Should I upgrade from 18" to 19" on Zed DD

[cj10jeeper]

They still used 13" wheels and small discs before energy harvesting, the difference is the composite material used that only works at high temperatures. Road cars will need bigger discs for their heat capacity though. In an F1 car the tyres actually form a large part of the suspension so a move to low profile requires a complete redesign. They would have seen less grip with thinner tyres as it would have skipped around.

I don't think we're disagreeing. As I said - complex answer.

Tea break over. Having a mare reconnecting my Jeep rear anti sway bar and oarts of the suspension

 

[Steve84N]

Neither do I, just saying the energy harvesting is a red herring.

Weather is wet here, hope you're not plagued with the same problem.

 

[ben g]

Simple answer...
18's drive better, handle better.
19's drive worse, handle worse.
:lol:
F1 car's use 13'' wheels if I remember rightly.

That's a ludicrous generalisation.

It was a sarcastic comment, hence the emoji's. If you really think I'm comparing my Z4 to an F1 car then you must be on some kind of mental mind messing drug.

 

[A1GSS]

well who knows

 

[goldbcfc]

Here's my bit of input, I bought my car with 19" 8.5/9.5j it tramlined terrible so I swapped to my other wheels I had on my last E46 19" but with 8.5j all round and the Z4 drives perfect now. Id read about E46 M3's mainly using a square setup on track to counter any oversteer problems. For track days in the Z4 I use 18" 8.5j all round they are lighter, I think that's what you have to remember moving from 18" to 19". At slow speeds like parking I can notice the front wheels feel lighter to move the steering wheel left/right. I wouldn't say the ride was any different softer/harder but my car is lowered and my E46's before were so I'm sort of used to the ride being hard. The Z4 is a sports car at the end of the day its not meant to be comfy like driving a 5 or 6 series etc so it has never been an issue for me. If I want a comfy car to drive I can borrow the mrs VW golf that puts my suspension to shame or maybe I'm just getting old. I'm buying some new wheels for bmw show next month most likely I will get some more 19".

use something like this it helps with sizing,offsets and weights etc

http://www.wheel-size.com/calc/?wheel1=235-40-19X8.5ET50&wheel2=265-35-19X10ET38&fcl=50mm&wcl=30mm&scl=50mm

 

[JINGLE]

well im moving from 18s to 19s this weekend

RE: weight... my new AVA Memphis are:

fronts - 19" 8.5J ET35 - 11.7Kg
rears - 19" 9.5J ET35 - 11.1Kg

any body know the weight of the original 18" 108 wheels?

 

[Steve84N]

Here's my bit of input, I bought my car with 19" 8.5/9.5j it tramlined terrible so I swapped to my other wheels I had on my last E46 19" but with 8.5j all round and the Z4 drives perfect now. Id read about E46 M3's mainly using a square setup on track to counter any oversteer problems. For track days in the Z4 I use 18" 8.5j all round they are lighter, I think that's what you have to remember moving from 18" to 19". At slow speeds like parking I can notice the front wheels feel lighter to move the steering wheel left/right. ".

I'm surprised that a square setup would be used to counter oversteer as it gives less grip at the back so it's probably to quell understeer...?

Surely, the differences you felt were due to tyres not wheels?

 

[TomK]

Id read about E46 M3's mainly using a square setup on track to counter any oversteer problems.

I'm surprised that a square setup would be used to counter oversteer as it gives less grip at the back so it's probably to quell understeeer

Indeed that's correct, one of the benefits of the square setup is to help combat understeer. I used to run this on track on my m3.
Personally, having run 18s and 19s on my car with comparable tyres for some time, I would and have chosen to sacrifice the looks for the increased sidewall height. The roads in Gloucestershire really aren't the best though.

 

[STUBOY2UK]

I was on 108s with runflats and M suspension. I'm now on 19s with proper tyres and lowered on Eibachs.

I definitely have to be more careful now when it comes to potholes and speed bumps but I think it's worth it for the looks. I think the lowering has caused more issues than the 19" wheels.

 

[andy.c]

I went from 18" upto 19"s last year, mines on standard suspension and is a daily and I didn't notice much difference in the
ride quality.

You should see if anyone locally to you is running 19"s and go out for a little drive with them to see if you like it or not

 

[ben g]

well im moving from 18s to 19s this weekend

RE: weight... my new AVA Memphis are:

fronts - 19" 8.5J ET35 - 11.7Kg
rears - 19" 9.5J ET35 - 11.1Kg

any body know the weight of the original 18" 108 wheels?

How comes the wider rears are lighter than the fronts?

 

[goldbcfc]

well im moving from 18s to 19s this weekend

RE: weight... my new AVA Memphis are:

fronts - 19" 8.5J ET35 - 11.7Kg
rears - 19" 9.5J ET35 - 11.1Kg

any body know the weight of the original 18" 108 wheels?

Id think there about approx the same if not a little lighter maybe around 10.5 kg reason they might be lighter is there made by BBS so should be as light as possible being a track based alloy brand manufacturer. I've just checked the link below and most are 11.5 to 12.5kg for Z4 but for the 108's theres no weight given. I'm shocked the new rears weigh the same as front when there 1 inch wider that's really good sometimes there's a bit of a myth when people think aftermarket is heavier alloy. Its usually the wider wheel which can be a negative as they normally weigh more. I explained earlier mine feels lighter to turn on 18's at low speed so did a quick calculation on the link below. Whilst my rear widths stayed the same there was almost no difference in weight. The front the now being 0.5 inch wider on my 19" actually weighed 2kg more each side which is what I'm feeling in comparison to the 18" 8J wide.

bmw alloy styles
http://www.bmwstylewheels.com/Z

wheel calculator
http://www.wheel-size.com/calc/?wheel1=225-40-18X8ET47&wheel2=225-35-19X8.5ET40&fcl=50mm&wcl=30mm&scl=50mm

Here's my bit of input, I bought my car with 19" 8.5/9.5j it tramlined terrible so I swapped to my other wheels I had on my last E46 19" but with 8.5j all round and the Z4 drives perfect now. Id read about E46 M3's mainly using a square setup on track to counter any oversteer problems. For track days in the Z4 I use 18" 8.5j all round they are lighter, I think that's what you have to remember moving from 18" to 19". At slow speeds like parking I can notice the front wheels feel lighter to move the steering wheel left/right. ".

I'm surprised that a square setup would be used to counter oversteer as it gives less grip at the back so it's probably to quell understeer...?

Surely, the differences you felt were due to tyres not wheels?

Not all bmw come with wider rears the main reason for wider rears is traction on acceleration in a straight line hence why you see drag cars with huge wide rear wheels and little thin small front wheels. Try driving a drag car around a track and it will most certainly oversteer. Square/box setup has been used by racers for a long time to counter oversteer this isn't something new. Its pretty much common sense if you have a narrower front wheel than rear wheel the car will oversteer. Having used this square setup on both my E46's and now Z4 the car always feels more planted around corners and gives more confidence I think

 

[JINGLE]

i have no idea why the rears are lighter, i was the same and expecting the rears to weigh more as they are wider, really confused me, defo accurate tho as i weighed them 3 times each!!! (i thought maybe the surface i put scales on wasn't level.... but it was same in 3 different rooms lol)

the actual figures were:

front 11.7Kg
front 11.7Kg
rear 11.2Kg
rear 11.1Kg

very suprising

 

[Steve84N]

If you go from 225 and 255 to 225 all round it will oversteer more. Yes a dragster will power oversteer but it will handle with massive understeer.

 

[goldbcfc]

If you go from 225 and 255 to 225 all round it will oversteer more. Yes a dragster will power oversteer but it will handle with massive understeer.

FWD cars "understeer which would be easier to deal with than oversteer in a RWD. The reaction to correct understeer is to lift of accelerator braking until the car comes under control. This is more natural to the people than the reaction to correct oversteer by staying on the accelerator and keep the front wheels pointed where you want to go if you lift off you will spin. Which maybe a common mistake in many RWD accidents to novice drivers. If all you are interested in is the 1/4 mile then a skinny tyre at the front and wider wheel at rear to control any wheelspin. Drag racing is where the wider look started being associated with performance. I have 225 all round and tracked both the Z4 and my E46's running this setup. Like I said this isn't something new people have done this with racing RWD cars for ages it counters the oversteer and gives better stability in the corners giving better times. Wider rears is for more for the traction in the straights and aesthetics look. There are plenty of bmw's that leave the factory with non wider rears.

The only way for you to know I suppose is try it for yourself, You also get the added bonus of switching tyres around front to rear so they wear even and your not replacing rears at twice the rate as fronts.

 

[Steve84N]

FWD cars "understeer which would be easier to deal with than oversteer in a RWD. The reaction to correct understeer is to lift of accelerator braking until the car comes under control. This is more natural to the people than the reaction to correct oversteer by staying on the accelerator and keep the front wheels pointed where you want to go if you lift off you will spin. Which maybe a common mistake in many RWD accidents to novice drivers. If all you are interested in is the 1/4 mile then a skinny tyre at the front and wider wheel at rear to control any wheelspin. Drag racing is where the wider look started being associated with performance. I have 225 all round and tracked both the Z4 and my E46's running this setup. Like I said this isn't something new people have done this with racing RWD cars for ages it counters the oversteer and gives better stability in the corners giving better times. Wider rears is for more for the traction in the straights and aesthetics look. There are plenty of bmw's that leave the factory with non wider rears.

The only way for you to know I suppose is try it for yourself, You also get the added bonus of switching tyres around front to rear so they wear even and your not replacing rears at twice the rate as fronts.

I'm sorry but you're talking tripe.

FWD and RWD will oversteer and understeer, but that's not the point here.

The 1/4 mile dragsters use small skinny front tyres for low rolling and air resistance, it's nothing to do with over/understeer as they go in a straight line...

Wider tyres on the front or back isn't just about traction. To a point a wider tyre will give more grip on that axle so a wider front in relation to the back will give less understeer. Don't believe me, ask Porsche why they put a 265 on the front of the latest GT3 RS. It's to give greater front axle grip and hence less understeer. Wider or smaller tyres are used on different axles for weight distribution reasons too. It's why you see rear or mid engined cars with a greater differential in size between front and back.

Smaller rear tyre & no change up front = less rear grip = more oversteer.

Racing cars tend to increase the front tyre width rather than reducing the rear to give more front axle grip. This leads to what is closing in on a square setup, but it wasn't to reduce oversteer but understeer.

 

[SonnyA85]

On the wifes mini cooper D we went from 16" to 17" and the ride quality was horrible. so much so if one of the 16's wasn't buckled I would of put them back on. this is with goodyear eagle f1's on the 17"s so nothing to do with the tyres.

i have 18's on the z4 108's and tbh i'm thinking 17's would be a much better suit for the car ride wise.

what 17" options are there for an e85 z4?

 

[goldbcfc]

Used this set up on last 3 bmw's I'm only sharing my own an others experience of facts.

Lets compare a F1 car and drag car they both have wide wheels but on a drag they will be taller to have a longer contact patch. The F1 car will use wider tyre too for better cornering but the wheel will be a lot smaller so less contact patch for acceleration but better lateral grip for corners. On both you will notice the sidewalls are huge compared with a road tyre, compare this to say a 10 or 11 inch wide rear on Porsche/bmw etc running small sidewalls. The patch is wider but length is still smaller than using a narrower tyre. It really depends how the vehicle is setup I guess the Porsche has a chassis to make the most of this like you said. On track though these super wide wheels are more to do with heat made, the bigger side wall tyre F1/DRAG will be cooler than one with smaller sidewall tyre on a road car. Wider tyres are not always better they don't always give better traction. It depends on the car, the situation, the conditions. Eg. Rally cars use wider tyres when on tarmac rally's, and use very thin tyres when on ice rally's. F1 cars used to use narrow tires until aero began to be used in the 60's. Drag racers actually want tall tyres, width is there to stop the tire being destroyed.

maybe u just need to go and try for yourself we cant all be wrong using square on track to get faster times can we?.

 

[Steve84N]

You're going quick as you're car turns in nicely due to not having too much rear grip compared to front. If you ran 255 all round you'd go quicker again.

 

[goldbcfc]

You're going quick as you're car turns in nicely due to not having too much rear grip compared to front. If you ran 255 all round you'd go quicker again.

Stop watching topgear, get off the sofa, get out on track and try it is all I can say as we must all be wrong using a square setup then. Let me guess it should have wider rears because bmw wanted that and their the best engineers therefore no one improves their cars....lol

I work in trade as a motor technicain by the way for a main UK dealer