Are Lightweight Rims worth the investment?

6UE5t

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6UE5t

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nowadays the standard offset for 15" is always +35. hahaha. go all shops, +35. if want specific offset then need to order.
My son's Swift also now use 15x7 et35 coz it's the best offset to just lineup with the fenders.
20200712_124031.jpg
 

Izso

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Izso

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Here are some newer ones:
I dunno man.

the 2nd and 3rd video examples show a difference in diameter. Hypothetically - If traction wasn't a factor - switching from a 15" to 12" tyre and wheel package would technically increase acceleration for a car. However if the same car switched from 15" to a lighter 15" with the same HP (power), then acceleration should improve which is what I've been saying - response. It doesn't increase HP.

Engineering explained talked about rotational mass - that one I can agree. I'm trying to apply the concept in my head and it's giving my headaches. His bicycle wheel example compares one low profile vs one high profile wheel and according to his theory the higher profile wheel will be quicker to roll down the hill even though both are the same diameter. But in a real car situation - a smaller wheel bigger profile tyre wouldn't deliver the same kind of blistering performance feel due to tyre flex and probably other things I don't understand.

Right now I'm talking about improving performance by means of response, ie-acceleration resulting from changing 15" heavy to 15" lightweight rims.

Can an asian dude with good maths please come in explain to us if this improves HP as well? Because I don't think it does. I agree it improves acceleration because the rotational mass is less but does higher acceleration = higher HP? Or just less resistance to the torque needed to turn that mass?
 

6UE5t

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6UE5t

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I dunno man.

the 2nd and 3rd video examples show a difference in diameter. Hypothetically - If traction wasn't a factor - switching from a 15" to 12" tyre and wheel package would technically increase acceleration for a car. However if the same car switched from 15" to a lighter 15" with the same HP (power), then acceleration should improve which is what I've been saying - response. It doesn't increase HP.

Engineering explained talked about rotational mass - that one I can agree. I'm trying to apply the concept in my head and it's giving my headaches. His bicycle wheel example compares one low profile vs one high profile wheel and according to his theory the higher profile wheel will be quicker to roll down the hill even though both are the same diameter. But in a real car situation - a smaller wheel bigger profile tyre wouldn't deliver the same kind of blistering performance feel due to tyre flex and probably other things I don't understand.

Right now I'm talking about improving performance by means of response, ie-acceleration resulting from changing 15" heavy to 15" lightweight rims.

Can an asian dude with good maths please come in explain to us if this improves HP as well? Because I don't think it does. I agree it improves acceleration because the rotational mass is less but does higher acceleration = higher HP? Or just less resistance to the torque needed to turn that mass?
The difference in diameter is just the wheels but not the overall diameter, at least not significantly. But the weight difference are significant there. This is talking about transferring power to the ground. If there's no additional power going to the ground to move the car quicker then what does?? Power at the engine is the same but there's not as much loss used to rotate the mass of the wheels hence enabling the power more to move the car.
 

gunnerzz

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The difference in diameter is just the wheels but not the overall diameter, at least not significantly. But the weight difference are significant there. This is talking about transferring power to the ground. If there's no additional power going to the ground to move the car quicker then what does?? Power at the engine is the same but there's not as much loss used to rotate the mass of the wheels hence enabling the power more to move the car.
I suck at math and only loves to look at the outcome.

However, since we all agree that gb eats up some hp from the engine thus making hp at the wheel lower to hp at the flywheel...i am guessing whatever parts (including the rims) which are there to transfer the power from the engine to the road will have impact in hp figure. Its a matter of how much.

Would be interesting to see a dyno chart though. Then do the dyno again...this time removes the drive wheel disc brakes...i would love to see the outcome.
 

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Izso

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The difference in diameter is just the wheels but not the overall diameter, at least not significantly. But the weight difference are significant there. This is talking about transferring power to the ground. If there's no additional power going to the ground to move the car quicker then what does?? Power at the engine is the same but there's not as much loss used to rotate the mass of the wheels hence enabling the power more to move the car.
Ok I'm beginning to see the disconnect now. What you're saying here is you'll potentially regain some lost power. You won't gain power like what was said originally. This much I can agree! But I also did say the gains is minimal in the beginning.

Diameter of the whole wheel package (tyres and all) between a 20" and 18" is pretty significant. Based on the dimension given by the bloke in the 2nd video, it's roughly 5% difference. That alone would contribute to the slower acceleration on top of the wheel weight. Anyway, the 2nd and 3rd video has too many discrepancies. What we should do is make a video comparison between same diameter, same tyre and just a difference in wheel weight.

Anyway thinking too much about this is giving me a bloody headache. I'm done thinking. Hahaha! We all generally agree that lightweight means more better.

I suck at math and only loves to look at the outcome.

However, since we all agree that gb eats up some hp from the engine thus making hp at the wheel lower to hp at the flywheel...i am guessing whatever parts (including the rims) which are there to transfer the power from the engine to the road will have impact in hp figure. Its a matter of how much.

Would be interesting to see a dyno chart though. Then do the dyno again...this time removes the drive wheel disc brakes...i would love to see the outcome.
You know what we should do? We should start a ZTH video channel where members get together to properly mythbust or discuss topics like this and share on Youtube.

Cuz I sure would like to see for myself how this'll turn out on a wheel dyno and hub dyno.
 

leinnz

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leinnz

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You know what we should do? We should start a ZTH video channel where members get together to properly mythbust or discuss topics like this and share on Youtube.

Cuz I sure would like to see for myself how this'll turn out on a wheel dyno and hub dyno.
racenotrice revival too
 

DNGFashion

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DNGFashion

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love the discussions here.

Maybe we need to define what is HP?
HP rated at engine or HP rated effectively on the ground (BHP)?

Engineering Explained has a very good point on rotational mass. Having a lightweight piston, crankshaft, driveshaft, flywheel and all parts that delivered power to the ground essentially increases BHP and probably slight increment in HP rated at engine for the same engine capacity.
 

lsm1991

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lsm1991

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love the discussions here.

Maybe we need to define what is HP?
HP rated at engine or HP rated effectively on the ground (BHP)?

Engineering Explained has a very good point on rotational mass. Having a lightweight piston, crankshaft, driveshaft, flywheel and all parts that delivered power to the ground essentially increases BHP and probably slight increment in HP rated at engine for the same engine capacity.
erm..... hp vs bhp??

i think you want to discuss crank hp (i believe this what you are referencing to as is the bhp) vs wheel hp (at the wheels)

hp vs bhp, no real point thinking bout it
 

6UE5t

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6UE5t

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Ok I'm beginning to see the disconnect now. What you're saying here is you'll potentially regain some lost power. You won't gain power like what was said originally. This much I can agree! But I also did say the gains is minimal in the beginning.

Diameter of the whole wheel package (tyres and all) between a 20" and 18" is pretty significant. Based on the dimension given by the bloke in the 2nd video, it's roughly 5% difference. That alone would contribute to the slower acceleration on top of the wheel weight. Anyway, the 2nd and 3rd video has too many discrepancies. What we should do is make a video comparison between same diameter, same tyre and just a difference in wheel weight.

Anyway thinking too much about this is giving me a bloody headache. I'm done thinking. Hahaha! We all generally agree that lightweight means more better.


You know what we should do? We should start a ZTH video channel where members get together to properly mythbust or discuss topics like this and share on Youtube.

Cuz I sure would like to see for myself how this'll turn out on a wheel dyno and hub dyno.
Nope the 5% difference he mentioned is not the rolling diameter difference but he expected around 5% difference in dyno results! The 20' tyre he used was 255/35/20 while stock 18' should be 235/50/18 which is actually bigger rolling diameter than the 20' tires! So despite running bigger rolling diameter, it actually got 20whp more than the heavier 20' setup with slightly smaller rolling diameter. To me it's pretty conclusive. I had seen many other tests long time ago but just cannot find them anymore.