Mixing runflats with non runflats?
- Thread starter jamesgarbett
- Start date
Of course tyre manufacturers are going to state that you shouldn’t mix tyres, it’s done to protect themselves from litigation and [ref]B21[/ref], tyre manufacturers also state that you shouldn’t change from the tyre sizes approved by the manufacturers vehicle homologation, which in some countries is also illegal and can affect your insurance, didn’t stop you though :wink:
No bullshit about whats right or wrong.
I had an e46 330ci with run flat rears and non fronts for 6 months and had no issues doing a 75 mile trip to work daily i didnt drive like a hoonigan.,and all was fine,i dont advocate this as a good idea but if your not driving like our dear departed mr Block you will be fine .just go steady and fit same tyres on aĺl 4 corners as soon as you can
I had an e46 330ci with run flat rears and non fronts for 6 months and had no issues doing a 75 mile trip to work daily i didnt drive like a hoonigan.,and all was fine,i dont advocate this as a good idea but if your not driving like our dear departed mr Block you will be fine .just go steady and fit same tyres on aĺl 4 corners as soon as you can
sars said:
Errrrrr , didn't stop you either
aren't you currently running aftermarket wheels with different tyre spec to how your car left the factory with different offset & different rolling radius ? Top & bottom of it is a car leaves the factory with the capability of running on 17inch , 18inch , 19inch & with those sizes comes a varying weight , width of tyre required & varying profile , the car is also capable of running on summer or winter tyres , presumably all this without causing any risk to the owners .
The cars however would never leave with mixed tyre spec , brand or tread & ultimately this should be adhered to but having a snipe at someone simply for changing their tyre sizes seems a bit rich .
Time to lock this thread, nothing else left to be said now. Nothing quite as polarising as a good runflat thread!
sars said:
I know you are trying to link somehow my judgment on different tyre widths to OE spec to mixing run flats and non runflats..
There are big big differences trying to put these as a parity situation.
I’ve not found any published documents that state that you absolutely cannot use wider tyres…whereas there are a plethora of documents stating that you shall not with regard to mixing run flats and non runflats..
Obviously anyone using your generalisation could f**k up badly a car’s handling with inappropriate tyre sizes, however your accusation was against me personally in my choices…
I would point out..
Rim widths used to support said tyres were always within guidance issued by the tyre manufactures for said sizes
All 4 tyres were from the same manufacturer, same model, same compound, same construction
Choices were based on a large body of public domain information showing no specific handling related issues
I’ve attached specific testing of said issues under controlled circumstances on a BMW rear wheel drive platform exploring said issues
Along with specific guidance from Continental on the matter
My tenacity on this discussion is not with regard to scoring points versus another person’s viewpoint but for the newbie member who might receive advice on runflats that runs contrary to all publish documentation (I’ve found) from accredited sources.
For a good dissertation on effects of various sizes and configurations of tyres this video makes interesting viewing.
https://www.tyrereviews.com/Article/Do-wider-tyres-give-you-more-grip-225-vs-255-vs-285-wide-tyres.htm
Attachments
[ref]mr wilks[/ref], and [ref]B21[/ref], You are partially correct, for the e89 the vehicle passed homologation, that is the European vehicle type approval using three wheel sizes 17, 18 & 19 with profiles ratios that give a similar diameter. if you change those profiles and/or widths thus giving a larger wheel diameter than you have modified the vehicle beyond what was homologated.
I have not stated anywhere that you are stupid for doing such things, it is your choice as it is for the OP to fit mix run-flats with non-run flats, but [ref]B21[/ref], you have, that is hypocritical. Technically speaking you are both (B21 & OP) contravening the specification that was homologated, I just consider increasing the width, ratio and thus diameter worse than mixing tyres types between axles. From a design engineering point of view, all European safety legislation requires things that are likely for the public to do to be considered. Getting a flat and there only being a non-run flat available in your size is probable, especially in some markets. Whereas why would you want to increase the rolling diameter? Certainly not from a performance perspective.
FYI [ref]mr wilks[/ref], the tyre sizes for my winter wheels are per their specification for winter tyres for the M40i
[ref]B21[/ref], As you stated previously, you didn't look very hard
https://www.michelin.com.my/auto/advice/tyre-basics/change-tyre-size
I like the way they used the word imperative in their advice, strong stuff indeed.
Again to both, this is not a criticism of your choices, they are your choices after all and your responsibility.
I have not stated anywhere that you are stupid for doing such things, it is your choice as it is for the OP to fit mix run-flats with non-run flats, but [ref]B21[/ref], you have, that is hypocritical. Technically speaking you are both (B21 & OP) contravening the specification that was homologated, I just consider increasing the width, ratio and thus diameter worse than mixing tyres types between axles. From a design engineering point of view, all European safety legislation requires things that are likely for the public to do to be considered. Getting a flat and there only being a non-run flat available in your size is probable, especially in some markets. Whereas why would you want to increase the rolling diameter? Certainly not from a performance perspective.
FYI [ref]mr wilks[/ref], the tyre sizes for my winter wheels are per their specification for winter tyres for the M40i
[ref]B21[/ref], As you stated previously, you didn't look very hard
https://www.michelin.com.my/auto/advice/tyre-basics/change-tyre-sizeI like the way they used the word imperative in their advice, strong stuff indeed.
Again to both, this is not a criticism of your choices, they are your choices after all and your responsibility.
Love a good tyre thread :?
If you make sure your tyres are in good condition, and drive sensibly, then I'm pretty sure you'll be fine.
I'm more concerned about the 1,000s of cars on the road with badly worn, damaged and aged tyres than I am about anyone using slightly wider tyres than OEM or having a mix of brands or types.
Sars, if you read that link, it says it is imperative not to change sizes because you may change diameter and speedo will be inaccurate or they may be so wide that they stick out of the side of the car!
The problem with "safety" advice from big organisations, is that they're only ever going to give you the most cautious and most simplistic possible opinion. Otherwise, some idiot misunderstands it, does something stupid, and Michelin or whoever get blamed. Michelin didn't write that article because they wanted to give accurate and nuanced advice, they wrote it to avoid being sued.
If you make sure your tyres are in good condition, and drive sensibly, then I'm pretty sure you'll be fine.
I'm more concerned about the 1,000s of cars on the road with badly worn, damaged and aged tyres than I am about anyone using slightly wider tyres than OEM or having a mix of brands or types.
Sars, if you read that link, it says it is imperative not to change sizes because you may change diameter and speedo will be inaccurate or they may be so wide that they stick out of the side of the car!
The problem with "safety" advice from big organisations, is that they're only ever going to give you the most cautious and most simplistic possible opinion. Otherwise, some idiot misunderstands it, does something stupid, and Michelin or whoever get blamed. Michelin didn't write that article because they wanted to give accurate and nuanced advice, they wrote it to avoid being sued.
