326M Tyres - A few Questions.

C

Colin_E

Member
 North Hampshire
I'm weighing whether to replace my RFTs yet and research here & elsewhere raises as many questions as answers. You're a helpful bunch though so i hope you might be able to shed some light. :D

#1 Since I'd prefer to keep the 19in 326Ms is a decent quality non-RFT (I'm thinking Michelin PS4S) going to do much to reduce the risk of cracking the rims?

#2 I've read that some people replace the 255/30 rears with 255/35s to improve comfort. Presumably that too should give the wheels a little more protection? I think I saw someone suggesting that a 245/35 was a better option (dunno why though). I'm unclear here :
a) about how far if at all these dimensions can be changed
b) whether and to what extent it is safe & legal to do so - would going to a 35 profile or for that matter a 245 width invalidate insurance?
c) whether a variation at the rear needs a corresponding change to the front?
d) any other issues to watch out for associated with width or profile changes.

#3 Does changing RFT to non-RFT and/or changing dimensions have an impact on TPMS? Does anything need to be replaced or modified?
 
Just done this a few weeks ago, swapped my 35i tyres from Bridgestone potenza RFT (90% teflon junk) to Michelin PS4S, increased rear profile tyre from 30 to 35 and left the fronts at 35.
Ride smoothness is transformed and no your rims will not crack.
No you dont have to increase front profile as well
You can add a bit of width say 255 to 265 I may do this next time but my stage 1+ car is fine on 255's so far.
No change to TPMS, this system gets its info from your ABS sensors, when you inflate/check your tyres you (hopefully) carry out the calibration on iDrive each time. This basically tells ABS how fast your wheels go round at certain speeds, if you get a flat tyre width reduces, rpm increase and TPMS sees this and reports.
PS4S is a premier performance tyre and worth every penny, if you do deep research they come top across as an average over all reviews. Asking tyre dealers who drive performance cars for a recommend will usually result in "PS4S is the way to go mate". If your budget goes that far buy them but shop around online for best deal, I paid £616 for a full set.
 
Oh this is going to be another bonfire.. :tumbleweed:

All these are IMHO...

1). It reduces the chance but doesn’t eliminate it..several people have had 326m crack on non runflats

2) 255/35 or 245/35 would work and many have done that..not sure about going to a 45 profile?

You need to advise your insurance but technically it’s not illegal from an MOT perspective..

When it comes to relative profiles there are two issues stability control/abs and TPMS

If you have a second generation TPMS that displays actual pressures then it’s irrelevant..if you have a first generation system then it lumps in with abs/stability control

In those cases the rolling radius/diameter of both front and wheel rear combos need to be closely matched..no specific number but he advise is to keep any difference to less than 3% max allowing for cumulative differences in part worn/new tyre combos..

The experts will be along shortly..
 
I think the changeover for tpms occurred in 2014 sometime, my sep13 facelift car uses the abs sensors.
I’ve had 326 wheels crack after changing to non rf tyres, throwing away the oem tyres does help, but the rims are still made from eggshells :cry:
Rob
 
Not sure what my TPM or TPMS actually is - car is a 2015 model. What distinguishes one from t'other?

Do you think the following formula is reliable enough to work out whether a combo is within a 3% tolerance?

Rim (in cm) + [(Width * Profile/100) x2] = Total Diameter

That would give rear of 63.56 and front of 64.01 for the existing combos - so less than 1% variation

Same formula would suggest that increasing rear tyres to 255/35 would increase rear diameter to 66.11 which is just outside of 3% :headbang:

That might explain why someone proposed a rear tyre of 245/35 as it would give a diameter of 65.41 (2.2% variation)

Hmmm :?
 
Yours will be a second generation version..

The best tool..imho ..is this one..answers all your questions on tyre fitment, steering offset, rim size and speedo error/rolling radius etc..thumbsup:

https://www.wheel-size.com/calc/
 
OP.....IMHO you are wasting your time with the 326 alloy wheels as they are not robust enough for UK roads, they are a fantastic looking alloy and compliment the E89 well but that is all !!!! Go and invest in another OEM alloy fit for purpose or purchase a good quality aftermarket alloy. One of the best things I have done to my E89 was ditching the RFTs and selling for peanuts the oh so fragile bone china 326 alloys👍
 
Boltz said:
OP.....IMHO you are wasting your time with the 326 alloy wheels as they are not robust enough for UK roads, they are a fantastic looking alloy and compliment the E89 well but that is all !!!! Go and invest in another OEM alloy fit for purpose or purchase a good quality aftermarket alloy. One of the best things I have done to my E89 was ditching the RFTs and selling for peanuts the oh so fragile bone china 326 alloys👍
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I concur apart from the fact I got £1,350 inc run flat tyres on ebay when I sold mine.. :thumbsup:
 
mr wilks said:
The 326 & 296 are both a9j rear which is why a 245-35 is a perfect option over the 255-30 or a 255-35
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Sligtly off topic.. for my winter tyre set on 17" rims very limited choice on 9J type rear rims in 255..so I'm probably going to go for a 245/40 rather than 255/40 :thumbsup:
 
Pbondar said:
I concur apart from the fact I got £1,350 inc run flat tyres on ebay when I sold mine..
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Well done for getting that amount for some bone china and some Teflon, you sound like you could sell snow to an Eskimo😃. I do like the look of those M3 satin black alloys currently for sale on this forum, must admit very tempted.
 
Boltz said:
Pbondar said:
I concur apart from the fact I got £1,350 inc run flat tyres on ebay when I sold mine..
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Well done for getting that amount for some bone china and some Teflon, you sound like you could sell snow to an Eskimo😃. I do like the look of those M3 satin black alloys currently for sale on this forum, must admit very tempted.
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I did do/still do some sales n marketing so a bulk order of sand to the Saudis is one of my specialalities! :rofl:

You should do it..join the non silver wheel brigade..you know it makes sense :thumbsup:
 
I am going to definitely join the non silver brigade and I do like those M3 alloys but then again my current set would look good in black and could be stripped and powder coated for £300
 

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So would it be fair to say that the majority view here is that the 326M's aren't really worth trying to save? Not sure I want to spend £600 on tyres to try to preserve wheels that will either break anyway or are otherwise worthless. So much for seeking clarity :lol:
 
Colin_E said:
So would it be fair to say that the majority view here is that the 326M's aren't really worth trying to save? Not sure I want to spend £600 on tyres to try to preserve wheels that will either break anyway or are otherwise worthless. So much for seeking clarity :lol:
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If the roads you drive on are as smooth as a billiard table you shouldn’t have any problems, accidentally hit a nasty pothole however & you’re in the lap of the gods... :cry:
Rob
 
If you happened to be behind me whilst I am driving my Zed all you will see is me weaving all over the place trying to avoid potholes!!!! A sign of the times I’m afraid 😦
 
i made the the switch from M326 during lockdown due to a cracked rim. now have some M343 replicas on. 9J up front and 10J in the rear.
 

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Colin_E said:
So would it be fair to say that the majority view here is that the 326M's aren't really worth trying to save? Not sure I want to spend £600 on tyres to try to preserve wheels that will either break anyway or are otherwise worthless. So much for seeking clarity :lol:
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Why not swap your tyres and see for yourself, if you continue to get problems, you probably wont, then shell out big money for new alloys. Remember that the experiences of one person are not facts so dont take them as such. Buy the PS4S in 35 rear profile and take it from there, you will be fine.
 
The combination of runflat tyres and 19" rims puts you at the greatest risk of cracking a rim.

If you like and want to keep your 19" rims, then ditch the run flats. If you're set on keeping runflats, then downsize the alloys to 18s - though you'll still need to avoid potholes!
 
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