[zebedee]

I have just purchased a 2005 320d SE with standard wheels that I am currently getting refurbished (think the PO must have enjoyed kerbing the wheels).

I have been to a couple of local tyre shops and enquired about changing from RFs to standard tyres and they all agree it is a good idea as I am looking more for comfort and economy than all out performance (although after reading here I do intend to have it ReMapped).

But a tyre fitting shop I contacted today to also enquire getting Winter tyres (due to 2inches of snow today) did not advise changing from RFs for the following reason............he says that RFs have a stiffer side wall and as such the suspension is made a little softer and by putting on NON RFs the ride could be TOO soft and dangerous.

I have read many threads on here over the last few days but have not seen anybody mention that it may be dangerous to change from RFs.

Does anybody have any comments on this, taking into account that age wise I am way past the boy racer stage but do like to enjoy the performance in a straight line, but without going stupidly over the speed limit as my job involves having a driving licence.

[dxb335d]

I dont think you will find it soft and dangerous. More pliant, therefore safer in Effect.

This is what I found with my Sport suspensioned E92.

[doughboy]

Just ill-informed tyre centre staff.

The ride will be less crashy without runflats, but its is proposterous to say it could be dangerous.

In fact, any tyre centre that employs someone that understands so little about tyres and suspension should be avoided IMO....

Even BMW's onw internal guidelines recommend fitting non RFTs if you find the ride too hard.

From your needs I'd say the Falken FK452 would be a good bet.

[zebedee]

Thanks for your prompt replies, and for putting my mind at rest....NON RFs it is then.

I have been a long time member of another Forum site for a type of motorbike I own, and find the information on these sites much more informative and honest than going to stealers who may only have their best interests at heart.

[MOB]

Originally Posted by doughboy

Just ill-informed tyre centre staff.

The ride will be less crashy without runflats, but its is proposterous to say it could be dangerous.

In fact, any tyre centre that employs someone that understands so little about tyres and suspension should be avoided IMO....

Even BMW's onw internal guidelines recommend fitting non RFTs if you find the ride too hard.

+1

I had to enquire with around 5 tyre fitters before someone would agree to fit the non-RFT's

[HighlandPete]

Originally Posted by zebedee

But a tyre fitting shop I contacted today to also enquire getting Winter tyres (due to 2inches of snow today) did not advise changing from RFs for the following reason............he says that RFs have a stiffer side wall and as such the suspension is made a little softer and by putting on NON RFs the ride could be TOO soft and dangerous.

I have read many threads on here over the last few days but have not seen anybody mention that it may be dangerous to change from RFs.

Does anybody have any comments on this.

OK, I've looked at this extensively and can speak from running a 'soft' SE E91.

I am aware of guys going back to run-flats as the cars are too soft on non run-flats. One tyre specialist and BMW driver himself had a customer in a 3-series which was changed to same tyre spec/brand in non run-flat. The driver was sure the car was dangerous, the specialist had a drive and brought it straight back in and fitted a set of run-flats again, as he was sure the car was lethal on the softer tyres. Extreme you may say, but I know the specialist and he has too many years with cars to just be reactive.

The latest LCI cars are softer anyway, so you may need a pretty stiff non run-flat alternative to give the right dynamics. A lot will also depend on what wheel sizes you are running and what characteristics the run-flat has in that size, ahead of any change.

I personally could not live with run-flat tyre behaviour, was willing to experiment and go a further stage if necessary. I changed from the infamous Bridgestone Potenza (17") on my car, to the Goodyear F1 GS-3D and improved my ride quality and rid the car of strange dynamics. BUT, as it is on standard suspension, was now under damped. Could not thump out ridges and hollows in one thump, had a sort of 'one and a bit' reaction. Long undulations were also under damped, a bit too much lift and fall. It was to a degree already there on the RFTs, but completely unmasked with normal rubber. I fitted Koni FSD dampers and that sorted the problem, softer on the smaller bumps and imperfections and good control on ridges, hollows and longer undulations. The car is even better on Falken FK 452 tyres, they just work in total harmony with the car's modified suspension setup, seem to enhance the sum of the parts.

I'm aware that most M-sport setups when changed get a well balanced result, softens the ride, reduces the inherent harshness without much loss of composure, just lose an edge of turn in, which some love so much.

HighlandPete

[doughboy]

Originally Posted by HighlandPete

The driver was sure the car was dangerous, the specialist had a drive and brought it straight back in and fitted a set of run-flats again, as he was sure the car was lethal on the softer tyres.

No offence intended, but it is ridiculous to suggest this could be attributable to the softer sidewalls of non RFTs. For a start, lower spec 3ers don't come with RFTs (cost option) and they have no suspension components changed whatsoever if you don't spec RFTs.

Remember this is soft ES suspension, with small 16" wheels on soft larger profiles 205/55/16 - the worst case scenario and its available from the factory without RFTs

And BMWs own internal guidelines recommed they source and fit non RFTs where customers complain of ride harshness.

Long undulations were also under damped, a bit to much lift and fall. It was to a degree already there on the RFTs, but completely unmasked with normal rubber.

Tyrewall stiffness can have no effect on the inherent underdamping that causes slowspeed lift and fall over undulations, that is solely down to damping/springs and vehicle weight. The 'spring' effect of any tyre has no damping to speak of so any compression is released immediately and cannot alter slow speed vehicel damping IMO.

However, tyrewall stiffness will affect the high speed upwards wheel movement resulting from sharp bumps as it cannot absorb these shocks as a soft tyre can, thus it will actually require stiffer damping to slow the faster upwards moving wheel and heavier RFT tyre, of course this would cause further harshness in the vehicle so it is not done.

Thus the 'double bounce' is a result of this underdamping as the dampers cannot control this rapid upwards movement so the wheel rises too high, before returning to the ground only to bounce back off the ground partially as again its stiffness cannot absorb the impact energy. Further 'slop' in the mounting bushes etc only worsen the 'wobble' in various directions as a ridge is struck.

Changing to non RFTs, in my experience with pre and post LCI cars almost cured the double bounce in all but the most severe potholes.

[HighlandPete]

Originally Posted by doughboy

No offence intended, but it is ridiculous to suggest this could be attributable to the softer sidewalls of non RFTs. For a start, lower spec 3ers don't come with RFTs (cost option) and they have no suspension components changed whatsoever if you don't spec RFTs.

Remember this is soft ES suspension, with small 16" wheels on soft larger profiles 205/55/16 - the worst case scenario and its available from the factory without RFTs

I'm with you on the reasoning, used it myself in other discussions. Also which wheel size is the car 'designed' to run on, when options are offered?

On the specific car with issues, all I'm doing is reporting the example of one user's experience I have discussed 'face to face' with a very experienced tyre specialist. He assured me the car was put back to a surefooted drive with run-flats refitted. BTW, he is no fan of run-flats.

Originally Posted by doughboy

Tyrewall stiffness can have no effect on the inherent underdamping that causes slowspeed lift and fall over undulations, that is solely down to damping/springs and vehicle weight. The 'spring' effect of any tyre has no damping to speak of so any compression is released immediately and cannot alter slow speed vehicel damping IMO..

I'm not going to say more than I know how my car responds over roads I drive, with and without run-flats, and in comparison wth the Koni dampers on both the same run-flats and non run-flat tyres, as I have two 17" wheel sets.

I assure you there was a difference in damping feel and response over undulations with the different tyres fitted to my car with OEM dampers. As I say, it was already there but completely unmasked on non run-flats. It is all subtle stuff, but 40 years of seat of the pants experience does tell you a bit. I personally suspect the damper valving is in conflict, or there is a suspension frequency issue with softer rubber.

I also am aware of other 3/5 series drivers who find the SE suspension really too soft when running non run-flats.

HighlandPete

[doughboy]

Fair comment.

There's a minefield of counter reactive forces going on under the car.....the combinations and results are endless.

I'm keen to know which suspension kit you've fitted, I'm in a tourer too.

[milesr3]

Originally Posted by HighlandPete

I also am aware of other 3/5 series drivers who find the SE suspension really too soft when running non run-flats.

I put non-RFTs on my pre-LCI 535d SE (17" wheel) and I don't find the suspension too soft. The non-RFTs have removed all the harshness, skittishness and following cambers and the car is much more sure-footed on the new tyres. I don't find the ride soft at all - if anything it is still too firm for me on bumpy surfaces, but then I did absolutely hate the 320d sport on 18" RFTs I had as a loan car last week, so I may be less tolerant of a harsh ride than others.

I have heard of one other person who didn't get on with non-RFTs on an LCI 5er, but they changed the dampers from build date 03/2006 onwards on the five so it could be that they were compromised for RFTs as I understand the E60 was originally designed for normal rubber.

The only weirdness I've noticed with non-RFTs was a little delay on turn-in and I could sometimes feel the car moving about a little on the sidewalls in a straight line at speed in a crosswind. I've since discovered that my tyre pressure gauge was inaccurate though and I was running my Falken ZE912s at less than the standard pressures. Now they're up to a full 36/41psi it feels no different to RFTs.

Otherwise I'm a total convert to non-RFTs.

[HighlandPete]

Originally Posted by doughboy

Fair comment.

There's a minefield of counter reactive forces going on under the car.....the combinations and results are endless.

I'm keen to know which suspension kit you've fitted, I'm in a tourer too.

I'll definitely agree on the minefield.

For me, I simply wasn't happy on the Bridgestones, was about to rid myself of an 8-month old car, as the ride up here was so varied each time I went out. Ambient temperature, wet roads, different surfaces made my car have a jekyll and hyde nature. My wife hated it and I thought I'd lost the plot after my E39 540i.

I tried getting a BMW solution as my garage had two other disappointed users and one wife refusing to drive the car, as she declared it was dangerous. A technical meeting didn't get anywhere, and I got Bridgestone involved and had an engineer come up and ride with me. He really believed the damping was in conflict and my day to day driving was pushing the boundatries of RFTs. So stuck with a car that didn't work, or sell it and get a Merc. I decided the cheapest solution was to experiment and get some more wheels and try a wet weather biased performance tyre. Hence the Goodyear F1.

Was part way there, I was still hoping for a run-flat solution, due to no spare in a remote environment. So looked to change dampers. The Koni FSD was just coming into the market and getting good reviews particularly from VW users. Tirerack had tested some on a BMW and their report and speaking with one of their guys, got a nod of approval. Had a discussion with Koni and after one of their engineers responding to my questions, including the fact they believed BMW's damping was unbalanced front to back, went for the first set of FSDs to be fitted on an E91 in the UK. Got the car I wanted on normal rubber, but still had issues with the run-flat set, running at less than 12-degrees ambient and in wet running, where they stiffen up too much to be predictable.

I replaced the Goodyear F1's with the Falken 452, as Goodyear didn't thave the exact tyre sizes in the F1 asymmetric, which would have been my first choice. The Falkens just work so well with the suspension and steering. It is as if they just complete the circle and make the whole set up work in better harmony. The car is now very fluid in the way it drives, totally predictable. I'm sure some would say too soft, but I'm a guy who believes that a fast drive, doesn't need to be rock hard.

HighlandPete

[HighlandPete]

Originally Posted by milesr3

I put non-RFTs on my pre-LCI 535d SE (17" wheel) and I don't find the suspension too soft. The non-RFTs have removed all the harshness, skittishness and following cambers and the car is much more sure-footed on the new tyres. I don't find the ride soft at all - if anything it is still too firm for me on bumpy surfaces, but then I did absolutely hate the 320d sport on 18" RFTs I had as a loan car last week, so I may be less tolerant of a harsh ride than others.

I have heard of one other person who didn't get on with non-RFTs on an LCI 5er, but they changed the dampers from build date 03/2006 onwards on the five so it could be that they were compromised for RFTs as I understand the E60 was originally designed for normal rubber.

Same reports/feedback for me, pre LCI SE ride is greatly improved, transforms the cars. Post LCI 5's on the revised SE suspension, seem to be more tyre sensitive, some report losing the planted feel and generally being too soft.

M-sport cars seem to get the good reports throughout the model range, pre and post LCI.

HighlandPete

[milesr3]

Originally Posted by HighlandPete

I thought I'd lost the plot after my E39 540i.

Sadly I think it's BMW that lost the plot after the E39.

Moving from E39 to E60 myself I can't begin to understand why they developed an all alloy suspension setup, which had a truly magic-carpet ride and then ruined it by nailing runflat tyres to it.

I guess at least the M-cars have managed to avoid RFTs and all the compromises in suspension setup that come with them, so BMW can still get it right.

[HighlandPete]

Originally Posted by zebedee

But a tyre fitting shop I contacted today to also enquire getting Winter tyres (due to 2inches of snow today) did not advise changing from RFs for the following reason............he says that RFs have a stiffer side wall and as such the suspension is made a little softer and by putting on NON RFs the ride could be TOO soft and dangerous..

Sorry to the OP, but I think we went off on a tangent.

The comment on dangerous... if you have read my comments, I can assure you that at no time was my car giving the feeling of being dangerous on non run-flat tyres. Could be honed to run better, but definitely not dangerous. If anything I'd say running the RFTs was where the feeling of danger could apply in some conditions.

HighlandPete

[HighlandPete]

Originally Posted by milesr3

Sadly I think it's BMW that lost the plot after the E39.

I was hoping to go to a 535d touring after the E39 touring (M-tech) suspension, but the M-sport example I tested and was going to buy, was rock hard and far too harsh. So waited for the E91 to come along, as it is really big enough for our needs these days. Just need to try an F10 to see if BMW have really got back in their stride.

HighlandPete

[zebedee]

HighlandPete

As the OP, no problem with things going a bit off subject, just glad I have stimulated some comments.

I will definitely give the non RFs a go and see what happens.

I only drove the car for two days before getting the wheels off for refurbishmnet due to some scuffs, but it felt very skittish on town bumpy roads, and tended to tramline in grooves, but then all four tyre were getting close to their wear marks.

[milesr3]

The whole 'RFTs are much safer' argument is very narrow: RFTs allow you to avoid changing a tyre at the side of the road and potentially avoid losing control if you get a rapid deflation but the tyre remains intact. In 23 year's of driving, I've had one puncture and never had a blow-out <runs to touch wood>.

Outside of these narrow criteria my experience of Bridgestone RFTs has been that the stiff sidewalls cause the tyre to lose contact with the road over bumps, tramline badly and lose grip less progressively with less feel than a normal tyre - particularly in cold/damp conditions where they work particularly badly.

You also can't see when they're flat. My Dad was driving round with 10psi less than the std pressures in his 535d because they didn't look like they needed pumping up and because they'd all lost pressure together hadn't triggered the tyre pressure warning.

They are also more prone to causing cracked rims and increased wear and tear on other suspension components, which you can't see.

As long as you fit a decent non-RFT tyre and keep it inflated then it will work better and thus be safer than a RFT.

[Animalfreeride]

Originally Posted by zebedee

I have just purchased a 2005 320d SE with standard wheels that I am currently getting refurbished (think the PO must have enjoyed kerbing the wheels).

I have been to a couple of local tyre shops and enquired about changing from RFs to standard tyres and they all agree it is a good idea as I am looking more for comfort and economy than all out performance (although after reading here I do intend to have it ReMapped).

But a tyre fitting shop I contacted today to also enquire getting Winter tyres (due to 2inches of snow today) did not advise changing from RFs for the following reason............he says that RFs have a stiffer side wall and as such the suspension is made a little softer and by putting on NON RFs the ride could be TOO soft and dangerous.

I have read many threads on here over the last few days but have not seen anybody mention that it may be dangerous to change from RFs.

Does anybody have any comments on this, taking into account that age wise I am way past the boy racer stage but do like to enjoy the performance in a straight line, but without going stupidly over the speed limit as my job involves having a driving licence.

I know exactly the predicament you are in. Funnily enough I took the plunge only today & ditched the RFT's. This was only after sorting out a nightmare situation with Swiftcover who wouldn't give me a straight answer about covering non-RFT.

I opted for Continental Sport Contact 3. However the garage owner, who is a friend of a friend, recommended that I keep RFT on the vehicle as the handling is affected. To be fair this was not based on his personal opinion, but views & opinions he has heard from other customers. This was also mirrored by BMW who I recently contacted & gave me a list of reasons to keep RFT. However BMW are hardly going to admit that RFT's are shite & are linked to alloys cracking.

My motive for change was primarily comfort, followed by cost & hopefully reduce the risk of a costly alloy wheel replacement.

It's really too early to give my opinion of the the Conti's but they have definately "ironed out" the bumps & are less noisy. The steering feels lighter but to be honest I have literally only driven 15 miles, it was raining & is more than likely attributed to the tyres not having had chance to "bed in".

I have found this thread an interesting read & just hope I haven't made a costly mistake. I was under the impression that all 335's have Msport suspension?

I will keep you posted over the Conti's.

BTW the garage concerned was Tyremarks of Tavistock, Devon. I was relieved that there were no apparent cracks to any of the alloys (touch wood). The owner Mark was really helpful & looked after my car whilst in his care. Good job Mark!

[zebedee]

Animalfreeride, you seem to be changing for the same reasons as me so your opinion will be appreciated, although my wheels should be back from refurbishment tomorrow so hopefully getting tyres fitted this weekend.

I had not heard that RFs could damage the wheels, but after 54k miles that mine have done the place Im having the wheels beadblasted and powder coated at did not mention anything about any damage to the wheels when I spoke to them today, so fingers crossed.

[RichJ]

Originally Posted by Animalfreeride

I know exactly the predicament you are in. Funnily enough I took the plunge only today & ditched the RFT's. This was only after sorting out a nightmare situation with Swiftcover who wouldn't give me a straight answer about covering non-RFT.

I opted for Continental Sport Contact 3. However the garage owner, who is a friend of a friend, recommended that I keep RFT on the vehicle as the handling is affected. To be fair this was not based on his personal opinion, but views & opinions he has heard from other customers. This was also mirrored by BMW who I recently contacted & gave me a list of reasons to keep RFT. However BMW are hardly going to admit that RFT's are shite & are linked to alloys cracking.

My motive for change was primarily comfort, followed by cost & hopefully reduce the risk of a costly alloy wheel replacement.

It's really too early to give my opinion of the the Conti's but they have definately "ironed out" the bumps & are less noisy. The steering feels lighter but to be honest I have literally only driven 15 miles, it was raining & is more than likely attributed to the tyres not having had chance to "bed in".

I have found this thread an interesting read & just hope I haven't made a costly mistake. I was under the impression that all 335's have Msport suspension?

I will keep you posted over the Conti's.

BTW the garage concerned was Tyremarks of Tavistock, Devon. I was relieved that there were no apparent cracks to any of the alloys (touch wood). The owner Mark was really helpful & looked after my car whilst in his care. Good job Mark!

I will be really interested to hear your views/experiences of changing to non run flat continentals as i was thinking of doing exactly the same!! Keep us posted.

[Jules6]

I've just taken the plunge and ordered Contisport 3s for my E92 MSport.
I shall also get a Continental Comfort Kit 12V compressor and goo.
Pretty much what my E46 M3 had.

I shall review next week after they have been fitted. I hope it's the right decision.

[zebedee]

I think I may have found my answer to RFs or NON RFs.

I am currently trialling the new electro magnetic hover system which is showing good results.....I wonder when this will be an optional extra.