My thoughts exactly

I am glad I am not the only one to have misunderstood his question.

 

Do you mean the front track is wider than the rear? By how much?

 

17mm on each side, also using 9.5" wide wheels.

n

 

Widening the track should (feel free to shoot this theory to pieces ) also change your effective spring rate in that by moving the wheel further out, it will have greater leverage over the shock/spring setup and the amount the wheel travels up and down in relation to the shock/spring will increase slightly due to the increased radius it is moving in. Not sure what effect the amount of widening you are talking about may have on your shock/spring performance if any as I haven't played with track widths.....yet

Agreed also with the increased load on the wheel bearings. This was a real problem when racing STI's but doesn't seem to be a prob with the EVO.

 

Yes, what you are describing is called "wheel rate". Widening the track will lower the wheel rate as you stated by increasing leverage the arm/spindle/hub/wheel assembly has on the spring.

Widening the track will also change the effect the moment arm created by the center of gravity height has on chassis roll and weight transfer...

 

First of all, JTB posted good post and should be read by all. It's just in the wrong thread but really isn't all that wrong I suppose. Anyway, very well put. Couldn't have done better myself.

Back on topic ez is correct, widening the front wheel centres will reduce lateral load transfer. A little bit like reducing the height of the cg. The end effect is more front end grip, or rather increasing the front end relative to the rear thus reducing understeer. In contrast to lowering the car, you are not moving the roll centre and therefore the roll axis of the car remains in the same position. Also you're not lowering the cg so braking should be pretty much the same.

Lowering the front roll centre should have a similar effect (of reducing the lateral load transfer). To do so 'properly' you should try to keep the roll axis at the same height at the cg and reduce the height at one end and raise at the other. But what you should end up with is that the end with the lowered roll centre will have more available grip and the other less available grip and so you can get the desired over/under steer effect - so the theory goes. Perhaps when you lower the front, the brake balance is upset and so braking and turn-in is adversly affected. But then you'd have to be doing serious lowering for that...

The possible problem with running wider front track than the rear is that I'm not sure how the ACD, AYC or even S-AYC willl take to it.

The wheel rate will change also, but I don't think this is either here nor there and is more of a by-product rather than a direct result IMO.

 

Regarding the wheel bearings, I doubt you'd notice any reduction in life of the bearings. Yes an additional moment will act on the bearing, but he's running +35 with 3mm spaers, so effective offset is +32 which isn't all that much...

 

do you mean longer wheel base? longer wheel base provides more high speed cornering stability. the shorter the wheel base is the easier it is the turn the car.

i won't comment on swinging out the rear... that is sort of up to the driver.

 

seems no one took to my comment about reduced overall lateral grip.

i'd say track tuning is not a good way to dial out understeer. why? cuz if you don't increase the track all around... then you're leaving something on the table.

and if you're finally hitting the fender (and the fronts are wider than the rears) then you've gone and changed the slip angle of the tires. this change in slip angle does not get you the maximum lateral cornering grip that is possible with a "straight" setup.

it's not that huge of a deal but it's not ideal. you can be fast both ways but neutral handling can be achieved in different ways.

 

Sorry, yes I meant wheelbase ...

 

I was hoping someone would pickup on this also. Not that the Evo has the greatest potential for midcorner speed but nonetheless we don't want to lose much if we can help it.

I was hoping to avoid upping the rear spring rate (or lowering the front) but I'm running out of alternatives.

 

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Funny you should mention that. Why would you say that increasing the track reduces overall lateral grip?

Widening the distance between the fronts would reduce lateral load transfer and should therefore increase the total available grip (see my post above). You're effectively increasing the front grip relative to the rear...

I suppose if you do it by reducing the rear track then you'd limit the available grip at the rear which will reduce understeer but reduce overall grip.

I think I get your comment about the 'straight' set up, but surely running wider front (than stock) and keeping the rear stock is better than the bone stock setup?

 

the thing is you end up increasing hte slip angle generated because the difference from front to rear. the front will hold more, the rear won't, this generates a slip angle on TOP of the slip angle induced by maximum load cornering.

on a skid pad this results in less than optimal g numbers. the fact is however that a good river will drive around this or a good driver will DEMAND this in their setup because it has it's strengths. at that point it's all about preference.

but from a strict skid pad analysis... there is a margin where it will benefit and then a point at which it will hurt g numbers.

 

+1

Changing track width ratio front to rear is a valuable tool for balancing out the handling of the car. I did this on my last race car (an M3) as part of the suspension set up.

A couple of observations from my experience:

- The wider the track on the front, the better turn in you'll get. Wider track slows down the weight transfer
- Wider track in the rear on a RWD car adds high speed stability

From Carrol Smith's "Tune to Win", "The advantages of wide track widths are reduced lateral transfer for a given amount of centrifugal accelleration..." This means more cornering power.

 

Installed the 15mm H&R spacers last nite. Longer studs were supplied in the box. Used a hammer and WD40 to get the OEM studs out...2-3 taps and they came out easy. I don't think the bearing was effected in any way. Then I used a 12x1.5mm nut with 2 washers to pull the H&R studs back into the wheel hub. Again with WD40 it went very easy.
My main motivation was to push the stock front wheels out as my front camber is 2.6 degrees and makes it look kinda funny. H&R says it's safe to widen the track as long you don't exceed 2% of total track width. The Evo 8 track is 1515mm and adding total of 30mm on the axle (15+15mm) is within the safe 2%.
Taking the car on track this Friday...will give you a short report on the handling (hopefully improved handling )