Question about tire sizes

Will an increase in heigth give you just as much advantage as an increase in width? For instance, will a tire that is 27 x 10.5 give you just as much traction ability as a tire that is 26 x 11.5

Height is entirely different. Traction is based on primarily on rubber compound, sidewall height/flex, tire construction, width, and height.

Generally people to go a wider tire for more traction, not taller. Taller tires change the final drive ratio.

Drag racers tend to us a smaller rim size with a taller tire and steeper gears to enhance the traction at the launch.

I went to a taller tire to be more to slow down my sixty foot times just a bit as I was running too quick for my index. You need to think through tire size changes carefully for your application. Tell us more about your setup and your goals.

My setup is moslty in my sig, at least the important parts are. Car puts down a little less than 600hp in a 6 speed. I am trying to figure out what the best tire would be. I have ran 26 x 10.5 Et streets and spun through 2nd on most passes and a couple of time in 3rd gear. My suspension includes chassis mount tq arm, relocated lcas, subframe conn and aje k-member and a-arms. Springs and shocks are stock. I know that plays into the launch a lot I just havent made it that far yet in modifying. My best 60' so far is about 1.9x on et streets. I want that way down. During my test driving over the last couple of days, the k-member and a-arms seem to make the weight transfer a lot better. I can feel the front lifting up like crazy now when I jump on it.
The reason I ask about the tires is my friend has a set of 27 x 10.5 and it brought up and interesting question to me. I found out later though that he is only selling the 15 x 10 rims and not the tires. So I guess a 28 x 11.5 would be a better solution. If I remember correctly, I was reaching the top of fourth gear with the 26" tires (its been alomst a year since I ran it). So for future modding would it be a good idea to go ahead and go up a tire size so Im not shifting into 5th gear? Thanks

Some of the guys here have much better brains for math than I do. From what you have said, a 28 tire sounds to me like iot will work better for you, maybe even a little taller, if necessary.

Footprint, sidewall, and time measurements are all important. I run 28 x 12.5 x 15 ET Streets. They have a 10" foot print. I have them mounted on 15 x 10 rims. The rim width and footprint should match.

Your sixty foot times should be below 1.5. I was cutting 1.52-1.55 sixty foot times with much less horsepower than you until I went to the larger tire size and sixty foot times are now in the low 1.6 area.

In your case, you have enough power so i would expect your sixty foot times to drop significantly as you do not even have a baseline yet from which to tweak.

I was looking at the hoosier QTP last night. 27 x 11.5 x 15. It says I can run it on a 10" wide rim so Im thinking of trying that out. I want to see if I can avoid rolling my fenders and beating in the inner panel. A friend of mine was running the 28 and was having to modify the quarter area quite a bit. But heres the thing, do i even want to start messing with tubed tires??

They should fit on a 7" offset rim. The tubes are not really a big deal. I have rim screws and tubes for mine and I do not regret it one bit. Drilling for the screws was a pain, but well worth the effort. The tubes are an extra margin of safety as slick have very thin sidewalls. The traction benefits and consistency of a well set up rim/tire combination pay big dividents on the starting line in terms of consistency and traction. You need a good light in addition to hooking up if you want to be on the winning side of the track.

Are screws required on tubed tires??

Are screws required on tubed tires??

I believe so. If the tire spins on the rim at all, whats going to happen to the tubes valve stem?

taller tire increases the contact patch moreso than a wider tire. That's why people fit the tallest tire they can get away with for the track along with optimum gearing. I use 28x10.50 and 29.5x10.50 on my camaro typically.

Good point.... so whats different with the tires that dont require tubes or does it just depend on how well you hook and how much power you have

Screws are a good idea whether they are tubed or not. As HP goes up, you generally need a larger tire diameter. At 600HP, the 26's just might not have enough sidewall.

taller tire increases the contact patch moreso than a wider tire. That's why people fit the tallest tire they can get away with for the track along with optimum gearing. I use 28x10.50 and 29.5x10.50 on my camaro typically.

It does increase the length of the contact patch but doesnt increase the width which, I think, is what increase the friction and in turn traction.

it's always better to run a taller skinnier tire than a shorter fatter for instance:

28x10.50 will hook better than a 26x11.50 if you have traction issues.

You'll have to explain that one to me please. I would think that tire of 26 x 10.50 tire with 81" of circum would spin just as easily as a 28 x 10.50 because you are just increase the "length" of the tread and not the amount (width) that has to do with the friction and traction. Does that make sense?? Unless it has to do with a litttle softer sidewall due to the increased tire height allowing it to wrinkle and take most of the shock

It does increase the length of the contact patch but doesnt increase the width which, I think, is what increase the friction and in turn traction.

Your math is flawed. The contact patch is in square inches. The length times the width. A small diameter tire at 10'' tread width with a 7'' long contact will give 70 sqin of area. A larger dia. tire at 10'' width might have an 8'' long contact giving it 80sqin of area. Equalling about a 12% increase in contact area.

Your math is flawed. The contact patch is in square inches. The length times the width. A small diameter tire at 10'' tread width with a 7'' long contact will give 70 sqin of area. A larger dia. tire at 10'' width might have an 8'' long contact giving it 80sqin of area. Equalling about a 12% increase in contact area.

The taller tire also benefits from the added sidewall.

I am in the process of switching from a 26x10x15 to a 28x9x15 and stepping up the gears to match.

I was spinning my 26 x 11.5 x 15 ET Streets by the time I was cutting 1.6 sixty foot times. That is when I did the rim screws. The last thing anyone needs is a sawed off valve stem. You also need to ream out the valve stem hole to accept a bigger (metalic) stem.

Did your 60 improve after the screws

The screws made no difference in my times but they did keep me from having to re-seat the tires and having flats.

I may be flirting with danger here, but I haven’t put any rim screws in my wheels and slicks. I just can’t bring myself to drill holes in my Alumistar 2.0s. However, I have marked the slicks, have many runs (100+) on them and they “have not” slipped on the rims.

I’m running 15” x 10” rims w/ Goodyear 28” x 10.0” slicks. Also, 4.30 gears and I have consistent 1.54, 60ft times. Additionally, the Goodyears have the stiff side-walls for heavier cars and I’m not running any tubes (which is a very common practice around here).

WD

stiff sidewalls don't need tubes, this is from a M/T rep. Also the non-stiff sidewalls we usually don't run tubes, but they will air down after a day or two, so you can't have them sitting on a car or you'll be refilling it often.

I know plenty of people who do not use rim screws and do not have a problem. However my Et Streets did spin and I saw the possibility of problems due to the slippage.

I also use tubes. Why? Although many people don't use them it it the manufacturer's recommendation and ET Streets are considered a tube type tire. Sure tubes add a minimal amount of rotating mass, but they provide an extra layer of safety (if properly installed), and especially with rim screws I figured the tubes were a good idea. Additionally, I have to check tire pressure enough as it is and the concept of increased chances for a leak are simply one more thing to worry about while during a burnout or staging that can potentially interfere with a good reaction time.

I have found generally the less distractions a driver has the better a driver can do their job.

I know plenty of people who do not use rim screws and do not have a problem. However my Et Streets did spin and I saw the possibility of problems due to the slippage.

I also use tubes. Why? Although many people don't use them it it the manufacturer's recommendation and ET Streets are considered a tube type tire.


That's why I switched to Hoosiers. Their QTPs are equalivelant to the ET streets and they are tubless tires. This year I'm trying their drag radials and I love them. 275-60x15s and I have dead hooked every pass this year. Best 60' 1.48, worst 1.53.

That's why I switched to Hoosiers. Their QTPs are equalivelant to the ET streets and they are tubless tires. This year I'm trying their drag radials and I love them. 275-60x15s and I have dead hooked every pass this year. Best 60' 1.48, worst 1.53.

I have also been very happy with my new Goodyear slicks this season. They are my first set of Goodyears, I had MTs in the past. The Goodyears with the stiff side-walls hold really well and I'm getting very consistent 60ft times around 1.54. Additionally, they are very stable down track.

WD

I'm up to a 32 x 14 MT slick now mounted on a 15" wide rim. I have 8 rim screws on both sides of each rim. I shock the tires with a high rpm transbrake launch and don't want the rims to spin in the tires.

I don't use tubes because I have a stiff sidewall tire but in about 2 weeks, the 9 psi of air I normally have in the tires is down to 2 psi.

I soaped the insides of the tires before installing them but I only had time for one coat. After this race season, I'll pull the tires and put 2 more coats of liquid soap on the inside. This will stop any leaks. The tires don't leak around the bead. The air seeps through the sidewalls.

As for your tire height question, typically racers stuff the tallest tire possible under the fenders. Wide is generally restricted to wheel well opening or a class restriction (10.5 class etc). The taller tire give a longer contact patch on the ground. This will give you better traction than a wide contact patch because a fixed point on the tire will be on the ground longer. Once you determine the tallest tire you can use, then you determine the best gear ratio to use that tall height. I started with 26" tall tires and 3.27 gears. Over the years as my car has gone faster, tires and gears have changed. I'm now at a 32" tall tire and 4.86 gears.

Maybe I do need rim-screws! A friend of mine took this picture during a launch this past weekend at the Summit Bracket Series. These are stiff side-wall Goodyears w/ 13.5 PSI. That looks like way too much side-wall wrinkle and possibly getting ready to slip on the rim!

WD

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http://shutter13.pictures.aol.com/data/pictures/08/009/5D/F7/67/CF/vyRQutFasm1DTKsVqSSC7WpQKH19dchg0300.jpg