Lack of traction

[ftc~brz]

^this…it's why I bought a winter beater. summer car with similar #s. At 334whp I was putting 261tq (90 degrees ambient) Summer tires not so nice in winter temps.

[Figo]

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Trade your turbo for my CAI and you will solve the problem easily.

my loss your gain.



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[ZDan]

Originally Posted by SpeedR

300hp + 55 mph + 255/40/18 PSS and "the back end just starts spinning" dose not add up!

Actually, it does add up, particularly if it's 300rwhp.

300rwhp at 55mph (80.7 ft/s) gives 2045 lb. of thrust at the rear tire contact patches.
300hp * 550 ft-lb/s/hp /80.7 ft/s = 2045 lb.

If all that made it to the ground, ~0.7g acceleration (2045/2950 = 0.7). At that acceleration, weight transfer is ~12% (0.7*18" c.g. height/101" wheelbase =.12) , load distribution ~42F/58R, load on rear tires ~1714 lb. Effective coefficient of friction at the tire/ground interface would have to be 2045/1714 = 1.19 to put that down. It's not surprising that even very good tires are overwhelmed.

[Mathewgzlz]

Originally Posted by ZDan

Actually, it does add up, particularly if it's 300rwhp.



300rwhp at 55mph (80.7 ft/s) gives 2045 lb. of thrust at the rear tire contact patches.

300hp * 550 ft-lb/s/hp /80.7 ft/s = 2045 lb.



If all that made it to the ground, ~0.7g acceleration (2045/2950 = 0.7). At that acceleration, weight transfer is ~12% (0.7*18" c.g. height/101" wheelbase =.12) , load distribution ~42F/58R, load on rear tires ~1714 lb. Effective coefficient of friction at the tire/ground interface would have to be 2045/1714 = 1.19 to put that down. It's not surprising that even very good tires are overwhelmed.

Batman did you do tht in your head or did Alfred lol


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[OjiGeorge]

Throw a few sandbags in the trunk

[Mathewgzlz]

Originally Posted by OjiGeorge

Throw a few sandbags in the trunk

I might actually do tht


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[SKELLINGTON]

[wparsons]

Originally Posted by ZDan

Actually, it does add up, particularly if it's 300rwhp.

300rwhp at 55mph (80.7 ft/s) gives 2045 lb. of thrust at the rear tire contact patches.
300hp * 550 ft-lb/s/hp /80.7 ft/s = 2045 lb.

If all that made it to the ground, ~0.7g acceleration (2045/2950 = 0.7). At that acceleration, weight transfer is ~12% (0.7*18" c.g. height/101" wheelbase =.12) , load distribution ~42F/58R, load on rear tires ~1714 lb. Effective coefficient of friction at the tire/ground interface would have to be 2045/1714 = 1.19 to put that down. It's not surprising that even very good tires are overwhelmed.

How are you able to calculate ANY of that without seeing his dyno chart and knowing what gear he was in at 55mph???

To actually calculate how much power is making it to the tires you need to know what gear it was in and how much power it makes at that RPM. Knowing peak hp means nothing if it peaks at 6500rpm and he was driving at 3500rpm.

I think most people were assuming he wasn't driving around at 55mph in 2nd gear, but probably 5th or 6th which would put it low in the rev range and nowhere near 300whp.

[ZDan]

Surely no one is assuming he's getting wheelspin at 55mph in 5th or 6th gear! If he's making 300rwhp at 55mph, most likely he has to be in 2nd gear. To make that much power at that speed in 5th gear would require about 570 lb-ft of torque.

[Moto-P]

Stickier tires can also cure traction issues, as well as suspension tuning for softer rear rates that allow the car to squat a bit more for drag racing use...

Tires do make a HUGE difference and while going wider will allow for some increase by making the contact patch larger, it also has to maintain correct contact patch temperature, and bigger tires on a light car also has inherent issue of taking much longer to heat up.

Going to a more aggressive tire compound will make a much more drastic difference...than small difference in size in the case of traction, cornering and braking.

[bucko3the7man]

I'm betting temperature has something to do with it. Pss are summer tires, don't do well in cooler conditions

[ZDan]

Agree, temp is probably a big factor. PSS are great tires, but at ambient temps below about 50F, they don't have a lot of grip on the street, don't get near optimal operating temp.

[charged86]

Originally Posted by bucko3the7man

I'm betting temperature has something to do with it. Pss are summer tires, don't do well in cooler conditions

Originally Posted by ZDan

Agree, temp is probably a big factor. PSS are great tires, but at ambient temps below about 50F, they don't have a lot of grip on the street, don't get near optimal operating temp.

This is true i have the same tire in a michilen super sport 245/40-17 65mph punch in 3rd gear car gets side ways forget about first and 2nd under boost.

and once (no one is gonna believe it).....but on a chilly afternoon with the sun out on the salt covered highway that was BONE DRY after I ran a V8 challenger, got completely sideways in 3rd and when i hit full boost in 4th the tires loss traction at 90mph.

i was at 375whp and 262 trq

[wparsons]

Originally Posted by ZDan

Surely no one is assuming he's getting wheelspin at 55mph in 5th or 6th gear! If he's making 300rwhp at 55mph, most likely he has to be in 2nd gear. To make that much power at that speed in 5th gear would require about 570 lb-ft of torque.

Where does he say he's making 300whp at 55mph?

OP, what gear are you when this is happening?