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Old 07-23-2009, 07:22 AM   #1
MurphysLaww
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Well, I have an opportunity to pick up a high quality set of wheels that weigh in the 17lb range for pretty cheap. They look good enough to be daily drivers.

How much performance increase should I see/feel dropping from a 23-24 lb stock wheel to a 17lb wheel, and should I wait until I can afford the 14-15lb Kosei K1 ?

I think I may have gained 2lbs going from the stock 205/50/17s to the Ecsta XS 235/45/17s.

I've been thinking I may leave the XS'es on the stockers, and go to R-comps on the new 17lb'ers. Then I'd have the XS for rain tires. I'd go to 245/40's then too and pick up some more traction.

I just need to get the most bang for my buck if possible.
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Old 07-23-2009, 07:51 AM   #2
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How much performance increase should I see/feel
Marginal increase. Almost too imperceptable to measure. Sure, you're dropping 6ish lbs at each corner in unsprung weight, but you probably won't really 'feel' anything. 24ish lbs from the car in total, but unless you're already trying to eek out a 100th of a second to win the national title, it's not going to make much of a difference in time.

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and go to R-comps
This will make a bigger difference on *any* wheel than losing a little unsprung weight.

Sure, you hear many people on the internet exclaiming 'lighter wheels/tires are better', but very few are actually on the top of their game, where in addition to losing this weight, they've done almost all the prerequisite changes/modifications to the car to also lose weight.

I'm not saying it's not important... but just moving to lighter wheels alone will only make a small, finite, almost imperceptable improvement whereas grippier tires are going to make a HUGE improvement.

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Old 07-23-2009, 07:56 AM   #3
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Marginal increase. Almost too imperceptable to measure. Sure, you're dropping 6ish lbs at each corner in unsprung weight, but you probably won't really 'feel' anything. 24ish lbs from the car in total, but unless you're already trying to eek out a 100th of a second to win the national title, it's not going to make much of a difference in time.



This will make a bigger difference on *any* wheel than losing a little unsprung weight.

Sure, you hear many people on the internet exclaiming 'lighter wheels/tires are better', but very few are actually on the top of their game, where in addition to losing this weight, they've done almost all the prerequisite changes/modifications to the car to also lose weight.

I'm not saying it's not important... but just moving to lighter wheels alone will only make a small, finite, almost imperceptable improvement whereas grippier tires are going to make a HUGE improvement.

--kC
Ok, that was kind of what I was searching for, as far as deciding whether or not to pick up the 17lb'ers, as opposed to waiting for the kosei's.

It sounds like bang for my buckwise, getting the r-comps and putting them on the 17lb'ers for about a grand total W/the wheels (Kumho V710's), is going to get me farther than waiting a bit and putting out $1500-1600 to get the Kosei's with R-comps.

With the difference, I could get a set of adjustable Koni's.

And... my street tires will last longer then.
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Old 07-23-2009, 09:50 AM   #4
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It is noticeable in daily driving...mostly when pulling away from a stoplight or something like that, but I believe GRM did a test and it isn't worth any time on course, which surprised me.
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Old 07-24-2009, 12:28 AM   #5
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It is noticeable in daily driving...mostly when pulling away from a stoplight or something like that, but I believe GRM did a test and it isn't worth any time on course, which surprised me.
it was worth a small amount of time with R-comps, but on 200 treadwear street tires, the times were virtually the same.
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Old 07-24-2009, 02:20 AM   #6
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so the opinion is:

With $1500ish to spend I'd be better off with the 17lb wheels with new R-comps, and a set of Adjustable Koni's, than with just 14.5 lb Kosei's with R-comps and no Koni's ?
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Old 07-24-2009, 02:35 AM   #7
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correct
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Old 07-24-2009, 05:30 AM   #8
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ohh well, I know I'm going to pay for this with another kid (wifey brownie points), hope the kids at least cute...and smart, and scores scholarships...
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Old 07-24-2009, 08:44 AM   #9
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As someone who's bought the Kosei's this year for summer/autox use(245/40/17's on a 7" width, running 40 lbs. of air), I'll note they aren't holding up to the rigors of suburban Chicago streets. I have two bends in them already in 4 months from potholes. One I can ignore, the other needs fixing or replacement....not suprising I suppose at their cost/weight.
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Old 08-01-2009, 01:22 PM   #10
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Well, the 17lb enkei's were not the legal D-stock offset, so a no-go at that station...

The Kosei's would probably hold up for me, as they would be strictly for Autocross. That and even if they were not, we don't tend to have a lot of potholes here as the ground doesn't freeze very often and we don't have snow removal equipment running 4-5 months a year.

The wheel money just went into buying a used SPT exhaust which I'll be putting on today. The 2 1/2 inches looks HUGE compared to the stock piping. I was expecting my caliper to read 3 inches when I measured it.
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Old 08-03-2009, 02:12 AM   #11
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The lower Rotational Inertia of a lighter tire/wheel combination is really only noticeable at higher speeds. If your on a road course with speeds of 80 plus mph, then you would find a world of difference. But seeing that in autox, you hardly see the mid range of 2nd gear, a few lbs don't matter.
For whats its worth, every lb you add to your tire/wheel combo, feels like an additional 300 lbs to your car. Making a set amount of mass rotate, takes more energy than pushing or pulling said mass forward. So, big rims and massive brakes may make your car feel like its lugging around another 500 lbs.

Lighter is always better when it comes to rotating mass. Better braking, better acceleration, better suspension response.
But once that turbo spools up in 1st and 2nd, you wont notice much of a difference. After that, its well worth the investment in lighter components
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Old 08-03-2009, 07:17 AM   #12
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Originally Posted by tuskenraider View Post
As someone who's bought the Kosei's this year for summer/autox use(245/40/17's on a 7" width, running 40 lbs. of air), I'll note they aren't holding up to the rigors of suburban Chicago streets. I have two bends in them already in 4 months from potholes. One I can ignore, the other needs fixing or replacement....not suprising I suppose at their cost/weight.
There's nothing wrong with the Kosei's and EVERYTHING wrong with your streets I always chuckle when someone makes comments about wheel X not being "a good wheel" because it bent on the street after they slammed them into a few potholes. Go buy a set of Volk or Kneiss (sp?) wheels for $2-4k and drive on those same streets. You'll bend those on potholes too. Bad streets will bend any wheel, regardless of price. Kosei wheels are great because they are a) light and b) inexpensive. I've had a couple of sets , one a track set and one a daily driver set. Neither set bent in 4 years use, that's good enough for me.

PS: 245 is waaaaaaaaaaaaaaaaaaaaaaaaaaay too wide for a 7 inch wheel, you should be on a 225 max. Just because you can mount a 245 tire on a 7 inch wheel doesn't mean its going to work properly (look at VW - stretched wheels trend).
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Old 08-03-2009, 07:29 AM   #13
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For whats its worth, every lb you add to your tire/wheel combo, feels like an additional 300 lbs to your car.


Got a source for this.... comment?

--kC
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Old 08-03-2009, 11:05 AM   #14
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There's nothing wrong with the Kosei's and EVERYTHING wrong with your streets I always chuckle when someone makes comments about wheel X not being "a good wheel" because it bent on the street after they slammed them into a few potholes. Go buy a set of Volk or Kneiss (sp?) wheels for $2-4k and drive on those same streets. You'll bend those on potholes too. Bad streets will bend any wheel, regardless of price. Kosei wheels are great because they are a) light and b) inexpensive. I've had a couple of sets , one a track set and one a daily driver set. Neither set bent in 4 years use, that's good enough for me.

PS: 245 is waaaaaaaaaaaaaaaaaaaaaaaaaaay too wide for a 7 inch wheel, you should be on a 225 max. Just because you can mount a 245 tire on a 7 inch wheel doesn't mean its going to work properly (look at VW - stretched wheels trend).
Well thanks for telling me what I already know. I don't believe I called the Kosei a bad wheel, I'd buy them again. My comment was just to let a potential buyer know the wheel is susceptible to bending in harsh environments. And a 245 is fine for a 7" wheel for my primary purpose of my summer wheels as I stated, autox. I thought my post had these caveats. Oh, and I've never bent any of my stock wheels on my streets.

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Old 08-03-2009, 11:08 AM   #15
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Well thanks for telling me what I already know. I don't believe I called the Kosei a bad wheel, I'd buy them again. My comment was just to let a potential buyer know the wheel is susceptible to bending in harsh environments. And 245 is fine for 7" wheel for my primary purpose of my summer wheels as I stated, autox.
Here's a general rule of thumb when looking at wheels...

Pick any 2:
A) Strong
B) Light
C) Inexpensive

--kC
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Old 08-04-2009, 11:55 AM   #16
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I went from 27lb stockers on the 08 STi down to 17lb Volks and I could tell a huge change in the car. But it also changed the offset at the same time moving the wheels out from center giving me a wider stance, so it really changed acceleration and handling. And the acceleration part the starter at the last autox can attest to. Before I would take off out of the hole at 4k and just cherp the tires, this last time with the new wheels was a Ken Block style AWD burnout...... haha, not what I expected.
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Old 08-04-2009, 12:32 PM   #17
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I went from 27lb stockers on the 08 STi down to 17lb Volks and I could tell a huge change in the car. But it also changed the offset at the same time moving the wheels out from center giving me a wider stance, so it really changed acceleration and handling. And the acceleration part the starter at the last autox can attest to. Before I would take off out of the hole at 4k and just cherp the tires, this last time with the new wheels was a Ken Block style AWD burnout...... haha, not what I expected.
I noticed the same thing, but it was due to added traction for the most part for me. When I started the race in the 205x50's I got a good chirp, but with the 235x45's Ecsta XS'es, which also weighed 3lbs more, I got pretty much just a bunch of bog. I had to go up 500 rpm at the start to really feel like I was launching it. Adding the SPT catback, seemed to eliminate a good bit of the bog, amazingly to me.

I'm kind of interested now, because at a long course this weekend, I was just a few secs off of the ESP cobra, and the two STU STi's, not driven by Vitek B. I'm wondering how much I could pick up with really light wheels, and R-Comps. I was ahead of the 09' WRX, but he was on the stock 225 tires I think. I probably could have made some shifts to 3rd, to stay in the power a bit better, but it wasn't evident enough to warrant risking the tranny with my novice shifting.

I actually rode with Vitek this race, and OMG that was violent. I did see a couple places that I think I could have picked up some time by how he was hitting some corners.

Ohh, and Vitek uses the Kosei K-1 on his highly prepped STU Sti. That's pretty much good enough for me. It's close to 10lbs per wheel for me, so I think I'll just wait now and save for these. This last race proved to me I really need a separate set of wheels for racing.

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Old 08-04-2009, 01:25 PM   #18
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If you aren't on R tires in an R tire class those will definitely make a huge difference. Lighter wheels can't hurt, but the tires are such a major change you will notice that much, much more.
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Old 08-04-2009, 03:37 PM   #19
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Originally Posted by d'cheat View Post
For whats its worth, every lb you add to your tire/wheel combo, feels like an additional 300 lbs to your car.

Totally negatory.




1 lb at 22" diameter at 60mph has the same amount of kinetic energy as 60 lbs moving in a straight line at 60 mph. The relationship goes towards 1:1 as your speed decreases. So accelerating that wheel to 60 will feel like you've added another 60 lbs to the car, but most of that feeling will be at the end where power becomes more interesting than torque.


I just did the math and saved my firefox session in case anybody is interested. I'm going out for a skateboard.



EDIT: I did funny math. Disregard these numbers.

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Old 08-04-2009, 03:47 PM   #20
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Totally negatory.




1 lb at 22" diameter at 60mph has the same amount of kinetic energy as 60 lbs moving in a straight line at 60 mph. The relationship goes towards 1:1 as your speed decreases. So accelerating that wheel to 60 will feel like you've added another 60 lbs to the car, but most of that feeling will be at the end where power becomes more interesting than torque.


I just did the math and saved my firefox session in case anybody is interested. I'm going out for a skateboard.
Who is auto-crossing on 22" rims?

17-18" wheels are more realistic, and that measures the bead. Most of the rim is going to be at a smaller diameter than the bead. Plus, not all the weight savings on a light rim is in the outer rim. A lot of it is going to be on the face of the wheel and the hub mounting.

Modified's test (or was it in SCC before they went under?) had a lot of issues, but it did pretty conclusively show that there are a LOT more important variables than wheel weight.

-Mike
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Old 08-04-2009, 05:16 PM   #21
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Who is auto-crossing on 22" rims?

17-18" wheels are more realistic, and that measures the bead. Most of the rim is going to be at a smaller diameter than the bead. Plus, not all the weight savings on a light rim is in the outer rim. A lot of it is going to be on the face of the wheel and the hub mounting.

Modified's test (or was it in SCC before they went under?) had a lot of issues, but it did pretty conclusively show that there are a LOT more important variables than wheel weight.

-Mike
I don't know about you, but I run tires on my wheels...
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Old 08-04-2009, 09:44 PM   #22
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but it did pretty conclusively show that there are a LOT more important variables than wheel weight.

-Mike

Oh, believe me, i concur. I was just setting the record straight on exactly how much it matters (or doesn't matter). I doubt there is that much variation in wheel weight out that far, but wouldn't be surprised if there IS that much variation in tire weight. Also, switching up a size in wheel could very well have that large an impact.

I think having an extra couple hundred pounds of inertia in a 3200 pound car is going to have pretty minimal effect on laptimes unless you're already at the edge of what you can do. After all, a lot of people don't bat an eye at taking on a passenger.
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Old 08-05-2009, 12:55 AM   #23
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I don't know about you, but I run tires on my wheels...
But the thread is asking about differences in wheel weight, not differences in tire weight.

-Mike
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Old 08-05-2009, 07:34 AM   #24
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I went from 27lb stockers on the 08 STi down to 17lb Volks and I could tell a huge change in the car.
Did you keep the same tires? My guess is going to be no. Grip/compound > weight.

Quote:
But it also changed the offset at the same time moving the wheels out from center giving me a wider stance, so it really changed acceleration and handling.
Offset does not effect acceleration, but it does effect handling. This is why you're limited in stock to how much an offset away from stock you're allowed.
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Old 08-05-2009, 07:38 AM   #25
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But the thread is asking about differences in wheel weight, not differences in tire weight.

-Mike
Wheel can also be a combination of wheel/tire. They're all related. It's all unsprung weight that needs to be delt with. Also, that comment was more towards your comment regarding rotational inertia... the tire plays a much greater part in the calculations than the wheel does.

I get what you're saying that the wheel mass, with more towards the center on almost every wheel is the same, just 1" or 2" out. I very much agree with that and is why I've been saying that just changing a wheel makes a negligible difference.

However, if you go from, a 16" to a 17" wheel most of the weight has been moved out an inch (or more technically, 1/2" from the hub), and the wheel is usually wider at that, so generally it is moving more weight towards the outside of the wheel.

Add onto that the tire you put on it plays a bigger part with it's weight because one generally keeps almost the same rolling diameter as stock, it's more to the outside of that same rolling diameter. Where a taller profile 16" at 22lbs had a sidewall of 3" (all examples here) the 17", wider, lower profile tire, which usually weighs more (around 1-2 lbs more on average), has more weight to the outside via the wider tread, with less a sidewall of 2.5".

--kC

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