28" Slicks On Lowered Bird?

DrFishbone

SCCoA Member
Just wondering if anyone else is running 28" diameter slicks (on 16" sc wheel)...especially on a lowered car.

I'm switching to 3.07 gears and also considering buying 28" x 11.5-10.5 Hoosiers for the rear. It looks like the will fit, but it will be close.

My thought is more sidewall to flex and absorb driveline shock for the 5-speed launch. Could also go to 15" TBird wheels, but would have to reduce the width, since they are 1" (I think) narrower.

Opinions / experience?
 
I'm starting to think 28" will be too tall to use with 3.07 gears...might have trouble getting moving (60fts)....hmmmm
 
Neibert is running 28" tires. His car is lowered, but his fenders are rolled. I mounted them on my car which is a little lower and doesn't have rolled fenders, and I put a few lines in the tires just driving around the block. Of course his wheels are not stock and therefore the offset might be different. Still, I'm convinced that I cannot run 28" tall tires on my car without rolling the fenders.
 
I did ghetto roll my fenders with a baseball bat for my Cobra Rs...might be able to go a little further if needed. I bet they would rub bad without rolled fenders.
 
I did ghetto roll my fenders with a baseball bat for my Cobra Rs...might be able to go a little further if needed. I bet they would rub bad without rolled fenders.
Don't forget about tire growth (depending on what tire you are running)
 
I run 28's on my lowered car with lips rolled. And my wheels are 10" wide they stick out alot further than stockers, no problems. The tires are MT ET Street 28x11.50x16 which the tread width is only like 8". Now a full slick usually has a wider tread width so they may not work with my wheels. But I did have a full slick on mustang v6 wheels with no problems either. Also I believe Casey had some 31"ers on the green car.
 
I have 28" full slicks on my car now with 15" wheels. But with the new rear it's really not a fair comparison. I've modified the wheel wells pretty heavily to get them to tuck in.
 
I remembered Casey had some big tires on the tank...wasn't sure what size.

Also, I was wondering (concerning growth)...does the tire diameter = relaxed, uninstalled diameter, installed diameter (with assumption on rim dimensions), or a max "grown" diameter(given wheel diameter and a speed)?

:confused:
 
Okay...found a handy-dandy before/after calculator....

http://www.4lo.com/calc/geartire.php

Right now I have 2.73 rear gears + 26" diameter slicks. If I were to switch to 3.08 rear gears + 28" slicks, I would effectively be switching my ratio to 2.86:1 over the existing 2.73:1...not very much of a change! But, I'll have more sidewall....pros and cons....

Now, I don't really want to go to 3.27+ because of all the street driving I do with the car, but....

3.27 gears + 28" tire would be an effective change to 3.04:1

3.55 gears + 28" tire would be an effective change to 3.3:1

I'm starting to see one clear reason why most street/strip people stick with the 26" diameter tires! :eek:

15" wheels are starting to look good....I think I could fit some 10.5" wides on a stock T-bird rim...current setup is 11.5" on a 7.5" SC rim should be able to do 10.5 on the 6.5" LX rims...I bet it would get pretty wobbly with the tall tires on the far end of the track though. :(

Maybe I should just plan on 3.27's & a bigger tire/wheel combo for street driving too. :D
 
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Good idea...

Matt,

This was with Hoosier 28" x 11.5" x 16" QTP DOT slicks on my 93 SC with Bogart 8.5" x 16" wheels at stock ride height. No rubbing at stock height, but since adding the 3/4" Drop Volgtland springs I'm hitting the fender lips when launching and will need to roll them or fill the air bags to max pressure.

garage_attachment.php




Same wheels and tires on my 91 SC with rolled fenders and H&R 1.5" springs aren't a problem and don't require adding as much air to the bags. It doesn't squat nearly as much launching because the 93 SC is using a trans brake and the 91 SC just uses a foot brake. It was necessary to remove most of the plastic fender liner from both cars to keep from rubbing the tires.



garage_attachment.php



David
 
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I forgot about the fender liner. I believe you just have to trim the passenger side behind the tire where the liner squares off.
 
Here are some pics of Hoosiers bias ply slicks, 28/10.5/15 on 8" rims with a 5" backspace. I have Eibach 1.5" springs and the fender lips rolled. I run tubes and rim screws with 12 psi tire pressure.
 

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Okay...found a handy-dandy before/after calculator....

http://www.4lo.com/calc/geartire.php

Right now I have 2.73 rear gears + 26" diameter slicks. If I were to switch to 3.08 rear gears + 28" slicks, I would effectively be switching my ratio to 2.86:1 over the existing 2.73:1...not very much of a change! But, I'll have more sidewall....pros and cons....

Now, I don't really want to go to 3.27+ because of all the street driving I do with the car, but....

3.27 gears + 28" tire would be an effective change to 3.04:1

3.55 gears + 28" tire would be an effective change to 3.3:1

I'm starting to see one clear reason why most street/strip people stick with the 26" diameter tires! :eek:

15" wheels are starting to look good....I think I could fit some 10.5" wides on a stock T-bird rim...current setup is 11.5" on a 7.5" SC rim should be able to do 10.5 on the 6.5" LX rims...I bet it would get pretty wobbly with the tall tires on the far end of the track though. :(

Maybe I should just plan on 3.27's & a bigger tire/wheel combo for street driving too. :D

I'm not sure I understand what it is you are trying to accomplish here, but if it helps any I am running 28" MT E/T Streets on standard 16" SC wheels with 3.08 gears.

Ira
 
Okay...found a handy-dandy before/after calculator....

http://www.4lo.com/calc/geartire.php

Right now I have 2.73 rear gears + 26" diameter slicks. If I were to switch to 3.08 rear gears + 28" slicks, I would effectively be switching my ratio to 2.86:1 over the existing 2.73:1...not very much of a change! But, I'll have more sidewall....pros and cons....

Now, I don't really want to go to 3.27+ because of all the street driving I do with the car, but....

3.27 gears + 28" tire would be an effective change to 3.04:1

3.55 gears + 28" tire would be an effective change to 3.3:1

I'm starting to see one clear reason why most street/strip people stick with the 26" diameter tires! :eek:

15" wheels are starting to look good....I think I could fit some 10.5" wides on a stock T-bird rim...current setup is 11.5" on a 7.5" SC rim should be able to do 10.5 on the 6.5" LX rims...I bet it would get pretty wobbly with the tall tires on the far end of the track though. :(

Maybe I should just plan on 3.27's & a bigger tire/wheel combo for street driving too. :D

Well that all depends on what RPM and gear you want to trap at. Looking at your old setup with an early model trans and the 107 MPH in your sig you trapped at 6200 rpm. Which maybe too much for your motor I don't know. Now if you went to 4th on that run you went thru at 4500 rpm which is prolly too low.

If you want to trap at 6k at 107 mph with the 28" tires in 3rd gear(less gear changes) you should stick with the 2.73's they are perfect.
 
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