THE Tire Thread

shesgotlegs said:

30 front and 28 rear.

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Thanks. Just wanted to ensure Canadian lbs weren't inflated like the currency. :wink

SYCO GT said:

Thanks Torrie and shesgotlegs for the info. I kept thinking, WTH is going on...

I do recall the Goodyears feeling really hard in comparison.

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Glad I could help. :thumbsup

Terry

AlohaGT said:

Thanks. Just wanted to ensure Canadian lbs weren't inflated like the currency. :wink

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Naw... it was only our gallon. :lol

Bony, earlier in the week I made a boo boo. Could you deduct one vote from after market wheels/tires and add one vote to OEM wheels - after market tires?

done

B O N Y said:

done

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Thank you, my friend.

Pirelli PZero Corsa System
F 235/40-18
R 345/35/19

Comparable to Hoosier R6's on track, way superior to Goodyears.
Better than Hoosiers and Goodyears on street.
Rears are bordering on too wide for wheel but ok with higher pressures. Dont drop them below 29.

Hoosier R6 as track tires with completely dry and warm conditions.

Goodyears as track tires with anything less than dry conditions and as daily street tires.

20,000 plus miles and counting.

Pete S.

Goodyears on the track:

tire change

Just put the Bridgestones on but instead of the 265 in front I opted to go 1 size smaller to 255/40 18. Read the posts regarding the lack of "nimbleness" after going with the 265 tire on the front. Pleased to announce that the car still feels light and nimble but "planted" all the time.Only drawback is the 255 is a W rated tire.

To add to Fubar's very informative post: In our quest for the best alternatives to Goodyears and something with more grooves than the Hoosiers, wanted to post some data on the current tire selections and get some ideas about how this would theoretically (or realistically) affect handling:

Used the following link to obtain this data:
http://www.net-comber.com/tirecalc.html

Front , Dia. (in) , Rear , Dia. (in)

Goodyear 235/45/ZR18 , 26.327 , 315/40/ZR19 , 28.921

Hoosier R6 245/40/ZR18 , 25.717 , 315/40/ZR19 , 28.921
Ground clearance of front -0.305 inches. Rear unchanged.
Actual speed of front tire when speedometer reads 65 mph is 63.493.
Rear tire is unchanged.

Bridgestone 265/40/ZR18 , 26.346 , 345/35/ZR19 , 28.508
Potenza RE050A Scuderia (rear)
Ground clearance of front end +0.01 inches and rear by -0.207 inches.
Actual speed of front when speedometer reads 65 mph is 65.049.
Actual speed of rear when speedometer reads 65 mph is 64.071.

Pirelli Zero 245/35/ZR18 , 24.752 , 345/35/ZR19 , 28.508
Corsa System
Ground clearance of front end -0.787 inches and rear -0.207 inches.
Actual speed of front when speedometer reads 65 mph is 61.112.
Actual speed of rear when speedometer reads 65 mph is 64.071.

Pirelli Zero Corsa system also comes in a 235/40/ZR18 tire, 25.402 dia., which changes ground clearance in front -0.463 inches. Also speed of front when speedometer reads 65 mph is 62.716.

Michelin Pilot 245/40/ZR18 , 25.717 , 345/30/ZR19 , 27.150
Sport PS2
Ground clearance of front -0.305 inches but rear ground clearance -0.886 inches.
Actual speed of front tire when speedometer reads 65 mph is 63.493.
Actual speed of rear tire when speedometer reads 65 mph is 61.018

Now here are my questions:
1) More desirable to have the front end slightly lower than the rear? If this is the case the Hoosiers and Pirellis would be most desirable. The Bridgestones and especially the Michelins appear to raise the front end of the car. I assume this is why Stillen had to adjust their Penske's...but for those of us who do not have Penske's????
2) Speed sensors located in all 4 tires? rear vs. front?
3) Any problems with these combinations and our ABS system? previous posts seem to mention this as a potential problem.
4) Dave, any high speed runs on tires other than Goodyears or Hoosiers? If so, was the ride height adjusted?

This is probably extreme overkill but I think most of us are still wrestling with this issue.

The Pirelli Corsa Systems were a slight improvement over the Goodyears, but disappointing traction/handling wise versus my new HRE/Michelin PS2 combo. I would honestly not recommend the Pirelli setup on OEM wheels.

Review for Michelin PS2's: Used during 2008 New Zealand Targa Rally

First off let me start by saying that I am not a distributor for Michelin so the following review will be completely unbiased. I just want to tell everyone about our experiences with the PS2's on the rally and explain what we think of them.

To put it simply, we were VERY impressed with these tires. When we initially received the tires we were a little bit concerned that they might not have as much grip as we would like. They appear to have a lot of tread and they aren't what I would normally refer to as a soft compound. We were trying to decide whether we should go with the Michelin PS2's or the Sport Cup's. Michelin Sport Cup's are the same tires used on the new Viper ACR's and Steve had some experiences with them when testing the ACR for Road and Track. We would love to have used the Sport Cup's but our concern was that they would be too soft and not hold up for the entire week. So, we decided to stick with the PS2's.

After every stage we would inspect the tires to make sure they were holding up well and check to see if there were any issues arising. Every time we checked the rubber we found that it became very soft after it was warm. However, it didn't appear to be wearing out very quickly. We ended up having a half day in the rain and the wet weather performance was fantastic. The more time we spent on the tires the more confidence we gained in their performance. Unlike the factory Goodyear's the tires didn't get warm and greasy. They got warm and grippy! It was perfect!

On the last day we decided to change the rear tires. The ONLY reason for this was becuase it began to rain extremely hard and Steve just didn't want to take any unnecessary risks. We decided to put on some new rear tires to make sure that we had as much rear grip as possible. The last day of competition saw hurricane force winds and terrential downpours. Part of the rally was held on the peninsula around Wellington. The final stage of the rally was canceled due to ocean waves splashing on to the roads of the stage. Even in these conditions Steve felt confident in the car and pushed her hard. In some stages he was able to pass up to 5 or 6 cars. He has said many times that the only reason for this was because of his confidence in the tires.

Again, we don't sell Michelin tires so this isn't a sales pitch. Just our experience with them. I hope this is helpful.

kmillen said:

Review for Michelin PS2's: Used during 2008 New Zealand Targa Rally

First off let me start by saying that I am not a distributor for Michelin so the following review will be completely unbiased. I just want to tell everyone about our experiences with the PS2's on the rally and explain what we think of them.

To put it simply, we were VERY impressed with these tires. When we initially received the tires we were a little bit concerned that they might not have as much grip as we would like. They appear to have a lot of tread and they aren't what I would normally refer to as a soft compound. We were trying to decide whether we should go with the Michelin PS2's or the Sport Cup's. Michelin Sport Cup's are the same tires used on the new Viper ACR's and Steve had some experiences with them when testing the ACR for Road and Track. We would love to have used the Sport Cup's but our concern was that they would be too soft and not hold up for the entire week. So, we decided to stick with the PS2's.

After every stage we would inspect the tires to make sure they were holding up well and check to see if there were any issues arising. Every time we checked the rubber we found that it became very soft after it was warm. However, it didn't appear to be wearing out very quickly. We ended up having a half day in the rain and the wet weather performance was fantastic. The more time we spent on the tires the more confidence we gained in their performance. Unlike the factory Goodyear's the tires didn't get warm and greasy. They got warm and grippy! It was perfect!

On the last day we decided to change the rear tires. The ONLY reason for this was becuase it began to rain extremely hard and Steve just didn't want to take any unnecessary risks. We decided to put on some new rear tires to make sure that we had as much rear grip as possible. The last day of competition saw hurricane force winds and terrential downpours. Part of the rally was held on the peninsula around Wellington. The final stage of the rally was canceled due to ocean waves splashing on to the roads of the stage. Even in these conditions Steve felt confident in the car and pushed her hard. In some stages he was able to pass up to 5 or 6 cars. He has said many times that the only reason for this was because of his confidence in the tires.

Again, we don't sell Michelin tires so this isn't a sales pitch. Just our experience with them. I hope this is helpful.

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Kyle great feedback. Certainly lines up with my own limited time so far with the PS2 on my new rims. The compound does seem to belie the grip levels achieved.

I'm pleased with the PS2's that I have mounted and will replace them with the same tire.

kmillen said:

Review for Michelin PS2's: Used during 2008 New Zealand Targa Rally

First off let me start by saying that I am not a distributor for Michelin so the following review will be completely unbiased. I just want to tell everyone about our experiences with the PS2's on the rally and explain what we think of them.

To put it simply, we were VERY impressed with these tires. When we initially received the tires we were a little bit concerned that they might not have as much grip as we would like. They appear to have a lot of tread and they aren't what I would normally refer to as a soft compound. We were trying to decide whether we should go with the Michelin PS2's or the Sport Cup's. Michelin Sport Cup's are the same tires used on the new Viper ACR's and Steve had some experiences with them when testing the ACR for Road and Track. We would love to have used the Sport Cup's but our concern was that they would be too soft and not hold up for the entire week. So, we decided to stick with the PS2's.

After every stage we would inspect the tires to make sure they were holding up well and check to see if there were any issues arising. Every time we checked the rubber we found that it became very soft after it was warm. However, it didn't appear to be wearing out very quickly. We ended up having a half day in the rain and the wet weather performance was fantastic. The more time we spent on the tires the more confidence we gained in their performance. Unlike the factory Goodyear's the tires didn't get warm and greasy. They got warm and grippy! It was perfect!

On the last day we decided to change the rear tires. The ONLY reason for this was becuase it began to rain extremely hard and Steve just didn't want to take any unnecessary risks. We decided to put on some new rear tires to make sure that we had as much rear grip as possible. The last day of competition saw hurricane force winds and terrential downpours. Part of the rally was held on the peninsula around Wellington. The final stage of the rally was canceled due to ocean waves splashing on to the roads of the stage. Even in these conditions Steve felt confident in the car and pushed her hard. In some stages he was able to pass up to 5 or 6 cars. He has said many times that the only reason for this was because of his confidence in the tires.

Again, we don't sell Michelin tires so this isn't a sales pitch. Just our experience with them. I hope this is helpful.

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Kyle,
Could you comment more specifically on what you altered on the suspension to accomodate the PS2s, such as ride height front and back, etc.?? My feeling, based on my posted information of tire dia, is that the PS2's on a stock GT without suspension and ride height adjustments would not be optimal, at least compared to the Goodyears.
Thanks,
Scott

Cyclenirvana said:

Kyle,
Could you comment more specifically on what you altered on the suspension to accomodate the PS2s, such as ride height front and back, etc.?? My feeling, based on my posted information of tire dia, is that the PS2's on a stock GT without suspension and ride height adjustments would not be optimal, at least compared to the Goodyears.
Thanks,
Scott

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Scott,

There were a couple of adjustments that we made to our suspension due to the Michelin's. Obviously the first thought is going to be "how do they fill the wheel well." Simply said, they don't. Our car is equipped with the Penske adjustable coil-overs. To be perfectly honest, I do not know exactly how much we have lowered our car compared to stock. I want to say we are about a half inch shorter than factory ride height based off of the shock settings (not including tire circumference differences.) One thing to keep in mind is that we use our car in somewhat rough conditions and therefore we keep her a little bit higher off the ground than the average owner would. Although, we are still lower than stock ride height.

When we initially tested the tires at the Fontana Speedway interior road course we found that the car was a little bit unstable. So, we dropped her about 1/4 inch in the rear (which in turn gave her a little more toe out in the rear as well) and the car became much more stable and really turned through the corners alot better.

Depending on what you are doing with your car I think that most owner's will find that the wheel gap will become unacceptable with the factory suspension and Michelin PS2's in their current size offerings. I think that a set of Penske's or T&A shock sleeves will become a necessity. With that being said, I think that the Michelin tires are well worth the look and consideration. I promise you, you will not be disappointed.

kmillen said:

Scott,

There were a couple of adjustments that we made to our suspension due to the Michelin's. Obviously the first thought is going to be "how do they fill the wheel well." Simply said, they don't. Our car is equipped with the Penske adjustable coil-overs. To be perfectly honest, I do not know exactly how much we have lowered our car compared to stock. I want to say we are about a half inch shorter than factory ride height based off of the shock settings (not including tire circumference differences.) One thing to keep in mind is that we use our car in somewhat rough conditions and therefore we keep her a little bit higher off the ground than the average owner would. Although, we are still lower than stock ride height.

When we initially tested the tires at the Fontana Speedway interior road course we found that the car was a little bit unstable. So, we dropped her about 1/4 inch in the rear (which in turn gave her a little more toe out in the rear as well) and the car became much more stable and really turned through the corners alot better.

Depending on what you are doing with your car I think that most owner's will find that the wheel gap will become unacceptable with the factory suspension and Michelin PS2's in their current size offerings. I think that a set of Penske's or T&A shock sleeves will become a necessity. With that being said, I think that the Michelin tires are well worth the look and consideration. I promise you, you will not be disappointed.

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Thanks Kyle. It helps to have someone posting real life experiences on the road and track in all conditions but still wanting optimal performance. I figured given the ride height of the Michelin PS2s being much shorter than the Goodyears that lowering the car was a must. Based on what you have said regarding ride height, does the rear of your car sit slightly lower than the front? Having the Michelins front and back would produce a slightly rear bias...but you further lowered the car 1/4 inch in the rear? How does this rear bias affect high speed runs? cornering?
I had always thought the following summarized at this link http://www1.epinions.com/auto-review-30A2-31E8432-3A231082-prod1: "Rake is the angle between the car and the road. If the car is level with the ground you have zero rake. If the front is lower than the back, you have positive rake. If the back is lower than the front you have negative rake. Positive rake is what we want here. What happens is the air goes under the front of the car and is in a set amount of space. With positive rake, the space between car and ground gets larger as you travel toward the back of the car. This has the effect of reducing the pressure of the air beneath the car by trying to pull the individual molecules further apart than they already are". Now, honestly, I am not sure how our rear diffuser affects the above. However, it is clear that some of our tire choices, namely the Bridgestones and Michelins would produce negative rake, at least compared to stock Goodyears.

Sorry for all of the questions?:ack

Kirby has a set of the PS2's. What's your feeling Kirby? Have you done any suspension mods with the Michelins?

shesgotlegs said:

I love the Bridgestones for the street (as I have had no track experience with them) and agree with HHGT, Heritage Bruce and Fubar in their reports of better traction and being alot quieter than the Goodyears. I do want to add though that the car also now feels alot "softer" - that is I didn't realize how much the Goodyears vibrated and or felt harsh through the steering wheel, seat of the pants and through the floor boards. For the record I am running 30 Canadian lbs. up front and 28 American lbs.:wink out back as per Alex of T&A's suggestion.

I however did also experience what Fubar is saying regarding no longer feeling as comfortable driving with two fingers as the vehicle, for me, no longer feels as planted or wanting to stay dead centre especially in the ruts. That being said I had a discussion at the rally with Alex of T&A who didn't seem surprised and felt it was just a matter of adjusting the car's toe in about 1/16 of an inch since the Bridgestones are alot softer than the Goodyears.

I have yet to have this done but will report after I do so.

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Well, I had the toe in done to 1/16 of an inch which gave it the on center feel it was lacking however also now find the car too twichey / nervous. Something I also just noticed and may have a bearing is that the rear tires have too much negative camber as the outside 1" of each tire fails to make contact with the road.

Our thoughts are to dial in more positive camber in the rear so that the tire's contact patch is balanced as well as re-adjust the front toe in to 1/32 of an inch over stock.

Keep you posted.