A
Anonymous
Guest
Hi, anyone know what pressure these bad boys live at? I have them in my 18".
Thanks,
Steve
Thanks,
Steve
A
Anonymous
Guest
What is that? Lol
lacroupade
Veteran
Even if same size as the original RFTs its not a given that pressure should be the same.
If you fit larger tyres (i.e. more air) pressures can come down, if you fit smaller or lower profile tyres (less air) pressure should go up....but remember that with RFTs the sidewall is carrying more of the cars weight than a normal tyre, so I suspect a bit more pressure wouldn't go amiss with a non RFT, or you may see excessive wear on the shoulders....but it could be an expensive empirical process so you need to find someone who REALLY knows their tyres for a properly informed answer.
I've come across plenty of dickheads in the 4x4 community who fit bigger tyres and then jack the pressure up from mid 20s to mid 40s, when they should actually be dropping it a bit....even some morons who think the "not to exceed" pressure printed on the sidewall is the one to use!!!
If you fit larger tyres (i.e. more air) pressures can come down, if you fit smaller or lower profile tyres (less air) pressure should go up....but remember that with RFTs the sidewall is carrying more of the cars weight than a normal tyre, so I suspect a bit more pressure wouldn't go amiss with a non RFT, or you may see excessive wear on the shoulders....but it could be an expensive empirical process so you need to find someone who REALLY knows their tyres for a properly informed answer.
I've come across plenty of dickheads in the 4x4 community who fit bigger tyres and then jack the pressure up from mid 20s to mid 40s, when they should actually be dropping it a bit....even some morons who think the "not to exceed" pressure printed on the sidewall is the one to use!!!
You use the last number on the tyre to determine pressure difference as it relates to side-wall strength... RFT's are ~88Y and most non-RFT's are ~91Y which generally means you drop stock pressures my 3PSI. Which brings us to what most people run at - 30f/33r. I think the //M uses 31/33 on proper tyres, with its slightly heavier front end.
The RFT pressure (33/36 iirc) is definitely too high. You'll get excessive tramlining too, although its probably not noticable to many as anything is better than the RE050 RFT!
The RFT pressure (33/36 iirc) is definitely too high. You'll get excessive tramlining too, although its probably not noticable to many as anything is better than the RE050 RFT!
I've found 33 front and 35 rear about right on my staggered 18's.
The rears have, once again, worn more on the centre of the contact patch than the edges, suggesting that the pressure is still too low. 33/35 f/r seems like a good place for F1's... drop much lower and they feel crap.
FK452 were totally different, they wore almost flat in the middle with 1.5mm still on the edges at 33psi. I simply couldn't get them to wear reasonably at all. If you went lower on the pressure they just went horrible.
Anyone else noticed F1's go off very quickly with temp? 6 degC they are grippy, drop to 4degC and they are significantly more slippy. Get to 0degC and they are really bad. Still predictable and smooth, but you can easily get them spinning and the whole car four wheel drifting around if you push them a bit.
I thought the FK452 were bad, but the F1's seem worse for outright grip in the cold/wet.
I rekon the RE050's are still the best tyre all round for wear/life/grip in all winter/summer conditions etc (bar the rft harshness)... anyone ever tried them in non-rft though?
Hmm
Dave
The rears have, once again, worn more on the centre of the contact patch than the edges, suggesting that the pressure is still too low. 33/35 f/r seems like a good place for F1's... drop much lower and they feel crap.
FK452 were totally different, they wore almost flat in the middle with 1.5mm still on the edges at 33psi. I simply couldn't get them to wear reasonably at all. If you went lower on the pressure they just went horrible.
Anyone else noticed F1's go off very quickly with temp? 6 degC they are grippy, drop to 4degC and they are significantly more slippy. Get to 0degC and they are really bad. Still predictable and smooth, but you can easily get them spinning and the whole car four wheel drifting around if you push them a bit.
I thought the FK452 were bad, but the F1's seem worse for outright grip in the cold/wet.
I rekon the RE050's are still the best tyre all round for wear/life/grip in all winter/summer conditions etc (bar the rft harshness)... anyone ever tried them in non-rft though?
Hmm
Dave
lacroupade
Veteran
Mr Whippy said:
I hate to piss on your parade but wear on the centre of the tyre tread is about as CLEAR an indication of serious OVERINFLATION as you could wish for...when you overinflate the centre of the tyre bulges, when you underinflate its the edges (or shoulders) of the carcass that wear first.
Don't take my word for it, ask your local tyre place, then go somewhere and beat yourself quietly with a cheese grater...
Mr Whippy said:
Didn't experience that - mine worked great all through the winter, my town / countryside commute saw those sorts of temp variations. Coped well in the snowy days too - enough to get to and from work each day. Slight disclaimer, these were on 17 225s with the softer 2.5 setup, so not a like for like comparison.
Ran them at RFT pressures IIRC. Probably my favourite tyre to date
A
Anonymous
Guest
Great thread so far chaps, thanks.
Yep, as above, wear in the centre of the tyre is typically over-inflation. My fronts wear perfectly at 30psi. Rears have SLIGHT extra wear in the inside centre (~0.5mm at replacement time), but this is probably down to the width of the tyre,my high average speed, plus the aggressive camber of the Z4.
Wide tyred cars driven mainly on motorways at high speed will show central wear even with correct pressure. This is due to the centrifugal force, pulling the tyre away from the rim.
Wide tyred cars driven mainly on motorways at high speed will show central wear even with correct pressure. This is due to the centrifugal force, pulling the tyre away from the rim.
lacroupade said:Mr Whippy said:
I hate to piss on your parade but wear on the centre of the tyre tread is about as CLEAR an indication of serious OVERINFLATION as you could wish for...when you overinflate the centre of the tyre bulges, when you underinflate its the edges (or shoulders) of the carcass that wear first.
Don't take my word for it, ask your local tyre place, then go somewhere and beat yourself quietly with a cheese grater...
Unfortunately the wear profile isn't indicative of the right or wrong pressure.
I had to lower my FK452 to 29psi to reduce centreline wear, but the car oversteered everywhere and drove extremely badly.
The F1's NEED 35psi to drive right.
Drop to say 32psi and the back end of the car just feels all wooden and dead.
The big problem is contact patch shape.
Lower the pressure and the patch flattens, but can't get wider, so becomes longer. It's that length/width ratio that impacts handling.
You will naturally wear a tyre incorrectly for the desired handling/contact patch shape, if you put that over the wear being flat. I do on the Z4!
However, it seems the FK452 are really bad for it. There is no ideal compromise. You either wear the centre off a great deal too soon, or run too low pressure and it drives like crap.
The RE050 seem ideal in this regard, I wonder if it's down to their stiffer sides naturally, due to RFT... hmmm...
Dave
lacroupade
Veteran
Mr Whippy said:
Its interesting to note that with two different types of tyre, including the 'legendary' 452s, both seemingly run at too high a pressure, you seem to have trouble when they are run at what are probably the correct pressures (especially as they are clearly suffering from overinflation wear).....not sure what that means but what if theres an underlying suspension issue? :|
A
Anonymous
Guest
So 33 and 35 then lol
lacroupade said:
I thought this was standard fare for 'wider' tyres with some negative camber.
I asked on Pistonheads a while back about it, and not being able to find the right pressure (ie, too low and it drove like crap, but as soon as I got anywhere high it was clearly wearing the middle down)...
Apparently it's just a feature of wide tyres and camber.
I'm not saying the effect is huge, if I could have worn them flat maybe I'd have had 10% more miles from the F1's, but on the FK452 I'd say that would be more like 15%, but it's still interesting
The RE050's I had on wore flat, so it seems to be that RFT can sustain the stiffer sides to go with the stiffer centre better, and wear flatter still!?
Hmmmm
Dave