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my experience with the 15" 16" &17 rims and conclusions..

Discussion in 'Z3 Roadster & Coupé' started by joey, Feb 9, 2014.

  1. joey

    joey Zorg Addict
    British Zeds The M44 Massive

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    so I just thought I would relay all of this as I now have driven this car with 15" 16" and 17" rims...an interesting experiment with some clear conclusions...its all been a bit "goldilocks"

    when I bough the car it had the 15" pepper-pots on, I never like the look of them and to be honest i felt the 205/60/15 lacked grip and responsiveness and there was a general lack of feedback from the tyres, I tried some decent priced part worn's (firestones) with 6mm of tread to establish if it was wheel size or rubber that was the issue, although with these tyres the grip was better I still felt the car lacked "sharpness" and the rear was prone to stepping out without warning....this compared to other 1.9s I had test driven before buying this one.

    so I fitted style 18 5 spoke alloys with 17" rims..225/45/17 front and 245/40/17 rears...

    what a difference! some good, and some really bad things ..grip was phenomenal ! despite my best efforts the back would not step out at all and the car cornered as if glued to the road...however I had several problems straight after fitting these wheels despite them being checked and confirmed straight and balanced by a tyre guy I trust, and double checked elsewhere free of charge (just in case)..steering shake,awful and unpredictable tram-lining and I have to admit the car lost some of its "pep" acceleration was decreased as was mpg by about 10% I also had to renew the front discs,callipers and pads due to a binding calliper...a coincidence maybe and not entirely unexpected on a 15 yr old car, but heavier wheels means more work for these components so I am inclined to think that these issues were linked..I could not cope with the unpredictable nature of the tram-lining..even after fitting powerflex wishbone bushes, and the ride was generally harsh and suffered heavier steering and a slight increase in understeer.

    yesterday fitted the 16" with conti contact sport all around sizes, 225/50/16,

    tramlining and steering shake all completely gone, grip is unaffected and inspires confidence, the feedback from the tyres is great and the car is back to it's peppy drivable self..it feels less skittish at all speeds and even on the worse roads goes where its told...handling is neutral bordering on very slight understeer but it corrects itself with some right boot when cornering..all in all I am much happier.

    in conclusion I would not advise anyone to go bigger than 16" on a 1.9

    for optimum performance in all areas any bigger is a compromise between looks and drivability, especially on an older car where ball joints and bushes and braking components may be on their last 15% of useful life..it may highlight all even cause problems.

    I will be thinking more carefully in future about the potential effects of changing things on the car.
     
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  2. zedonist

    zedonist Guest

    Good write up Joey, I think it possibly comes down to all things being equal, i.e. wheel, tyre size, suspension etc all matching, when this occurs it is a match made in heaven, upset the balance and the smile disappears quite quickly. I am running 18's with 255 rubber at the rear and 225 at the front, that said i have uprated the suspension and ARB's and she handles like a dream, so you can have larger wider wheels, but at a price. I concur i would not go any larger than 225 at the front.

    I think what a lot of people ignore is that these cars are rear wheel drive, and most people come to them following years of front wheel drive cars. The fact is the front wheels on a Z3 are free wheeling, no torque applied, so are being pushed as a consequence will suffer bump steer, more pronounced with bigger wider wheels (Stiffer sidewalls and wider track etc). The addition of powerflex bushes just goes to amplify this problem, as you have witnessed. On a front wheel drive car the rear end is being dragged by the fronts, so you tend to feel the rear track the road instead and do not see the effects of tramlining, the fronts go where you point them due to the torque going through them.
     
  3. joey

    joey Zorg Addict
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    cheers Rich, I hope it helps someone else planning these changes in the future..

    I think your wheel and tyre sizes have been carefully considered and matched with your suspension components perfectly hence your car handles as well as it does,IMO this need to be done and your observation about the RWD aspect of the car and its effects on handling is spot on re the bump steer and tramlining especially,I have learnt this at my cost!

    but it was a valuable lesson,

    if you intend to keep all of the steering and suspension components stock on an M44 1.9 then the maximum size wheels will be 16''s, the brakes packing up IMO was down to the extra work that those 15 yr old 2 lady driver calipers and discs had to do on 17" rims driven by a motorcyclist driving a car..!

    your car is the perfect proof that the chassis and engine can be tweaked to perform above the limits dictated by the stock parts,but you must make sure that you do the modifications in the correct order and fully understand the relationships between components on the car , I clearly and admittedly lacked some of this knowledge but I am a fast learner and will not make a similar mistake again!.

    what I should have done was upgrade the suspension parts, drop links, bushings, ball joints and any other related parts, and then changed the wheels!...I still feel though that I would have preferred the ride closer to the stock 16"s and for me the 17'" wheels experiment has taught me one thing...I don't like 17" wheels!.

    rich, do you still think the heavier arb's are a way to go? as i'm still planning on getting Koens ones..and from what I can understand this should just tighten things up and reduce body roll whilst keeping the handling fairly neutral.

    as we have the same variant your advice experience with this is really helpful.


    thanks

    joey
     
  4. zedonist

    zedonist Guest

    Joey, IMHO the thicker ARB's will reduce the body roll on the 1.9 significantly (based onH&R products), and will perhaps be a better modification than lowering, that said i cannot quote a direct comparison as i have replaced all joints, bushes and suspension components underneath the car in one go, but i did change the ARB's after running the Bilsteins, and it made a big difference, it will therefore be a sportier ride, quicker through corners etc.
     
  5. Brian H

    Brian H Zorg Guru (V)
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    Interesting read Joey, I ran my 1.9 for a number of years with 17" wheels with no ill effect whatsoever, good tyre choice is an absolute must (IMO wrong tyres = unpredictable & poor handling) and having the right tyre pressures also made a huge difference to me. I never ran 15" or 16" wheels so I cannot comment on these. Out of curiosity what tyre choice (brand) did you have on the 17" wheels were they a matched set of tyres and were the wheels a staggered set?

    You make a valid point in your comments which I believe led to some of your handling woes, worn parts. We buy these cars which are now getting older and expect to jump into them and have the handling characteristics of a new sports car, however the reality is that unless a car has been fastidiously maintained to the highest level you will have to spend time and money replacing worn out items. I believe the brakes that you replaced were just tired. I cannot see why a 17" wheel would create so much extra work and cause a brake caliper to start binding, am I missing something here? I can see that there may be a little extra weight involved in the 17" wheels/tyres but nothing that should cause any issues, I am not trying to be a smart [email protected]&e here I am genuinely interested in your thoughts.

    I am pleased you are now happy with your tyre/wheel choice because it is not nice to have to drive a car you have no confidence in. Happy future modding and happy:coolsteer).
     
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  6. joey

    joey Zorg Addict
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    Hi Brian,

    front tyres 2x bridgestone potenza brand new 225/45/17 rear tyres 2x maxxi victra 245/40/17..tyre pressures were correct although I tried going higher and lower to cure the problem..with no real effect.

    my thoughts on the brakes were based on possibly flawed logic! but here goes,perhaps because of the extra weight and diameter of the bigger wheels I noticed that I was having to brake harder for longer to bring the car to a stop,increased braking=more heat transferred from pads to calliper and disc and therefore facilitating the seizing of the moving parts...there was never a problem before and when we removed the callipers I checked brake lines for a possible blockage and also fluid levels this was all ok..it had been done at the last service some 6k ago but always good to have another look..

    its worth saying I do drive the car hard and perhaps just as you said they were tired...it is more than possible that my tyre choice was also a big factor and could perhaps reduced the problem considerably with a different choice, but I believe based on the evidence that the width of the wheel especially at the front was to much for the steering rack to handle and the wider rear track in my mind geometrically speaking did exacerbate the situation, apparently even new Z3s tramlined with 17"s on and if this is the case I can see that it would definitely be a problem with 15 yr old suspension parts..., I also noticed a minimal drop in acceleration as well as lower MPG, I put this down to increased rolling resistance resulting in more fuel expended for less resultant speed..the speedo was also inaccurate with the 17"s..

    also coming in to play is the roads I drive..the A31 is a pig, and at present is in awful condition as is the A322 and A331 in places, the problem was most pronounced on roads that are frequented by lorry's and with a heavy camber in either direction, my main journey is between guildford and reading and on a on a smooth surface it was fine but at night without the ability to see these ruts in the road was bordering on dangerous...the car was also m ore prone to aquaplaning at high speeds and did once or twice, never a problem with the 15"s..

    re the extra weight, including the tyre it can be as much as 6 kilos a wheel every inch you go up depending on wheel and tyre choice that is considerable and probably worth 4 MPG..per inch of diameter..not including affecting acceleration and braking..

    this is all my opinion and based on the anecdotal evidence I have from doing this with my car,as well as some web research re wheel and tyre weights, but i'm open to other opinions and quite happy to accept my logic is flawed in some way...i'm no expert!

    but must say the change in ride quality and handling now i'm on these 16''s is markedly better in every way.
     
  7. ge45ton

    ge45ton Zorg Legend
    East Anglian Crew The M44 Massive

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    Good test Joey, BMW built these cars with 15 and 16 inch wheels and you'd like to think that they know what they're doing. I'm not a huge fan of massive wheels as being an old fart I like a bit of comfort. Quite a few people seem to complain of a harsh ride from 17inch wheels and over, but it's a trade off with better handling if that's what they want. Being a bit of a tight ar#e the tyres are cheaper too ;)...
     
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  8. joey

    joey Zorg Addict
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    thanks!

    it was an interesting test all be it unintentional experiment, it just happened as the 17"s were so frickin awful! I had just to get some different wheels and the 15''s previously on were sold and I knew anyway, I didn't like them, so the 16''s were the obvious choice, I must reiterate once again having driven 80 miles today the car is a TOTALLY different animal with the 16''s on, I really can't believe myself how much of a difference it has made, the handling is not the only area either ..acceleration is markedly improved and I can only put this down to the extra weight of not just the wheel but the tyre too as lower profile sidewalls have to be thicker hence an increase in overall weight and of course a bigger wider tyre means more rolling resistance too..

    bottom line the big smile is back on my boat race:)

    the main point I suppose is on my car the handling was worse,the MPG was lower the acceleration was negatively affected, the only improvement was in grip but not signifiant enough vs the 16''s to put up with all the down sides...

    yes the 17's looked nice but in real a way detracted from the "classic sports car looks" as no old sports car I like (TR3, E type, MGA, MGB, etc etc) have big wheels they are all modestly shod and look all the better for it IMO...

    I temporarily lost sight of my own ascetic sensibilities in the pursuit of some abstract concept of "better"....for me the Z3 to coin a phrase I read on an autotrader review is "a great old english sports car designed by germans" it is the one comment that perfectly describes the classy classic lines of our little cars and it is what sets them apart from the boxsters and Z4's of this world,in any future "upgrades or mods this sentiment will be first and foremost in my mind...

    putting 17''s or bigger on a totally stock 1.9 car IMO is like giving Audrey Hepburn a boob job..;) seems like a good idea but in reality its just not needed!

    in the case of rich's lowered car it works as it gives the car a different stance and makes it look more sporty and aggressive and I think it works well, but the car then has a different overall character, a testament to how well these cars lend themselves to the expression and stylistic sensibilities of the owner..

    but for what i'm trying to do, in future if it is at odds with my leather driving gloves aviators and wicker picnic hamper on the (soon to be purchased chrome luggage rack) I will leave it well alone..!
     
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  9. zedonist

    zedonist Guest

    Well said Joey, can you test manual roof v powered roof v hard top next please ;)
     
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  10. joey

    joey Zorg Addict
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    If you fund it rich!...

    I'm skint after all of these wheel shenanigans!

    ;)
     
  11. Stormy_be

    Stormy_be Zorg Guru (I)
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    I would like to add a comment on the mpg part with bigger/higher tires.
    If the diameter of the wheels (wheels including tires) becomes bigger, it is logical that mpg will go down: higher tyre = more meters done with one turn of the wheel (but your speedo and your trip computer don't know).

    So when fitting other tire sizes, always calculate this.

    Taking the example given here:
    205/60R15:
    Tyre flank: 205mm * 60% = 123mm
    Wheel: 15 inch = 381mm
    Total diameter: 2x flank + wheel = 627mm

    245/40R17 (as the speedo is on the differential - so on the back tyres)
    Type flank: 245 * 40% = 98mm
    Wheel: 17 inch = 431.8mm
    Total diameter: 2x flank + wheel = 627.8mm

    DAMN, in this case no effect.
    But it's something to keep in mind.
    For instance with 245/45R17: diameter = 652.3mm => 104%

    IF your height is increased by 4%, the road traveled is increased by 4% without your trip computer knowing.
    When you calculate number of miles per gallon, or (number of miles + 4%) per gallon, that will make a difference to your real mpg.
    The height of the car will also have an effect on acceleration. To give a comparison: put a normal bike in lowest gear and start off, now put it in it's heighest gear and start pedeling...you will know the difference with the same BHP (you). The 4% of difference in tire height does the same (in a lesser amount of course).

    An other thing, as pointed out by Joey, the width of the tire will increase fuel consumption....more then you might think.
    It will increase acceleration for a 2.8 (as it will have more grip), but a 1.9 will have enough grip with 205's (also as all the weight of the car is one the back wheels when accelerating - less easy wheel spin then a front-wheel-drive car)

    The tramlining (with and without bigger wheels) might also be affected by having a wide body Z3 or not.
    I haven't checked, but I suppose the track of the rear wheels changes, not?

    Correction on what I read above: "the Z3 was not intended/sold with 17" wheels". It was, but maybe not the 1.9.
    On the 2.8, my car, there were 17" as standard.

    On the ARB's of Joey: he will be replacing them with 2.8 ARB's not the H&R's, so this is also "stepped".
    He's not going the full thing (which might be to much without other modifications as said here).

    Joey, does this mean your 17's are for sale :)

    Regards, Koen
     
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  12. joey

    joey Zorg Addict
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    Hi koen, interesting stats and seem to back up exactly what I had noticed, the stock 1.9 cannot comfortably handle any bigger than 16's without compromising performance...I also think there may have been slight rubbing on full lock which would back up further that BMW didn't intend them as a factory option on this variant, or maybe added spacers to account for this, so in order for 17''s to work well with the 1.9 you need spacers as well as bushes,ball joints and springs to be in optimum condition...even then without maybe an air box mod and or a remap you will notice a negative effect on acceleration and fuel consumption..

    the 2.8 will be just fine with them though as stock..

    koen sorry bud they are not for sale as they have been swapped for my 16''s with the guy in birmingham "pucko" ...

    He is a really cool guy actually and happily sent the wheels to me with no payment required so I could try them out first, just an old school gents agreement, he breaks Z3s and after my experience with him would not hesitate to recommend dealing with him,he absolutely loves Z3's and is an enthusiast running a small sideline business, I will post a separate thread and contact details once I know what the forum rules are...Gaz maybe you could comment? but I think he could be a really useful contact for us gents here and a nice fella to boot...

    I know he has another Z coming in next week which he will be breaking so maybe he can help you with some bits Koen?

    cheers

    joe
     
  13. GazHyde

    GazHyde The Gaz Monkey
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    I'm happy for you to post a personal recommendation and his contact details if he is happy for you to do so.

    Someone called Pucko from Birmingham signed up a while back so he should be contactable through the forum directly as well.
     
  14. zedonist

    zedonist Guest

    interesting concept on the 1.9 grip compared to 2.8, but it is not tyres it is roll bar thickness, as they are thicker on the 2.8 you can corner quicker, hence the need then for wider rubber, like i said earlier the whole system needs to be looked at when modifying, otherwise you can be left with poor performance
     
  15. Stormy_be

    Stormy_be Zorg Guru (I)
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    I was talking on grip at acceleration (in a straight line)
    A 1.9 has enough with the normal 205's.
    The higher torque of the 2.8 makes it can put good use of the 245's.

    I agree that in bends, it's not only the tires that not to be upgraded.
    Then it's shocks, dampers, ARB's, tires and bushes (and even stuff increasing the amount of stiffness like strutbar, etc)
     
  16. joey

    joey Zorg Addict
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    b--ugger

    so what your saying is ...when I fit the thicker roll bars from the 2.8, to fully take advantage of this mod wider tyres would be optimal?

    I notice you say you "can" corner quicker...so presumably I can just enjoy the benefit of less body roll without pushing it to the limits..?


    knowing me though..:racecar:
     
  17. zedonist

    zedonist Guest

    well yes you can corner quicker, less roll means you don't chicken out as soon as in a standard 1.9 and ease off, i don't think you will lose grip to be honest with 205's unless being a hooligan in the wet.....
     
  18. joey

    joey Zorg Addict
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    i'm on 225/50/16 now...so it "should" be fine..

    they will go on in march along with the next oil service, and I might as well replace the ball joints as well as the remaining bushes with powerflex ones...and the drop links...

    there goes another £300!
     
  19. Stormy_be

    Stormy_be Zorg Guru (I)
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    I was loosing grip a lot of times in corners on my first trackday.
    Then noticed that the rear ARB was not connected on the left side.
    So I was driving without rear ARB.

    Going over very bumpy roads, you will feel the car becoming more bumpy too.
    It's normal, ARB's will try to move the left and right wheels the same way up and down.
    This is of course the most in corners, but on roads were only the left and/or right side woes up/down, you will also feel a difference.

    That said, changing to H&R ARB's is maybe too much for a 1.9 (for normal driving).
    But changing to 2.8 ARB's should be an improvement, but not a distruction of your comfort.

    Regards, Koen
     
  20. Stormy_be

    Stormy_be Zorg Guru (I)
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    Does anyone know the price of a full poly-set?
    Is there an cheaper alternative to the real superflex polybush?
     

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