PorKen

One thing I've noticed, now, is that the rear end corkscrews less when the tires slip.

I should have mentioned that. The second time (first time with 18s), the left toe adjuster stripped, so I had to put one on, hence the large variance.

BTW, if you need a rear toe eccentric bolt, make sure you specify 86.5 up, or better, 98mm bolt/116mm total length! The earlier bolts are only 84/100mm.

Bill Ball

Ah, so. Drive on!

mark kibort

i think it was iceman's sheets that showed .25 degree total toe.

so, my question is , why the difference?

mk

Bill Ball

It looks like different machines with different databases and possibly some errors in one of the databases.

Brian's shows different spec range for front right and left camber. ERROR on left side - maybe Nascar setup
Brian's shows correct front caster for pre- 1991 spec.
Brian's shows front toe range too low - the unit symbol is hard to read - looks like " (inch sign)
Brian's shows correct rear camber range
Brian's shows rear toe range too low - the unit symbol is hard to read - looks like " (inch sign)

Ken's shows correct front camber range
Ken's shows correct front caster for pre- 1991 spec.
Ken's shows correct front toe range
Ken's shows correct rear camber range (well, close enough)
Ken's shows correct rear toe range

I would ignore what the sheets say and make sure I had the WSM specs with me.

WSM specs converted to decimal degrees and range calculated
FRONT
Camber: -0.5 +/- 0.17 degree (RANGE: -0.3 to 0.7)
Caster: 3.5 to 4 degrees (updated in 1991 to 4 to 5 degrees)
Total toe-in: 0.25 +/- 0.08 degree (RANGE: 0.17 to 0.33)
REAR
Camber: -0.67 +/- 0.17 degree (RANGE: 0.5 to 0.8)
Toe-in each side: 0.17 +/- 0.08 degree (RANGE: 0.08 to 0.25)

PorKen

Perhaps I'll get used to the new setup, but I must say I liked the handling of the 16" rims, with the old alignment better, the short time that I had them/it.

<- But now I'm rollin' on 18's, beyotch!

Bill Ball

What's different? I had to go with a narrower front tire on my 17s due to less offset, and the front pushed in the twisties. When I switched to the BFG KDW 2s, the front stopped pushing.

drnick

ken, what differences are you noticing? what 18" rims are you using? with the rear toe ecentric, is the later part a replacement for all model years - ive got a bolt that wont undo and will need to be cut through.

drnick

bill, i guess you are familiar with the experience of chasing a 928 handling fault! so many variables, change one thing and the problem sometimes transmutes..

PorKen

Nick,

I have 993 twists (18x7.5 50et, 18x9 52et), they fit, just, with 225s, 265s, and the stock rear 21mm spacer.

It really likes to follow the crown of the road. Cornering is excellent, however. The heavier rear rims do take a bit more time to wind up. I'm afraid of what the dyno will subtract for these baddies.

There are two eccentric bolts, one for all the welded steel toe brackets, and one for all the aluminum brackets.

drnick

ken, ive found the car to be very sensitive to suspension changes either the tyres or the rims could change the feel and handling. new tyres like to heat cycle and the copycat rims are not always true and are almost always heavier. having said that, i think the lower et on the front rim will certainly be making the front want to pull the steering more. ive had less issues with tramlining since maxing out the front castor.

mark kibort

what do you think the dyno results might show????

Remember, i gave the formulas a while ago. it will be insignificant, at BEST.

Think about it this way, you are taking the extra weight, and accelerating it over time on the dyno run. dyno runs take near 6-8 seconds, and the rpms on the wheels are from 800 to 1600rpms. simple equations can show the hp required to spin up 20lbs (10 each wheel and tire) from 800 to 1600rpm on a 25" diameter. its less than 1 hp at best .

as a rule of thumb, the effects of wheel and tire weight at a 2 ft diameter, is same effect as if 2x that weight was in the car. If it is only wheel weight that is changing, then the effect is more like 1.4x.
The HP effects will vary by the acceleration rates.

mk

PorKen

Nick,

I think you (and Bill) may be right about the tires. I replaced the rears, but the fronts are old and near the wear bar. I'm going to get new tires first. I may yet have another date with the rack, but next time I'll have a rack centering bolt!

I'm also going to see about making a liftbar for the rack jacks, going from balljoint to balljoint, so the front wheels can be lifted without messing up the suspension. I suspect rolling the car on the rack to calibrate may not work well with the sensors this machine has.

mark kibort

sorry, that wont work. you need the leverage the tires give by being outboard. CT tried that in the old days and i just laughed at them, for what seemed obvious. lift it by the ball joint and its just like jacking up the car, but the spring is compressed about 1/2 normal. (not enough to make a difference)
need to do the "roll back technique" !

mk

Bill Ball

Check beforehand that you steering wheel is centered when the rack is centered and you won't need the to bring the centering bolt.

drnick

i think the 928 is more sensitive than most to having different tyres front to rear.