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However, Mark Anderson did style me with a BEAUTIFUL used windshield for less than it cost to install the darn thing. money well spent. Looks PRETTY now
no credit for free lodging and payday loan?
I was keeping that B&B discovery to myself.... yes, fantastic service and comfort and a 5 star view! Great bank terms too!
It's interesting that the engine didnt have any oil issues,smoke, etc even though the engine was between 5k and near 6500rpm for over 30 seconds! (plus the high RPM on the infield part of the track)
The "chicane" of turns 7 and 8 is also a place where you can PROBABLY not lift either But turn 9 as a decreasing radius none cambered turn is always a bit awkward and doubly so in traffic !! Great job enjoying a new track. So what is your current race weight and corner weights ?
The "chicane" of turns 7 and 8 is also a place where you can PROBABLY not lift either But turn 9 as a decreasing radius none cambered turn is always a bit awkward and doubly so in traffic !! Great job enjoying a new track. So what is your current race weight and corner weights ?
Thanks Jim!
Edit... you are probably right about the chicane... it's not a big time saver, but certainly is a point where you dont need to lift even though you fly through that section at 100 plus tossing the car around., but the following decreasing turn, is kind of like the omega of Willow that scrubs off a lot of speed with adequate room. (that chicane is turn 7-8 and then 9 is the decreasing radius turn, right?)
current race weight is 3000lbs with driver. cornerweight is just about 50.2% front to rear is 53/47%
Excellent drive notwithstanding, if you were to return to that circuit tomorrow what would you do differently to mitigate that tyre wear? Your perception that your DOT rubber has relatively weak sidewalls I find somewhat bizarre- surely the organisers would not let you out on that track without adequate rubber?
That wear pattern looks to me [and probably most others] like a classic lack of adequate camber issue irrespective of what the root cause turns out to be. What disturbs me is that if you can do that to a tyre in 15laps/25 minutes [or whatever the race distance was] the worrisome bit is how far were you from a blowout? Given you have never had this type of problem before the culprit has to be turns1 &/or 2 and Jim warned early on about this circuit being hard on tyres. Both Jim and Dr Bob suggested camber as did I but you seem to dismiss that. Historically you have stated many times you run with 1.8 degrees camber up front and now you state you are actually running 2.2. My comment was that you might need an additional 0.5 degrees on top of whatever you have. On my setup I can pull about 1.2g lateral and I found the front needed 2 degrees in the stock configuration to stop the rubber running onto the shoulder. You are pulling 1.5g. If as you suggest you can run 2 seconds a lap quicker than you were, how on earth are you going to do that unless you change something?
Interestingly your photo of the tyre heeling over suggests to me you did not have sufficient camber for the cornering forces you were generating during that particular session. Now you have been on that circuit for the first time and possibly the first time you have run on those Hillbilly hooch running banks- those are seriously fast bends and presumably are where you were topping out at 155 mph. Have you ever been round a bend at that speed before [as a matter of interest]? Had you known your front tyre was in the state it was on the last lap would you have gone round at full speed or dropped out? You also state that the tyres had even temperature across the tread but how can that possibly be with rubber attrition like that? Whereas a bit more camber might have mitigated the wear, that does not mean your lap times would have improved- indeed such might be less than optimal lap time wise.
To be clear I am not worried about what did or did not happen, my concern is that at the end of the day you should go home to your wife and kids in one piece. Your car is replaceable you are not. 12 or so years ago I went into a solid wall on a bend at half that speed and I do not fancy doing that again. Just make sure you get the best possible post race analysis you can. Once one goes past the rubber layer the situation is basically out of control and failure is something of a random shot thereafter. Would you say you had the situation under control or were you [unintentionally] running on luck at the end?
By all means have fun but above all else stay safe!
Excellent drive notwithstanding, if you were to return to that circuit tomorrow what would you do differently to mitigate that tyre wear? Your perception that your DOT rubber has relatively weak sidewalls I find somewhat bizarre- surely the organisers would not let you out on that track without adequate rubber?
That wear pattern looks to me [and probably most others] like a classic lack of adequate camber issue irrespective of what the root cause turns out to be. What disturbs me is that if you can do that to a tyre in 15laps/25 minutes [or whatever the race distance was] the worrisome bit is how far were you from a blowout? Given you have never had this type of problem before the culprit has to be turns1 &/or 2 and Jim warned early on about this circuit being hard on tyres. Both Jim and Dr Bob suggested camber as did I but you seem to dismiss that. Historically you have stated many times you run with 1.8 degrees camber up front and now you state you are actually running 2.2. My comment was that you might need an additional 0.5 degrees on top of whatever you have. On my setup I can pull about 1.2g lateral and I found the front needed 2 degrees in the stock configuration to stop the rubber running onto the shoulder. You are pulling 1.5g. If as you suggest you can run 2 seconds a lap quicker than you were, how on earth are you going to do that unless you change something?
Interestingly your photo of the tyre heeling over suggests to me you did not have sufficient camber for the cornering forces you were generating during that particular session. Now you have been on that circuit for the first time and possibly the first time you have run on those Hillbilly hooch running banks- those are seriously fast bends and presumably are where you were topping out at 155 mph. Have you ever been round a bend at that speed before [as a matter of interest]? Had you known your front tyre was in the state it was on the last lap would you have gone round at full speed or dropped out? You also state that the tyres had even temperature across the tread but how can that possibly be with rubber attrition like that? Whereas a bit more camber might have mitigated the wear, that does not mean your lap times would have improved- indeed such might be less than optimal lap time wise.
To be clear I am not worried about what did or did not happen, my concern is that at the end of the day you should go home to your wife and kids in one piece. Your car is replaceable you are not. 12 or so years ago I went into a solid wall on a bend at half that speed and I do not fancy doing that again. Just make sure you get the best possible post race analysis you can. Once one goes past the rubber layer the situation is basically out of control and failure is something of a random shot thereafter. Would you say you had the situation under control or were you [unintentionally] running on luck at the end?
By all means have fun but above all else stay safe!
Rgds
Fred
Fred, I apreciate the concern, and am still evaluating everything. as well as others experiences there. ive been racing for 20 years, and been around the best in the business and you just dont see my car having any issues and there is a reason for that.
you are assuming all sorts of things, so let me clarify.
i have a ball park alingment that i start with . it was about 1.8 degrees 5-6 years ago and with small adjustments to ride height, that aligment has changed a little to 2.2 degrees.
you dont , again, understand why the tire wear as it does under such harsh conditions. so say that .5 degree of camber would solve that problem, is a guess. its a function of balance and speed, and tire action. the sidewalls are not as stiff as a real race slick (like a Hoosier R100), so at high g loadings, you will have a lot of tire movement and wear if sustained. Laguna isNOT sustained as you can see and i experience NO wear on the shoulder, but if i hit the corkscrew at 150mph and held that g loading for 20 seconds, it would be a different story.
one thing i can do is to increase preasure on that side, but making a half of degree of additional camber would hurt braking performance and handling on other parts of the track for which i am not willing to make a sacrafice. this is race engineering at its simplist.
Lets be clear.... the tires i used in the race and in practice and qualifying had plenty of rubber. i had one tire that had a wear pattern due to extreme conditions. to contrast this, the 911s with engines in the back running these types of speeds and times, get the rear tirre to cord on its outside edge. same condition, same reason, just different tire. (front engine vs rear engine). part of the reason i get the great life out of my tires that i do, is that i am meticulous about tire information management, with tire temps and wear patterns. they again were perfect over the weekend, with the exception of the rear inside tire that was hotter in the center, meaning the higher pressures recommended needed to be adjusted to normal on the driver side. again, that type of wear is not indicative of a problem as you suggest. i have had camber and toe that were off before due to impact, and the wear pattern for a .5 degree of camber is is the outer third (or inner) third wears flat. stressing the tire in high g turns, and normally, im near 1.5g and in this instance its more like 2g with the compression and downforce. the tire , naturallly can roll over and put pressure only on its sidewall, especially if the tire is NEW or NEW'ish" having a lot of grip,makes more tire movement.
did you see and watch the video?? watch the video of the Laguna seca fender cam. look at the pics... this is normal.
yes, i expect to be faster. i will do this for two simple reasons. (having nothing to do with settings) WOT , going into turn 1-2, (no lift) and no lift through the chicane 7-8. the times im posted, even being my fist time, is right up there with the fastest cars in this kind of class for POC (GT3) with the same power to weight.
to answer your questions, that wear was slight. it takes a while before it gets critical for the tire to lose air , or blow out. that was the beginning. certainly i woudlnt go out on that tire on the outside of the car for another session, it was perfect , except for that outside edge. and no cords were even touched. i would put even more pressure in that tire and that woudl keep the tire from rolloing over on its shoulder as much. this si why the pit temps were perfect. for 10 seconds a lap, it rolls over and scrubs the outside shoulder and no where else.
again, i appreciate the concern. it was mine as well. racing is NOT that important to have a mishap and cause me to hurt myself and not go home ot my family. i take it very seriously. remember i did run all tires that were purchased by me.. one set , qual and practice were older and after the 1st race, showed the exact same wear. because they were older , i didnt think the newish tires would get as bad and they did. i ran faster and harder and the wear appeared in the same spot.. you also have to understand the bump steer vs your car. im at 108mm ride height. at that level the bump-steer gives HUGE camber changes which actaully help my outside compressed tire. and yes, ive experienced this kind of turning speed, at the fastest track in the "west". willow springs. not the same problem... why? because it is not banked . in fact, an opposite problem occurs.. .the inside edge of the inside tire wears due to scrubbing. (caused by extreme bump steer) but , the tire on the ouside, with less g forces, doesnt rollover on the shoulder at 1.5 gs.
just a few bits of info to help you understand the factors involved.
An excellent post. The only thing about your setup that I feel I do not understand is why you do not have more bump steer issues than you seemingly do given your ride height- not many people can look out of their 928 side windows and look up to see a snake's belly! I run at around 150mm, This is lower than most 928 owners will ever see by choice but with stiffer springs it is not a problem on our very good roads over here. At your ride height even at rest the lower arm must be about horizontal before any compression if not a little above horizontal- have you fitted any anti bump-steer kit? I am also a bit surprised that you run the same camber front and rear- at my level of incompetence I find the rear needs less camber.
I can well understand why some folks want to minimise the camber used and if experience suggests that dialling in more camber to accommodate the banking wear issue just does not work or costs lap time elsewhere then you simply have to understand the rate of attrition and be prepared to bin a new tyre after one race outing. As you say some of those chaps you were running with dump their rubber after one outing and thus dumpster mongrels like yourself can go home with a grin on their face. Your perception that the front outer wear was "minimal" baffles me- from my perspective that tyre was borderline marginal.
First time I ran my wider/stickier rubber I was running up on the sidewalls but that was with 1 degree of camber [it was not what I wanted rather it was all I could get on one side at the time]. Modern stock rubber requires that. Pulling 1.2G with my 265 fronts I eventually concluded the car needed 2.0 degrees- the front brace seemed to lower that by 0.5 degrees thus I currently run 1.5 degrees on the road- no uneven wear issues and with lower camber the braking is better. Start pulling 1.5G's and that goes out the window then the question is what is flexing?
Finally, when it comes to tyre temperatures, Formula 1 technology for some years permits real time monitoring across the tread and they even have infra red cameras showing how temperatures change dynamically. If you have seen this you will understand that tyre temperatures change rapidly going from minimal to maximum to minimal within a single bend. When one knows this it makes temperature checks in the pits look somewhat silly. They help of course and do give some clues but to my mind such do not give you a deep understanding of what is actually going on two minutes after the fact.
Thanks Fred. Still a few things need to be described to be more clear. once you understand them, you will get the entire picture. you speak of "bump steer problems" and, the only problem you can have , is enhanced camber change with compression (actually good for race car)..... fine for street, because there is no excessive compression, so the only draw back is the opposite side not increasing camber with droop, but loosing camber, and thus toe'ing out as well. this can create a scrubbing inside edge of the drooping tire, but if you are puling enough g's the tire is barely on the surface, so .....no issue. however, as the speed goes up like turn 8 at Willows, its toed out at 1.5g, and the speed is so great, it acts like a lathe and scrubs off the inside edge of the drooping tire. so yes, at willow, i sacrifice a tire for the race and a qualifying... same at Cal speedway. collateral damage. its predictable..... the good news is the cal speed way tire, can be easily just put in the rear where the shoulder wear area is put on the inside rear and never sees pavement again.. (all you get on the rears with 2 degrees camber is "pickup" and virtually no wear.) i might be able to change that with softer rear springs, but then there is other sacrifices. (another story all together)
so yes, the wear was minimal , so dont be "baffleled" due to the fact that it was so localized , and can be swapped to the rear and flipped directionally. the picture of the corded tire was my very used set, after Race1, Race 2 and warm up session where i went considerably faster, showed this wear, but slightly less after the final rest. (cords not showing, but shoulder gone)...... in thinking about it, the real only mod would be higher pressure, which might solve that problem however, there are more forces on that part of the tire naturally,... very difficult to solve this issue with camber alone.
keep in mind as the suspension is compressed, the outside tire on the turn is compressed, it toes out and due to bump-steer, desensitizes steering but it also increases camber dramatically, and even more so with high bump steer "issues", due to extreme low ride height.
you ask what is flexing? nothing is flexing to speak of... what is seen at the higher g loading, is the increased camber due to the natural action of the A-Arm geometry. and this is enhanced as you lower the car. which is GREAT for a race car.with a stiff suspension. so many factors you need to consider. observation is not causation. there is no flexing as you can see from the wheel-cam video .5 degree would be near .25" and you would be able to see that kind of movement. (for reference, about 1" is 2.5 degrees camber)..... you can see the tire tilt in near that much as its compressed down the corkscrew. (see pictures above)
its not going POSITIVE , as you suggest with chassis flex, its going negative and you can see it referenced to the fender .
regarding tire temps, of course i understand how fast things cool off . that was my point. i have even temp wear and by design, its progressive from inside to out. the outers wear, but why not the higher temps there?? because as you mention and as the IR video shows, this temp rise and wear happens on a very short time section of the track ( but a great distance). it all adds up and there is no surprises.
All being taken into consideration. again, to solve the outer wear issue on the specifica area ( shoulder), there are 3 solutions. 3 more degrees of camber.. (not possible), increase pressure. ... might help , but i dont expect it to solve the issue.... or soften the front spring, this would allow more compression of the wheel and increase natural bumpsteer driven camber.... there is also a driver induced issue, im driving down near the apron, where the fastest car of the day was not going down as low as i was.... (out of concern to really hit the apex line)... this increases distance, but allows you to carry MUCH more speed and subsequently, less outer shoulder wear..
Originally Posted by FredR
Mark,
An excellent post. The only thing about your setup that I feel I do not understand is why you do not have more bump steer issues than you seemingly do given your ride height- not many people can look out of their 928 side windows and look up to see a snake's belly! I run at around 150mm, This is lower than most 928 owners will ever see by choice but with stiffer springs it is not a problem on our very good roads over here. At your ride height even at rest the lower arm must be about horizontal before any compression if not a little above horizontal- have you fitted any anti bump-steer kit? I am also a bit surprised that you run the same camber front and rear- at my level of incompetence I find the rear needs less camber.
I can well understand why some folks want to minimise the camber used and if experience suggests that dialling in more camber to accommodate the banking wear issue just does not work or costs lap time elsewhere then you simply have to understand the rate of attrition and be prepared to bin a new tyre after one race outing. As you say some of those chaps you were running with dump their rubber after one outing and thus dumpster mongrels like yourself can go home with a grin on their face. Your perception that the front outer wear was "minimal" baffles me- from my perspective that tyre was borderline marginal.
First time I ran my wider/stickier rubber I was running up on the sidewalls but that was with 1 degree of camber [it was not what I wanted rather it was all I could get on one side at the time]. Modern stock rubber requires that. Pulling 1.2G with my 265 fronts I eventually concluded the car needed 2.0 degrees- the front brace seemed to lower that by 0.5 degrees thus I currently run 1.5 degrees on the road- no uneven wear issues and with lower camber the braking is better. Start pulling 1.5G's and that goes out the window then the question is what is flexing?
Finally, when it comes to tyre temperatures, Formula 1 technology for some years permits real time monitoring across the tread and they even have infra red cameras showing how temperatures change dynamically. If you have seen this you will understand that tyre temperatures change rapidly going from minimal to maximum to minimal within a single bend. When one knows this it makes temperature checks in the pits look somewhat silly. They help of course and do give some clues but to my mind such do not give you a deep understanding of what is actually going on two minutes after the fact.https://cimg5.ibsrv.net/gimg/rennlis...f1339b3850.jpg
Are you running with stock [unreinforced] anti roll bar mounts?
The dynamics of what happens to the suspension under those extreme conditions is complex and the banking is yet another additional factor complicating the issue. With a car lowered to the extent yours is it just complicates things further. As with anything to do with the suspension system for every tweak that adjusts something positively there is invariably a negative impact elsewhere and the aim is to find an optimal set of adjustments to give the best overall result. Camber is an important component but at the end of the day it is just one of a number of variables. Trying to find the optimal recipe for every circuit is difficult to say the least but the results speak for themselves and good post race analysis will hopefully better prepare you for the next time you there.
Buying a rich man's toy, paying someone to prepare it for the track with bottomless accounts and plonking a spoilt brat in it to drive mid pack is what it is [all too often] but taking a relic, spending next to nothing on it and bringing it home in a credible position that is quite something in my books at least.
To answer your first question.. no.. no reinforcements on the swaybar mounts. i did on the Holbert car, but i had two problems here. one, the bolt tore from the subframe mount. so, we welded a bar across it to keep that from happening. next, i high sided the car on a birm at T-hill and later the swaybar mount tore from the chassis. had to weld it back . the new chassis is stock with no mods and has lasted 75hoursof racing, and extreme g loading on very large slicks. ive gone to a slightly lower roll bar setting as you can see, which tended to make the car less pushy. with no bar (when it breaks) the car will roll and lift the rear inside tire, making it spin wildly like an open diff (i know this when a bracket bolt came loose) too much bar, and the forces are greater, to break the mount, but just right, and the car handles better and the brackets can withstand the forces. NOW, on a stock car with softer springs, all bets are off. most of your anti roll forces are absorbed by the bar and its mounts and thats when thing rip and tear. remember, this these are things learned in 20 years of racing this chassis!
Actually, the lowering of the car makes things better and doesnt complicate the reactions of the chassis and components the reason is , that as you lower the car, stiffen the car, and damp the car, many of the ill effects of a stock car are reduced tremendously. (with a stock set up car, comes body roll comes alignment change, ) Many things in race car dymanics, deal with all sorts of adverse conditions. damping, body roll, balance,weight transfer, etc. in this situation with lowering and stiffening/damping) many of the variables are taken out. With high constant speed, and the banking, we are dealing with maybe a quarter of the race car dynamic factors. we are only dealing with near static rate compression and resultant camber/toe changes.
F1 teams look at IR temp footage, shock data, g loading etc. but in the end, the result is how the car feels and what the wear indicators look like. (the tires). Knowing how a tire responds in extreme conditions is key here. this is something that experience and visual data (pictures, video , result of forces in form of wear) So, in the end, my assessment of tire wear and causes is going to be very close to reality.
we know with a lowered chassis bump steer is exacerbated...which is a good thing in this situation. it means with extreme compression, i have an accelerated camber setting which is good. this is a great design of the 928 front and rear suspension system. with it, comes extreme toe changes, which are not a concern for Auto club speedway, because with the banking , there is minimal body roll, so both wheels in front compress near the same, even under high lateral g loading conditions. (it would have been interesting to put a digital scale under my body, to see the positive gs) . again at a track like willow springs, the opposite wear patterns occur. knowing the difference is key here for adjustments and setting the the car up safely. at Auto club speedway, the high g loading, and positive gs crush the outside front tire and lots of shoulder only wear. i suspect it is the sacraficial lamb of the race weekend... but i think i can fix it 3 ways, higher pressure ( i was much lower than the racing list community said to be at... going on fellow racer settings at the track that day as well as what the HOOSIER owner recommended at this track) , go to a full racing slick with much stiffer sidewalls and possibly a stiffer swaybar setting.
Did you see my times? Have you compared them to similar cars with exact same HP/weight on same tires in a same Porsche club class? if you do, you can see that a top, reigning championship porsche team, with a local top driver, with seemingly unlimited budget, ran this same circuit and was only within a second faster.... and they are local to the track with a car 25 years newer designed by one of the top teams.... so, how is it, i can show up with my relec, with 100 hours of pure racing on the engine, and be where i am on the track in 3 sessions? Sure i would like to take all the credit, but the 928 is an amazing platform that has so many things built into it by design, that we take for granted how adaptable and easy it is of a car to driver and modify for racing. (even with most of the bushings on the car being near 30 years old!)
one of the things ive found, is i dont tend to set up the car for different tracks, ive set it up to do what it does best, with the best wear patterns. (so , its not totally optimal) But, i understand where it is performing best and drive it on any race track taking advantage of what it does best. it might mean it might not perform best in certain sections that i could improve, but because it does so well in others, naturally, it makes up for it, AND gives me the best wear / performance ratio. Just like gearing... sure, i could change transmissions for ever track, but i dont... I make the best of it and make sure im using the engine's max potential where ever i can with the ratios i have. It might be optimal for one track, and not for another, but i drive in a way to minimize the difference..
by the way.. look at a picuture i just took. look at the lower Aarm look at the tie rod angle.... you think under 4" of upward tire movement, that the forces are acting in a way that can induce any moment on the chassis frame rail? no way that you can get the frame rail to move 1/2" with 1 or 1.5g, let alone 2g lateral forces.... with real life angles, it just cant likely happen.
Originally Posted by FredR
Are you running with stock [unreinforced] anti roll bar mounts?
The dynamics of what happens to the suspension under those extreme conditions is complex and the banking is yet another additional factor complicating the issue. With a car lowered to the extent yours is it just complicates things further. As with anything to do with the suspension system for every tweak that adjusts something positively there is invariably a negative impact elsewhere and the aim is to find an optimal set of adjustments to give the best overall result. Camber is an important component but at the end of the day it is just one of a number of variables. Trying to find the optimal recipe for every circuit is difficult to say the least but the results speak for themselves and good post race analysis will hopefully better prepare you for the next time you there.
Buying a rich man's toy, paying someone to prepare it for the track with bottomless accounts and plonking a spoilt brat in it to drive mid pack is what it is [all too often] but taking a relic, spending next to nothing on it and bringing it home in a credible position that is quite something in my books at least.
You do not turn up at an event like that and do as well as you did by chance/luck. Having a sound platform is vital but so is the way it is being driven. If you were in a top flight racing machine it is a fair bet you would make a very good account of yourself.
You do not turn up at an event like that and do as well as you did by chance/luck. Having a sound platform is vital but so is the way it is being driven. If you were in a top flight racing machine it is a fair bet you would make a very good account of yourself.
Chance favours the prepared mind!
Thanks! I guess we can make some of our own luck...... But the star of this show is the car. I lost track of how many people came by to check out the loley 928 .such a cool car , i think! Just a quart of oil and gas all weekend. remarkable!
Here is the 1st race (with the head wind) and the last few laps of the second day's race. dont think it came though on the last post
Greg, and the other "928 oiling issue specialists",
there was talk awhile back regards to the high RPM issues of oil being pumped into the heads and not returning to the pan, thus starving the engine for oil feeding the pump (via the pickup)
what was the net net of that discussion. i couldnt find the discussion. as you can see on the video, i keep the RPM from the moment i exit the final turn, i run out to 6000rpm and keep it there and up to 6500rpm for about 30 seconds, PLUS putting about 2 g of lateral forces as well as some positive gs. the lateral gs FAR exceed what the 928 sees at Willow springs , not only in duration , but in intensity. 2g vs 1.5g) maybe the positive Gs are helping the return of the oil from the heads if they are being "overpumped"
what was the limit of time at 6500rpm before the pan was starved. i seemed to remember, "30 seconds" being the limit.. true?
Greg, and the other "928 oiling issue specialists",
there was talk awhile back regards to the high RPM issues of oil being pumped into the heads and not returning to the pan, thus starving the engine for oil feeding the pump (via the pickup)
Oh boy. That's a big topic! Can you narrow down what you are looking for information about? Info on crank scraper/windage trays? Crankcase venting with oil separator to return the oil back to the crankcase? Or controlling the oil flow to the heads for racing?
This might be best as its own thread, but then again, its pretty much a race-only issue.
01-20-2018, 04:23 AM
But turn 9 as a decreasing radius none cambered turn is always a bit awkward and doubly so in traffic !! Great job enjoying a new track. So what is your current race weight and corner weights ?
