tire width vs performance???
04-06-2010, 11:54 PM
#1
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tire width vs performance???
okay I understand that a wider tire will have more mechanical grip..but they also are heavier and have heavier wheels? So here is my quandary?
On my 84 "lemons" racer we run stock forged (think light) 16x7 wheels with 225/50-16 tires....I am VERY happy with how the car handles...I just would like a touch more braking and accelerating traction....its far to easy to lock up the brakes or spin 1 tire (open diff
)....
So for an exact same tire...how much "traction" advantage would running say a 275/35-18 tire on 18x10 rims..I'm sure it would "feel" better...but how much improvement would it make in lap times? The downside I can see (other than COST) is the tires a 6lbs each heavier and the wheels are probably 10+lbs heavier each...so the car would gain 64+lbs in rotating weight......
The tires will be the same..just larger...so we are going from about 8.8" actual width per tire to 11.2" per tire...& yes it will fit....
On my 84 "lemons" racer we run stock forged (think light) 16x7 wheels with 225/50-16 tires....I am VERY happy with how the car handles...I just would like a touch more braking and accelerating traction....its far to easy to lock up the brakes or spin 1 tire (open diff
).... So for an exact same tire...how much "traction" advantage would running say a 275/35-18 tire on 18x10 rims..I'm sure it would "feel" better...but how much improvement would it make in lap times? The downside I can see (other than COST) is the tires a 6lbs each heavier and the wheels are probably 10+lbs heavier each...so the car would gain 64+lbs in rotating weight......
The tires will be the same..just larger...so we are going from about 8.8" actual width per tire to 11.2" per tire...& yes it will fit....
04-07-2010, 12:02 AM
#2
Burning Brakes
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On a normally aspirated 944 I'd think 225 would be enough tire. It's not enough power to need more traction on acceleration, IMHO. If you're spinning a wheel on corner exit then just try to be smoother. Are you saying its to be raced as a Lemons race car or were you just making a joke?
04-07-2010, 12:59 AM
#3
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On a normally aspirated 944 I'd think 225 would be enough tire. It's not enough power to need more traction on acceleration, IMHO. If you're spinning a wheel on corner exit then just try to be smoother. Are you saying its to be raced as a Lemons race car or were you just making a joke?
Its a 928...racing weight is about 3150lbs......so its 196whp 233 torque going through a open diff automatic (not ideal I know but its lemons)....and yes we DO race it in lemons....going into our 3rd race!!!
04-07-2010, 04:37 AM
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OH ok 
For a 928 I guess bigger tires would make a lot more sense. Why F with it and spend more money though? If that 928 is actually holding up through the races you have to be killing the other cars anyway! If you start "developing" a lemons car to go faster you may as well be club racing! Bigger tires will need stiffer suspension, etc...If I'm getting this Lemons thing it's race what you got!
We're building a 1995 Integra Lemons car that should be finished this week actually
For a 928 I guess bigger tires would make a lot more sense. Why F with it and spend more money though? If that 928 is actually holding up through the races you have to be killing the other cars anyway! If you start "developing" a lemons car to go faster you may as well be club racing! Bigger tires will need stiffer suspension, etc...If I'm getting this Lemons thing it's race what you got!We're building a 1995 Integra Lemons car that should be finished this week actually
04-07-2010, 11:40 AM
#7
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Brian, go to your room!
forget about the tires! the car is MORE than fine. you start making it better and you (we) will get crushed.
as far as the question, yes, more often than not, larger tires offset the weight with more grip. as Ive posted before, weight on the tire, only has the effect as if 2x the weight was in the car. 10:1 HP to weight ration will value that weight at about 1hp per 10 lbs for acceleration loss, BUT, faster cornering speeds and exit speeds will off set it and in more cases, be enhanced for a slightly lower lap time.
There is a point of diminishing retun. each car will have its optimal tire size based on its weight, hp and driver capabilties. For example, in your lower powered 928, 225 to 255/275 is a huge gain, while putting the 305s on might not be that much better.
Are you talking about using the car in NASA GTS2?
forget about the tires! the car is MORE than fine. you start making it better and you (we) will get crushed.
as far as the question, yes, more often than not, larger tires offset the weight with more grip. as Ive posted before, weight on the tire, only has the effect as if 2x the weight was in the car. 10:1 HP to weight ration will value that weight at about 1hp per 10 lbs for acceleration loss, BUT, faster cornering speeds and exit speeds will off set it and in more cases, be enhanced for a slightly lower lap time.
There is a point of diminishing retun. each car will have its optimal tire size based on its weight, hp and driver capabilties. For example, in your lower powered 928, 225 to 255/275 is a huge gain, while putting the 305s on might not be that much better.
Are you talking about using the car in NASA GTS2?
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04-07-2010, 02:43 PM
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Brian, go to your room!
forget about the tires! the car is MORE than fine. you start making it better and you (we) will get crushed.
as far as the question, yes, more often than not, larger tires offset the weight with more grip. as Ive posted before, weight on the tire, only has the effect as if 2x the weight was in the car. 10:1 HP to weight ration will value that weight at about 1hp per 10 lbs for acceleration loss, BUT, faster cornering speeds and exit speeds will off set it and in more cases, be enhanced for a slightly lower lap time.
There is a point of diminishing retun. each car will have its optimal tire size based on its weight, hp and driver capabilties. For example, in your lower powered 928, 225 to 255/275 is a huge gain, while putting the 305s on might not be that much better.
Are you talking about using the car in NASA GTS2?
forget about the tires! the car is MORE than fine. you start making it better and you (we) will get crushed.
as far as the question, yes, more often than not, larger tires offset the weight with more grip. as Ive posted before, weight on the tire, only has the effect as if 2x the weight was in the car. 10:1 HP to weight ration will value that weight at about 1hp per 10 lbs for acceleration loss, BUT, faster cornering speeds and exit speeds will off set it and in more cases, be enhanced for a slightly lower lap time.
There is a point of diminishing retun. each car will have its optimal tire size based on its weight, hp and driver capabilties. For example, in your lower powered 928, 225 to 255/275 is a huge gain, while putting the 305s on might not be that much better.
Are you talking about using the car in NASA GTS2?
Isn't unsprung weight (wheels/tires etc) equal to 4 times sprung weight?
Isn't it true that running wider tires where suspension alignment and camber isn't adjusted to take maximum advantage of dynamic contact patch/side slip angle a waste of money?
04-07-2010, 06:18 PM
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With respect to suspension tuning a sports car, is it true that given the choice between lowering center of gravity or wider tire tread, lowering center of gravity is the more beneficial choice? (I'm speaking in general here)
04-07-2010, 06:58 PM
#11
Race Director
Yes.
Lowering the CG is very important in making th car perform as it is one of the few things that reduces weight transfer. However lowing the the CG is never simple an easy and of lowering the CG causes other compromises. Wider tires are easier to put on and have less impact in potentially negative ways.
So impractice a wider tire is often better.
Lowering the CG is very important in making th car perform as it is one of the few things that reduces weight transfer. However lowing the the CG is never simple an easy and of lowering the CG causes other compromises. Wider tires are easier to put on and have less impact in potentially negative ways.
So impractice a wider tire is often better.
04-07-2010, 07:23 PM
#12
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Why do you say that and what do you mean?
That is way too general and in most cases completely untrue.
Ive done this from 225s to 305s, as well as others and have not changed alignment with benificial results in all areas, including treadwear.
That is way too general and in most cases completely untrue.
Ive done this from 225s to 305s, as well as others and have not changed alignment with benificial results in all areas, including treadwear.
04-07-2010, 07:46 PM
#13
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Thread Starter
Right now the car handles pretty well with max caster & max camber (about 2.5' all around) with toe set to neutral in front and a touch in out back....Kibort races the car with me...so he can speak to its strengths and weaknesses....
We DO NOT have a hard time keeping up with the fastest cars out there.....our car as it sits is a top 5 overall car...in terms of fastest lap times...& we don't have to push super hard either.....
I'm just looking for ways to make it faster............or maybe even NASA GTS2...since its power to power-weight right now is just at the limit for GTS2....its times are competitive with other GTS2 cars like Spec E30's and its running a one legger automatic with (good) street tires
Does NASA allow automatics? I know SCCA doesn't unless the driver is disabled?
We DO NOT have a hard time keeping up with the fastest cars out there.....our car as it sits is a top 5 overall car...in terms of fastest lap times...& we don't have to push super hard either.....
I'm just looking for ways to make it faster............or maybe even NASA GTS2...since its power to power-weight right now is just at the limit for GTS2....its times are competitive with other GTS2 cars like Spec E30's and its running a one legger automatic with (good) street tires
Does NASA allow automatics? I know SCCA doesn't unless the driver is disabled?
04-07-2010, 08:03 PM
#14
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compare your video time with the old configuration vs the configuration we ran at Sears and see the time difference. (long turn 7 plus the indy chicaine at 9)
I think its about 17-20 seconds slower, so even with 20 seconds off our best time of 2:17, its only about a 1:57-2:00 spec e30s run in the 1:53 range, and spec miatas run in the 1:55 range. However, we were on pure street tires, and small ones at that, SO, with my set of DOT slicks, knock off a full 4 seconds easy. in GT2, that would be competitive, but I dont think you can race an automatic.
Certainly, it would be a 1:55-7ish car with DOT slicks
Better check with nasa.
mk
I think its about 17-20 seconds slower, so even with 20 seconds off our best time of 2:17, its only about a 1:57-2:00 spec e30s run in the 1:53 range, and spec miatas run in the 1:55 range. However, we were on pure street tires, and small ones at that, SO, with my set of DOT slicks, knock off a full 4 seconds easy. in GT2, that would be competitive, but I dont think you can race an automatic.
Certainly, it would be a 1:55-7ish car with DOT slicksBetter check with nasa.
mk
Right now the car handles pretty well with max caster & max camber (about 2.5' all around) with toe set to neutral in front and a touch in out back....Kibort races the car with me...so he can speak to its strengths and weaknesses....
We DO NOT have a hard time keeping up with the fastest cars out there.....our car as it sits is a top 5 overall car...in terms of fastest lap times...& we don't have to push super hard either.....
I'm just looking for ways to make it faster............or maybe even NASA GTS2...since its power to power-weight right now is just at the limit for GTS2....its times are competitive with other GTS2 cars like Spec E30's and its running a one legger automatic with (good) street tires
Does NASA allow automatics? I know SCCA doesn't unless the driver is disabled?
We DO NOT have a hard time keeping up with the fastest cars out there.....our car as it sits is a top 5 overall car...in terms of fastest lap times...& we don't have to push super hard either.....
I'm just looking for ways to make it faster............or maybe even NASA GTS2...since its power to power-weight right now is just at the limit for GTS2....its times are competitive with other GTS2 cars like Spec E30's and its running a one legger automatic with (good) street tires
Does NASA allow automatics? I know SCCA doesn't unless the driver is disabled?
04-07-2010, 08:57 PM
#15
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Also keep in mind that tire temperature comes into play. If you go too wide and the tires don't come up to optimal temperature across the section, you won't get maximum available grip. I'm no pro, I just remember hearing this from more than one very successful race preparation shops when I asked about just going wider with the tires...