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Trek 7.5 Hybrid to Hill Climber conversion

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Trek 7.5 Hybrid to Hill Climber conversion

Old 08-30-20, 06:37 PM
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ronmann
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Trek 7.5 Hybrid to Hill Climber conversion

Hi,

I have a 2012 Trek 7.5 with a compact double crank. I want to change the gearing, either the crankset or cassette to use this bike for very steep hill climbs. I'm wondering if there is any changes I can make without changing the derailleurs to get a better granny gear. I tried my LBS but they wouldn't give me any advice. I've found 11-40T cassettes and sub-compact double cranks online but I'm not sure if these are compatible. Any advice appreciated, Thanks!

Specs:Shifters Shimano R440, 9-speed trigger

Front derailleur Shimano Sora

Rear derailleur Shimano Deore

Crank FSA Vero, 50/34 compact road gearing

Cassette SRAM PG-950 11-34, 9 speed
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Old 08-30-20, 07:03 PM
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Without knowing which "Deore" RDER you have, one doesn't know the max cog size or amount of chain wrap available.
It might sound "brutal", but it sounds like you bought one step to good of a bike.
The 7.4 lists a 3X9 which would likely fill your needs.
I'm uncertain of which "new" generation of 9 speed RDER's that handle the larger cogs AND Double Rings AND is compatible with your current shifter.
Hopefully one of the knowledgeable ones will step in first.
to add: Your right shifter is a flat bar "road" shifter, shifting a "road" FDER to move the chain on a "road" crank.
IF you wanted a "mountain" triple, you'd also have to change the shifter & FDER to make sure everything functioned right.

My hybrid has been changed from an 8 speed 11-32 / 28-38-48 to a 9 speed 13-25 / 22-32-44. (44 has actually been changed to a 36T, but that's a different episode)

Last edited by Bill Kapaun; 08-30-20 at 07:12 PM.
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Old 08-30-20, 08:13 PM
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small gear on the crank big gear on the back hub.. you don't go far with every crank rotation , but that what a granny gear is..
50-40-24 is my touring bike chainset cassettes are huge now due to the one by craze..
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Old 08-30-20, 09:08 PM
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Thanks for all the info. I agree this isn't the right bike, I moved to an area with the steepest hills, and now I have a goal to ride up them. I'm finding there's a lot of options for sub-compact double cranks. I don't know all the things to check for compatibility. Looking at my current crank, FSA Vero, 50/34, is there a compatible crank with 30 or less teeth that will work?
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Old 08-30-20, 11:47 PM
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Run your 34t inner ring only. Get a Wolf Tooth Road Link. Get a Sunrace 11-40 9 speed cassette, not sure if there is an 11-42. Get new chain. Put it all together.

The 34t will give you a 3:1 ratio.

If the 34:40 (42) isn’t low enough, it will get more expensive with a different crank.

John
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Old 09-01-20, 02:57 PM
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Thanks for the idea John, this looks like the simplest solution. Another idea I found is to install a triple and removed the largest chainring so you’re left with a super compact double. I’m not sure if I can keep my derailleur if I do this?
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Old 09-01-20, 03:29 PM
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Originally Posted by ronmann
Thanks for the idea John, this looks like the simplest solution. Another idea I found is to install a triple and removed the largest chainring so you’re left with a super compact double. I’m not sure if I can keep my derailleur if I do this?
I would keep your cassette or get a 11-40 or 11-36 if research shows that your R/DR will reach a cog that large and try your idea of using a triples crankset to achieve "Alpine Gearing" (read Sheldon Brown, big proponent of this.)

That sounds confusing but my overall idea is that it will be cheaper and more effective to swap out your crank than to switch out cassette and derailleur, but if your derailleur has the capacity, then go ahead and mess with the cassette too.

Keep your 34 in the middle position (you'll need new, shorter bolts, and get a 24T small chainring and away you go! You may have to shorten your chain a bit. That will give you the poor man's version of Rivendell's Silver low/low crank.

You're not crazy, the stock gearing on that bike is ridiculous for anyone looking to climb anything.

Last edited by davei1980; 09-01-20 at 03:41 PM.
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Old 09-01-20, 06:24 PM
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The Deore rear derailleurs from 2012 were still working fine on MTBs with triple chainraings. I don't know the exact chain wrap capacity, but you're probably good with any changes you make keeping the crank as a double. I'd look at 2x cranks with smaller chainrings. MTB and even GRX, where 48-31 is common. You also need to look and see how your front derailleur is positioned on the braze on tab. If you drop the size of your chainrings, you'll also need to drop the front derailleur, so make sure there's space on your FD tab to do so, cause you want the bottom of the derailleur cage close (less than 2mm) from the big chainring.
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Old 09-06-20, 02:06 PM
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I ended up taking a crank off an old mountain bike with 22/32/42 rings. I got the FD working with the 2 inner rings, I didn't replace the chain and it is working great. I have an insane granny gear of 22 on the crank and 34 on the cassette. I researched the hill grade from my house to the beach and it is 25%, very steep. I know most would say this gearing isn't necessary but its helping work towards my goal of climbing this hill without breaks.
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Old 09-06-20, 03:30 PM
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Originally Posted by ronmann
........ I know most would say this gearing isn't necessary but its helping work towards my goal of climbing this hill without breaks.
You use the gears YOU need, not what people who don't know a thing about you tell you to use.
Some days I'm using a 22/27 to haul a load of groceries up an approx 1.5% slope.
Old age, bad knees, COPD & fatigue issues from my immuno-therapy.
Ya do what ya gotta do-
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Old 10-17-20, 12:09 PM
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Originally Posted by 70sSanO
Run your 34t inner ring only. Get a Wolf Tooth Road Link. Get a Sunrace 11-40 9 speed cassette, not sure if there is an 11-42. Get new chain. Put it all together.

The 34t will give you a 3:1 ratio.

If the 34:40 (42) isn’t low enough, it will get more expensive with a different crank.

John
John, would you explain how you calculated the gear ratio of 3:1? (Math isn't my strong suit, and I really don't get it.)
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Old 10-17-20, 02:20 PM
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If you have an 11t 1st position cog, you are turning it, and the wheel, about 3 times for every revolution of the crank with a 34t. Three times 11 = 33 which is close enough, at least for me, to 34 to get an idea of the top end.

There are gear/speed calculators that will give you an exact ratio and a speed that is based on you tire size cadence.

John
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