Tyre pressure - a newbie asks for experts to explain
10-22-2012, 03:25 PM
#31
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10-22-2012, 03:29 PM
#32
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Edward
10-22-2012, 04:08 PM
#33
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No, I don't think that a random N-spec tire is good for a random 911. There were a lot of N-spec tires over the years. Somebody above mentioned the P7s and I remember them well along with P6s. You _really_ wouldn't like them today, I assure you. And they were very much N-rated.
No, I don't believe that 911s ask for anything unique from its tires. My autocross appliance is asking for something unique from the tires and they last about 90 miles (sic). 911 on the street? No, not at all.
I do agree that you believe that any N-spec tire is good for your car. I don;t agree that any N-spec tire is good for your car
More seriously, should you buy a pair of front Contis now that you have rears? I'm far from sure. How much driving have you done on rear Continentals? What's your tire pressures front and rear? Have you tried adjusting it?
You are saying that car feels like it wants to come around on initial turn-in. That would indicate to me a terrible oversteer, to a point of danger. I personally don't believe this to be the case. Let me explain, because this is important in keeping the car in once piece and yourself healthy. I believe that what you are feeling is the softness of rear sidewalls. The rear tires are rolling their shoulders and you feel like the rear is stepping out while in reality it just dives a bit with now lowered rear spring effective rate of the inner corner. The solution for this would be more rear pressure, but, again, in some moderation. If you overdo it you'll get real oversteer and will be quickly visually reminded in every corner where you just came from. Which would be a patently bad thing.
So... let us know what pressure you are running in rear tires. For something like DSW (I will keep my opinions to myself despite all the Tirerack accolades) I would expect that you'll end up close to 40 psi by the time it's all said and done in order to feel anything resembling ... I wanted to say "good handling", but I can't.
And an aside. We all buy 993. Presumably to drive and enjoy them. They are not Accords or Corollas. They deserve very good summer only highest performance tires in order to handle at least as well as intended (better if properly set up due to the fact that tires today are leaps and bounds better than in 1995). And I say this as a daily driver of a 993 in Boston, which means rain, snow and crappy roads. Today there are about 3 tires that suit the 993 best - Toyo R1R, Dunlop Direzza Z1 StarSpec and Hankook RS-3. These, in my opinion, are the best street tires on the market today. I don't have enough knowledge about Michelin Pilot SuperSport, but the regular PS/2s weren't even close to the above three from both first hand and non-first-hand experience.
No, I don't believe that 911s ask for anything unique from its tires. My autocross appliance is asking for something unique from the tires and they last about 90 miles (sic). 911 on the street? No, not at all.
I do agree that you believe that any N-spec tire is good for your car. I don;t agree that any N-spec tire is good for your car
More seriously, should you buy a pair of front Contis now that you have rears? I'm far from sure. How much driving have you done on rear Continentals? What's your tire pressures front and rear? Have you tried adjusting it?
You are saying that car feels like it wants to come around on initial turn-in. That would indicate to me a terrible oversteer, to a point of danger. I personally don't believe this to be the case. Let me explain, because this is important in keeping the car in once piece and yourself healthy. I believe that what you are feeling is the softness of rear sidewalls. The rear tires are rolling their shoulders and you feel like the rear is stepping out while in reality it just dives a bit with now lowered rear spring effective rate of the inner corner. The solution for this would be more rear pressure, but, again, in some moderation. If you overdo it you'll get real oversteer and will be quickly visually reminded in every corner where you just came from. Which would be a patently bad thing.
So... let us know what pressure you are running in rear tires. For something like DSW (I will keep my opinions to myself despite all the Tirerack accolades) I would expect that you'll end up close to 40 psi by the time it's all said and done in order to feel anything resembling ... I wanted to say "good handling", but I can't.
And an aside. We all buy 993. Presumably to drive and enjoy them. They are not Accords or Corollas. They deserve very good summer only highest performance tires in order to handle at least as well as intended (better if properly set up due to the fact that tires today are leaps and bounds better than in 1995). And I say this as a daily driver of a 993 in Boston, which means rain, snow and crappy roads. Today there are about 3 tires that suit the 993 best - Toyo R1R, Dunlop Direzza Z1 StarSpec and Hankook RS-3. These, in my opinion, are the best street tires on the market today. I don't have enough knowledge about Michelin Pilot SuperSport, but the regular PS/2s weren't even close to the above three from both first hand and non-first-hand experience.
As far as pressure, as I mentioned in the post, I have them up to 40 and the car feels better, but not great. They were at 44 initially, but I did not like that. I have installed RS engine mounts since putting the Contis on and it helped a bunch.
I didn't think it was actual oversteer as the car does not feel like it loses grip. It is just a sensation. I agree that the softer side wall is the culprit. The tire guy mentioned how much softer the sidewall was when installing them. This is the first car I've owned where tires have made such an impact on the handling. It is my first true sports car.
I did have an MBZ 6.9. When the XWX's were no longer available from Michelin I installed a Michelin standard passenger tire - do not recall the model and it was very sloppy on handling. I found some Bridgestones with a load rating the same as the XWXs and it made a world of difference. The 6.9 was a heavy car.
So you really think that Contis on the front would help?
I do plan on getting another set of wheels and having a winter and summer set. I do not really need snow tires here in TN. The question is 18s or 17s. The car rides pretty stiff now so I'm afraid that 18s would be too stiff for me.
10-22-2012, 07:19 PM
#34
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Vince, I think that, indeed, because 993 is a sports car you are now suddenly feel what the tire transmits to you much better than you do on a softer and taller sedan, for example. So, yes, tires are much more critical on a more finely tuned car... well, they are the only things between you and the road, literally.
I think the question of buying front DWSs is a grey area. The issue seems, and we agree, to be isolated to soft rear sidewall giving "squeeshy" feel. Buying DWS fronts will not help that except make turn-in less crisp. So, no, I wouldn't spend money on front DWS. As long as you are mindful of different traction and behavior of front and rear tires you'll be fine. 40 psi is about as high as I'd go, agreed. So all sins point to a good set of new tires for new wheels. And I'd strongly suggest 17s. Because the car will be a little less stiff overall (not a bad thing at all) and because both wheels and tires will be a bit cheaper. Plus something like Cup 2 is such a stable commodity now that it can be bought, used and sold a few years later for the same money.
BTW, I made a huge omission above by not mentioning Yoko A008 as one of the best street tire today.
I think the question of buying front DWSs is a grey area. The issue seems, and we agree, to be isolated to soft rear sidewall giving "squeeshy" feel. Buying DWS fronts will not help that except make turn-in less crisp. So, no, I wouldn't spend money on front DWS. As long as you are mindful of different traction and behavior of front and rear tires you'll be fine. 40 psi is about as high as I'd go, agreed. So all sins point to a good set of new tires for new wheels. And I'd strongly suggest 17s. Because the car will be a little less stiff overall (not a bad thing at all) and because both wheels and tires will be a bit cheaper. Plus something like Cup 2 is such a stable commodity now that it can be bought, used and sold a few years later for the same money.
BTW, I made a huge omission above by not mentioning Yoko A008 as one of the best street tire today.
10-22-2012, 07:59 PM
#35
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What does the list recommend for air pressure for 19" wheels? (never mind the never-resolved discussion of are 19's too much wheel for the car).
10-22-2012, 09:06 PM
#36
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Enough with the tit for tat.
...I didn't think it was actual oversteer as the car does not feel like it loses grip. It is just a sensation. I agree that the softer side wall is the culprit. The tire guy mentioned how much softer the sidewall was when installing them. This is the first car I've owned where tires have made such an impact on the handling. It is my first true sports car....
...I didn't think it was actual oversteer as the car does not feel like it loses grip. It is just a sensation. I agree that the softer side wall is the culprit. The tire guy mentioned how much softer the sidewall was when installing them. This is the first car I've owned where tires have made such an impact on the handling. It is my first true sports car....
The "sensation" you write about that you don't like, presuming the tires are inflated within its proper operating range, is exactly from the soft sidewalls of said tire (also presuming that all felt right before the tire swap). That you "fixed" the handling on your 6.9 (cool cars, BTW, I miss seeing those
) with a mere tire swap says much. And yes, a so-called "sports car" is going to be be more sensitive to tire choices because the nature of the car is that it is tuned to "feel" more of the road/driver input. So yeah, a tire choice makes precious little diff in a Camry but will impact your 993's feel considerably. Add to this what others said about 911s and rear-weight bias in general and you have a car that will respond more favorably with a "good" tire; much less favorably with a poor one.
Edward
