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Rotating Weight Question..........

SLOWPOKE693

SLOWPOKE693

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Would removing 21lbs of rotating weight from the drivetrain on my SxS make a big difference as far as acceleration goes?

I race my SxS at the local short course in the Vet N/A class and I'm getting out motored by a couple of guys I run with. I have them covered going into and through the turns and then get out motored on the straights. I'm looking for an easy way to make my car quicker without getting into pulling and building the motor. I have plans to add high compression pistons, a cam and port the head once the season is over (or I blow the motor up) but with the racing schedule and work travel it's not going to happen soon so I need something in the meantime to even the playing field some.

I found a company that makes a 15 x 7 billet center beadlock wheel that weights 11lbs 8oz vs my current beadlocks at 18lbs 8oz. I'm wondering if loosing 21lbs of rotating mass and unsprung weight by changing out the wheels would be worth it?


Pic of badass ultra light wheel for reference..... 😎

packard-performance-v2-super-star-beadlock-utv-wheel-set-15x7-4x137-gloss-black-pp-v2bl-15x7-s...jpg



What says the IBB?
 
Mathematically it will make a difference, but I would damn near guarantee that they will still pull you.
 
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Well, I know that when I added a bunch of rotating mass (tires and wheels), mine slowed WAAYYY down, so maybe?

Either way, I dig your SXS threads.

:beer:
 
Wilson said:
Mathematically it will make a difference, but I would damn near guarantee that they will still pull you.
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indeed. will it help? absolutely.

will it be enough? depends on how far away they are pulling you. don't remember the rough weight/hp ratio off-hand and unsprung rotating weight is moar better to reduce than sprung static weight.
 
Once upon a time, an old racer told me that shaving a pound of unsprung weight was equivalent to shaving three pounds of sprung/static weight. Shaving a pound of rotating weight was equivalent to shaving ten pounds of static weight. I'd say yes, it'd make a decent difference. Can't speak to "worth it", that one's on you.

I can similarly say that my 4runner is borderline road-undriveable with 39.5's on steel beadlocks with liners, and just slow with 315/70/17's (33, 35, tire dimensions are sometimes only marginally connected to reality it seems) on aluminum wheels. Obviously, tire size is a big factor there too, I don't have a means to compare weight for weight without changing size in the process.
 
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It'll make a notable difference imo. It's not just the amount of weight, but how far it is from the center of rotation. The longer the lever arm, the more the rotating mass matters. So the weight of wheels and tires makes a big difference. The brake rotors do as well, to a lesser degree because that weight is closer to the center. The weight of axle shafts doesn't help much as far as rotating mass, but it does help with unsprung weight (which the other options also help with).
 
ScottRS said:
Once upon a time, an old racer told me that shaving a pound of unsprung weight was equivalent to shaving three pounds of sprung/static weight. Shaving a pound of rotating weight was equivalent to shaving ten pounds of static weight. I'd say yes, it'd make a decent difference. Can't speak to "worth it", that one's on you
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This is pretty much what I remember from our circle track racing days. Anything and everything that spun in the drivetrain was super light. We ran 4.5" clutchs on automatic trans flywheels, Anything in the trans that didn't need to be there was removed, carbon fiber driveshaft, and the entire quick change rear assembly was of the ultralight variety. We even used spun shell wheels to keep those as light as possible.

My car only makes about 98hp to the wheels. I'm ththinking removing 28lbs of unsprung and rotating weight weight should be enough to feel a difference and help me get off the corners quicker.

The "worth it" part is subjective I guess. I'm out there to win races and not just drive around, so I think it might be worth it.
 
Like others have said, it will absolutely be better, but if it will solve your problem is a different question. Moment of inertia also plays a factor. The mass is easier to spin if the weight is located closer to the axis of rotation.

Some rules will put weight limits on crankshafts and other parts to try and limit the engine. We use to buy gun drilled crankshafts that were under the weight limit and press/weld tungsten slugs into the center to bring them back up to weight. Our cranks were the same weight as a "legal" crank, but our mass was closer to the center.
 
In the long game it’s worth it, because it is a beneficial part of the overall package. It may not be enough alone, but the net gain will be even greater once you build the motor.
 
Wilson said:
Mathematically it will make a difference, but I would damn near guarantee that they will still pull you.
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They are not pulling me by all that much now. Maybe 1-1 1/2 car lengths off the corners. I gain on them once we are back on the straight and they can't drive away from me. I only need a little more......... Story of my life! :laughing:
 
665.0coupe said:
Some rules will put weight limits on crankshafts and other parts to try and limit the engine. We use to buy gun drilled crankshafts that were under the weight limit and press/weld tungsten slugs into the center to bring them back up to weight. Our cranks were the same weight as a "legal" crank, but our mass was closer to the center.
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Hahahahaha....... That is exactly what our circle track engine builder used to do to our cranks. :smokin:
 
Yes, lose weight in rotating mass. I bet it helps more than you think. Can you lose any more weight anywhere else?
What about a cam? I bet that would help your low end if you use the right one. Sounds to me that's where you're getting beat, out of the hole and out of the corners. A diet, and a cam for some grunt will be good $ per hp per time spent imo.
 
Sterlingfire said:
Yes, lose weight in rotating mass. I bet it helps more than you think. Can you lose any more weight anywhere else?
What about a cam? I bet that would help your low end if you use the right one. Sounds to me that's where you're getting beat, out of the hole and out of the corners. A diet, and a cam for some grunt will be good $ per hp per time spent imo.
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I'd rather skip the engine mods until I have time to pull the motor and do it right and all at once. I'm sitting on a pair of 11.5-1 CP pistons, 1mm oversize Kibble White valves and a few other things for my motor build. Cam purchase is coming soon but will not be installed until I can pull the head and send it to FTZ Performance for porting, bigger valves and a 5 angle valve job. Probably won't happen until the winter unless I blow the stock one up.


Edit: I've removed as much weight as I could from this car. Not much else I can cut off to lighten it up...... I did pull the headlights, buckets and grill from the car on Sunday after the race. Probably 8 - 10lbs total. Not much but everything helps at this point.

20210314_192511.jpg
 
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SLOWPOKE693 said:
The "worth it" part is subjective I guess. I'm out there to win races and not just drive around, so I think it might be worth it.
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Speed costs money. How fast do you want to go??:flipoff2:

Can the new wheels be painted gold? Because the current wheels look pretty sweet.
 
665.0coupe said:
Speed costs money. How fast do you want to go??:flipoff2:

Can the new wheels be painted gold? Because the current wheels look pretty sweet.
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backchat said:
Anodized Gold would be sweet... and lighter...
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Yup. Nothing looks better than a red Honda with gold wheels. 😎 Company that makes the wheels pictured above offers different powder coating options for more money, but I can barely afford the wheels now, so I'll have to skip the custom stuff.

Fuckers won't answer their phone. :mad3: I want actual wheel weights before I pull the trigger on a 2k set of wheels. They have the beadlock and non beadlock listed at 11lbs 8oz. One of those #'s is definitely wrong. I'm hoping it's not the beadlock numbers.......
 
why can't you do a quick spirited driving around the block, preferably HOA neighborhood, then put something smaller and or lighter set on and go for another test run, and decide if the weight saving is worth it for the money? use small utility trailer tires or from an Aveo car? (I don't know what bolt pattern youre running)
 
No carbon wheels in that size?

How about losing some driver weight? Seats?

I know when we used to race 500# car 20lbs made a slight difference. But what really made a big different was reducing drivetrain loses where ever possible. Better bearings, seals, oils, etc that combined with the weight reduction was very noticeable.
 
In order to answer your question, I have to ask how much beer you can drink, that directly effects the speed and handling of the car. I have seen too many racers standing around cars drinking a beer and when they spill it does not land on their shoes, it lands on the belly of their custom sewn race suit. If they would switch to seltzers they could drop and easy 20 lbs or more off the sprung weight of the car without lifting a wrench. Or eat some taco bell and drop another 5 lbs before the race starts.
 
Sterlingfire said:
Yes, lose weight in rotating mass. I bet it helps more than you think..
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i agree, 10yrs ago when i swapped a 14b rear axle into my toyota, everything remained exactly the same down to the rims and beadlocks, the only thing i changed was the rear axle and it went from being an under powered 22re to an under powered gutless fucking turd 22re because of the massive heavy 14b diff. i would guess that heavier tires and rims would have a similar effect
 
Weasel said:
No carbon wheels in that size?

How about losing some driver weight? Seats?

I know when we used to race 500# car 20lbs made a slight difference. But what really made a big different was reducing drivetrain loses where ever possible. Better bearings, seals, oils, etc that combined with the weight reduction was very noticeable.
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First place I checked was Hiper Wheel. I had a set of their billet center carbon shell wheels on a 450R quad a bunch of years ago and they were stupid light. Unfortunately they only sell cast wheels for UTV's though.

I'm 6'2 and weigh 175lbs. There is no extra weight there to lose. HYDRODYNAMIC :laughing:

Car only has a single Corbeau tub style seat. I literally cut everything off the chassis that wasn't needed to race when I built it. Every extra bracket, nut, bolt or length of tube that was unnecessary was cut off. My exhaust is 23lbs lighter than stock, it has the stock paper thin plastic skids on it, and all the suspension arms except for the rear radius arms are stock because those are the lightest components that can be had. Main cage is 1-3/4 .095 wall and all the bracing is .065 wall. It's as light as I was comfortable making it for racing purposes. All the pre-built SxS cages available are .120 wall so I have less weight up high and one of the reasons my car handles better than other cars. F&R bumper are stupid light aluminum. The aluminum roof and doors are also way lighter than stock. The rest of the car is just a bunch of plastic and replacing it with aluminum wouldn't net me any real weight loss. That leaves me with wheels as my only other option to lighten up the car at this point. The fact that it is also rotating weight is a bonus.... :smokin:


Edit: I've already switched out all the oils for full synthetic Shockproof in various weights and run full synthetic engine oil. I have a wet clutch like a motorcycle so I can't get crazy with racing oils with friction modifiers.
 
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total newb said:
Should accelerate better.

If you bouncing off the rev limit youre not going to catch them regaurdless
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The way I look at it.

If its bogged down, and not wound up, when hes getting walked on... then it *might* help.
 
SLOWPOKE693 said:
First place I checked was Hiper Wheel. I had a set of their billet center carbon shell wheels on a 450R quad a bunch of years ago and they were stupid light. Unfortunately they only sell cast wheels for UTV's though.

I'm 6'2 and weigh 175lbs. There is no extra weight there to lose. HYDRODYNAMIC :laughing:

Car only has a single Corbeau tub style seat. I literally cut everything off the chassis that wasn't needed to race when I built it. Every extra bracket, nut, bolt or length of tube that was unnecessary was cut off. My exhaust is 23lbs lighter than stock, it has the stock paper thin plastic skids on it, and all the suspension arms except for the rear radius arms are stock because those are the lightest components that can be had. Main cage is 1-3/4 .095 wall and all the bracing is .065 wall. It's as light as I was comfortable making it for racing purposes. All the pre-built SxS cages available are .120 wall so I have less weight up high and one of the reasons my car handles better than other cars. F&R bumper are stupid light aluminum. The aluminum roof and doors are also way lighter than stock. The rest of the car is just a bunch of plastic and replacing it with aluminum wouldn't net me any real weight loss. That leaves me with wheels as my only other option to lighten up the car at this point. The fact that it is also rotating weight is a bonus.... :smokin:


Edit: I've already switched out all the oils for full synthetic Shockproof in various weights and run full synthetic engine oil. I have a wet clutch like a motorcycle so I can't get crazy with racing oils with friction modifiers.
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We were doing things like polishing the CV housing a balls so they spin and move by blowing on them. Running better bearings in the hubs, pulling seals and checking to see if they improved drag, polishing the ever loving crap out of the cv's, ceramic bearings. But we also had a fixed engine source and overall the weight package was quite a bit less then what your dealing with.

I know you said those tires are working well but they also look heavy/wide? The race BFGs are pretty light?

A few extra hp would probably net you more then the wheels would or anything else. It's a decent weight drop but I don't think you'll see the result your looking for, bridging the gap on pulling 15' on you. I'd spend the money on something engine related.
 
It's too bad Hiper technology's got gobbled up by the group that owns Weld. They don't even make UTV wheels anymore. They would have shaved another 2# per corner over those billet wheels.

Not only will lighter wheels make you faster, they will make your car handle better. Less unsprung weight is always better.
 
The Hoosiers I run are 24.5lbs each. The Maxxis SC-1's weigh exactly the same so their is no weight to be lost switching brands.

I should also mention the car I'm chasing is a Polaris SC-1 with what sounds like a decently healthy motor. I'm not exactly comparing apples with apples here. Those things are basicly sprint cars with super wide long travel suspensions. That's my stock motored fat pig in the background trying to keep pace at the end of a straightaway.

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You are 100% correct about the motor mods being my best option. Im just being thick headed and trying to avoid pulling it out in between races.
 
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