not surprise me if you could not set up the same position on the two bikes, the guidance has evolved.

I have a '53 Italian bike that is a 53 cm frame with a 55.5cm top tube, 72° parallel. I usually ride a 55-56 cm. The bike fits quite well by "modern" standards but if I was sized up for a bike way back I would have been placed on a larger frame with a shorter stem and less drop between the saddle and the bars no doubt. On unpaved roads this bike is quite a delight to ride. Aggressive descents are not its strong suit but it does feel stable, just not sporting.

Zombie Cyclist

Thanks for all the terrific suggestions everyone! I especially found the comments about the small frame size compelling, I will definitely follow up on that and post if I come up with anything.

To clarify, I do not find the handling of my Bianchi objectionable. One source suggests that racing geometries often feel "squirrelly" at low speed, a sensation that disappears as speed increases, and that has been my impression with the her. I certainly am not motivated to attempt to change either the geometry or the handling, I love my Bianchi the way she is.

I apologize for not including a picture, I had not yet figured out photos on this forum* nor was I happy with the photos of my Bianchi that I had and was waiting until I had taken better ones. The attached photo is one of the ones I had and thus is far from perfect but is nice because it shows my Bianchi in near original configuration. I hope this photo will do until I have better ones.

* One of you suggested that I host photos on another site and include links. I hope I am not being rude by uploading this photo directly to the forum. I am trying to do figure out if I can link to photos hosted on Google+ (I have a family connection with Google) and haven't made that work yet. If that turns out to be impossible (which it well may), I will create an account on one of the sites that does work and post future photos that way.

bradtx

ZC, I generally just attach a photo like you did, no big deal.

Brad

iab

Likely only the latter. The 3 bikes below are from 1933, 1958ish and 2009 respectively. All "race" bikes". As you see, the 2009 had the most trail.

For the OP, when taking a picture for this purpose, place your bike as upright on a flat surface against a wall. Use 100% optical zoom on your camera to get it the furthest you can from your bike while filling the frame with your bike. The camera lens should be about the same height as the top of your rims. This will minimize distortion.

Geometry2 by iabisdb, on Flickr

repechage

Actually, the image tells the tale pretty well, you will most likely find the seat tube angle to be 72° or 73°. Most Italian road bikes at the time were 72°. Look at the head tube angle in comparison, much slacker. What you have is the typical solution for obtaining a short top tube (to be in proportion to the seat tube) and the typical generous fork rake of the larger sizes being maintained in the wee ones. At low speed you probably have a lot of "wheel flop" which is the feeling one gets of the drop and rise of the head tube as you turn the front wheel, mostly felt as slow speed as that is the time you are most likely to make big swings of the steering.

Brian Baylis would say this bike would handle like a truck. To experience a comparison you would need to find a bike with a 73° head angle, fork rake of 50mm or less and live with front wheel overlap or a too long of a top tube. Many builders would like to design the frame so that you would need a 100 or 110 mm stem, to do so and get you comfortable would result in a lot of overlap and or 650c wheels. Part of the problem are the UCI regulations for road bicycles. Overlap was basically regulated out. Designing a production bike where overlap was part of the design was even back then not an insurance friendly thing to do. in a bespoke one off bike, it might be okay if the client is willing to have the condition.

Way back I had a bike like that. Terrific handling machine, perfect for its purpose that I asked of it which was to be ahead of the others in criterium races, that bike had a 37.25" wheelbase, super tight rear triangle, 11 inch high bottom bracket and lots of overlap. I learned to manage the bike a slow speed. But its reason for life was going fast around corners and sprinting to victory.