fastvet

iTrader: (2)

Need help selecting either 26 or 28 inch tire. I used to run a 26 in tire and it would get close to redline on my M6 at the 1/4. But since then, I have upgraded to an Aluminum Fly and upped the shot of Nitrous from 100 to 150TNT kit. Car used to hit Low 500'sRWHP before I gutted cats, added the Al. Flywheel, and had half point lower compression. Returning to the Dyno soon and hoping for maybe in the 560's RWHP. My Question is, Would I definately run out of RPM if I stick with the 26inch tire or should I go with the 28inch tire??

Side note, I use to launch at 4k with the 26", if I do go with the 28", what should I launch at then??

Thanks in advance!!

RARON455

iTrader: (35)

Are you running oem wheels or aftermarket? have a set of convo pros I use at the track, my rears are 15" I split the difference and run a a set of M&H slicks that are 27". Itll give you a lil more room to breathe on the top end and still leave you some accel out of the hole. Maybe somethin for you to consider, I know I couldnt stuff that 28 in my wheelwell without trimming, now that I have the 27 Im sticking with it. You can up your launch a lil its really trial and error. I have my box set to leave at 5k, then dump the clutch, it lifts the front tires about 3 inches and then settles right back.

AGRV8D

iTrader: (19)

trans am::c5 vette

1SLwLS1

iTrader: (6)

If you were at red line before, you will definitely need a taller tire as you are making more power = more MPH. Go with 27 or 28 if applicable.

Give me your rear end specs, transmission specs, rev limit, and previous trap speed. I can lay out all of the scenarios with various OAH's.

fastvet

iTrader: (2)

Badass, I am using a 16inch rim that is off another car. So it isnt the light wheels that are out there for the Vette's. I got 4.10's on a T-56 M6. My rev limiter is set at 7000 but ishift at 6400. I just have it up there because I spray and I dont want to over rev. Previous trap speed was at 125. Anything else let me know. I appreciate ur help!!

1SLwLS1

iTrader: (6)

No Problem. These figures below assume no tire stretch, just simple mathematical calculations. Your MPH at certain RPMs will be a little lower due to the centrifugal force and various environmental conditions such as tire pressure, temperature, atmospheric pressure, etc (maybe 1/2 MPH tops).

With 26" tall tires, 4.10's and a 1.00 4th gear ratio, I show 120.7 MPH @ 6400 RPM and 132.1 MPH @ 7000 RPM. This also equates to 6626 RPM crossing the finish line @ 125 MPH.

With 27" tall tires, 4.10's and a 1.00 4th gear ratio, I show 125.4 MPH @ 6400 RPM and 137.1 MPH @ 7000 RPM. This also equates to 6380 RPM crossing the finish line @ 125 MPH.

With 28" tall tires, 4.10's and a 1.00 4th gear ratio, I show 130.0 MPH @ 6400 RPM and 142.2 MPH @ 7000 RPM. This also equates to 6152 RPM crossing the finish line @ 125 MPH.

Lets assume you pick up 5 MPH on your trap speed. Feel free to respond with what you think your trap speed will be and I can plug this back in and calculate that RPM based on your guesstimated MPH gains.

With 26" tall tires, you will be revving at 6891 RPM @ 130.0 MPH.

With 27" tall tires, you will be revving at 6636 RPM @ 130.0 MPH.

With 28" tall tires, you will be revving at 6399 RPM @ 130.0 MPH.

I would try to find a 27" tall tire depending on ease of availability, price, and MPH gain on your trap speed.

fastvet

iTrader: (2)

Ok, picking up 5mph on trap speed for a 26" tire may be the case, but if i go with a 28" tire it would probly only pick up 3mph if any, right? because its a bigger tire or am i missing something here?

I wanted the 27" tire but no one makes it on a 16" rim. So that is why I am debating on the 28". Unless someone knows of a good tire that is 27" then problem solved.

BTW, that outline is impressive!!

fastvet

iTrader: (2)

Alright I did another search for tires, These are radial tires. I guess i can go with these. What do u all think about them. They are a 27.69" tire. I havent seen this tread pattern too much, I normally see the other ones. Let me know, Thanks!!

http://www.summitracing.com/parts/MTT-3794R/

1SLwLS1

iTrader: (6)

Thanks, its just a simple excel calculator for gear comparison, transmission comparison, and gear & transmission comparison I built a while back.

Yea, you will pick up a little less with the taller tire due to the increased rotating mass and apparent reduced gear torque multiplication. This could also let you hit the tires harder off line without negative results decreasing your 60', lowering your ET and keeping a similar trap to the 26" tires. It all just depends on the variables!

If you're looking at the radials, Mickey Thompson sells a 315/45/16 under the "Street Radial II" section on their website. They label it as a 27 x 12.5 R16 and with the metric conversion, its a 27.16" tall tire. That should give you plenty of room to grow too.

fastvet

iTrader: (2)

Thanks for the imput bud! I will look those up.

stoverz28

iTrader: (8)

Are you spraying it out of the hole? I think that would determine whether or not you could turn a 28" tire.

One thing to keep in mind is that you went with a lighter flywheel therefore your car will not be able to launch as well as before.

fastvet

iTrader: (2)

Yeah I am going to be spraying 150 out of the hole. I usually launch at 4k but with the lighter flywheel I am going to have to launch higher, which I understand that. So ur saying with a 28" tire im going to have to launch even harder than what i was anticipating? Maybe 5000rpm?? Or will the extra 50hp of nitrous be ok to launch it at 4500rpm and be ok all around??

1SLwLS1

iTrader: (6)

I would leave as high as you can get traction.