I have been driving the fit around with a set of my race wheels and tires up front with base stocker 14" on the back. I don't know if its the lighter rims or the lack of bite in the tires on the back but the car seems a lot more nimble and quick in the turns with this setup.

I am going to an SCCA event tomorrow and Im tempted to run this setup. Has anyone else tried this with good results or might see some drawback in racing that might not favor good lap times? I'm thinking it might carry the back around rwd like in the tight turns.

I'm just trying to make up excuses to go racing tomorrow since I have to wait for my real set of race tires to come next week.

 

You are not able to run in a stock class at autocross because if you have a base Fit you'll need four 14" stock rims.

Using any other sized rims will put you into STS class if you have street tires and FSP if you use R compounds on the fronts.

What tires and rims do you have for the fronts?

Any other mods installed besides the front tires?

Any upgrade to air intake puts you out of stock class.

You cannot adequately test a car on the street safely so it's hard to say what will happen for you at autocross.

Give it a try and see how you do.

Stock tires have very poor grip and handling for autocross. I've used the stock 15" wheels and tires and they didn't work very well at all. They also wore down very fast.

 

I should have clarified but I am in STS. I have a progress rear sway bar, fender braces, tanabe springs, j's roll center adjusters, front and back tower bars, I/H/E, and 15" kosei wheels. The tires I have on the front are some hannook, but they are just loaners for the front till I got my real set of tires this week. I didn't plan on racing today and I am glad I didn't because I don't think the tires would have worked like I thought(they are bald) but the idea still seems like it would work.

If you had sticky 15x7s in the front for grip and handling and trailed in the rear with some 14x5.5s or similar, you have a lot less rotational mass and unsprung weight with narrow tires in back, and being its fwd I would think that as long as the tread was sticky in back that the tires would just trail quick in the turns without effecting grip or handling. The main benefit would be the weight loss, but I think the idea could work, mainly for autocross.

 

It might work. You'd have to get used to it and make adjustments in whatever suspension and tire pressures you have. Chalk the tires to check rollover and check tire temperatures to see how well you are using the tires.

In another car I am currently running in autocross with-

Front 225/50-15 on 15x8 rims
Rear 205/50-15 on 15x8 rims

No real big difference on handling than with all 205/50-15 but 225/50-15 is a taller tire and effectively raises gearing compared to using 205/50-15.
I have tall gears so smaller tire offers more advantage.

225/50-15 is a better fit and width for 15x8 rims but weighs about 3 lbs more per tire.

So far the trade off has not yield any positive results, in fact I'm slower with the change right now, and need to make more adjustments to my driving (will be doing downshifting in tight corners).

 

There are a few reasons I'm sure, but the fastest time attack and road racing front wheel drive cars out of japan run wider in the front. Like the top RSX's, they run 245/40/17 in front, 215/45/17 in the rear.
My guess is it would aid in tossability, in turn in. In theory, it seems that having less traction in the rear is better for reducing understeer. If you had more traction than less out back, it seems it would make you understeer more.

 

Your car is more nimble with the tire variation. Its just like disconnecting the front antisway bar to reduce the immense understeer of the stock Fit.
Yes, this tire setup has been proven decades ago to be an excellent solution for vehicles with severe understeer otherwise. Anything you do to reduce understeer or increase oversteer improves handling a bunch. We ran CRX's, Eclipses, and Swifts with comp tires (BFG's in those days) up front and stock tires in back to generate rotation of the vehicle in tight turns to aim the car out of the turn in as close to a straight line as possible (vehicles accelerate faster in a straight line than in a curve) to maximize corner exit speed. You may want to practice initiating & controlling the rotation in a vacant parking lot under various tire pressures to acquire the skills to do it well but your times will improve greatly.
Also, so rules don't allow different tires front to rear so you might inquire early. good luck.

 

I would have to say lack of bite with the 14"s I know the stealies are a lot heavier than the wheels I got from you.

 

Any time you improve grip at the front and don't in the rear the Fit will really be more nimble because you decreased the heavy understeer. And it turns better.
Assuming the diameters of your race tires and rear tires on the rear are pretty close to the same (with the fronts a tad under, say 1/8 to 1/4"), the Fit balance and nimbleness indeed improve because the Fit becomes more rotatable. More rotation means the rear will swing around behind the fronts and line-up better with the exit path so your exit speed improves dramatically. In any kind of racing including autocross the exit speed is the critical attribute. Practicing rotation will improve your times.
In your case putting comp tires on the front probably means you need the front antisway bar. If your organization won't let you have unmatched tires, and some don't, disengage the front antisway bar on the driver's side by removing the shock to bar link. That will amount to much the same thing as comp tires front and squegies rear.
good luck.
PS all these 'tricks' with mismatched tires, antisway bar changes, and tire pressure mods were tried (with success) in autocrossing as far back as the 60's and probably before but I wasn't there then. We ran an Eclipse in IMSA Firehawk with better front tires than rears like most everyone else in the 90's. Proven the fast way for front-engined front drive understeering cars.