Your experience / recommendation on Geometry set up.

[dario]

Ok, as some might have seen i have recently had an MOT failure due to a pair of rear cracked 19 inch wheels on my 35i E89. That is being resolved as i type this.

I've read through a thread which fairly exhaustively discussed the issue of geometry that potentially affected / exacerbated the situation where some nice person took the time to draw a CAD drawing to try and show the situation.

I've also read this on a suspension companies website:

The run-flat tyre has been the desire of many tyre manufacturers over the last 30yrs. Its obvious safety features encouraged exhausting development advances but despite this the original embryo the Run-Flat tyre looked like it was deemed to failure.

In the late 90's Bridgestone launched their version of the RFT (Run-Flat-Tyre) which in essence is not too distant from an ordinary tyre in appearance. Nevertheless this tyre, undressed is far from similar to a conventional tyre.

Bridgestone's design required the tyres sidewall to be reinforced, "armoured" is a closer description so that the tyre is able to support the car when fully deflated. I, for one salute Bridgestone for finally bringing this necessary safety feature for the first time in a useable context, but unfortunately there are problems.

Most people would know that the tyre full of air has a reasonable level of compliance acting as our first line of defence deflecting the poor road condition however things appear to be quite different with the Run Flat. By compromise, all BMW's fitted with RFT's have downgraded (softer) suspension to absorb the migration of these road shocks. Unfortunately this doesn't appear to be perfect as we are starting to notice that this shock migration appears to transmit some of these forces to the wheel rim, and actually cracking it in some cases without amazingly, any apparent harm to the tyre itself. We are currently monitoring this but it is something that owners of Run Flat Tyres must keep a keen eye on and in the avoidance of doubt... stay away from pot holes.

BMW run flat problems

As with a lot of things today we have to make compromises and the safety benefits of Run Flat Tyres are not in question, though we will continue our studies into this shock migration very thoroughly. However, "What about the actual inconsistent and premature tyre wear?" Wheels In-Motion, surprise surprise, has found the solution!

The BMW suspension allows superb handling characteristics providing that the tyres contact patch can be maintained. In order to do this the wheels vertical position (camber) is tilted and along with careful and sensitive suspension and geometry adjustments to compliment this, allows both tyre and suspension to follow the same radii thus maintaining that all important tyre contact patch

The consequence of camber alone conically deforms a normal tyre sidewall, however if the correct maths are used in suspension adjustment, geometry and alignment thus allowing the cars weight to be evenly distributed across the tyre, all can be encouraged to work together in harmony.

The problem some BMW's have is that the RFT's do not deform and do not allow a conical profile because of the rigidity of the tyre and sidewall, meaning they cannot distribute the cars weight evenly easily, but before you depart your beloved BMW in despair, once again we have solutions to address this.

We can establish the camber curve and adjust the chassis accordingly allowing the RFT to maintain a solid, predicable footprint during the suspensions transitions. Our chassis adjustments belays the fact the RFT cannot deform, maintains the BMW handling and prevents the adverse tyre wear. Once again, regular alignment checks and calibration by Wheels In-Motion will maximise tyre life and handling without compromise. It just needs a little more thought, care and attention.

Tony Bones (Blackboots / Wheels In-Motion).

END

I've run BMW cars for a fair while and with 12-13 years in Z4 a couple of years in an E92 335d and now about 2.5 years in a 5 series GT 335d. the one thing in common with these cars is that they all prematurely wear out the inside edge of the tyre leaving many 1,000s of miles on the remainder of the tyre whilst getting to the cords in one occasion (inspected without getting under the car)

so the question is: do any drivers of the E89 have any experience of setting up the geometry of the car which is not aggressive Negative for track use, but more sympathetic to getting a balance between cornering grip and longevity.

if you do, i'd like to know the set up figures you used to achieve this setup and how it felt in rear world driving. As i say this has affected all the BMWs i have owned since 2005 so its not a new phenomenon.

[Busterboo]

Tony Bones' English is as flawed as his science. So, just as he confuses "exhausting" with 'exhaustive' and "belays" with 'belies', he also believes his assumptions about RFTs are a substitute for research.

This belief is probably prompted by two factors: lack of education and, more significantly in this case, a desire to make money.

[dario]

Ok, so other than an English lesson and with the lack of empirical information, what is your suggestion and experience about my general question?

[Busterboo]

Ok, so other than an English lesson and with the lack of empirical information, what is your suggestion and experience about my general question?

1 It wasn't an English lesson, but a comment about Mr Bones, because ...
2 His blurb says, 'I know the answer. Trust me.'
3 However, my experience was to use 'Center Gravity' [sic] in Atherstone, just off the A5 in Warwickshire.
4 There, Chris Franklin has a second-to-none reputation for excellence among Porsche owners, but he also does work on Ferrari & other high-enders and people travel to him from all over the UK.
5 So, that's my suggestion. http://www.centregravity.co.uk/

(The reason, in an earlier post, I asked about the rear tyre pressures you use was that, as I'm sure you know, single-edge wear can be exaggerated by incorrect inflation.)

[dario]

ok, that explains it better.

the tyre pressure will be as per manufacturers recommendation on all of the cars with the Exception of the E85. As they were truly terrible with runlets on it was always an experiment to try and balance tyre pressure and handling. I did find that the lower the pressure (within reason) the better the ride quality, however at the expense of fuel economy.

i'll bear the suggestion of centre gravity in mind.

thanks for the input.

[john-e89]

Tony Bones' English is as flawed as his science. So, just as he confuses "exhausting" with 'exhaustive' and "belays" with 'belies', he also believes his assumptions about RFTs are a substitute for research.

This belief is probably prompted by two factors: lack of education and, more significantly in this case, a desire to make money.

You can off course provide evidence of Tony's lack of research in as much as you can provide evidence of Centre gravity having theirs, it being varified by the relevant institutions for you to have a bias. Or are you just having an opinion on one guy you don't rate, based on what,? over another guy you do rate, based on what,? neither of which have any scientific verified proof of anything? Please do enlighten us or are you guessing just like anyone else that as AFAIK there is no varified scientific proof of why wheels crack.

[Busterboo]

Tony Bones' English is as flawed as his science. So, just as he confuses "exhausting" with 'exhaustive' and "belays" with 'belies', he also believes his assumptions about RFTs are a substitute for research.

This belief is probably prompted by two factors: lack of education and, more significantly in this case, a desire to make money.

You can off course provide evidence of Tony's lack of research in as much as you can provide evidence of Centre gravity having theirs, it being varified by the relevant institutions for you to have a bias. Or are you just having an opinion on one guy you don't rate, based on what,? over another guy you do rate, based on what,? neither of which have any scientific verified proof of anything? Please do enlighten us or are you guessing just like anyone else that as AFAIK there is no varified scientific proof of why wheels crack.

In some ways, fair comment.

My blurb for Center Gravity was no better than Tony Bones' for his work.

As for your point about 19" wheels, however, my answer is that I wouldn't use them, because they crack. I don't need to know why.

[john-e89]

Tony Bones' English is as flawed as his science. So, just as he confuses "exhausting" with 'exhaustive' and "belays" with 'belies', he also believes his assumptions about RFTs are a substitute for research.

This belief is probably prompted by two factors: lack of education and, more significantly in this case, a desire to make money.

You can off course provide evidence of Tony's lack of research in as much as you can provide evidence of Centre gravity having theirs, it being varified by the relevant institutions for you to have a bias. Or are you just having an opinion on one guy you don't rate, based on what,? over another guy you do rate, based on what,? neither of which have any scientific verified proof of anything? Please do enlighten us or are you guessing just like anyone else that as AFAIK there is no varified scientific proof of why wheels crack.

In some ways, fair comment.

My blurb for Center Gravity was no better than Tony Bones' for his work.

As for your point about 19" wheels, however, my answer is that I wouldn't use them, because they crack. I don't need to know why.

I didn't make a point about 19" wheels, never mentioned them.

Anyway cut to the chase. The general consensus, on this forum anyway, is that 19" E89 OEM wheels can crack and it's because of run flats in most people's opinion, which I think you know. It's also opinion that non run flats serve 2 purposes; To help prevent cracking and, and I can varify this, give a much better ride. I don't think you are without common sense and it's not rocket science to agree with the above based on common sense. You seem to have been round the houses wanting proof of this that and the other when there is none. So if you want 19's, don't deny yourself, fit them with non run flats, stop fretting about it, and enjoy your car.

[Twin Turbo]

Going from memory - but need to re-check my settings

Front Camber -0.5
Front Toe 0.05
Rear Camber -2.5
Rear Toe 0

[dario]

Going from memory - but need to re-check my settings

Front Camber -0.5
Front Toe 0.05ard set
Rear Camber -2.5
Rear Toe 0

Out of interest, Do you know the standard numbers?

[Smartbear]

My rear camber is 1.5degrees to save the inner edge of the tyres a little
Rob

[dario]

My rear camber is 1.5degrees to save the inner edge of the tyres a little
Rob

Thanks for posting Smartbear, how long has the car been set up like this? Do you notice the change in handling? And finally how is the tyre wear now as opposed to before?

[Smartbear]

My rear camber is 1.5degrees to save the inner edge of the tyres a little
Rob

Thanks for posting Smartbear, how long has the car been set up like this? Do you notice the change in handling? And finally how is the tyre wear now as opposed to before?

I took my car in for a geo set up (hunter equipment) with the intention of taking some negative camber away-I realise most excessive inner edge wear is tracking originated & not camber but I think it contributes to it.
My car was on 20k miles & when checked it was already on 1.5degrees, the operator said he recommended less camber for the same reasons. (Standard setting is 2.5degrees I think)
I don't track my car or drive it particularly hard on the road, I won't miss the reduced camber
Rob

[dario]

My rear camber is 1.5degrees to save the inner edge of the tyres a little
Rob

Thanks for posting Smartbear, how long has the car been set up like this? Do you notice the change in handling? And finally how is the tyre wear now as opposed to before?

I took my car in for a geo set up (hunter equipment) with the intention of taking some negative camber away-I realise most excessive inner edge wear is tracking originated & not camber but I think it contributes to it.
My car was on 20k miles & when checked it was already on 1.5degrees, the operator said he recommended less camber for the same reasons. (Standard setting is 2.5degrees I think)
I don't track my car or drive it particularly hard on the road, I won't miss the reduced camber
Rob

Cheers

[Busterboo]

The Hunter standard Rear Camber for the E89 with Adaptive M Suspension on 18" wheels is 2 degrees 20', with 10' Toe.