Black Wheels

[merc]

They are 17X8, 5/4.5, but I don't have the offset/backspacing handy. IMHO...I think they look pretty cool, and I considered a set myself at one time, until another idea came through.

Did you say 17x8 ? That my be the front tire size on this picture, but the rears look like ?x9. The Corbra R rim also comes in 18' size, right. :loco:

 

[Donny Carlson]

They are 17X8, 5/4.5, but I don't have the offset/backspacing handy. IMHO...I think they look pretty cool, and I considered a set myself at one time, until another idea came through.

Did you say 17x8 ? That my be the front tire size on this picture, but the rears look like ?x9. The Corbra R rim also comes in 18' size, right. :loco:

The 17's are 9" across, not 8.

The 18" version looks a bit different:

 

[SergntMac]

Did you say 17x8 ? That my be the front tire size on this picture, but the rears look like ?x9. The Corbra R rim also comes in 18' size, right.

Yes, the 2000 Cobra R wheel is 18X9.5, 6.12" backspace. I can't speculate on what's on the rear from this pic.

 

[merc]

I don't know that Donny. Thanks for the quick reply :cool4:

 

[SergntMac]

This wheel is available in a variety of sizes, including 17X8, so, anything is possible.

If this pic is going to be used as a representation of what fits and what does not fit, someone should ask Dennis. If these wheels are same wheels he brought to Ennis last year, I'm pretty sure they are 17x8, because that factored in a number of chats about the affect of 17" wheels on rear end gear ratios.

http://www.fordracingparts.com/parts/part_details.asp?PartKeyField=5089

 

[Donny Carlson]

To clear up some possible confusion

There are more than one versios of the Cobra R Wheel this one:

Which of couse is a 4 bolt pattern, is 8" across

This one:

Is described as a "Chrome SVT Cobra R Wheel," whereas the one I posted earlier is described as a "Chrome Ford Racing Cobra R Wheel" The only difference is specs is that this SVT wheel has a 5.95" backspace compared to the FRP wheel's 5.98". The FRP offset is 37.6 mm, the SVT offset is 36.8 mm

 

[Donny Carlson]

This wheel is available in a variety of sizes, including 17X8, so, anything is possible.

If this pic is going to be used as a representation of what fits and what does not fit, someone should ask Dennis. If these wheels are same wheels he brought to Ennis last year, I'm pretty sure they are 17x8, because that factored in a number of chats about the affect of 17" wheels on rear end gear ratios.

http://www.fordracingparts.com/parts/part_details.asp?PartKeyField=5089

Mac, I realise that its easy to get mixed up when looking at the FRP wheel selection, but your link goes to the 4 lug wheel.

 

[Donny Carlson]

Bleakley Ford has this one on display in their parts department. I think it's a nice looking wheel and comes in two different finishes. This is a 17" x 9"

This has a 6.12" backspacing, making a 41mm offset.

 

[Pantherman]

That's a nice wheel Donny, but interpolating from the conversion chart at http://www.rsracing.com/tech-wheel.html, I think its offset is more like 28 mm. Ford really didn't use 50 mm offset wheels just to frustrate us. It was done to reduce scrub radius to about 10 mm, which helped to give the car very good steering. Scrub radius is defined by drawing a front view line from the upper ball joint down through the lower ball joint to the ground and then measuring out to the centerline of the wheel. When we drop offset from 50mm to 28mm, we roughly triple scrub radius. Steering would not just automatically become awful, but smaller disturbances in the road would disturb tracking. Otherwise acceptable tire imbalance or out of round would suddenly be noticeable. As they say in the car business, your mileage may vary. One last downside before I stop playing Jeremiah is that with zero scrub radius, the front tires pivot around their contact patch centers. As scrub radius increases, the tires start to swing in an arc fore and aft. This eats up clearance ahead of and behind the tires.

 

[SergntMac]

Mac, I realise that its easy to get mixed up when looking at the FRP wheel selection, but your link goes to the 4 lug wheel.

My point exactly, Donny...Makes as much sense as looking at pic of a particular car without knowing more about what wheels size is in place, wouldn't you agree?

 

[Donny Carlson]

My point exactly, Donny...Makes as much sense as looking at pic of a particular car without knowing more about what wheels size is in place, wouldn't you agree?

True. Wheel stuff is tricky.

 

[Mike Poore]

See http://www.rsracing.com/tech-wheel.html for a good description of offset/backspacing. All things are relative, but once you get past the physical clearance issues, decreasing offset increases bearing, ball joint, and steering gear loads and makes the car more likely to wander at high speeds. A little change would be insignificant, but one inch is quite a bit.

No, no it's TWO inches, one on each side, remember, we're not talking about half a car. Here's more old guy stuff. We used to think it was cool to reverse our rims, by drilling the rivets, and turning the hubs inside out. Of course, wheels weren't as wide in those days, but it was enough to tear the crap out of the steering gear, tie rods, king pins and bushings, not to mention handling issues. But chrome 'em, & add Moon caps, and they looked oh, so cool, cruising Richardson’s. Remember American Graffiti? That was us, only at Hagerstown, MD.

 

[Donny Carlson]

That's a nice wheel Donny, but interpolating from the conversion chart at http://www.rsracing.com/tech-wheel.html, I think its offset is more like 28 mm

Thank you for posting the link, and the information. There is one thing I want to point out with the conversion chart, though. It does not show a 6.5" backspace wheel (I verfied this measurement on my spare this afternoon) for an 8" wheel, but it does show for a 6, 5.5, 5, 4.5, etc, which is enough to extrapolate what the chart would show for 6.5".

4.5 = 0
5 = 12 (difference of 12 mm)
5.5 = 25 (difference of 13 mm)
6 = 38 (difference of 13 mm)

Which makes sense, because 1/2 inch is 12.7 mm

So, if we extrapolate to 6.5 inches, 38 + 12 = 50 (or just slightly more) mm

which matches what we know for the Marauder wheel.

The FRP 9" wheel,according to the chart, would have a 25.4 mm offset.
Safe to say the offset is an inch more

Okay, I understand it now.

The centerline on the the Marauder wheel is 4.5 inches from the inboard flange, with a positive offset of about 2 inches, the distance from the landing pad to the inboard flange is 6.5 inches, to the outboard flange is 2.5 inches. (the wheel is 9" from inboard to outboad flange, 8" rim width)

The centerline on the FR500 wheel is 5 inches from the inboard flange, with a positive offset of about 1 inch. The distance from the landing pad to the inboard flange is 6 inches, to the outboard flange is 4 inches. (The wheel is 10" from inboard to outboard flange, 9" rim width).

So, that means the FR500 wheel will actually extend 1.5 inches further out than the Marauder wheel, though it will not extend as far in as the Marauder wheel by 1/2 inch. You have a wider wheel sitting further outboard of the car.

Ford really didn't use 50 mm offset wheels just to frustrate us. It was done to reduce scrub radius to about 10 mm, which helped to give the car very good steering. Scrub radius is defined by drawing a front view line from the upper ball joint down through the lower ball joint to the ground and then measuring out to the centerline of the wheel. When we drop offset from 50mm to 28mm, we roughly triple scrub radius. Steering would not just automatically become awful, but smaller disturbances in the road would disturb tracking. Otherwise acceptable tire imbalance or out of round would suddenly be noticeable. As they say in the car business, your mileage may vary. One last downside before I stop playing Jeremiah is that with zero scrub radius, the front tires pivot around their contact patch centers. As scrub radius increases, the tires start to swing in an arc fore and aft. This eats up clearance ahead of and behind the tires.

Okay, get this too. The closer to zero scrub radius, the better the car will steer, and presumable tire wear will be better. By pushing the scrub radius out more positive will reduce handling.

Technically speaking, to prevent degradation in handling, you should stick to a wheel with an offset that does not change OEM scrub radius. The question becomes whether the increase in scrub radius by 25 mm -- an inch -- will produce unacceptable handling. It may very well be that the additional scrub radius is insignificant to some, and it may be that other owners would hate it. As you said, YMMV.

I still think the FR500 wheels would fit, but whether you'd be happy with them is sorta a matter of preference, sorta like the choice between lowering your car or leaving it stock. Again, I say I'd love to try this out, but there is better things to gamble $1000 on than replacement wheels when our stock wheels are so nice.