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Discussion Starter #1
After going from a 305 17in tire to a 295 20in tire i'm getting bad wheel hop if i try a burn out. I'm not someone who runs around smoking the tires all the time but i've done them before (a year or so ago) w/ the 305's. Would just switching tire sizes have that much of an impact on traction? the 305's had plenty of tread left too so.....

Any input is welcome.
 

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Can not comment on burn outs, but I have had two cars that developed major suspension changes after changing the tire/rim combination. The wheels are "un suspended weight" and can change the way your shocks and springs react. In one case I changed from steel rims to aluminum which I guess at a 10Lb change. The other car I just went to smaller tires.


The second issue is that lower profile tire also change your suspension rate.
 

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Agreeing with ZO- I'd add that you might be seeing affect of worn or failing control arm bushings - hell, even unloading of u-joints if exceeding their design range. Regardless of wheel size how do overall tire diameters compare old v. new?
 

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Large tires like 20"+ are much more rigid due to the lack of a sidewall.
They just cannot flex/give like a smaller tire.

I have a friend with a Magnum wagon he has 24"? and cannot do a burnout to save his life. Wasn't a problem with the stock 17" tires.
 

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Discussion Starter #5
Agreeing with ZO- I'd add that you might be seeing affect of worn or failing control arm bushings - hell, even unloading of u-joints if exceeding their design range. Regardless of wheel size how do overall tire diameters compare old v. new?
Tires: from 315/35/17 to 295/30/20
Rear suspension (maybe 15k miles):
* Hotchkiss springs
* Bilstein shocks
* BMR rear sway bar
* BMR rear LCAs

You can see, not a huge difference in side wall from the 17 to the 20. I wouldnt think businhing would go bad at 15k but i'll have to inspect them maybe this weekend.
 

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Discussion Starter #6
Large tires like 20"+ are much more rigid due to the lack of a sidewall.
They just cannot flex/give like a smaller tire.

I have a friend with a Magnum wagon he has 24"? and cannot do a burnout to save his life. Wasn't a problem with the stock 17" tires.

Changing from 315/35/17 (obviously not stock tire height) to 295/30/20 isn't much of a reduction in side wall so i would think there'd be that much of a change but i've been wrong many time before.
 

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Tires: from 315/35/17 to 295/30/20.....You can see, not a huge difference in side wall from the 17 to the 20.....
Actually, you have about an 1" difference in the sidewall going to the 295/30-20 tires....fairly significant.

Further, stock (OEM) tires for the Impala (255/15-17) have a 5" sidewall; 1 1/2" more than your current tires.

While your old 315/35-17 tires may not have reached a threshold of good sidewall flex, it's very probable that your 20" tires did. PARTICULARLY if you still have a stock-ish suspension.

Lower profile tires + bigger/heavier rims + stock-ish suspension = bad combination. :(

KW
 

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Discussion Starter #8
Actually, you have about an 1" difference in the sidewall going to the 295/30-20 tires....fairly significant.

Further, stock (OEM) tires for the Impala (255/15-17) have a 5" sidewall; 1 1/2" more than your current tires.

While your old 315/35-17 tires may not have reached a threshold of good sidewall flex, it's very probable that your 20" tires did. PARTICULARLY if you still have a stock-ish suspension.

Lower profile tires + bigger/heavier rims + stock-ish suspension = bad combination. :(

KW
I guess the rear suspension is stockish, in that its lowered and just a bit beefier than normal.

Rear suspension (maybe 15k miles):
* Hotchkiss springs
* Bilstein shocks
* BMR rear sway bar
* BMR rear LCAs

So i guess the next question is what else can i do to reduce wheel hop w/ the new tires? The car makes about 350hp at the wheels w/ 4.10 gears so power isn't an issue.
 

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....
So i guess the next question is what else can i do to reduce wheel hop w/ the new tires? The car makes about 350hp at the wheels w/ 4.10 gears so power isn't an issue.

IDK if it's the correct term, but you must have some harmonics thing manifesting itself that can't be absorbed by the sidewall. Look at me talkin' lika engineer.. Still, my first (and least costly) experiment would be changing tire pressures, and then either stiffer (or even counter-intuitively = softer) shocks to change up the cycle frequency. Then the same with the coils.
 

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IDK if it's the correct term, but you must have some harmonics thing manifesting itself that can't be absorbed by the sidewall. Look at me talkin' lika engineer.. Still, my first (and least costly) experiment would be changing tire pressures, and then either stiffer (or even counter-intuitively = softer) shocks to change up the cycle frequency. Then the same with the coils.
That is similar to what I was going to write. It could be the sidewall, or the entire package. Changing one part may stop the wheel hop. There is a certain amount of compliance built into the suspension, and depending on the stiffness of the upgraded part, it may match the frequency of the assembly to the pulsations of the input, causing a positive feedback loop...and you get wheel hop.
 

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OP

while your tire size/profile/rim is causing new issues, some may be resolved with tire pressure change and or "adjustable" rear shocks.....you should consider adding Dick Miller triangulation braces
 

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Are the 20's a better hooking/stickier tire? I've seen a lot where severely traction limited cars DIDN'T get wheel hop, but when you install a stickier tire you start to bring out the flaws in the suspension setup. If a tire is spinning with hardly any resistance, you're probably going to get nice, smooth burnouts. Put on a sticky tire that is really attempting to bite, and you start loading and unloading the suspension as the tire hooks, weight transfers and then spins again.
 

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Marky -



The narrative refers to 5029, and the part no. pulldown indicates -W for our car. You know something special? or just a typo eh.


Oh and yes, I have them and hartilly agree benefit.
 

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SSandman touches on a good point...your "new" tires very well may have better "traction" than the older tires you had so they likely would not break lose as easily.....and lead to the wheel hop you now have

If your new tires are also taller than your old ones your rear gear ratio got a little shorter mathematically making it harder to break the tires lose....especially if you are power braking to do the burn out (holly F not a good idea). After a few passes through the water box many years ago I knew then power braking did nothing but potentially FU the tranny and warp rear rotors

While my left foot controls wheel spin on my car....if doing burnouts with a auto I would, and did when my car was a auto, install a line lock (roll control).

Of course more HP will always help smoke the tires....did for me :)

Double down on the DM braces, they helped my 60' times
 

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Discussion Starter #16
Are the 20's a better hooking/stickier tire?

The old tires were Nitto 555's and the new ones are continental summer only (dont remember the name, ill check later). My understanding is the Nitto's are pretty sticky but i may be wrong. If the continental tires are sticker i dont think it would be by much but maybe 'not much' is enough to make a difference.
 

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Discussion Starter #17
OP

SSandman touches on a good point...your "new" tires very well may have better "traction" than the older tires you had so they likely would not break lose as easily.....and lead to the wheel hop you now have

If your new tires are also taller than your old ones your rear gear ratio got a little shorter mathematically making it harder to break the tires lose....especially if you are power braking to do the burn out (holly F not a good idea). After a few passes through the water box many years ago I knew then power braking did nothing but potentially FU the tranny and warp rear rotors

While my left foot controls wheel spin on my car....if doing burnouts with a auto I would, and did when my car was a auto, install a line lock (roll control).

Of course more HP will always help smoke the tires....did for me :)

Double down on the DM braces, they helped my 60' times
The new tires are taller than the old ones so the gear ration makes sense. I do have a 4.10 gear though so it seems like there should be plenty left even with the taller tire
I have a 6speed so just a little reving and dumping the clutch used to work just fine before the swap.
I looked at the link but i'm not super familiar with what exactly what they do or how they install. i'll have to do some research.... I worked on some old Vette's but that dosent help w/ a solid axle.
 

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Discussion Starter #18

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Yep. Gittem'
 

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The new tires are taller than the old ones so the gear ration makes sense. I do have a 4.10 gear though so it seems like there should be plenty left even with the taller tire
I have a 6speed so just a little reving and dumping the clutch used to work just fine before the swap.
I looked at the link but i'm not super familiar with what exactly what they do or how they install. i'll have to do some research.... I worked on some old Vette's but that dosent help w/ a solid axle.
with a 383/T56 you should be able to boil any tire. Traction and additional rotating mass are greater with your new larger tires but still with a 383 and T56 you should easily spin the tires

I don't need to dump clutch, just floor it in 1st and it boils my stock size tires

The DM braces attach to the forward front bolts of the upper & lower control arm. They help prevent any twisting of the axle housing on launch....something that should greatly improve your situation. Control arms, if stock, flex and also if your control arm bushings are done that can be a contributing factor also

It can be tight getting the DM braces in. I had to un-hook my over axle pipe from hanger to push it out of the way. Also had to back out the upper bolt of control arm to where its end was flush with the control arm, put DM brace up to it, then tighten that bolt to thread through the DM brace (brace is just a hole, not threaded) then put the nut on bolt and tighten. I have Hotchkis upper & lower control arms but the DM braces will work with stock arms if that is what you have
 
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