Wheel discussion (From 818 Open House Pics Thread)

[Frank818]

Ok so my thinking was right.
I can't believe RaceLogic wouldn't allow a diameter difference, it's widely used for various applications, they certainly cannot impose same size everywhere. Another thing I'll try to confirm.

Duh, well after googling around I found a post from 2004 that says RLTC uses tire size setups, tire diameters and car speed to figure out if the wheels spin over your pre-set allowable slip %.

Some people changed tire front and rear for street vs track and it changed the proportional setup without causing any issues. But it is configurable.




Note to self for later % difference calculations: 255/35-18F and 285/30-18R street vs 245/45-17F and 275/40-17R track, no difference in RLTC management.

[Jim Schenck]

Frank,

The white car fitment is a little different because it has 18x8.5 instead of 18x9.5. The wheels on that car are 42mm offset and give about 3/8 clearance, but on a wider wheel you would lose a bit of that, even with the same size tire.

[Frank818]

On the S?
The S uses 255/35/18 as well or different size?

[Jim Schenck]

same rear size tires on both, 255/35/18

[bnr32jason]

I think there was a discussion before, but I can't find it.....

You may (or may not) have trouble squeezing something like a 285 street tire onto the 818.

The R for track testing has been running 18x9 +40 if I remember correctly. This was on a 255mm Hoosier slick and you can see how the wheels and tires are already poking out of the rear. Of course slicks run a little wide, but someone (maybe Wayne?) mentioned that on this setup there was VERY little inner clearance left to the suspension parts. So you may have modify the fenders a bit and run a lower offset wheel if you want to fit tires that wide.

[Wayne Presley]

It has Hoosier R6 tires in 255/35-18 which if you look at the tire data you'll see it's really just as wide as every other 275.

[Frank818]

run a lower offset wheel if you want to fit tires that wide.

Hmmm, increase the offset, no? If you lower the offset, the center of the wheel will be shifted towards the inside, which will push outside the rim.

[bnr32jason]

Hmmm, increase the offset, no? If you lower the offset, the center of the wheel will be shifted towards the inside, which will push outside the rim.

Lower offset.

Assuming you keep the wheel width the same going from a 40mm to 30mm offset would give you 10mm more inner clearance because it would push the wheel outwards by 10mm.

[Frank818]

Lower offset.

Assuming you keep the wheel width the same going from a 40mm to 30mm offset would give you 10mm more inner clearance because it would push the wheel outwards by 10mm.

Exactly. to do so the center of the rim is located closer to the inside (closer to its center), so it pushes out the rim and tire. Since the tires are already rubbing on the fender, running a lower offset would make it rub more, but will clear out the inner side where the suspension is.

[Wayne Presley]

Since the tires are already rubbing on the fender, running a lower offset would make it rub more, but will clear out the inner side where the suspension is.

Only the R rubbed with overly wide 255/35-18 hoosiers, they would be a 275 in any other tire based on tread/section width...

[philly15]

out of curiosity does anyone have the alignment specs from the cars at the open house?

[bnr32jason]

Exactly. to do so the center of the rim is located closer to the inside (closer to its center), so it pushes out the rim and tire. Since the tires are already rubbing on the fender, running a lower offset would make it rub more, but will clear out the inner side where the suspension is.

That's why I said you would need to modify the fender too. I don't think there is much clearance left inside, so your only option if you want to run a crazy tire setup is to run a lower offset wheel and modified fenders (flares maybe?).

[Frank818]

Yes. I don't think FFR designed the car for 305s anyway.

My goal is to drive a crazy car rather than a crazy tire setup. I think no matter what we do, the car will be crazy.

[metalmaker12]

38 offset is prob the lowest you can go before you rub the quarters. I will be running 18x9.5 38-45 offsetout back and 17x8 40-45 offset, rota, rays, enkis or something

[Wayne Presley]

out of curiosity does anyone have the alignment specs from the cars at the open house?

Yes

[metalmaker12]

Well Wayne what are the specs

[Silvertop]

Well Wayne what are the specs

Not unless you know the secret handshake.

[Frank818]

38 offset is prob the lowest you can go before you rub the quarters. I will be running 18x9.5 38-45 offsetout back and 17x8 40-45 offset, rota, rays, enkis or something

But on the R the R6s which are almost 275 large with a 35 offset where slightly rubbing, they said. So if you take 35 offset on real 255s, maybe it's going to work. Maybe...

[bnr32jason]

But on the R the R6s which are almost 275 large with a 35 offset where slightly rubbing, they said. So if you take 35 offset on real 255s, maybe it's going to work. Maybe...

The 818R that has been tested runs a 9" wide wheel so the offset of a 9.5" wide wheel is different. If you run a 7" wide wheel on the rear you could run a +10 offset if you really wanted to. Remember offset is only a part of the equation, wheel width is the other part.

[rori]

My wheel choice comes in an 18x9.5 +40 for the rears.

For the fronts I have a choice of 18x8.5 +45 or 18x7.5 +40.

What would you choose/suggest for the fronts?

[bnr32jason]

Depends what size tires you want to run. If you are sticking with a 215 or 225 I'd go with the 7.5's. If you are running a 235 or 245 go with the 8.5

[Frank818]

The 818R that has been tested runs a 9" wide wheel so the offset of a 9.5" wide wheel is different. If you run a 7" wide wheel on the rear you could run a +10 offset if you really wanted to. Remember offset is only a part of the equation, wheel width is the other part.

Darn right!!! I totally forgot about the 9".

Anyone knows the offset difference between 2 wheels that have 0.5" width difference in order to keep the center of the wheel at the exact same place?

I don't know if you understand why I mean.


Ok found this from someone here : http://www.1010tires.com/Tools/Wheel-Offset-Calculator

[Stickshift84]

All of my assumptions so far are to the rear wheel. The most extreme fit from F5 is an 18x9.5 with a +35mm offset and a 255/35-18 tire. This means the wheel sits (9.5/2)-(35/25.4)" or 3.37" outside of the hub. If you want to run a 255/35-18 tire the maximum offset to push the wheel to the outside is a +35mm in keeping with the F5 recommendations. That offset remains whether the wheel is 8.5", 9" OR 9.5" wide when keeping the same 255 series tire. If you want to run a narrower tire the offset could increase. For every 0.4" of tire width decrease the offset could increase by 5mm ( in this case to a +30mm wheel). Hope that helps.

[Frank818]

Very valuable, tnx!

Can the same calculations be applied for the front wheel? I mean to remain within F5 recommendations for the front.

[bnr32jason]

All of my assumptions so far are to the rear wheel. The most extreme fit from F5 is an 18x9.5 with a +35mm offset and a 255/35-18 tire. This means the wheel sits (9.5/2)-(35/25.4)" or 3.37" outside of the hub. If you want to run a 255/35-18 tire the maximum offset to push the wheel to the outside is a +35mm in keeping with the F5 recommendations. That offset remains whether the wheel is 8.5", 9" OR 9.5" wide when keeping the same 255 series tire. If you want to run a narrower tire the offset could increase. For every 0.4" of tire width decrease the offset could increase by 5mm ( in this case to a +30mm wheel). Hope that helps.

I'm completely confused by what you posted here. Tire size doesn't have anything directly to do with offset, am I misunderstanding what you are trying to say.

Lets take an example:

18x8.5 +35 offset wheel is the baseline
18x9 +35 outer position of the wheel extends 6mm and you lose 6mm of inner clearance as well
18x9.5 +35 outer position of the wheel extends 13mm and you lose 13mm of inner clearance.

Are you saying as long as we run a 255mm tire, that a 18x8.5 +35 will work exactly the same as a 18x9.5 +35? I think I must be misunderstanding.

[Stickshift84]

The offset only shifts the center of the wheel which has the same effect as shifting the center of the tire. A 255 series tire fits flush or outside the maximum to F5 specs with a +35 offset. Tire width will only vary a small amount when mounted on different width wheels.

Does anyone know the FRONT wheel width and tire size that F5 recommends for just fitting within the fenders?

[metalmaker12]

Wow nick you made more than one post lol, lets just wait and see what people put on and just use the stock rims until then

[rori]

My wheel choice comes in an 18x9.5 +40 for the rears.

For the fronts I have a choice of 18x8.5 +45 or 18x7.5 +40.

What would you choose/suggest for the fronts?

Depends what size tires you want to run. If you are sticking with a 215 or 225 I'd go with the 7.5's. If you are running a 235 or 245 go with the 8.5

I'm more worried about being able to fit the 8.5". That would be my first choice. I'm having trouble finding specs on what was on the FFR builds. Most discussions seem to focus on the rears.

[Wayne Presley]

The R had 8 fronts and 9 rears.

[bnr32jason]

The offset only shifts the center of the wheel which has the same effect as shifting the center of the tire. A 255 series tire fits flush or outside the maximum to F5 specs with a +35 offset. Tire width will only vary a small amount when mounted on different width wheels.

So you are saying a 255mm width (not series) tire will sit in the exact same spot regardless of wheel width as long as it's a +35 offset?

[bnr32jason]

I'm more worried about being able to fit the 8.5". That would be my first choice. I'm having trouble finding specs on what was on the FFR builds. Most discussions seem to focus on the rears.

I don't see any need to run a 8.5 up front anyways. There may be fitment problems and there may not, we'll have to wait to see a couple builds that experiment with different wheel combinations. I'm going to be running a 17x7.5 up front and 18x9 in the rear just to be safe. The only thing I may need to do is run a spacer in the front since my 17x7.5 wheels are +50, but I'm hoping they will look fine.

[Frank818]

So you are saying a 255mm width (not series) tire will sit in the exact same spot regardless of wheel width as long as it's a +35 offset?

Yes, if the wheel offset calculator on internet is right.
I am not on my computer right now but someone posted the link.
Reason for that is if you add 1 inch, you add half of it on each side, therefore the tire remains in the spot.
The fact is the 1 inch more added is independent to the offset it is relative to the real center of the wheel.

[Kooldaddy]

Am I missing something? Has anyone thought of the modular wheels out there? And I think as long as everyone here on the forum wants fatter, stickier rear tires, that wider rear fenders need to be an option or at least some sanitary and not labor intensive flairs?
i know I want as much grip as I can get front and rear, that means wider stickier tires all around. I am a T type personality and need the adrenalin rush of fast (used to race high horsepower bikes). I am a late/trailbraker, early power on kinda guy.
KD

[Silvertop]

Am I missing something? Has anyone thought of the modular wheels out there? And I think as long as everyone here on the forum wants fatter, stickier rear tires, that wider rear fenders need to be an option or at least some sanitary and not labor intensive flairs?
i know I want as much grip as I can get front and rear, that means wider stickier tires all around. I am a T type personality and need the adrenalin rush of fast (used to race high horsepower bikes). I am a late/trailbraker, early power on kinda guy.
KD

Actually, I don't think everyone here on the forum DOES want fatter, stickier tires. Many do, of course, and those that do have a tendency to show more, um, ENTHUSIASM for that than some of the rest of us, who are just building our street toys with less grandiose intentions. But the 818 as designed has room for plenty of rubber under the fenders, while still being aesthetically OK for slightly less aggressive tire/wheel sizing. But it's a kit. Build it your way.

[Kalstar]

Is anyone sticking with the 16" in an aftermarket wheel? I am thinking about it but is it too small?

[Silvertop]

Well, too small for what? There are certainly 16" wheels available that will work on the car. And there are certainly no shortage of high performance tires that will work. Can you get the 16's in the width you want? You will need to look at 16" tire width availabilities to make sure you can get what you want there too. They will need to be higher profile -- probably 50 or 55 series depending on the width -- but it is doable. Depends mostly on the look you are going for, and the tire (and wheel) width available and desired. Beyond making sure you can get the tire size you want, its mostly a matter of personal preference. But I'm sure you know all of that.

Personally, I don't think 16's are too small. I'll be using 16's -- the stock Subie wheels. Of course, I like the look of a slightly higher profile anyways, and I don't feel the need to run really wide tires. And I just don't feel like spending $1000 on a set of wheels. I have already found way too many places on this car to spend extra $1000s of dollars............

If I WAS going to go with aftermarket wheels, I would look at 16's -- though I might also consider 17's. I don't think I would go to 18's. Just my preferences

[Kalstar]

Well, too small for what? There are certainly 16" wheels available that will work on the car. And there are certainly no shortage of high performance tires that will work. Can you get the 16's in the width you want? You will need to look at 16" tire width availabilities to make sure you can get what you want there too. They will need to be higher profile -- probably 50 or 55 series depending on the width -- but it is doable. Depends mostly on the look you are going for, and the tire (and wheel) width available and desired. Beyond making sure you can get the tire size you want, its mostly a matter of personal preference. But I'm sure you know all of that.

Personally, I don't think 16's are too small. I'll be using 16's -- the stock Subie wheels. Of course, I like the look of a slightly higher profile anyways, and I don't feel the need to run really wide tires. And I just don't feel like spending $1000 on a set of wheels. I have already found way too many places on this car to spend extra $1000s of dollars............

If I WAS going to go with aftermarket wheels, I would look at 16's -- though I might also consider 17's. I don't think I would go to 18's. Just my preferences

Thx for the reply. I found some new inexpensive 16" wheels I like. They are 16.3 lbs each and only 117.00 each. I also found stock fitment 205/55/16 Hankcook V12 (highly rated and one of the lightest tires in the industry) for 81.00 each. Mounted and balanced ready to install for less then 800.00 for the whole package. They look great, inexpensive and light. Just didn't know if they would look too small.

[07FIREBLADE]

One thing to keep in mind though if you run the 16in wheel. You limit yourself on brake options in the future.

[Silvertop]

Thx for the reply. I found some new inexpensive 16" wheels I like. They are 16.3 lbs each and only 117.00 each. I also found stock fitment 205/55/16 Hankcook V12 (highly rated and one of the lightest tires in the industry) for 81.00 each. Mounted and balanced ready to install for less then 800.00 for the whole package. They look great, inexpensive and light. Just didn't know if they would look too small.

You might want to try the 205-55's on the front only, with 225/50's for the rear. The 225's will likely fit the wheels you are looking at, unless they are very narrow -- less than 6 inches wide. Given the weight balance of the 818, that combination would be likely to give you a more neutral grip. The overall height will be the same -- nominally 25 inches. Which, if you check, will about the same overall height as the 17's and 18's that other builders are running. You won't quite fill the wheel wells horizontally though -- might be about an inch or so inboard of the fender edges. But if this bothers you, you can always add some wheel spacers..........

Regarding 07Fireblade's note about potential brake limitations -- I suspect he's right about that. But it will come down to how much brake you think you are going to need. Unless you plan to go racing, the stock brakes should be more than adequate-- even for track day events. It seems to me that a stock brake system that was meant to do a good job stopping a 3100 lb car is going to have EXCEPTIONAL stopping power on a car that only weighs 1800 lbs. Just my .02

[Scargo]

I'm wondering what FFR thinks now that they may be upping the horsepower on the race car? Jason told me the driver thought it could handle some more horsepower. Wasn't that fast on WGI back straight. I'm thinking of starting at 400 WHP on my pure racer.
If the tires were rubbing on the inside at the rear it must have been the coils, near the top? Couldn't the tops of the shocks move in a little? I don't mind doing rear flares.
What I am considering is 17x8.5 with 38+ offset and 18x9.5~10 with 38+ offset. Undecided on tires but am thinking 275x35x18 Hoosiers for the rear. Not much difference in section width between them and 255s.
I am thinking I may want 18s on the front so I can run a Stoptech 355 mm BBK on the front. Crazy?