Tyre Pressures after removing runflats E93 330i

[c4sman]

Hi all, Need some advice. Recently swapped out Bridgestone runflats to Michelin PS4 non runflats and read that I may need to change tyre pressures. Car is an E93 330i and feels 10x better on standard pressures but I want to make sure they are properly adjusted.

Thanks in advance.

[Prinny]

You don’t say what wheel size you’re running, and whether or not you’ve a staggered setup.

Assuming 19” and staggered (i.e. msport), then 38f, 41r is a good starting point.

The e93 is heavier than the coupé though, you might even want to go slightly higher.

[c4sman]

Sorry, good point. It’s an E93 MSport on 18s (225 Front and 245 Rear). thanks!

[Prinny]

245 isn’t a standard size on the e9x afaik - should be 255 I think. (But 10mm isn’t enough to worry about until you come to replace, so I wouldn’t sweat that).

On 18” you should be able to go a couple of psi lower than the 19”. I’d suggest starting with 36f, 39r and taking it from there.

Going too low on the rear, with the -ve camber a 3-series runs will accelerate inside shoulder wear, which can be hard to see - unless you’re following the car - seen more than a few over the years with cords showing on the inside!

[Swervin_Mervin]

Stick to the standard pressures. Why would they need to be any different?

[RafflesNH]

Swervin_Mervin said:

Stick to the standard pressures. Why would they need to be any different?

I can see his point. I have wondered about the difference in tyre wall stiffness between the runflats and non-rfts necessitating an increased pressure for the non-rfts to compensate perhaps. However, I kept the same pressures (35F/39R for normal use or 37F/42R for moderately laden motorway touring) when I changed to non-rft PS4s, and no uneven wear seen across the tyre tread. However they do seem to wearing down quicker than the OE PS2 rfts, but that's another story! Can't really comment about handling on the limit, as I don't drive that way. But when i like to make progress, they seem just as predictable as the rfts, but with a more compliant ride, imo.

ps. I too use 225/40(Front) and 255/35(Rear) on 18" wheels

[Smuler]

I swapped bridgestone rft to Michelin non rft on a 335i, I used the stock pressure as per the door jam.

worked well for me. Michelin, BMW agreed this was correct.

[c4sman]

Prinny said:

245 isn’t a standard size on the e9x afaik - should be 255 I think. (But 10mm isn’t enough to worry about until you come to replace, so I wouldn’t sweat that).

Sorry, yet another senior moment from me. Yes they are the standard 255s on the rear as you say. I’m tempted from the mixed view to stay standard pressures and monitor wear. Handling wise the car is transformed after the switch (and is on standard pressures). It used to feel like it had no suspension over bumps, now it’s much more compliant and comfortable but with more accuracy and confidence when pushing on, which is the perfect blend. Also it used to sniff out every camber or road scar and wander around at the front end meaning the drive was never completely relaxed. Now it’s as if they are not there and it goes where you point it. Wish I’d done it sooner as I’ve had the car 18 months. Was thinking of trading for an M3 sometime soon but gonna hang on to enjoy this as a cruiser a little longer.

[tgr]

Are you having any problems with the N53 engine? Plenty of people seem to, judging from postings on here.

Leaky injectors that need replacing at £1200 a set seem to be a key weakness

[RafflesNH]

tgr said:

Are you having any problems with the N53 engine? Plenty of people seem to, judging from postings on here.

Leaky injectors that need replacing at £1200 a set seem to be a key weakness

I don't wish to sound complacent, but so far so good on my 2008 car running on original injectors, and high pressure fuel pump, although I did have some lumpy running for a short while whilst using supermarket fuel. After adding a can of BMW's own petrol additive, that issue went away. And then after reading about Honest John's frequent beseechings to motorists to only use fuel with cleaning agents, such as Shell V+ Nitro, I started using that regularly, and the engine seems much better for it. The trademark GDI injector clatter is quieter and the exhaust tips stay clean.

I'm also on the original coil packs, but I don't believe that can be fuel quality related.

[c4sman]

tgr said:

Are you having any problems with the N53 engine? Plenty of people seem to, judging from postings on here.

Leaky injectors that need replacing at £1200 a set seem to be a key weakness

Early days for my ownership (18 months) but my car is on 63k miles (bought with 54k mile) with a full BMW and now Munich Legends service history so i dont know about previous problems, but it runs beautifully at the moment. I always treat it to V Power, unless really inconvenient and reading previous post i will try even harder!

[Dannbodge]

Standard pressures are fine

37 rear, 35 front for me normally
If going on a long run I'd probably go 38R, 36F