[moldcad]

Exactly - and depending on where exactly AlpsRider is getting the rub, replacing my current 235/35 tires with 245/30 might be necessary if I want to lower the car. It's a pity I was talked out of this idea when it was still possible to order 245/30 tires without any additional expense - yet I do admit I wasn't very determined to go with this modification of the 'Dinan specs' because such a low profile would mean much harsher ride which I was trying to avoid...

This is why it's so important that AlpsRider specifies in more details when and where exactly he is getting his 235/35 rub; if it's due to the tire radius increasing negative camber will not help, and 245/30 might prove necessary. If on the other hand the rubbing is more related with the current tire width - camber and/or spacer might be the solution...

Piotr

[AlpsRider]

I checked out the 245/30/19 size, it looks like the tire sidewall height would be 6mm less than the rear 265/30/19 or an overall diameter difference of 12mm. For some people 12mm diameter difference looks weird on the car, some people don't notice it. I'm not sure how it would affect handling, traction control, ABS etc.

I think the combo 235/35/19 and 265/30/19 is about as close as can be found for a 19" wheel diameter match for this car.

Keep in mind that the Dinan springs "allegedly" lowers the front by 1/2" and is 10% stiffer, the replaced bump stops are shorter to allow more suspension compression to make up for the lowering. I've read that without the shorter bump stops you're just asking for the shocks to fail early. I'm happy overall with my car's setup, the rear end is dropped 1" and is 30% stiffer which feels better to me. The original setup always felt like the ass end was up in the air. However at high speed over bumps and cornering the shocks don't have enough dampening for the stiffer springs. It is nothing dangerous, but there is a bit more bounce than I would prefer. I am a perfectionist when it comes to the way my car handles though, I probably need a "P" car to shut me up. On this car, adjustable coil-overs is probably the cure. Alternatively springs that are less stiff in the back might help the dampening issue. Personally I wouldn't consider springs that are taller in the back than the front.

A slight fender roll may take care of the rubbing problem with my car. It happens when the wheel is turned fairly sharp when cornering hard with big bumps in the road. I don't hear it rub so it is difficult to pinpoint the situation exactly.

Here is a snapshot of what the scuff looks like, this is about as bad as it gets. Sometimes it's just a faint charcoal tint. It happens at the very top of the front fender on the inside roll lip. You can't see the scuff from the outside. I have to look under the fender well upside down to see it. It can happen on either side, but it seems to happen on the passenger side front much more often, in fact it's only happened on the driver's side a couple of times, which indicates that it is very close to clearing. So far there hasn't been any permanent damage. The scuff results in a skid mark that comes right off with a soapy sponge. Over time it might affect the paint, as I said it is not visible from the outside of the car.
It's difficult to say what the cure would be besides a fender roll or smaller tires. IMHO this car needs at least 235s on the front. The M2 has 245s in the front and 265s rear.

[moldcad]

Doesn't look encouraging at all

Thanks for your time and effort, AlpsRider. What a pity you didn't post this picture earlier on, though. I comtemplated going 245/30 front even before I settled for the 235/35! And a front wheel with slightly smaller diameter than the rear - even if noticeable - is not weird looking at all on an RWD car... Plus, the rear with be eaten up pretty quick, so the difference will diminish in time.

Piotr

PS. Guys - do you think some aggressive negative camber would help clear the current tire and the fender lip? I personally don't think so, as the rub happens with wheels turned - but my experience in this kind of mods is zero, so I'd do with your sound advise.

[moldcad]

Considering that radius increase with the current (235/35) tire over the OEM one is just 5mm:

https://www.wheel-size.com/calc/?whe...cl=30mm&sr=0mm

- it really seems strange that the 235/35 would rub on the circumference... I'd say the Dinan bump-stops are probably just a tad too short; anyone knows how they compare in length with the E36 M3's front ones?

@AlpsRider - did you contact Dinan about the rubbing?

Piotr

[moldcad]

I really don't know how to proceed now May I kindly ask you AlpsRider to help the community further by trying to pin-point the portion of your 235/35 tires which actually rubs? Even though from your picture it looks like it's the circumference, it would help tremendously to know for sure - and whether there is any chance at all to solve the problem with more negative camber (which could only be the case if the tire rubs with the outer edge rather than central part of its tread)...

Perhaps you could apply some color substance over the fender lip, and see where exactly on the tire its traces are left after inducing the rub?

Piotr

[AlpsRider]

The rubbing doesn't happen often. There are no marks on my tires because it is a minor rub.
The top of the tire is 5 mm closer to the fender and also pokes out 6.3 mm more. Take into account that these are monster tires, I wouldn't doubt if those calculator figures are too conservative. I'm not sure that the type of rubbing I'm getting is due to the bump stops since it doesn't have to be at full compression to rub.

[moldcad]

People are running 18x8.5 ET35 235/40 wheels at the front, and claim there is no rubbing.
https://www.wheel-size.com/calc/?whe...cl=50mm&sr=0mm

Something strange is going on with yours; you would help me tremendously if you found out which region of the tire is rubbing (perhaps using the technique of applying some dye to the inner lip). As I said: I need to know whether I must use 245/30 instead, or apply more negative camber with the current tires...

I'm aware it'd take some time and effort, but I'm sure others would appreciate this information as well. Many people tend to trust companies like Dinan and would like to use their specs - now they must feel just as lost as myself. I certainly hope you will help us; Thanks in advance

Piotr

[AlpsRider]

There is nothing strange going on with my car, it is lowered. I don't have the time to trouble shoot for you right now. The best of luck to you.

[moldcad]

Well - given your wheels and lowering kit are of the same origin (Dinan) - it IS very strange.

Thank you very much, anyway.

Piotr

[moldcad]

Also what is strange to me - and even sad - is how some people don't want to hurt their own ego by admitting the choice they made wasn't necessarily the best one. Even if this could help not only others (by avoiding the same mistake), but also others and themselves (by trying to find a solution that would work for all in the same trouble)...

Since the rubbing occurs with the wheels turned and the suspension squeezed, and knowing how the camber increases with both - it's safe to conclude it's the outer tire edge that gets in contact with the fender lip. Very unscientific and rough calculation shows that with the negative camber increased to -5 degrees, the outer edge of 235/35R19 tire will go up more than 12 mm from its position at zero camber...

Unfortunately, only more scientific calculations or an experiment will answer the all important question whether increasing the "base" negative camber (so that it's not zero but say -2 deg with straight wheels and suspension relaxed) will increase this elevation even more, or - if the said 12mm happens to be the maximum elevation value - decrease it, by changing the camber from the mentioned -5deg to -7deg (in turned and squashed position).

Anyone interested in helping me answer this question? Otherwise the only safe option for people who followed the 'Dinan specs' of wheels/tires and would like to lower their cars is adopting the lower 245/30 tires. At the cost of vastly increased ride harshness

Piotr

[Bee Pee]

-5 deg
-7 deg
-2 deg

You are quoting very large camber angles there.

Stock suspension front camber is somewhere between -0.3 to -0.5 deg.

I'm lowered with F8X arms and still only manage running -2deg upfront.

Check yr sums - reads to me like you are missing a decimal point somewhere....

[moldcad]

Just imagine the camber angle of a left front wheel which is:

- turned fully to the right
- on a suspension which is fully compressed
- on a car which is lowered

So no, I didn't miss a decimal point.

Piotr

[Anthony235]

Geez what's going on in this thread?! It's not that complicated. haha.

Run less aggressive offset, run a narrower wheel, run a narrower tire, roll/pull fender, run more camber. Pick one or any combination of those to fix the issue while keeping in mind inner fender clearance.

You can run a 18x9.5 +25 with a 265 tire up front without issue using a combination of the above.

[AlpsRider]

Originally Posted by Anthony235

Geez what's going on in this thread?! It's not that complicated. haha.

Run less aggressive offset, run a narrower wheel, run a narrower tire, roll/pull fender, run more camber. Pick one or any combination of those to fix the issue while keeping in mind inner fender clearance.

You can run a 18x9.5 +25 with a 265 tire up front without issue using a combination of the above.

Exactly.

[AlpsRider]

Originally Posted by moldcad

Also what is strange to me - and even sad - is how some people don't want to hurt their own ego by admitting the choice they made wasn't necessarily the best one. Even if this could help not only others (by avoiding the same mistake), but also others and themselves (by trying to find a solution that would work for all in the same trouble)...

I don't know what your problem is, but you need to take a chill pill.

[Bee Pee]

Originally Posted by moldcad

Just imagine the camber angle of a left front wheel which is:

- turned fully to the right
- on a suspension which is fully compressed
- on a car which is lowered

So no, I didn't miss a decimal point.

Piotr

I don't need to imagine any of the above as I have 1st hand experience as you well know already - from our PM exchanges on a different forum - as follows:-

Firstly - I've been running lowered springs, F8X arms 18" x 8" et34mm with 225/40/18 MPSS upfront for ~ 3 years and ZERO rub.

Secondly - I have driven AC Schnitzer F2x cars with their sports and RS suspension set-ups with ACS 8.5" et 43mm wheel/tyre combo with larger rolling radii than your tyres and outer faces which poke out more than yr Dinan spec wheels - on bumpy UK roads and on TD's - ZERO rub.

IMHO, you are over thinking all of this - as mentioned already - chillax.

Your car already looks trick with its new wheels/tyres, you mentioned somewhere about having neck/back issues and are unsure about what to spend your money next.

Save your cash and if your neck/spine is fine with car just now - leave as-is and enjoy it.

[moldcad]

BP, I do appreciate both your vast experience and your patience with me. However it is not me who is claiming that wheels & tires with specs Dinan recommends rub when the car is lowered on Dinan springs, and we have no reasons not to believe it. All I'm after is to find a remedy, as I'd like to drop my car as well...

Cheers
Piotr

[Bee Pee]

Ok - avoid Dinan products is my advice.

As we have discussed already there's plenty more options out there that will give you minimal drop without fender/rubber contact.

[AlpsRider]

Originally Posted by moldcad

BP, I do appreciate both your vast experience and your patience with me. However it is not me who is claiming that wheels & tires with specs Dinan recommends rub when the car is lowered on Dinan springs, and we have no reasons not to believe it. All I'm after is to find a remedy, as I'd like to drop my car as well...

Cheers
Piotr

One of the recommended tires for the Dinan spec wheels is the MPSS.

My tire is the MPS4S, this is not the same tire and I've made it abundantly clear.

Quote from the Dinan wheel website:
-----------------
"Recommended Tire: Michelin Pilot Super Sport or P-Zero Corsa – 235/35-19
(For other tires see note below)

NOTE – If using a tire other than the recommended tire: The physical dimensions of different tire manufacturer's products may vary for a given tire size. In some cases minor trimming of the fender well lip may be required due to vehicle production tolerance variations."
-------------------

* They make no guarantees that even the stock non-lowered suspension with the MPSS tire won't rub without modifications, now throw in the MPS4S...

It makes sense that given the already tight tolerances that adding lowering springs could cause even more issues, I knew all of this before I ordered anything.

I spent my money and took a chance. It cost me $550. to add the springs including installation. I'm happy with the handling improvement. I may eventually get the fender lip rolled in a bit, it wouldn't be visible from the outside. If I decide to remove the Dinan springs for whatever reason, so what, I've lost $550. I can sell the springs in the classifieds if it ever came to that. I'm done here.

[Anthony235]

Originally Posted by AlpsRider

I may eventually get the fender lip rolled in a bit, it wouldn't be visible from the outside..

Alps, just a heads up that any fender roll that flattens the inner lip will be also give you a slight pull on the fender that is noticeable. You will probably be the only one that notices it since you're aware of the pull. I've had many fenders rolled and this has always been the case.

Luckily on our cars the BMW lip and fender liner tabs don't meet at the edge of the lip so it's very easy to get a clean roll on this car. No ripples or cutting of fender liner.

Just wanted you to be aware

[AlpsRider]

Thanks for the heads up

[moldcad]

Originally Posted by moldcad

Just imagine the camber angle of a left front wheel which is:

- turned fully to the right
- on a suspension which is fully compressed
- on a car which is lowered

Actually, even more illustrative to my rough estimation of how much the tire edge elevates would be the inner (relative to the direction of turning) wheel camber as it increases the most with turning the wheels (though this varies with different suspension designs). Anyone interested please try to find some good read and relevant pictures of the front suspension geometry (also when turned and squeezed) before you advise me to take some pill, or criticize me for a fundamental error in my calculations (like missing the decimal point in my numbers ).

You will then understand that the problem I'm trying to define & solve is far beyond the usual reservations Dinan - and all other providers of oversized wheel fitments - always make about a possible necessity of doing a little 'bodywork' (like rolling fender lips) when a specific tire model is used. BTW, it was stated in this very thread that Michelin PS4S tires (which I also have) are actually narrower than MPSS. But that's not the point here, as out of the 'Dinan specs' wheels it's the more aggressive rear wheels that might rub against the fenders because of wheel offset & tire width (easily solvable with adjustable camber though) - in the case of front wheels, it's the tires height which is at fault.

And last but not least: I may be lacking 1st-hand experience in modding BMW cars many of you guys have, but it so happens that both my MSC and DSC theses some 40 and then 35 years ago were on car dynamics (and in particular: tire-road surface contact as non-holonomial type of Boundary Condition). I built a detailed, comprehensive mathematical model of a car in motion, including of course a very precise description of the suspension kinetics, and by solving it numerically I was getting the car's response to all relevant inputs (propelling torque, braking forces, steering angle & force, inertia & gravity - but also aero drag & wind forces, road elevation & inclination angles, etc.). BTW later on - when personal computing power in number crunching and - above all - graphics capabilities became more like what we have access to today, I developed my model further so it became quite a capable graphical car simulator... And as to my practical background: I have 46 years of driving experience, including participation in sport events (something known to Europeans as WRC-type rallies, for which I heavily modded my cars - just not BMW at that time)... But I'm digressing; I only mentioned my background to deny your accusation that I'm making things more complicated that they really are: I'm not, my Friends - quite the opposite actually, believe me - so would you please stop your ad persona attacks?!

Thanks again for all your input so far, and waiting for more of ad meritum ones

Piotr