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Cobra rims on FiST

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Location
Indio, CA, USA
#1
Hello all,
Im trying to wide body my fiesta, but on a budget.
Ive come across cobra rims with the same bolt patten and low offset. Im really interested as to what wheels will fit. Im still trying to understand what back spacing is, and how low or high of back spacing will fit the 2016 fiesta ST's
Ive put some screen shots of rims that i was looking at, will any of them fit??

Thanks 🏎🏎
 


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Location
Wichita, KS, USA
#2
You should probably explain what "wide body on a budget" means exactly, because 10" wheels are going to take some hacking to fit.
 


SteveS

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#4
Offset and backspacing refer to the same thing, but measured from a different place. Offset is the distance from the center of the wheel to the plane of the mounting surface, measured in millimeters. If the number is positive, the mounting plane is closer to the outside (pretty side) of the wheel. If the number is negative, it's closer to the backside.

Backspacing is the older way of measuring this and has largely been abandoned. In backspacing, the distance from the inside wheel rim to the mounting surface is measured, usually in inches.

The wheel you are looking at has a 25mm positive offset, which is an inch. The backspacing for that should be 6". The fact that it's 6.48" comes from the fact that they have a little bit of flange thickness to the rim they don't include in the 10" width designation.

In comparison, the stock FiST wheel has a width of 7" and offset of 47.5 mm. 47.5 mm is 1.87". So the backspacing is 3.5" + 1.87" = 5.37", plus a little for the thickness of the rim. So this wheel will go one inch farther towards the shocks at the rim, and three inches farther out. Therefore the tire mounted on it will bulge another half inch or more than that each way. So the issues you will encounter will be rubbing against the shock or inner fender liner, depending on how much extra room there is to begin with. I believe people encounter rubbing with 225's, and the recommended tire for the wheel is a 275. You will also encounter rubbing with the fender lip itself, as the wheel will definitely not fit under the fender. In addition, although a 275/30R17 would have the exact same diameter as the stock tire, there is no tire made that size. Going up to a 275/35R17 is possible, but you will find only Hoosier drag radials and an all season P Zero made for Porsche in that size. All are priced very high and are also 1.1" taller than the stock tire. There are lots of reasonably priced tires at 275/40R17 but they are 2" taller than the stock tire.

https://www.customwheeloffset.com/o...zbvsUAcqFQOVL1Cq6JzQZrRoPKSpI-b0aAiriEALw_wcB
 


Messages
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127
Location
San Diego
#5
Offset and backspacing refer to the same thing, but measured from a different place. Offset is the distance from the center of the wheel to the plane of the mounting surface, measured in millimeters. If the number is positive, the mounting plane is closer to the outside (pretty side) of the wheel. If the number is negative, it's closer to the backside.

Backspacing is the older way of measuring this and has largely been abandoned. In backspacing, the distance from the inside wheel rim to the mounting surface is measured, usually in inches.

The wheel you are looking at has a 25mm positive offset, which is an inch. The backspacing for that should be 6". The fact that it's 6.48" comes from the fact that they have a little bit of flange thickness to the rim they don't include in the 10" width designation.

In comparison, the stock FiST wheel has a width of 7" and offset of 47.5 mm. 47.5 mm is 1.87". So the backspacing is 3.5" + 1.87" = 5.37", plus a little for the thickness of the rim. So this wheel will go one inch farther towards the shocks at the rim, and three inches farther out. Therefore the tire mounted on it will bulge another half inch or more than that each way. So the issues you will encounter will be rubbing against the shock or inner fender liner, depending on how much extra room there is to begin with. I believe people encounter rubbing with 225's, and the recommended tire for the wheel is a 275. You will also encounter rubbing with the fender lip itself, as the wheel will definitely not fit under the fender. In addition, although a 275/30R17 would have the exact same diameter as the stock tire, there is no tire made that size. Going up to a 275/35R17 is possible, but you will find only Hoosier drag radials and an all season P Zero made for Porsche in that size. All are priced very high and are also 1.1" taller than the stock tire. There are lots of reasonably priced tires at 275/40R17 but they are 2" taller than the stock tire.

https://www.customwheeloffset.com/o...zbvsUAcqFQOVL1Cq6JzQZrRoPKSpI-b0aAiriEALw_wcB
Thank you for the excellent explanation!
 


flbchbm

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#6
Mfgr wheel size info....
Wheel-Size.com :: Reference guide for car wheel and tire dimensions such as size, offset, PCD (wheel-size.com)

Insert your existing wheel and tyre specs, and the desired size, and the outcome is shown on the diagram
Online Wheel and Tyre Fitment Calculator. Offset, Tyre Stretch and Speedo Error | Will They Fit

tire size comparing
Tire Size Calculator

Pay attention to BORE SIZE...too small, will not fit, too large, will need concentric rings, if made to adapt the two sizes.... ours are 63.4mm
 


SteveS

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#7
I just noticed the middle wheel is a 17x8. Its backspacing is similar to the stock wheel. A 245 is the recommended width on that, and a 245/35R17 is available in the Toyo Proxes R1R. Almost stock diameter (about a quarter inch taller). Oddly, if you try going down in section width, to 235 and 225, nothing is really available until you get to 225/40R17, in which case you're an inch and a half taller than stock.
 


M-Sport fan

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#8
You meant 225/45-17 above, correct?
(There are no 225/40-17s save for pure DOT race slicks with 00-40 tread wear ratings.)
 


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Location
Mountains of
#11
One of my mustangs is a foxbody with a somewhat similar set up to what you are asking about... How serious are you on getting them? I don't remember the offset of them but I know they are a lot of weight.

I am switching my winter set up to summer set up tomorrow anyways on my fist.

My fist isn't widebody but let me know... Only reason I am willing to is because not much information exists on the net about what you are asking.

I could weigh them vs stock fist rims with potenzas so you can see... Let me know before 4pm
 


OP
Blanco_ST
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Location
Indio, CA, USA
Thread Starter #14
You should probably explain what "wide body on a budget" means exactly, because 10" wheels are going to take some hacking to fit.
I do want to hack up my fenders and add aftermarket fenders, im just making sure i want have any problems with hit the calipers or any suspension parts.
 


PunkST

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#15
Itll have to be a very aggressive body kit to make these not poke. And theres going to be a huge amount of trimming the arches to keep the wheels from turning the body to bacon. Imo its not really an on the cheap type of job.
 


OP
Blanco_ST
Messages
103
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Location
Indio, CA, USA
Thread Starter #16
Offset and backspacing refer to the same thing, but measured from a different place. Offset is the distance from the center of the wheel to the plane of the mounting surface, measured in millimeters. If the number is positive, the mounting plane is closer to the outside (pretty side) of the wheel. If the number is negative, it's closer to the backside.

Backspacing is the older way of measuring this and has largely been abandoned. In backspacing, the distance from the inside wheel rim to the mounting surface is measured, usually in inches.

The wheel you are looking at has a 25mm positive offset, which is an inch. The backspacing for that should be 6". The fact that it's 6.48" comes from the fact that they have a little bit of flange thickness to the rim they don't include in the 10" width designation.

In comparison, the stock FiST wheel has a width of 7" and offset of 47.5 mm. 47.5 mm is 1.87". So the backspacing is 3.5" + 1.87" = 5.37", plus a little for the thickness of the rim. So this wheel will go one inch farther towards the shocks at the rim, and three inches farther out. Therefore the tire mounted on it will bulge another half inch or more than that each way. So the issues you will encounter will be rubbing against the shock or inner fender liner, depending on how much extra room there is to begin with. I believe people encounter rubbing with 225's, and the recommended tire for the wheel is a 275. You will also encounter rubbing with the fender lip itself, as the wheel will definitely not fit under the fender. In addition, although a 275/30R17 would have the exact same diameter as the stock tire, there is no tire made that size. Going up to a 275/35R17 is possible, but you will find only Hoosier drag radials and an all season P Zero made for Porsche in that size. All are priced very high and are also 1.1" taller than the stock tire. There are lots of reasonably priced tires at 275/40R17 but they are 2" taller than the stock tire.

https://www.customwheeloffset.com/o...zbvsUAcqFQOVL1Cq6JzQZrRoPKSpI-b0aAiriEALw_wcB
Ahh see thats what i was afraid of, the inner rim hitting my shocks. I dont care about height persay because im going to cut the fenders i just need to know how much back spacing i can fit before i rub the shock.
 


OP
Blanco_ST
Messages
103
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Location
Indio, CA, USA
Thread Starter #17
Mfgr wheel size info....
Wheel-Size.com :: Reference guide for car wheel and tire dimensions such as size, offset, PCD (wheel-size.com)

Insert your existing wheel and tyre specs, and the desired size, and the outcome is shown on the diagram
Online Wheel and Tyre Fitment Calculator. Offset, Tyre Stretch and Speedo Error | Will They Fit

tire size comparing
Tire Size Calculator

Pay attention to BORE SIZE...too small, will not fit, too large, will need concentric rings, if made to adapt the two sizes.... ours are 63.4mm
Ill just get hubcentric ring adapters
 


PunkST

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#19
I do want to hack up my fenders and add aftermarket fenders, im just making sure i want have any problems with hit the calipers or any suspension parts.
With the 10" wheel youre biggest battle might be catching the tire on the frame horns when you turn.

The 8" wheel is going to clear suspension. And frame But still need flares.
 


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