Tires slipping / rotating on Rim
#1
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My rear tires slipped/rotated on rims at the last event.
15x9 6UL (Gen 3), 205/50/15 Toyo RRs, 26 cold\30 hot.
NB N/A (TTE) Miata, Torsen II, light weight flywheel.
I started marking my valve stem positions with my latest set of RRs and found the right rear tire had slipped about 6" on the rim and the left rear about 4" in 4 15 minute sessions. Fronts didn't appear to move on the rim.
The track was MSR-Cresson with one longer tight left 2nd gear accelerating corner and one shorter left 2nd gear accelerating corner. Right corners are all under deceleration or 3rd gear.
Do I need to re-balance the tires?
Do I need to change where I get my tires mounted? Could they be using too much liquid during the install?
Or do I just need to ignore it and drive the car?
15x9 6UL (Gen 3), 205/50/15 Toyo RRs, 26 cold\30 hot.
NB N/A (TTE) Miata, Torsen II, light weight flywheel.
I started marking my valve stem positions with my latest set of RRs and found the right rear tire had slipped about 6" on the rim and the left rear about 4" in 4 15 minute sessions. Fronts didn't appear to move on the rim.
The track was MSR-Cresson with one longer tight left 2nd gear accelerating corner and one shorter left 2nd gear accelerating corner. Right corners are all under deceleration or 3rd gear.
Do I need to re-balance the tires?
Do I need to change where I get my tires mounted? Could they be using too much liquid during the install?
Or do I just need to ignore it and drive the car?
#5
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If make marks like that on pretty much any track car that doesn't have a knurled area where the bead seats, you'll notice they slip.
Ignore it.
This is also the reason I will balance my wheels without a tire on it, and just slap race tires on and off without issues. (Sometimes the bare wheel will take 1, maybe two weights at the most. Most don't require any at all.)
Ignore it.
This is also the reason I will balance my wheels without a tire on it, and just slap race tires on and off without issues. (Sometimes the bare wheel will take 1, maybe two weights at the most. Most don't require any at all.)
#8
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Running 205's on a 9 inch wheel is a hefty tire stretch. Cornering forces may actually be pulling the tire bead off the rim, only to reseat themselves on a straight section of road. With this amount of stretch, you would need more than 26 psi cold / 30 psi hot to keep the tires seated on the wheels. Go to a narrower wheel size and your troubles should disappear. Or go to 245's for tires.
#9
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Running 205's on a 9 inch wheel is a hefty tire stretch. Cornering forces may actually be pulling the tire bead off the rim, only to reseat themselves on a straight section of road. With this amount of stretch, you would need more than 26 psi cold / 30 psi hot to keep the tires seated on the wheels. Go to a narrower wheel size and your troubles should disappear. Or go to 245's for tires.
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Last edited by emilio700; 05-25-2016 at 03:01 AM.
#10
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Running 205's on a 9 inch wheel is a hefty tire stretch. Cornering forces may actually be pulling the tire bead off the rim, only to reseat themselves on a straight section of road. With this amount of stretch, you would need more than 26 psi cold / 30 psi hot to keep the tires seated on the wheels. Go to a narrower wheel size and your troubles should disappear. Or go to 245's for tires.
#11
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Running 205's on a 9 inch wheel is a hefty tire stretch. Cornering forces may actually be pulling the tire bead off the rim, only to reseat themselves on a straight section of road. With this amount of stretch, you would need more than 26 psi cold / 30 psi hot to keep the tires seated on the wheels. Go to a narrower wheel size and your troubles should disappear. Or go to 245's for tires.
#12
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OK, so I didn't get universal buy-in to my explanation. Could someone please answer why the OP's setup, 205/50-15 tires on a 15x9 wheel is the hot setup for an autocross car? I would have thought the wheel width could be less just to remove weight and keep the tire close to its original dimensions. Typically, people don't recommend more than 7.5 inch width for a 205 section. Does a larger rim width translate into extra responsiveness? If so, does it make a difference to lap times? Perhaps he has the wrong bead sealing glop in the wheel with the wheel spinout he is getting. Or perhaps this is a effect of the Torsen he is using. Decades ago, drag racers used to screw the tires to the rims - not universally accepted but at least the tire didn't rotate on the wheel and this was with the low pressures (under 15 psi) that were used at the time.
BTW the last autocross I attended as a spectator was won by the lowest powered car with the smallest tires - a Lotus Elan running stock wheels and tire sizes. This was not a close win either - he did 47.+ seconds and the nearest car was at 51.+ seconds.
BTW the last autocross I attended as a spectator was won by the lowest powered car with the smallest tires - a Lotus Elan running stock wheels and tire sizes. This was not a close win either - he did 47.+ seconds and the nearest car was at 51.+ seconds.
#14
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If a rear tire debeaded mid corner, the only outcome I can think of is the tire immediately deflating and the car spinning.
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Does a larger rim width translate into extra responsiveness?
If so, does it make a difference to lap times?
#17
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OK, so I didn't get universal buy-in to my explanation. Could someone please answer why the OP's setup, 205/50-15 tires on a 15x9 wheel is the hot setup for an autocross car? I would have thought the wheel width could be less just to remove weight and keep the tire close to its original dimensions. Typically, people don't recommend more than 7.5 inch width for a 205 section. Does a larger rim width translate into extra responsiveness? If so, does it make a difference to lap times? Perhaps he has the wrong bead sealing glop in the wheel with the wheel spinout he is getting. Or perhaps this is a effect of the Torsen he is using. Decades ago, drag racers used to screw the tires to the rims - not universally accepted but at least the tire didn't rotate on the wheel and this was with the low pressures (under 15 psi) that were used at the time.
BTW the last autocross I attended as a spectator was won by the lowest powered car with the smallest tires - a Lotus Elan running stock wheels and tire sizes. This was not a close win either - he did 47.+ seconds and the nearest car was at 51.+ seconds.
BTW the last autocross I attended as a spectator was won by the lowest powered car with the smallest tires - a Lotus Elan running stock wheels and tire sizes. This was not a close win either - he did 47.+ seconds and the nearest car was at 51.+ seconds.
Also, how does a Torsen work?
And a 3rd request: what tires are readily available 245 in 15"?
Thanks.
#18
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^
The OP did not bring up autocross, but autocross does have some of the same handling issues as racing with tighter turns.
Here is the explanation of a Torsen in a video:
Although it does ensure traction from both wheels in a straight line, its tendency to lock wheels together may make for interesting behaviour in turns with some tendency for the rear end to get loose.
Hoosier apparently has A7 and R7 tires in 245/40-15 third and fourth entries down on this page:
245 15 at Tire Rack
Not cheap and not for the street but listed as available.
The OP did not bring up autocross, but autocross does have some of the same handling issues as racing with tighter turns.
Here is the explanation of a Torsen in a video:
Although it does ensure traction from both wheels in a straight line, its tendency to lock wheels together may make for interesting behaviour in turns with some tendency for the rear end to get loose.
Hoosier apparently has A7 and R7 tires in 245/40-15 third and fourth entries down on this page:
245 15 at Tire Rack
Not cheap and not for the street but listed as available.
#19
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https://www.miataturbo.net/wheels-ti...40-15-a-86511/
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