Help with Gear ratios....?

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Cyclothesist
Posts: 309
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Location: Scotland

Re: Help with Gear ratios....?

Post by Cyclothesist »

You can just change the cage. It's not difficult. I swapped the original short cage on my 10 speed 105 for a Tiagra 4700 medium cage. SJS Cycles carry the innner and outer cage plates. You can likely reuse your jockey wheels if they're not too worn. Just make sure you don't mix up the upper and lower jockey wheels as they look the same but aren't.
slowster
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Re: Help with Gear ratios....?

Post by slowster »

The cassette is not the problem, and changing it is not the solution. 50/34 is evidently the wrong chainset for you, given the riding that you are doing and the terrain where you ride, and given your level of fitness.

Changing the chainset for one witth smaller rings that actually fit your needs and preferences is the correct solution, and will make riding more pleasurable. Riding a nice bike but with the wrong gears is frustrating and spoils the experience, whether it's because bottom is not low enough, top is not high enough (rare), the gaps between gears are too small or too big, or you find yourself constantly cross-chained.

The link below compares your current chainset with the Shimano's main low gear offering of 46/30, as on its GRX gravel chainsets. It only gives you one extra lower gear, and is unlikely to be the answer for you.

http://www.ritzelrechner.de/?GR=DERS&KB ... 0&UF2=2150

However, you can get other chainsets which (unlike GRX) give a choice of rings and a degree of customisation. The least expensive and one of the best options is the Spa Super Compact, which is available in 46/30, 44/28, 42/26 and 40/24. As shown in the link below, 42/26 for example would give you two lower gears. By comparing the your current gearing in the link with alternatives, you should also be able to determine whether the gears you use most are combinations that will result in cross-chaining.

http://www.ritzelrechner.de/?GR=DERS&KB ... 0&UF2=2150

A Spa Super Compact costs £79. You would also need to replace the bottom bracket with a square taper model, and almost certainly you would need a 'dropper' to lower the front derailler, e.g. like the ones linked below.

https://www.spacycles.co.uk/m8b0s109p33 ... cral-Rings

https://www.spacycles.co.uk/m16b0s110p3 ... om-Bracket

https://www.spacycles.co.uk/m8b0s106p51 ... On-Dropper

Assuming you do not have the requisite tools and experience to do this yourself, if you are anywhere near Harrogate I would suggest you go to Spa and get them to install it all.
Brucey
Posts: 44843
Joined: 4 Jan 2012, 6:25pm

Re: Help with Gear ratios....?

Post by Brucey »

rareposter wrote: 20 Apr 2024, 10:05pm Cross chaining on a 2x11 is irrelevant, the system is designed to run all 11 cogs in the big ring. Assuming the chain is long enough and the gears correctly set up, you'll get all cogs with no issues.
......big-big is fine.
IMHO cross-chaining was always a dumb idea and it still is.

All derallieur systems suffer two major types of loss; 1) chordal loss 2) cross-chaining loss. 1) is purely dependent upon the sizes of the sprocket and the chainring; here bigger is always better. Cross-chaining losses happen whenever the chainring is not well aligned with the sprocket. So small-small cops the lot; areal double dose, having the worst of both. Big-big has the lowest chordal losses of any gear, so with a nicer chainline it would be the most efficient gear. However, big-big ties with small-small for the highest cross-chaining losses. This means that in most double setups, there is gear ratio using the small chainring which is about the same gear, but slightly more efficient when measured. It may still be expedient to use big-big occasionally, eg. if you know you are staying on the big ring, but it often is not the most efficient gear of those available.

Unfortunately one of the few published experimental studies probably didn't show cross-chaining losses in their true light. The reason for this is that they used a low-mileage chain with a low-friction coating on it. In the real word the coating soon wears off, and once it has, cross-chaining losses would be expected to increase dramatically.
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rareposter
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Re: Help with Gear ratios....?

Post by rareposter »

slowster wrote: 21 Apr 2024, 10:08am A Spa Super Compact costs £79. You would also need to replace the bottom bracket with a square taper model, and almost certainly you would need a 'dropper' to lower the front derailler, e.g. like the ones linked below.
So based on this thread:
viewtopic.php?t=160179

the OP bought a (very nice) Trek Emonda SL5 with a 105 groupset.
The bike has a T47 BB so the only way to put a square taper in (that I'm aware of anyway) is a Phil Wood:
https://philwood.com/collections/square ... ackets/t47

That's ££££. In fact, taking all that into account, it works out as far and away the most expensive option, even though the chainset is only £79. Changing the chainset is almost invariably far more complicated (due to the plethora of BB standards) and costly than any other option and it usually results in further changes being needed as well - like the need for an adaptor to drop the front mech and adaptors for the BB.

Plus it would affect the top end gearing which the OP has already said he wants to keep as is.

If the gearing only needs to be slightly lower, a new 11-32 or 11-34 cassette would work - I suspect that the original mech would cope with it because Shimano are usually very conservative in their calculations although it would definitely struggle in big-big.
If the gearing needs to be lower than that, an 11-36 cassette and a Wolftooth mech hanger would be the easiest and cheapest.

And quite bluntly, if it needs to be lower still then the OP bought the wrong bike and/or needs to build up some fitness before tackling the steeper hills.
Brucey wrote: 22 Apr 2024, 12:09pm IMHO cross-chaining was always a dumb idea and it still is.
That's as maybe but if you give people those gears, they will use them (intentionally or otherwise) so it makes sense that the system can cope with it. SRAM in particular is fully designed around that - their gearing combinations work on the premise that the rider is in the big ring most of the time (to save on front shifting) with the small ring used only on steep climbs hence the chainring combinations of 35/48 and 33/46 coupled with a 10-33 cassette (12sp). Works really well in practice and all 12 cogs are completely accessible from the big ring.
Brucey
Posts: 44843
Joined: 4 Jan 2012, 6:25pm

Re: Help with Gear ratios....?

Post by Brucey »

rareposter wrote: 22 Apr 2024, 12:30pm That's as maybe but if you give people those gears, they will use them (intentionally or otherwise) .....
I don't disargee with much of what you say; I see people blithely pedalling small-small all the time, often to the point that the RD
wears out prematurely, because the pivots in the derailleur are loaded differently when the mech is against the limit screw. Years ago, mechs 'flapped themselves to death' all the time; however it is now very much less likely. Shimano's use of a diagonal tension spring improves matters in most of the gears, but the outside of the parallelogram is still completely unloaded when the mech is against the high gear limit screw, as it usually is when the smallest sprocket is selected. This means it is still possible for a mech to 'flap itself to death', just like the bad old days, but only when the smallest sprocket is selected is this likely to happen. In many cases this only ever occurs when small-small is selected.
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slowster
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Re: Help with Gear ratios....?

Post by slowster »

rareposter wrote: 22 Apr 2024, 12:30pm The bike has a T47 BB so the only way to put a square taper in (that I'm aware of anyway) is a Phil Wood:
https://philwood.com/collections/square ... ackets/t47

That's ££££.
I had not spotted the T47 bottom bracket, but it appears adapters are available, e.g. https://www.tradeinn.com/bikeinn/en/fsa ... IE6C_KKaKQ.
rareposter wrote: 22 Apr 2024, 12:30pm Plus it would affect the top end gearing which the OP has already said he wants to keep as is.
It's common for novices like the OP to be unduly concerned about spinning out, and to want higher top gears than they need.
rareposter wrote: 22 Apr 2024, 12:30pm And quite bluntly, if it needs to be lower still then the OP bought the wrong bike and/or needs to build up some fitness before tackling the steeper hills.
Which is what some in the cycling trade and clubs said in the 1970s about bikes with gears lower than 42 x 21. They also said the same about 42 x 23, then about 39 x 25, and then about 36 x 25.
Cyclothesist
Posts: 309
Joined: 7 Oct 2023, 11:34am
Location: Scotland

Re: Help with Gear ratios....?

Post by Cyclothesist »

rareposter wrote: 22 Apr 2024, 12:30pm
slowster wrote: 21 Apr 2024, 10:08am A Spa Super Compact costs £79. You would also need to replace the bottom bracket with a square taper model, and almost certainly you would need a 'dropper' to lower the front derailler, e.g. like the ones linked below.
So based on this thread:
viewtopic.php?t=160179

the OP bought a (very nice) Trek Emonda SL5 with a 105 groupset.
The bike has a T47 BB so the only way to put a square taper in (that I'm aware of anyway) is a Phil Wood:
https://philwood.com/collections/square ... ackets/t47

That's ££££. In fact, taking all that into account, it works out as far and away the most expensive option, even though the chainset is only £79. Changing the chainset is almost invariably far more complicated (due to the plethora of BB standards) and costly than any other option and it usually results in further changes being needed as well - like the need for an adaptor to drop the front mech and adaptors for the BB.

Plus it would affect the top end gearing which the OP has already said he wants to keep as is.

If the gearing only needs to be slightly lower, a new 11-32 or 11-34 cassette would work - I suspect that the original mech would cope with it because Shimano are usually very conservative in their calculations although it would definitely struggle in big-big.
If the gearing needs to be lower than that, an 11-36 cassette and a Wolftooth mech hanger would be the easiest and cheapest.

And quite bluntly, if it needs to be lower still then the OP bought the wrong bike and/or needs to build up some fitness before tackling the steeper hills.
Brucey wrote: 22 Apr 2024, 12:09pm IMHO cross-chaining was always a dumb idea and it still is.
That's as maybe but if you give people those gears, they will use them (intentionally or otherwise) so it makes sense that the system can cope with it. SRAM in particular is fully designed around that - their gearing combinations work on the premise that the rider is in the big ring most of the time (to save on front shifting) with the small ring used only on steep climbs hence the chainring combinations of 35/48 and 33/46 coupled with a 10-33 cassette (12sp). Works really well in practice and all 12 cogs are completely accessible from the big ring.
Great that you spotted that T47. That changes the order of things somewhat in terms of cost:benefit. The Emonda SL5 is a nice road bike with a 105 chainset that goes with the aesthetic. Sometimes a change from a 30 to a 34 cassette bottom gear can make a big difference in terms of perceived effort. Trying it is the only way to know. If I was the OP I'd change the SS cage to GS on the 105 RD (or look for a good deal on a GS derailleur) and fit an 11-34 cassette (I know a 12-34 or 13-34 would be better but try finding one, and at a good price). SJS cycles have rd 7000 inner and outer cage plates at £9.99 each.
It's worth trying out, isn't overly spendy and just may be all that's required.

*Edit* - remember to buy a new chain too, you're likely to need one 2-4 links longer than currently fitted.
Last edited by Cyclothesist on 22 Apr 2024, 8:02pm, edited 1 time in total.
Jezrant
Posts: 900
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Re: Help with Gear ratios....?

Post by Jezrant »

As above, 11-34 and modify or swap rear mech if necessary. Costs small beer given what you probably paid for the bike. You'll get fitter as you put in the miles. If the hills are still a struggle after a few long rides, maybe have a re-think, but I wouldn't change anything more for now.

Most touring cyclists like to ride bikes with much lower gearing, with or without extra baggage. Different strokes for different folks.
JohnR
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Joined: 6 Jul 2020, 3:51pm

Re: Help with Gear ratios....?

Post by JohnR »

It's the OP's call as to whether adding one more gear at the bottom is enough. There's the alternative of fitting an extender link to the medium cage derailleur and an 11 - 40 or 11 - 42 cassette which adds two more gears at the bottom compared to the current 11 - 30.
Usually riding a Spa Cycles Aubisque or a Rohloff-equipped Spa Cycles Elan Ti
Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: Help with Gear ratios....?

Post by Brucey »

it is also possible to fit special chainrings to 110mm bcd 'road' cranks, allowing fitment of a 30t inside ring IIRC. This does affect chainline, moving both rings leftwards slightly, leaving the big ring in the '1x' position. This is arguably an improvement, given how most folk ride 2x gears.
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Cyclothesist
Posts: 309
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Location: Scotland

Re: Help with Gear ratios....?

Post by Cyclothesist »

JohnR wrote: 22 Apr 2024, 8:30pm It's the OP's call as to whether adding one more gear at the bottom is enough. There's the alternative of fitting an extender link to the medium cage derailleur and an 11 - 40 or 11 - 42 cassette which adds two more gears at the bottom compared to the current 11 - 30.
Agreed. That's an additional option if the 34t isn't enough. You need the GS cage to use an extender on a double. Sunrace have a well made extender for about £10 and there are many others for less.
NickJP
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Location: Canberra, OZ

Re: Help with Gear ratios....?

Post by NickJP »

Cyclothesist wrote: 22 Apr 2024, 9:52pm
JohnR wrote: 22 Apr 2024, 8:30pm It's the OP's call as to whether adding one more gear at the bottom is enough. There's the alternative of fitting an extender link to the medium cage derailleur and an 11 - 40 or 11 - 42 cassette which adds two more gears at the bottom compared to the current 11 - 30.
Agreed. That's an additional option if the 34t isn't enough. You need the GS cage to use an extender on a double. Sunrace have a well made extender for about £10 and there are many others for less.
Although the Ultegra long cage 8000 RD is only rated by Shimano for use with a 34t big cog, I know that it copes OK with an 11-40 cassette, as that's the combination that we're using on our tandem. Thre are several videos on Youtube showing this combination working. e.g.
Carlton green
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Re: Help with Gear ratios....?

Post by Carlton green »

PaulK wrote: 20 Apr 2024, 11:05am Hi All

I have a Shimmanno105 Groupset on a roadbike.

50\34 Compact Chain ring
11 speed 11-30 Cassette

I live in a hilly area and have heard switching to an 11-32 cassette will be a good move to consider (the hills are a rather punishing and im pretty sure i end up cross chaining which is obv not a good thing)
.
However have also read the jumps between gears on an 11-32 are not optimal and an 11-34 would be better...?
Im really not sure what is meant by this..?

As the small cog teeth count remains the same i assume it wont affect spinning out of gears during the fun part of going down these hills ..?

Would peeps here suggest going with 11-32 or 11-34 and why ..?

P
It seems to me that you’re trying to do too much and not focusing on your core needs (eg. getting up hills and making good time on the mostly level sections).

Change the rear derailleur to accept bigger sprockets and then fit the biggest sprockets that are practical for you to install. Spinning out going fast down hill is a luxury and probably sees you going somewhat fast too. It wouldn’t particularly harm your enjoyment to increase the small sprocket size from 11. At one point 52 x 13 was considered a very high gear and I still do think of it that way.

To some extent there is an obsession about riding up every hill. Whilst it’s good to have the gears to ‘ride up the side of a house’ there’s almost no good reason not to ‘pace yourself’ and walk up a few hills. That might be hard to believe but it’s still true.
Don’t fret, it’s OK to: ride a simple old bike; ride slowly, walk, rest and admire the view; ride off-road; ride in your raincoat; ride by yourself; ride in the dark; and ride one hundred yards or one hundred miles. Your bike and your choices to suit you.
Cyclothesist
Posts: 309
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Location: Scotland

Re: Help with Gear ratios....?

Post by Cyclothesist »

JohnR wrote: 22 Apr 2024, 8:30pm
Although the Ultegra long cage 8000 RD is only rated by Shimano for use with a 34t big cog, I know that it copes OK with an 11-40 cassette, as that's the combination that we're using on our tandem. Thre are several videos on Youtube showing this combination working. e.g.
Cool, though it looks pretty tight on a 40t and he seems very wary of running it in the big chainring. It would suggest a 36t is very doable, and safe for the derailleur. For the price of a cassette and new chain that seems like the one to try first.
PaulK
Posts: 24
Joined: 5 Mar 2024, 6:21pm

Re: Help with Gear ratios....?

Post by PaulK »

Hi All

Sorry didn't mean to start a posting war.
Yes my core fitness whilst it is improving significantly needs to be better having driven a desk for a significant while now will do that to you. Practice and weighs will help me here im sure.

I don't spin out of gears on any but the steepest down hill sections (i did it yesterday and scared myself stupid in the process).

I had of course considered a chainring with less teeth, but the options and practicality of doing so seemed very complicated and was not something i decided to proceed with.
My thinking is that as my strength and core fitness increases i will spend longer in the large chainring.

Spoke to my bike shop yesterday and apparently i dont need whole new mech to change out the rear cassette as it can still be done but only the cage needs to be swapped out for a medium cage, which is something i didn't know was possible.

I suppose with a bigger cassette there is still the opportunity to occasionally cross-chain in a 34T on difficult hills etc but the 30T cog (my current lowest) will be available to me without cross-chaining as it is the next cog down in the RD.

P
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