gman73

Does having smaller diameter tires hurt my performance in the 1/8 mile? No 1/4 mile tracks around. My tire diameter is 25.7. My car is a manual and I have 4.10 gears.

mike08

i thought larger diameter tires hurt performance

Stkjock

the answer is it depends..... a smaller tire give you more effective gear.... a larger tire less. there are too many variables to have a simple answer to this question. For instance if a bigger tire allows ur car to hook better and get thru the traps with one less gear change it'll help. if the smaller tires lets you cut yoru 60' due to the increase in gear it helps.... etc etc etc

gman73

With the smaller diameter tires, I am essentially have 4.30 gears, but what I think would hurt my 1/4 mile is the extra gear shift, but I am not effected by the extra gear shift on the 1/8 mile.

Stkjock

what are you traping?

i have effective 4.24 iirc (26.4" tire) and I'd have to shift long b4 the traps when I had 3.55s anyway... so the 4.10s didnt matter in my case...

gman73

The last time on the 1/8 mile track I trapped at 77.304; the corrected sea level trap would be about 78.5.

Stkjock

well I meant the 1/4... but in the 1/8th your still in 3rd so IMO the smaller diameter is helping.. if your trap in the 1/4 is 107(iirc) or more the smaller tire doesnt matter much. under that its boarderline and as you could maybe stay in 3rd

Vapour Trails

You're better off with shorter gearing if even it means an extra shift.

Vapour Trails

Do you have an intake? That seems low.

kazman

The rear tire diameter and gear ratio give you and over all ratio. You want to cross the finish line 100-200 rpm above your peakrpmHP. Reducing a shift may help if your having issues shifting. If your bracket racing you really don't want to shift just before the finish line especially in the 1/8 mile. Larger diameter tirescushionthe shock on the launchbecause they have more sidewall and therefore hook better.Also note that a 25" tire on a 15" wheel will have more sidewall than a 25" tire on a 17"wheel.

BALL PARK EXAMPLES BELOW:
(3.73 gears + 25" diameter tires) = (4.11 gears + 27" tires) = (4.33 gears + 28" tires) = (4.56 gears + 30" tires)

Bigger tires will hook more but need more HP to run you down the track. You need to find a the smallest tire that will hook (width wise) plus you need to see what RPM you cross the finish line. Last thing is to decide if you want that extra shift and where it occures. If your bracket racing you want to "over" tire the car (able to dead hook on spit).