gear ratios for Dawes SG

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robing
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gear ratios for Dawes SG

Postby robing » 2 Dec 2019, 11:01am

I have a 2011 Dawes SG and the gear ratios are 48-36-26 on the front and 11-32 on the back.
The newer ones are 11-34 on the back. Would mine take a 11-34 cassette without any modifications? Is it worth changing?

bgnukem
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Re: gear ratios for Dawes SG

Postby bgnukem » 2 Dec 2019, 11:42am

Suggest you find the model number (for Shimano, usually something like 'RD-Mxxx', where 'xxx' is a number) on the rear mech then google it to find out the cog capacity, i.e. whether a 34T sprocket can be accommodated?

mcshroom
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Re: gear ratios for Dawes SG

Postby mcshroom » 2 Dec 2019, 12:03pm

I think you have a MTB rear derailleur on that one (9 speed?). If so it should be a straight swap. You might need a slightly longer chain at the same time to cover the greater Big-Big combination.

rotavator
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Re: gear ratios for Dawes SG

Postby rotavator » 2 Dec 2019, 12:46pm

Is it worth changing?

It would give you a 6% easier bottom gear which would not be worthwhile (IMHO!) unless your current RD can cope with 34T and you need a new cassette and possibly a chain in any case. If it is a 9sp, I would check if the RD can handle a 36T cassette.

robing
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Re: gear ratios for Dawes SG

Postby robing » 2 Dec 2019, 12:55pm

I wasn't sure if the RD could cope with 34T and wondering if it was worth changing or not.

mcshroom
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Re: gear ratios for Dawes SG

Postby mcshroom » 2 Dec 2019, 1:25pm

I'm not sure you'd gain a massive amount, but the rear derailleur is a Deore LX model, so I'd expect it to handle 34t ok.

Pretty bike too :)

hamster
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Re: gear ratios for Dawes SG

Postby hamster » 2 Dec 2019, 1:39pm

Simpler to swap the inner chainring from 26T to 24T. Cost around £10 and a bigger effect too!

robing
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Re: gear ratios for Dawes SG

Postby robing » 2 Dec 2019, 2:17pm

hamster wrote:Simpler to swap the inner chainring from 26T to 24T. Cost around £10 and a bigger effect too!


Great! :)

freeflow
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Re: gear ratios for Dawes SG

Postby freeflow » 2 Dec 2019, 3:12pm

I have a 92/93 supergalaxy, bought just before manufacture moved overseas. It was kitted out with Deore Lx chainset and deraillieurs, 105 bar end shifters. It's now happily running 10 speed 11-42 with an additional gear hanger and original front and rear mechs. Just a few weeks ago the original BB started creaking and groaning so I upgraded the chainset to a Deore 40/30/22.
All is working well.

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Tigerbiten
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Re: gear ratios for Dawes SG

Postby Tigerbiten » 2 Dec 2019, 5:26pm

Another thing to think about .........

Going from 11-32 to 11-34 means not only will you get a bigger large sprocket but you'll also change some other sprockets as well.
It depends on which sprockets change versus which are the sprockets you most commonly use if you may or may not notice any difference.
If you suddenly get a bigger jump in the middle of your most commonly used gears, you may not be happy with the new ratios until you get used to them.

Luck .......... :D

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The utility cyclist
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Re: gear ratios for Dawes SG

Postby The utility cyclist » 2 Dec 2019, 7:19pm

robing wrote:
hamster wrote:Simpler to swap the inner chainring from 26T to 24T. Cost around £10 and a bigger effect too!


Great! :)


I have done this with every triple I own except the commuter which is a Deore c/set and rarely use the inner ring unless I'm deliberately trying to get wear out the small/small.
If your c/set is a 4 bolt 64mm BCD (on the inner) you can get them for under £6 posted the no.2 ring looks untouched https://www.ebay.co.uk/itm/BICYCLE-CHAI ... SfAX84vDtQ or https://www.ebay.co.uk/itm/Shimano-24T- ... Swdjha1Uyi can get them for £4 posted from China if that's enough to sway you from buying from a UK seller
I prefer this solution as you can keep the gaps between the ratios which stretch out as you get onto the wider range cassettes, hateful when transitioning loaded or pushing on up a slope and the gradient changes one way or the other.
Last edited by The utility cyclist on 2 Dec 2019, 7:35pm, edited 1 time in total.

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The utility cyclist
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Re: gear ratios for Dawes SG

Postby The utility cyclist » 2 Dec 2019, 7:23pm

freeflow wrote:I have a 92/93 supergalaxy, bought just before manufacture moved overseas. It was kitted out with Deore Lx chainset and deraillieurs, 105 bar end shifters. It's now happily running 10 speed 11-42 with an additional gear hanger and original front and rear mechs. Just a few weeks ago the original BB started creaking and groaning so I upgraded the chainset to a Deore 40/30/22.
All is working well.

How do you find the massive gaps between the ratios, I hate it when I use an 11-32 compared to a 12-28, god knows what it's like with a dustbin lid that size!

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Tigerbiten
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Re: gear ratios for Dawes SG

Postby Tigerbiten » 2 Dec 2019, 9:23pm

The utility cyclist wrote:
freeflow wrote:I have a 92/93 supergalaxy, bought just before manufacture moved overseas. It was kitted out with Deore Lx chainset and deraillieurs, 105 bar end shifters. It's now happily running 10 speed 11-42 with an additional gear hanger and original front and rear mechs. Just a few weeks ago the original BB started creaking and groaning so I upgraded the chainset to a Deore 40/30/22.
All is working well.

How do you find the massive gaps between the ratios, I hate it when I use an 11-32 compared to a 12-28, god knows what it's like with a dustbin lid that size!

Apart from at 20% between the 15t and 18t sprockets which can be worked around, the rest are roughly around 15-16%.
The chainrings are 30%/33% apart or around 2 sprockets so chainring shifts are easy/logical.
Also that setup isn't aimed at the ultra high gear range where you really need close gears, max gear is only around 100".
So as long as you're happy with the size of the steps between the gears, which isn't that important for low gears, then actually that combo of chainrings and sprockets works well for a wide gear range.

YMMV ........... :D

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The utility cyclist
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Re: gear ratios for Dawes SG

Postby The utility cyclist » 2 Dec 2019, 10:59pm

Those big gaps at the bottom end when you're pushing hard or even struggling is where the problems arise when you're transitioning on terrain, the cadence change is significant when you have such a big gap IME. I'm not worried about the higher gears as that rarely changes, it's only when cassettes get bigger that these issues crop up.

freeflow
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Re: gear ratios for Dawes SG

Postby freeflow » 3 Dec 2019, 9:36am

The utility cyclist wrote:How do you find the massive gaps between the ratios, I hate it when I use an 11-32 compared to a 12-28, god knows what it's like with a dustbin lid that size!


I know what you mean, but in practise, I have been greatly surprised that it has been a very good fit to the 'span' of my legs and my general (non racing) riding style. The only real downside I've noticed comes when riding with others, as the group speed may fall at the top or bottom end of the cadence range for the gear I am riding that I can't find a comfortable cadence by changing up or down a gear. When riding solo this isn't an issue. I still find myself doing a couple of sprockets at the back in a single change when the terrain changes (rather than the 4/5 I'd be doing on a 12-28).

There is method in my madness. I had a lovely custom Burls titanium bike that was stolen earlier this year. When looking at a replacement I was considering a pinion gearbox but was undecided between the P1.18 with 10% between gears its 18 gears or the P1.12 with 17.5% between the 12 gears. The advantage of the P1.12 was that a crowd funded group make STI style gear changers/brakes which work upto the P1.12 (but not P1.18) rather than having to use the rotary shifter (not best suited to drop handlebars). The 11-42 cassette was an experiment to see how I would cope with gearing of an average of 17.5% before I invested in a pinion gearbox. From my experience I decided that the P1.18 would be the better choice. I like the 11-42 so much that I haven't bothered to go back to a smaller cassette.

The pinion gearbox project was shelved when I had to divert the money to other more urgent needs so I've been riding 11-42 now for some seven months.

For background I'm now 62 with a BMI of 33 <sigh> and worrying twinges in my knees when I push too high a gear. I enjoy doing a bit of Audax but otherwise ride mainly on my own or with like minded colleagues as I can't abide the group politics/willy waving of cycle clubs. I have for many years eschewed the 50/39/30 triple in favour of 42/32/22 and the 40/30/22 was the simplest/ cheapest option when I knackered my original LX cranks during removal.

Above I referred to 'span'. This is a complex parameter but basically is a measure of how much cadence range you have before it becomes uncomfortable enough to change gear. If you ride at your aerobic limit then typically you will have a low span and therefore require a cassette with small percentages between gears. If you are a cruiser like myself and ride well below your aerobic limit, then you will have a wider span and therefore wider spaced gears at the rear are more acceptable and remove the annoyance of constantly changing two or three gears at the back to get back to a comfortable cadence.