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Discussion Starter #1
I was shopping for tires for autocross and came across some discussions on unsprung/rotational weight loss vs power increase.
Then I start thinking since the sport rims are heavy, compare to RV6 pipe+ ktuner method, switching to lighter rim might be equal or more cost effective to improve a sport's acceleration and handling.

So I did some quick calculations.
Stock sport rim + tires(Mine is Eagle LS-2)= 28+25=53lb
ENKEI TS9 17X8 + Pilot super sport = 18.65+22= 40.65lb
It will lose 12.35lb per wheel and total of 49.4lb unsprung/rotational weight.

Total cost=573.96(tires)+780(Rim)= $1353.96.
The stock wheels+tires probably worth at least 600+.

Then the cost of switching rim/tires and RV6 pipe/ktuner would come out about the same.

With the weight loss mod, you improve acceleration, handling(a lot) and MPG. To me it comes down to the question how much WHP/tq and throttle response this 49.4lb unsprung/rotational weight loss mod will actual get you.

It would be nice if anyone got a dyno for the weight loss mod.
 

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8th Gen 6-6 Red Coupe
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Edit: somehow missed how this is for a track car. I would recommend getting sway bars. Nice tires would help a lot too, but whole rims are unnecessary.
Unsprung weight isn't too much of a factor unless you go up to 20" rims, and even then isn't too much of a factor.

The gains from raw hp and torque mods are far more noticeable and usable in my opinion. The 9th Gen has proven that it highly benefits from a quality exhaust.

Search around Google about engine power mods vs unsprung weight and I'm sure many would agree with my opinion. Typically unless building a track star or weekend warrior weight reduction doesn't improve daily driving very much. And even then would be something I would do after power mods.

Weight location both laterally and longitudinally does however. A bullet proof super heavy sunroof would be extremely detrimental to handling vs if the same weight was located in the rear of the car, counter weighting the engine weight in the front.

Then of course is the issue that these cars are unfortunately front wheel driven, and a more so equal balanced car would improve handling while causing traction reduction of the forward wheels under higher engine power.

Huge topic really but, again to answer your question, just go with a good quality exhaust.

BTW : there are two different dynos. I don't remember which is which, but one actually reads the affect of inertial load, while the other one ignores this and reads power. The one that reads inertial load always shows much less hp but is much more accurate to show usable power. These dynos would be affected by wheel weights and rim sizes unlike the other type.

Also, check this pictue to read about wheel weight affect on real world conditions. It's about rim up sizing, but weight is there too; note how little is really and truly affected...

 

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The dyno would not help much. The decrease in rotational inertia would apply to all four wheels however a dyno only measures the torque on the power wheels. It can’t measure the power benefit created by the lighter rims/tires on the non-power wheels.

Years ago I ran across an amazing excel spreadsheet that calculates (very closely estimates) the change in power due to a change in wheel weight, tire weight, wheel diameter and tire diameter (or any combination).

It appears you intend to go from 25 lbs 235/45-18 tires mounted on 28 lbs 18” wheels to 22lbs. 215/55-17 tires mounted on 18.65 lbs 17” rims. (Tire size is part of the calculation.)

The car’s rate of acceleration is also part of the calculation. You said Sport, but I don’t know your transmission type. Based on the numbers above, here are the increases in horsepower and torque based on different Accords.

CVT: 0-60 in 7.6 seconds----- +17hp and +16lbs-ft.
6MT Sport: 0-60 in 6.6 seconds ----+19HP and +17lbs-ft.
V6 Accord : 0-60 in 5.6 seconds---- +22HP and +20lbs-ft.

You WILL feel a 17-19 hp change. Believe or not, dropping rim size and tire weight has more of an impact than the light weight wheel. Going to 25-lbs OEM 17” wheels with 22lbs tires would give the CVT and extra 11 hp, the I4-6MT 13hp and the V6 Accord 15hp. Pretty much a 6 hp difference across the board compared to having the 18lbs 17" wheels.

If you want this excel spreadsheet, PM me your email address and I’ll send it. That goes for anybody else too.
 

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Basque Red Fury
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The car feels much lighter on its feet since I changed my wheels and tires. I'm on 245/40/18 Continental ExtremeContact DW and TSW Sochi 18, total 43 lb per wheel and I absolutely love them
 

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According to Enkei: "Every pound of unsprung weight savings has the effect of reducing overall vehicle weight by 20lbs."
OAKOS Automotive - STi & WRX Performance Parts: Enkei RPF1 Wheels (17x8", 45mm, 5x114.3, Set/4) Silver

Others claim it's more like 4 lbs.

I'm no engineer, but I don't think the actual power or torque is changed, but because wheels and tires are like flywheels, the decreased rotational mass does make for quicker acceleration and braking.

I like my car better since I put on Enkei Raijin wheels.
 

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Discussion Starter #6
Edit:

Also, check this pictue to read about wheel weight affect on real world conditions. It's about rim up sizing, but weight is there too; note how little is really and truly affected...

I don't consider 0.3sec drop for 0-60 and 2mpg improvement are little comparing first and last column in the picture. You get around 15hp and 15 tq from the pipe+ktuner mod.I guess it is going to drop you less than 0.5sec for 0-60. However, it isn't a very good comparison since the pic drops from 19"-15" and mine is 18” to 17". But the weight loss is similar.

The dyno would not help much. The decrease in rotational inertia would apply to all four wheels however a dyno only measures the torque on the power wheels. It can’t measure the power benefit created by the lighter rims/tires on the non-power wheels.

Years ago I ran across an amazing excel spreadsheet that calculates (very closely estimates) the change in power due to a change in wheel weight, tire weight, wheel diameter and tire diameter (or any combination).

It appears you intend to go from 25 lbs 235/45-18 tires mounted on 28 lbs 18” wheels to 22lbs. 215/55-17 tires mounted on 18.65 lbs 17” rims. (Tire size is part of the calculation.)

The car’s rate of acceleration is also part of the calculation. You said Sport, but I don’t know your transmission type. Based on the numbers above, here are the increases in horsepower and torque based on different Accords.

CVT: 0-60 in 7.6 seconds----- +17hp and +16lbs-ft.
6MT Sport: 0-60 in 6.6 seconds ----+19HP and +17lbs-ft.
V6 Accord : 0-60 in 5.6 seconds---- +22HP and +20lbs-ft.

You WILL feel a 17-19 hp change. Believe or not, dropping rim size and tire weight has more of an impact than the light weight wheel. Going to 25-lbs OEM 17” wheels with 22lbs tires would give the CVT and extra 11 hp, the I4-6MT 13hp and the V6 Accord 15hp. Pretty much a 6 hp difference across the board compared to having the 18lbs 17" wheels.

If you want this excel spreadsheet, PM me your email address and I’ll send it. That goes for anybody else too.
Good point on the dyno. But I guess you can still get a idea how the rotational weight will impact the whp and tq if you can get several data points from dynos with different weight loss.

WOW, if these numbers from the excel sheet are true, then this definitely is a better mod since the pipe+ktuner only add about 15 hp and tq. Not to mention all the other benefits: handling(from better tires),MPG and breaking. In the other hand, you need 91 gas for the power mod.

Personally, with the other benefits , I will consider this a better way to go even if it will only provide 50% of the power improvement of what the power mod can provide.

I have PM you for the spreadsheet. I really want to see how the calculations were being done for these numbers.:nerd
Sorry for the missing information. I have a CVT sport. I thought the drive train does not matter in this case. But I guess the MT drivers would appreciate the info too.
 

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'15 6-6
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I was shopping for tires for autocross and came across some discussions on unsprung/rotational weight loss vs power increase.
Then I start thinking since the sport rims are heavy, compare to RV6 pipe+ ktuner method, switching to lighter rim might be equal or more cost effective to improve a sport's acceleration and handling.

So I did some quick calculations.
Stock sport rim + tires(Mine is Eagle LS-2)= 28+25=53lb
ENKEI TS9 17X8 + Pilot super sport = 18.65+22= 40.65lb
It will lose 12.35lb per wheel and total of 49.4lb unsprung/rotational weight.

Total cost=573.96(tires)+780(Rim)= $1353.96.
The stock wheels+tires probably worth at least 600+.

Then the cost of switching rim/tires and RV6 pipe/ktuner would come out about the same.

With the weight loss mod, you improve acceleration, handling(a lot) and MPG. To me it comes down to the question how much WHP/tq and throttle response this 49.4lb unsprung/rotational weight loss mod will actual get you.

It would be nice if anyone got a dyno for the weight loss mod.
I'm assuming you have a V6?

The best bang for your buck if you want straight line performance would actually be to get some lightweight 18x8 wheels, put your stock tires on them, sell the stock wheels, then use the savings to buy an RV6 J pipe and CAI.

18x8 wheels - $750
J Pipe + CAI, no KTuner - $700
---------------------------------------
Total 1550
Sell stock wheels - $400

Final Total - $1150, which is roughly the cost of J Pipe, KTuner, and Custom tune, or the price of a nice set of wheels and tires.

If you care about grip, skip the performance mods for now and focus on wheels, tires, and suspension.
 

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if you gutted your car you would feel more power and would be faster than anything they have out for the accord now. power to weight ratio. thats what hondas are known for. being light. i own two Eg's fully gutted and an EK drag car. if you took your seats out and your spare tire and tools and put a light weight seat in there and took out all unnecessary things in the car, your car would dominate the track. '

But im not sure how far you want to go with it.

one day i plan on putting this J series from a 9th gen in my EG and it will be an easy 12 second and possibly break 11's depending on how much weight i shave off and slicks/60ft
 

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Honestly, I'd invest in lighter wheels and stickier rubber before doing any engine mods. The V6 cars are traction-limited, even with the stock level of power. Adding any more power just exacerbates the issue. And excess wheel weight is an enemy to performance no matter how much power you have.

An engineer once told me that losing 1 pound at each wheel is the equivalent of lightening the car by 32 lbs, as a rule of thumb. So if you lighten each corner by 10 pounds, you're essentially shedding 320 pounds. Rather, the reduced rotational inertia equates to a performance improvement equivalent to lightening the car by 320 lbs.

We saw the effects of this big time back in the 6th gen days where replacing the stock 15" sedan (~40 lbs with tire) or 16" coupe (~43 lbs with tire) rims with much heavier 17" 2nd Gen TL-S rims (~50 lbs with tire) caused a huge drop in performance. Guys with the TL-S wheels and typical bolt-ons (intake, headers, pulleys, exhaust) were running track times that were barely quicker than stock V6 Accords. With the stock wheels or just lighter aftermarket wheels, guys with the same mods were running at least half a second quicker at the track.
 

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2.5th gear
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2014 Canadian Sport 6mt
i have the PCD Downpipe + resonator and Ktuner 91+octane tuned.
I will buy lighter 18inch wheel next summer why ?
because i did buy winter rim which are 10lbs lighter then my Summer Sport wheels
and the car did feel so much lighter .
But i didnt have the Ktuner + PCD downpipe with the winter rims.
I installed everything when i reinstall my summer wheels.
The car feels a bit like it was in the winter with lighter wheels.
SO i can say its almost equal in performance yes.
I can;t wait to have lighter rims in the summer ;)
but ill have fun with my winter tire loll.hope i won't kill em to fast
 

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Yes.

18" = 28#
19" = 27#

Many aftermarket wheels are ~20#.
 

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18" = 28#
19" = 27#

Many aftermarket wheels are ~20#.
Not a huge difference, but at least the 19s are less. I suspect the one-size-up-from-stock tires I want to put on 19s would be slightly heavier than the stock 18s since they are slighly larger in diameter and width. I'll have to think about this more. Non-straight line grip is as important as straight line performance to me so I'll have to weight the pros and cons of various combinations.
 

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I would suggest doing the weight loss mod first. You get a nice clean look while improving handling performance. Coming from the EVO community and many others, this is a hug mod done by others. I've personally cut weight on rims and tires, and definately felt a difference.
 

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I’ll just throw this out there for added discussion. Many people feel the Accord has a jittery, harsh highway ride. I am in this group. I downsized from 235/45-18s to 215/55-17s in my 6-6. The ride improved significantly and the at-the-limit handling sacrifice was minimal - almost nothing.

While that evaluation is subjective, math is not. Here’s some math that might appeal to some of you. My current OEM 17-wheels weigh about 24 lbs. and my Hankook Ventus 1 Noble2 215/55-17 tires weigh 22 lbs. This same Hankook V1N2 tire in a 235/45-18 size weighs 23 lbs.- one pound more.

That is kind of important. In order for an 18” wheel with those 23lbs tires to have the same rotational inertia as my 24-lbs. 17”-wheels with 22-lbs tires, the 18" wheel must weigh 18 pounds! Yeah. You’d need an 18-pound 18” forged wheel to spin as easily as a 24-pound 17”wheel. That extra pound of required tire weight AND the rim of the wheel spinning ½” farther from the axis has a rather large effect on rotational inertia. Food for thought.


Edit: As an additional comment directed at WhiteOrchid for his research, if we assume a 19” wheel needs 235/40-19” tires and an 18” wheel needs 235/45-18” tires, AND both tires weigh the same – which may not be true, the 19s may weigh more, the 19” wheel must weigh 24-pounds to have the same rotational inertia as the 18” 28-pound wheel. Stated another way, a 19” 27-pound wheel is equal to a 31-pound 18” wheel. And if the 19" tire weighs 2-3 pounds more (255/35-19), it gets MUCH worse!
 

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I asked the dealer who told me that the stock 18s are 29.5lbs each and the 19s are 32lbs each which make some sense contrary to what was posted earlier. I'm now looking at more lightweight aftermarket 18s instead of the 19s HFPs. The HFPs look great, but geez they are heavy.
 

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I asked the dealer who told me that the stock 18s are 29.5lbs each and the 19s are 32lbs each which make some sense contrary to what was posted earlier. I'm now looking at more lightweight aftermarket 18s instead of the 19s HFPs. The HFPs look great, but geez they are heavy.
You may find this very helpful:


16” HFP….18lbs
17” HFP….20lbs
18” HFP….23lbs.
 

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I have to wonder if the weight the dealer gave me for the 19 HFPs was the full shipping weight with box, lugs, center cap? 32lbs sounds incredibly heavy for an alloy wheel, even if it is a 19.

Watch CHH weight them:
https://www.youtube.com/watch?v=P9N7sZR80kU

Stock 18" Sport wheels are ~28#, ~53# with tire. Noted in many threads and posts on this forum.
https://www.google.com/search?q=site:www.driveaccord.net+18"+honda+sport+wheel+weight&ie=UTF-8
Duh. I responded before I watched these vids. Thanks!
 
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