13" vs. 15" tires and wheels.....

[smokem2024]

Any advantage with 15's. What is the lightest 13"wheels

[Profile]

MARSH has 13 lbs 13 X 7 wheels.

[smokem2024]

Thanks.... the reason I ask about the 15" is there are some guys I know running them with imca tires and it just looks like it would be too heavy.?????

[Foghorn]

You are right, too heavy. It is "Unsprung Weight". The only advantage is a larger contact patch to the track which isn't a big enough advantage to use on a Ministock when you factor in the extra weight. You will also have to re-gear the car because of the larger diameter. So it will cost you time and money with a negative result. BUT, If you wait on here long enough you will find someone that likes the idea.

[return to dirt]

sorry foghorn, there are times for both. I have ran both 13 and 15 inch setups. the 13s do have less unsprung weight but it isn't a big deal on a good setup suspension. the biggest advantage of the 13s is the inertia effect on starts. they take off quicker but once you are moving there is less difference. short stop and go tracks would favor the 13. the 15s have better side and foreward bite. if the tracks you run are very rough the 15s handle it better. on a momentum track the 15s have an advantage. this all assumes the cars are equal. one or the other won't suddenly make your car a winner.

olin

[marysumali]

sorry foghorn, there are times for both. I have ran both 13 and 15 inch setups. the 13s do have less unsprung weight but it isn't a big deal on a good setup suspension. the biggest advantage of the 13s is the inertia effect on starts. they take off quicker but once you are moving there is less difference. short stop and go tracks would favor the 13. the 15s have better side and foreward bite. if the tracks you run are very rough the 15s handle it better. on a momentum track the 15s have an advantage. this all assumes the cars are equal. one or the other won't suddenly make your car a winner. olin

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[Foghorn]

I could see them maybe working on a nasty old dirt track but that's about it. My comments are always asphalt related. If the poster doesn't say what he is running on I always assume for some reason he is on asphalt. I'm bad for that. You know what they say, "Assumption is the Mother of all F&CK-UPS!"

[smokem2024]

Dirt of course. ... is there any other type of racing before the cup series.

[return to dirt]

no problem foghorn. I go the other way and assume it's dirt. I can see how the 13s could be best for pavement.

olin

[car62]

i agree,dirt is icky..but regardless, less unsprung weight,and less rotating weight will be the best way to go

[return to dirt]

foghorn and car62 have given their opinions why the 13 is better but they run pavement. dirt is different. if unsprung weight was the only factor then everyone would run a 6.75 instead of a 7.5 or like I do an 8 inch rear. as far as the rotating weight look at this. I run an 8.10 final ratio. at 8000 rpm engine speed the rear axles are only turning about 1000 rpm. if I run say a low of 6500 and a peak of 8000 that is little change in the rear axle speeds. the only time I have noticed a difference in tire size is on starts or restarts when the rpms are real low. I have noticed a bigger effect with different flywheel weights then with tire size. I have noticed a big difference in side and foreward bite with the 15s. the difference in gear ratio you change is more then just the difference in circumference of the tire. the 15s just don't slip and spin like the 13s. the only way you will know how it works is to try it yourself.

olin

olin

[little302]

Ill have to chime in here.. Im usually quiet and absent, but needed some advice so I logged on today.. We ran 15's because of cost.. Tires were plentiful in our area used from modified teams so that was the route we went..I did have to gear lower than my 13 inch counterparts, but its is a big advantage on momentum tracks as said previously. Great bite, and they dont spin as much..The only difference I have seen is more roll, maybe due to raised height, which may hurt front end geometry. No concrete evidence, but we know lower is better..I run them and have no complaints..