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      02-02-2020, 10:00 PM   #1
MBan
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Do light wheels make a measurable power difference?

Hi all,

I have some new forged wheels on the way (Advan RS-DF) and I am wondering if I should dyno the car before fitting them (rolling-road style dyno, not a hub dyno, obviously) to see what power difference they make at the wheels... if any. I think there should be a difference but happy to be corrected if physics says otherwise.

On the Superstreetonline project Z4M they made an additional 13hp and 10ft-lb by fitting wheels that are 4lb lighter each.

Has anyone ever dyno tested lightweight wheels? Will I see a measurable difference?
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      02-03-2020, 09:46 AM   #2
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My OZ Ultraleggera 18 in rms were weighed vs the stock rims and the OZ's weight savings is an incredible 42.4 lbs....the rotating or spinning mass of reducing over 10 lbs at each wheel positively affects corner turn-in and reduces braking mass and unsprung weight.
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      02-04-2020, 02:57 AM   #3
MBan
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Thanks, racerbruce.

Did you measure power before and after fitting your wheels?

I’ve had lightweight wheels on pretty much all my cars and love the performance benefits but I have never done pre- and post-install dyno runs to see if there is a measurable power difference.
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      02-04-2020, 08:07 AM   #4
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Testing

Quote:
Originally Posted by MBan View Post
Thanks, racerbruce.

Did you measure power before and after fitting your wheels?

I’ve had lightweight wheels on pretty much all my cars and love the performance benefits but I have never done pre- and post-install dyno runs to see if there is a measurable power difference.
I didn't - unsure of any dyno results.
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      02-05-2020, 03:17 AM   #5
MBan
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Okay, thanks.

We’ll see if someone else has experience. I’m quite curious about this given how common it is to fit lightweight wheels.
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      02-06-2020, 03:25 AM   #6
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Yesterday I stumbled on an old discussion about this on m3forum and the superstreet article was referenced. There was a bit of debate and consensus wasn’t reached (it’s an online forum, after all) but it was interesting to read. Still no first hand, dyno-proven results though.

http://www.m3forum.net/m3forum/showt...=218821&page=6
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      02-16-2020, 04:15 PM   #7
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BHP measured at the engine, no. WHP measured steady-state, no. WHP measured while accelerating, yes, because you will have less power losses from spinning up the rotational mass of the wheels. Lightweight flywheels work on the same principle.

http://www.uucmotorwerks.com/flywhee...heel_works.htm

Whether this power gain will show on a dyno depends on the type of dyno and how it measures HP. An inertial dyno would theoretically see a difference but I'm not sure if it's large enough of a difference to show up.

https://en.wikipedia.org/wiki/Dynamo...of_sweep_tests
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      02-17-2020, 03:52 AM   #8
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Thanks, filtercoffee - great information.

I think load dynos (e.g. Dyno Dynamics) should also see a difference (theoretically at least)?
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      02-18-2020, 04:53 AM   #9
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Nice wheels, my personal favourite. Congrats. Pics when they are on please..
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      02-20-2020, 11:40 PM   #10
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Quote:
Originally Posted by Vanne View Post
Nice wheels, my personal favourite. Congrats. Pics when they are on please..
Thanks, Vanne.

I’ll definitely post up some pictures when I have them fitted... which reminds me that I should follow up and find out if they have left J yet.
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      03-10-2020, 04:03 PM   #11
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Wheels are essential in clutching with expensive. Will light wheels give more power? Some people claim to reject it. This topic was in auto reviews.

Last edited by mendelarnos; 03-10-2020 at 04:15 PM..
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      03-10-2020, 04:25 PM   #12
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What is important is what the grip of the wheels will be on the road and how much energy will be spent on overcoming mechanical losses. It is impossible to get rid of them completely, but it is real to reduce it. For example, it could be Body Kits For Bmw X5 G05 PUNISHINGER https://rng-t.com/body_kit/bmw/bmw-x5-g05-punisher/. Such body kits increase the aerodynamic performance of the car. The body of the car with the elements of the body, more easily overcomes the resistance of the air.
The front bumper will increase the downforce of the front of the car. The rear bumper weight will eliminate the appearance of air swirls under the rear of the car. This will improve the grip of the wheels with the road surface. The side body kit also works - excludes air swirls in the side parts of the car.
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