But changing the length of that link affects directly the parallelism of the lower Subaru lateral links and when those aren't parallel, it apparently causes a lot of driving issues on the rear end.
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But changing the length of that link affects directly the parallelism of the lower Subaru lateral links and when those aren't parallel, it apparently causes a lot of driving issues on the rear end.
Frank
818 chassis #181 powered by a '93 VW VR6 Turbo GT3582R
Go-karted Aug 5, 2016 - Then May 19+21, 2017
Tracked May 27/July 26, 2017
Build time before being driveable on Sep 27, 2019: over 6000h
Build Completed Winter 2021
You are correct Frank, only it's just one driving issue that it causes: bump steer.
The lower lateral links not being parallel causes toe changes along suspension travel. You can set them very close to parallel using a ruler or a digital angle gauge, but until you test it and adjust it with a bumpsteer gauge, it may have more bumpsteer than ideal.
It is quite impossible to eliminate all bump steer in these cases with the factory suspension setup. 0 is the target but it is unachievable, and besides, some bump steer can be beneficial if it is in the right direction. Toe out at the front under compression would be a good thing if not too much. Toe in at rear under compression is also desirable, provided it is not extreme. These two together would produce slight understeer in corners. Not my opinion, its all in the book. Not the FFR book either.
Well, I guess I am going to have to experience it first! I am hopeful that the stock suspension set-up is very driveable, but if bump steer is an issue then I will be forced to learn something new to improve it. This 818 build has been very educational so far!
Ben,
The character of the car improved and became a joy to drive after eliminating much of the bump steer that my R had. I will have to look at my notes but if I recall correctly I was seeing .250+ toe out on each front and at least that on the rear, now I have around .010 out on the front and .007 in on the rear. Bumpsteering the car is not that hard and can be done with a couple a flat plates clamped to the rotor, a floor or bottle jack and a dial indicator on a fixed stand IMO it is well worth the time. The first corner will take the longest, it is down hill from there. Check out Bob's build thread he and Michael used what they had in the shop and transformed the car (I believe that is what he said) Their car was like mine when I go karted, nervous, dirty and uncomfortable.
I would suggest doing it before installing the body, the job is really not that much harder with the body installed but you just are working in a tighter space.
Hear is a couple of articles and instructions.
http://www.hotrod.com/articles/ctrp-...eer-explained/
http://www.longacreracing.com/instru...0Steer%20Gauge
http://www.irvansmith.com/scart/arti...articles_id=11
I had the same experience. The 818 wasn't even fun to drive before fixing bump steer. It was a real handful and pretty scary, darting to the left and the right over every tiny bump in the road, and the same when applying the brakes. The bump steer fix was the best mod I have made to the car... well maybe it was second to re-routing the exhaust so I wasn't inhaling it while driving.
What method do you use to adjust the front bump steer? Are you adjusting the rack height through shims/bushings or spacing the tie rod end at the steering arm? If you are adjusting the tie rod end at the steering arm, did you replace the end links with rod ends? Thanks for your insight!
~ Mark
818C S/N 429ES: Start Date 1 September 2016
2001 NB Miata LS3 V8 440 rwhp
2004 Miata MazdaSpeed Factory Turbo
Tony Nadalin
2018 SOVREN Big Bore Champion
2015 SCCA Oregon Region VP3 Champion
2012 ICSCC ITE Class Champion
FFR MkII Challenge Car, Spec Racer, Street Legal, SCCA, ICSCC and NASA Racing
818R Build in progress
You can buy a kit from Baer Brakes. It's like $170 or so. Has everything you need except for a big 5/8" bolt and lock nut that you replace the spindle with. Check Plavan's build thread for instructions on drilling out the spindle. The Baer kit has a rod end for the tie rod. You just use spacer shims and replace the taper bolt with a 5/8" bolt. For my S at 4.5" ride height, the magic number was 46 or 47mm of shims. You can also buy shims online. I have some info in my build thread too.
FFR also has a PDF R supplement that has recommendations for a starting point for R ride height. Looks like Frank, Bob and a few others will have a good starting point of an S.
we must have gotten really lucky, because we have no bump steer that we can feel. Watch the steering input in our last video test session, I'm sure it will all turn to **** when we lower the car another inch in the front.....
Tony, thanks for your work in finding these parts and process. I found the following in your build thread and posting again so I can find them in the future and for other's reference:
Here are the parts I sourced out to get a bump steer kit that would work, height wise and adjustable
http://www.speedwaymotors.com/Adjust...=91636055PINTO
http://www.speedwaymotors.com/Search...+Inch+x+1+Inch
http://www.racecraft.com/index.php?m...result&search_ in_description=0&keyword=RC21083&x=21&y=8
http://steinjager.com/shop/index.php...earch=J0041201
~ Mark
818C S/N 429ES: Start Date 1 September 2016
2001 NB Miata LS3 V8 440 rwhp
2004 Miata MazdaSpeed Factory Turbo
The links in my original post #661 work, http://thefactoryfiveforum.com/showt...attle-WA/page3
Tony Nadalin
2018 SOVREN Big Bore Champion
2015 SCCA Oregon Region VP3 Champion
2012 ICSCC ITE Class Champion
FFR MkII Challenge Car, Spec Racer, Street Legal, SCCA, ICSCC and NASA Racing
818R Build in progress
I've been following this thread with interest. I am curious as it seems that the Whiteline kit noted by Junty from New Zealand has not received much support. I see the Baer system discussed as well as the DIY system which both require some modification. Am I missing something? Seems the Whiteline is a bolt on made for Subaru front end. I'm at go cart stage with my street only 818S, is it more an issue with 818R that need more adjustment than the Whiteline kit allows?
You should look at the Longacre refurbished list as all the stuff on this list has just been used at shows, and it can save you lots on $$$$. I live somewhat close to Longacre as they do most of their testing at the Monroe circle track about a mile away from them so they have some great products that actually work.
Tony Nadalin
2018 SOVREN Big Bore Champion
2015 SCCA Oregon Region VP3 Champion
2012 ICSCC ITE Class Champion
FFR MkII Challenge Car, Spec Racer, Street Legal, SCCA, ICSCC and NASA Racing
818R Build in progress
The whiteline does not solve the bump steer issue on the 818 which is different geometry than the WRX. You can use the DIY system w/o modification, as for racing I wanted to make sure I had matched the taper 100%. The good thing about the DIY is that no stock part is modified so if you break something at the track I don't have to then find someone to bore the spindle out for the strut.
Tony Nadalin
2018 SOVREN Big Bore Champion
2015 SCCA Oregon Region VP3 Champion
2012 ICSCC ITE Class Champion
FFR MkII Challenge Car, Spec Racer, Street Legal, SCCA, ICSCC and NASA Racing
818R Build in progress
Remember ride height and control arm location also come into play and what you find on an S will differ from what we/I have found on the R. Personally I have not worked on or checked the bump steer on an S. I enjoy playing with this kind of stuff and more than willing to work with 818 owners that are close to Bowling Green KY.
So finished up the bump steer this weekend, I was able to get .
Driver side .0020 on compression
Driver side .0040 on droop
Passenger side .0010 on compression
Passenger side .0030 on Droop
Alignment was -3 camber, +6 caster and 1/8 toe out (1/16 each side)
The passenger side did not need as tall of a spacer as the drivers side did
Last edited by FFRSpec72; 01-22-2017 at 09:42 PM.
Tony Nadalin
2018 SOVREN Big Bore Champion
2015 SCCA Oregon Region VP3 Champion
2012 ICSCC ITE Class Champion
FFR MkII Challenge Car, Spec Racer, Street Legal, SCCA, ICSCC and NASA Racing
818R Build in progress
Alignment was -3 camber, +6 caster and 1/8 toe out (1/16 each side)
Tony, I am curios on the toe out spec,the manual specs toe in 1/16" front wheels. Not toe out??
Your numbers look great Tony! Best I could do was .03 compression and .05 droop. According to Jim, this is because the frame and steering rack were designed around running at the R suspension mounting locations, so it's easier to get less bump steer that way. The only way to get less than I ended up with on the S is to add steering rack spacers.
Tony Nadalin
2018 SOVREN Big Bore Champion
2015 SCCA Oregon Region VP3 Champion
2012 ICSCC ITE Class Champion
FFR MkII Challenge Car, Spec Racer, Street Legal, SCCA, ICSCC and NASA Racing
818R Build in progress
Tony Nadalin
2018 SOVREN Big Bore Champion
2015 SCCA Oregon Region VP3 Champion
2012 ICSCC ITE Class Champion
FFR MkII Challenge Car, Spec Racer, Street Legal, SCCA, ICSCC and NASA Racing
818R Build in progress
I have 46mm on one side and 47mm on the other. Adding or subtracting spacers wont help me on the S at this point - all I can do is add steering rack extenders. The R requires more spacers because of the difference in suspension holes vs steering rack location. I may add the steering rack extenders at some point but it's lower on my priority list.
How did your rear come in Tony?
Rs need more spacers than Ss. Ok, Rs are 1" lower on the suspension mounts points. Is it fair to say, on the same car, if you mount the susp at the higher holes you will need exactly 1" less spacers on the bump steer than if you mount at the lower holes (same car, remember)?
Frank
818 chassis #181 powered by a '93 VW VR6 Turbo GT3582R
Go-karted Aug 5, 2016 - Then May 19+21, 2017
Tracked May 27/July 26, 2017
Build time before being driveable on Sep 27, 2019: over 6000h
Build Completed Winter 2021
Tony Nadalin
2018 SOVREN Big Bore Champion
2015 SCCA Oregon Region VP3 Champion
2012 ICSCC ITE Class Champion
FFR MkII Challenge Car, Spec Racer, Street Legal, SCCA, ICSCC and NASA Racing
818R Build in progress
Tony, why does high caster help with the turn-in?
Tony Nadalin
2018 SOVREN Big Bore Champion
2015 SCCA Oregon Region VP3 Champion
2012 ICSCC ITE Class Champion
FFR MkII Challenge Car, Spec Racer, Street Legal, SCCA, ICSCC and NASA Racing
818R Build in progress
Ah yeah gotcha. I spin out and went off the track at my last track day because I didn't have ANY feedback or self-centering due to lack of caster. Once the car got sideways, I countersteered, but it was too difficult to tell how much I need to countersteer and how quickly to take it back once the car started to correct. I have about 5.7 degrees now and could dial in a little more if I wanted to but I'm going to see how it feels on the track like this. Feels good on the street.
Sweet baby jesús I hope someone with your experiences knows there's a whole lot more going on then "feed-back."
The better feel is just an added bonus of your changing scrub, camber gain, weight jacking and a few other weird things. Those are what give you better ultimate grip. The steering is harder because you're actually lifting the car by rolling the tire backwards and underneath it (you can visibly see this on most modern cars if you have someone turn the wheel back and forth while you watch from the outside.)
I've known a few high-end race cars with power steering that run caster angles well into the double digits.
Your front should be toe'd out a small amount, the rear toe'd in an even smaller amount.
Tony Nadalin
2018 SOVREN Big Bore Champion
2015 SCCA Oregon Region VP3 Champion
2012 ICSCC ITE Class Champion
FFR MkII Challenge Car, Spec Racer, Street Legal, SCCA, ICSCC and NASA Racing
818R Build in progress
I'm still prepping donor parts and building my bump steer kit. I recently bought the Speedway Adjustable Tie-Rod Adapter and the tapered end doesn't go all the way through the knuckle. Am I missing something?
The taper on the speedway part doesn't match the taper of the Subaru spindles. Tony turned his down on a lathe for an exact fit. Most people won't have that option so that is why many of us just use the 5/8" bolts by drilling out the spindle instead of using a tapered bolt. That is what I did. There is a writeup here from Chad Plavan as well.
The tapered end on the Speedway part is close to the correct taper, but the diameter is larger than the OEM part so it doesn't insert all the way into the steering arm. The Baer bump steer kit has the correct taper and diameter but in my case was not quite long enough to get enough spacers on the driver's side. Some have felt comfortable with the Speedway piece inserted partway into to steering arm but this didn't seem a good solution to me. I ended up using the Baer on the passenger side and having the Speedway piece turned down to fit the steering arm properly for the other side.
Agree with Hindsight that drilling the spindle to 5/8ths is the easiest and cleanest approach. I would have gone this route as well if I was not doing it on an already assembled car.