Wheel track options?

[Made_In_America]

I'm toying with the idea of buying a coupe but I'm working out the details of what I would want to do. If I build the coupe I want to flare the fenders a bit. I see people running 10.5" wheels with 315 tires that work well with the Coupe as is. Question is with the flares, how can I extend the wheel track without going with a ridiculous rear wheel size like 18x12/13? I know about wheel spacers but I seem to remember there being a negative to going that route? Any insight or suggestions would be welcome, thanks.


This is always asked so to clarify, the car is to be a race car first and foremost that can be driven on the street on occasions. I plan on road racing the car often.

[riptide motorsport]

the newer mustang rear ends ( sn 95 and newer) are about an inch wider. Nothing other than that , that I know of. Wheel spacers should perform safely and adequatly for your needs though.

[Made_In_America]

Thanks, I am only looking to flare it about 2" but I want to make sure the wheels fit right in the well. I have read a lot about spacers but it it's 50/50 good or bad. Just trying to educate myself on the subject, thanks again.

[tirod]

I find spacers to be a value engineered way to use the wrong wheels. If it really is a full on race car, specifying the correct backset to center the tire in the wheel well is basic. That way, the studs aren't cantilevered with excessive stress, and the hubs live with the bearing loads.

Whether the wells need flaring, what the optimum tire size is, and how it performs on the track after extensively comparing different compounds and tire sizes is going to be more important than what it looks like sitting parked in the pit. Big tires are only better if they are proven to offer more of a specific quality the driver and car can actually use - and by most accounts, having consistently reliable handling is much more a function of optimizing the chassis rather than finessing the looks of a fender well.

It's likely money better spent on a data acquisition system to show where the driver can get closer to ten/tenths of the traction circle in various corners - a .5 second improvement there can add up to 5-6 seconds on the lap. It's just an assumption that larger tires and flared fenders would do anything at all. A data acquisition system will, it's proven race tech.

[Made_In_America]

There are "full on race cars" that use spacers and lower wider cars are proven to have a higher skid pad when all other things are equal. To be honest the flares are a little more for the look but by extending the wheel track by 4" in the will yield better performance. Its not about bigger looking tires. I just want to make sure I do it right is all.

[tirod]

Increasing the track 4" doesn't necessarily guarantee improved cornering. There is a lot more involved - the suspension is designed to keep tires as flat and level as it can with specific sized tires in mind. Pushing them out further from the centerline of rotation will simply put more stress on the hub bearings, and the camber curves with resulting actual tread contact patches may not be correct.

If the track needs to be wider, the suspension arms themselves need to be lengthened, which does offer some advantages. This and a whole lot more is thoroughly explained in Carroll Smith's book, Tune to Win. He explains how 4 out of 5 of the ideas chassis tuners go thru are proven ineffective. They have to work thru dozens of combinations to get the correct assortment of "ideas" selected that work together to make an improvement.

Those lower wider cars don't always turn out better, too much frontal area doesn't help, and high steady state skid pad performance is emphatically not what ever happens on a race track. It would be easy if it was. What does happen is the most consistent handling car will go faster because it's less "brittle" and doesn't fall off the grip curve radically. Who says? Carroll Smith. Carroll Smith had an extensive career in real race car development, worked with Carroll Shelby on the GT40's, helped bring home the wins at LeMans and elsewhere from 1966 to 1969, and worked with Ferrari Formula One.

Don't take my word for it, read his books, and you'll wind up using insight from a successful professional who didn't need to hide his secrets or protect a market position.

[Timb]

the newer mustang rear ends ( sn 95 and newer) are about an inch wider. Nothing other than that , that I know of. Wheel spacers should perform safely and adequatly for your needs though.

Just for a visual this is an SN95 rear with the stock GT 17 inch rims and tires
http://1.bp.blogspot.com/-ckj1rrnVu9M/T-ONxRXDQ1I/AAAAAAAAAMo/QUOK3zsN1Zw/s1600/IMG_6278.JPG

[STLMARSHALL]

Another thought is that a wider car makes you drive a wider line. On tighter tracks a wider line is usually not as fast.

There is a trend in SOLO racing to build the smallest car possible. Many of the wider cars have trouble navigating some of the tighter elements cleanly. I am thinking about pulling my 1.25" spacers off to narrow my rear end. About 80% of the cones I hit are with the rear tires...after I drove a perfect line that cleared them with the front tires. I will still run the spacers on the street as the Daytona looks strange with the tires tucked way back in the huge wheel wells.

Here is an example of the front clearing something the back won't: http://i464.photobucket.com/albums/rr2/mmarshall01/DSC_0447.jpg

[Made_In_America]

Thats funny, I just ordered that book about 3 days ago. I plan on grabbing his other books as well. Anyway, I am all ears. I have tracked my mustangs at my local track and modified them but I am by no means any expert. With this car I am planning to actually race though. Somewhere down the road I want to take on the Silver State Classic.

[Made_In_America]

I dont plan on doing any auto x so the really tight turns and cones aren't as big of a concern. I plan on doing the majority of my laps here:

[tirod]

You're in for a good read. More to this discussion, there's a section on why a wider front track than rear can help cornering. And some interesting insights into how much or little Ackerman could affect things. That means having the ability to change the steering arms, which donor spindles don't often do.

Having run chrome reverse rims on a '66 Mustang in the day, having the tread shoved out further did accomplish the aesthetic affect. It also wore out the hub bearings and added a significant amount of scrub since the center of the tire was offset from the SAI. Tire contact patches can be maximized, but the correct centering is still important.

With that in mind, longer front control arms, a stock slightly narrower width rear, optimized steering with maybe even some selective bump steer (it's actually not all bad,) and getting the camber controlled to keep the outside front tire in it's best place are all things that have been used.

Carroll wrote about it in 1978, right after his Ferrari Formula One experience. Things change, but they still stay the same.

[Made_In_America]

This is what I am going for with a little less flare. Looks killer but I will read up on the proper suspension geometry and make sure it is a functional setup. I wont do it if it wont yield a good result.

[type 65 coupe]

Does anyone have a pic of a coupe w/ 295 front and 335 rear tires