Bigger rear or smaller front.


4 replies to this topic
  • loudarbs

Posted February 07, 2008 - 09:12 AM

#1

I know that they say you lose more mechanical advantage if you go with a smaller sprocket. Keeping the gearing ratio that I want the same, should I go with a smaller front sprocket or a bigger rear sprocket? Also assuming that the rear axle position will stay the same. What's everyones thoughts? Does extra chain wt make a difference?. Does added friction in the chain guides make a difference? Just a couple primer questions.

  • grayracer513

Posted February 07, 2008 - 09:40 AM

#2

Given the same gear ratio, for example, 13/49 vs. 14/52, there is no difference in the two setups from the standpoint of the "leverage" the engine has over the rear wheel at all.

The smaller front sprocket will produce a very small increase in frictional losses within the chain due to the increased rotational angle of the links passing over it, but it's such a small difference that it's negligible from a practical standpoint. I seriously doubt it could be reliably detected on a dyno. A bigger issue is that the sprocket and chain will wear faster over sprockets having 12 or fewer teeth.

In the rear, larger sprockets are necessarily heavier, but here again, what really is the weight difference in two otherwise identical sprockets, one a 49 and the other a 52? Drag at the lower guide can become a factor if the sprocket is so large that the chain must deflect over the back edge of the guide in order to run down to the sprocket. This, however, is more of a problem because of the wear it causes the guide than for the power loss involved.

Chain weight is also not significant between the two setups, since at most, it would require a difference of not more than one link; two pins one way or other out of 114 is less than one percent.

So, IMO, it's functionally immaterial which way one does it, as long as both sprockets are within practical limits as to their size.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • loudarbs

Posted February 07, 2008 - 10:05 AM

#3

Great response Gray except you forgot one important factor, $$ Price $$. Just kidding. Thanks. Great info. Do you think going with the larger rear sprocket and added chain length will affect rotational mass enough that it could be noticed by seat-of-the-pants?

  • grayracer513

Posted February 07, 2008 - 10:08 AM

#4

Machinery designed to measure such things would find it virtually undetectable. Whether you feel it or not (and realistically, you won't be able to) depends on what you convince yourself of. That's why the black feather worked for Dumbo.

  • loudarbs

Posted February 07, 2008 - 10:13 AM

#5

Amazing the power of the mind, I think?:busted:





Related Content

Forums
Photo

YZ450F 03 Sparks driving me crazy by SirAttard


Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 5 replies
Forums
Photo

Snake pit oct 30th by The Anvil


Dirt Bike   Dirt Bike Regional Discussion   California
  • Hot  293 replies
Forums
Photo
Motocross

Thinking about Yamaha 250... by Arctic Pride


Dirt Bike   Special Interest Forums   Pro Racing
  • Hot  491 replies
Reviews

Yamaha YZ450F 2017 by Chris.GVS


Yamaha YZ450F 2017
  • - - - - -
  • 0 reviews
Forums
Photo

100 hrs on 2014 yz450f, shim valves or replace them? by ttr230rider6


Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • Hot  79 replies
 
x

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.