Resizing components

Colin Blackburn said:

My other half's bike is the right size for her, well the frame is
anyway. But, we'd like to tinker with a few components to play with
the reach and the front wheel overlap/pedalling efficiency.

Elfie uses Butterfly bars which, depending on the angle they are set
at, bring the straight part of the bars towards the rider. The bike
was originally fitted with a ridiculously short stem and standard
70mm cranks which meant that knees could come into contact with bars!
I changed the stem to a 110mm (with a 30-40 degree upward angle IIRC)
some time ago.

However, she would like a slightly longer reach to the bars, she
feels too upright at the moment, so I'm thinking of a 130mm stem. Is
there a trade off with the handling as the stem length is increased?

Yes, a longer stem will make the steering "slower" and handling will feel
different when out of the saddle, but 130mm is not beyond the normal
range. You generally very quickly get used to any difference in handling
so that shouldn't be a problem, with a bit of luck.

Quoted message said:

I have seen a few at 150mm advertised, though this would be too much.

Yes too much of a change to try in one go, I think. Even 10mm makes a
difference. 120mm might be enough if only a *slight* change really is
required.

Quoted message said:

Also, her inside leg is short and so 170mm cranks are probably not the
most efficient. Something around 160mm would seem, on paper, to be
more suitable. This would also remove the slight toe overlap with the
front mudguard. Can anyone recommend a good supplier for non-standard
cranks?

165mm Shimano cranks are commonly available.

Settle Cycles and St John Street Cycles have some 160 and shorter cranks.

Toe overlap shouldn't matter as long as it only occurs at very low speed
and very tight turns. It's then avoided easily by freewheeling or
half-pedalling.

Quoted message said:

Will I need to replace the entire chainset or can I just
replace the spiders? (The only words I found on the chainset with a
very brief look this morning was 'Cyclone'😉

I don't know Cylones. Regarding chainring compatibility, make a note of
the number of arms/bolt holes and the Bolt Circle Diameter (aka Pitch
Circle Diameter). See www.sheldonbrown.com/gloss_bo-z.html

Quoted message said:

If I change the chainset
should I adjust the chainrings to account for the short crank---she
likes her bottom gear so I'd not want to make things harder.

There won't be a huge change in gearing but still not a bad idea to change
either the rings or the rear sprockets for that reason if you like. Have
a go with Sheldon's gear calculator, using Gain Ratio units, to work out
what would be required:
http://www.sheldonbrown.com/gears

Settle Cycles are good for replacement rings.

Funny, I was just doing some sums yesterday as I might be changing from
175 to 172.5mm. Turns out that equates to less than one rear sprocket
tooth's worth of difference (with my gears).

~PB

Pete Biggs said:

Colin Blackburn said:

My other half's bike is the right size for her, well the frame is
anyway. But, we'd like to tinker with a few components to play with
the reach and the front wheel overlap/pedalling efficiency.

Elfie uses Butterfly bars which, depending on the angle they are set
at, bring the straight part of the bars towards the rider. The bike
was originally fitted with a ridiculously short stem and standard
70mm cranks which meant that knees could come into contact with bars!
I changed the stem to a 110mm (with a 30-40 degree upward angle IIRC)
some time ago.

However, she would like a slightly longer reach to the bars, she
feels too upright at the moment, so I'm thinking of a 130mm stem. Is
there a trade off with the handling as the stem length is increased?

Yes, a longer stem will make the steering "slower" and handling will feel
different when out of the saddle, but 130mm is not beyond the normal
range. You generally very quickly get used to any difference in handling
so that shouldn't be a problem, with a bit of luck.

Quoted message said:

I have seen a few at 150mm advertised, though this would be too much.

Yes too much of a change to try in one go, I think. Even 10mm makes a
difference. 120mm might be enough if only a *slight* change really is
required.

Quoted message said:

Also, her inside leg is short and so 170mm cranks are probably not the
most efficient. Something around 160mm would seem, on paper, to be
more suitable. This would also remove the slight toe overlap with the
front mudguard. Can anyone recommend a good supplier for non-standard
cranks?

165mm Shimano cranks are commonly available.

Settle Cycles and St John Street Cycles have some 160 and shorter cranks.

Toe overlap shouldn't matter as long as it only occurs at very low speed
and very tight turns. It's then avoided easily by freewheeling or
half-pedalling.

Quoted message said:

Will I need to replace the entire chainset or can I just
replace the spiders? (The only words I found on the chainset with a
very brief look this morning was 'Cyclone'😉

From what I have seen there are three ways to go.

The cheap way is to buy an integrated chainset of about the right length, ie
with the rings riveted to the crank. These are hard to find and not as cheap
as their quality would suggest (though SJScycles.com usually have a
selection).

The next method is to find a better quality chainset that comes in the right
length. Typically these are the top of the range ones, eg shimano Ultegra go
from 162.5 (IIRC) upwards.

Best but most expensive is to take the new TA Vega modular route.
Chainrings, spider and cranks are sold separately so you can mix and match.
Cranks come in almost any length imaginable. Spiders attach to the cranks
and are available for many different chainring sizes. Then just add
chainrings to suit. Expect to pay upwards of 150 quid for a complete set.
The advantage of this is that you can get a spider to match existing
chainrings, or if you need to change crank lengths you can do so easily
without having to change the whole chainset. Probably a really good idea
for a youth race bike as you can move the cranks with the change in bike and
not have to shell out huge amounts of money to get a complete chainset.

Not sure if this method allows you to add the spider to either the left or
right hand crank for use as a crossover set on a tandem.

FWIW I have an Ultegra 165mm double on the road bike (though would like a
triple.. the upgrade will cost me about 100+ pounds minimum for the same
quality. With Vega it would have cost me about 40 quid for the spider and
another tenner or so for the little ring.
I also have a 162.5 chainset on the MTB which is possibly a trifle short. I
couldn't find a cheap 165mm one at the time and it replaced a 175mm one.

...d

Perhaps you could contact someone like Highpath who can cut down the long
cranks

"Colin Blackburn" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

My other half's bike is the right size for her, well the frame is anyway.
But, we'd like to tinker with a few components to play with the reach and
the front wheel overlap/pedalling efficiency.

Elfie uses Butterfly bars which, depending on the angle they are set at,
bring the straight part of the bars towards the rider. The bike was
originally fitted with a ridiculously short stem and standard 70mm cranks
which meant that knees could come into contact with bars! I changed the
stem to a 110mm (with a 30-40 degree upward angle IIRC) some time ago.

However, she would like a slightly longer reach to the bars, she feels too
upright at the moment, so I'm thinking of a 130mm stem. Is there a trade
off with the handling as the stem length is increased? I have seen a few
at 150mm advertised, though this would be too much.

Also, her inside leg is short and so 170mm cranks are probably not the
most efficient. Something around 160mm would seem, on paper, to be more
suitable. This would also remove the slight toe overlap with the front
mudguard. Can anyone recommend a good supplier for non-standard cranks?
Will I need to replace the entire chainset or can I just replace the
spiders? (The only words I found on the chainset with a very brief look
this morning was 'Cyclone'😉 If I change the chainset should I adjust the
chainrings to account for the short crank---she likes her bottom gear so
I'd not want to make things harder.

Any advice, etc...

Colin

In message <[email hidden]>, Pete Biggs
<[email hidden]> writes

Quoted message said:

Colin Blackburn said:

My other half's bike is the right size for her, well the frame is
anyway. But, we'd like to tinker with a few components to play with
the reach and the front wheel overlap/pedalling efficiency.

Quoted message said:

Quoted message said:

Also, her inside leg is short and so 170mm cranks are probably not the
most efficient. Something around 160mm would seem, on paper, to be
more suitable. This would also remove the slight toe overlap with the
front mudguard. Can anyone recommend a good supplier for non-standard
cranks?

165mm Shimano cranks are commonly available.

Settle Cycles and St John Street Cycles have some 160 and shorter cranks.

Spa Cycles are also useful, esp for TA and Stonglight

Quoted message said:

--
Chris French, Leeds