Give me the 'Skinny'

[chevy72blu]

Ive been thinking about buying a set of skinnies for the front, to aid in overall gear ratio more than the coef. of rolling friction and weight reduction (those things are nice too).

Right now I have a 28x14" wide Hoosier DOT slick mounted on a 15x10" steel UNIQUE wheel. I plan on selling my UNIQUE's (they were a birthday present) and getting something with an inch or 2 more BS (my slicks stick out of the fender about 3/4" and im swapping to trailing arms anyway).

Truck has a 3.73 ring gear and TH350, with a 28.5 inch tall tire in the front (street rubber) mounted on a 15" x 8" aluminum Ultra sixgun wheel. The truck will be driven on the street occasionally and I want to keep the 3.73's for a while.

With my SBC, it was running through the traps at about 4700 RPM (1/4mi). I havent yet had it on the track with my BBC.

I would like to get my trap RPM up a few hundred by going with a shorter tire up front. How short/wide should I go? Is the truck going to be much harder to steer? I have no experience with skinnies.

[bigjimzlll]

The front tires have nothing to do with rpm. The only advantage is less windage, weight and the height can change the roll out on the starting line.(increase or decrease reaction time)
Now changing the rear tire height will change rpm/gear ratio.

[djracer]

Sounds like you need some 4.10/4.11's in the rear. That tire is short enough in my opinion. The taller the tire the larger the contact patch on the ground is.

[cdowns]

the shorter and skinner a front tire is the easier it is to turn

[chevy72blu]

Hmm.. That doesnt really make sense to me.

Tire height obviously impacts your overall gear ratio. A taller tire given the same rear end gear and transmission will translate to lower RPM at the same speed. The same is true vice versa.

I dont see how a rear tire would affect the overall ratio but a front tire wouldnt?

It would seem to me that your overall tire height would be front height + rear height/ 2.

Thus, a 28" tall rear tire and a 24" tall front tire would yield an equivalent of rotational speed equal to a 26" tall tire all the way around.

Sorry if I was unclear in my first post. Am I missing something here?

[blackedoutharley]

There are no gears in the front to have a ratio (unless its 4x4) affected by front tire size changes.

As stated, the front tire height will affect roll out in the starting line beams which affects reaction times as well as e.t. to some degree. A larger tire with alot of rollout will keep the beams blocked longer which has the effect of getting a running start on the lights which will make the e.t. lower in most cases.

The front tires have nothing to do with engine rpm because they are not connected to the engine.

[chevy72blu]

Ok, ive figured it out now. I've taken more than a few physics classes and gotten into quite a bit of angular momentum, and I was applying that. The this is, I was thinking about it as though they were cog gears (or some similar analogy). It didnt make sense to me because a smaller tire in the front will rotate faster at the same speed as taller tire in the back. BUT, the front tire is free to rotate at whatever speed it is being driven at with no mechanical impact on the system.

Sorry for my ignorance.

It seems like money would be much better spent on a set of 4.10's. It wasnt more than a few years ago that I put a brand new set of 3.73's in it, but oh well. I'll see how it goes down the quarter before making the change.

Thanks

[blackedoutharley]

No worries, you learn by either doing it (right or wrong) or by asking.

I would run it with the 3.73's prior to making any changes to the rearend.

According to my calculator a 28" tire and 3.73 gears at 4800 rpm should put you at about 107 mph.

With all things remaining the same except the switch to 4.10's your speed will drop to 98 mph at the same rpm. For drag racing you will get better 60' times but your mph will decrease, provided it hooks up.

If you drive it on the street for any amount of time or distance you will hate the 4.10's (and so will your wallet at current fuel cost). I had 3.73's in my truck and it was a blast to drive but the 3.42's are much better on the freeway.

Good luck and how about some photos ?

[chevy72blu]

The I DD'd the truck with a 355 for 3 years driving about 60 miles round trip per day. Since then the truck has been retired during the BBC swap and having only a weekend to a week every couple months while im home from school to work on it.

Its a street/strip machine that will rarely be driven, so 4.10's arent out of the question, but like I said, I wont make the change until I see how it runs.

There are tons in my build page (link in my signature), but these are my favorites:

SBC powered:

[D13]

Yer carby's on krookd.


great truck, love that paint, reminds me of my longhorn (except for the woodgrain).

[ton*loc]

i tink it is the "sidewinder"

[chevy72blu]

Originally Posted by ton*loc

i tink it is the "sidewinder"

Its an original Edelbrock Torker. I could have went with a better performing intake... but it is an "old school tech" build and I really dig the look of it.

[PA-IndianRider]

Originally Posted by chevy72blu

Its an original Edelbrock Torker. I could have went with a better performing intake... but it is an "old school tech" build and I really dig the look of it.

Yeah I feel the "same" way.... willing to sacrifice "some"performance for the "old school LOOK"

[redhead69]

[QUOTE=blackedoutharley;2788285]No worries, you learn by either doing it (right or wrong) or by asking.

"I would run it with the 3.73's prior to making any changes to the rearend.

According to my calculator a 28" tire and 3.73 gears at 4800 rpm should put you at about 107 mph.

With all things remaining the same except the switch to 4.10's your speed will drop to 98 mph at the same rpm. For drag racing you will get better 60' times but your mph will decrease, provided it hooks up. "

I disagree, if you go with a 4.10 your going to cross the finish line at higher rpm and pickup some mph too. Respectfully
Red

[scatesracing]

Mine likes to push the front wheels If I dont slow way down on sharp turns........... I have even had it yank the wheel out of my hands pulling into a driveway........ not sure wich is more to blame the spoll and 14" wides out back or the 3.5s up front........ But it looks kick so you just change the way you drive... my .02$ Travis

[regan wilson]

Twenty years ago I had 29.5x10.5 slicks on an 8inch wheel with stock tubs . It was lowered and the wheels fit inside . Only problem was it would rub on the inside of the tubs if you didnt turn real slow . The motor was an 11.5 to 1 468 basically an LS6 . It had a big solid cam (cb310 comp cam w/637 lift) a strip dominator manifold and an 850 Holley it made around 600 hp . The converter was a #2422 TCI 10" 4500 stall . It also had a fogger and a cheater on it . With 4.56 gears it would run 11.teens at 117 at around 6300-6400 rpm . With the plate it would run 10.50's at 128 . With both systems it would run 10.30's at 130 at 6800 rpm spinnin all the way down the track . So if you got enough motor , believe me 4.10's will work and 4.56's might even work better .