Electric gear shifting?

[Postboxer]

I was wondering the other day about how much the temperature changes the length of the cable, it must make some, and only a small difference could cause problems. I suppose you need to set them up when the temperature is in the centre of the possible range it will encounter.

[Bicycler]

... none of them use a power source other than the human in the saddle. That to me is an important distinction. It’s my ‘red line’.

I'm just wondering what equipment you use to do the liposuction in order to get a fuel source to burn in your bike lights?

Dynamo?

[andrewjoseph]

No idea but the front is grinding a bit and the rear won't shift into some gears. I'm sure it just needs a tweak tbh

so the mechs may not be out of alignment.

when is front mech grinding, on trying to change up to big cog?

what gears are difficult to use, largest cogs in back or smallest??

[Mark1978]

No idea but the front is grinding a bit and the rear won't shift into some gears. I'm sure it just needs a tweak tbh

so the mechs may not be out of alignment.

when is front mech grinding, on trying to change up to big cog?

what gears are difficult to use, largest cogs in back or smallest??

On the front the chain is rubbing on the right hand side of the front mech, especially when I'm in the hardest gears on the back. I can tell mostly because if I push the shift lever more then the noise stops, of course comes back when I let go.

On the rear, it appears to be the lower half of the cassette some gears just don't want to engage properly, constantly clicking, sometimes if I shift past and then back it, then it will engage.

As I said I'm sure it just needs reindexing front and back, but I've never had any luck with that. Of more concern is why it's going out in the first place, as the front was doing the exact same thing maybe 3-4 months ago and the LBS fixed it up.

[reohn2]

No idea but the front is grinding a bit and the rear won't shift into some gears. I'm sure it just needs a tweak tbh

so the mechs may not be out of alignment.

when is front mech grinding, on trying to change up to big cog?

what gears are difficult to use, largest cogs in back or smallest??

On the front the chain is rubbing on the right hand side of the front mech, especially when I'm in the hardest gears on the back. I can tell mostly because if I push the shift lever more then the noise stops, of course comes back when I let go.

On the rear, it appears to be the lower half of the cassette some gears just don't want to engage properly, constantly clicking, sometimes if I shift past and then back it, then it will engage.

As I said I'm sure it just needs reindexing front and back, but I've never had any luck with that. Of more concern is why it's going out in the first place, as the front was doing the exact same thing maybe 3-4 months ago and the LBS fixed it up.

The front mech sounds like it needs the cable tightening slightly so the mech is up again the upper limit screw.
The rear sounds like a sticky cable and I'd go for the short piece of outer at the rear mech,which needs unhitching from the stop on the chainstay by putting the bike in bottom gear then withouut turning the pedals shift to the highest gear(small cog)this allows enough slack in the outer cable to unhitch it from the the chainstay stop,it can then be slid along the inner and the portion of now exposed inner cleaned and lubed with grease,then reassembled .

[[XAP]Bob]

I was wondering the other day about how much the temperature changes the length of the cable, it must make some, and only a small difference could cause problems. I suppose you need to set them up when the temperature is in the centre of the possible range it will encounter.

Only if the inner and outer have different coefficients of thermal expansion...

[Brucey]

yes, and for our purposes the 'outer' can be the frameset, between cable stops.

But if you put some numbers to this kind of thing you can get an idea of whether it is a real problem or not.

Suppose that the CTEs are 12 for the inner and (say) 20 for the 'outer' (each being parts per million, per degree C) this would make a differential of 8. Supposing the temperature changes by 25C, this gives 200ppm change.

This means that in a cable 1000mm long, it might cause a change in apparent cable length of about 0.2mm. Much to my surprise this may actually be significant, or at least potentially noticeable; this is about the same as one click on an indexed adjuster with four clicks per turn.

However it shouldn't be enough (by itself, anyway) to cause a real problem, I would have thought.

cheers

[[XAP]Bob]

What materials are those cte values for?

[Brucey]

they are (very loosely, from memory) chosen to represent those of a fairly conventional steel and an aluminium alloy. The differential CTE could be more or less than I've estimated, with different frame materials or cable materials. Similarly the cable length (between frame stops, or total) could be more or less than that, too.

If I've chosen poorly, do say!

cheers

[RickH]

... none of them use a power source other than the human in the saddle. That to me is an important distinction. It’s my ‘red line’.

I'm just wondering what equipment you use to do the liposuction in order to get a fuel source to burn in your bike lights?

Dynamo?

And using a dynamo to, say, charge the Di2 battery every 1000 miles (approx) is inherent different how? It reminds me of the Mennonites who won't use electricity - but it doesn't stop them using refrigerators, they just use ones that run on gas.

Are battery powered bike computers a no-no too? (Can you still get the ones that have the little star-wheel that is turned one click by a widget attached to the spokes like I used to have in the 70s?)

I don't have any Di2 stuff I'm just not inherently anti the technology and wondering why the line gets drawn at a particular point!

The instance mentioned about Pinot losing time due to gear problems could just as easily have been a purely mechanical problem - a cable problem on a mechanical setup could have just as effectively scuppered his chances.I expect there were more of those, particularly on the cobbles stage, that just get shrugged off as "one of those unfortunate things".

Rick.

[[XAP]Bob]

they are (very loosely, from memory) chosen to represent those of a fairly conventional steel and an aluminium alloy. The differential CTE could be more or less than I've estimated, with different frame materials or cable materials. Similarly the cable length (between frame stops, or total) could be more or less than that, too.

If I've chosen poorly, do say!

cheers

No idea - there just wasn't your usual level of detail in reporting the numbers. I've not considered it, because in my mind inners and outers are basically both steel, Although I do have an Al MTB with open runs, so that bit is subject to thermal variation.

Don't forget to halve the difference, since you always temperature check your setup when initialising it

OTOH the fact that it's one detent on a "normal" cable adjuster suggests that it is easily dealt with

[1942alexander]

I don't seem to have any problems on different temperature days with my set-ups. It can't be because I'm always going fast enough to keep them air cooled so it must be that I generate so much heat and so little forward motion that they are always hot.

ASG_Gears.JPG (14.3 KiB) Viewed 380 times

[JohnW]

I don't seem to have any problems on different temperature days with my set-ups. It can't be because I'm always going fast enough to keep them air cooled so it must be that I generate so much heat and so little forward motion that they are always hot.

ASG_Gears.JPG

CB_Gears.JPG

WFH_Gears.JPG

Are those bar-end levers friction or indexed?

[Dave W]

Good god whatever next
I think my frame has grown with the hot weather and buggered my gear settings My tyres are warm so my speedo is out. My lycra shorts don't fit so tight in the cold.

[reohn2]

Are those bar-end levers friction or indexed?

Both