davek9

Has anyone ever used the Porsche "pull-down" tool, if so does the ride height return to extended or does it stay at the correct height when it's removed?

Was thinking one could make a pull down bar to be used when the car is on four post lifts to Adjust the ride height.

Thanks,

Dave

Mrmerlin

FWIW you really should measure the ride height with the stock wheels and tires ,
Otherwise....... verify your new wheel tire package is the same diameter as stock , or your height measurements will be off

Speedtoys

Cant you just add/subtract the radius difference from OEM wheel+tire to what you have installed to the target height?

Speedtoys

..and last question merlin...

Whats the ratio of the adjustment? If I have to go up 10mm, thats how many mm of adjuster movement front and rear??

hacker-pschorr

What size are those tires? It may be my eyes but they look small which further exacerbates the look of a high riding car.

dr bob

Yah-but, the goal is to find a ride height that satisfies the needs of the suspension geometry, and more importantly the alignment adjustments you have in the car. Want to drive the car at 160mm height? Go for it!. Just have it aligned, particularly the toe setting, at that height. Then maintain it at that height so the toe settings stay correct. At 160mm, normal road surface deviations risk a larger amount of toe change than they might at 170 or 190, but the difference isn't really huge. But it's there. At normal straight-ahead with rack actually centered, the inner joint for the tie rod is at about the same axis as the inner control shaft bushings. When you are turning and see the suspension compress on one side and extend on the other, you'll see the toe change more on the lowered car than on a spec-height car because the inner tie rod pivot has moved laterally with the rack. Most folks here, especially those who drive more briskly than I do, will scrub the outside ribs while cornering at about the same rate that the inside is scrubbed by toe-out from sagging if the toe is correct at their "normal" static ride height.

Regardless, whatever height you decide to run at, record the height as part of your alignment protocol. Then monitor the height, adjusting as needed as the suspension settles over time and use. Tread depth changes for me maybe 5-7mm over the life of the tire, so in theory I should be factoring that into my height measurements and adjustments. Good news for me anyway is that the last alignment I did was with the front tires already worn some, so the couple mm change in height over the life of a set of fronts is too small to worry about. With the car at 175mm, there's no measurable change in straight-ahead toe with a few mm change in height.

Got tires that are 1/4" larger radius (1/2" larger diameter)? That's a 6.4mm height adjustment difference to consider. Up. The larger tire will be 1/4" closer to the fender lip. Will you notice? I doubt it, as you'll be focused on the extra 1/4" of daylight under the chassis. Whatever height you decide on, measure/document the settled height in your logbook, have the car aligned at that height, measure again immediately after the alignment (telltale for whether they unloaded the suspension for you during alignment), and adjust as needed going forward to maintain that height.

For those playing along at home: I started doing my own alignment work after a highly regarded SoCal place messed it up. Twice. The loss of a pair of Pilot PS2's in a thousand miles easily justified the cost/effort of the tools and time so I can do this stuff at home. Doesn't mean you need to do your own of course -- If you have a reliable place you like, use them.

Got a 4-post lift? Put a couple trailer tie-down loop in the inside of the rails up front, under the factory tie-down loops. Or clamp a steel crossbar under/between the ramps to pull down to. Grab a couple good turnbuckles with hooks at the hardware store, connect between the ramps and the loops on the car, and you can easily pull the car down to your target height so you can align on the lift. It's possible I'm sure to pull the car down extra-low and relieve then retighten the rear bushing clamps. Release the turnbuckles and see if it recovers exactly to your target height. Then perform your alignment without moving the car. Obviously, a key through all of this is knowing in advance what that target height is.

M. Requin

What an excellent point.

davek9

Thanks dr bob !

"...Got a 4-post lift? Put a couple trailer tie-down loop in the inside of the rails up front, under the factory tie-down loops. Or clamp a steel crossbar under/between the ramps to pull down to. Grab a couple good turnbuckles with hooks at the hardware store, connect between the ramps and the loops on the car, and you can easily pull the car down to your target height so you can align on the lift. It's possible I'm sure to pull the car down extra-low and relieve then retighten the rear bushing clamps. Release the turnbuckles and see if it recovers exactly to your target height. Then perform your alignment without moving the car. Obviously, a key through all of this is knowing in advance what that target height is... ".

This answered my question

Dave

Socal_Tom

rjtw

My '83 is definitely low. REALLY low. I can barely get two fingers between the front tires and the fender (much less the 4 fingers Tom shows). And for the first time ever, I've hit the skid plates and handful of times during hard cornering if there's any appreciable change in slope in the road. Ouch. Stock wheels and tires and the height has never been adjusted, ever.

I'm really concerned about corner weighting and getting this done right and am not sure I'm comfortable with just dialing X turns or adjusting until the height measures correctly. Even if you get the height measurement nailed, are you really corner weighted properly? I don't have a scale so don't see how I can do this at home properly.

Bottom line -- I'm in NoCal -- is there an expert "nearby" anywhere who can do this? (And this is from the guy who never lets ANYONE work on my car lol!!!) Bob, should I bring it up to you??

dr bob

Put a paint mark on each adjusting ring. Count the turns you add so that you can move the other collar the same amount. Your corner-weighting will stay as it is now.

Speedtoys

Where in norcal? I can make suggestions if you have the $ to spend on it.


"I'm really concerned about corner weighting"

Dont be, 99% of racers that THINK they should be, cant drive well enough to leverage it anyways...its cool to say it, but you'd never know, or really benefit from it given the time sink it is to do it properly.

dr bob

Reality: Unless you happen to have a pair of springs that aren't the same free length, the "count the turns" method of maintaining side-to-side loading is more than adequate for street cars. If you want to get fussy, you can calculate spring rates (or read the mfr's data) and relate that to the difference in free length, multiply by the LCA ratio, etc. Or put the collars at the same spots on both and call it a day. "Perfect" corner balancing makes perfect sense so long as you drive on perfectly flat surfaces. Otherwise it changes as soon as you roll the first wheel out of the garage.

----
Probably a decade ago or more now now, a SoCal local hurriedly swapped in new springs and dampers, paying no attention to getting the adjustments consistent. Then height-balanced the car without much regard for the interaction of the diagonal spring loading. On transition between pulling and trailing throttle, the load would transfer side to side as it moved front to back. His hurry was to make it to a "fun drive" planned for later that day, a casual cruise through Angeles National Forest just north of where we lived. It was a fun day with a few roadside repairs to a couple cars. On the way down the hill, the lead swapped to one of our more aggressive members who knew his car well, and the new shocks and dampers dashed off in hot pursuit. We let them go, mostly due to an issue with the rev limiter on my car. Rolled up on them a few miles down the hill, with the new springs and shocks just downhilll from a corner and a berm he'd driven into, RF suspension dangling broken from the impact. That's an extreme case, but still a reminder that keeping the car at least somewhat balanced side to side can be important. Having two diagonal legs slightly longer then the others means the stool will always be tippy.

Speedtoys

^^Id only blame the driver. he would crashed any other car that day. He didnt know it at the time, but that was his intent.

dr bob

Jeff (Speedtoys) knows the Norcal racing services community well, and can recommend a shop to do the alignment and corner balancing. You still get to adjust the basic ride height first, then go settle the suspension before you balance and align.

I don't own balancing scales. I take advantage of clinic days an other opportunities to check the adjustments on my car, but theyv'e never been far enough from good to make it worth adjusting and aligning again.

In SoCal we hosted clinic days, and once in a while it would include suspension and alignment. I don't have an alignment rack, so everything is done on the floor, with lasers and a tape measure and a digital angle gauge, plus a bubble level and drill bits as spacers. Since it's a user clinic, it's ideally presented in a lesson format where the owner actually holds the tools. I promised in November to put together an updated instruction for folks who'd rather DIY their own alignment, and it's on my project list. I'd also planned to grab the materials while I was on holiday in SoCal to fab a set of fixtures, but my favorite metal supply store was closed while I was there. We may fab a set out of wood with metal feet or something. Regardless, my day gig is getting in the way of fun stuff as it does every year at this time.