PaulQ Posted October 22, 2020 Report Share Posted October 22, 2020 Was the 235 fitted to the 987 only on the 2.7 or did this include the 3.2S as well. ? I wonder why the front/rear stagger is bigger on the 986 running summer 17's Link to comment Share on other sites More sharing options...
edc Posted October 22, 2020 Report Share Posted October 22, 2020 17 minutes ago, PaulQ said: Was the 235 fitted to the 987 only on the 2.7 or did this include the 3.2S as well. ? I wonder why the front/rear stagger is bigger on the 986 running summer 17's Probably as much to do with preferred supplier N rated tyre availability. Link to comment Share on other sites More sharing options...
gIzzE Posted October 22, 2020 Author Report Share Posted October 22, 2020 24 minutes ago, PaulQ said: Was the 235 fitted to the 987 only on the 2.7 or did this include the 3.2S as well. ? I wonder why the front/rear stagger is bigger on the 986 running summer 17's Probably more to do with the fact 987 S always came on 18" wheels, so the 17" wheels were only ever sold as a winter set. So why bother to get approval for 17" wheel sizes? How many would want to 'upgrade' to a 17"? Link to comment Share on other sites More sharing options...
the baron Posted October 23, 2020 Report Share Posted October 23, 2020 16 hours ago, ½cwt said: Also bear in mind the earlier cars have no tc.... Some do, my 1997 2.5 has TC from factory, I know cos I ordered it. Link to comment Share on other sites More sharing options...
½cwt Posted October 23, 2020 Report Share Posted October 23, 2020 19 hours ago, ½cwt said: Also bear in mind the earlier cars have no tc as standard.... CFA Link to comment Share on other sites More sharing options...
K.I.T.T. Posted October 23, 2020 Report Share Posted October 23, 2020 26 minutes ago, ½cwt said: 19 hours ago, ½cwt said: Also bear in mind the earlier cars have no tc as standard.... CFA Neither did the later cars. Link to comment Share on other sites More sharing options...
½cwt Posted October 23, 2020 Report Share Posted October 23, 2020 2 minutes ago, K.I.T.T. said: Neither did the later cars. Does the 987 not have it as standard then? If so I misunderstood. Link to comment Share on other sites More sharing options...
K.I.T.T. Posted October 23, 2020 Report Share Posted October 23, 2020 14 minutes ago, ½cwt said: Does the 987 not have it as standard then? If so I misunderstood. I thought you meant later 986s, as you were following on for The Baron's replay about his early 2.5 You are correct - the 9x7 got PSM as standard. Link to comment Share on other sites More sharing options...
½cwt Posted October 23, 2020 Report Share Posted October 23, 2020 32 minutes ago, K.I.T.T. said: I thought you meant later 986s, as you were following on for The Baron's replay about his early 2.5 You are correct - the 9x7 got PSM as standard. Hence the reduction to 235 rears is largely un-noticed. The OP has a 2002 986 S (no comment as to whether is has tc / stability control) hence my concern in reducing width of rear rubber rather than balancing up from the front. Link to comment Share on other sites More sharing options...
gIzzE Posted October 23, 2020 Author Report Share Posted October 23, 2020 1 hour ago, ½cwt said: Hence the reduction to 235 rears is largely un-noticed. The OP has a 2002 986 S (no comment as to whether is has tc / stability control) hence my concern in reducing width of rear rubber rather than balancing up from the front. I have TC. But it is not really about balancing the car, it does understeer, but not to the point where it is annoying. The thing with the car is it feels like the rear tyres are just a bit too wide, it is very difficult to describe, but it comes across by it feeling a bit too heavy at the rear. To be honest if I had not experienced this before on cars I wouldn't have even thought twice about it. But I think it is worth trying the 235 section rear and see how it feels. I will know in a bit, picking it up in an hour or so. Mind you, chucking it down with rain, so might not get a chance to try it today. Link to comment Share on other sites More sharing options...
PaulQ Posted October 23, 2020 Report Share Posted October 23, 2020 I think it might be down to the weight of the tyre as well. I know there can be a quite a difference even on different makes and models of same size tyre, and the kumho ku39 I took off in 255/40 felt a fair bit heavier then the Contis I replaced them with in 235/45. Both were on approx 5mm. I've recently replaced these with new Goodyear Eagle F1 in the same size and they don't feel as nice, but it could be that fact they are quite noisy which is clouding my judgement somewhat. Wonder what the difference in weight between a new tyre on 8mm, and one say on 3mm would be...? Some say that they can tell a big difference in feel using lighter wheels (I noticed this a lot on my mx5) and I wouldn't be surprised if the tyre weight played an even bigger part in this due to the mass being distributed further away from the centre of the wheel. Link to comment Share on other sites More sharing options...
½cwt Posted October 23, 2020 Report Share Posted October 23, 2020 27 minutes ago, PaulQ said: I think it might be down to the weight of the tyre as well. I know there can be a quite a difference even on different makes and models of same size tyre, and the kumho ku39 I took off in 255/40 felt a fair bit heavier then the Contis I replaced them with in 235/45. Both were on approx 5mm. I've recently replaced these with new Goodyear Eagle F1 in the same size and they don't feel as nice, but it could be that fact they are quite noisy which is clouding my judgement somewhat. Wonder what the difference in weight between a new tyre on 8mm, and one say on 3mm would be...? Some say that they can tell a big difference in feel using lighter wheels (I noticed this a lot on my mx5) and I wouldn't be surprised if the tyre weight played an even bigger part in this due to the mass being distributed further away from the centre of the wheel. Unsprung mass is a big factor in the suspension dynamics. All the inertia every time the suspension moves relative to the body position. Link to comment Share on other sites More sharing options...
gIzzE Posted October 23, 2020 Author Report Share Posted October 23, 2020 OK, picked the car up, obviously early days, damp roads and new tyres don't inspire pushing them to properly test grip levels, but first impressions are pretty good. It just feels a bit lighter on its feet, and that was what I was hoping for. There isn't a massive difference, but there is a difference. Looking forward to bedding them in a bit more and seeing how it goes. Link to comment Share on other sites More sharing options...
Ninesomething Posted October 23, 2020 Report Share Posted October 23, 2020 I can't imagine wanting less grip at the back. Whether the car understeers or not is totally down to how you drive it. If you drive it on the throttle as Dr Porsche intended (I imagine) then it's on the verge of oversteer at any given point. That's why god invented PSM. To save my untalented ar*e. Fun though..... Link to comment Share on other sites More sharing options...
PaulQ Posted October 23, 2020 Report Share Posted October 23, 2020 3 minutes ago, JonSta said: I can't imagine wanting less grip at the back. Whether the car understeers or not is totally down to how you drive it. If you drive it on the throttle as Dr Porsche intended (I imagine) then it's on the verge of oversteer at any given point. That's why god invented PSM. To save my untalented ar*e. Fun though..... It's not about outright grip, or driving at or on the limit. I can feel the difference just driving around town. You must have driven a lighter, or at the other extreme heavier rear wheel drive car at some point.? The difference is akin to that feeling , albeit to a much lesser degree. Link to comment Share on other sites More sharing options...
Ninesomething Posted October 23, 2020 Report Share Posted October 23, 2020 Yeah I had a Subaru with wide 18 aftermarkets on. When I had them refurbed I put the stock skinnies back on. Steering was sharper but it became a drift car - poss due to the 380 ft/lbs at 2750 rpm. Fun but I'd got used to the total unstickability of it wet or dry. Like I said if I'm having fun PSM is on quite often and it's always the back setting it off not the front which means I don't need less rear grip. Thinking back to when the 911 was a bit of a widowmaker due to sudden terminal lack of grip if you lifted off mid corner I guess Porsche wanted to give the car as much rear grip as possible. It is a fact that what's best for feel and handling isn't always best for ultimate roadholding. Link to comment Share on other sites More sharing options...
PaulQ Posted October 23, 2020 Report Share Posted October 23, 2020 1 hour ago, JonSta said: Yeah I had a Subaru with wide 18 aftermarkets on. When I had them refurbed I put the stock skinnies back on. Steering was sharper but it became a drift car - poss due to the 380 ft/lbs at 2750 rpm. Fun but I'd got used to the total unstickability of it wet or dry. Like I said if I'm having fun PSM is on quite often and it's always the back setting it off not the front which means I don't need less rear grip. Thinking back to when the 911 was a bit of a widowmaker due to sudden terminal lack of grip if you lifted off mid corner I guess Porsche wanted to give the car as much rear grip as possible. It is a fact that what's best for feel and handling isn't always best for ultimate roadholding. F#ck me...... I can't even unstick my skinny 235's 😂 Link to comment Share on other sites More sharing options...
½cwt Posted October 23, 2020 Report Share Posted October 23, 2020 3 hours ago, PaulQ said: F#ck me...... I can't even unstick my skinny 235's 😂 Try harder my 265s will drift a bit if I want them to. Link to comment Share on other sites More sharing options...
½cwt Posted October 23, 2020 Report Share Posted October 23, 2020 4 hours ago, JonSta said: Yeah I had a Subaru with wide 18 aftermarkets on. When I had them refurbed I put the stock skinnies back on. Steering was sharper but it became a drift car - poss due to the 380 ft/lbs at 2750 rpm. Fun but I'd got used to the total unstickability of it wet or dry. Yep that much torque even in 4WD will give you a problem on 205 tyres on 15" balloons... IIRC. In stock power out put it was just fine. Link to comment Share on other sites More sharing options...
witko999 Posted October 24, 2020 Report Share Posted October 24, 2020 I think I recall that mathematically, tyre width isn't a factor in grip levels. Rather it's the coefficient of friction of the rubber along with the mass of the car that determines the grip. Or something like that. Link to comment Share on other sites More sharing options...
gIzzE Posted October 24, 2020 Author Report Share Posted October 24, 2020 Yeah, with tyres you are trying to get as much force into the contact area possible to increase friction, which in turn increases grip. If you put on a bigger tyre without increasing down force you will actually reduce the amount of force per square inch. It is a bit more complicated than that, and obvious vehicle weight, type of rubber and tire pressure all make a huge difference too. But simply putting on bigger tyres doesn't guarantee more grip. What you often find with wider tyres is owners feel they have lost some steering and chassis feel, the usual recommendation is to increase the tyre pressure, which people do and they get the steering feel back. Probably with that is all you are doing is reducing the contact area beck to what you had previously on the narrower tyre. That is sort of what I was feeling with the 265 wide tyres on the Boxster, to get the back end feeling right I was running 39psi cold, but this seemed too high the back end felt crashy and lost grip, but I could feel what it was doing, drop it down to 36psi and it had better grip, but you lost chassis feedback. So far the 235 section running 36psi seems to have chassis feel and if anything is biting better on fast corners, more grip. Link to comment Share on other sites More sharing options...
PaulQ Posted October 24, 2020 Report Share Posted October 24, 2020 If you lower the pressure, then you will increase the contact patch. A narrower tyre will have a longer contact patch then a wider one. Link to comment Share on other sites More sharing options...
gIzzE Posted November 6, 2020 Author Report Share Posted November 6, 2020 OK, so went out with the car yesterday for an hour on some winding back roads I know well. It was a nice dry day for once!! Impressions? Love it! It has stopped trying to follow the ruts in the road, it was never terrible for this, but did do it, and now it has stopped you realise how much it happened before more than noticing at the time, if that makes sense? The whole car just feels lighter on its feet, the steering feels more responsive and...well... just nicer. The back end when pressing on and trying to provoke it has so, so much more feedback. With TC off, you can really tell when it starts to go at the back, it is very, very progressive. Still hard to get it to let go on the road, but forcing it to on long sweeping corners shows that you can now tell when it is about to, where as before it gripped longer and then snapped, which I really don't like. Don't get me wrong, I would never be going those speeds on the road on a corner, but it is important as you can get that happening at normal speeds if you hit a bit of wet, greasy road and snapping is not what you want. Overall, really pleased I made the move to the 235 section, really pleased. Link to comment Share on other sites More sharing options...
Dan944 Posted November 6, 2020 Report Share Posted November 6, 2020 1 hour ago, gIzzE said: OK, so went out with the car yesterday for an hour on some winding back roads I know well. It was a nice dry day for once!! Impressions? Love it! It has stopped trying to follow the ruts in the road, it was never terrible for this, but did do it, and now it has stopped you realise how much it happened before more than noticing at the time, if that makes sense? The whole car just feels lighter on its feet, the steering feels more responsive and...well... just nicer. The back end when pressing on and trying to provoke it has so, so much more feedback. With TC off, you can really tell when it starts to go at the back, it is very, very progressive. Still hard to get it to let go on the road, but forcing it to on long sweeping corners shows that you can now tell when it is about to, where as before it gripped longer and then snapped, which I really don't like. Don't get me wrong, I would never be going those speeds on the road on a corner, but it is important as you can get that happening at normal speeds if you hit a bit of wet, greasy road and snapping is not what you want. Overall, really pleased I made the move to the 235 section, really pleased. wow this is great! i’ve been following this thread as i know exactly what you mean. i’ve just changed all x4 on mine this week and just done mot today. mine at rear was 265/4/18 and fronts 225/40/18 ive tried a new tyre this time wanted michelin pilot sports but went the cheaper option for now and decided that way i will change the front although they still had 4 mm left. i did however go with 255/45 at rear only by accident as i ordered them wrongly 😫 but think i may go smaller at the rear also as i find the same as your describing with the wider wheels at the rear. i think it’s a very personal drivers character thing, and i also like to feel the car drifting out of it’s limit of grip so i can manipulate the chassis if i need to. 👍🏻 Link to comment Share on other sites More sharing options...
Cheddar Bob Posted November 6, 2020 Report Share Posted November 6, 2020 On 10/23/2020 at 6:33 PM, JonSta said: Yeah I had a Subaru with wide 18 aftermarkets on. When I had them refurbed I put the stock skinnies back on. Steering was sharper but it became a drift car - poss due to the 380 ft/lbs at 2750 rpm. Fun but I'd got used to the total unstickability of it wet or dry. Like I said if I'm having fun PSM is on quite often and it's always the back setting it off not the front which means I don't need less rear grip. Thinking back to when the 911 was a bit of a widowmaker due to sudden terminal lack of grip if you lifted off mid corner I guess Porsche wanted to give the car as much rear grip as possible. It is a fact that what's best for feel and handling isn't always best for ultimate roadholding. I don't think I've had any understeer yet. Plenty of oversteer and I must confess plenty of saving by PSM. Until I make a change, I won't know what the difference is you refer to, but so far I have no complaint with the rear of my box Link to comment Share on other sites More sharing options...
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