Author Topic: Advice for Great Divide bike set up  (Read 3797 times)

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Offline ghh@me.com

Advice for Great Divide bike set up
« on: October 08, 2017, 01:10:44 pm »
Hi Everyone

Im building up a bike to do an awesome Canada to Mexico trip along the Great Divide route.  Im leaning toward a 1X setup for durability and ease of maintenance en route. 

Id like your advice on set up

Given that the  route will be 80% dirt roads/10% singletrack/10% paved roads - Im leaning towards drop bars and mechanical disk brakes (again due to ease of maintence).

I prefer SRAM shifters on my current road bike, but I am not completely dead set on them.  I am a spinner, not a masher, so I would like to set the bike up with plenty of low end gearing and would be happy to spin out above 25 mph


So - if you could start from scratch - what would you suggest? 

Thanks

Greg

Offline RussSeaton

Re: Advice for Great Divide bike set up
« Reply #1 on: October 08, 2017, 02:49:44 pm »
This is a purely mathematical response.  Assume 10 speed.  Assume 700C wheels.  Just for fun.  I suppose you could go 11 speed too.  And 26 inch wheels too.  But 10 speed and 700C.  11-36 cassette.  Putting the gears into a gear chart with a 34 tooth single chainring, I get about 22 mph top speed with 34x11 gearing and 90 rpm, 83 gear inches.  And I get about 7 mph with low gear of 34x36 and 90 rpm, 25 gear inches.  All the gearing jumps are about 5-6-7 gear inches apart.  Not bad.  Only problem is the high is not too high, not really much of a problem.  And the other problem is the low is not too low really.  25 gear inches isn't anything to brag about for a low gear.  You could run a 32 ring and get a high of 78 and a low of 24 gear inches, 21 and 6.4 mph.  But the low really isn't a lot better and the high is definitely worse.

The problem with running a single chainring is the gearing is compromised.  Either you lose high gears, or lose low gears, or lose the nice progression between gears.  You cannot have all three with a single ring and 10 or 11 or even 12 cogs on back.  SRAM is making a 12 cog cassette now.  The SRAM 12 speed cassette is 10-50.  The SRAM 11 speed cassette is 10-42.  I suppose with a 32 ring and 10-42 cassette, you could get a range of 86 to 20.6 gear inches.  23 to 5.5 mph at 90 rpm.  Good low gearing.  But not a great choice of middle or high gearing and big jumps between gears.  You got to compromise with a single chainring.  With a triple crankset, or even a double crank, you can have nice high gears, nice low gears, AND nice jumps between gears.  You can have it all with a double or triple crank, you can't with a single ring.  You give up good gearing range or progression for the benefit of maintenance, reliability, ease of shifting.
« Last Edit: October 08, 2017, 08:06:26 pm by RussSeaton »

Offline Iowagriz

Re: Advice for Great Divide bike set up
« Reply #2 on: October 08, 2017, 04:07:51 pm »
I rode 6 days from Banff to Lincoln this past late June.  29er, hardtail, 2.3 tires and rigid fork.  1x10 gearing, 32T upfront, 11/36 rear. Walked a fair amount, but that was also the plan to keep moving for 12hrs a day. This was all in prep to do the entire route at some point in the future.  Now I'll upgrade to 11speed or 12/Eagle.  Probably keep the 32 up front, but gain a lower gear in the rear.  Add some additional fitness and I'll be fine.

But, everyone is different.  FWIW - I'm 52, former cat 1 MTB racer, don't mind mashing gears if needed for hills, but prefer to spin as much as possible.  Total gear weight with food and water was probably close to 60lbs.

It is a great route, enjoy the trip.

Offline ghh@me.com

Re: Advice for Great Divide bike set up
« Reply #3 on: October 08, 2017, 08:12:17 pm »
Thanks for the advice so far. 

Regarding the greater jumps in 1X gearing - understood and appreciate and probably still more interested in the reliability of 1X. 

And I guess I should have said a bit about me - Im 54 years old.  I rode the TransAm route last summer with a super light road bike with RV support in 7 weeks.  Average daily distance toward the end of the ride was about 115-125 miles per day. 

Im planning on doing this ride with a combination of lightweight bikepacking combined with meeting my better half at convenient locations along the way.


Lastly - I think the Eagle 12 cog cassettes are the way to go - (10 to 50) and then fine tune it with chainring choice.  Since I prefer drop bars, I d probably have to mount the eagle shifter near the stem on the top of the bars and use regular (non shifter) brake levers - eh?