Michelin PSCs grip 10% better than S-02s!
12-25-2001, 02:01 AM
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Michelin PSCs grip 10% better than S-02s!
I took the Bridgestone S-02s off my 993 and replaced them with Michelin Pilot Sport Cup tires. I measured the max breaking & cornering of both types of tires under similar conditions and found the Michelins to generate 10+% greater G forces. Here are the details:
- 1997 993 with US M030 and H&R Stage 2 springs (lower & stiffer)
- R265/35 ZR18 F225/40 ZR18 on Factory Tech 8” & 10” wheels 36/44 PSI
- Bridgestones had 0.26” to 0.28” tread depth (2,000 miles on rears)
- Michelins had 0.17” tread depth in center (tested with less than 100 miles use)
- Valentine Research g-analyst 3-axis accelerometer with 1% accuracy
- Tested at 70F ambient, tires warmed a little from street driving
-------------------BRIDGESTONE----MICHELIN
MAX BREAKING-----0.97G----------1.08G From 65 MPH
MAX CORNERING--0.88G-----------0.98G 100’ dia
NOTE: The cornering tests were done by driving in a 100 ft diameter circle on a parking lot which has smooth pebbles in the asphalt. I suspect the pebble asphalt had less grip than the open road where the brake tests were done. So, use the data to compare Breaking to Breaking or Cornering to Cornering. Do not compare Braking to Cornering.
In comparison, I did some tire testing in the late 80s with my 1982 911 SC. The SC had
stock size tires and was stock except it had 7” & 8” x 16” turbo wheels. Switching from
Comp T/As to Yokohama A008Rs improved braking and cornering more than 10%. The
SC could brake or corner at up to 1.0G with the Yokes.
The S-02s have huge rain grooves but I don’t need that in Arizona. The S-02s were very
loud, which I did not like. The Michelins with their small, shallow grooves are very quiet. The S-02s are for sale!
Regards,
George
In sunny Arizona
- 1997 993 with US M030 and H&R Stage 2 springs (lower & stiffer)
- R265/35 ZR18 F225/40 ZR18 on Factory Tech 8” & 10” wheels 36/44 PSI
- Bridgestones had 0.26” to 0.28” tread depth (2,000 miles on rears)
- Michelins had 0.17” tread depth in center (tested with less than 100 miles use)
- Valentine Research g-analyst 3-axis accelerometer with 1% accuracy
- Tested at 70F ambient, tires warmed a little from street driving
-------------------BRIDGESTONE----MICHELIN
MAX BREAKING-----0.97G----------1.08G From 65 MPH
MAX CORNERING--0.88G-----------0.98G 100’ dia
NOTE: The cornering tests were done by driving in a 100 ft diameter circle on a parking lot which has smooth pebbles in the asphalt. I suspect the pebble asphalt had less grip than the open road where the brake tests were done. So, use the data to compare Breaking to Breaking or Cornering to Cornering. Do not compare Braking to Cornering.
In comparison, I did some tire testing in the late 80s with my 1982 911 SC. The SC had
stock size tires and was stock except it had 7” & 8” x 16” turbo wheels. Switching from
Comp T/As to Yokohama A008Rs improved braking and cornering more than 10%. The
SC could brake or corner at up to 1.0G with the Yokes.
The S-02s have huge rain grooves but I don’t need that in Arizona. The S-02s were very
loud, which I did not like. The Michelins with their small, shallow grooves are very quiet. The S-02s are for sale!
Regards,
George
In sunny Arizona
12-25-2001, 02:28 PM
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George,
Just for interest, were the Bridgestones and Michelins in the same condition (ie, same amount of miles on them)?
I have zero knowledge of tires, but was wondering if the Bridgestones were worn and the Michelins were new if that wouldn't account for some of the differences seen. Anyone with more tire knowledge care to comment?
Just for interest, were the Bridgestones and Michelins in the same condition (ie, same amount of miles on them)?
I have zero knowledge of tires, but was wondering if the Bridgestones were worn and the Michelins were new if that wouldn't account for some of the differences seen. Anyone with more tire knowledge care to comment?
12-25-2001, 02:40 PM
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Interesting data, but there are a couple of problems with the tests.
36/44 is way too high for maximum grip with either tire, so you are not really testing the tire capability.
Both tires improve grip with temp, but especially the cups, as those are R-compound. If you did not adequately heat the tires, the comparison is rather meaningless.
Perhaps the skidpad diameter is too small for best results, but the cup tires should be able to generate ~1.2 g's and the SO-2's around 1.0g. I would be interested to see what you get with the cups if you really heat them and use a cold pressure of 30/32.
36/44 is way too high for maximum grip with either tire, so you are not really testing the tire capability.
Both tires improve grip with temp, but especially the cups, as those are R-compound. If you did not adequately heat the tires, the comparison is rather meaningless.
Perhaps the skidpad diameter is too small for best results, but the cup tires should be able to generate ~1.2 g's and the SO-2's around 1.0g. I would be interested to see what you get with the cups if you really heat them and use a cold pressure of 30/32.
12-25-2001, 03:40 PM
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Originally posted by Jeff96-993:
<STRONG>I have zero knowledge of tires, but was wondering if the Bridgestones were worn and the Michelins were new if that wouldn't account for some of the differences seen.</STRONG>
<STRONG>I have zero knowledge of tires, but was wondering if the Bridgestones were worn and the Michelins were new if that wouldn't account for some of the differences seen.</STRONG>
Assuming dry conditions, the reverse is generally true, i.e., deeper tread/less wear = less tire contact area & more tread squirm, resulting in reduced adhesion & control. That's why slicks are used for dry racing.
OTOH, add water & the equation is reversed requiring a combination of tread pattern, tread depth, rain sipes, etc. for improved adhesion.
Makes designing a street tire that will excel in both wet and dry conditions challenging, even without adding in optimal temperature ranges, ride comfort, low noise, durability, tread life, etc.
George
Thanks for sharing your results. Regardless of several unadjusted test variables, the results are pretty interesting (at least to me) and the performance differentials are surprisingly large. I'm no engineer, but I think the increased deceleration would translate into a significantly shorter stop.
12-26-2001, 02:06 AM
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Jeff96-993,
The Bridgestone S-02s had about 2000 miles on the rears and more than 4000 miles on
the fronts.
The Michelin Pilot Sport Cups had about 100 street miles on them at time of testing. I
would expect the Michelins to grip better as I put more miles on them.
Regards,
George
In sunny Arizona
The Bridgestone S-02s had about 2000 miles on the rears and more than 4000 miles on
the fronts.
The Michelin Pilot Sport Cups had about 100 street miles on them at time of testing. I
would expect the Michelins to grip better as I put more miles on them.
Regards,
George
In sunny Arizona
12-26-2001, 02:33 AM
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Mark D - 993TT CA ,
Thanks for your comments.
1) “36/44 is way too high for maximum grip with either tire”
I was running stock tire pressure. I have not done pressure evaluation yet. My first autocross in the 993 is coming up on 13 JAN and I would like to be optimized by then.
Have you found 30/32 PSI to be optimum for this wheel tire combination?
2) “If you did not adequately heat the tires, the comparison is rather meaningless”
You are right. I will be running the g-analyst as I drive the car in autocross & DE to measure the effect of temperature on grip. However, I am skeptical that the S-02s will out perform the Michelins when hot so I will run with the Michelins.
3) “cup tires should be able to generate ~1.2 g's and the SO-2's around 1.0g” on skidpad
The lot I used for a skidpad (Northeast parking at Westworld, for those in the Phoenix area) has a lot of smooth pebbles in the surface so the grip was surely compromised.
WOW, I will be thrilled with 1.2Gs with the Michelins in competitive events!
Regards,
George
In sunny Arizona
Thanks for your comments.
1) “36/44 is way too high for maximum grip with either tire”
I was running stock tire pressure. I have not done pressure evaluation yet. My first autocross in the 993 is coming up on 13 JAN and I would like to be optimized by then.
Have you found 30/32 PSI to be optimum for this wheel tire combination?
2) “If you did not adequately heat the tires, the comparison is rather meaningless”
You are right. I will be running the g-analyst as I drive the car in autocross & DE to measure the effect of temperature on grip. However, I am skeptical that the S-02s will out perform the Michelins when hot so I will run with the Michelins.
3) “cup tires should be able to generate ~1.2 g's and the SO-2's around 1.0g” on skidpad
The lot I used for a skidpad (Northeast parking at Westworld, for those in the Phoenix area) has a lot of smooth pebbles in the surface so the grip was surely compromised.
WOW, I will be thrilled with 1.2Gs with the Michelins in competitive events!
Regards,
George
In sunny Arizona
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12-26-2001, 12:35 PM
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Originally posted by George Helser:
<STRONG>Mark D - 993TT CA ,
Thanks for your comments.
1) “36/44 is way too high for maximum grip with either tire”
I was running stock tire pressure. I have not done pressure evaluation yet. My first autocross in the 993 is coming up on 13 JAN and I would like to be optimized by then.
Have you found 30/32 PSI to be optimum for this wheel tire combination?
I have found this to be a good starting point for most tires on the 993 for track events. At an autocross, you will not get the tires as hot, so I suspect a couple more lbs at each end will be better. I don't autocross, so perhaps someone else can chime in here.
2) “If you did not adequately heat the tires, the comparison is rather meaningless”
You are right. I will be running the g-analyst as I drive the car in autocross & DE to measure the effect of temperature on grip. However, I am skeptical that the S-02s will out perform the Michelins when hot so I will run with the Michelins.
I agree. They Michelins are an R compound, if I have this right. They will far outperform the SO-2s. My comments about temp are really that the Michelins will gain alot of grip as they heat. The SO-2's will gain a little bit.
3) “cup tires should be able to generate ~1.2 g's and the SO-2's around 1.0g” on skidpad
The lot I used for a skidpad (Northeast parking at Westworld, for those in the Phoenix area) has a lot of smooth pebbles in the surface so the grip was surely compromised.
WOW, I will be thrilled with 1.2Gs with the Michelins in competitive events!
I think the challenge in autocross is to keep R-compound tires hot enough so that you get best grip for your timed runs. Good Luck
</STRONG>
<STRONG>Mark D - 993TT CA ,
Thanks for your comments.
1) “36/44 is way too high for maximum grip with either tire”
I was running stock tire pressure. I have not done pressure evaluation yet. My first autocross in the 993 is coming up on 13 JAN and I would like to be optimized by then.
Have you found 30/32 PSI to be optimum for this wheel tire combination?
I have found this to be a good starting point for most tires on the 993 for track events. At an autocross, you will not get the tires as hot, so I suspect a couple more lbs at each end will be better. I don't autocross, so perhaps someone else can chime in here.
2) “If you did not adequately heat the tires, the comparison is rather meaningless”
You are right. I will be running the g-analyst as I drive the car in autocross & DE to measure the effect of temperature on grip. However, I am skeptical that the S-02s will out perform the Michelins when hot so I will run with the Michelins.
I agree. They Michelins are an R compound, if I have this right. They will far outperform the SO-2s. My comments about temp are really that the Michelins will gain alot of grip as they heat. The SO-2's will gain a little bit.
3) “cup tires should be able to generate ~1.2 g's and the SO-2's around 1.0g” on skidpad
The lot I used for a skidpad (Northeast parking at Westworld, for those in the Phoenix area) has a lot of smooth pebbles in the surface so the grip was surely compromised.
WOW, I will be thrilled with 1.2Gs with the Michelins in competitive events!
I think the challenge in autocross is to keep R-compound tires hot enough so that you get best grip for your timed runs. Good Luck
</STRONG>