Thoughts on a Staggered Setup?
- Thread starter Supra469
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I've got 17s front 18s rear, and along with h&r springs, my supra looks like it belongs with hotrods out of the thirties. the rake is RIDICULOUS. I hate it. I can't stand it. UGH. Its easily my biggest dislike about my car.
buckshotglass
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17s have bigger sidewalls to help with traction.. stiff short sidewalls are no good for traction.. (straight line)fstlane88 said:
doesn't turbodrifter have it staggered like that?
Sawbladz said:
A small point it would be 1/2" extra of rubber.....
But and here's the rub if you want to keep the rolling diameters the same the 17" rubber is going to be heavier than the 18" due to taller sidewalls.
255/35/18 = 635.7mm diameter = 89.3mm sidewall
255/40/17 = 635.8mm diameter = 102mm sidewall
It has to be a close call whether the rubber will outweigh the extra 1/2" of spokes in the rims
The way I figure it raking the car by reducing the wheel size up front will not impact the weight distribution much.
The weight distribution of a stock supra is about 54 / 46, the wheel base is 102.2 inches and the height of the center of gravity is somewhere around 12 inches above the hub. Then the stock center of gravity is 0.46 * 102.2 inches = 47.0 inches behind the front hub and 12 inches above it. Therefore the weight distribution of the 3,500 lb car is (102.2-47/102.2) * 3500 lb = 1,890.4 lbs on the front axle and 3,500 lb – 1,890.4 lb = 1,609.6 lbs on the rear axle.
Using the same tire profile but reducing the front wheel size by 1 inch essentially lowers the front end by 0.5 inch and moves the center of gravity 0.5*12/102.2 = 0.059 inches forward. Thus the new center of gravity is now located at a distance of 47-0.059 = 46.94 inches behind the front hub. The new weight distribution is (102.2-46.94/102.2) * 3500 lb = 1,892.4 lb front and 3,500 lb – 1,892.4 = 1607.6 lb rear. So the staggered wheels shifted 2 lbs to the front and the weight distribution is now 54.1 / 45.9.
The lowering of the center of gravity would seem to have a greater impact than the movement forward. In the case described above the center of gravity is reduced 0.5*(102.2-47) /102.2 = 0.27 inches. This is relative to the ground not the hub, which is unchanged. Typically, I would think that a lower car would handle better than a higher one due to reduced overturning moments. But perhaps the improvement may be biased towards the front or rear and overall this may make things worse. But I really don't have a clue about suspensions and leave this to someone much wiser than me to explain.
The weight distribution of a stock supra is about 54 / 46, the wheel base is 102.2 inches and the height of the center of gravity is somewhere around 12 inches above the hub. Then the stock center of gravity is 0.46 * 102.2 inches = 47.0 inches behind the front hub and 12 inches above it. Therefore the weight distribution of the 3,500 lb car is (102.2-47/102.2) * 3500 lb = 1,890.4 lbs on the front axle and 3,500 lb – 1,890.4 lb = 1,609.6 lbs on the rear axle.
Using the same tire profile but reducing the front wheel size by 1 inch essentially lowers the front end by 0.5 inch and moves the center of gravity 0.5*12/102.2 = 0.059 inches forward. Thus the new center of gravity is now located at a distance of 47-0.059 = 46.94 inches behind the front hub. The new weight distribution is (102.2-46.94/102.2) * 3500 lb = 1,892.4 lb front and 3,500 lb – 1,892.4 = 1607.6 lb rear. So the staggered wheels shifted 2 lbs to the front and the weight distribution is now 54.1 / 45.9.
The lowering of the center of gravity would seem to have a greater impact than the movement forward. In the case described above the center of gravity is reduced 0.5*(102.2-47) /102.2 = 0.27 inches. This is relative to the ground not the hub, which is unchanged. Typically, I would think that a lower car would handle better than a higher one due to reduced overturning moments. But perhaps the improvement may be biased towards the front or rear and overall this may make things worse. But I really don't have a clue about suspensions and leave this to someone much wiser than me to explain.
ive worked real world numbers on the weight difference between 17s and 18s. if you keep width and rolling diameter the same then you will save 2.5 - 3.5 lbs per wheel by using 17s.
thats fairly substantial concidering that this is both unsprug AND rotating weight.
thats fairly substantial concidering that this is both unsprug AND rotating weight.
IJ. said:255/35/18 = 635.7mm diameter = 89.3mm sidewall
255/40/17 = 635.8mm diameter = 102mm sidewall
It has to be a close call whether the rubber will outweigh the extra 1/2" of spokes in the rims
kind of a mute point for real world applications. The rubber will be heavier and more importantly, further out, so your moment of inertia will be higher with the 17's.
that said, i'd still run the 17's, I do in fact, 'cause for most racing that we do, traction is a lot more important than rotational inertia.
ofcourse the difference either way will be minute enough that the ass dyno will never pick it up.
I wouldn't do the different size set up 17 and 18. As far as staggered wheels go I am thinking of getting new wheels for my car but I am leaning towards same size wheels and tires front and back(17x9's). I think 18's staggered look really good on supras though.
Blackfin: I think you are missing the point. The car doesn't get lowered, the sidewall height changes. It has the same overall size (rolling diameter).
Screaminglemon: How did you work it out? Did you have access to 2 sets of of wheels and 2 sets of tires of the same models?
I'm also in for pics of speed dodici's car.
Screaminglemon: How did you work it out? Did you have access to 2 sets of of wheels and 2 sets of tires of the same models?
I'm also in for pics of speed dodici's car.
My first thought here is WHY?
Now for the math.
The stock diameter of the MkIII rim/tire combo is 24.9inches. When you upsize your rims you downsize your tire (sidewall) to maintain that same diameter - or else you have to change your speedo to compensate. We'll just start with the part where we don't change the speedo for now.
For a 17" rim (say a 255 width since everyone here wants wider) you need to run a 40 series tire. This will make your diameter be 25" (or 0.1" taller than stock). Your speedo will be off by 0.7% so when your speedo reads 60mph you will actually be going 60.4mph.
Now... for an 18" rim (we'll keep the same 255 width to keep this easy) you'd need to run a 35 series tire to maintain the same 25" diameter - and still be off on the speedo by the same 0.7% mentioned above.
So now I come back to the first question... "WHY?"
Now for the math.
The stock diameter of the MkIII rim/tire combo is 24.9inches. When you upsize your rims you downsize your tire (sidewall) to maintain that same diameter - or else you have to change your speedo to compensate. We'll just start with the part where we don't change the speedo for now.
For a 17" rim (say a 255 width since everyone here wants wider) you need to run a 40 series tire. This will make your diameter be 25" (or 0.1" taller than stock). Your speedo will be off by 0.7% so when your speedo reads 60mph you will actually be going 60.4mph.
Now... for an 18" rim (we'll keep the same 255 width to keep this easy) you'd need to run a 35 series tire to maintain the same 25" diameter - and still be off on the speedo by the same 0.7% mentioned above.
So now I come back to the first question... "WHY?"
Staggered setups cant hurt handling too bad being as the best handling cars in the world run staggered diameter wheels. (corvettes, porsches, ferraris?) Granted they were designed for it, i dont think a half inch rake on a Supra will totally throw off the center of gravity or weight distribution.
Well a couple people are getting it, others are missing some things. What really matters is the tire diameter. If you keep them the same or close to the same, the car will sit the same way it did before. The 17/18 stagger is more of a style choice than anything. It also depends on what tires you want to run in what sizes, on some cars the tire size you want to run might be better in a 17 rather than an 18. And then you can size the rear a little differently or however you want.
I'm also guessing most people aren't using any type of height adjustable suspension. Which would allow you to adjust the car if you have to run a tire that is 0.5 inches taller than stock or shorter or whatever.
As for the CCW road race 18/17 setup. From what I remember that was because of the tire sizes that people wanted to run and their availability. Now, there is no reason to run that setup because there are a lot more race tire offerings in 18" sizes.
As for the different weights. Do some research. A lot of tire weights are published and depending on what wheel, you can find weights for them from certain places. I know enkei has the weights of some of their wheels listed. It would at least offer some basis for comparison. Of course, this won't take into account rotational inertia, but I doubt there are many people at the point where that will really matter.
I'm also guessing most people aren't using any type of height adjustable suspension. Which would allow you to adjust the car if you have to run a tire that is 0.5 inches taller than stock or shorter or whatever.
As for the CCW road race 18/17 setup. From what I remember that was because of the tire sizes that people wanted to run and their availability. Now, there is no reason to run that setup because there are a lot more race tire offerings in 18" sizes.
As for the different weights. Do some research. A lot of tire weights are published and depending on what wheel, you can find weights for them from certain places. I know enkei has the weights of some of their wheels listed. It would at least offer some basis for comparison. Of course, this won't take into account rotational inertia, but I doubt there are many people at the point where that will really matter.
If the car is aligned correctly on all 4 wheels after fitting the staggered combo it's not going to make a difference to handling.......
Junior makes a good point about the PMoI but I doubt it would be measurable even on a real dyno
Junior makes a good point about the PMoI but I doubt it would be measurable even on a real dyno
Sawbladz said:
:nono: I got the point. Someone else missed it, headed out towards la-la land and you went with them.
Staggered wheels means different sizes (width or diameter). The original poster (Supra469) made no mention of adjusting the tire profile to keep the diameter the same. I think that would look pretty stupid anyway. I just stuck to the original post and the later comments that this would affect center of gravity.
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nosechunks said:
I am not certain about pre-1999 Porsches but 1999 and later run the same diameter front and rear.
hmm, just checked it out, i could have sworn my uncles 05 911 turbo had 19's in the back and 18's in the front, guess not though.......
No doubt the rears are definitely fatter.
I just got a screw stuck in one of the fronts today. About a 1/4 inch from the sidewall. No one could patch it because of the location and the tire shops don't plug anymore (what's up with that?) So I just bought a kit and plugged it myself. Think the tire will safely hold?
I just got a screw stuck in one of the fronts today. About a 1/4 inch from the sidewall. No one could patch it because of the location and the tire shops don't plug anymore (what's up with that?) So I just bought a kit and plugged it myself. Think the tire will safely hold?