Are we adding more rubber than is necessary

[Ahbengdriver]

On my 335 E92 for example. The stock 18 tyres are 225 and 255 front/rear, width-wise.

On the B pillar label, the reccommended 19 tyres are also 225/255. However, many of us use 235/265 bcos the rims we buy are usually wider hence requires a wider tyre. We all know the pros/cons. More rubber more grip but also slows your car sometimes. There must be reasons why BMW maintains the rubber width altho some would argue what is just 1 extra cm of rubber.

 

[e46monster]

Re: Are we adding more rubber than is necessary

sounds logic and makes sense. however, real world experience -
gti - all 4 corners standard 215x45x17 upgraded 225x40x18 and found the grip NOT sufficient while cornering and accelerating as frt tyres spun terribly and then, further upgraded 235x40x18 and voila, better off the line and cornering due to more grip.
135i - rear standard 245x35x18 to 245x30x19 (bbs specs) and then, up again to 255x30x19 as the 245s grip was insufficient. would have loved to go rear 265s but, unable to fit.

if you have the power = go for more rubber for improved grip and cornering besides the chio look.
if insufficient power = stick to specs if pick-up important, else go to thicker rubber for improved grip and chio look.
believe me any extra rubber is important although if too thick and insufficient weight to imprint on the road in the wet, we could acquaplane.

 

[Girettom]

Re: Are we adding more rubber than is necessary

it may just be a case of running different pressures with the new size. Lower pressure would, I guess, give you more contact area and softer tyre walls. So it may be better to up the pressure a bit to reduce the contact area a little giving you more weight per sq inch and harder walls for cornering.

 

[kenntona]

Re: Are we adding more rubber than is necessary

On the B pillar label, the reccommended 19 tyres are also 225/255. However, many of us use 235/265 bcos the rims we buy are usually wider hence requires a wider tyre. We all know the pros/cons. More rubber more grip but also slows your car sometimes. There must be reasons why BMW maintains the rubber width altho some would argue what is just 1 extra cm of rubber.

Stock figures for stock cars. Is your car stock?

 

[Terry]

Re: Are we adding more rubber than is necessary

Doesn't matter imo.. Bmw gives a certain spec.. Might be optimal , might not be optimal.. Nothing is perfect for all u know they don't even put research into this..

For bmw.. Marketing , cost cutting , looks. , performance., partnerts.. All come into consideration

Basically wider rubber does no harm...

However ecu tuning I have different view.. I think bmw has their own reason so ifor ecus I don't touch

 

[Girettom]

Re: Are we adding more rubber than is necessary

Thanks to ABD, I just spent the last hour scouring the web for all things tyre related. There are three really good references I found so far.

Car Tyre Bible (mentioned by Jinooi before)... Car Bibles : The Wheel and Tyre Bible Page 2 of 2

Tyre load, area of contact, and pressure - F1technical.net...http://www.f1technical.net/forum/viewtopic.php?f=6&t=6330

And this article from Autospeed...
http://autospeed.com/cms/title_Tyres-Grip-and-All-That/A_108915/article.html

Seems, at the pinacle of the sport there is a lot of science into the contact area of the tyre (both at macro and micro level) and in the compounds that create grip.

However, the basic upshot is that the width of the tyre has little bearing on the grip other than reducing the weight on the point of contact by a small degree. The width helps, really, with cooling the tyres as grip is created by friction between the surfaces of the tyre and the road. When the rubber gets too hot the grip levels drop (have to admit that I haven't read the links in full yet though)

 

[ryan]

Re: Are we adding more rubber than is necessary

Running 225/265 right now for my setup. Primary for daily driving and track.

Whatever floats your purpose.

To me however, paying premium for wider tyres for looks isn't worth it.

Moving to 235/265 michelin cups in future for track driving works for me.

 

[TripleM]

Re: Are we adding more rubber than is necessary

ryan..i saw u drift at T14 Ryan at last trackday...what a sight...
intentional or u were fighting the car?

 

[totoseow]

Re: Are we adding more rubber than is necessary

i am stock! i will upsize only for looks.

 

[e46monster]

Re: Are we adding more rubber than is necessary

it may just be a case of running different pressures with the new size. Lower pressure would, I guess, give you more contact area and softer tyre walls. So it may be better to up the pressure a bit to reduce the contact area a little giving you more weight per sq inch and harder walls for cornering.

18s on the gti - running 260kpa and 270kpa both after 30mins of driving.
19s the 135 - running 270kpa frt and 280kpa rear both after 30mins of driving.

both regardless of the width on the 2nd upgrading, the pressure is maintained.
that means for the 135 rear 245x30x19 vs 255x30x19 the pressure is same.

 

[kenntona]

Re: Are we adding more rubber than is necessary

I think there is a distinction between contact patch and (lateral) grip.

"So why do wider tyres perform better when cornering? Well apart from the softer rubber compound giving better mechanical keying and a higher coefficient of friction, they have lower profile sidewalls. This makes them more resistant to deforming under lateral load, resulting in a more predictable and stable contact patch. In other words, you can get to a higher lateral load before reaching the peak slip angle."

 

[TripleM]

Re: Are we adding more rubber than is necessary

First and foremost

It's all in the marketing. Today's BMW cars non Ms are all equipped with RFTs.
stock 225/255 Potenza RE050A RFT....so, the car has no electric air pump kit when you hv tire puncture.
Optional wheel size is typically 19in, so the available RFT is 225/255 as well from Potenza....check the table chart at Tirerack as proof....
Profiles from 40/35 to 35/30 , same widths...no other choice for the same brand!

We dont expect to see a label that suggests non RFT since all cars come std in RFT...and so u know RFT sizes are strictly more limited than non RFTs...

A reco is a reco and more often than not, it's based on vested interest.

 

[VolanteDB9]

Re: Are we adding more rubber than is necessary

wear 2 lubber will look better and safer? most important is it fits...why make it look wider than it is? more wear and tear...wear pua liao jialat...need to tow your baby for morning after service...quite long and tedious while you sit on the tow truck and endure the stares.

 

[Shaun]

Re: Are we adding more rubber than is necessary

ryan..i saw u drift at T14 Ryan at last trackday...what a sight...
intentional or u were fighting the car?

he was fighting the car (wink wink), punching it repeatedly in the face... videos coming soon

don't play play.. ryan is ascendant trained

 

[ryan]

Re: Are we adding more rubber than is necessary

ryan..i saw u drift at T14 Ryan at last trackday...what a sight...
intentional or u were fighting the car?

Was fighting the car.... lol

Ok let's get back to topic.

 

[roberttan]

Re: Are we adding more rubber than is necessary

First and foremost

It's all in the marketing. Today's BMW cars non Ms are all equipped with RFTs.
stock 225/255 Potenza RE050A RFT....so, the car has no electric air pump kit when you hv tire puncture.
Optional wheel size is typically 19in, so the available RFT is 225/255 as well from Potenza....check the table chart at Tirerack as proof....
Profiles from 40/35 to 35/30 , same widths...no other choice for the same brand!

We dont expect to see a label that suggests non RFT since all cars come std in RFT...and so u know RFT sizes are strictly more limited than non RFTs...

A reco is a reco and more often than not, it's based on vested interest.

Business is business,if no marketing lots of people will lost their job,and you will not able to find any new technologies,nice showroom,staff attired,clean workshop,GOOD serive and not last new modelsss.
wider rubber does provide better grip on dry condition but is more prompt to Aqua plan when is wet road condition (skiddding).
SO to produce a street tyre that fulfill both above condition is not a easy task,that is Why premium brand rubber R&D R&D (cost $) developing new product to make a safer tyre , part of the effort also try to develope tyre that for different climate/weather/region/even car type and also how to preserve the tyre quality life span.so that deliver rubber to consumer the best performance.
To me is no point spend thousands of $ on rim and save on rubber which is more critical to your driving.
Just MHO

 

[centurion]

Re: Are we adding more rubber than is necessary

my 2 cents: the main issue to me, why variance from the manufacturer's specifications is not a good idea, is car balance.

If the ratio of contact rubber of rear:front increase, the car will understeer compared to stock.
If the ratio of contact rubber of rear:front decrease, the car will oversteer compared to stock.

Yes, there are some who vary the ratio to BETTER than stock, but those cases needs lots of testing and change.

Also, too much grip will sometimes result in blown engine. Including dry sumped engines, also will blow, coz cornering more than spec permit will induce oil starvation. All BMW engine wet sump, and M engine is wet sump with aux pump to prevent oil starvation.