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post #1 of 6 (permalink) Old 12-26-2010, 06:29 PM Thread Starter
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Q: Stock Suspension Travel & Smaller diameter tires (for track use)

Hi:
I'm building a 95 Thunderbird LX into my car for the 24 Hours of Lemons. One of the things I need to tackle is the tire choice.

As most of you folks know, sticky tires in the stock wheel diameter are just NOT available.

I KNOW that adjusting the overall tire diameter is NOT recommended because it wrecks hell with your speedomoter. Since this car will be tracked, I could care less how fast the speedometer says I'm going.
If you aren't familiar with the rules of LeMons, upgrading the suspension is OUT of our budget.
Tires on the other hand do NOT count but they need to be DOT certified and have a minimum treadwear rating of 190.

Anyway, based on feedback, I've narrowed my choices down to the following tires & sizes. I haven't decided on size but I've listed them in my order of tire preference.

Stock Overall Wheel+Tire Diameter = 26.85" (for reference)
Dunlop Direzza Sport Z1 Star Spec (205/50-R15) = 23.07" diameter = 14.08% difference = 1.89" ride height drop
Dunlop Direzza Sport Z1 Star Spec (195/55-R15) = 23.44" diameter = 12.07% difference = 1.705" ride height drop
Toyo PX4 (205/55R15) = 23.88" dia = 11.0% difference = 1.485" ride height drop
Toyo PX4 or Falken ZE 912(225/50R15) = 23.86" dia = 11.14% difference = 1.495" ride height drop
Falken ZE 912 (225/60R15) = 25.63" dia = 4.54% difference = 0.61" ride height drop

Q: What is the maximum suspension travel on the stock Thunderbird suspension? I.e. how low can I drop this car without bottoming out the car?

Will the suspension travel prevent me from using ANY of these tires?
Also, based on my requirements here, please let me know if you have any particular suggestions on tires.

Thanks in advance for your replies.
Regards,
-g


PS. I've taken out about 200LBs out of the car. It should be about 3300Lbs before gas+driver.
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post #2 of 6 (permalink) Old 12-26-2010, 07:48 PM
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You won't have any problems running any of those tire sizes, there is plenty of suspension travel. Also, by the time you take all the weight out of the car, you will probably want to cut the springs to bring the ride height back down a bit. With all that said, I would reccomend finding some 16" wheels, and running the stickiest and widest tires you can find/afford. Last year we had one set of toyo proxes245/50/16s and one set of falken ziex 225/60/16s. I also cut 1.5 coils off all 4 springs to drop the ride height and stiffen up the suspension. Also, if you can get some SC/sport springs and sway bars, they will drastically improve your handling (especially after cutting the springs) and it will still be stock parts so they won't kill you on the BS inspection.

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post #3 of 6 (permalink) Old 12-26-2010, 08:25 PM Thread Starter
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Quote:
Originally Posted by MadMikeyL View Post
You won't have any problems running any of those tire sizes, there is plenty of suspension travel. Also, by the time you take all the weight out of the car, you will probably want to cut the springs to bring the ride height back down a bit. With all that said, I would reccomend finding some 16" wheels, and running the stickiest and widest tires you can find/afford. Last year we had one set of toyo proxes245/50/16s and one set of falken ziex 225/60/16s. I also cut 1.5 coils off all 4 springs to drop the ride height and stiffen up the suspension. Also, if you can get some SC/sport springs and sway bars, they will drastically improve your handling (especially after cutting the springs) and it will still be stock parts so they won't kill you on the BS inspection.
Thanks for your lemons specific feedback.
We are pretty committed to stock rims & suspension.. for now.
This is our first race (without a firm commitment from everyone else that we will go back for a 2nd go-around) so our #1 goal is not to win but to see it through until the checkered flag.

Q: Isn't the concern having too much suspension vs. too little?
I'm worried that at the bottom of a hill, for example, the weight of the car and transmission will cause the bottom bits to scrape because the ride height has been lowered due to the smaller diameter tires.

If you say that this won't be a problem (esp with stock ride height), then we'll be OK with the "max max" looking jack-ed up suspension.
-g
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post #4 of 6 (permalink) Old 12-26-2010, 08:55 PM
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Well our car is pretty low, and we didn't have any problems. The only thing was going into one banked turn, the front chin spoiler would scrape, but who cares? I really wouldn't be too worried about being too low, but if it concerns you, maybe go check out the track that you are going to be running on?

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post #5 of 6 (permalink) Old 12-26-2010, 09:33 PM
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BF goodrich geforce sport tires are pretty sticky...

http://www.tirerack.com/tires/tires....SPV2&tab=Specs

I've ran these before; I'm running them in 16s now.

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post #6 of 6 (permalink) Old 12-26-2010, 09:51 PM Thread Starter
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Thanks for the recommendations, folks. I could care less about the chin spoiler so I believe we are good to go. I need to confer with the team with the tire cost/performance trade-offs now that we know all of them are good to go.

-g
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