Widened suspension?

[WD-40]

Hey gang.

One of the most common things the off-road crowd does is widen their suspensions for a more stable stance. In my searching, I can't find that anyone has done it for track or autocross... is there a reason why not?

For a Standard Beetle, it's all simple bolt-ons, and you can buy everything you need to do it without any welding or fabrication. The front of a Super would be more of a challenge, as you would have to move the spring perches out into the fender area... but it could be done.

Whatcha think?

- David

[Greg Ward]

Putting even 7" front and rear rims on a Std Beetle (like mine) widens it enough in all reality.

The front track being "slightly" wider than the rear will help stability terrifically.
However, severely widening the rear track will make it oversteer much easier.
Severely widening the front track will make it understeer much easier.

A balanced combination with the front just a bit wider than the rear is perfect for road racing or the track.

I've seen for example a Baja set up for the dirt, run a road race track, it was very (excessively IMO) wide front and rear track, and when it didn't understeer on a lower speed corner it was facing the wrong way from the rear sliding out

[kdf]

The front track being "slightly" wider than the rear will help stability terrifically.
However, severely widening the rear track will make it oversteer much easier.
Severely widening the front track will make it understeer much easier.

Generally, widening track improves grip when cornering. A wider track reduces load transfer so the tires are more evenly stressed.

I'm just wondering why widening the rear track would make the rear lose grip while cornering? I have a basic understanding of the physics involved, but I know that theory doesn't always apply. Vw's keep on surprising me.

[Greg Ward]

I agree totally with you, but it needs to be done carefully.

Sometimes I'm not so good at explaining what I'm trying to say, but that's why I said "severely" widening.

NO doubt, widening the track makes everything more stable,BUT it needs to be done in proportion.
And whilst I say that in reality 7" rims are all that are necessary I believe, I have had the offset (backspacing whatever you want to call it) adjusted so it will still fit under standard fenders as well.

So the type of widening I'm talking about is when you see cars with the wrong offset that need massive rear fenders to cope with them, or even they still stick out past that!
Example 2, I have a good friend who had and early 60's Beetle, it had Big fibreglass flared fenders and 8" widened steel rims! It was the most fun even with a mild 1915cc engine as you could drive it on the street speedway style. All attributed solely to how wide the rear track is.

I also found the exact same thing when racing Karts WAY back in 1989, you would always reduce the rear track in the wet so it wouldn't slide as much.

My open-wheel racecar is exactly the same, much wider front than rear, I'll send Greg C some pics of that to show all you guys, cause a lot was learnt from that car too, and it ALL applies to all cars, these things we find aren't solely a VW thing, even though particular handling traits come definitely from it being rear engined, rear wheel drive.

Just as the quickest search on google as I'm running out of time.

Check this out, look at the front compared to rear tracks on these, the fastest of all circuit racing cars, ask yourself why? differences are HUGE.

http://www.motorsm.com/motorsport/auto/F1/2005_cars.asp


Later,

Greg

[WD-40]

Greg-

Thanks for sharing your experiences! I would love to see those pictures too, if you find them.

Some comments though:

The baja example you gave- did this car have sway bars removed, and was it raised up? There's a lot of changes for off-road that are definitely not right for the track!

The F1 thing is interesting, but I'll also point out that Porsche has given their 911's a wider rear track than front for years. The 2006 911, for example, has a front track of 58.5", a rear of 59.7. Now, certainly, Porsche has done their homework on handling and suspension design!

Last, I agree that the wrong offset wheels are a problem. They put extra stress on wheel bearings, and change the steering geometery up front. That's exactly the reason why I'm proposing widened suspensions- you can leave the wheels at an offset that is good for the bearings, and still get the widened track.

- David

[Marc]

The local SCCA-affiliated autocross group's rule book limits you to a 2" maximum track width increase. In the stock classes you're allowed no more than 1½" wider-than stock rims and a maximum offset deviation of ±¼" so you'd eat up most of that 2" without any change in suspension width.
SCCA rules (especially those on engine preparation) may not have been written to expressly exclude ACVWs but they couldn't have done that much better had they tried. You can run-whatcha-brung for a few races while competing as a Novice, but once you're required to move to your car's appropriate class you may as well resign yourself to being an also-ran. Chris has gone to a couple of events so far driving cars that aren't even remotely prepared but would still be illegal in class due to displacement and carburetion restrictions. He's acquitted himself quite well which was no surprise but the only "home" I can see for a bug is in the "time-only" group...unless you're easily-excited and could get a thrill out of flogging a near-stock one.

[ericsbracer]

Most of the vintage groups, as well as current SCCA classes, are very similar in limiting both rim width and overall track changes. Some of the vintage groups are more lenient than others, but adding 2 or 3 inches to the track will certainly get you some unwanted attention. Ultimately, you'll end up running as an 'exhibition' car - just as Marc suggests.

Surprisingly, the vintage groups may offer you the most competitive place to play - if you're willing to build a true "period correct - state of the art (for the time)" racer. You'd be very surprised how well Supers did at both the regional, national and professional levels on courses that suited their lack of a fifth gear. Back East where I got my first exposure to road racing (and got hooked), good finishes at Briar, Lime Rock, Mid-Ohio and Nelsons Ledges were common. Even a Standard has a fighting chance on the right sort of tracks, but the limitations of front drum brakes makes it a bit more difficult.

[kdf]

Increasing front track (or decreasing rear) may allow the front to take care of more weight transfer. The rear wheels will be more evenly loaded and acceleration in corner exit will improve (assuming rear wheel drive ofcourse).

[bigGreen]

Increasing the front track only improves stability under deceleration
This is good in emergency stops on street cars, for people who cant drive properly...

A wider rear track improves stability under acceleration & on corner exit. That's why Porsche 911's and most mid-engine race cars will have a wider rear track.

I think the formula 1 cars are limited by regulations & not by engineering considerations. So the track is just as wide at both ends as the regs allow. But all F1 cars all have stability control built into their braking systems, so presumably they can overcome regulation constraints with electronics....

[kdf]

My thinking seems to be a bit slow because I’m used to thinking about race cars as the rules I’m concerned of permit them to be. And writing about this in English doesn’t help either. I know this is an extremely complex thing to explain and in suspension set-up everything affects everything, so I’ll try to keep it simple.

There are three ways to affect the total load transfer of a car when cornering: CG height, track width and the weight of the car. Less load transfer means that the tires will be more evenly loaded. Widening track width means that there is less weight transfer taking place. Even if you widen track at just one end of the car, there will be less load transfer in total.
Less total load transfer = the whole car has more grip when cornering.

Increasing the front track only improves stability under deceleration

Increasing track doesn’t improve performance when accelerating or decelerating in a straight line, but it does increase grip when cornering. Because there is more grip available for cornering, braking or accelerating while cornering can improve with a wider track.
You could also say that widening the rear track could improve performance when braking and cornering at the same time.

But all F1 cars all have stability control built into their braking systems, so presumably they can overcome regulation constraints with electronics....

The current F1 cars don’t have electronics controlling the brakes. Anyone who has seen a F1 race can tell you otherwise, they lock up their inside front wheel all the time when braking. F1 cars do have traction control systems.

[bigGreen]

Well I shall not talk about weight transfer here because it’s too simplistic and also contravenes the laws of physics. Basically I do believe that there’s actually no such thing as weight transfer. A sideways centrifugal force is added to the weight of the car as it corners, and it’s that which pulls the car sideways, nothing else. The same effect holds riders on the fun-fair Wall of death against the inside of the drum as it spins. Weight itself is never transferred, it always acts straight down towards the centre of the Earth. The weight never changes direction and never changes in size. If it ever did, then we could probably invent anti-gravity machines, create free energy, and instantly solve all the world’s energy problems, and more… J . So I don’t ever talk of weight transfer because its over-simple and contradicts the laws of physics.

Quote "Increasing track doesn’t improve performance when accelerating or decelerating in a straight line, but it does increase grip when cornering."

Well as far as I know that’s not true at all.
It's an oversimplification to say that a wider track (front or rear) would always improve handling & stability. It simply doesn't. All it really does is help to keep the car from tipping onto its side. Doesn’t improve grip at all - Only bigger tyres can do that. And it can create a lot of negative problems too. In a lot of cases a wider track can even make a car roll slightly more when cornering. I think this is true of all MacPherson strut and swing-axle type suspensions. Don’t ask me to prove this to you.

Generally speaking though, a wider front track gives better stability under deceleration. And a wider rear track gives better stability under acceleration.
Circuit racing almost never involves huge amounts of acceleration in a straight line. It happens mostly on corner exit. So here a wider rear track is useful. Wide front track is not...

If you ever watch a high performance SuperBeetle raced, you'll probably see the driver having great difficulty in keeping control when accelerating out of the corners. But he'll have no problems holding his intended course on the way into the next corner. Simple reason for this as far as I know, is the SuperBeetle’s wider front track.

Quote "You could also say that widening the rear track could improve performance when braking and cornering at the same time.”
Well I don’t think it does that at all. It makes a car more likely to spin under those conditions. On its own, a wider rear track would make the car more unstable under deceleration – whether going into a corner or trying to hold a straight line. So I wouldn’t say it at all. And excessive widening of both front and rear will make the car generally more twitchy & unstable - on both the straight lines, and on the bends. That’s not a good thing either.

Anyway, in my opinion (which could of course be wrong) for a SuperBeetle you should really think of increasing the track at the rear (911 style) before you make the front any wider. In my opinion it would be wiser to have a slightly wider rear track on a rear-engined car used for racing. Wider front track is good for a street car where safety under emergency braking conditions is most important, but I definitely wouldn’t have a wide front track for racing.

About the comment on F1 traction control though, it uses the same electronics & sensors as ABS. Didn’t know they don’t use it to assist braking in F1 though. But in any case, I’m sure the F1 engineers can make the most use of it to control the car’s stability when accelerating out of corners. And if forced to have a wider front track (which basically they are at the moment, due to the regs), then that extra stability from traction control would definitely be useful then – on corner exit.
i.e. The wider front track on an F1 car must help it to keep the car stable on corner entry. But must also cause it stability problems on the exit. So I’d bet their traction control helps an awful lot on corner exit.

cheers, bigGreen