Should All Gears Work?

marcobraynio

Hi

I have just bought my first road bike after many years on a hybrid which I used for commuting. It has a Shimano 105 Groupset which is cool, but I can't shift to all gears without the chain rubbing on the front derailleaur.

I have managed to adjust previous bikes so that the whole gear range can be used, but I can't manage it on this. is this something which is specific to road bikes and/or this groupset. It is very rare that I would use the big rear cog and the large front together or the small rear and small front but surely you should still be able to engage them?

It has two cogs on the front and 10 on the rear.

Thanks

Mark

anto164

Trim function on the front shifter.

like you're going to shift to the small chainring, but only push until the first click.

You probably won't be able to use all the gears at the back without the trim functin on the large ring.

rafletcher

That's perfectly usual - the chain rub that is. You don't have 20 distinct and separate ratios, you probably have 15 or so, and their is an overlap between the ratios available in the big and small chainrings

Whilst you can go "big-big" and indeed I've seen pros do it so that when they crest a climb they just have to shift up gears at the back, it'll bugger the chain in short order - and rub on the front mech cage. Best practise is to use say sprockets 1-8 with the small chainring and 3-10 with the larger - 1 being the largest sprocket.

thecrofter

On a very simple spread sheet work out the ratios you've actually got you'll find there is quite a bit of overlap and it's never necessary to cross-chain. Pro's will cross chain but they've got a mechanic to replace chains and cassettes every day if required.

1-1 1.2
1-2 1.304347826
1-3 1.428571429
2-1 1.56
1-4 1.578947368
2-2 1.695652174
1-5 1.764705882
2-3 1.857142857
1-6 2
3-1 2.000
2-4 2.052631579
1-7 2.142857143
3-2 2.174
2-5 2.294117647
1-8 2.307692308
3-3 2.381
1-9 2.5
2-6 2.6
3-4 2.632
2-7 2.785714286
3-5 2.941
2-8 3
2-9 3.25
3-6 3.333
3-7 3.571
3-8 3.846
3-9 4.167

These are the ratios on my Giant, with a triple, as you can see if I was in 1-8 for example it's almost exactly the same as 2-5, or conversely if I was in 3-1 it's almost the same as 2-4. Once you know what the ratios are you can find the right gear and keep the drive straighter thereby limiting losses in power. Basically I tend to be in 3,4,5,6 on the rear and when I reach the end of those limits it's time to change the chainring, unless the circumstances are reasonably exceptional.

CiB

This is the same chart idea as thecrofter's (above) but for 53/39 rings on a 12-25 cassette, which is probably closer to your 105.

Note the number of gears that produce a near identical ratio - 39/19 & 53/25 ~4.0, 39/17 & 53/23 both = 4.4.

The two salient points are that you can get the same gear in more than one combination, and that for most of us who don't have a mechanic to rebuild the bike after each day's riding it's generally considered a no-no to run the chain on the big-big or small-small combinations.

39-25   3.0
39-23   3.2
39-21   3.5
39-19   3.9
53-25   4.0
39-17   4.4
53-23   4.4
39-16   4.6
53-21   4.8
39-15   5.0
39-14   5.3
53-19   5.3
39-13   5.7
53-17   5.9
39-12   6.2
53-16   6.3
53-15   6.7
53-14   7.2
53-13   7.8
53-12   8.4

marcobraynio

Trim function? GENIUS - thanks chaps.

elmsallmissile

marcobraynio wrote:

Trim function? GENIUS - thanks chaps.

you still should not be doin' it though!

woodbloke

rafletcher wrote:

That's perfectly usual - the chain rub that is. You don't have 20 distinct and separate ratios, you probably have 15 or so, and their is an overlap between the ratios available in the big and small chainrings

Whilst you can go "big-big" and indeed I've seen pros do it so that when they crest a climb they just have to shift up gears at the back, it'll bugger the chain in short order - and rub on the front mech cage. Best practise is to use say sprockets 1-8 with the small chainring and 3-10 with the larger - 1 being the largest sprocket.

I have a 105 groupset as well, and if I'm reading you correctly, the three largest sprockets ought not to be used with the bigger chainring?...I've noticed the rubbing as well and thought it odd, but If the three big sprockets don't get used that it would make sense...kinda - Rob

Velonutter

Sorry lads I really don't have a problem with running the big-big small-small concept.

I run Campag 10 & 11speed on all my bikes and if they are set up correctly then there is never any issue.

However I rarely run the small-small, as my gears are really set up nicely to enable smooth changes on the front mech. I do however regularly run big-big and never have any issues.

The only time mates have had issues is if their mechanic has been less than generous when cutting the chain and it has been left too short.

I run 5339 with 25/11 and 50/34 with 27/12 and never have an issue, perhaps it is something to do with Shimano??? :?

sheffsimon

Velonutter wrote:

Sorry lads I really don't have a problem with running the big-big small-small concept.

I run Campag 10 & 11speed on all my bikes and if they are set up correctly then there is never any issue.

However I rarely run the small-small, as my gears are really set up nicely to enable smooth changes on the front mech. I do however regularly run big-big and never have any issues.

The only time mates have had issues is if their mechanic has been less than generous when cutting the chain and it has been left too short.

I run 5339 with 25/11 and 50/34 with 27/12 and never have an issue, perhaps it is something to do with Shimano??? :?

Same here, generally ride on big ring and quite often ride on big-big on Campag 10 speed 53/39 and 12/21 - no issues with chain wear etc.

crescent

It's not just about the derailleur rubbing at the front - as others have pointed out the trim function should take care of this. What will cause damage to the chain is the fact that when on the big-big or small-small configuration the chain is skewed and the links and cogs will rub on each other eventually causing erosion.

Cheers

Velonutter

Crescent wrote:

It's not just about the derailleur rubbing at the front - as others have pointed out the trim function should take care of this. What will cause damage to the chain is the fact that when on the big-big or small-small configuration the chain is skewed and the links and cogs will rub on each other eventually causing erosion.

Cheers

No Can't agree with that, I measure my chains regularly with a Park Chain Tool and regularly get between 2000-2500 miles before my chains get any where near the 75 mark.

With my gears (Campag) I rarely have to trim either, if you set the gears up correctly in the first place then it should all work perfectly.

Maybe I don't get the problems because I ride Campag :roll:

Headhuunter

woodbloke wrote:

rafletcher wrote:

That's perfectly usual - the chain rub that is. You don't have 20 distinct and separate ratios, you probably have 15 or so, and their is an overlap between the ratios available in the big and small chainrings

Whilst you can go "big-big" and indeed I've seen pros do it so that when they crest a climb they just have to shift up gears at the back, it'll bugger the chain in short order - and rub on the front mech cage. Best practise is to use say sprockets 1-8 with the small chainring and 3-10 with the larger - 1 being the largest sprocket.

I have a 105 groupset as well, and if I'm reading you correctly, the three largest sprockets ought not to be used with the bigger chainring?...I've noticed the rubbing as well and thought it odd, but If the three big sprockets don't get used that it would make sense...kinda - Rob

Most people will advise against "crossing the chain" from big chainring to big gear at the back or small to small, as you say, you should avoid using perhaps the 3 largest rear gears with the largest chainring and the same with the small... This is one of the top 3 cardinal rules of cycling, although judging by the number of people cycling round London with a crossed chain, most noobs are blissfully unaware of this.

However that is traditional thinking and as you can see here, some believe that there is no problem crossing the chain. Personally I try to avoid it, I also believe that crossing the chain causes the links to wear and in any case, as others have pointed out, running from large front to large back has the same gearing ratio as perhaps small front and 4th at the back anyway, so crossing the chain is completely unnecessary anyway...

oldwelshman

Velonutter wrote:

Crescent wrote:

It's not just about the derailleur rubbing at the front - as others have pointed out the trim function should take care of this. What will cause damage to the chain is the fact that when on the big-big or small-small configuration the chain is skewed and the links and cogs will rub on each other eventually causing erosion.

Cheers

No Can't agree with that, I measure my chains regularly with a Park Chain Tool and regularly get between 2000-2500 miles before my chains get any where near the 75 mark.

With my gears (Campag) I rarely have to trim either, if you set the gears up correctly in the first place then it should all work perfectly.

Maybe I don't get the problems because I ride Campag :roll:

Sorry but it is nothing to do with campag, and your tool only measures chain stretch not internal wear.
If you use the large large or small small combo the chain line is not perfect so it will wear the inner plates of the chain and your sprockets but as your rich having campag you can afford it

morstar

Oh sod it. I ride a compact and spend 95% (maybe more) on the 50 tooth front ring and use the whole cassette at the back. No problems with chain wear so far. Yes, I'm sure I am shortening it's life but not catastrophically so. I find it a far more convenient riding technique on every ride and the extra chain after a hundred+ hours of riding is probably worth it.
For what it's worth, my current chain has done 1,200 miles and looks good so far. Only time will tell.
I've even ridden in the wet and on muddy roads. It is a bike after all.

mattgoodman

Hi all,

I have Shimano 2300, with 52 x 39 x 30T chainrings... and Shimano HG-50, 8 speed, 12-25t cassette.

How do i work out my ratios?

Many thanks,
Matt

morstar

Some helpful soul will post a link no doubt but I can't on my phone.

Google 'Sheldon Brown gear calculator'. The font of all knowledge awaits you.

CakeyPirate

Big on the front (50 Compact) and 3rd biggest on the back is my fave gear

crescent

Velonutter wrote:

No Can't agree with that, I measure my chains regularly with a Park Chain Tool and regularly get between 2000-2500 miles before my chains get any where near the 75 mark.

With my gears (Campag) I rarely have to trim either, if you set the gears up correctly in the first place then it should all work perfectly.

Maybe I don't get the problems because I ride Campag :roll:

I think we are at crossed purposes here. My point is that, regardless of how well set up your gears are or which manufacturer you use, there are in reality only a handful of combinations where the chainring and cog are in the same plane and there is little or no skewing of the chain. All other combinations will skew the chain to some degree. For the main part this is imperceptible but is at its most pronounced on the big-big or small-small combination. It doesn't mean you can't use these combinations otherwise we would all be cycling around on 3-speed transmissions. What I am saying is that it is not just about the chain rubbing on the front mech - it is easy enough to adjust you derailleur or set the trim up to counteract this - but it is a mechanical certainty that there will be an element of rubbing between the chain links and the teeth of the gears when the chain is skewed at an angle. I'm not sugegsting your chain will snap after riding like this for a couple of miles but prolonged exposure will undoubtedly have an adverse effect on your chain.
To the best of my knowledge there is no adjustment that allows you to change the plane between the front and rear cogs/rings whilst you are moving.

Cheers

CiB

I avoid using big-big & small-small for the same reason that I push the handbrake button in when applying said brake; it's just nicer to do it without the accompanying mechanical noise. In my mind, it's doing it properly instead of the old 'so what?' approach.

oldwelshman

morstar wrote:

Oh sod it. I ride a compact and spend 95% (maybe more) on the 50 tooth front ring and use the whole cassette at the back. No problems with chain wear so far. Yes, I'm sure I am shortening it's life but not catastrophically so. I find it a far more convenient riding technique on every ride and the extra chain after a hundred+ hours of riding is probably worth it.
For what it's worth, my current chain has done 1,200 miles and looks good so far. Only time will tell.
I've even ridden in the wet and on muddy roads. It is a bike after all.

When you change your chain, you will have to replace cassette also, almost certain fo that.
I dont us large large or small small but I do use large fron and 2nd largest rear. Recently replaced chain and found I was slipping when using 2nd largest rear sprocket, this was the only gear I had slip on so I had to replace cassette also.