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Width Vs Traction?

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It was mentioned in another thread that narrowing width increases traction.

Can someone give more details?

I am wondering if this applies to mini chassis' on asphalt. Will a narrower front provide more grip on asphalt surface?

6mm hex's are often discussed as the default on a mini, but the above has me wondering.

Thanks.

:)

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it is only 1 factor on the overall picture... back in late 1990s the touringcars were running 22mm supernarrows

narrower width puts more weight=pressure on the footprint which can improve grip - but so can downforce

but when rubber compounds improve, bigger footprint may give better grip for less down pressure

overworked rubber will also overheat faster

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I assume you mean track width and not tyre width.

My understanding would be that if you narrow the car it will lean more in the turns and increase the pressure on the outside tyres generating more grip.

I would expect just softening the front springs would have the same affect.

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I assume you mean track width and not tyre width.

My understanding would be that if you narrow the car it will lean more in the turns and increase the pressure on the outside tyres generating more grip.

I would expect just softening the front springs would have the same affect.

I've used the quick n dirty width (widening) trick to overcome a sudden onset (half way through a meeting) of grip roll on indoor carpet touring car racing..

The reason its quick is because tamiya provide spacers that fit between the back of the wheel and the hex adaptor i.e. just whip the wheel off. The harder but imho better solution is to solve it with suspension - shock angle, shock oil, shock piston, spring weight. camber, diff height, anti roll bar thickness etc...) changes.

Paul ;)

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I assume you mean track width and not tyre width.

My understanding would be that if you narrow the car it will lean more in the turns and increase the pressure on the outside tyres generating more grip.

I would expect just softening the front springs would have the same affect.

You are essentially correct. Narrowing the track will effectively raise the roll center so as you corner the weight will go to one side or the other faster in a turn. What you are doing is trading stability for faster steering response.

You can also get more steering by softening the front springs, stiffening the rear springs, using lighter oil in the front, using a heavier oil in the rear, or some combination of these, and not affect the stability, with of course a different trade off. All the above will cause more weight on both front tires instead of just planting the outside ones more.

I have enough problems with rolling my Mini that raising the roll center would be the last thing I would want to do. The off throttle over steer is one of those things I can just never get use to on the M-03 even with all the weight I've added to the back end and the ultra stiff front springs.

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I have enough problems with rolling my Mini that raising the roll center would be the last thing I would want to do. The off throttle over steer is one of those things I can just never get use to on the M-03

Thats what makes the mini such fun!

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I have enough problems with rolling my Mini that raising the roll center would be the last thing I would want to do. The off throttle over steer is one of those things I can just never get use to on the M-03 even with all the weight I've added to the back end and the ultra stiff front springs.

after a day's trashing of new M05... learnt

1, never lift off :D

2, softer springs seems to help more than going harder like on M03

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There are several ways to reduce grip roll on a Mini;

Lower profile tyres - if your rules permit them, use 55D tyres (Tamiya, Xpress, YR or similar).

Widen the track, as above.

Fit adjustable upper arms & give it more negative camber (although it can cause very uneven tyre wear)

Run a band of CA / superglue around the tyre sidewall so that as the car rolls onto the sidewall, it loses grip & slides.

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...Narrowing the track will effectively raise the roll center...

Too true, never thought of it that way. Thanks for making the reason make sense :D

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Thanks very much. So its about transferring more weight to the outside wheel, but incurs the roll center height increase as a penalty.

My M05 is quite stable on carpet, and with tarmac now in summer traction rolling is even less likely, so I might try reducing it if traction can be gained.

I will post up results :)

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Narrowing track width lowers the roll center guys. This is what makes the car roll more and transfer more weight. A higher roll center would make the car roll less... :)

Here's a picture to help you picutre roll center changes. If you pulled the tire in towards the center, your roll center would drop slightly:

rollcouple.jpg

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Narrowing track width lowers the roll center guys. This is what makes the car roll more and transfer more weight. A higher roll center would make the car roll less... :D

Here's a picture to help you picutre roll center changes. If you pulled the tire in towards the center, your roll center would drop slightly:

rollcouple.jpg

Thanks 94. I was hoping you would reply.

So, will it be beneficial to use narrower hexes then? I'm on 6mm's currently.

Thanks :)

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Narrowing track width lowers the roll center guys. This is what makes the car roll more and transfer more weight. A higher roll center would make the car roll less... :)

Here's a picture to help you picutre roll center changes. If you pulled the tire in towards the center, your roll center would drop slightly:

rollcouple.jpg

Your picture is showing what happens when you change the mounting point of the a-arms, something you can't easily do on an M-series car, but something that you do do on a touring car. The center of gravity would not be the same distance from the hub if you were widening the track. Easiest way to see this is to just draw both sides of the car.

Since we're talking about moving the tire on the hub, and not lengthening the arm itself, I don't think there will be an effect on the arm angles.

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Thanks 94. I was hoping you would reply.

So, will it be beneficial to use narrower hexes then? I'm on 6mm's currently.

Thanks B)

I can't really say. In spite of all the theory, it all boils down to how the car handles after the change. Typically if you narrow the front, you give the car more oversteer. If you narrow the rear, you give the car more understeer. But as we all know, these things can sometimes have the opposite effect due to unforeseen circumstances.

Personally I have only just begun to touch on setup changes when racing. I've been focusing my last two years of racing on simply building a consistent and repeatably stable car to begin with. Once you can build a consistent car, and are able to identify your small repeatable issues while driving, only then can you start to work on your setup with positive results. I just wish our track had more test & tune time. We only get about 20 minutes of practice before the heats start. And those 20 minutes are packed withe everyone from novice to expert playing crash derby... ;)

Here is a link to the Hudy setup book. It tells you about all the typical changes that can be made to a touring car, and when to use them. It also tells you what to look for and how to identify problems. The best part is the flow chart near the end that puts everything on one page. Essentially it all boils down to the following issues:

- Oversteer

- Understeer

- Grip Roll

...in the following locations:

- Corner Entry

- Mid corner

- Corner Exit

...in the following conditions:

- On Throttle

- Off Throttle

The Hudy setup book is the 3rd download down from the top:

http://www.teamxray.com/teamxray/products/...0d1edb530cec450

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Your picture is showing what happens when you change the mounting point of the a-arms, something you can't easily do on an M-series car, but something that you do do on a touring car. The center of gravity would not be the same distance from the hub if you were widening the track. Easiest way to see this is to just draw both sides of the car.

Since we're talking about moving the tire on the hub, and not lengthening the arm itself, I don't think there will be an effect on the arm angles.

If you read what he's trying to say, you'll realise that he's not refering to the differance in the two setups in the picture but rather he asks us to imagine the lines an roll-center if the track were to be narrowed (sorry if this comes out sounding high and migthy, that is not my intent, English is not my mothers tounge and I'm writing with my mouse due to my son sitting in my lap)

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If you read what he's trying to say, you'll realise that he's not refering to the differance in the two setups in the picture but rather he asks us to imagine the lines an roll-center if the track were to be narrowed (sorry if this comes out sounding high and migthy, that is not my intent, English is not my mothers tounge and I'm writing with my mouse due to my son sitting in my lap)

Yes exactly... If you were only to move the wheels in towards the center, the roll center would drop slightly. Probably a small change similar to changing the upper control arm angle. Perhaps I'll get my AutoCAD out to make a diagram...

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Okay, after making an image of the roll center change, I'm finding that the shallow angle of the imaginary lines makes for a VERY small change in roll center. It's so small that I'm guessing it has absolutely nothing to do with the difference in handling. It's much much smaller a roll center change than even adjusting camber. Of course the lower the instant center (the outter point where your imaginary control arms intersect) you start with, the less change you will have due to the shallow angle...

Roll Center vs Track Width

RollCentervsTrack.jpg

Roll Center vs Camber Angle

ROLLCENTERCAMBER.jpg

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Very cool diagrams - thanks for going to that effort. B)

That clears up any concern I had about roll center nicely. I will get some narrower hubs and try it out, and will post up after.

Thanks to all for responding!

:D

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