Boss 302 tire setup on GT question

dre256

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I need 2 new tires soon. I have brembo brake wheels (track pack) there 19x9. Right now am running square setup stock 255/40/19s. Thinking on the rears going Boss 302 setup of 285/35/19s from the 255s as I need a bit more traction, leaving 255s alone upfront.

Here is my question, all the searches I can find say the 285/35s will fit the 19x9. But if they fit the 19x9s, why did for spend extra money to put 19x10s on rear of the Boss 302? Is it better to spend the extra money and get a set of wheels 19x9 up front and 19x10s for the rear? OEM factory wheels are already quite heavy for what they are at like 31 pounds each. This is why am a bit confused if 19x9 is fine for a 285/35, why Ford spend extra money and weight on 19x10s in the rear? I just want to do the job correctly and tires and brakes are the most important thing on a car! Am not sure I should look into new wheels or save the money and am way over thinking it and 19x9s are fine.

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RocketcarX

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Tire width will have less affect on traction than rubber compound. I would look into a high performance tire, a 285 is pushing the limit of what will fit a 9 inch wide wheel.
 

dre256

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Tire width will have less affect on traction than rubber compound. I would look into a high performance tire, a 285 is pushing the limit of what will fit a 9 inch wide wheel.


I agree on the compound, last tire change I went to Michelin super sport Xls. Huge difference over the stock Goodyears. Don't think they make XLs anymore on super sports so have to go to the new Michelin 4s. Not sure there is to many better street tires to choose from, I can do 1.93 60 foot on them. Just on my last batch of upgrades and retune a few weeks ago am really starting to break the tires free and think might have out grown a 255 in the rear. But am open to hear from anyone about a better tire also to stick with a 255.

That's what I was curious about, I thought 285 might be pushing the limit of a 9 inch wide wheel. Other searches on other forums and people run them but have me concerned.
 

RocketcarX

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I daily my car on drag radials, pretty much the only option for real traction on the street.
 

RocketcarX

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What tire size do you run and the brand if you don't mind
I have two sets of 15x10 Race Stars. My daily set up is the Nitto 555r drag radial in a 275/60/15. For the track/racing I have the same wheels with Mickey Thompson ET Street R drag radial in the same size.
I run my factory wheels up front with 245/45/18 Michelin Primacy MXM4

I suspect our cars have different purposes though, lol
 
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dre256

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Thanks! An idea lol. My car isn't really a daily driver. More like weekends out for drives and track like 5 times a year. So something little more extreme like that I could look at it as an option. As winter in NJ, never comes out in bad weather and I have a set of winter tires/ wheels for the colder temps. Not buying anything right now, trying to get info so in next few weeks can make a good decision.
 

stevbd

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Go to tirerack.com and click on the specs for your tire. The "rim width" column tells you the minimum and maximum size rims you can use to mount the tire. To actually make it drive and turn well though, with good turn in, look at the "tread width" column. You want the tread width of the tire to be either the same width as your rim or up to 1/2 inch less. That's why 19x10 is the preferred size for the 285 width tire you are looking at. If you don't care about the turning part you can use a narrower rim, but I think 9" is too narrow for a 285 in any event. Good luck.
 

Norm Peterson

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I don't think you're going to find 9" wide wheels being OK'ed for 285/35 or 285/40 tires in any diameter. 9.5" is the smallest width I remember seeing for those sizes anywhere.

I imagine that Ford went to 10" wide for a little help in keeping people out of throttle-induced oversteer exiting corners on some throttle. On 9's, 285/xx's might feel a little "loose" into and out of the corners and not giving you quite as stuck-down of a feeling as you think you should be getting.


Norm
 

oldVOR

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Since you do track the Mustang, I'd recommend going with a 10" square setup, either 18x10 or 19x10, both sizes have several tire sizes available to suit more street or more track orientation.
 

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Since you do track the Mustang, I'd recommend going with a 10" square setup, either 18x10 or 19x10, both sizes have several tire sizes available to suit more street or more track orientation.

This. Don't even mess with anything smaller than a 10" wide rim on the rear. I'd suggest 10" square setup too, then you can rotate. Then use 285's on all 4 x corners. Then it will steer, corner, stick, brake etc. Even 275's on 10" rims works superb, esp on the front. A 275 on a 10" rim is stretched 1/2" above its 9.5" measuring width. Measuring width on a 285 is 10"..and min is 9.5". Being able to rotate is major plus, depending on the application.

What year and rwhp is your car ?? What track are you talking about, autoX, drag strip, or road course ?
 

dre256

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This. Don't even mess with anything smaller than a 10" wide rim on the rear. I'd suggest 10" square setup too, then you can rotate. Then use 285's on all 4 x corners. Then it will steer, corner, stick, brake etc. Even 275's on 10" rims works superb, esp on the front. A 275 on a 10" rim is stretched 1/2" above its 9.5" measuring width. Measuring width on a 285 is 10"..and min is 9.5". Being able to rotate is major plus, depending on the application.

What year and rwhp is your car ?? What track are you talking about, autoX, drag strip, or road course ?


Thank you all for your help! I didn't know 10 inch would fit up front as generally looking says 10 inch is rear only. That would be a great idea could fit 10 inch all the way around then could rotate them.

My car is a 2013 with the auto. I go to the drag strip handful of times a year. My RWHP was done on same mustang dyno. I was 363 RWHP when I was running a constant 12.5 @ 112, once in awhile on cooler days could do 12.4 @ 114. Few weeks ago I added a PMAS 120mm CAI, X pipe and retune and went to 383 RWHP. I have not been back to the track since doing that stuff a few weeks ago.
 

Pentalab

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A LOT / most 10" wide wheels will say... " rear only". They all fit the front just fine. What you have to worry about is whether they will clear the Brembo brake package. Even then, most 10" wide rims ( but not all) will clear the 14" front rotors. Forgestar CF5's..and also F14's will clear the 14" front rotors with their 18" diam wheels. IE: 18x10

If using a 19 x 10 wheel, there should be even less of an issue clearing the 14" rotors. I don't know many 19" rims that won't clear the 14" brakes. There is a whole slew of both 18 x 10 and 19x10 wheels that will clear your brembo front brakes.... even though they put a disclaimer on there..saying.. 'rear only'.

Typ ideal offset (ET) for the fronts is 42mm. 42 /45 mm offset is typ of a 18x10 and 19x10 wheel. IF you have a tiny clearance issue on the front, a small 3mm spacer can be used to decrease the offset by 3mm. The bigger the offset, the more INboard the wheel resides. Smaller offsets will result in wheel sitting more outboard.

Ask,or use the search eng to find which 19 x 10 rims will fit the front of your 2013...and clear the Brembo brakes. Very few will not clear, due to their spoke design, like bullitts, with their deep dish design, and spokes terminating well in from the edge.
 

dre256

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Typ ideal offset (ET) for the fronts is 42mm. 42 /45 mm offset is typ of a 18x10 and 19x10 wheel. IF you have a tiny clearance issue on the front, a small 3mm spacer can be used to decrease the offset by 3mm. The bigger the offset, the more INboard the wheel resides. Smaller offsets will result in wheel sitting more outboard.

Ask,or use the search eng to find which 19 x 10 rims will fit the front of your 2013...and clear the Brembo brakes. Very few will not clear, due to their spoke design, like bullitts, with their deep dish design, and spokes terminating well in from the edge.

Thank you for the offset information! I never understood the offset number is based off of to clear the brembo brakes. One set of wheels am looking at are Shelby super snakes as they look very similar to the brembo brake wheels I currently have as I like that style. Says the offset is +37mm, if I understand your post correctly, since its smaller than the 42mm they should clear. Says back spacing is 177mm
 

oldVOR

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Offset is the distance off of the true center line of the wheel to the actual mounting face.
If the mounting face was located on the center line of the wheel, the offset would be zero.
If the mounting face is moved closer to the outboard side of the wheel, the offset becomes a positive number. (in days gone by, this relates to greater back-space or less dish on the front face of the wheel).
If the mounting face is moved closer to the inboard side of the wheel, the offset becomes a negative number. (in days gone by, this relates to less back-space or greater dish on the front face of the wheel).

What determines caliper clearance is a combination of wheel design (more so the back-side of the wheels spokes) and offset. Typically, wheels of the same design with more positive offset will have a thicker mounting pad and this alone creates caliper clearance.

Another concern with more positive offset wheels is the clearance to hard parts like struts, shocks, inner fenders, frame rails, etc.
 
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Norm Peterson

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This ↑↑↑
Thank you all for your help! I didn't know 10 inch would fit up front as generally looking says 10 inch is rear only. That would be a great idea could fit 10 inch all the way around then could rotate them.
Most of the wheel sources are very conservative in their recommendations. They have to be so they don't have to deal with too many returns and bad publicity when customers don't do enough homework before ordering.

Even wider than 10" is possible if you don't mind a little sidewall 'poke'.


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Norm
 

GLOCKer

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What BOSS 302 wheel are you referring to? I'm running BOSS 302 wheels on my car; I coul dbe wrong but I thought the fronts are 9" wide and the rears are 9.5" wide. I'm running the 285 out back on those 9.5" wheels.

29982766_10160512136480107_3640977013779698185_o.jpg
 

Gabe

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285/35 is too wide and it has too short a sidewall to go on a 19x9
Yes, there are lots of people out there that run that combo, it certainly doesn't make it right.
I've run 19x10's on the front with a 275/40/19 tire, awesome fitment. No bulge, no stretch, the tire fit perfectly square onto the wheel.
I've also run 305/35/20 on 20x10 rear wheels, and yes it fit, and yes the tire bulged. Actual contact patch was about 275-285.
Currently running 18x9.5 all around, 285/40/18 front tires (perfect fitting tire), with 305/40/18 rear tires. Not a perfect fitment but the 40-series sidewall "forgives" some of that sidewall bulge and because it's on the back, it works ok.
Contact patch is not 305, more like about 285.
My next set of rear tires will be 285's.

On the factory Brembo wheels, the fattest tire I'd run on the back is a 275/40/19
 

dre256

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285/35 is too wide and it has too short a sidewall to go on a 19x9
Yes, there are lots of people out there that run that combo, it certainly doesn't make it right.
I've run 19x10's on the front with a 275/40/19 tire, awesome fitment. No bulge, no stretch, the tire fit perfectly square onto the wheel.
I've also run 305/35/20 on 20x10 rear wheels, and yes it fit, and yes the tire bulged. Actual contact patch was about 275-285.
Currently running 18x9.5 all around, 285/40/18 front tires (perfect fitting tire), with 305/40/18 rear tires. Not a perfect fitment but the 40-series sidewall "forgives" some of that sidewall bulge and because it's on the back, it works ok.
Contact patch is not 305, more like about 285.
My next set of rear tires will be 285's.

On the factory Brembo wheels, the fattest tire I'd run on the back is a 275/40/19

Yes as I am seeing here people running 285s on a 9 inch wheel isn't right. Thank you also on letting me know your running 10 inch wide in the fronts with no problems! I am leaning towards 10" all the way around now. Be much easier being able to rotate if needed and just 1 size to worry about in a flat tire issue.


What BOSS 302 wheel are you referring to? I'm running BOSS 302 wheels on my car; I coul dbe wrong but I thought the fronts are 9" wide and the rears are 9.5" wide. I'm running the 285 out back on those 9.5" wheels.

I could be wrong but I believe Boss 302 wheels are 9inch in the front and 10 in the rear?
 

Gabe

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The black 2012 Boss302 wheels were 19x9 front, 19x9.5 rear:

boss302_2012.jpg



The 2013 Boss302 wheels were 19x9 front, 19x10 rear:

M-1007KIT-DC199LGB.jpg
 

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