Pinpoint suspension failure / incorrect geometries.

Discussion in 'Corner Carver Racing Tech Discussion' started by Macman45, Jul 2, 2021.

  1. eighty6gt

    eighty6gt forum member

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    my car doesn't lag. EPAS, stock swaybar, 427R front springs, and old, dry rotten, cracked down in the treads NT555 (not even G2's!) I bought from @Pentalab years ago. 255/45R18's on 18x9 IIRC.
     
  2. Macman45

    Macman45 Resident Geriatric

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    EPAS or stock 05-09 hydraulic? Yeah there’s something wrong and I think it’s a bushing. Gotta crawl under there and check everything
     
  3. eighty6gt

    eighty6gt forum member

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    EPAS i said!!!!
     
  4. Macman45

    Macman45 Resident Geriatric

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    OK!!!!

    ....then that doesn’t apply to me as I don’t have EPAS. Apples to oranges
     
    eighty6gt likes this.
  5. Pentalab

    Pentalab forum member

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    How do u like the EPAS vs the hydraulic the car came with ? Where does the software for the EPAS reside ?
     
  6. eighty6gt

    eighty6gt forum member

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    Software is In the rack. No way to change settings but I always liked "comfort" the default mode in the GT's anyway. Sport mode was just stiffer.

    It is a 10000% improvement because I got to throw away the hydraulics, pump, reservoir and I can run a normalish length belt from the parts store with the blower.
     
  7. Pentalab

    Pentalab forum member

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    I bought those Nitto-555's (255-45-18) fronts and the mating Nitto-555 (275-40-18) rears in the summer of 2011. I still have the 275-40-18's (on 18 x 10 rims)..and checked both of em today. Pristine shape, no dry rot, cracks or anything else. Perfect between treads, and plenty of wear left. BUT I only used em between the last week of April...till end of sept, or a bit into Oct. Stored in heated basement in the fall /winter. I suspect that if you have them exposed to -30 C outside temps, that could create issues. They were touted as...'summertime tires'. I used the oem tires + rims in the fall / winter. These days I use NITTO Motivo's in the fall/ winter. Spring + summer I use MPSS in 305-35-19 for rears...and Nitto NT-555's in 285-40-18 for fronts. I'm not really impressed with the MPSS, but they should really be on a 11" wide rim, not the 19x10 that I'm using.
     
  8. eighty6gt

    eighty6gt forum member

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    Omg, 2011... I'm going to die

    Good thing I took the car off the road.

    I need all new tyres. Rear tire size/fit is pretty annoying now with 18x10's. Will be dr's $$$... fronts won't match. Maybe just nitto tires again... they function. Cheaper than Michelins. Maybe China is making tires in this size by now, get some from ali express....
     
  9. Pentalab

    Pentalab forum member

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    The Nitto Motivo's are superb in the rain, but semi useless in the snow. Those firestone Indy 500's, or whatever they are called appear to be the bomb for the price. Gasoline here is priced into the stratosphere. $1.97 per litre...for Chevron 94. $90.00 to fill up from a 1/4 tank..and shit gas mileage....20 litres per 100 km around town.
     
  10. Norm Peterson

    Norm Peterson corner barstool sitter

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    Approximate conversion from L/km to mpg is about 235 divided by the L/km number . . . so yeah, nothing to be writing home about.


    Norm
     
  11. eighty6gt

    eighty6gt forum member

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    I get 9 miles per gallon

    my car is more a curio now, we will see how my career and money situation develop, I don't plan on buying any other vehicles, there's nobody who wishes to buy it, if I have some play money down the road I will keep screwing around with it and it will be parked most of the time, but occasionally dusted off and taken out to be embarrassed in performance by a tin plated truck that looks like dr. suess invented it....
     
  12. Macman45

    Macman45 Resident Geriatric

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    Alright this thread got real de-railed and somehow moved out of chat but anyways, I’ve solved the problem.

    blown struts. Both were leaking severely and went totally flat while the car was in storage. New FRPP struts and the body roll is nonexistent and steering is very responsible.

    sometimes the obvious solution is the right one. And I love the Nittos on it. Perform great on dry pavement which is all the car sees.
     
  13. Frankief28

    Frankief28 Junior Member

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    Quick question I have w
    2012 GT with aluminum driveshaft pan hand bar adjustable rear shocks strut brace both front snd back I had car aligned and wheels balanced got 255/55/19 front rear 285/35/19 rear I put rear tires used but good tread on them problem is at speed over 90 mph car starts vibrating like I’m going over small speed bump no vibration in steering wheel had all tires balance already I just don’t know why he’ll it’s doing it any suggestions?
     
  14. Pentalab

    Pentalab forum member

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    Yes, and it gets worse. Our gallon is 20% bigger than a us gallon.
     
  15. Norm Peterson

    Norm Peterson corner barstool sitter

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    So 195 divided by L/100 km when using UK gallons . . . sure makes the mpg number look worse . . .


    Norm
     
  16. larry Stark

    larry Stark Junior Member

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    I beg to differ. When you lower car LCA inner pivot is below ball joint. As suspension compresses arc of ball joint travel will add positive camber
     
  17. Norm Peterson

    Norm Peterson corner barstool sitter

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    Not necessarily.

    Camber only starts going in the positive direction after the LCA arc starts running inside the strut axis - after the LCA makes a 90° angle with the strut axis. That's when it starts pulling the ball joint inward, not before. Based on measurements I made of my car at stock height, that would take over 2.5" of suspension lowering, which would put you almost always on the bump stops . . . meaning excursion into positive camber gain would be minimal anyway.

    The strut axis would need to be running essentially vertical as seen in front view for your description to work as you think. But it's sloped inward toward the top at about 15° away from the vertical, has to for tire clearance with any sane MacStrut geometry.

    2D MacStrut geometry at inflection point.jpg


    Norm
     
  18. Vorshlag-Fair

    Vorshlag-Fair Official Site Vendor Official Vendor

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    Some observations.

    1. Like many have said - don't just throw money and parts at the car. Get a real alignment, scan in the sheet, post it up here. Then ditch the 2" lowering springs - that is causing problems.

    [​IMG]

    2. NOBODY READING THIS POST NEEDS A BUMP STEER KIT. There, I said it. That is for cars lowered a TREMENDOUS amount, more than the Bolt On Billy lowering springs, more than almost any coilover kit. This is something people buy simply because shops sell these kits. The car above had no bump steer correction even lowered 3" on proper coilovers (AST, Moton, and MCS kits were run on this car) - 2" lower on the dampers/springs, 1" lower on tire height. It didn't have any bump steer. That is mostly internet tall tales.

    [​IMG]

    3. Nitto tires are garbage. GARBAGE. Nobody serious in competition uses Nitto or Toyo tires. The latter is required in some Spec classes because Toyo BOUGHT INTO THOSE SERIES. I say this as an idiot who also bought and tried to compete on Nitto tires (above) and having wasted money on Toyo tires in the past, too.

    These two brands tend to have terrible performance, terrible wear, and are not competitive in any form of timed Motorsport. They are popular because: A) they make some funky sizes B) Are cheap C) Drifters D) Hard parkers.

    4. Lowering any S197 TWO INCHES on OEM length struts and shocks introduces a lot of BAD things, namely - RUNNING OUT OF BUMP TRAVEL. This is due to the fact that the lowering amount automatically reduces suspension travel in the BUMP direction when you leave the shock and strut lengths stock.

    [​IMG]

    This is why all coilover struts/shocks are SHORTER than the OEM lengths (typically by 1 to 2 inches). This is no accident. The shorter length allows for more bump travel, while it will give you less total suspension travel. We have helped shock makers from 4 companies design new shock/strut setups for over 20 different chassis (the 6th gen Camaro strut from MCS above was 1" shorter than stock, but with the bottom of the strut housing pushed below the stock brackets we gained that all back) - this is literally what I do for a living.

    No bolt-on part will fix this issue on the OPs car, short of tossing all of that FRPP stuff in the trash and starting over with properly designed suspension.

    I am honestly not trying to pick on the OP, but he did ask this in the corner carvers / racing tech sub-form. Which means you get answers from racers and suspension designers... like me. :)

    Cheers!
     
  19. Juice

    Juice forum member

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    Nitto NT01s and Toyo Proxes R888Rs are far from garbage. May not be up to 'racer's' spec, but they are more than capable HPDE tires.
    Sorry Terry, but HPDE drivers are not rich ppl. We need to do this HOBBY as inexpensivly as possible.
     
  20. Norm Peterson

    Norm Peterson corner barstool sitter

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    Competition is still pretty serious even at the autocross and road course Time Trial levels. Where tire and other contingencies may be at stake.

    Never mind that if you need to consider suitability for running HPDE in the wet, neither NT01s nor R888Rs belong on your "go-to" list.


    Norm
     
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