Anyone tracking ForgeStar rims?
07-06-2011, 04:28 PM
#3
Melting Slicks
No issues besides lead time on getting 18x11's +55 for rear. 18x10s can be had for the front at a +48 offset (for a C5)
I was using F14's. Cheap, strong, and light
I was using F14's. Cheap, strong, and light
07-06-2011, 06:45 PM
#5
Melting Slicks
No I don't, but you can run 295/335 on a 10" and 11" from most manufacturers iirc. The other down side to them is they are limited in offsets and sizes per application. The wheels aren't custom made like many other companies have, so I don't even know if they have an option for C5s for an 11" and 12" width...
07-06-2011, 07:19 PM
#6
Race Director
Thread Starter
My stock Speedline offsets (c5z) are
17x9.5x54
18x10.5x58
So when you go with wider rims it means you need to go to a LOWER number for the offset, which moves the whole rim width out to clear the tub, is that right?
10's and 11's just don't seem like it's worth bothering as the stock size is 9.5 and 10.5
17x9.5x54
18x10.5x58
So when you go with wider rims it means you need to go to a LOWER number for the offset, which moves the whole rim width out to clear the tub, is that right?
10's and 11's just don't seem like it's worth bothering as the stock size is 9.5 and 10.5
07-06-2011, 07:29 PM
#7
Drifting
Member Since: Dec 2005
Location: Dayton, OH
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An 18 x 10.5 with a 63mm offset is about as far out as you can go. So you could run a 18 x 12 that came with a 54mm offset and then add a 10mm spacer. You may hit the upper control arm at full droop but if you are running coilovers they will hit the control arm before the wheel will.
07-06-2011, 08:42 PM
#8
Race Director
Thread Starter
You need to figure the offset out based on the tire. A 63mm offset on a 12 wheel will clear the tub and fender but it depends on the section width of the tire. You can only add so much towards the inside and if you go too far towards the outside you will rub the fender lip depending on how much camber you run in the rear. If you can't get the correct offset in the width you want you can add a space to get the same result.
An 18 x 10.5 with a 63mm offset is about as far out as you can go. So you could run a 18 x 12 that came with a 54mm offset and then add a 10mm spacer. You may hit the upper control arm at full droop but if you are running coilovers they will hit the control arm before the wheel will.
An 18 x 10.5 with a 63mm offset is about as far out as you can go. So you could run a 18 x 12 that came with a 54mm offset and then add a 10mm spacer. You may hit the upper control arm at full droop but if you are running coilovers they will hit the control arm before the wheel will.
285/30/18 a6 is 11.5 section width
295/30/18 a6 is 11.6 section width
335/30/18 a6 is 13.5 section width
The rims I like will work with those tires, & I don't mind some spacer (10mm is a lot for me) but how do you do the calculation.
These tires all fit my car at my setup with no rub (1/4 inch spacer for rear)
What offsets should I look for in the Forgestar rims?
07-07-2011, 02:52 PM
#9
Drifting
Member Since: Dec 2005
Location: Dayton, OH
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Instead of trying to explain it, how about an online calculator that does it for you 
This is a pretty good one. It lets you compare a wheel to your current wheel and also gives how much further in it will be as well as how much further out it will extend.
If you want to use this to figure out if the tire will fit then you still use the same offset but use the section width of the tire to find clearances. Remember that the section width varies a little bit depending on the wheel width. Most manufactures of race tires will give you the section width based on a measured rim width. If you use a narrower rim to a point the section width will be wider and if you use a wider rim the section width will be narrower than the rim. For instance, if you put the 285 above on a 12" wheel the rim would be wider than the section width of the tire so you would use the wheel to calculate clearance not the tire.
http://www.1010tires.com/WheelOffsetCalculator.asp
This is a pretty good one. It lets you compare a wheel to your current wheel and also gives how much further in it will be as well as how much further out it will extend.
If you want to use this to figure out if the tire will fit then you still use the same offset but use the section width of the tire to find clearances. Remember that the section width varies a little bit depending on the wheel width. Most manufactures of race tires will give you the section width based on a measured rim width. If you use a narrower rim to a point the section width will be wider and if you use a wider rim the section width will be narrower than the rim. For instance, if you put the 285 above on a 12" wheel the rim would be wider than the section width of the tire so you would use the wheel to calculate clearance not the tire.
http://www.1010tires.com/WheelOffsetCalculator.asp
Last edited by geerookie; 07-07-2011 at 02:58 PM.
07-07-2011, 03:42 PM
#10
Race Director
Thread Starter
Instead of trying to explain it, how about an online calculator that does it for you
This is a pretty good one. It lets you compare a wheel to your current wheel and also gives how much further in it will be as well as how much further out it will extend.
If you want to use this to figure out if the tire will fit then you still use the same offset but use the section width of the tire to find clearances. Remember that the section width varies a little bit depending on the wheel width. Most manufactures of race tires will give you the section width based on a measured rim width. If you use a narrower rim to a point the section width will be wider and if you use a wider rim the section width will be narrower than the rim. For instance, if you put the 285 above on a 12" wheel the rim would be wider than the section width of the tire so you would use the wheel to calculate clearance not the tire.
http://www.1010tires.com/WheelOffsetCalculator.asp
This is a pretty good one. It lets you compare a wheel to your current wheel and also gives how much further in it will be as well as how much further out it will extend.
If you want to use this to figure out if the tire will fit then you still use the same offset but use the section width of the tire to find clearances. Remember that the section width varies a little bit depending on the wheel width. Most manufactures of race tires will give you the section width based on a measured rim width. If you use a narrower rim to a point the section width will be wider and if you use a wider rim the section width will be narrower than the rim. For instance, if you put the 285 above on a 12" wheel the rim would be wider than the section width of the tire so you would use the wheel to calculate clearance not the tire.
http://www.1010tires.com/WheelOffsetCalculator.asp
I tried 10.5x58
vs
12x58
The calculator adds 19mm to inside (less clearance) and 19 to outside (sticks out)
That makes sense.
Then I tried 10.5x58
vs
12x68 (INCREASE OFFSET)
The calculator adds 29mm to inside (less clearance) and 9 mm to outside (sticks out)
Herein lies confusion.
I look at the picture and to me an INCREASE in OFFSET moves all the wheel to right/outside.
So an INCREASE in OFFSET should result in MORE clearance on the inside compared to using the same offset on a wider wheel.
At least according to that diagram & calculator.
What am I not getting?
Last edited by froggy47; 07-07-2011 at 03:44 PM.
07-07-2011, 04:20 PM
#11
Drifting
I tried 10.5x58
vs
12x58
The calculator adds 19mm to inside (less clearance) and 19 to outside (sticks out)
That makes sense.
Then I tried 10.5x58
vs
12x68 (INCREASE OFFSET)
The calculator adds 29mm to inside (less clearance) and 9 mm to outside (sticks out)
Herein lies confusion.
I look at the picture and to me an INCREASE in OFFSET moves all the wheel to right/outside.
So an INCREASE in OFFSET should result in MORE clearance on the inside compared to using the same offset on a wider wheel.
At least according to that diagram & calculator.
What am I not getting?
vs
12x58
The calculator adds 19mm to inside (less clearance) and 19 to outside (sticks out)
That makes sense.
Then I tried 10.5x58
vs
12x68 (INCREASE OFFSET)
The calculator adds 29mm to inside (less clearance) and 9 mm to outside (sticks out)
Herein lies confusion.
I look at the picture and to me an INCREASE in OFFSET moves all the wheel to right/outside.
So an INCREASE in OFFSET should result in MORE clearance on the inside compared to using the same offset on a wider wheel.
At least according to that diagram & calculator.
What am I not getting?
In your example, the 12" wheel is 38mm wider than the 10.5". Center gives 19mm more width to each side. When you increase the offset 10 mm that adds 10+19 for 29mm to the inside and 19-10 for an extra 9mm to the outside. Hope that helps.
07-07-2011, 05:25 PM
#12
Race Director
Thread Starter
Offset is the location of the center of the wheel relative to the mounting surface. Adding offset moves the wheel to the inside. Take a 12" wheel (size doesn't matter) and use a current offset of 0mm and a new offset of 50mm, say. You'll have less inner clearance (by 50mm) and retract the outer edge (by the same 50mm.)
In your example, the 12" wheel is 38mm wider than the 10.5". Center gives 19mm more width to each side. When you increase the offset 10 mm that adds 10+19 for 29mm to the inside and 19-10 for an extra 9mm to the outside. Hope that helps.
In your example, the 12" wheel is 38mm wider than the 10.5". Center gives 19mm more width to each side. When you increase the offset 10 mm that adds 10+19 for 29mm to the inside and 19-10 for an extra 9mm to the outside. Hope that helps.
