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Gear ratio's

Posted: Fri Sep 14, 2012 4:33 pm
by rog on a bike
Hi All Has anybody got the formula for working out gear ratios. I pick up the Vivente WR on Tuesday next :D and it is my intention to tow a trailer with it.
The Vivente thread has put the wind up me some what in relation to the standard ratios and sore knees at the end of the day?
I suspect now is the time if changes need to be made :?:
Cheers Rog

Re: Gear ratio's

Posted: Fri Sep 14, 2012 4:38 pm
by Carriage
Do you mean selecting a suitable ratio or working out what ratio a given drivetrain gives?

Re: Gear ratio's

Posted: Fri Sep 14, 2012 5:12 pm
by Tim
Gear ratio calculator;

http://home.earthlink.net/~mike.sherman/shift.html

You've picked yourself a nice bike. After commuting for around six months and a few loaded (approx. 20kg) overnight and trial runs I'd suggest a lower gearing ratio might be better than the stock standard. I've just ordered a Sugino 24t chainring and an 11-34 cassette from Loose Screws Bicycle Small Parts in the U.S;

http://www.loosescrews.com/index.cgi?c=Crank/Chainring&sc=74mm%20BCD,%205%20bolt&id=229901821519

The rings are out of stock at the moment but due next week. I was going to order an HG61 12-36 cassette and a steel chainring from another supplier but wasn't sure of their compatibility with the Vivente running gear so stuck with a configuration I know (hope) works.

Re: Gear ratio's

Posted: Fri Sep 14, 2012 9:27 pm
by rog on a bike
Thanks Guys.
What I'm trying to determin is. If a cassette change to 11/34 will do what I require? Or do I need to do a chain ring change to say? 24 or 22 with the std. cassette. (That being a 32)
I'm riding an "Epic" at present with a 44/32/22 by 11/34 x 9 speed , the VWR has a 46/36/26 by 11/32 x 9 speed. I don't believe I need to go as low as 22 by 34 (I walk faster than that)
But I suspect that I may need to be lower than Epic 32main/34cassette (which is bottom of the mid ring). Any thoughts :?:
P.S. The planned ride is through Cooma, Jyndabine, Suggan Buggan, Orbost and on to the Great Ocean Road via Sorrento to Port Fairy? Towing a Bents single wheel trailer and rear panniers?
Cheers Rog

Re: Gear ratio's

Posted: Fri Sep 14, 2012 9:39 pm
by RonK
You definitely need a smaller chainring.
With 28 x 700c tyres:
26 x 32 = 21.7 gear inches
26 x 34 = 20.4 gear inches
24 x 34 = 18.8 gear inches
22 x 34 = 17.3 gear inches

This is quite a significant variation.

The best choice is a 22T chainring and an 11-32 cassette, this yields 18.4 gear inches and closer ratios, however the simplest solution is to buy a 24T Stronglight chainring from Dotbike and use a 11-34 cassette.

PS - if you have an iPhone there is a great little app called Bike Gears.

Re: Gear ratio's

Posted: Fri Sep 14, 2012 10:15 pm
by rog on a bike
Thanks Ronk.
I'll ride it standard for a while. (I've got a couple of months before I leave)
I also thought that a chain ring change was required and stay with the std cassette.
I do have an iphone, so I'll check that app out.
Cheers Rog

Re: Gear ratio's

Posted: Fri Sep 14, 2012 10:22 pm
by Tim
I dithered around for ages trying to decide what to buy and from where. Sorry Ron, I should have taken your advise and bought the steel ring and cassette from Dotbike. I just had some (probably irrational) doubt it would fit so chose the Sugino ring to go with the Sugino crank.
Anyway, I'll report back when it's fitted and see if my combo provides a noticeably lower gearing ratio.
ps. I think 24t is the smallest ring that will fit on a 74BCD crank.

Re: Gear ratio's

Posted: Fri Sep 14, 2012 10:34 pm
by Tim
....Jyndabine, Suggan Buggan, Orbost....


I made a trip up that way about a month ago. I come from that area, near Benambra, and only moved down to the coast a few years ago.
There are some mighty long and steep dirt roads in and out of the Snowy River valley. Towing a trailer I'd reckon you'll need as lower gearing as can possibly be fitted to the VWR.
Maybe even consider mountain bike cranks and smaller than 24t granny gear. It is really rugged country.

Re: Gear ratio's

Posted: Sat Sep 15, 2012 9:04 am
by rog on a bike
Good Point Tim!
I plan to leave the coast at Nowra then to Braidwood and on to Cooma via snowball. If the going gets a bit untidy on the Braidwood/Old cooma rd I may very well opt for the Cooma /Cann River route via the Monaro Hwy.
Rons idea appears to be on the mark with a 24t chain ring and a bottom end 34 cassette. (Thanks ron)
Has any body fitted a 22t chain ring to a VWR? If so what brand and what problems did you have?
Again. Thanks All.
Rog

Re: Gear ratio's

Posted: Sun Sep 16, 2012 5:17 pm
by RonK
rog on a bike wrote:Has any body fitted a 22t chain ring to a VWR?

No, 24T is the smallest you can fit to your 74 BCD chainset. An MTB chainset is needed to go smaller.

Re: Gear ratio's

Posted: Sun Sep 16, 2012 7:32 pm
by rog on a bike
Thanks Gents.
Very much appreciated!
Cheers Rog

Re: Gear ratio's

Posted: Mon Sep 17, 2012 1:18 pm
by rifraf
Hi Rog
Be aware you may end up needing a longer derailleur and chain for cassette conversions
utilising more teeth (lower gears)
I'm not familiar with your bike so dont know for sure.
Sheldon has a little page here that might be helpful with regards ratios and gear inches.
http://sheldonbrown.com/gears/

For loaded trailer work, Ronks right on the money, you'll need low gearing.
I'm running 16.7 inches and still do lots of pushing up rises and hills. :shock:

Re: Gear ratio's

Posted: Tue Sep 18, 2012 8:55 pm
by rog on a bike
rifraf. Thank you.
Sheldons site is a great sorce of information on all things bicycle.
I pick the bike up tomorrow :D so I suspect I'll get more of an insight as to what will be required very soon.
What are you riding and what weights are you pulling at 16.7 gear inches :?:
My Epic at 22/34 produces a ratio of .65. I'm pretty sure that this is not as low as 16.7 :? (and I can climb a cliff at 22/34)
Thanks again and I will check out the derailleur/chain length issue.
Cheers Rog

Re: Gear ratio's

Posted: Wed Sep 19, 2012 1:23 am
by rifraf
rog on a bike wrote:rifraf. Thank you.
Sheldons site is a great sorce of information on all things bicycle.
I pick the bike up tomorrow :D so I suspect I'll get more of an insight as to what will be required very soon.
What are you riding and what weights are you pulling at 16.7 gear inches :?:
My Epic at 22/34 produces a ratio of .65. I'm pretty sure that this is not as low as 16.7 :? (and I can climb a cliff at 22/34)
Thanks again and I will check out the derailleur/chain length issue.
Cheers Rog


An old Moulton APB Landrover (17 years old now approx) :)
Image

Re: Gear ratio's

Posted: Sun Sep 23, 2012 10:53 pm
by rog on a bike
Hi All
Just thought I'd drop back and give a "sitrep" on the new machine. Picked it up last Wednesday in Fyshwick (the bride needed to see floriade) but did not get on it in any form of anger untill Saturday. I put together a 53k ride ( that involved the purchase and fitting of a set of rear panniers) over a couple of rises in our area. It is important to note that everything that is wrong with the epic is being transfered to the Vivente :lol: .
Sunday, 75k was added to the odo with the trailor loaded to 50% (no water or food) over the same local hills but included a south to north run on the Fernleigh track. (Belmont to Adamstown) Then back to Western Lake Maquarrie. With standard gearing I only had to walk 2 hills.
The vivente is everything the epic is not. comparativly the VWR is hard (bone jaring) The epic is a dualie, really tight in the head where as the epic is light, the VWR is much heavier at around 50 kgs loaded and with all of that it is an absolute pleasure to ride. :D :D
Two small issues are the seat wants to decend (about 5 mm every hour) but I reckon I've got that covered by wiping the excess grease from the seat pillar and useing a good quallity set of allen keys to neck it off properly :P
The other has nothing to do with Vivente. I'm finding it difficult to access info (Good and simple) on the jetblack 22 cycle computer I purchased for the new stead! The manual consists of one small piece of paper outlining 22 functions? It then does nothing to tell you how to access these functions.
Look it may very well be me :oops: As i said all that was wrong with the Epic has been transfered to the Vivente.
Ron and rifraf I'm ordering the 11/34 tomorrow! I must admit I didn't think it was all that bad.
Thanks for your help guys.
Cheers Rog

Re: Gear ratio's

Posted: Mon Sep 24, 2012 12:16 am
by rifraf
Hi Rog
what do you think about derailleur compatibility?
Do you have the GS(medium) or SGS(long cage) version of the Shimano rear derailleur?
I got a feeling your going to need the SGS with that combo front and rear.
I only got away with the 11-32T cassette because I run only a single front chainring (I was told).
Love to hear how you got on.
Keep us updated. :)

Re: Gear ratio's

Posted: Mon Sep 24, 2012 8:26 am
by rog on a bike
rifraf.
Thanks! My lbs seems to think it will be alright :?:
I suspect it will be a "suck it and see" exercise?
I've got another issue and that is the trailer is dislodging the LHS pannier, (Panniers are hard backed) So I've got some work to do there :roll:
Not to worry! All part of the thrill of cycle touring :P
Cheers Rog

Re: Gear ratio's

Posted: Mon Sep 24, 2012 11:42 am
by rifraf
HI Rog,
I was rereading Andrews LHT review on his Aushiker site:
http://aushiker.com/surly-long-haul-trucker/
and notice he has the long cage derailleur.
"The front derailleur that came on my Surly Long Haul Trucker is a Shimano Tiagra FD-4403 triple and the rear derailleur is a Shimano Deore XT RD-M761 SGS long cage."
If yours is the same spec you should have no worries.
Remember to check your chain length after adding gear teeth to your drive train.
Sheldon Brown tells you how if your not sure or have forgotten.

Re: Gear ratio's

Posted: Mon Sep 24, 2012 1:05 pm
by RonK
According to the published specification on the Vivente web site, the current model VWR uses a rear derailleur from the Deore LX groupset. This is now designated as trekking groupset but was formerly designated as an MTB groupset, and I believe it will almost certainly accommodate an 11-36t cassette.

A 24x36t combination will yield 17.8 gear inches. In my experience it should not be necessary to gear this low. 24x34t yields 18.8

As mentioned previously my preference is for 11-32 with a 22t chainring, which yields 18.4 gear inches.

Re: Gear ratio's

Posted: Mon Sep 24, 2012 2:01 pm
by rifraf
RonK wrote:A 24x36t combination will yield 17.8 gear inches. In my experience it should not be necessary to gear this low. 24x34t yields 18.8

I think mines 16.7 from memory according to Sheldons calculator.
When the trailer has a good load on I could go for a smidgeon lower if it was possible.
I've lost most of my tour fitness now having been hiding indoors for Perths winter but even at the last
leg of my trip, I still found myself pushing up long rises and/or most hills.
I couldn't go any lower without replacing my cranks which after coughing up for a new dura-ace bottom bracket
as a spare to take on the tour, I dont want the expense of doing.
Or the trauma of trying to work out the right bottom bracket length for correct chainline.
Twas a handful when there was no info available from anyone who had travelled the path before.
I got the smallest ring that would fit my FC7701 cranks which I think was a 39T.
When I finished my tour and could unhook the trailer I was amazed at the gears I could push.
I'd previously never used the top range except when going downhill but now/then was able to utilise
the three and sometimes four largest cassette rings whilst in top in the IGH.
Theres hills around me though where I still use the lowest gears unladen.

Re: Gear ratio's

Posted: Mon Sep 24, 2012 3:55 pm
by RonK
rifraf wrote:I think mines 16.7 from memory according to Sheldons calculator...

I got the smallest ring that would fit my FC7701 cranks which I think was a 39T.

39x36t with 20" x1.5" tyres would yield 21.1 gearinches. Not really low enough for semi-trailer drivers in my book. :lol: :lol: :lol:

Re: Gear ratio's

Posted: Mon Sep 24, 2012 4:09 pm
by rifraf
RonK wrote:
rifraf wrote:I think mines 16.7 from memory according to Sheldons calculator...

I got the smallest ring that would fit my FC7701 cranks which I think was a 39T.

39x36t with 20" x1.5" tyres would yield 21.1 gearinches. Not really low enough for semi-trailer drivers in my book. :lol: :lol: :lol:

Dont forget the 3 speed IGH Ron.
Sheldon gives me 16.5 to 81.6inches after a quick check.
If I've looked at the correct manual, first gear (low) is 73% , second (100% direct drive or 1:1) and third is 136%

Re: Gear ratio's

Posted: Mon Sep 24, 2012 5:24 pm
by Baalzamon
Well I'm looking at getting a rohloff with a 13 tooth sprocket with a triple on the front. 60/48/34 setup. Don't forget it's recumbent and to use a 34 on the front I need a 13 tooth sprocket

Re: Gear ratio's

Posted: Mon Sep 24, 2012 6:41 pm
by rifraf
Baalzamon wrote:Well I'm looking at getting a rohloff with a 13 tooth sprocket with a triple on the front. 60/48/34 setup. Don't forget it's recumbent and to use a 34 on the front I need a 13 tooth sprocket

I know you've heard of some failures, but have you considered a Sram dual drive?
A lot of bents use and love em.
With a nine speed cassette you get a wider range (576%) than a Rohloff for a fraction of the cost with lighter weight.
Some serious Moulton riders I've read about have travelled the world on them with no probs.
Disk brake version available.
You know mines just hauled a trailer and my fat butt from Mudgee to Adelaide to Perth
with no problems.
Choice of 7,8,9 or 10 speed cassettes and three different shifter possibilities.
Two trigger shifters, two gripshift shifters or a one handed trigger/gripshift combo.
Seven speed cassette has a range of 509%
Eight speed cassette has a range of 542%
At the edge of their weight limit with a bent I imagine as sram recommends no tandem use.
Max recommended ratios are 33T front ring and 11-34T cassette but we all "suspect" thats just to cover their butt
so they dont have to pay for warrantys.
Not hard to find on the net examples of people riding way outside these limits.
For a non disk version count on around $152Au.
http://www.ebay.com.au/itm/SRAM-Dual-Dr ... 5d34dc0049

Re: Gear ratio's

Posted: Mon Sep 24, 2012 7:00 pm
by Baalzamon
One when you will see my trike you will see what I want to get rid of the derailleur. It is too close to the ground and a stick/rock can easily snag and bend/break it
Two John Lewis has had to fix up a few Sram Dual Drives
Three If I'm running a double or triple upfront then I will have even wider range.