Traction Issues

[neo871]

I love the car to bits, but the poor traction is killing me. I'm not talking only standing starts, but also the launch control seems to be inefficient to propel the car forward. I also get a good amount of slip in rolling starts from 50km/h with DSC off. Needless to say that in MDM mode the ECU cuts the gas immediately, even when doing rolling starts.

Is anyone else bothered by the fact that is very difficult to put the power down in the new m3/m4?

[clar]

For some strange reasons, M cars have always been under-tired. Maybe BMW is trying to bring down the running cost of their cars and rolling resistance...

[clar]

Porsche 991 C2S with rear weight bias and puny torque at 325 lb/ft gets 295 rear tires while the F8x with that generous 406 lb/ft gets only a set of 275 in the rear

[brava09]

Had the same issue with my E92 M3, with much less torque than your car. All that power was pretty useless up until 60-70 km/h.

That's the biggest reason I moved to RS5.

[Algol]

I for one love being able to fry tires at will; just control your right foot to help get the power down. Then again I have had cars in the past that couldn't get out of their own way at low rpm (RX-7, STI) so coming back to a car that is a bit rambunctious at all rpm's is a huge plus for me.

[karussell]

go up to a 275/295 and you should be a lot better.this car is seriously under tired.

[gthal]

I agree it's an issue... moreso at the track IMO.

I am now in the process of moving to wider wheels and tires. 19x10 front and 19x11 rear with 265/35-19 tires along with 305/30-19 in the rear. Likely a Bridgestone RE-11. That should go a long way to dealing with the traction issue.

Keep in mind that going with a wider tire won't necessarily mean more tire on the road if you are still on narrow wheels. If you don't want to replace he wheels, then get a set of stickier rubber like Yoko AD-08 in OEM sizes (or slightly plus sized).

[JoeFromPA]

Serious question for the extremely tire educated on here:

My understanding is that a wider tire does next to nothing to increase straight line traction because it does not increase contact patch size. It will increase lateral traction because the tire will stay on the desired contact patch across a broader spectrum of dynamic cambers and loads with a wider tire available before the tire tread squirms or rolls.

My understanding is that the ways to increase straight line traction are as follows:

- Change the tire compound to a stickier compound in the dry
- Change the tire tread design to reduce voids
- Install a taller tire which will actually increase contact patch size, all else being equal

....so....with all that being said...

Help me understand why I'd want to increase my tire WIDTH to increase my straight line traction potential on this car vs. just changing the COMPOUND/tire to a stickier dry tire?

[Chadfugi]

Originally Posted by JoeFromPA

Serious question for the extremely tire educated on here:

My understanding is that a wider tire does next to nothing to increase straight line traction because it does not increase contact patch size. It will increase lateral traction because the tire will stay on the desired contact patch across a broader spectrum of dynamic cambers and loads with a wider tire available before the tire tread squirms or rolls.

My understanding is that the ways to increase straight line traction are as follows:

- Change the tire compound to a stickier compound in the dry
- Change the tire tread design to reduce voids
- Install a taller tire which will actually increase contact patch size, all else being equal

....so....with all that being said...

Help me understand why I'd want to increase my tire WIDTH to increase my straight line traction potential on this car vs. just changing the COMPOUND/tire to a stickier dry tire?

You are correct sir !

[ASAP]

Originally Posted by JoeFromPA

Serious question for the extremely tire educated on here:

My understanding is that a wider tire does next to nothing to increase straight line traction because it does not increase contact patch size. It will increase lateral traction because the tire will stay on the desired contact patch across a broader spectrum of dynamic cambers and loads with a wider tire available before the tire tread squirms or rolls.

My understanding is that the ways to increase straight line traction are as follows:

- Change the tire compound to a stickier compound in the dry
- Change the tire tread design to reduce voids
- Install a taller tire which will actually increase contact patch size, all else being equal

....so....with all that being said...

Help me understand why I'd want to increase my tire WIDTH to increase my straight line traction potential on this car vs. just changing the COMPOUND/tire to a stickier dry tire?

Correct Statement

[gthal]

Originally Posted by JoeFromPA

Serious question for the extremely tire educated on here:

My understanding is that a wider tire does next to nothing to increase straight line traction because it does not increase contact patch size. It will increase lateral traction because the tire will stay on the desired contact patch across a broader spectrum of dynamic cambers and loads with a wider tire available before the tire tread squirms or rolls.

My understanding is that the ways to increase straight line traction are as follows:

- Change the tire compound to a stickier compound in the dry
- Change the tire tread design to reduce voids
- Install a taller tire which will actually increase contact patch size, all else being equal

....so....with all that being said...

Help me understand why I'd want to increase my tire WIDTH to increase my straight line traction potential on this car vs. just changing the COMPOUND/tire to a stickier dry tire?

Here is a link to a very technical discussion that seems to suggest that the contact patch of a wider tire is bigger Tire Contact Patch. Here's a quote at the end...

Wide tires have a greater contact area? From this data it appears very likely. Which would mean the “wide tires are softer and therefore give more grip” argument is bunk. The contact patch is bigger, and the contact patch pressure is lower.

It is also my understanding is that to make a wider tire effective, you need a wider wheel. Second, I absolutely agree that the tire compound, etc may be more impactful to traction. Lastly, wider will be better for road course duty given lateral grip is absolutely improved.

I'm happy to be corrected if I'm wrong

[Taimur]

Agreed with JoefromPA.

Get a taller drag radial tire for traction. My main reason not to get 19" was traction plus the 18" look better. In addition you can run a taller 18" drag radial when you start modding the car

[JoeFromPA]

Gthal and others: My point was simply that alot of folks are getting direction and the clear inference that to "fix" the m3/m4 accelerative traction issue, people are installing 1"+ wider wheels and 10-30mm wider tires.

But that may really not be the case: either the new tire's compound is stickier, tread pattern puts more tread on the road under acceleration, or it probably really makes no difference in accelerative traction.

My point is this: If someone is looking to fix the problem, they probably shouldn't spend $3k-$5k on a new set of wheels and tires unless they want wider wheels/tires for another reason. Instead, they should focus on spending ~$1k on stickier tires - which will yield almost all the same benefits while saving a good amount of money and keeping rotating mass (tire & wheel) down.

Again, I'm not trying to present myself as an authority in this area. I'm simply trying to state my clear understanding.

[CanAutM3]

Originally Posted by JoeFromPA

Serious question for the extremely tire educated on here:

My understanding is that a wider tire does next to nothing to increase straight line traction because it does not increase contact patch size. It will increase lateral traction because the tire will stay on the desired contact patch across a broader spectrum of dynamic cambers and loads with a wider tire available before the tire tread squirms or rolls.

My understanding is that the ways to increase straight line traction are as follows:

- Change the tire compound to a stickier compound in the dry
- Change the tire tread design to reduce voids
- Install a taller tire which will actually increase contact patch size, all else being equal

....so....with all that being said...

Help me understand why I'd want to increase my tire WIDTH to increase my straight line traction potential on this car vs. just changing the COMPOUND/tire to a stickier dry tire?

In general the statement is not untrue, but it is quite more complex than this.

There is an important element missing in the equation, it's the fact that it is not only the air pressure inside the that tire carries the load, the sidewalls also carry a portion of the load. The proportion of the load that the sidewalls carry varies with tire deflection, so it makes the calculation quite complex. Wider tires can provide more longitudinal grip, but it is not a given either.

[jc05e46m3]

Originally Posted by gthal

I agree it's an issue... moreso at the track IMO.

I am now in the process of moving to wider wheels and tires. 19x10 front and 19x11 rear with 265/35-19 tires along with 305/30-19 in the rear. Likely a Bridgestone RE-11. That should go a long way to dealing with the traction issue.

Keep in mind that going with a wider tire won't necessarily mean more tire on the road if you are still on narrow wheels. If you don't want to replace he wheels, then get a set of stickier rubber like Yoko AD-08 in OEM sizes (or slightly plus sized).

This is my exact setup (as you already know) and it is WAY better for traction- especially as the tires are getting a little more broken in. I havent even experimented with lower pressures yet either.

For reference, I am JB running MAP7 with 100+ or MAP2/MAP7 with E85 blends. With the boost limiting function and the RE-11s, I am getting a much better driving experience. Launching is still a beast to tackle though. I'm 6MT.

Originally Posted by JoeFromPA

Serious question for the extremely tire educated on here:

My understanding is that a wider tire does next to nothing to increase straight line traction because it does not increase contact patch size. It will increase lateral traction because the tire will stay on the desired contact patch across a broader spectrum of dynamic cambers and loads with a wider tire available before the tire tread squirms or rolls.

My understanding is that the ways to increase straight line traction are as follows:

- Change the tire compound to a stickier compound in the dry
- Change the tire tread design to reduce voids
- Install a taller tire which will actually increase contact patch size, all else being equal

....so....with all that being said...

Help me understand why I'd want to increase my tire WIDTH to increase my straight line traction potential on this car vs. just changing the COMPOUND/tire to a stickier dry tire?

Originally Posted by JoeFromPA

Gthal and others: My point was simply that alot of folks are getting direction and the clear inference that to "fix" the m3/m4 accelerative traction issue, people are installing 1"+ wider wheels and 10-30mm wider tires.

But that may really not be the case: either the new tire's compound is stickier, tread pattern puts more tread on the road under acceleration, or it probably really makes no difference in accelerative traction.

My point is this: If someone is looking to fix the problem, they probably shouldn't spend $3k-$5k on a new set of wheels and tires unless they want wider wheels/tires for another reason. Instead, they should focus on spending ~$1k on stickier tires - which will yield almost all the same benefits while saving a good amount of money and keeping rotating mass (tire & wheel) down.

Again, I'm not trying to present myself as an authority in this area. I'm simply trying to state my clear understanding.

I think you're absolutely right. With the wider wheels, wider tires, and stickier compound, I'm getting the best of all worlds + my primary goal of aesthetics, but at the sacrifice of the extra weight the wheels and tires bring.

If someone really wants to benefit from the stock wheels, just put some R888s on there in 265/35 and 295/30. It will save you $$$ and give you much better traction, but at the cost of increased wear.

[Gstone]

Speaking of wear. How many miles should we expect out of the stock tires with mixed road driving?
And what about stickier tires?

Thanks for opinions, this is my first M.

[gthal]

Originally Posted by JoeFromPA

Gthal and others: My point was simply that alot of folks are getting direction and the clear inference that to "fix" the m3/m4 accelerative traction issue, people are installing 1"+ wider wheels and 10-30mm wider tires.

But that may really not be the case: either the new tire's compound is stickier, tread pattern puts more tread on the road under acceleration, or it probably really makes no difference in accelerative traction.

My point is this: If someone is looking to fix the problem, they probably shouldn't spend $3k-$5k on a new set of wheels and tires unless they want wider wheels/tires for another reason. Instead, they should focus on spending ~$1k on stickier tires - which will yield almost all the same benefits while saving a good amount of money and keeping rotating mass (tire & wheel) down.

Again, I'm not trying to present myself as an authority in this area. I'm simply trying to state my clear understanding.

[jc05e46m3]

Originally Posted by Gstone

Speaking of wear. How many miles should we expect out of the stock tires with mixed road driving?
And what about stickier tires?

Thanks for opinions, this is my first M.

All depends on driving style. Some can get 20k, Some get 5k. Just depends on how your right foot operates.

[M4TW]

I posted something about this in the tire forum. I am speculating that the PSS star tires were designed to improve wear, noise and mileage at the expense of longitudinal grip, but with good lateral grip.

The problem with LSD is that with both wheels spinning the car can get quite squirrelly as opposed to one wheel spinning where it will keep going straight.

Based on the comments above, I am thinking about switching to Cup 2's next year in the same size as OEM.

[FTS]

If you look at any engineering equations related to chassis and suspension design, obviously with the objective of improving performance overall, traction being one of those variables, none include the width of the tire as a variable for increase longitudinal performance. However, track width is certainly a variable in those equations. At the same time do not assume wider tires/wheels will increase track width, it depends on offsets of course.

One thing to understand is the taller side wall tires have longer (longitudinal) contract patch than same diameter lower profile tires; that longitudinal contact patch is what improves straight line acceleration performance, which is also the reason dragsters use such tall tires. Along the same lines taller diameter tires overall do improve acceleration, but increased weight of tire/wheel combination decreases performance even more, hence going with taller wheels is always to the detriment of straight line performance.

The reason most recent sports cars get more and more wider tires is because of increased vehicle weight, which in turn generate more heat on the tires, and wider tires retain less heat and disperse it much faster than narrower tires. And of course, wider tires certainly offer more lateral contact path, hence lateral grip.

There are endless links you'll find on the Internet on this, some are not quite clear cut or are too technical, but looking at drag racing circles will yield many answers on this. And also why the M platform is not an ideal drag racing platform.

Few I'd recommend for this topic are:

• https://www.physicsforums.com/thread...a-tire.587766/
• http://www.stangtv.com/tech-stories/...-drag-radials/
• http://www.hotrod.com/how-to/wheels-...tire-traction/
• http://www.eng-tips.com/viewthread.cfm?qid=14638
• http://insideracingtechnology.com/booktiredescrptn.htm
• http://www.fsae.com/

Having more power than traction is something I always wished for, and I think the F8x will provide that to me/us

[motex]

Originally Posted by Taimur

Agreed with JoefromPA.

Get a taller drag radial tire for traction. My main reason not to get 19" was traction plus the 18" look better. In addition you can run a taller 18" drag radial when you start modding the car

Can you explain why a taller tire gives better traction? Never heard that before, it will be interesting to learn something new

[Taimur]

Originally Posted by motex

Can you explain why a taller tire gives better traction? Never heard that before, it will be interesting to learn something new

Straight line traction basically comes down to contact patch and tire compound. Taller tires have bigger sidewalls which in terms increases the contact patch.
Read here -
http://www.tirerack.com/tires/tirete....jsp?techid=10

Another interesting thread -
http://www.supraforums.com/forum/sho...-true-or-false