Cycling UK Forum

It’s about 10 minutes work to measure the offset, then we might know.
But where’s the fun in that?

Cyclothesist wrote: ↑28 Dec 2024, 10:57pm I don't think anyone can have a definitive diagnosis from the description given. The OP appears stumped and out of their depth. That bike needs a trip to a good bike mechanic.

I think the OP is saying the handling has changed; and that’s with the old headset and a replacement headset. So presumably it’s not a mechanical issue with the headset, so what’s left?
Bent fork?
Fork coming apart at the crown?…you might hope somebody would have noticed! New headset fitted by a shop, I think.
Bent frame or frame welding failure is probably less likely ?

531colin wrote: ↑28 Dec 2024, 6:32pm Check fork offset.

To do this
1. Remove front wheel and mudguard.
2. Measure BB axle to front axle with steering “dead ahead”
3. Reverse fork and re- measure front axle to BB axle
4. Fork offset is half the difference between your 2 measurements, to a good approximation.

I think design offset is 54mm, but you can check that on SPAs website.

Just to be clear, I think what’s going on is this;
Repeated impacts have bent the fork to increase offset and reduce trail ; you now have a low trail bike with tricky handling

Check fork offset.

To do this
1. Remove front wheel and mudguard.
2. Measure BB axle to front axle with steering “dead ahead”
3. Reverse fork and re- measure front axle to BB axle
4. Fork offset is half the difference between your 2 measurements, to a good approximation.

I think design offset is 54mm, but you can check that on SPAs website.

Sweep wrote: ↑27 Dec 2024, 7:44pm ……I pretty religiously check train wear with a tool (yes I know you are supposed to use a steel rule and a set of log tables but I'm not up to it) and often find that while the vast vast majority of the chain is fine and dandy any measurement taken across a span of chain including the link is not.

Being a mean git I am tempted to keep using the chain but usually give in and replace it.

Because of this "rogue" measurement.
…………

If one link is worn on a chain of over 100 links, this won’t have much effect on sprocket wear, because it’s only that pair of rollers which are at a wrong spacing, all the rest are OK. Each time the chain goes round, just one tooth on the sprocket and one tooth on the chainring can be exposed to the wrongly spaced rollers.

Bmblbzzz wrote: ↑27 Dec 2024, 1:27pm Or is counter-steering what happens after you lean? In other words, you lean left (to turn left) and as you do so, the front wheel, whether through momentum or gyroscopic forces or what I'm not sure exactly, carries on straight, thus creating counter-steer. The counter-steer is the product of the lean, it does not produce the lean.

At least so I've understood it, but I'm not sure I've noticed it in reality.

Try Andrew's test, previous page?

Some people claim that they ride with their hands so lightly on the bars that when they lean the bike (by shifting body weight) the weight of the front wheel working through the lever of fork offset (?) is enough to turn the steering on the headset bearing. I have been struggling to believe this, so........

I went out to the shed and leant a (stationary) bike. I tried stopping the front wheel turning by the pressure of one digit on the handlebar.....the "pressure" was only just enough for me to feel it. When actually moving, the wheel is turning so there will be less friction between tyre and surface, so to turn (or straighten) the steering will require the exertion of even less force?

Riding no hands, the steering is turned by leaning the bike.....there isn't much option, that has to be it.

Riding no hands, I think the turn is initiated by leaning into the turn; I don't think there is anything like counter-steering going on.
(riding no hands if you wanted to turn left by counter-steering, you would have first to initiate a right turn to lean the bike left in order to turn left; however this becomes a circular arguement, because in order to initiate a right turn (to lean the bike left) you would need to first initiate a left turn to lean the bike right....and so ad infinitum.)

andrew_s wrote: ↑23 Dec 2024, 6:30pm

pjclinch wrote: ↑22 Dec 2024, 4:50pm

531colin wrote: ↑22 Dec 2024, 10:33am Initiating a turn on a motorbike, which is heavier than me, with or without a pillion passenger, I can "initiate a turn" by "countersteering", which means (briefly!) steering left to lean the bike to the right in order to make a right turn. I'm not aware of doing this on a push bike, or a pedelec.

Counter-steering can be found in Cyclecraft, introduced as an advanced technique for things like slaloming around potholes. I use it coaching as a demonstrator on how bike steering isn't like trike steering but I don't actively, consciously do it in my general riding.

Pete.

Not being conscious of counter-steering doesn't mean that it's not a normal part of bike control that you do sub-consciously all the time.

To demonstrate, try riding with your hands making fists resting on the rear side of the bar, so you can only push on the bars, not pull, and you'll find that you ride entirely normally.
Then try turning left into a side road with one hand off the bars. What you'll find is that you can make the turn quite easily with your left hand on the bars, but that if you try to use the right fist while signalling left, you'll have to unclench your fist so you can pull on the bars.

I dare say most people do much the same quite a lot, just resting the heel of the hand on the tops with the fingers just dangling loosely in front of the bars. I certainly do.

WHAT A WONDERFUL DEMONSTRATION!
20 years ago I would have been straight out and tried it.....unfortunately, I am now of an age (77) where people trip over their slippers, fall over and break bones, so I shall choose my moment to try it!

When I'm freewheeling, or just idling along, I have just enough weight on the bars so that I can "steer" (as much as i need to, which doesn't normally involve waving the bars through great sweeping arcs) WITHOUT curling my fingers around the bars. In order to completely un-weight the bars (for example to raise my hands above the bars) I have to support that tiny bit of weight with my "core" and when I do I feel a slight change somewhere in my back or abdomen.
(edited for clarity)

CyberKnight wrote: ↑26 Dec 2024, 9:49pm on further research i found an article on someone who looked into into it
upshot
say you had drop bars and went from 100 to a 50 mm stem then to turn the bars 20 degrees you would turn 1 cm less

And 20 degrees of turn is in the "low speed manoeuvering" range, not the "riding along" range.

Where do you (normally) hold the existing bars? It looks like the bars bring the grips (where the brake levers are) back in line with the head tube, this is completely outside my experience.

foot level on bottom pedal by 531colin, on Flickr

https://www.cinelli-milano.com/products ... ......this?
The geometry table is pretty impenetrable; I think it says (for the 54cm) head angle 71.5 offset 47.
.....don't you want short trail for a front load?
Seat tube angle is 74 degrees, completely impossible for me.

.................what are you looking for?

Slowroad; I don't have a really clear picture of whats going on.......

Touriste....flat bars....toe overlap.....shoulder issues....propping up torso on arms ??
Mercian....smaller.....unknown bars .....shoulder issues......propping up torso on arms ??

This probably sounds wrong, but the way to take the weight off your arms is to move the saddle back.
Put a bit of tape on the saddle rail as the saddle is now, so that you can get the saddle back exactly where it is if you need to.

017 by 531colin, on Flickr

With the current saddle position clearly marked, move the saddle back and see if you can take the weight off your arms.

I like to be able to do this ;

Balanced position by 531colin, on Flickr

Not everybody is comfortable doing that while riding no hands. An alternative is to find a road which rises gently, and ride up it, starting gently and gradually increasing your effort. I can feel the weight come off my hands with just a bit of pedalling effort; if I'm working fairly hard, I'm pulling up on the bars even when I'm sitting on the saddle.

Clearly, moving the saddle back will increase reach to the bars, and you probably aren't looking for an increased reach. However, I would recommend you try to sort out your riding position using your existing bike(s). Buying a new bike and then finding out the new bike hasn't solved your fit issues is expensive and futile. You may get sorted out by moving the saddle back and fitting a shorter stem.

tentman wrote: ↑23 Dec 2024, 10:11am What a wonderful word! Does 'detransitioned' mean 'changed it back'?

IT DOES NOW!

Ha Ha!.....the Master has posted.....but I'll post this anyway......

Audax67 wrote: ↑22 Dec 2024, 8:18am My old Ti-framed bike used to shimmy if I had a rack pack aboard, or if I was gripping the bars too tightly and keeping my arms stiff. A handlebar bag changed its resonance frequency and the shimmy stopped completely.

I think this illustrates how difficult it is to forecast whether or not any particular design of bicycle will shimmy....some will shimmy as soon as you fit a bar bag.

I remember long ago Brucey posting to the effect that "Any bike built light enough to be comfortable unloaded will shimmy at some combination of speed, loading and other variables."

At the time I was responsible for designing the Spa bikes, and this panicked me considerably. I found a local hill which was steep and long enough to get up a good speed freewheeling, with good sight lines and road surface so I could freewheel down no hands in safety. ...which I did, multiple times on multiple bikes, including doing things like banging the corner of the drop bar forward with the heel of my hand, in attempts to provoke a shimmy. Nothing, zip, zilch.....try as I might.

It now occurs to me that by "comfortable unloaded" Brucey possibly meant lightweight steel tubes, inch top tube, inch and eighth down and seat tubes, inch steel steerer. ....at which point 2 things occur to me.....firstly, a six foot sixteen stone man on those tubes would have a very different riding experience to a five foot eight stone woman.....and secondly, by the time I was designing the Spa bikes, the world had changed to inch and eighth steel steerers and "oversize" tubes.

First good bike I had was about 1965, butted 531. Maybe 20 years later, it started shimmying with my hands on the bars...I was devastated, then I found I could kill the shimmy by sliding back in the saddle a bit; so I put the saddle back a bit, and rode it for several more years.

axel_knutt wrote: ↑22 Dec 2024, 1:30pm When I reduced the stem length (as above) it was the only change to the bike, and it went from having done 40,000 miles all over the country and down some of the biggest hills without ever having shimmied once, to shimmying the first time I went down a modest local hill that I'd been down scores of times before. Shortening the stem reduces the moment of inertia of the steering, and so will shortening the bars, but to a lesser extent.

If your hands are forward of the steering axis, any weight you place on them will provide a self-centering force for the steering, and if your hands are closer to the axis the self-centering effect is less, and the steering feels more twitchy.

How big a change in stem length?