I just changed the gearing in LazyBoy's 03 RM125 for a test and he liked the change so we are going to stick with that gearing (12/51). The only 51 I had was a cheap steel sprocket and while I have no trouble running a cheap sprocket I was shocked at how much more it weighed than the stock Sunstar 49t. My question is how much is that extra weight affecting performance, and should I run out and get the much lighter aluminum 51t now that we have picked a gearing to stick with? Also while were at it can one of the experts explain this "unsprung" weight thing to me, I know that's what they refer to it as since a few mechanics told me they would never run the steel when I asked at the races this weekend.
Effects of Unsprung Weight
- Thread starter Chili
- Start date
I think unsprung weight means anything which is not suspended by the suspension, e.g wheels tyres etc., and in general the less mass which is not under the control of the suspension the better, although of course the tyres themselves act as rudimentary suspension but offer limited damping etc! If you pick up a complete rear wheel assembly you will either think that a little extra weight on the sprocket won't make much difference, or you will think that the more weight you can save the better. They are heavy, especially with 18" rims and heavy tubes/tyres. I've never actually weighed tyres, but I always have the impression that Dunlops are lighter than most.
elf
Member
- Jun 7, 2003
- 695
- 0
Muddy has it right, anything that moves up and down with the suspension. The less unsprung weight the faster your suspension can react. That is why you see things like magnesium hubs on factory bikes. There is also another issue, rotational mass. The weight of all your moving parts that the engine has to move. In drag racing 10 pounds of rotational mass is equal to about 100 pounds of static weight.Meaning taking 10 pounds off your wheels is = to taking 100 pounds off the car. So more weight on the wheels = slower reacting suspension and slightly slower acceleration.
Of course Lazy boy might not even notice ;)
Of course Lazy boy might not even notice ;)
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