Okay now I have a serious chassis and tire Question.

[syborg tt]

Okay now I have a serious chassis and tire Question.

If you look at all the new late model super cars they have much smaller wheel & tire combo then the older muscle cars that are being built on this
site and other site. I know the philosphy that bigger is better but at what point is it overkill. If you have that much unsprung weight on a car you have
to increase the power of the engine and increase the brake size to over come said weight. I am just trying to figure out when a 12" Tire became small.

BTW I am not a suspension guy so I really looking for wisdon on this.

Here is the only example I can give you.

Joe has a car with 500hp an John has the same "Exact" car with 1200hp. Both of them have the same exact problem - Traction.

If the reason for traction is acceleration then it makes sense. But if you look at a Lotus Exige that car has tires 1/3 the size of what people here are putting on there cars.

[Track Junky]

Keep in mind, the Lotus is probably 1/2 the weight. Take a look at the Miata's for example. Less power, less tire, and most importantly less weight. But the Miata's do very well on road courses and Auto-X's.

[Vince@Meanstreets]

i'd say most of it has to do with looks. Nothing says mean like fat ass tire.
For me its both. not really for the off the line but more for the lateral grip.

[Formula43 Wheel]

New cars keep getting heavier and heavier! Just check out the weights on the new Camaro and Mustang. Brakes need to get bigger to compensate for this as well. ABS and traction control are a big help as well.

Your tire question I believe is: the overall diameter of tires for new Super Cars (Camaro, Corvette, Mustang, Challenger) are shorter than 1st & 2nd Gen. muscle cars?

If this is your question than take a look on Tire Rack at the OD for the tires these cars come stock with. They range from 26" to almost 28" in diameter. Many come stock with 20" wheels and rather than having a shorter sidewall they (the car manufacturer) have increased the sidewall diameter of the tires so not to loose ride equality.

If your referring to the tire and wheel width, than a 12" wide compared to the original 7.00X14 bias pizza cutter tires these came with 40+ yrs ago is a bit of a difference as we know.

The widest tire available with a 200 tread wear is a 345 which fits on a Viper with a 13.0" wide rear wheel.

I believe we'll see the wheel and tire sizes level off at 20". I really don't see 21" and 22" wheels and tires being stock on new cars in the future.

Lots of tire options in 18", 19" and 20" sizes now from a wide variety of tire manufacturers. The 19" and 20" tires are generally taller in OD than 18".

In general 18" tires are 25.0" to 26.0" in OD and 19" and 20" are 26.0" to 27" in overall diameter.

Not sure if this answers your question entirely, but hope it helps! :lol:

[GregWeld]

Marty -

TORQUE is what is being put to the ground for acceleration... more contact patch is going to "hook up" faster. Just look at the 10.5 tire guys on the drag strip. They're putting down big numbers with what is really a pretty "skinny" tire. But they've mastered weigh transfer... the track is gooey... and so is the tire. Put a 200 tread wear 345 wide tire on the car and it'd probably smoke 'em all the way down the 1/4 mile!

WEIGHT coupled with VELOCITY are the load forces that a Track Car is going to see in a corner - HP and TQ then really don't come into play except that the more TQ and HP a given vehicle has will obviously determine the velocity. The Mustang runs 245 X 45 Z 16's -- Hoosier R6's... they'll actually turn to liquid and stick like frigging glue once you get some temps up in 'em. Cold - they suck!

The tread wear # probably has as much to do with both of the above as does the width (contact patch). So a guy could run a skinnier tire and run 200 TW and corner and accelerate as well or better than a wider tire at 400 TW. So depending on "USE" -- the width is more about looks than actual tire loads and traction.

The part I laugh at the most is the size of the brakes on STREET CARS... because if the car doesn't have ABS -- then the most braking the car can do is whatever the TIRE / Contact patch is capable of. 6 piston Brembos - locked up are probably every bit as good as a single piston PBR.... if they're locked up and you're skidding it doesn't matter how "big" they are.

The bigger rotor and brake is about how much HEAT they can absorb and continue to function properly. On a street car - how much heat are they going to have to absorb?

So --- What Vince said is really the determining factor -- and it's all about KOOL and what looks good.... big azz tires and big azz brakes just look kool!

I was told -- because I haven't experienced it yet - that the Miatas will just run away from you on a track. They don't have to hit the brakes -- and don't have much torque or horsepower... so mat the gas and hit terminal velocity and never slow down.... "US" with bigger HP and TQ are hard on the throttle and then we scrub all that speed OFF to make the corner... Having said that - I'd prefer my Mustang and it's 590 HP motor over the Miata (yes I owned one - great little car) any day.

[GregWeld]

Joe has a car with 500hp an John has the same "Exact" car with 1200hp. Both of them have the same exact problem - Traction.



WELL -- yes they have a traction problem -- but the 1200HP car has a far larger problem. And I'm being serious here.

[parsonsj]

The part I laugh at the most is the size of the brakes on STREET CARS... because if the car doesn't have ABS -- then the most braking the car can do is whatever the TIRE / Contact patch is capable of. 6 piston Brembos - locked up are probably every bit as good as a single piston PBR.... if they're locked up and you're skidding it doesn't matter how "big" they are. That's not quite true. Bigger rotors give you more leverage to stop the car, without as much clamping force. It means that at near threshold braking the brakes are easier to control as the tire nears its loss of traction threshold. Another plus of bigger rotors is that the additional mass of the rotor itself can dissipate heat and help reduce fade -- not important on the street where a panic stop per year is too much. But on the track, every turn is a quasi-panic stop, and heat dissipation is vital.

Another way of looking at it is this: if locking the brakes was the goal... we'd still be using drum brakes, which can lock up a tire very easily.

[camcojb]

Another way of looking at it is this: if locking the brakes was the goal... we'd still be using drum brakes, which can lock up a tire very easily.

yeah, the first time you hit them........ :drive: Good info and I know what you're getting at. Just reminded me of a few times in my first drum braked cars where the second or third time trying to stop fast the car barely slowed down and I had to get "creative" to avoid hitting something. :lol:

[GregWeld]

Another plus of bigger rotors is that the additional mass of the rotor itself can dissipate heat and help reduce fade -- not important on the street where a panic stop per year is too much.


Pretty sure I pointed that out in my post.:lol:

[Vince@Meanstreets]

Miate's are cool.... http://www.rightthisminute.com/story/tight-race-between-miata-porsche-corvette big tires get it done in this case but HP didn't hurt either.

[parsonsj]

I pointed that out in my post.Yessir, you certainly did. :thumbsup: We agree on that!

[syborg tt]

The reason I started this post is I was talking with a Race Car Chassis builder. Most of the cars he build are for long tracks not short tracks like autocross at Good Guys Events.

Long story short he is building of all things an s10 pick for a gentleman that has a 250,000 porsche race car. The tire size he is putting on the truck is 275 front and 295 rear. Engine is a 383, forgot to look at the trans. He is confident that with the suspension set up and scratch built chassis it will handle every bit as good as the owners Porsche race car if not better.

They are building it for fun to beat other high end cars. Nothing like getting spanked by a little S10 pick up. When I asked him why not go bigger he kinda laughed and said ,"Son bigger isn't alway better"

By the time he was done explaining everything to me it made more sense. I figure since all this guy does is actually build track cars he must know what he's talking about. I remember a VW van that was built with the same philosphy and it surely didn't have big tires

http://www.youtube.com/watch?v=0MLCuaPdPew

[Vince@Meanstreets]

The reason I started this post is I was talking with a Race Car Chassis builder. Most of the cars he build are for long tracks not short tracks like autocross at Good Guys Events.

Long story short he is building of all things an s10 pick for a gentleman that has a 250,000 porsche race car. The tire size he is putting on the truck is 275 front and 295 rear. Engine is a 383, forgot to look at the trans. He is confident that with the suspension set up and scratch built chassis it will handle every bit as good as the owners Porsche race car if not better.

They are building it for fun to beat other high end cars. Nothing like getting spanked by a little S10 pick up. When I asked him why not go bigger he kinda laughed and said ,"Son bigger isn't alway better"

By the time he was done explaining everything to me it made more sense. I figure since all this guy does is actually build track cars he must know what he's talking about. I remember a VW van that was built with the same philosphy and it surely didn't have big tires

http://www.youtube.com/watch?v=0MLCuaPdPew

of course, purpose build and factored into design a smaller tire is fine. 275/295 isn't really considered small either. its all about balance.

[syborg tt]

of course, purpose build and factored into design a smaller tire is fine. 275/295 isn't really considered small either. its all about balance.

Hi Vince,

I agree but there are some purpose built cars on this site and the others that I lurk on and they are all going bigger is better.

btw - Don't tell Kenny I am thinking about building a road race s10. He might kill me.

[FETorino]

I am also pondering a similar question. Or I think it is similar. I am questioning the gain or lack of by increasing width.

Tire size dictates a lot on a build so I am agonizing over the rear tire size. Diameter is locked in to 27 to 28" for me. I want to keep the proportions right for a car with a big back end (1969 Torino fastback). I can fit a 285 40 19 out back and don't even think I need to touch the tubs (I run a shorter 285 40 17 now). If I do a 4 link (copy Jasons DSE install) and tub it then I could go all the way to 345.

I plan on taking the car to track day events and maybe some open road events.

I would think proper ear suspension set up makes the most difference along with track width. With DOT rubber how much lateral grip am I giving up (any really) with a smaller diameter tire 285 vs 345?

In an overly simplified scenario with all things being equal. When you increase tire size but maintain overall track width does it really make that much of a difference?