In the world of exotics, it seems that a mid engined car with 50/50 (or 25/25/25/25) weight distribution is pinnacle. maybe that applies to RWD or AWD. in your opinion, if you could hypothetically have up to 100% of the vehicles weight on or beyond the front wheels of our cars, what do you think would be near an optimal and safe weight distribution for a road course driven festiva?
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Originally posted by F3BZ View PostIn the world of exotics, it seems that a mid engined car with 50/50 (or 25/25/25/25) weight distribution is pinnacle. maybe that applies to RWD or AWD. in your opinion, if you could hypothetically have up to 100% of the vehicles weight on or beyond the front wheels of our cars, what do you think would be near an optimal and safe weight distribution for a road course driven festiva?
The rear wheels do very little on a FWD vehicle and weight over them actually acts to spin the car in circles under hard cornering. Weight forward of the front axle stabilizes the chassis and helps with driving and cornering grip ( but ultimately, any weight is counter productive, so try to keep things light).
RWD platforms do work better with weight on the rear wheels, but any more than 50% will make the car hard to drive at 10/10 of the limit. Ask any Porsche race driver.
AWD cars also benefit from weight forward designs. Both Subaru and Audi have had great success with front weight biased AWD cars.
After a few years of testing, and playing around with these light FWD cars, I'm convinced that the old 50/50 mid rear platform is inferior in many ways to a lightweight fwd car. In street trim, my B6t Festiva would out corner even the mighty Lotus Exige with it's ideal chassis configuration. I watched one slide off the track in my rear view mirror as the driver attempted to follow me into the carousel at firebird Main coarse. Apparently the Festiva can carry more speed into corners than the Lotus, even with less tire under the car. The two cars were nearly identical weight and HP, but the Lotus was no match for the Festiva.Last edited by Advancedynamix; 07-02-2015, 06:37 PM.Driving for me is neither a right nor a privilege. Driving is my passion, as it was for the people who invented the automobile, the people who paved the first roads and the people who continue to improve the automobile. Please respect this passion.
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Festiva Chassis Dynamics
interesting. thanks for your input. the 100% was a "hypothetical" limit but mathematically impossible. just wondered how close to that would be ideal. my build goal will require the engine be moved forward as much as practical and my old school magazine thinking was that it would hurt handling so this is good news. now it brings up other questions. i wonder how much this affects the contribution of the rear brakes if the rear of the car is unloaded by the fulcrum?, effect of a heavy front end. do you use an adjustable proportioning valve? or as silly as it seems, if they don't contribute much, could the rear brakes and their unsprung weight be removed? not on a street legal car of course.
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Originally posted by F3BZ View Postinteresting. thanks for your input. the 100% was a "hypothetical" limit but mathematically impossible. just wondered how close to that would be ideal. my build goal will require the engine be moved forward as much as practical and my old school magazine thinking was that it would hurt handling so this is good news. now it brings up other questions. i wonder how much this affects the contribution of the rear brakes if the rear of the car is unloaded by the fulcrum?, effect of a heavy front end. do you use an adjustable proportioning valve? or as silly as it seems, if they don't contribute much, could the rear brakes and their unsprung weight be removed? not on a street legal car of course.No car too fast !
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So far, the stock rear brakes and brake bias seem to work well. The biggest problem that we've seen is the rear ends tendency to hydroplane in wet conditions. This is why I suggest narrow, deeply treaded tires on the rear of a lightened and engine swapped Festiva when driven in the rain. This seems to solve the problem.Driving for me is neither a right nor a privilege. Driving is my passion, as it was for the people who invented the automobile, the people who paved the first roads and the people who continue to improve the automobile. Please respect this passion.
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Originally posted by Advancedynamix View PostSo far, the stock rear brakes and brake bias seem to work well. The biggest problem that we've seen is the rear ends tendency to hydroplane in wet conditions. This is why I suggest narrow, deeply treaded tires on the rear of a lightened and engine swapped Festiva when driven in the rain. This seems to solve the problem.Last edited by TominMO; 07-02-2015, 08:14 PM.90 Festy (Larry)--B6M (Matt D. modified B6 head), header, 5-speed, Capri XR2 front brakes, many other little mods
09 Kia Rondo--a Festy on steroids!
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Originally posted by TominMO View PostWould this apply well in both wet and dry conditions on the street? I.E., if I'm running my 165/55-14s on front, would the car corner better in wet conditions with skinnier 155/80-13s that had a deep tread? Especially given that they would be S or T-rated. I'm thinking the same tires as on the front would still be better for dry.
In wet or snowy conditions your 155/80-13 tires will work better on the rear. The front of the car may be a different story. You'll have to test it to see.Last edited by Advancedynamix; 07-02-2015, 08:24 PM.Driving for me is neither a right nor a privilege. Driving is my passion, as it was for the people who invented the automobile, the people who paved the first roads and the people who continue to improve the automobile. Please respect this passion.
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Originally posted by Advancedynamix View PostThis does apply to the street as well. I usually run no wider than a 165mm tire on the street on all 4 corners because the Festiva doesn't have enough weight to effectively utilize a wider treat on typical roads.
In wet or snowy conditions your 155/80-13 tires will work better on the rear. The front of the car may be a different story. You'll have to test it to see.90 Festy (Larry)--B6M (Matt D. modified B6 head), header, 5-speed, Capri XR2 front brakes, many other little mods
09 Kia Rondo--a Festy on steroids!
You can avoid reality, but you can't avoid the consequences of avoiding reality--Ayn Rand
Disaster preparedness
Tragedy and Hope.....Infowars.com.....The Drudge Report.....Founding Fathers.info
Think for yourself.....question all authority.....re-evaluate everything you think you know. Red-pill yourself!
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I run 155/80-13s on all four corners in the winter. I've had no problems with getting stuck (unless I'm doing something stupid) and can make it where a lot of all/four wheel drive vehicles seem to be traction challenged.
I've been running 185-60's in the summer but my current set will be ready for replacement soon. I make go to something a little narrower based on Charlie's suggestion above. Will be keeping the 13"x5" wheels though.Ian
Calgary AB, Canada
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Originally posted by TominMO View PostNot planning on the Festy ever seeing snow again, especially with salt or brine on the road. So probably I'll just go slower in the rain on the tires I have on there now. The Aspire is my four-season car; I have brand new snows (155/80-13 Bridgestone Blizzaks) mounted on Aspire steelies for it, should we get some heavy snow here. In the garage, swap 'em all in ~10 minutes.
The most noticeable hydroplaning situation I've personally seen and felt was on a BP swapped Festiva with a frontward mounted engine, no interior, no rear hatch and 195/60-14" Falken Azenis 615K tires. This was at MSR in Houston under moderate rain. The rear of the car would drift on every corner at speed, and I almost spun several times. It was a fun challenge, but made me very aware of something I hadn't considered. The light rear end will hydroplane easier.
With More negative camber and narrower tires in the rear, the car would have been much more stable. The test car had stock camber settings in the rear.Last edited by Advancedynamix; 07-03-2015, 08:51 AM.Driving for me is neither a right nor a privilege. Driving is my passion, as it was for the people who invented the automobile, the people who paved the first roads and the people who continue to improve the automobile. Please respect this passion.
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Originally posted by bhearts View PostHow do the front wheels compare in weight on Pedro?
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Pedro feels wonderfully balanced at the limit on street tires however, where Tweak would really overwork street tires and had more of a tendency to want to spin around in circles after the tires got hot. Pedro is much easier to drive at 10/10.Driving for me is neither a right nor a privilege. Driving is my passion, as it was for the people who invented the automobile, the people who paved the first roads and the people who continue to improve the automobile. Please respect this passion.
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That's neat! Thanks. Good resource to have.Driving for me is neither a right nor a privilege. Driving is my passion, as it was for the people who invented the automobile, the people who paved the first roads and the people who continue to improve the automobile. Please respect this passion.
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