Effects of Rotational/Unsprung weight Loss
02-19-2009, 07:22 PM
#21
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i've been looking at the greg weld fronts from summit. right now they're $99 each for a 15x3.5 with 1.75 in BS. if i paired that with a mickey thompson front runner 26"x4.5-15 (if that's the right tire), how much could i expect to gain et/mph over my 17x9.5 AR TTM's with 275-40-17 nittos? (they weigh ~45lbs each as they sit) i would plan on pro star rears in the 15x8-10" variety. i would use the Greg Weld rears if they would fit. did the 8" GW's ever get fixed?
02-20-2009, 05:01 AM
#25
For the original poster:.. IN 2007, my car wouldn't pull a tire hardly at all, car was 3550 all season, even with the last couple passes with the nitrous it wasn't pulling the tires at all.
This year, I got about 200 lbs out, ds2 tires from m/t sportsmans was one change, 12 lbs pre tire less, I went to a motor plate, elec. water pump, ditched the power steering, all the uneeded wiring, and I took the little pc 680 battery, tossed it in the trash and put a real full battery back in the trunk (little thing wouldn't crank the car for ****) Also put drag brakes on the car and went to a manual master, for a total of 120 lbs for that alont. 65 of which was the front brakes. Also did a spool in the back, rear end with the drag brakes and the spool was 40 lbs lighter then it was with the stock brakes and a posi unit.
So, the car lost 200 lbs, and about 65 lbs went into the trunk.
Car never pulled a tire more then a few inches before these changes, 1st pass on a 150 shot it went on the bumper.
So yes, the unsprung weight, definately helps alot, rotational weight makes more if a difference then regular sprung chassis weight.
This year, I got about 200 lbs out, ds2 tires from m/t sportsmans was one change, 12 lbs pre tire less, I went to a motor plate, elec. water pump, ditched the power steering, all the uneeded wiring, and I took the little pc 680 battery, tossed it in the trash and put a real full battery back in the trunk (little thing wouldn't crank the car for ****) Also put drag brakes on the car and went to a manual master, for a total of 120 lbs for that alont. 65 of which was the front brakes. Also did a spool in the back, rear end with the drag brakes and the spool was 40 lbs lighter then it was with the stock brakes and a posi unit.
So, the car lost 200 lbs, and about 65 lbs went into the trunk.
Car never pulled a tire more then a few inches before these changes, 1st pass on a 150 shot it went on the bumper.
So yes, the unsprung weight, definately helps alot, rotational weight makes more if a difference then regular sprung chassis weight.
02-20-2009, 11:28 AM
#26
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I deleted your weight list since that's already a sticky and not needed in the discussion.
Derek
02-24-2009, 07:28 PM
#27
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For the original poster:.. IN 2007, my car wouldn't pull a tire hardly at all, car was 3550 all season, even with the last couple passes with the nitrous it wasn't pulling the tires at all.
This year, I got about 200 lbs out, ds2 tires from m/t sportsmans was one change, 12 lbs pre tire less, I went to a motor plate, elec. water pump, ditched the power steering, all the uneeded wiring, and I took the little pc 680 battery, tossed it in the trash and put a real full battery back in the trunk (little thing wouldn't crank the car for ****) Also put drag brakes on the car and went to a manual master, for a total of 120 lbs for that alont. 65 of which was the front brakes. Also did a spool in the back, rear end with the drag brakes and the spool was 40 lbs lighter then it was with the stock brakes and a posi unit.
So, the car lost 200 lbs, and about 65 lbs went into the trunk.
Car never pulled a tire more then a few inches before these changes, 1st pass on a 150 shot it went on the bumper.
So yes, the unsprung weight, definately helps alot, rotational weight makes more if a difference then regular sprung chassis weight.
This year, I got about 200 lbs out, ds2 tires from m/t sportsmans was one change, 12 lbs pre tire less, I went to a motor plate, elec. water pump, ditched the power steering, all the uneeded wiring, and I took the little pc 680 battery, tossed it in the trash and put a real full battery back in the trunk (little thing wouldn't crank the car for ****) Also put drag brakes on the car and went to a manual master, for a total of 120 lbs for that alont. 65 of which was the front brakes. Also did a spool in the back, rear end with the drag brakes and the spool was 40 lbs lighter then it was with the stock brakes and a posi unit.
So, the car lost 200 lbs, and about 65 lbs went into the trunk.
Car never pulled a tire more then a few inches before these changes, 1st pass on a 150 shot it went on the bumper.
So yes, the unsprung weight, definately helps alot, rotational weight makes more if a difference then regular sprung chassis weight.
02-25-2009, 05:25 AM
#28
I've been racing for years, atv's, radio controlled cars, now drag racing for a few. I've done enough tests in enough different types of racing to say that unsprung weight, is generally something that you don't want.
However, I can think of one instance that it is used, on limited suspension circle track racing I do know people that have weighted the left front spindle to help keep the tire on the ground and get it to help turn the car better.... but that's a totally different situation and is a crutch because of the rules of the class, and we won't go there.
However, I can think of one instance that it is used, on limited suspension circle track racing I do know people that have weighted the left front spindle to help keep the tire on the ground and get it to help turn the car better.... but that's a totally different situation and is a crutch because of the rules of the class, and we won't go there.
02-25-2009, 05:46 AM
#29
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Yeah, I never see myself weighting down one of my spindles to keep the tire on the ground, I am more of a wheel stand guy personally! 
IMO there are two cars in Drag Racing for two reasons...
Dragsters - Built to be dead consistent, be extremely light, and be the fastest vehicle on the track.
Door Cars - Look more like your average car, be consistent, and to look cool all while on the bumper! lol
IMO there are two cars in Drag Racing for two reasons...
Dragsters - Built to be dead consistent, be extremely light, and be the fastest vehicle on the track.
Door Cars - Look more like your average car, be consistent, and to look cool all while on the bumper! lol
02-25-2009, 06:20 AM
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I agree that reduction in rotational weight makes a bigger difference, but the larger the diameter, the greater the gain (i.e. brake rotor diameter are about 12 inch while a tire is closer to 26 inches and both turn the same RPM). I would rather save the weight off the tire over a rim or a brake rotor, if not doing all of them.
Bob
Bob
02-25-2009, 07:56 AM
#31
Correct. Same goes with driveshafts, everything that's turning in the car. The more weight that you can get off from the part that is farthest from center the better off.
Example, going to a wheel that's 2 lbs lighter on the front is great, but taking 2 lbs off the tires themselves, way better idea and the gains will be larger.
Gun drilling axles, sure it's rotational weight, but it's at the center of the rotation, making the weight that's lost the least effective... one reason that I feel that they are a waste unless all other options are already done.
Taking weight off the rotating assy of a motor, definately a worth while excersize, reducing the weight of the parts that spin the most rpm will also net larger gains, example, 5 lbs off the engine's rotating assy would make a WAY bigger difference then taking 5 lbs of rotating weight off the tires.
Example, going to a wheel that's 2 lbs lighter on the front is great, but taking 2 lbs off the tires themselves, way better idea and the gains will be larger.
Gun drilling axles, sure it's rotational weight, but it's at the center of the rotation, making the weight that's lost the least effective... one reason that I feel that they are a waste unless all other options are already done.
Taking weight off the rotating assy of a motor, definately a worth while excersize, reducing the weight of the parts that spin the most rpm will also net larger gains, example, 5 lbs off the engine's rotating assy would make a WAY bigger difference then taking 5 lbs of rotating weight off the tires.
10-06-2009, 02:04 PM
#32
Okay, I know this thread is ancient but the reason I'm gravedigging is because I'm about to try out my Draglite 3.5" skinnies with Moroso Drag Specials. (Hey, at least I didn't start a new thread without doing a search. 
)The 16x8 Camaro wheels with Khumo tires weigh just over 43 lbs per combo, while the Draglite/Moroso combos weigh just under 20 lbs each (10 lb wheel, 10 lb tire). What kind of drop in ET should I expect with this? My car doesn't launch hard, so traction is probably not an issue either way.
)The 16x8 Camaro wheels with Khumo tires weigh just over 43 lbs per combo, while the Draglite/Moroso combos weigh just under 20 lbs each (10 lb wheel, 10 lb tire). What kind of drop in ET should I expect with this? My car doesn't launch hard, so traction is probably not an issue either way.
10-06-2009, 02:18 PM
#33
You will see a gain, if the DA and everything else is exactly the same, I would think that should be good for about a tenth and about 1 mph. 1 lb of rotating weight lost, is like losing about 4 lbs of dead weight.
(some people will tell you 1 lb of rotating weight is 10 lbs, but the actual real world gains rarely support that equation)
Kudos' on the search too
(some people will tell you 1 lb of rotating weight is 10 lbs, but the actual real world gains rarely support that equation)
Kudos' on the search too
10-07-2009, 06:48 AM
#34
I'll need to look up the DA for my runs last night but going from the full-size fronts to the Draglites two hours later the car gained .5 mph and dropped .12 from the ET, same 60 ft. Car is running slower though, gotta figure that out (possible trans issue).
EDIT: Just found the DA (519) and did the calculation, my 13.03 @ 107.9 (1.99 60 ft) corrected to a 12.95 @ 108.5, slower than the 12.7s I've been running with full-size fronts. Something is wrong with my car.
EDIT: Just found the DA (519) and did the calculation, my 13.03 @ 107.9 (1.99 60 ft) corrected to a 12.95 @ 108.5, slower than the 12.7s I've been running with full-size fronts. Something is wrong with my car.
Last edited by Tommyv8; 10-07-2009 at 09:21 AM.
10-07-2009, 08:01 AM
#35
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I went from a Sears metric 165R 15 tire to a M/T ET Drag front, much lighter yes, did not weight the difference however.
I did not gain 2 tenths and 2mph...
At best I picked up .05in ET and .5mph... But I have a feeling it may have been even less than that.
Rotating mass is big sure, but I have a feeling it means more on the wheels providing power ie. the rear. Yes the moment of inertia on a heavier wheel/tire combo will make it harder to accelorate its rotation, but its not a boat anchor guys. 2mph... are u nuts?
I do not know if I would stake this much on reducing the weight of the front tires, its not a miricle cure. Going from a full sise front that weighs close to 45 to 50lbs to a light weight wheel and tire combo that is 25 lbs a 50lbs saings I saw less than a tenth in ET. How do you expect 20lbs to show 2 tenths and 2mph?
I think front wheels, drag brakes and axles are a reduction in UNSPRUNG MASS which is what matters. Reducing rotating mass will free up some HP on the dyno sure, but reducing unsprung mass will help your ET. Not 1:10 either... more like 1:4 or 1:3
I did not gain 2 tenths and 2mph...
At best I picked up .05in ET and .5mph... But I have a feeling it may have been even less than that.
Rotating mass is big sure, but I have a feeling it means more on the wheels providing power ie. the rear. Yes the moment of inertia on a heavier wheel/tire combo will make it harder to accelorate its rotation, but its not a boat anchor guys. 2mph... are u nuts?
I do not know if I would stake this much on reducing the weight of the front tires, its not a miricle cure. Going from a full sise front that weighs close to 45 to 50lbs to a light weight wheel and tire combo that is 25 lbs a 50lbs saings I saw less than a tenth in ET. How do you expect 20lbs to show 2 tenths and 2mph?
I think front wheels, drag brakes and axles are a reduction in UNSPRUNG MASS which is what matters. Reducing rotating mass will free up some HP on the dyno sure, but reducing unsprung mass will help your ET. Not 1:10 either... more like 1:4 or 1:3
01-25-2010, 03:41 PM
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For the original poster:.. IN 2007, my car wouldn't pull a tire hardly at all, car was 3550 all season, even with the last couple passes with the nitrous it wasn't pulling the tires at all.
This year, I got about 200 lbs out, ds2 tires from m/t sportsmans was one change, 12 lbs pre tire less, I went to a motor plate, elec. water pump, ditched the power steering, all the uneeded wiring, and I took the little pc 680 battery, tossed it in the trash and put a real full battery back in the trunk (little thing wouldn't crank the car for ****) Also put drag brakes on the car and went to a manual master, for a total of 120 lbs for that alont. 65 of which was the front brakes. Also did a spool in the back, rear end with the drag brakes and the spool was 40 lbs lighter then it was with the stock brakes and a posi unit.
So, the car lost 200 lbs, and about 65 lbs went into the trunk.
Car never pulled a tire more then a few inches before these changes, 1st pass on a 150 shot it went on the bumper.
So yes, the unsprung weight, definately helps alot, rotational weight makes more if a difference then regular sprung chassis weight.
This year, I got about 200 lbs out, ds2 tires from m/t sportsmans was one change, 12 lbs pre tire less, I went to a motor plate, elec. water pump, ditched the power steering, all the uneeded wiring, and I took the little pc 680 battery, tossed it in the trash and put a real full battery back in the trunk (little thing wouldn't crank the car for ****) Also put drag brakes on the car and went to a manual master, for a total of 120 lbs for that alont. 65 of which was the front brakes. Also did a spool in the back, rear end with the drag brakes and the spool was 40 lbs lighter then it was with the stock brakes and a posi unit.
So, the car lost 200 lbs, and about 65 lbs went into the trunk.
Car never pulled a tire more then a few inches before these changes, 1st pass on a 150 shot it went on the bumper.
So yes, the unsprung weight, definately helps alot, rotational weight makes more if a difference then regular sprung chassis weight.
JL Were the tire you had on your car the MT sportsman pros and if so what size were they. I have been thinking about switching my front runners to maybe the goodyears.
01-26-2010, 05:31 AM
#40
I had the 4 ply sportsman pro's, 26x7.5x15 Went to the 26x4.5x15 moroso ds-2. The 2 of those, were lighter then 1 of the m/t sportsman tires. m/t front runners are about the same weight as a ds2, maybe a touch heavier, I just got the moroso tires at a good price.