Track-Width/handling

[azopelnut]

Ok
Here is my understanding of handling basics.
Generally speaking a lower and wider chassis is better than higher and narrow.

Question #1
When Opels are equipped with larger aftermarket wheels (the ones made for FWD cars) the track-width is actually narrower than stock and unless spacers are used handling would actually suffer at the cost of appearance. Correct?

Question#2
What is the stock track-width on a GT and on a Manta/Ascona?
Where is this measurement typically taken from?
Would a wider than stock track improve handling?

[baz]

for question 1 part right in that the handling would suffer because the front wheels could not turn to steer, thats why the spacers go in to allow the inner clearance for the wheels to turn lock to lock the whole suspension would suffer if you ran it like that
for q 2
the gt is 1254 mm @ the front and
1284 mm @ the rear
i dont have the dimensions for the manta
i think the track is messured from the centre of the tyre but dont quote me on that one

[RallyBob]

Manta/Ascona track widths are 52.4" front, and 52" rear. Track width is measured from the centerlines of the wheels, not the hub faces.

Generally, a wider track width will improve handling. If you go too extreme via wheelspacers or via wheel offsets, the front scrub radius goes to hell and the tires fight each other in the turns.

Another seldom mentioned factor is that changing offsets or adding spacers will soften the wheel rates. Note I didn't say spring rates...they stay as they are, but increasing the leverage on the springs via a greater wheel offset will reduce the effective rate at the wheels, so the suspension will be softer as a result. This amount can be easily calculated and the spring rates can be increased to compensate. Shocks will also have to addressed, they will become 'softer' too.

A better way to increase the track is to retain the same relative wheel offsets as stock, but to widen the suspension itself. This is exactly what Opel did with the Manta/Ascona B chassis.....

Bob

[billiard13]

Hey RallyBob, not to divert too far off subject, but what's a good shock to use (front and back) for street use, but possibly improve handling and ride over stock. I'm not talking hundreds of dollars per corner such as a race setup, but just any slight upgrade in street handling would be nice.

I plan on installing sway bars in the near future, if that affects your answer any. Also, I plan on using ET wheels. Any suggestions on shocks, and possibly springs, would be great.

Thanks in advance,
Claud

[RallyBob]

What model?

[billiard13]

69 GT

[billiard13]

Bump (sorry for the bump guys, was hoping for a reply from RallyBob on the shocks/springs).

[Gary]

A search for shocks in the Group 3 forum turned up 25 threads.
Check it out Here.
You may find an answer there. Try a similar search for springs.

[RallyBob]

Originally posted by billiard13 Bump (sorry for the bump guys, was hoping for a reply from RallyBob on the shocks/springs).

Haven't been around this weekend, been out shopping for land in Vermont....

For the most part, you're not gonna get improved handling and ride quality with the same shock. Koni reds come the closest though.....for a price.

High pressure gas shocks will generally ride the worst, as the nitrogen gas pressure tends to add spring rate to the suspension, as well as increased ride height. And unless they have a high-speed blow-off valve (they won't unless they're Penske or Ohlins or other high $$$ stuff), they are harsh on impacts.

I need more specifics in order to make a recommendation. Spring rates, sway bars sizes, wheel/tire weights, ride height, etc.

[Travis]

Originally posted by RallyBob And unless they have a high-speed blow-off valve (they won't unless they're Penske or Ohlins or other high $$$ stuff), they are harsh on impacts.

Bob, how does this high speed blow off valve compare to the methods used in the lower cost digressive valved shocks? My understanding of their theory of operation is that a valve opens under higher shaft velocities and the damping force essentially flatlines. Sounds alot like the Penskes... for a lot less$$

-Travis

[RallyBob]

Yes Travis, this is true, a digressive Bilstein racing shock will have this capability. However, even at $110.00 per shock, you still have a pure racing shock with heim-jointed ends, and you need to adapt it to your car (custom fabrication $$$). Most racing shocks have valving more in line with their usage, which is with high-rate racing springs and under racing conditions. So they're probably at least twice as stiff as normal street stuff.

[Travis]

At ~$110 they're a bargain compared to the big dollar Penskes.

Another option would be the steel body adjustable QA1's with OE style mounts. They run about $65

For someone serious about improving performance and ride quality at the same time, I think they could work well.

-Travis

[billiard13]

Man, i'll give you credit RallyBob, you're thorough if nothing else, hehe. I was just requesting what a good shock would be for a stock setup. My daughter's 69 looks and feels to be in need of replacement shocks.

The main thing i'm looking for tho is a simple 'ride vs handling balance' basically.

I know you have to sacrifice one to get the other, but I was looking for the best shock to balance the two on a stock setup car with addco sway bars to be installed. I believe my wheel width will be very close to stock, slightly wider at 53" from center wheel to center wheel in the back, 51 1/2" in the front.

Ride height i'm not sure where to measure it. Spring rate, as far as I can tell (and going by what I was told by the previous owner), it has stock springs on it. Their condition is used.

These other shocks you're discussing sound nice, however, i'd like to avoid having to fabricate their installation and am instead looking for something that's a direct fit. Same for springs.

If you need any more info, such as the ride height, I can have that for you asap if you tell me where you want it measured from.

Thanks again,
Claud

[azopelnut]

Rallybob wrote:Manta/Ascona track widths are 52.4" front, and 52" rear. Track width is measured from the centerlines of the wheels, not the hub faces.

Granted I am not talking about a big difference but last night I was measuring my 75 Sportwagon with Stock wheels and 195 70 13 tires and came up with 51 1/4 both front and rear. What is up with that? I measured from the mid-point of the tire on both sides.
BTW my GT was 50 1/4 at the rear.

[RallyBob]

Originally Posted by azopelnut Granted I am not talking about a big difference but last night I was measuring my 75 Sportwagon with Stock wheels and 195 70 13 tires and came up with 51 1/4 both front and rear. What is up with that? I measured from the mid-point of the tire on both sides. BTW my GT was 50 1/4 at the rear.

Was the car jacked up by any chance? That will throw the numbers off if the suspension is in droop. As will a non-symetrical tire tread, or toe alignment that is off (again affected by a compressed vs. hanging suspension). Try to measure from the inside of one tire to the outside of the other, or better yet, if you have a smooth concrete floor to drive on, roll the tires through a puddle, and drive onto dry concrete, and measure the tire tracks on the ground.

Bob

[RallyBob]

Scratch what I just said....sorta.

Duh, I just realized you said you had a Sportwagon. 1975 Opels have 1/2" wider wheels, and all the extra width is towards the inside of the wheel. This moves the wheel centerline 1/4" further inward on each side, so the track should be 1/2" narrower than a pre-'75 model 51/53/43/57. Doesn't fully explain your numbers though!

Bob