Making IRS work without going to mendeola truetrack... :)
What have you done to IRS suspension and what have been results?
At the moment i have: -944 aluarms widening the track -Remmele uniball kit -18mm swaybar -QA1 coilovers. -Urethane bushings According to Mendeola, their truetrack much more better, i dont doubt that its good, but i really want to try with 944 aluarms and rest. Any problems with Camber? I'v been considering Marco Mansi camber adjusting bolts and hard POM bushings at inner pivots. |
I'm very wary of the Mendeola rear suspension design. The system uses design elements like highly stressed fasteners in single shear, loads applied to the middle of tubes, and pre-buckled tubing. Any design book, whether an engineering text or those for us 'layman', will caution against these errors. Carroll Smith (Engineer to win) goes much further then caution!
http://images.thesamba.com/vw/gallery/pix/910793.jpg I asked Mendeola about the issues I saw and was basically given an answer that "the vehicle will never create loads large enough for it to be a problem". Which, considering some of the track monsters here, I'm not very confident of. I would think that if you were to completely redesign the rear suspension of a vehicle, you would do so without including what have been accepted as "major engineering 'errors'". The system may very well be overbuilt for a Volkswagen, maybe even a track-day GL monster, but if I can see errors in the basic design I lose all confidence in it's claims. It should be said, however, that the front system from Mendeola (for the standard beetles) has no major visible issues. My only complaint (from a purely performance perspective) is the choice of ball joints over rose ends. But that is an acceptable downgrade. -Dave |
I hear you Dave.
I'am also still wondering what problem they wanted to solve there? Same goes for most creative rear suspension set-ups. IRS is good enough for 911's and 944's which raced up to huge hp with it in heavy cars on real racetracks in real competitive races. The low 8 second 900+ hp Skinne beetle uses a basically stock IRS set-up. Coil-over mandatory though and a real upgrade, but thats easy and you already got that. Other then that, what/why does it need changing? I would focus on the front end mostly. Not a fan of urethane bushings, so I used some parts from porsche 944 performance shops, can't remember their names atm. Pics of both sides of the pivot point upgrades are still in my thread somewhere probably. |
I had an interesting technical conversation at thesamba about Truetrack rear suspension. But i am not an expert, just curious how different suspensions work and how they are built. My painter/bodyman is rally and trackdriver, and he has sometimes good advice about suspension. I know those 944 arm upgrades, finnish 9products sells also them. I know, there is not anymore much to do for rear suspension, i have almost every part for upgrading it. s
http://www.thesamba.com/vw/forum/vie...=asc&start=900 As you know, i did made the uniball kit for Volksmeister's bug. Quote:
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some may know i race my b/j car in a busy uk saloon car class, all serious race series have regulations governing suspension and its attachment, or what is known in racing as 'the pickup points', in many series these have to be retained. for my purposes, i chose steel a arms over the ally versions for many reasons, one being it gives me more scope to modify the setup and brace the arms against flexing with applied side loads. the arms are flipped l to r to improve the foot print and tyre life, with the lower shock mount removed and a new mount fabricated onto the top of the arm and fabricated in such a way as to brace the arm against flexing in the turns, just tightening the shock bolts helps brace the arm, an added gusset completes the job, the upper mounts are moved inboard and tied into the roll cage, pic shows them halfway through the conversion, ive clearanced enough to allow for coil overs should i desire them, tho my mantra with this car is to keep as near 'factory' as possible, and very well its going too, the setup in the photo above for instance, would be damaged if not torn off where i race, either on the track side kerbing, which we use hard, or from wheel to wheel contact just aiming you into a mashals post, its common enough, adjust-ability is all very well, but you better be good at your job, or mine will spank you while you play around and get lost in your little set up book of rules, the factory eqipment is damn good to start with, if you cant go quick with it, you wont go quick with more complex setup needs, just my views any way, i will post some pics when i can sort out new photo bucket. best regards Johnny.
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i still run a pretty much stock irs rear end on my 1303 race car. 944 torsion bars and spring plates along with steel arms [not flipped] none adjustable kyb shocks and a 944 anti roll bar.
theres enough adjustment in it to set it up and when i was running 9x15 rear rims with 240/540/15 slicks i had even tyre temps across the tyre. Its even better now i have gone to a narrow tyre and rim [7.5x17 with a 210/640/17 tyre] as i can get more heat into the tyre quicker. the stock system works and works well plus its pretty light and easy to replace should you bend somthing. |
I guess I'll toss in my $.02 here
I would estimate with my 245/45-17 & 275/40-17 slicks and aero, my race bug generates some of the highest lateral loads of the circuit style bugs out there. I went with 944T aluminum arms mainly for the brake and track width upgrades. I swapped out for later 944T s2 arms for wheel speed censors and to correct a bent arm after body contact. I've been pretty happy with my setup over the last 10 years, but it does need some help. Right now I've got: 944t S2 alu. arms qa-1 single adjustable shocks 550# springs 17mm rear sway bar, (topline I think?) urethane bushings everywhere mendeola stiffy kafer brace 944/911 camber/toe adjustment bolts, also serve as sway bar pick up point 944 spring plates What i have now is perfect for the street (except the spring rate, that's a bit much) but still a bit too compliant for track use. -I want to swap out the 944 spring plates for some 935 style -slighty heavier 600# springs -swap shocks for double (or triple $$$) adjustable units Not too much actually, I've been tuning my setup for a long time and I'm pretty close to having it dialed. Finishing around the top 10-15 in raw times out of 200 runners proves that my bug can hold it's own. Does that mean you need a mendeola rear suspension? Yes and no. I think the mendeola kafer brace is one of the best out there and it's a must have regardless of what you decide. If you want to buy a kit that looks pretty sick, is truly bolt-on, and can take different brake options then it's hard to go wrong with the truetrack. I don't think the mendeola engineering is off base, and even if they were installed on my race bug, I don't think the rear arms would bend or crack under race loads. I do like their adjustable outer pivot for suspension tweaks, and even in single shear I don't think you need to worry about it, though I would still safety wire the thing. If you decide to go 944 aluminum instead you'll have to factor in the cost for arms, bushings, brakes, wheels, e-brake adapters, kafer brace, sway bar and so on. It might not be as good a deal as you think. Upgrading the stock steel arms with just bolt on items, coil overs/upgraded torsion bars, kafer brace, sway bar, and bushings will go farther than most folks have given credit. |
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17mm is not that much imo. |
There are 2 schools of thought on this:
Heavier springs, with lighter sways to fine tune or Lighter springs, with heavier sways but more reliance on shocks to tune For autox and hill climbs where the corners come at you fast, you want to keep weight transfer minimal so the car can react faster. I've found the best way to do this is with heavier springs, so they do most of the work and then you can fine tune it with a sway bar. Weaker springs won't be able to deal with high cornering loads slick tires can generate even with a ridiculously large sway bar. You'll end up lifting a wheel and losing 1/4 of your grip. With both setups you have to tune your shocks accordingly or it's all for nought. |
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