Run Flat - Non Run Flat - Tyre pressures
Discussion
fareaster said:
liquidken said:
Keep them the same. The sizes are the same which means the internal volume is the same.
Yes, but the wall stiffness must be completely different, doesn't seem logical that it should be the sameI always run my Z4 real tyres slightly above what I ran with Runflats. S the rears are about 38psi and the fronts about 35psi. As the tyre is much softer sidewall wise I think this suits the car best.
Best is to try them and see how it feels to you. As long as the wear is even across the tyre(which is a laugh on a Z4 anyway in my experience) then it should be OK.
Best is to try them and see how it feels to you. As long as the wear is even across the tyre(which is a laugh on a Z4 anyway in my experience) then it should be OK.
liquidken said:
fareaster said:
liquidken said:
Keep them the same. The sizes are the same which means the internal volume is the same.
Yes, but the wall stiffness must be completely different, doesn't seem logical that it should be the sameI would,therefore, expect to raise the tyre pressure when switching from runflats to non runflats, but not too much.....
This is a good question, I'm a suspension guy not tyres, we need a response from a tyre engineer.
I've heard BMW sell cars in some markets with non runflats, what do they recomend then ?
The M models run lower pressures and go 10 wider and 5% higher on the profile only, with a bit more weight too.
On FK452 18" staggered my Z4 wore the rears down in the middle despite the pressure being 33psi vs 36psi standard.
The fronts were worn on the outside edges, with a fair bit of tread left in the middle, and that was at 31.5psi vs 33psi standard.
Logic would say lower rear pressure would flatten the wear, and increased front pressure would flatten the wear there.
It wasn't a huge dramatic amount, but that was the trend...
If I followed the logic here of raising pressures or leaving them the same, the rears would have gone bald in the middle with 3mm at each side. The fronts would have probably been ok with 33psi.
Currently running 33psi all round on my new F1 Asymmetric... and will see how they go.
Personally I think the FK452 are cheap for a reason. The fronts for example look about 12mm narrower, from sidewall to sidewall, the rears about 4mm... so rim protection is lacking, but also the contact patch must be a bit different again!?
That said, they are so cheap it doesn't matter how they wear vs more expensive ones, because you just replace em more often
They also drive ok.
Hmmmm
Dave
On FK452 18" staggered my Z4 wore the rears down in the middle despite the pressure being 33psi vs 36psi standard.
The fronts were worn on the outside edges, with a fair bit of tread left in the middle, and that was at 31.5psi vs 33psi standard.
Logic would say lower rear pressure would flatten the wear, and increased front pressure would flatten the wear there.
It wasn't a huge dramatic amount, but that was the trend...
If I followed the logic here of raising pressures or leaving them the same, the rears would have gone bald in the middle with 3mm at each side. The fronts would have probably been ok with 33psi.
Currently running 33psi all round on my new F1 Asymmetric... and will see how they go.
Personally I think the FK452 are cheap for a reason. The fronts for example look about 12mm narrower, from sidewall to sidewall, the rears about 4mm... so rim protection is lacking, but also the contact patch must be a bit different again!?
That said, they are so cheap it doesn't matter how they wear vs more expensive ones, because you just replace em more often
They also drive ok.
Hmmmm
Dave
fareaster said:
liquidken said:
fareaster said:
liquidken said:
Keep them the same. The sizes are the same which means the internal volume is the same.
Yes, but the wall stiffness must be completely different, doesn't seem logical that it should be the sameI would,therefore, expect to raise the tyre pressure when switching from runflats to non runflats, but not too much.....
This is a good question, I'm a suspension guy not tyres, we need a response from a tyre engineer.
I've heard BMW sell cars in some markets with non runflats, what do they recomend then ?
Handling characteristics will differ, which is why many people elect to change from RFT to standard tyres. Those who have more than a passing interest in their car will invariably alter the pressures to suit their individual driving style, anyway.
So what do you aim for.
Flat wear (ignoring the usual inside edge wear due to camber)... or handling optimisation?
I've always assumed flat wear meant the best of the tyre doing work most of the time, but is that not right?
In the FK452 on staggered 18's on a BMW at least, they wear down the middle of the rears down at 33psi (so ideally you'd want to run lower), and wear the outsides of the front at 31.5psi (ideally want these higher pressure, so 33psi seems ok there)
So what do you do at the rear? 31psi seems ideal for flat wear it would seem, but 36psi is recommended!?
It seems you have to run more for good performance, but then suffer from wearing out the tyres sooner than is ideal!? (ie, 2-3mm left on outsides of tyre, but to wear bars on middle)
Dave
Flat wear (ignoring the usual inside edge wear due to camber)... or handling optimisation?
I've always assumed flat wear meant the best of the tyre doing work most of the time, but is that not right?
In the FK452 on staggered 18's on a BMW at least, they wear down the middle of the rears down at 33psi (so ideally you'd want to run lower), and wear the outsides of the front at 31.5psi (ideally want these higher pressure, so 33psi seems ok there)
So what do you do at the rear? 31psi seems ideal for flat wear it would seem, but 36psi is recommended!?
It seems you have to run more for good performance, but then suffer from wearing out the tyres sooner than is ideal!? (ie, 2-3mm left on outsides of tyre, but to wear bars on middle)
Dave
I personally always aim for handling balance. In some instances, this can result in less than perfect wear but I'm more concerned with the quality of the ride and my ability to stay on the road than replacing my tyres 2 months earlier than I could have done.
Remember, a staggered set-up with decent section width tyres (255 and above) will have higher wear in the centre due to the forced generated by the RWD configuration which causes the tyre to 'egg' slightly.
Remember, a staggered set-up with decent section width tyres (255 and above) will have higher wear in the centre due to the forced generated by the RWD configuration which causes the tyre to 'egg' slightly.
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