355 Speedline Challenge wheels, strange offset?

I've had 295 on my Challenge wheels no problem. I have 285 on them now.

 

I never measured mine I will

 

Those wheels will not work on your car. They are junk. Fortunately for you, I am a scrap metal dealer, so I will take them off your hands for a few bucks.

 

Thanks for pointing that out. Forgot that they were made for both and the offsets would be different.

That explains why Tim and Bob were so much faster than me on the track.

 

Challenge ran 295's on the rear and they fit fine, that's what I currently have on my challenge rims (r6's).

 

I as told stock offset is 68 on the 355 but i have since seen 80 as well. I have nver measured but who knows.

 

Front offset (ET) for the 8J X 18 Challenge wheels is 49 mm and I think the rears are the same as stock F355 wheels, 10J X 18 and 77.9 mm. Anybody who has a similar image for the rear wheels, please post.

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Are you measuring the wheel width all the way to the outer lip which makes a 10 inch rim really 11 inches or inside the flange which is 10 inches? I notice offsets are all over the place so I wonder if people are measuring the rim width in different ways.

 

Thats a great document with all the wheel sizes and offsets. Thanks for sharing!

 

Try this, it will give you a good comparison of stock and challenge!

http://www.willtheyfit.com/index.php?width=265&aspect=40&diameter=18&wheelwidth=10&offset=59&width2=305&aspect2=30&wheel_size=19&wheel_width=11-5&offset2=67

 

Bob- I am not measuring anything. I am reading the ET cast into the wheel by the manufacturer and the ET marked on the box of a new wheel from photos. Measuring will just give you errors. Photos courtesy of Chris at Exoticar. All the offsets in the document I posted are the manufacturer's data.


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I think your offset is correct. I,have challenge wheels also. But some guys with aftermarket 1i inch rears that look good in the wheel well say their.offsets are 60. Some with 10 rear say their offset is 52. How can that be?

 

That makes sense. In the case of the 11 in. wheels, the offset is increased so that they do not protrude too much out.

 

I think on an 11 inch rim, the total width is really 12 inch from outside flange to outside flange. If you measure from inside the flange which is 11 inches, the two different measurements will be off 1/2 inch or about 12mm. I think that is why some of these offsets seem to be so different for the same wheels. Does that make sense?

 

When Ferrari went to wider wheels on later street models, mostly with 114.3 X 5 bolt patterns, the offsets usually were adjusted for the wheel width. Inch wider wheels had the offset adjusted by around 12.7 mm to keep the wheel at a constant distance inside the wheel-well (half the width on each side). An example of this are the similar 10J X 20 wheels on the 612 rear, vs the 11J X 20 on the 599 rear (ET 51.1 vs ET 63.8). Explains why the 599 wheels fit the 612 perfectly, too. On the racing wheels, however, the offsets were sometimes not changed to give a slight increase in track. An example of this are the 360 Challenge (8J X 18 ET 31.5) and Scuderia/16M front wheels (8J X 19 ET 31.5), which have the same offset as the narrower stock wheels (7.5J X 18/19 ET 31.5), resulting in a track increase of 1/4" on each side (1/2" total). Good for cutting down on understeer. Without knowing what the manufacturer was trying to do, and not understanding exactly how the manufacturer measures offset (yes, we all know how offset is calculated), the only way to get good offset information is to get it from the manufacturer.

 

This document list stock 355 OE wheels as 18 x 7.5 + 32mm offset and Challenge wheels as 18 x 8.0+ 49mm offset. This would imply the stock wheels sit roughly 10-11mm out more aggressive than the challenge wheels. I get the feeling the listed offset on the 355 OE wheel is wrong. Can someone confirm?

 

Stock rears are a crazy 79mm. That why a lot of us run spacers so we dont look like a old Winnebago RV
A set of challenge wheels with 59mm offset would be awesome! The would fit perfect with the fenders

 

When you run the slicks they are up against the lips of the fenders. Slicks are big

 

F355 OE wheels are actually 18 x 7.5 +46 (not +32). Which means these are roughly 3mm less aggressive than 355 Challenge Speedline wheels. Someone should edit the doc .


OE and Challenge Speedlines have identical sizes and offsets for the rears. 18x10 +78

 

Like this? That post is several years old.

348


Five Spoke 17” Early, 5 X 108 mm

Front 7.5J X 17 ET 49 mm, Rear 9J X 17 ET 68 mm

Five Spoke 17” Late, 5 X 108 mm

Front 7.5J X 17 ET 49 mm, Rear 9J X 17 ET 43.05 mm



355


Five Spoke 18”, 5 X 108 mm

Front 7.5J X 18 ET 46.15 mm, Rear 10J X 18 ET 77.9 mm


355 Challenge



Five Spoke 18”, 5 X 108 mm

Front 8J X 18 ET 49 mm, Rear 10J X 18 ET 77.9 mm

 

Post might be several years old, but it appears to be the most recent on the subject when I searched. It is good to have the numbers updated for clarification as I was about to order new wheels based off incorrect numbers .