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Old 12-27-2013, 11:02 AM   #1
vrracing
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Default Why no fit?



Guys, need some advice. I read RETed's wheel and tire advice pages. I ordered a set of TSW Jaramas in black for my son's Christmas present. I was going for a real racecar look, sidewalls flush to the fenders, no stretch, no 4x4 sticking out, no illegitimate camber, etc. Rolling the fender lips would be ok, pulling the fenders not. Like this...



Based mostly on RETed's pages, I ordered:

2 TSW Jarama
18X9.5 5-114.3 20GBL

2 TSW Jarama
17X8 5-114.3 40GBL

and 7/16" (11mm) spacers for the front along with ARP lug studs.

Per RETed's page with Min being flush and Max getting awfully close to the suspension bits...

For the fronts...


Rim width: Minimum offset: Recommended offset: Maximum offset:
8"---------+25-------------+30-----------------+35



Given that, we should have had the recommended offset (+/- 1mm). And yet the front wheels (no tires mounted) stuck out quite a bit - maybe 1/2" (13mm).

We thought it might be because of the unloaded suspension but even with the suspension blocked at ride height and fully loaded they still stuck out.

The rears were worst.


Rim width: Minimum offset: Recommended offset: Maximum offset:
9.5"-------+20-------------+25-----------------+30



In theory our 18X9.5 5-114.3 20GBL should have been nice and flush. But instead we got this (suspension fully compressed)...



As you can see its not even close. RETed obviously put a lot of thought and care into those suggestions and commented at length in the thread about side wall bulge. So, that suggests something is very goofy about our car. Current wheels look symmetrical side-to-side. Car has been aligned and when we bought it 2006 the CarFax was clean. Any thoughts?

We put a straight-edge against the hub (well, brake rotor face) and got the following measurements...

Front
64mm from wheel centerline to outside of fender
170mm from wheel centerline to shock

Rear
90mm from wheel centerline to outside of fender
170mm from wheel centerline to trailing arm

I'm going to use those numbers to try to calculate our the correct widths and offsets. I'm just bummed we were so off.

Thanks for sharing any insights yall might have.






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Old 12-27-2013, 11:21 AM   #2
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http://www.jegs.com/i/Percy's/760/01...FcQ9QgoddA8AEA




http://www.summitracing.com/parts/PHP-01201/


Sorry to hear about the fitment.
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Old 12-27-2013, 11:31 AM   #3
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Doing the math:

Fronts:

8" wheel = 203mm
half of 203 = 101mm
40mm offset means
61mm to outside of wheel
141mm to inside of wheel

measured distance from hubface to outside of fender = 64mm
measured distance from hubface to suspension = 170mm

So our 40mm offset 8" wheel should be 3mm inset from outside of fender and have 29mm of clearance on inside.

Rears:

9" wheel = 240mm
half of 240 = 120mm
if we switch from a 20 to 40 offset...
80mm to outside of wheel
160mm to inside of wheel

measured distance from hubface to outside of fender = 90mm
measured distance from hubface to trailing arm = 170mm

leaving 10mm both inside and out.

That all sound right?
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Old 12-27-2013, 11:33 AM   #4
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I'm starting to wonder if there are different suspension dimension out there...

Is this on an S4 or S5 chassis / suspension?
I've been talking to another guy who ordered some 8.0", +25 for fronts, and he sent pics that have the wheels sticking out a good 1/2" - 3/4" too...
I have a set of Panasport G7's that are 8.0", +27 (R32 wheels) that have no problem tucking under the front fenders...does 2mm make that much of a difference!?!?
In fact, I've used these wheels with a 5mm spacer, which effectively makes them +22 on the offset with no problem fitting under the front fenders.

Also, can you confirm the specs match the wheel dimensions?
I've heard of shops trying to pass on "wide" wheels that are not measured per industry spec; some shops are quoting *OUTSIDE* rim edge to rim edge as the "wheel width", which it's supposed to be *INSIDE* - this can add a full 1" of width to the wheel.

Also, can you measure the backspace on this wheels?
Backspacing on the fronts should be closer to 5.0"...maybe 5.5" at the most.
Backspacing on the rears should be closer to 6.0"...might be able to go 6.5" deepest.

This has me all worried, cause then my numbers are all off...



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Old 12-27-2013, 12:12 PM   #5
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For reference I run a 17x8+35 with a 245/40/17 and a 17x9+35 w/a 2552/40/17 and the fit is damn near perfect.... These are measured per BBS and Work but I have not double checked them as they fit as they should.

There isn't a difference in suspensions that I have ever noticed and I have interchanged parts from known S4's and known S5's with no ill effect at all.

I'm wondering if Ted is right and the new co's are trying to pass off the wrong size wheels in an effort to increase profits....

I have the Works off the car now and getting ready to take them to get refinished so it you guys need some measurements, let me know....

Cheers
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Old 12-27-2013, 01:10 PM   #6
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It's 90 S5 vert.

Ted, I did a couple of searches on how wheels are measured and both DiscountTire and Gemplers says its from bead seat to bead seat. That makes sense to me as the bead seat is the interface to the tire. So assuming the rim/flange is 1/2" a 9.5" wheel will have a total width of 10.5".

Of course that realization totally negates my calculations in that previous post.

Here are some shots of the front wheel measurements. My wife doesnt wait for the iPhone to focus and she wears weird socks.



TOTAL WIDTH


BEAD WIDTH


HUB TO INSIDE EDGE



And the rear

TOTAL WHEEL WIDTH


BEAD WIDTH


HUB TO INSIDE EDGE
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Old 12-27-2013, 01:20 PM   #7
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Re-doing the math...

Doing the math:

Fronts:

8" wheel with a total width of 9" = 228mm
half of 228 = 114mm
40mm offset means
74mm to outside of wheel
154mm to inside of wheel

measured distance from hubface to outside of fender = 64mm
measured distance from hubface to suspension = 170mm

So our 40mm offset 8" wheel should extend 10mm beyond the outside of fender and have 16mm of clearance on inside.

Rears:

9.5" wheel or 10.5 total width = 266mm
half of 266 = 133mm
if we switch from a 20 to 40 offset...
93mm to outside of wheel
173mm to inside of wheel

measured distance from hubface to outside of fender = 90mm
measured distance from hubface to trailing arm = 170mm

leaving 3mm jutting out beyond the fender and smashing into the trailing arm 3mm
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Old 12-27-2013, 01:29 PM   #8
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It would be interesting to compare TT's measurements of the Works.
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Old 12-27-2013, 01:29 PM   #9
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Quote:
Originally Posted by vrracing View Post
Doing the math:

Fronts:

8" wheel = 203mm
half of 203 = 101mm
40mm offset means
61mm to outside of wheel
141mm to inside of wheel

measured distance from hubface to outside of fender = 64mm
measured distance from hubface to suspension = 170mm

So our 40mm offset 8" wheel should be 3mm inset from outside of fender and have 29mm of clearance on inside.
Okay, let me add a few numbers...
On average, rim lips are usually around 1/2" or about 12mm, IME.
This is for "J" or "JJ" type rim lips.
See: http://www.carbibles.com/tyre_bible_pg4.html
(Scroll down about half way.)
I tend to add this 12mm to the (rim width)/2 + offset, and this should equal "backspace".
If this is a true 8.0" wide wheel, the we get 141mm + 12mm = 153mm.
153mm is right about 6.0".
So, your backspace on this wheel should be about that number...6.0".

I dunno where you're measuring the "170mm" number from, but if you're using stock type springs, the clearance issue is the lower perch of the front strut.
Some coilovers will interfere with the lower adjust collar or the bottom part of the spring, if you're using largish diameter springs.
Can you tell us where this 170mm measurement clearance is coming from?

At least with your fronts, you can play with a smaller / thinner spacer to get them to sink back in...
Try without a spacer and see if it'll fit?


Quote:
Rears:

9" wheel = 240mm
half of 240 = 120mm
if we switch from a 20 to 40 offset...
80mm to outside of wheel
160mm to inside of wheel

measured distance from hubface to outside of fender = 90mm
measured distance from hubface to trailing arm = 170mm

leaving 10mm both inside and out.

That all sound right?
9" = 9.0 x 25.4 = 228.6mm, try more like 230mm.
230mm / 2 = 115mm (offset = 0)
115mm + 20mm (offset) = 135mm
135mm + 12mm (rim lip) = 147mm, which is our backspace.
147mm / 25.4 = 5.7874", which is about 5-3/4", backspace
Would like this backspace more inward, but the 9.5" wide wheel shouldn't get that close to the fender lip...
I've run 9.0", +35 with easily an inch more space to spare in the rears...
Your 9.5", +20 only adds another ~18mm less clearance outward to the fender lip...
Weird.


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Old 12-27-2013, 01:32 PM   #10
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Quote:
Originally Posted by vrracing View Post

HUB TO INSIDE EDGE
Okay, this is backspacing...
...and this is for the fronts, 8.0", +40?
That looks like right around 6.0" on the tape measure...

The wheel widths are correct...


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Old 12-27-2013, 02:18 PM   #11
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So they should fit beautifully with the spacer...

The 170mm was from the straightedge on the hubface to the outmost portion of the spring. We have the half-ass psuedo coilovers. In the back the 170mm was from the straightedge on the hub to the trailing arm.
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Old 12-27-2013, 02:27 PM   #12
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Quote:
Originally Posted by vrracing View Post
So they should fit beautifully with the spacer...
Should... :P

Quote:
The 170mm was from the straightedge on the hubface to the outmost portion of the spring. We have the half-ass psuedo coilovers. In the back the 170mm was from the straightedge on the hub to the trailing arm.
Those are correct.
The rears tend to hit the trailing arm that snakes forward...

What size tires were you planning on using?

In the rears, even with a 255 / 265, the sidewall should be pretty vertical.
Some of the "curb protection" sidewall profiles might take away another 1/2" of clearance...
Bridgestones tend to have bulgy sidewalls, for example...


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Old 12-27-2013, 04:21 PM   #13
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I was leaving tire selection to the kid (and DiscountTire). I bought him the wheels, he can spring for the tires! I have Yokahama S.drives on the G35 coupe and to your point the sidewalls are pretty even with the wheels. Very square, no bulge. Same for the Hankook Ventus I have on the front.

The only other factor I can think of here is the brake rotor thickness. It essentially acts like a spacer. In yall's experience do they vary much?

I have some 18g sheet that I may make some templates based on our calculations. That'll provide a better view I think.
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Old 12-27-2013, 04:32 PM   #14
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Quote:
Originally Posted by vrracing View Post
The only other factor I can think of here is the brake rotor thickness. It essentially acts like a spacer. In yall's experience do they vary much?
That's a good point...

I do run a set of prototype BBK Wilwoods up front, but they are maybe 1.0 - 1.5mm sunken in.
This is why I need to use spacers on my fronts, but I haven't mentioned them until now.

Now, I'm assuming that the wheels are fitting flush to the face of the hub - i.e. the area where the wheel studs come out of.
That should be consistent over all the FC models...?
Can you confirm if you brake rotors are flush with the hub face?
I would think even with aftermarket OEM replacement brake rotors, it should be pretty consistent and even...


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Old 12-28-2013, 02:39 PM   #15
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FWIW my 17x9 +22 RPF1's with 255/40 tires fit the same in the rear. I have Centric slotted rotors and with -1 degree of camber I needed to roll and pull the rear fenders about 1/2 in. to clear. I have +20 mm front fenders that barely clear with -1.5 degrees of camber with the same wheels and tires. Just for reference...
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