Getting the ideal position

DIscuss anything relating to non-standard cycles and their equipment.
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n0ct0
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Joined: 27 Apr 2020, 2:11pm

Re: Getting the ideal position

Postby n0ct0 » 25 Aug 2020, 12:31pm

Plugging 9 to 36 teeth on the back with 46t on the front with a SA IGH on a 559 rear wheel I get 5.6mph to 32.7mph with a cadence of 80rpm.

I have a similar set up on my Speedmachine running 155mm cranks, apart from it's a SRAM DD3 hub which has slightly wider ratios. I have an 11-40 teeth cassette and a 34t on the front. So I get 4.18mph to 24.7mph, and it still sometimes feels overgeared on big hills after a long ride. I know I'd drop the gearing if I was touring.

Anyway, I'm getting off track, but to me it looks like you're overgeared. Certainly if you're thinking of going with shorter cranks.

Grldtnr
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Joined: 11 Jun 2020, 7:04pm

Re: Getting the ideal position

Postby Grldtnr » 25 Aug 2020, 1:14pm

n0ct0 wrote:Plugging 9 to 36 teeth on the back with 46t on the front with a SA IGH on a 559 rear wheel I get 5.6mph to 32.7mph with a cadence of 80rpm.

I have a similar set up on my Speedmachine running 155mm cranks, apart from it's a SRAM DD3 hub which has slightly wider ratios. I have an 11-40 teeth cassette and a 34t on the front. So I get 4.18mph to 24.7mph, and it still sometimes feels overgeared on big hills after a long ride. I know I'd drop the gearing if I was touring.

Anyway, I'm getting off track, but to me it looks like you're overgeared. Certainly if you're thinking of going with shorter cranks.


But that's just number crunching, does that equate to real time feel?
To be honest, I don't have a bike computer, I gave up on them yonks ago, finding I was racing myself, but I am fairly happy with how fast I am now, just wanting to find the right ratios, on the flat I can just manage to spin out the top gear,( not for long mind!),I reckon I need to lower the ratios a tad to be comfy climbing, so perhaps I should look for a new cassette.

Grldtnr
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Joined: 11 Jun 2020, 7:04pm

Re: Getting the ideal position

Postby Grldtnr » 25 Aug 2020, 4:40pm

Ok, I have spent some time counting cogs, I overestimated my ratios , I have 46 single on the front, with a 13 to 34 on the back, so that's sub 100" in top, with a bottom of 37" in the high range, the Sturmey RF hub reduces or increases the range by a third,, I haven't counted the in between cogs, but a 93" is more than high enough,in fact it's probably about right,as you rarely use yop gear on a touring bike, what is germane tho: is the low of 37", which isn't low enough, but that's before I click down to low range, a third of 37 is roughly 12" , which brings lowest gear to 25" or so, which will just about do, in theory I can't fall off a recumbent trike,tho' I have been unfortunate to roll a recumbent over 3 times in 30 yrs! One was a complete prat fall at low speed on my brand spanking new AZUB!

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[XAP]Bob
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Joined: 26 Sep 2008, 4:12pm

Re: Getting the ideal position

Postby [XAP]Bob » 25 Aug 2020, 5:40pm

Yeah - the SA has no limit on the pre gearing you can fit... I recall that they reckoned that even with a 36 tooth sprocket at the back the chain would snap before the hub gave up....

IOW Pop a double up front and drop the hearing that way...
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Manc33
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Re: Getting the ideal position

Postby Manc33 » 26 Aug 2020, 4:26pm

Jdsk wrote:With the heel on the pedal it's often recommended to allow full extension.


I tried this ages back and the saddle can still go another 5mm-10mm higher. I've got weird proportions though.
When two cyclists get married, they should throw anodized cable crimps instead of confetti.

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Tigerbiten
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Joined: 29 Jun 2009, 6:49am

Re: Getting the ideal position

Postby Tigerbiten » 26 Aug 2020, 4:34pm

Grldtnr wrote:But that's just number crunching, does that equate to real time feel?

Working off the old standard (14/16/18/21/24) 5 speed block, this gave each of your gears a very rough 15% step.
Ticking along at 75 rpm cadence and you want to change gear, up your cadence to ~80 rph, change gear which drops you to ~70 rpm, get back to 75 rpm, easy ........ :D
Much over 15% and you may find it hard to spin a gear enough to get the next one.
The approx 33% step on the old 52/39/30 road triple and 3 speed hubs is two 15% steps. So changing a gear range is always up a ring and down a sprocket or down a ring and up a sprocket for the next usable gear.

The easiest way to drop your gear range is to go double or triple up front as long as you have a derailleur post.
If you do go for multi chainrings, then do you stick to the 33% steps ??
I know that up a ring and down a range would give you an identical gear.
But it does make it simple to keep track of how to get the next gear needed.

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

Grldtnr
Posts: 26
Joined: 11 Jun 2020, 7:04pm

Re: Getting the ideal position

Postby Grldtnr » 26 Aug 2020, 5:04pm

Tigerbiten wrote:
Grldtnr wrote:But that's just number crunching, does that equate to real time feel?

Working off the old standard (14/16/18/21/24) 5 speed block, this gave each of your gears a very rough 15% step.
Ticking along at 75 rpm cadence and you want to change gear, up your cadence to ~80 rph, change gear which drops you to ~70 rpm, get back to 75 rpm, easy ........ :D
Much over 15% and you may find it hard to spin a gear enough to get the next one.
The approx 33% step on the old 52/39/30 road triple and 3 speed hubs is two 15% steps. So changing a gear range is always up a ring and down a sprocket or down a ring and up a sprocket for the next usable gear.

The easiest way to drop your gear range is to go double or triple up front as long as you have a derailleur post.
If you do go for multi chainrings, then do you stick to the 33% steps ??
I know that up a ring and down a range would give you an identical gear.
But it does make it simple to keep track of how to get the next gear needed.

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


I could add a ring, I still have a front derailleur post, but I really don't need a front changer my Optima has a double but no changer, plenty enough slack to grab the chain tube and push the chain by hand.
With the SA hub on the back, I tend to treat it as 9 spd ,with a H/M/ L Range box, click the range ,then up or down the block, it isn't a problem, except climbing hard,out of mechanical sympathy I stop pedaling on down shifts with the hub.
I think I just need to learn my ratios and get used to it, some more time getting miles in.

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Tigerbiten
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Joined: 29 Jun 2009, 6:49am

Re: Getting the ideal position

Postby Tigerbiten » 26 Aug 2020, 6:49pm

Grldtnr wrote:I think I just need to learn my ratios and get used to it, some more time getting miles in.

The way to look at it is like any triple.
Top range:- Downhill.
Mid range:- Flatland.
Low range:- Hill climb.
And as there's roughly 2 gears between each range.
This gives you ........
Top range:- Gears 3 to 11.
Mid range :- Gears 1 to 9.
Low range:- gears -1 to 7.
Adding a (46x0.75=34.5) 34t inner will shift everything down one range giving you roughly ......
Top range:- Gears 1 to 9.
Mid range :- Gears -1 to 7.
Low range:- Gears -3 to 5.
The next chainring down would be a (34x0.75=25.5) 26t if you want to go triple and keep the gears lined up.
The above is very rough and ready guide but it may be close.
Now go out there and find out if shifting up a range and dropping down 2 gears gives you close to the same gear you started with.
As well as finding out how well shifting down a range and climbing up 2 gears lines up.
Depending on the differences between sprockets, some combos will line up almost exactly and others may be well out.
But that's what putting the miles in is all about ..... :lol: