gearing?


5 replies to this topic
  • stroker yz426

Posted February 05, 2008 - 12:04 PM

#1

since this is the first stroker that im putting back into a bike, the manufacturer recomends that i gear down to make it more friendly anyway i have a 14 front and 49 rear the ratio is 3.50 this isnt that bad, should i more to a 15 front and a 47 or 48 rear or should i keep the 14 front and move to a 47 or 48 rear , this would give me the benefits or a 3.36 or 3.42 ratios, does it really make that much difference because these are soo close to stock setting?
what benefits do you get from switching front sprockets around i can get a 12-15 range in fronts, but which is more cost effective?
having a lil trouble with this one my brain must be turned off this week
thanks for all the input:worthy:

  • grayracer513

Posted February 05, 2008 - 12:23 PM

#2

"Gearing down" means to go to a "lower" ratio, which, counter-intuitively, is higher numerically. So by going from a 14/49 to a 15/48, you would be going "higher", not "lower".

This comes from the common parlance in which "low gear" produces less speed than "high gear". In the lower gears, the input RPM is higher than the output RPM, so the speed is "low", even though the ratio is numerically high.

What are you trying to do with your 426? Tight trails? MX?

  • stroker yz426

Posted February 05, 2008 - 12:34 PM

#3

true i understand the difference in going high or low, but should i change the counter sprocket or should i go bigger i think theres enough room? or should i keep the stock number upfront and switch out the rear ? i do all of the above riding but i want it to be the best all around for now im a heavy tall rider im 6'3'' and 240 so i need a lil extra ummph to push me around

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  • grayracer513

Posted February 05, 2008 - 02:18 PM

#4

You can do it either way, but there are practical limits. 13 is the smallest I recommend at the front, because any smaller and the sprocket and chain wear is accelerated significantly. At the rear, 52-53 is the largest practical size that can be run without modifying the lower guide to accept it, and 47 is the smallest most manufacturers offer without a custom order. Smaller than that is not practical for off-road because of the increase in swing arm drag.

You say that you understand gearing. However, the following statement...:

...the manufacturer recomends that i gear down to make it more friendly... I have a 14 front and 49 rear the ratio is 3.50 this isnt that bad, should i (move) to a 15 front and a 47 or 48 rear or should i keep the 14 front and move to a 47 or 48 rear , ...

...leads the reader to think otherwise, since either the 15/47(48) or 14/47(48) combos would be gearing up, not down.

Your stock gearing was 14/49. A lot of people do run 426's with 14/50 or 14/51 combos, but it just depends on what works best for you. What you might do is to set up a 14/48 or a 15/51 with the axle forward some, and then be able to change to either a 13/48 or a 14/51 for tighter trail areas. You could possibly do this as well by leaving the 14 at the front and buying both a 48 and a 51 tooth rear and trade them back and forth. One swap isn't really that much easier than the other, IMO, but of course, front sprockets cost less.

  • stroker yz426

Posted February 07, 2008 - 11:34 AM

#5

Quote:
You say that you understand gearing. However, the following statement...:


Quote:
Originally Posted by stroker yz426
...the manufacturer recomends that i gear down to make it more friendly... I have a 14 front and 49 rear the ratio is 3.50 this isnt that bad, should i (move) to a 15 front and a 47 or 48 rear or should i keep the 14 front and move to a 47 or 48 rear , ...

...leads the reader to think otherwise, since either the 15/47(48) or 14/47(48) combos would be gearing up, not down.

ok so i made it sound the oposite, however i do understand, but with as much math runnin a round in my head from work and such sometimes i dont slow down to explain better.....it makes sense in my head but sometime it doesnt to others as in this case, when i said down, i meant not so aggressive(high numerically), in which to mellow the bike out (low numerically), sometimes i cross the auto enthusist lingo with everything else and it comes out wrong, anyway back to the point, i have to buy a new chain and sprockets, and was wondering if i should change both sprockets from the factory amount, but since it is more complicated and confusing to some, i will keep the front the same, and change the rear to a smaller, do you really feel that the difference of a tooth is a big impact on engien rpm, is the step down from 3.50 to a 3.43 is really worth it its only .07 difference, howmany rpms do you feel this shaves off?

  • grayracer513

Posted February 07, 2008 - 04:21 PM

#6

In a 426, it changes the top speed (assuming 10,500 in 5th and zero traction losses) by 1.8 mph. At 3000 rpm in 1st, it makes a change of .25 mph, or looking at it from a speed constant perspective, at 12 mph in 1st, it's a difference of about 150 rpm.

Remember that the final drive (rear chain) ratio is not your overall gearing. That is a product of the Primary ratio (engine to trans reduction = 2.952:1) x trans gear ratio (between 1.846 and 0.952:1) x final drive, which comes out to 9.836:1 in 5th with the stock sprockets and 9.436 if you go to a 47.

Using higher (low numeric) gearing to damp an engine is only marginally effective with bikes as powerful as the 426. Having run an '03 YZ450, which is a bike that needs taming as badly as any, with stock gearing, one tooth lower, and two teeth higher, I can tell you that the gearing did nothing to tame the engine in any configuration except where it allowed me to use 3rd gear in place of 2nd. Otherwise, it simply either added top speed or made low gear more or less useful in slow sections. The only thing that ever had a taming effect was the heavier flywheel and my right wrist.





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