Lower gears

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Paul Smith SRCC
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Re: Lower gears

Postby Paul Smith SRCC » 27 Jul 2016, 7:32pm

martin113 wrote:.... But the posts about using a mtb 9 speed rear mech with my Ultegra 10 speed shifters has confused me. Can anyone tell me in easy language whether an XT would work? Better still, is there a decent mtb rear mech which would work and not be so expensive as XT?

The combination I referenced earlier was the Shimano Ultegra 6700 10 speed shifter (and 6703) with the 9 speed Shimano Deore M591 did work, I don't recall ever fitting the XT of that generation but that may have also been viable; the later versions of both Deore and Deore XT when we tried them didn't.
Last edited by Paul Smith SRCC on 27 Jul 2016, 9:45pm, edited 6 times in total.

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Re: Lower gears

Postby Paul Smith SRCC » 27 Jul 2016, 7:48pm

recordacefromnew wrote:...Are you sure your Centaur front mech is designed for front rings smaller than 30T?....

Going past the capacity of a rear mech' can be an issue, as you normally have to compromise in either the chain being long or short and a mis shift into the extreme gears of smallest chainring with smallest sprocket or vice versa can result in tears. Arguably pushing the front mech' past capacity is slightly less traumatic.

I personally use a 26/36/46 ring and yes as you can see below the radius of the rings differs from the front mech', that can and in my case does conclude in poor shifting, especially shifting down from middle to small ring, the cage being to far from the ring to derail the chain onto the small ring. It works well enough for me if I'm careful and or lucky, I try and change down not under load and three or four sprockets down, which does help, but it is a compromise. Note I referenced 'lucky', on occasion on a bike used for touring often I am riding on unknown roads and on more than one occasion I have misread the conditions, a steady long middle ring climb in the Pyrenees can hairpin into a small ring climb without warning, changing down under load simply doesn't happen, those moments I smile, turn round coast downhill to take off the load and engage small ring.

In conclusion we all have a different perception of what is and what isn't acceptable when it comes to compromises!
Image

Regarding gear ratios I have listed the below before but maybe of interest in this thread. Desired ratios can be very personal to each rider, some prefer to spin with a faster cadence and others prefer a higher gear with slower cadence. What you need to do is work out what ’Gear Ratios’ you like to use and then try and achieve them, making sure they are correctly positioned, no point if mathematically you can only get your most common used gear in largest ring largest sprocket.

By way of an example that is all I have done on my ’Tour Bike' I use a 13-29 Campagnolo 10 speed set up with a 26-36-46, which gives me all that I am after

Image

It does take a bit of thought as to what you need both in terms of ratios and then equipment choices to achieve them, but it can often be achieved. In my case for example back in 2007 I did invest in a high quality chainset (TA Carmina) to get the ring combinations I wanted, as for me personally I find many road specific triples to large for me and the ATB chainsets too small for what I want. That said you need not invest as heavily as I did, I was to an extent treating myself so something I wanted.

Note I said 'wanted' not 'needed', my tour bike is used for tours, often I want to climb a long mountain pass with little effort to take in the scenery, so I chose lower gear ratios on that bike. Sportive bikes by comparison are normally ridden with no luggage, plus set up generally for riding at a higher speed than a touring bike. You can see from that gear chart above that a 34t inner chain ring with a 27t largest sprocket results in a 34" gear, which until a couple of years ago was a common set up on a Sportive bike. Note Shimano road cassettes then evolved to offer upto 28t, then 30t and the Shimano 6800 Ultegra now offers upto 32t, resulting in a lower gear ratio than the previous generation triple transmission offered! As I said, even the 34 ring 27t sprocket combination gave a lowest gear ratio of approx' 34", on that style of bike that for many was low enough for most riders, even on a mountain pass.

To try and explain what a 34" gear ratio equates to, well I'm no fabulous racing whippet, but when I rode from 'Lands End to John O'groats, (LEJOG)’ I used a higher gear than that and I rode up every climb. In that specification I also toured the High Alps with two full panniers and again rode every climb; just, but I did it. That said I do believe that the way the compact transmissions have gradually evolved from 34 chainring to 27t rear sprocket, then 28t, to 30t and now on some 32t largest rear sprocket does result in more usable gears on the large chainring and more importantly in the correct chainline locations, on the small ring it gives you a gear for riding high mountain passes; or a get out of jail gear if in short you have just blown up! The Shimano 6800 group now offers such a low gear they dropped the triple version, personally I would like to have seen the triple still offered in 30t chainring 32t largest rear sprocket

Although a 34" gear was OK for me on 'Lejog' I realised when I was riding in a group I had to keep the gear turning on the climbs and ride quicker than many of my new friends, who were using lower gear ratios than me and able to ride at a slower more sociable pace, that along with wanting to take in the scenery is why you will now see that bike had a triple in some of the later tour articles. As I said gear ratio choices can take some thought, the decision may not always be down to ability. In my case for local rides I seldom, if ever need to use it the smallest ring, I have even done full tours in quite hilly areas and never once used it, yet I have no intention of taking it off as I know that it’s there if wanted, arguably I could have fitted a larger small ring and still been happy, as my choice of chain ring sizes is more for to achieve the 46-36 combination than it is the 26.

Note my bike is an Audax bike, I have mentioned it purely to illustrate the thought process that can go into deciding what gear ratios to go for. An Audax bike like mine is often used potentially for slower tours, as such many spec' a triple over a double, where as some are set up more as fast day ride/sportive bikes, as I said above normally used for a slightly faster style of riding, as such they will normally have higher gear ratios than my Audax bike as a result. Just because I have set my bike up with a very specific set of gear ratios and more importantly the equipment choices I have used to achieve them, it doesn’t mean that I therefore believe what manufacturers normally supply are as such wrong; far from it, for the majority of Audax bikes-riders, they can achieve what they personally are looking for with normal road triples of 30-40-50 or 32-42-52; likewise many Sportive bikes-riders find that the 34-50 double compact transmission also offer their desired ratios; especially now that 32t sprockets are becoming more and more common place. Along the same lines in many ways what I have done arguably is not recommended for the reasons I referenced above.
Last edited by Paul Smith SRCC on 29 Jul 2016, 7:18am, edited 2 times in total.

hamster
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Re: Lower gears

Postby hamster » 28 Jul 2016, 8:52am

This is a good example of how the bike frame design really affects outcomes. My setup (24/39/48 with 12-23 rear) doesn't have the problem of poor shifting on the front - even though the front mech is exactly the same as Paul's. I think it is two reasons: firstly having the middle chainring larger then halfway tends to result in better shifting. Secondly, my frame has a very short rear triangle so the chain exits the chainset at much steeper angles. Put the two together and the two marginal gains give a better result.

As it's a fast road frame I can use a 39T comfortably as I would never tour or fit panniers on it - otherwise I'd want a 36T.

Back to the OP's point about 10 speed road and 9 speed MTB: Shimano changed the cable pull for their MTB mechs at 10 speed. Before all road and MTB were interchangeable. So if you want to run a 10 speed road shifter with an MTB mech it needs to be a 9-speed or earlier one. As earlier mechs were not designed for the very wide 10s cassette, you are best off with the latest (9 speed) one.

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Re: Lower gears

Postby Paul Smith SRCC » 28 Jul 2016, 7:09pm

hamster wrote:This is a good example of how the bike frame design really affects outcomes. My setup (24/39/48 with 12-23 rear) doesn't have the problem of poor shifting on the front - even though the front mech is exactly the same as Paul's. I think it is two reasons: firstly having the middle chainring larger then halfway tends to result in better shifting. Secondly, my frame has a very short rear triangle so the chain exits the chainset at much steeper angles. Put the two together and the two marginal gains give a better result.

As it's a fast road frame I can use a 39T comfortably as I would never tour or fit panniers on it - otherwise I'd want a 36T.....

I concur it's the middle to small ring where I have the main issue, it works with minimal yet required sensitivity, but yes a slightly larger ring, more acute chain line and the 23t largest rear sprocket versus my 29t will also help, as that will pull the chain closer to the radius of the ring. All would combine and probably morph the changes back into working as it should as apposed to nearly as it should.

I'm not sure what bike you have, my Van Nicholas Yukon has 425mm chainstays, where as faster set up bikes are normally at least 15mm shorter.
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hamster wrote:..Back to the OP's point about 10 speed road and 9 speed MTB: Shimano changed the cable pull for their MTB mechs at 10 speed. Before all road and MTB were interchangeable. So if you want to run a 10 speed road shifter with an MTB mech it needs to be a 9-speed or earlier one. As earlier mechs were not designed for the very wide 10s cassette, you are best off with the latest (9 speed) one.

I would still recommend caution as we tried several of the 9 speed Deore rear mechs that came after the M591 model, as well as the later generation 9 speed XT and none worked.
Last edited by Paul Smith SRCC on 29 Jul 2016, 7:20am, edited 5 times in total.

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Re: Lower gears

Postby freeflow » 29 Jul 2016, 7:13am

I'm using Deore XT 44/32/22 chainset with an ultegra 6703 front mech. The sti were ultegra 6603 but now 105 5703. Both work(ed) absolutely fine. The rear is sram 12-36 cassette and deore XT shadow 9 speed derailleur (M772). I've done around 10,000 km Audax rides since jan 2015 on this setup.

Very occasionally a front shift causes a nasty crunching when trying to do two a two click change. Using a slower change sequence of click 1-2-3 click has never caused a crunching.

The front mech sits about 1 cm above the large chainring which is a constraint imposed by the chainstay when on the 22 tooth chainring.

Prior to this I had lower gears by replacing the 30 tooth chainring with a 24 tooth using an Ultegra 6603 chainset. This wouldn't work with a 6703 chainset doe to design changes.

I switched to the XT chainset as I very rarely used the 52 chainring.

If I was approaching this again I'd stay with the 52/39/24 chainset but fit a 16-30 cassette (made from a 16-27 and 11-30 cassettes) as I've now demonstrated to my satisfaction that this works nicely albeit with the loss of some of the very low gears.

The 16 tooth start at the cassette means that a 52 tooth chainring becomes sensible gearing ( for me).

For Shimano cranksets the model number is usually printed on the back of the cranks at the pedal end.

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Re: Lower gears

Postby hamster » 29 Jul 2016, 8:59am

Paul Smith SRCC wrote:I'm not sure what bike you have, my Van Nicholas Yukon has 425mm chainstays, where as faster set up bikes are normally at least 15mm shorter.

I would still recommend caution as we tried several of the 9 speed Deore rear mechs that came after the M591 model, as well as the later generation 9 speed XT and none worked.


It's a 1994 Litespeed Catalyst. You cannot get a fingertip between the rear tyre and seat tube, so yes, it's short!

Agreed on the rear mechs, none were made for 10 speed cassette dimensions especially the overhanging bottom gear. So while the indexing should work, other factors like very thick dropouts can mean that they lack the necessary range of travel.

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Re: Lower gears

Postby Vetus Ossa » 29 Jul 2016, 10:13am

Martin…I’m in the same boat as you…old bloke with ultegra equipped Trek Madone needing lower gears, the only difference being my bike has a compact chainset.
Thanks to Paul’s and others advice here I have purchased a 9 speed M/B rear mech, 11-34 cassette and new chain. This will give me a bottom gear of 27” which will be low enough for me, a 36 sprocket would of course have given me an even lower gear.
This may be more tinkering than you want to do but if not I don’t see why it shouldn’t work for you.
How does my new setup work…I’ll let you know when my birthday comes next week and I am able to play with my new toys.

You may be interested in my thread…
viewtopic.php?f=5&t=107694

martin113
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Re: Lower gears

Postby martin113 » 29 Jul 2016, 6:34pm

Thanks for the help but can anyone tell me how to find out which Ultegra shifters I have already on the bike? The specs that came with the bike just give Ultegra sti, no model number. Will it be on the shifters somewhere?

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Re: Lower gears

Postby Vetus Ossa » 29 Jul 2016, 7:07pm

martin113 wrote:Thanks for the help but can anyone tell me how to find out which Ultegra shifters I have already on the bike? The specs that came with the bike just give Ultegra sti, no model number. Will it be on the shifters somewhere?


Peel forward the rubber hood and you will find it embossed on the outside of the lever body. You may need to pull the tape a little aside to see it.

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Re: Lower gears

Postby Paul Smith SRCC » 29 Jul 2016, 7:12pm

martin113 wrote:Thanks for the help but can anyone tell me how to find out which Ultegra shifters I have already on the bike? The specs that came with the bike just give Ultegra sti, no model number. Will it be on the shifters somewhere?

If 10 speed it sounds like Shimano Ultegra 6700/03 (the 6703 being the triple specific parts) as 6600 was 9 speed (edit, sorry also 10 speed, see recordacefromnew post below) and 6800 is 11 speed; looks like that below. Also came with a sliver chainset, brake caliper and mechs', STI levers were still black.

Image

Inside the LH crank near the pedal you will have the crank length and model number, the later 6800 model shown below purely to show you the location

Image
Last edited by Paul Smith SRCC on 29 Jul 2016, 9:48pm, edited 2 times in total.

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Re: Lower gears

Postby recordacefromnew » 29 Jul 2016, 8:01pm

martin113 wrote:Thanks for the help but can anyone tell me how to find out which Ultegra shifters I have already on the bike? The specs that came with the bike just give Ultegra sti, no model number. Will it be on the shifters somewhere?


Paul has shown you the 6700/6703 above already. The 6600/6603 were also 10 speed. They look quite different:

Image

Unless you would prefer having an XT label, I would go for a RD-M592 9 speed SGS (i.e. long cage) rear mech, which is widely available (e.g. from crc). I would go for it because it is shadow, it is designed for 36T, and it has the correct cable pull ratio for indexing with your 10 speed road shifter.

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Re: Lower gears

Postby Paul Smith SRCC » 29 Jul 2016, 9:44pm

recordacefromnew wrote:....Paul has shown you the 6700/6703 above already. The 6600/6603 were also 10 speed....

Apologies, correct the 6600/6603 is indeed 10 speed and not 9 as I mentioned up thread, I couldn't quite remember and a quick Google search to clarify if it was 9 or 10 speed for once failed me! :oops: More haste, less speed as they say, that can be a trouble with Forums; what should I do when my dinner is in the oven, then before you know it, 'pinggggggggggg' :lol: !

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recordacefromnew
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Re: Lower gears

Postby recordacefromnew » 29 Jul 2016, 10:07pm

Paul Smith SRCC wrote: :oops: More haste, less speed as they say, that can be a trouble with Forums...


And also the power with Forums. Just think of the trail of destruction I would have left, if it weren't for others making corrections of mistakes I made... :shock: :oops: :lol:

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Re: Lower gears

Postby martin113 » 1 Aug 2016, 11:52am

Unless you would prefer having an XT label, I would go for a RD-M592 9 speed SGS (i.e. long cage) rear mech, which is widely available (e.g. from crc). I would go for it because it is shadow, it is designed for 36T, and it has the correct cable pull ratio for indexing with your 10 speed road shifter.


Thanks for all the help. So I have the Ultegra 6603, which involves a mighty amount of silver on the bike. I could go for the M592 9 speed SGS or the M591. Given the state of my knees I either get some low gears or leave this bike at home and I would definitely prefer the first option. The M592 will let me use a 36t sprocket but it is black and ugly and is going to spoil the look of an eye-wateringly nice bike (hope I'm not offending anyone here). I could live with that if I have to. The M591 comes in a silver version and will suit the bike much better but will only go to a 34t sprocket. But there is a review I found saying that it could be stretched to a 36t at a pinch.

Recordacefromnew, You mention "an XT label". I have seen an XT M772 9 speed which has some nice silver in it. http://www.chainreactioncycles.com/shim ... lsrc=aw.ds
Would this suit the 10 speed shifter and go to a 36t sprocket? And would I need the medium or the long cage? Thanks for helping a completely non-tech rookie here.

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Re: Lower gears

Postby Neilo » 1 Aug 2016, 12:03pm

martin113 wrote: I have seen an XT M772 9 speed which has some nice silver in it. http://www.chainreactioncycles.com/shim ... lsrc=aw.ds
Would this suit the 10 speed shifter and go to a 36t sprocket? And would I need the medium or the long cage? Thanks for helping a completely non-tech rookie here.


Yes, I have one one my CdF, 50-34 up front and 36-12 on the back, works fine.
If it aint broke, fix it til it is.