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Discussion Starter · #1 · (Edited)
I am doing the Horribly Hilly 200K ride and I am wanting to squeeze the most out of my Madone 5.2 SL gear ratios. I am currently running a 50-34 Ultegra SL Compact with a 12-25 cassette. This set up puts me at the total capacity for my 10 speed Ultegra rear derailleur which is listed at 29. According to what I have read you take the difference from the largest and smallest chain ring (50-34) and add it to the difference of the largest and smallest cog (12-25). (50-34) + (25-12) =29.

Can I cheat the total capacity spec and replace my 12-25 with a SRAM 12-26 which will put me only 1 number above (30 vs 29) the total capacity? How forgiving is this spec? I will still be ok with max capacity which is listed at 27t for my derailleur.

What will the results be? I am looking for the most bang for my buck without switching derailleurs. Can an experienced mechanic make this work?
 

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info...

The smallest increment of chain that can be changed is 1 inch, which equivalent to 4 teeth. Adding one tooth of wrap is unjlikely to cause a problem, but the chain must be set to the longest length that will avoid hanging loose or rubbing on the RD when you're in the 34/13. If the chain length was set an inch shorter, it could cause a problem in the 50/26.

Chainstay length varies and those with the perfect chainstay length can gain up to 2T of wrap over another bike with the same gearing setup.
 

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I put on a 12/27 with my 50/34 and the chain was slack while crossed. If you think you'll never, ever be crossed then you can get away with it. I ride Brevets and doubles and sometimes in the dark when your head is fuzzy you end up crossed when you normally wouldn't.

...so i put on a triple rear derailler, and there it stays. I just didn't like the chain tension while crossed in 50/27 and 34/12.

I think the length of your chainstay has much to do with it. How tall are you?
 

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short answer...yes you can, but if you ever do a big/big combo you could blow your drivetrain up.
 

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How much advantage would going up one tooth like that be?

Basically Im asking if specific training would be more effective. Ride upgrades dont buy upgrades and all that crap. Make yourself a better cyclist and spend less money.

Im not saying that you are doing anything wrong if you do buy it. Maybe that would be the best/easiest/practicle thing?

Hence, How much advantage would going up one tooth like that be?
 

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I agree with logansites, going from a 12-25 to a 12-26 will make very, very little difference. going to a 12-27 will give you one lower gear, and yes, your set up will handle that just fine. Also consider a SRAM 11-28 cassette, though with a short cage rear derailleur, you may be pushing the capacity a bit, but it should work, just watch your big to big and small to small combos, and make sure your chain is long enough to handle the 28.
 

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Discussion Starter · #11 ·
Thanks for all the advice, I now agree that going from a 12-25 to a 12-26 is not going to get me much. Based on the advice in this thread and after calling my mechanic I am going with the 12-27.

Also the point made by logansites about the training is well taken. I have (as much as I can in northern Illinois) sought out the worst hills to do repeats on. The problem is there is nothing in this state the even compares to the Horribly Hilly Hundreds (HHH). I rode 55 mi on the course a few weeks ago and that is when I decided to make a change. I am going to do a 80 mi training ride on the course tomorrow. This is a 3 hour drive from my home so yeah you can see that I am not trying to buy fitness in lieu of training.

The HHH is a 200 K ride. We are not talking mountains here ( longest climb about 900 ft) but the hills have grades that can really inflict some pain. Depending on what you read there will be about 12000 feet of vertical in this with no opportunity to get any rhythm. Also being in a colder climate means most riders will not be anywhere near peak fitness in June. One experienced rider who did the HHH and the assault on mount Mitchell said the HHH is worse.

Thanks again for all the help
 

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That course looks pretty tough. Sometimes you have to match your equipment accordingly. I know that when I go visit my friend in VA or my dad in PA im usually wishing for a couple more gears!

Have fun man! I wish I werent so far away from that one.
 

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IME you can push the limits pretty far... I was able to set up a friend's bike with an 11-34 cassette on an old short cage 105 derailleur, 42/52 up front, which is way beyond spec.

I had to tweak everything perfectly including the position of the wheel in the dropouts, b-screw adjustment and chain length. It even worked in the big-big combo, as I wasn't going to risk that she would shift into it by mistake.

However, it sounds like your bike is at a shop. They should be able to determine what will work or not, I would think.

Regards,
Anthony
 

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Your gearing is likely fine as is. The trick to these type of rides is to stay within yourself . If you don't hammer on the flats and get into the type of fun but silly paceline that's more ideal for a 40 mile ride you won't have to worry about the climbs. Anyway, sounds like fun.
 

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Discussion Starter · #15 ·
Thanks for all the good advice. Based on my my current level of fitness going to a 34X27 was just the ticket as I tested it out on 80 mi of the course last sat.. Heading back this weekend for 96 miles of fun!
 
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