Bike Forums

Bike Forums (https://www.bikeforums.net/forum.php)
-   Bicycle Mechanics (https://www.bikeforums.net/bicycle-mechanics/)
-   -   Shimano Front Chain Ring Option (Larger?) (https://www.bikeforums.net/bicycle-mechanics/1230076-shimano-front-chain-ring-option-larger.html)

Warbird21 05-09-21 07:09 AM

Shimano Front Chain Ring Option (Larger?)
 
I purchased a new Salsa Warbird with the Tiagra group last month. It has a 2x10 gearset with 34/46 front chain rings. I ride 80% on the road, some on the nearby C&O canal. I find myself on the smallest rear ring 80% of the time and rarely past 8-9-10 range. On even modest downhills, I seem to run out of pedal and feel I could ride faster. I've never swapped a chain ring before, so this is uncharted territory.
I have the FC-R460 chain set.

It looks like Shimano offers a 48 gear front ring in that group. Is that something that would work for me? Would my current chain work? Any advice or tips are appreciated, this is completely new to me.

smashndash 05-09-21 11:48 PM

If you're in 8-9-10 80% of the time, maybe you need something bigger than a 48T top end. Or maybe you just need to shift to the big ring more often? Or are you saying that you're in your big ring and little cogs 80% of the time?

Step 1 is to figure out your spinout cadence. How fast can you spin downhill before you can't put out useful power? At what speed do you hit that cadence?

Step 2: Figure out what you want your top speed to be. For example, do you have a good reason to be able to pedal past 40mph?

Step 3: Use bikecalc.com to figure out what gear ratio allows you to hit your target speed.

Step 4: Get the chainrings (or even new cranks?) you need. Any 10 speed 110mm 5 bolt ring should work. You can try to just get a bigger big ring. Your front mech probably won't be able to handle it. Thus, you'll need a bigger little ring. If you need easy gears, you'll need a bigger cassette. If your rear mech is a short cage, you'll need a new rear mech. And you'll also need a new chain to accommodate the larger gears. And you'll need to readjust the front mech.

Alternatively: get better at spinning. I can put down useful power well beyond 45mph if I want to using a 50:11, which is pretty standard gearing. It's usually far more beneficial to tuck than to continue to pedal at those speeds anyway.

https://cimg7.ibsrv.net/gimg/bikefor...e08a145e1.jpeg

With a 46:11, at 130rpm, you're doing 43mph rather than 46.5mph. Not a huge difference IMO.

Those are your options.

Warbird21 05-10-21 05:36 AM

Thanks@smashndash!

"you're in your big ring and little cogs 80% of the time?"

Yes - I've only need to use the small front ring 1x.

Going down a mild grade, I can't get past 30 mph, no matter how fast I pedal. Speed measured by an older Garmin Edge 500 (a cast-off my brother gave me), but no cadence monitor.

My brother was over last night, he had not seen the new Salsa. He said I wouldn't notice any difference with the 48 tooth and should only try the 50. He said I would also need a new chain, and the whole process could be going down a bit of a rabbit-hole.

andrewclaus 05-10-21 06:20 AM

My 36/50 works fine for me. I live at the border of plains and mountains. I use them both. When I ride east, it's a big ring day. When I ride west, it's a small ring day. I spent a winter in Florida last year and never used the small ring. But it's low enough for me for the big climbs out here. (11-34 rear cassette)

The deciding factor will be your rear derailleur (RD). Try to find its chain wrap specs. Or do this test: Shift to small-small combination and the RD should be fully retracted, with the pulleys almost touching the chain. Then shift to large-large, and the RD cage (line between pulley axes) should be extended at a max 45 degree angle to the ground.

Every two teeth added on a gear will need one more inch of chain.

JohnDThompson 05-10-21 06:44 AM


Originally Posted by Warbird21 (Post 22052675)
My brother was over last night, he had not seen the new Salsa. He said I wouldn't notice any difference with the 48 tooth and should only try the 50. He said I would also need a new chain, and the whole process could be going down a bit of a rabbit-hole.

Yes, a larger ring will likely need a longer chain. And a new chain will likely need a new rear cassette, as chains and cassettes wear together, such that a new chain will not mesh securely under load with a worn cassette. There's also a possibility that the larger ring/longer chain may exceed the wrap capacity of your rear derailleur, requiring a longer cage derailleur.

Andrew R Stewart 05-10-21 07:17 AM

The time tested way to go faster is to pedal faster:) That and understand that gravel bikes, and their gearing, are not about max paved road down hill speed. I might suggest you are using the wrong tool for 80% or your riding. Andy

DaveSSS 05-10-21 07:32 AM


Originally Posted by andrewclaus (Post 22052704)
My 36/50 works fine for me. I live at the border of plains and mountains. I use them both. When I ride east, it's a big ring day. When I ride west, it's a small ring day. I spent a winter in Florida last year and never used the small ring. But it's low enough for me for the big climbs out here. (11-34 rear cassette)

The deciding factor will be your rear derailleur (RD). Try to find its chain wrap specs. Or do this test: Shift to small-small combination and the RD should be fully retracted, with the pulleys almost touching the chain. Then shift to large-large, and the RD cage (line between pulley axes) should be extended at a max 45 degree angle to the ground.

Every two teeth added on a gear will need one more inch of chain.

It takes 4T to use 1 inch of chain, but since 2T requires 1/2 inch and changes can only be made in 1 inch increments, that could still require another inch of chain. The chain length formula is relatively simple. Add the big/big and divide by 4. Multiply the chain stay length times 2 and add to the first amount. Then add 1 more inch for going through the RD. If the total ends in .5 or greater round up.

https://www.parktool.com/blog/repair...-length-sizing

Warbird21 05-11-21 04:53 AM

Wow,I appreciate all the replies and input. I suspected this might be pretty involved (replacing the chain, derailleur and/or rear cassette = pretty involved, by my experience) I'll complete this season of riding and see if I still feel the need to change. I guess that I was used to my Cannondale road bike from 30 years ago.

I've learned quite about already from this forum, thanks again for helping to educate me!

Warbird21 05-12-21 06:06 PM

Perhaps I need to learn and adapt! Today, I beat my max speed, down a modest grade hill by nearly two mph - by getting on the drops.

Iride01 05-13-21 08:24 AM


Originally Posted by Warbird21 (Post 22056935)
Perhaps I need to learn and adapt! Today, I beat my max speed, down a modest grade hill by nearly two mph - by getting on the drops.

I go faster up hills when I'm in the drops. I wonder why? duh!

Sorry if that sounds rude, I think you have to agree that has to be a duh!

Aerodynamics if you need a hint.


All times are GMT -6. The time now is 09:35 AM.


Copyright 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.