Why does my ride height look so high even though it's lower than spec

[Oh Haha]

If your tires say 15 inch then they are 15 inch wheels. You simply cannot install 15 inch wheels on 16 inch tires or vice versa.

The only way to reduce the tire to fender opening gap is to lower the front via the torsion bars adjusters.

[Oh Haha]

[QUOTE=kach22i;5630411]It looks high for being lowered to lower than Euro. I have no idea why - sorry.

My new 60 series are about 1-3/4" taller in diameter and make parking lot maneuvering much easier.


That looks much better George.

[Wil Ferch]

Ossiblue.....your analysis is correct in my view--> quote .." If you are trying to lower the car body (point B in diagram) relative to the center of the wheel (point A), then the gap measurement that results should be larger than the 124mm indicated, not smaller...."

jawakil.....a 16" rim will be almost 17" according to where you measure...so a 15" rim being 16" where you measure is probably also correct. The tire diameter has to fit "inside" the maximum lip diameter of the rim and these 2 dimensions cannot be absolutely the same. If it makes you feel better....take the rim off and tell us all the numbers you find on the backside. That will tell us for sure if it's 16 or 15. Oh...by the way, if you so this, don't fully depend on the 6Jx16 or 6Jx15 stamped raised letters you see.....I found a factory Fuchs with a stamping error that showed 6x15.... that was TRULY a 16" rim. Look instead to the 911.XXX.XXX.XX numbers. That will tell us directly.

[Flieger]

Why don't you post a photo of the angle of your A-arms. Mine are level at static ride height. That is about as low as you want to go. I have 22mm front torsion bars, 22mm Weltmeister anti-sway bars, Rebel Racing A-arm bearings, and no bump steer stuff or raised spindles.

If the angle is still "good" just lower it more and make sure to get it aligned.

[RSTarga]

215 60 R15 is not the proper tire for that rim Since the original 185/60 vr15 is nla most go to a 195/55 I believe the 215 60 VR15 should be on a 7" wide wheel ie. The rear on an RS

[mickey356]

Would it be easier to just install adjustable rear spring plates and "fine tune" the ride height with those and the stock front adjusters? It seems that lowering these cars (especially the rear) is trial and error, unless you've done many, and with all the different wheel and tire combos out there there really isn't a "stock answer".
I know a bump steer kit and an alignment is still needed as well as corner balance but if you're gonna go to the trouble of rear torsion bar adjustment why wouldn't one just spend $300 for adjustable rear spring plates and be done with it for any future adjustments? You go to all that trouble and then possibly find out you've gone too low or not low enough and you have to go in and do it all over again. I think it's about the same intitial amount of work to swap spring plates as it would be to adjust the rear height anyway. Just a thought.

[Wil Ferch]

kach22i....you say... " There is a surprising variance in the actual heights/diameters of 205/60 and 215/60 tires between different manufacturers. Tire rack is one of the few sites which list them. You should be almost 25" diameter, but could be less than 24" from what I've seen in the charts.

I don't buy it ...but will believe you if you can show me. Yes... I agree there is a lot of variation...but I see this mostly in section width and tread width. Pls show me a 205/55-16 or 215/60-15 ( I presume these are the right sizes you meant to compare, as these are the ones being discussed) that are less than 24" in rolling diameter.

[ossiblue]

jwakil,

The picture I posted was from another thread and the 124mm was on it already--sorry for the confusion. The thread was about lowering and included measurements of Euro height and lower. You may wish to look at the reply posted by Bill Verberg as it mentions A-B measurements that cover the illustration I posted. Here's the link, scroll down to post #4:

lower my 911 targa 79 to euro spec??

[Wil Ferch]

Mickey.....the discussion here is about the front ride heights, and not being able to reconcile the dimensions given on Porsche's spec books. With all due respect, the ease ( or lack of ease) of adjusting the rear is outside the scope of this thread's discussion and doesn't help the situation being discussed as to why the front is so high.

Furthermore, the rear adjustment has been made less "hit and miss" once Tom Fitzpatrick and I collaborated and offered a rear spring plate adjustment guide. Most on this board who use that method have found it to be pretty much "spot-on" first try.

[Wil Ferch]

To All:

The diagram posted in response #18 of this thread...and cross-referenced back to a Bill Verburg answer...is part of the confusion I mentioned in the outset about never being able to understand Porsche's publications.

That exact diagram is used for Porsche's 1974 Tech Spec books...and it shows 108 mm.

for 1975....the Tech Spec books show---> 108 mm for the 911 and 911S, 113 mm for the Carrera, 93 mm for USA, and 93.5 mm for Turbo.

for 1976/77... it shows---> 108 mm ( Carrera)...93mm ( USA Carrera)...93.5mm (Turbo)

for 78/79/80/81...the same book shows---> 108mm (911SC)....99 mm ( 911SC for USA/Canada/Japan).....94mm(Turbo)..... and 85mm( Turbo for USA/Japan/Canada).

for 82/83....108mm ( 911SC)....99mm ( 911SC- USA/Canada/Japan) with footnote " 108mm for 83 onwards".....94mm ( Turbo)....85mm ( turbo for USA/Canada/Japan) with footnote "94mm for model year 83 onwards.

for 84/85/86/87...... 108mm(Carrera, all markets).....94mm( all markets)

All measurements are (+/-) 5mm.

[jwakil]

Wil...you need to read Wayne's 101 book (where he has similar diagram) or Bentley, and you will find clearly that 108mm is the Euro spec, 99mm is the US spec, but more importantly that a LARGER NUMBER for this dimension MEANS LOWER HEIGHT (It's also obvious if you just look at the diagram). Since I'm at 120mm, I'm about half inch LOWER than spec. My total tire diameter is also 24, not 25 as you assume. Anyway, I don't think my bottom line question is answered.---My tire to wheel well gap looks too much for a lowered car.

[Reifle]

Here is my '77 after I had it lowered to "european" standards.

Prior to the adjustment the measurement from the ground to the bottom lip of the fender was over 25 ins. After the work was done the car now sits 23 ins from the ground to the bottom lip of the fender. I am running with a 15 X 7 fuchs wheel and 185/70 Toyo tire. The back really sagged at first - the tire was just in the wheel well. I replaced the shocks in the back with Bilstein Sports and she sits perfectly! I like the way the car is level to the ground - it has a great stance now! The front shocks were done when the car was lowered (bump steer kit and turbo tie rods as well) and aligned. She drives like it is on rails - great turn in and not terrbily tail happy. I barely have 2 fingers between the tire and the fender lip.

[911pcars]

Originally Posted by jwakil

Wil...you need to read Wayne's 101 book (where he has similar diagram) or Bentley, and you will find clearly that 108mm is the Euro spec, 99mm is the US spec, but more importantly that a LARGER NUMBER for this dimension MEANS LOWER HEIGHT (It's also obvious if you just look at the diagram). Since I'm at 120mm, I'm about half inch LOWER than spec. My total tire diameter is also 24, not 25 as you assume. Anyway, I don't think my bottom line question is answered.---My tire to wheel well gap looks too much for a lowered car.

Your assessment is correct. The front tire-to-wheel well gap is too much.

Suggestion: Glean through the many photos on this site, pick a side view you like that appears to be Euro height or so, then replicate it on your car. Record the number of turns of the torsion bar adjusting screw so you can return to the previous height if needed. Follow suggestions for gas and driver weight, then measure from ground to top of wheel well. Report back to us with a photo for confirmation and validation . A front end re-alignment should probably follow.

Sherwood

[Wil Ferch]

My mistake and my apologies.....it is I who had it all backwards.

Let's start over.

According to Porsche, the target value for (a- b) = 108 mm. If you are at 120 mm, then indeed you are correct, and the car is supposedly 12mm lower than spec ( according to the Porsche spec books.) Yet, oddly, you "look" to be higher.

As we can see from your photos, this does not look correct. So we must now focus on other numbers.

As was said....Porsche had always used tire/wheel combinations that got us close to 25" rolling diameter. Half that ( for the "a" dimension) *should* then be 12.5". Instead, you measure 11.75". Right there we have a big discrepency and we should understand why.

Let's first do the math on what a generic 215/60-15 *should* be.

215mm= 8.46"
60% of this (aspect ratio) = 5.07"
Total tire height should be rim diameter and 2x aspect height...or 15 + 5.07+5.07= 25.15"
Half of that ( for "a" dim) should be 12.57".....yet you are measuring 11.75". Right there is a height problem of 0.82" or 21 mm. The only reason I can think of is that the tire is out of spec because of wear and/or underinflation and/or tread "flattening" on the bottom. One or more of these characteristics should be there for ANY tire....not just yours, so this is still a mystery.

With 11.75" and assuming the "flattening" effect is negligable or at least the same for all other "correct" tires....then the rolling diameter is closer to 23.5"...a full 1.5" off spec. This alone can account for a large portion of the "space" you have on top of the tire as referenced to the fender lip.

All I can say is that for my 85....using 205/55-16 tires....the "math" came up with just under 25" rolling diameter and so did ( IIRC) the "a" measurement. This resulted in a fender lip measurement of just over 25.5"...combined with the lower A-arm being just about horizontal.

Maybe we look at this point again as a question...as I don't believe we ever got an answer. With your current setup...what is the A-arm angle? If it is horizontal already, it then says you shouldn't go any lower as the outboard balljoints will then be higher than the inboard pivot points of the A-arms...and your camber curve would be royally screwed up. This then circles us around to figure out why the 215/60-15 tire is so "small" in radius in its "installed" state.

?????

[Wil Ferch]

As follow up to my techincal gaffes.....I have edited and/or removed certain earlier comments I made to this thread that were found to be technically incorrect. For the sake of accuracy as an archived document. Sorry for the confusion this caused.

That said....some more things to chew on. We mention that Porsche systematically used tire/rim combos over the years right from the 356 days..... that gave a rolling diameter close to 25" . We perhaps need to "Factor-in" the possibility that the later combos achieve that with lower profile tires on larger diameter rims. Therefore the "squish" of the flat portion on the contact patch may be less due to the shorter/stiffer sidewall of a lower profile tire....which can somewhat alter the results.

To recap...the OP has 26" ground-to-front-fender lip measurement...which has been seen for a lot of US cars...and is only about 0.5" higher than desired. Combined with high-profile tires ( relatively speaking)..also noting that they are worn...resulted in a much smaller rolling diameter than expected..making the "visuals" look more "spacey" than anticipated. All working together to make this look much worse than it really is in terms of open space above the wheel, etc.

Cranking the front down with the adjusters ( 11 mm protruding hex at each side of the cross-member...about 1 turn=1/4" height effect)...should get you there. In a separate thread, Chuck Moreland suggests that the front suspension be unloaded, and that the screw threads be lubed...when you do this. One can otherwise do this dry and with the car weight on the suspension as you do this, but it might needlessly distress the threads this way. Lowering will also tend toward toe-out, but I don't think this will be an appreciable amount....still...if you started with "0" toe....it will be net-toe out result and maybe not good to end up this way...so check.

Also...just to complete this thought process...it might be good for the original poster to tell us the lower A-arm angle...either as it sits now, or after the lowering of another 0.5"

Lastly....just for record, I measured the rim diameter of a 6x16" Fuchs (red line measurement equivalent to the previous posting)...and it was about 17.25+".

[kach22i]

Originally Posted by jwakil

My total tire diameter is also 24, not 25........

From what I can find in 215/60 (mostly all season) 24.7" is common, don't know how you loss 3/4".

You would be able to see 3/4 inch.

The 205/60 in Hankook is almost 1/2" shorter than other brands, none of that exact size/ratio are under 24" though.

What tire pressures are you running front/back?

[jwakil]

Tires are pretty worn which could explain the 3/4" loss. I run ~32 psi. So 24inch total wheel diam seems reasonable. (From Wils rim measurements, I feel more confident I have 15in rims, at least that is settled).

I looked at the A-arms, and the top surface is pretty much horizontal with the ground, maybe very slighly lower towards the tire. I have no desire to lower the car more.

Could an incorrect mounting of the shock inserts be causing the higher than expected fender height (26inch) given the small (24inch) wheel height? As for as I know I have stock Boge inserts. I'm wondering if there is an extra spacer or something in there. That could explain why everything is low down at the A-arm/torsion bar but high at the fender.

[Flieger]

Some USA 911SCs had big spacers to raise the ride height. Not sure of the years.

[Vancouvertechie]

Here is my gap with 25" in the rear and 25 1/2" in the front. I am running 205/55/16 and 245/45/16 in the rear.

[jwakil]

Actually, now that I think about it, if there was some issue with shock raising the car, it would also raise the torsion bar, so forget that hypothesis.