Alterning steering behaviour

Not sure if this one needs to go to rec.bicycles.tech, but I'll try the UK
first....

My partner rides an Orbit Mercury with flat bars (a tiny road bike with 26in
MTB wheels). The steering is somewhat twitchy, and she would prefer it to
be a bit slower steering and thus more stable.

The Mercury has a traditional steering stem with locknuts and expander bolt.
Her bike has a very short reach stem, originally intended for drop-bars. The
handlebars are straight (MTB), with the grips/brakes/shifters set well
inward of the original bar width.

So, what changes will give an improvement in steering and how to fit it ?

I can think of the following:
Different tyres - does this make any difference ? Currently using
Specialized Fat-Boy slicks.
Different stem, taller and longer reach, possibly combined with different
bars - might make a slight change to the feel of the steering, but doesn't
alter the geometry. Would it make much difference ?
Replacement forks, either longer (decreases the steering angle, which should
increase trail) or with a different trail.
Altering the existing forks to increase the trail, either by bending the
forks or moving the drop out position.
Stacking the head bearings to increase the effective fork length. Probably
not enough fork steerer to reach the top-nut to do this.

I guess this will need a trip up to Madgetts in Diss, but advice in advance
would be useful.

Nigel

NC wrote:

Not sure if this one needs to go to rec.bicycles.tech, but I'll try the UK
first....

My partner rides an Orbit Mercury with flat bars (a tiny road bike with 26in
MTB wheels). The steering is somewhat twitchy, and she would prefer it to
be a bit slower steering and thus more stable.

The Mercury has a traditional steering stem with locknuts and expander bolt.
Her bike has a very short reach stem, originally intended for drop-bars. The
handlebars are straight (MTB), with the grips/brakes/shifters set well
inward of the original bar width.

So, what changes will give an improvement in steering and how to fit it ?

I can think of the following:
Different tyres - does this make any difference ? Currently using
Specialized Fat-Boy slicks.
Different stem, taller and longer reach, possibly combined with different
bars - might make a slight change to the feel of the steering, but doesn't
alter the geometry. Would it make much difference ?
Replacement forks, either longer (decreases the steering angle, which should
increase trail) or with a different trail.
Altering the existing forks to increase the trail, either by bending the
forks or moving the drop out position.
Stacking the head bearings to increase the effective fork length. Probably
not enough fork steerer to reach the top-nut to do this.

New (straight) forks might help, but you then have to watch for toes
fouling the front wheel or mudguard. 26" wheels are a good way to
design a small frame, but if it's really "tiny" then there could still
be compromises in the design.

"Pete Biggs" wrote in message
...
NC wrote:
Not sure if this one needs to go to rec.bicycles.tech

It's a good one for them so you should post there as well.

My partner rides an Orbit Mercury with flat bars (a tiny road bike
with 26in MTB wheels). The steering is somewhat twitchy, and she
would prefer it to be a bit slower steering and thus more stable.

How long has she had it and how many miles done?

Several years and at least 1000 miles.
45 mile ride on Friday last week.


So, what changes will give an improvement in steering and how to fit
it ?

Different stem, taller and longer reach

Longer reach will make the steering slower but that's not worth doing if
it would make the riding position uncomfortable. It would need to be more
than 15mm longer to make a significant difference to steering, possibly a
lot more.

Could work if the stem was higher as well. I'll look at this option.
I'll need to replace cables (not enough length to move them much further at
the moment).



Replacement forks, either longer (decreases the steering angle, which
should increase trail) or with a different trail.

Different forks could make a big difference. LESS offset or rake will
make the bike more stable. See: http://www.phred.org/~josh/bike/trail.html

I've read that before. Perhaps I should go and calculate the trail for the
bikes in the shed and make some comparisons.

. But there's a danger of the steering feeling very weird with a different
rake (plus or minus).

Longer? No!

Altering the existing forks to increase the trail

, either by bending the forks or moving the drop out position.

No no!!!! Will mess up steering and will be dangerous if you got that
even slightly wrong,

Sorry, not clear. I had in mind re-building the existing forks by a frame
maker, not hitting them with my own hammer ! To my mind, that's very similar
to new forks.



I think it's all either a case of more practice and setting required or
bike is wrong size & shape for your partner. The steering of the bike is
likely to be ok for a rider of the right size - but perhaps not everyone
will happen to like the "feel" of this particular bike.

Size is an issue; at the time we bought it, there were not many bikes suited
to 5ft riders, this has a 42cm frame and took more than a year to find. The
number of small bikes around has improved a bit, but we're loathed to spend
another £500+ on another bike. The steering is quick and a bit twitchy - I
can feel it (though I look comical riding it) - slightly slower might be
better.


Nigel.

NC wrote:


Size is an issue; at the time we bought it, there were not many bikes suited
to 5ft riders, this has a 42cm frame and took more than a year to find. The
number of small bikes around has improved a bit, but we're loathed to spend
another £500+ on another bike. The steering is quick and a bit twitchy - I
can feel it (though I look comical riding it) - slightly slower might be
better.


I thought the steering on the giant ocr was a bit twitchy after an older
claude butler but after two days of commute it felt normal to me.


Ivor Cave

NC wrote:
Different stem, taller and longer reach

Longer reach will make the steering slower but that's not worth
doing if it would make the riding position uncomfortable. It would
need to be more than 15mm longer to make a significant difference to
steering, possibly a lot more.

Could work if the stem was higher as well.

Generally longer stems need to be lower. It's the short stubby ones that
are usually put up high.

Altering the existing forks to increase the trail

, either by bending the forks or moving the drop out position.

No no!!!! Will mess up steering and will be dangerous if you got
that even slightly wrong,

Sorry, not clear. I had in mind re-building the existing forks by a
frame maker, not hitting them with my own hammer ! To my mind, that's
very similar to new forks.

Ok, but there's still a risk of them ending up asymetrical and new forks
are likely to be cheaper than getting the work done. See St John Street
Cycles for examples.

~PB