Space Saver Spare so I can replace my RFTs

[Jezzaaa]

Hi all...hope you're all well

I'm on the verge of casting aside the ruinous run flats and engaging some Michelin PSS goodness instead. I live in the middle east though, and don't like the thought of being stuck on a desert road in the middle of .... well, the desert ... with a flat and no spare and just a can of gunk.

So I've been looking around for a space saver spare and found this:

http://www.bimmerzone.com/BMW_Performance_Spare_Tire/BIM-SST-E89-KIT.html

Thing is, it says it's for 20i, 28i, 35i...but that it's NOT TESTED WITH 35is or M sport brakes. Which is of course what I've got (at any rate, I have the 35is car...whether it's got M Sport Brakes or not, I don't know how to tell).

I guess the stud pattern and the overall tyre diameter will be the same as the 35i. So the only thing I can think of that might be an issue is if the brake rotor or calliper on a 35is a different size to the 35i since they have tested it with a 35i?

My car is a standard 35is, but with the 19" 326M wheels.

Any and all help would be appreciated

Thanks,
J.

 

[Angie4m]

Firstly, where are you going to keep this? If you store this in the boot you will need to ensure it is sure there is no room underneath for it. Secondly if its been tested with a 35i then it would also fit a 35is and thirdly the rolling circumference is what matters. I am assuming that its only designed to be used with a maximum of 18inch wheels and not the 19s and so this won't help.

Ideally you might want a can of gunk and a compressor.....just incase instead

 

[Nictrix]

A lot of space saver wheels can only be used on the rear of the car because the rear brakes are often smaller than the fronts.
This means if you get a puncture in a front wheel you would swap the rear onto the front and put the space saver on the rear.
This obviously wouldnt work with staggered wheels, I dont think you could fit a 255 on the front even just to get you home.

 

[flybobbie]

Why not use a standard wheel, after all you are going to loose most of the boot space anyway.
I think if i was driving in a desert region, probably wouldn't drive a BMW!
In 2 1/2 years have had five punctures.
3 screws which were slow enough to drive around for a few days and two pothole damage that took the side wall out of the nearside tyres in one go. No spare would have helped there, so just drove home on the deflated tyres. They were non RFT. No harm was done to rims.

 

[lux]

I don't get all this 'ditch the run flats' shite....unless you're trying to get another couple of seconds out of a lap time!?
I've had run flats on 18" for 3 years and 19" for two and never thought about swapping them as my ride is fine with them on, and they will get me home if I get a puncture. :?

 

[Jezzaaa]

Thanks for all the replies

AngieM - you make good points. There is space, with the hood cover in position, to store the skinny spare with cover. I don't think there's enough depth to store a full size wheel and be able to have roof down.
I think it's the size of the brakes which is the key thing here. I don't think the size of the proper wheel is of relevance, since with either size wheels, the brakes stay the same. So I just need to find out if the skinny spare will fit over the front and rear brakes. My assumption was that if they have tested it ok with the 35i....and the 35i has the same brakes as the 35is, then it should work on the 35is too.

Flybobby - We do have proper roads here...it's just they go through huge tracts of desert with no civilisation. If you break down, it takes a long time to get recovered ... and at 45 degrees it's not pleasant! I don't think there's room for a full size wheel and be able to put the roof down. Nice idea though

Lux - I guess it's all subjective...at the moment, the cars ride is hard which is fine...but it crashes and bangs when going over catseyes and potholes...and it's a bit squirmy and unpredictable when cornering hard. And I'm lead to believe that changing to standard tyres will improve it mightily. Certainly in my Z4M Coupe (my last car before I left the UK) I never had these problems...and that had very hard suspension and non RFTs. So I presume that my current car could at least become more like that by changing the tyres. I'll let you know how I get on

 

[Angie4m]

I think you'll find that the size of the wheel you intend to use it with is relevant because like I said its not how big the space saver is but the rolling circumference. So a 16inch space save would possibly have the same rolling circumference as at 18inch wheel but not the same as a 19 inch wheel and that is not only dangerous but illegal. The standard wheel size supplied is 18 inches and the 19s are an optional extra so most likely are not compatible rolling circumference wise. I had the same issue with a FN2 civic, if I had 18s I could use the 16inch space saver but not with 19s soley down to this issue.

You will also require a net to be fitted as its against the law to have a tyre unsecured. So this will be an additional cost on top of the kit you are looking to purchase.

I was also thinking about space in the event that you want to actually put stuff in your boot, unless you take the wheel out it won't leave a lot of room and almost nothing with he roof down.

you would need to check what UK law says with regards to percentage differences in rolling circumference but it's looks like from the link it's maybe 1.2% based on 225/35r 19

 

[Jezzaaa]

Hi Angie - Interesting

I'm probably being ignorant here and I know I've asked for advice and am now challenging what's been given...so forgive me!!!

I'm assuming, since the link is for an E89 space saver spare specifically, and that they don't distinguish in their description about what size rims are fitted; just that it's compatible with 20i, 28i and 35i, that the rolling circumference of both 18" and 19" wheels must be the same, where the difference is the tyre side wall size?? Otherwise would they not have loads of different skinny spare wheel sizes for E89s and specify particular rims and circumferences so you could choose the correct skinny spare for your car?

Ta,

J.

 

[TitanTim]

I would be surprised if you would get a spacesaver to fit in the boot never mind an 18 or 19" wheel and say if you could there is no way you could have the roof down.

If being stranded really worries you why not install puncturesafe?

Tim.

 

[Stark]

A skinny spare only needs to be one size.....regardless of what sizes the other wheels are....

 

[Angie4m]

As Stark says a skinny spare only needs to be one size, however BMW do not do a spare wheel for the E89 and this one if for a E60, previous gen 5 series. Also the E89 comes with 17 or 18inch wheels as standard and I believe only the 35is comes with 18s so it's likely it's only been tested with 17s but they do not advise.

I've checked the front and rear sizes vs the space saver and it's positive 1.25% difference rolling circumference for the front and positive 1.89% on the rear so that would be an acceptable difference I believe as a recommended difference is plus or minus 2.5% in the UK and I'm sure this would also be acceptable in the Middle East.

I assume when you do change the tyres you will be sticking with the same size ie 225/35r19 and 255/30r19 if not then this will need to be taken into consideration when using a spacesaver as the calculation is based on he current sizing. Even a slight change in the profile will cause it to become well over 2.5%

 

[Jezzaaa]

As Stark says a skinny spare only needs to be one size, however BMW do not do a spare wheel for the E89 and this one if for a E60, previous gen 5 series. Also the E89 comes with 17 or 18inch wheels as standard and I believe only the 35is comes with 18s so it's likely it's only been tested with 17s but they do not advise.

I've checked the front and rear sizes vs the space saver and it's positive 1.25% difference rolling circumference for the front and positive 1.89% on the rear so that would be an acceptable difference I believe as a recommended difference is plus or minus 2.5% in the UK and I'm sure this would also be acceptable in the Middle East.

I assume when you do change the tyres you will be sticking with the same size ie 225/35r19 and 255/30r19 if not then this will need to be taken into consideration when using a spacesaver as the calculation is based on he current sizing. Even a slight change in the profile will cause it to become well over 2.5%

Thanks for your advice and patience Angie...much appreciated