12 replies to this topic

[meb58]

When we analyze weight transfer or weight distribution by adding a larger rear swaybar for example, do we analyze weight transfer when increasing rear track width by the same means? Although both increase roll resistance the outcomes are different in my mind...

Adding a larger rear bar will increase lateral traction loss over the rear wheels - I am not differentiating between the inside or out here. However, when we increase rear track width - and I am assuming for the moment that wheel rates do not change - we increase rear roll resistance but I can not see how we increase lateral traction loss. I am aware that a wider track can raise the RC and that this might load up the tires a little quicker upon initial turn-in. But since the tires can perform more steady state cornering work when spread farther apart, they saturate at a higher threshold. The two seem to approach the question about oversteer in two different ways.

If my concern is balance and traction out of a corner, I have to have enough weight distribution to be able to point the car where I want it to go and to to aid inside front wheel traction. Why not use a smaller rear bar and increase rear track width?

Edited by meb58, 19 May 2010 - 19:42.

[Johan Lekas]

This is my thinking
Increasing track width improves the total steady state cornering capability (since the average track width front/rear increases)
Changing the proportion between the front and rear track affects over/under steer

[meb58]

And that is my theory as well. However, both a swaybar, and presumably a wider rear track in thsi instance - provide some weight distribution or transfer of weight. But the two go about their busness in different ways with different outcomes that I think are important to tuning and driving.

And I take back what I wrote above about wider rear track and smaller rear bar...I think a wider rear track allows the use of an even bigger rear bar...

[Powersteer]

And I take back what I wrote above about wider rear track and smaller rear bar...I think a wider rear track allows the use of an even bigger rear bar...

Why? Wideness decreases force acting on the suspension. Usually track width is associated with weight distribution, a heavy front car would have wider front track.

[cheapracer]

Why? Wideness decreases force acting on the suspension. Usually track width is associated with weight distribution, a heavy front car would have wider front track.

Usually a track width is associated with rules and bodywork.

MEB what is it your trying/intending to do with the car?

[Greg Locock]

Has any racer ever reduced the track of their car successfully, if they are on a circuit that has the usual proportion of corners?

If not, there's your answer.

[meb58]

Cheapracer,

When I increased front track width I noticed a fair amount of initial turn-in understeer. I assumed this was from an increase in front roll resistance - this is a Mac Strut so I did not have to worry about motion ratios. This increase in track width also helped front end grip and most of the understeer went away in steady state long-ish sweepers. The front track is 20mm wider than the rear (10mm per front wheel wider ). This seemed a proper relationship given that 62% of the weight is up front.

I thought that I might be able to tame some of that turn-in understeer by increasing rear track a little - more rear roll resistance...assuming I can get to the same wheel rate as before.

So perhaps a better way of asking the question is, how do we compare roll resistance/later load transfer via a wider track with a swaybar? I am specifically refering to a multi-link rear design.

A rear swaybar will st some point lift the inside rear wheel off the ground and its contribution to balance and inside front wheel traction at that point begins to taper off. Can I increase track width and obtain the same balance with out worrying about cornering on three wheels?

Greg,

Not sure I understand...I did play with varying front track widths as a way of identifying a track width that is too narrow. The current set up is 54mm wider than stock track - about an inch wider per side. This produced a fairly significant increase in grip...as I expected.

Edited by meb58, 24 May 2010 - 16:47.

[Greg Locock]

Exactly. increasing the track to the maximum allowed, and reducing cgZ as far as possible, and minimizing weight, are 3 strategies that would almost invariably be 'directionally correct', to the extent that having done them you'd retune the car around them. It is possible to have the rear track too wide compared with the front I suppose, but not I suspect for any normal variation.

[SteveCanyon]

I widened the front track of my racer a few years ago, had the perfect opportunity after this little spot of fun at 210km/h ->



Made it very hard to stop.

I noticed (subjectively) the car was more stable in the corners and reduced understeer with another 50mm front track.

Edited by SteveCanyon, 25 May 2010 - 05:47.

[meb58]

Steve...how faster were you traveling? I was behind a formula ford a couple years ago at Pocono...we were turning into the infield from the high speed banking and his steering shaft broke...there wasn't much drama for either of us...I was right on his tail - lucky for both of us! I was in a Sports Racer with a 78hp Renault motor. Steve, you wrote that you noticed a reduction in understeer after increasing track width...did you also notice an increase in initial turn-in understeer? I am really try to remove some of this as it tends to make tha car feel a little vague upon entry...steering feel seems to fall off just as I want the car to bite - off or on throttle.

Greg,

Am I correct writing that increasing front track will increase front roll resistance? I noticed while experimenting with front track widths that as I reduced front track width, turn-in understeer was reduced while steady state grip gradually fell off. The reason I bring this up is if this rationale - narrower front track decreases turn-in understeer - then why wouldn't increasing the rear track a bit provide some of the same benefit - after increasing front track that is. In a vacuum, no motion ratio changes to worry about...

And again, my query is really about which application diminishes turn-in understeer - wider rear track or more rear swayar. I cannot quite gather the answer from Milliken...there is no swaybar info in the book.

Thanks all for your patience!

EDIT...After thinking about this the title perhaps answers my question. A swaybar contributes to load transfer distribution and a wider track is actually the opposite, it decreases load transfer. But the effects can narrowly be the same...

Edited by meb58, 25 May 2010 - 16:20.

[SteveCanyon]

Steve...how faster were you traveling? I was behind a formula ford a couple years ago at Pocono...we were turning into the infield from the high speed banking and his steering shaft broke...there wasn't much drama for either of us...I was right on his tail - lucky for both of us! I was in a Sports Racer with a 78hp Renault motor. Steve, you wrote that you noticed a reduction in understeer after increasing track width...did you also notice an increase in initial turn-in understeer? I am really try to remove some of this as it tends to make tha car feel a little vague upon entry...steering feel seems to fall off just as I want the car to bite - off or on throttle.

It's Bill - I've had to change handles here due to poor & hypocritical moderation standards.

I'm not sure how fast I was going but it was fortunately on a new part of the track that I hadn't been on before so I wasn't going flat-out and hit the brakes pretty early. Guess it would have been around 200 km/h though. The car got all snaky as it was trying to stop on 3.5 wheels ... I managed to get it pointing a little to the right so I could take the wet line into the corner and that gave me enough room to pull up on the bitumen and then get back to the pits in one piece.
I didn't notice any turn-in understeer, it feels better I guess though I couldn't quantify it. The car does 'feel' better when settled in the corner though.
FWIW I went racing last weekend, here's a couple of vids. Nearly got wiped-out in the first one!



One of the problems the car has is that it has a very short wheelbase and the wheelbase/track ratio is about 1.55:1 I think. That makes it pretty twitchy sometimes and I suspect that other cars with the more usual 1.7:1 or so will give a different feel on turn-in, and it may be more noticeable than my car.

[meb58]

Okay, sorry Bill.

That little bit of contact could have been much worse...I learned a while ago that there is an art to being passed as well...perhaps the fellow you passed didn't look in his mirrors. Is the yellow car a Radical? I remember lining up at Watkins Glen in front a few Ferraris, a handful of modified Porsches a couple of Lotus' and a handful of Radicals...I was driving my JCW mini...only front wheel drive car there and way down on power compared to all the others...one of the Radicals was very well driven and the closing rate on that track was a little scary...I spent much of the weekend in the marbles...I think the vibration wake from the big bore Corvettes puched me off line a few times...okay, not really but they were loud!

Edited by meb58, 26 May 2010 - 13:28.

[SteveCanyon]

The poor bloke in the car I touched did indeed have his head down, trying to find a gear of some sort and he wandered off, unfortunately a tad too close to me. I made the left/right decision as late as I could and after that point he started heading right even faster. The road-going guys don't seem to realise how fast a racing car can close on them. The only damage to my car is a slight rub mark on the left-rear wheel rim.
The yellow car was another early Mallock I think.