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Hey guys,

Headin to the drag strip this coming friday and was just wondering if I bolted a couple spares to the front of the car as skinnies.... would they explode?
The car ran a 12.6 best so far. Weighs 3450lbs.
 

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I've seen people do it before. Running those times you should be ok, but you better check your track rules; most of them will not let you run on them. I do not recomend doing it. You are taking a risk for a very small gain.
 

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Those spares are only rated to 55 MPH I believe. Read the sidewall.

I also don't think you will pass tech inspection.
 

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Skirt Chasing Philanderer
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Those spares are only rated to 55 MPH I believe. Read the sidewall.

I also don't think you will pass tech inspection.
+1

It depends on your track though. I have seen guys run spares on the front but have also seen people not be able to run their cars because of them. Just depends how tough tech insp is...

Personally, I wouldnt run them as I wouldnt risk one of my cars cause I cheaped out on skinnies.
 

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The Despised Vert
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just because someone else did it w/o problems doesn't mean it will work for you... I hit some fluid on the track just before the finish line and the rear broke completely loose.. I thought I was going to hit the wall cross track but was able to steer through it.. doubt I would have had the same results with wanna be skinnies... there is a reason they are expensive...
 

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Tires are rated at 86mph;). That's a sustained speed of 86mph for 1 hour. You'll be fine for 12.6 seconds.
MMM, yeah, but you are doing 117 MPH or so. That far exceeds the forces the spare was designed for.

It would be a real bummer to blow one and crash into the wall trying to save a tenth due to not doing something the "correct" way.
 

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I Poop Entirely Way Too Much
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MMM, yeah, but you are doing 117 MPH or so. That far exceeds the forces the spare was designed for.

It would be a real bummer to blow one and crash into the wall trying to save a tenth due to not doing something the "correct" way.
Its not forces so much as heat. A lil tires heat up faster then a larger tire. GOin down the track your not turning much at all and most of the weight will be on the rear tires since your accelerating hard.

Also remember theres a factor of safety put into that max limit. so the incase you want to push it and do 60 when the limit is 55 and dont even realize and do 60 your tire wont blow out. If the tire doesnt make a few drag strip passes theres somethin wrong with it.
 

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they're fine...

and that gain aint so minimal....
 

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The Despised Vert
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risk/reward.... I wouldn't do it... but thats just me...
 

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Speed rating isn't the max speed a tire can go. It's a speed a tire can go for long distance. Hitting 117 isn't going to be an issue. The only problem I see is maybe a handling or braking issue with such small tires.
Speed ratings are based on laboratory tests where the tire is pressed against a large diameter metal drum to reflect its appropriate load, and run at ever increasing speeds (in 6.2 mph steps in 10 minute increments) until the tire's required speed has been met.

Tire Tech Information - How to Read Speed Rating, Load Index & Service Descriptions

Temporary spares typically carry an M speed rating...which is 81 MPH - although my MAxxis spare in my mustang has both the M speed rating on the sidewall as well as "TEMPORARY USE ONLY - MAX VEHICLE SPEED 50 MPH" on the sidewall.

Although I agree, based on my reading, that sustained speed and temperatures are the largest factor in speed ratings - no doubt about that - but they are not the only factor. Tire design and therefore speed ratings also include calculations based on the centrifugal forces the tire carcass and tread area experience.

Centrifugal forces on the tire tread increase as the square of the speed. When a tire fails, it is typically in the belt/tread area, not the sidewall.

Using this calculator...

Wheel And Tire Motion Calculator

at a rim diameter of 17 inches (which is what my spare is) and a sidewall height of 4 inches (rounded) I calculate 160 G's on the tread at 50 MPH.

Moving to the tires M rating of 81 MPH and all other factors the same, we are now pulling 420 G's on the treads.

At 117 MPH at the end of the quarter mile: 877 G's - more than double what the tire was rated for.

Can the tread design handle that? I have no clue, I wasn't the engineer...but rest assured the engineer who designed that tire probably never thought a temporary spare would see 117 MPH.

I think you could probably do it. But I am saying I wouldn't. Does the benefit outweigh the potential risk?

Why no contact Maxxis and ask:

Maxxis Tires
 

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I think you should do it. I wanna see what happens lol :popcorn
 
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