GlenL

We didn't talk about tire brand or driving style. I'll get Kumhos for value and Hoosiers for times. Really depends on how the wallet feels at the moment.

mark kibort

your alignment settings are obvious issues. need to go to 1.8 degrees min on fronts and 0 toe, especially for track use. who recommended these settings? when I go to a track like Sears. (hard turns and lots of trail braking turns, the tires will slightly wear to the outside, but nothing like what you see here. my tires , even Hoosier A series and R100s wear very evenly. plus, at the track you should measure temps... the temps should be hottest in the inside edge to the outside edge, by 10 degree differences , outer, middle and center.

if you rears are doing this , you.might have too much toe as well and you need 2 degrees min in the rear on a 928 track car. hopefully you have a lowered car or these figures need to be higher as well.

mark kibort

1.5 degrees in the rear is not enough to keep the tire flat on the turns, expecially If you don't have a race suspension set up.
1.8 degrees front and 2 rear if you care about track performance. we have been tuning these cars for the best set up for many years now. lots of data
too much toe in the rear will make the car push and feel very tight. too much camber (above 2 degrees ) will make the car feel loose and push, because the tire is not flat and on the straights, as car says more prone to lock up. not a "hunting " problem thought .. you just don't want to run the car on the edges of the tires, in or out. the 911s and 944s are totally different. they need more camber due to the geometry of the front and rear ends. (strut vs coil over plus the geometry of the 928 coil over system and lever /attachment points)

mark kibort

brother!!! you start listening to tire company suggestions for tire pressures and suspension settings, you will find yourself at the back of the pack with corded tires! look, these guys at NITTO for example, give suggestions, but usually they are for Honda civics.
no, a 5 degree camber wont work on any car that you usually see at the track. their pressure readings are high as well, and don't take it from me, take it from the fast guys running nitto or hoosiers.

FredR

Mark,

Did you read Ken's original post? We are trying to give him a good starting point to help him avoid the obvious problems he is experiencing as someone who has a street car that he also uses on the track from time to time. This is always going to require compromises.

Regarding rear camber, if you have read earlier posts of mine you will see that I have stated on several occasions that the 928 can handle 2 degrees on the rear but at the expense of grip away from a standing start and thus I look for a good compromise that works for me and my needs.

Your car is setup for out and out track work and doubtless suits your very low ride height, suspension etc etc but your car is not everyone's car and neither the driving style. You run in some pretty hot company with some pretty fast machines and most of us respect that but I rather suspect that Ken runs in a different league to you- more in tune with the kind of profile that I modestly aspire to.

Doubtless once the OP has tried recommendations such as the ones I have recommended he will experiment to determine what works best for him and if it does the trick great.

I have tried running with minimal rear toe- did not work for me and my kind of use. May well be a different ball game on a high speed circuit. I have run with 3 degrees front camber and did not like that because of detriment to braking. I run front toe at the minimal end of the stock setting range because I like the feel and turn in it gives without being too twitchy but I can well understand why you operate with zero toe.

One size does not fit all in this game as those of us who have been through all this well know. If I fitted slicks instead of street rubber I might expect to make changes.

Very happy with what I have and what I have done and could not care less about what 911's do with their setup as long as I can stick it to them occasionally.

Rgds

Fred

mark kibort

actually, my set up is pretty mild compared to a full race set up still. there isnt much different compared to the street sport and yes, 1.5 degrees front camber can work but with a stock suspension you will burn the outside edges.... so yes, im reading the OP's post. as no need to go more than 0 toe, as he has, which also can burn up the outside edges. soft suspension, rolls the tire over more and you need more camber to handle it. thats the point, but then you sacrifice tire wear on the street, BUT, 1.5 to 1.8 degrees on a 928 is fine , regardless of suspension and lowering (which makes camber changes worse wtih compression in race conditions) So, since ive proved that theses settings can allow me to drive 1000s of miles on DOT race rubber on the street and have no weird wear patterns, he might want to adjust camber and toe a little in front to solve that nasty cord problems. those tires are not cheap, unless hes using my supplier (mr dumpster).
there is reason for my madness...... just trying to help as ive done street track for 20 years now with the 928.
curious.... what didnt you like about the less rear toe setting? I understand launch grip with a stock street car and too much camber, but wondering what you felt with the toe near 0 in the rear.
the part i was refering too with the monster suggestions for camber settings, was from the fact that you cant make any settings for all cars witihout knowing geometries of the car. a tire company is silly in suggesting that 5 degrees can work best for that tire. again, maybe on a honda with a soft suspension, but other cars? doubtful.

FredR

Mark,

On front camber I recommend 2 degrees not 1.5 degrees just not as little toe as you run. I have no differential wear issues whatsoever and I can well believe your front camber setting may be optimal with the lower frame brace I have fitted given it reduces the need for camber but the fact is my front end is rock solid and saw no need to play around any more.

Reducing rear toe theoretically helps the car drive out of the bend better and if you can get it to work great but what I experienced was I just could not get any bite in the apex of the tight bends we were running to get the drive out whereas a mid range toe setting seemed to grip better. Cannot explain this- it is just what I found in practice having tried the reduced rear toe.

Thus the logic behind my recommendations for a good starting point. Even with my Devek bar set fully stiff my 928 is still slightly tail happy but I quite like it that way

As I said, I believe you run in a different league altogether and if I ever had the good fortune to run with you at Laguna Seca I reckon I would at the very least be a good 5 seconds a lap behind you and quite possibly much more but it sure would be fun trying.

Regards

Fred

mark kibort

I think you are on the right track.. just remember the more roll you get the more camber you need..... but the 928 doesnt need much camber due to its action in compression. usually toe doesnt matter that much in tight turns, as you are really almost lifting an inside wheel anyway, so if too much toe, you get little scrubbing action. actually, it works for driving 8-10ths as you have both tires more on the ground. increased toe then works to not scrub as much of the inside "lifting" tire, as the toe on the compressed tire is increased in a turn. they line up better and thats why a lot of folks like slight toe in for spirited driving with a soft suspension.

rear toe definitely makes turn in and mid turn performance better on the track. i need some more too, as my rear toe is near street specs. the car doesnt handle as well mid turn as the holbert car due to this one diff.

laguna is a fund track.. one of the best for the 928. I think Dean Krenze ran a 1:44 when he was down from the NW for our race many years ago with his 5 liter euro. scot has run a 1:42.5 , same as what i ran in that same euro 5 liter.
the holbert car was 1:38.9 and the stroker has run 1:36.1, but i have barely been in the 1:37s lately. need some new tires!! the fastest anderson ran in the WCGT was 1:34 with DOTs but with 520 rwhp. and he ran a 1:30.xx on slicks during a POC race. Those are some fast times!

dr bob

Carl-

What are the dimensions of your toe plates? There are several options for these. I'm looking specifically for the locations on the plates where you are measuring, more specifically for the distance between measurement points on the toe plate.

I'm playing with options on DIY fixtures for setting toe. I have lasers now clamped to each front wheel. Compare lateral measurements at about 84" difference between measuring points fore and aft, so every 1/8" difference works out to 5' (five minutes) of toe angle at that measurement spread. The measurements scale down for shorter spreads, so 3/32" difference with about a 21"-long toe plate would get the factory 15' toe-in number, 1/8 would be at the max at 20' of toe-in. Toe plates are easier for most folks to make and use, but the measurement differences get so small. Fun stuff!

mark kibort

Ive matched the measurement of the hunter machine with my results by just taking a level and making a mark at the front of the tire and the rear of the tire. just use the inside edge of the mark front and rear . measure both fronts and both rears. take the distance and trig it out.
usually about 1/8" difference divided by 18" INV TAN and you get degrees.
.4 degrees /2 because thats 1/16" for each tire position, so that becomes .2 degrees or about 12mins

KenRudd

mark kibort

there is always Math !!
In this case, math helps with not having to fuss with the toe plates, lasers, alignement of the mechanisms .... just use a straight edge, a marker and get the value you need to do a pretty accurate adjustment.

FredR

Mark,

Reminds me of the constipated mathematician- he worked it out with a pencil and it came out in logs!

Rgds

Fred

mark kibort

thats funny!!

dr bob

Thanks Carl! Using toe plates or some similar hard repeatable tool for this allows mere mortals to get reliable repeatable results. No crayons or markers trying to see if the bleeding edge of that mark on the asphalt is closer to the 1/16 or 1/8" line on the tape measure. Miss by one mark total and your 'alignment' is trash. Using the laser method at 86" spread has users looking for 3/8 - 1/2" differences, lots easier to read on the tape measure with no trig needed by the user.

____

Meanwhile, this discussion is about tread wear and camber adjustment.