Bump steer

[Hindsight]

A few questions about bump steer.

At S ride height, can I use the tapered bolt that comes with the Baer kit or will it be too short?

I watched a video demoing the Longacre bump steer gauge and one thing I don't understand is how the gauge reading is not impacted by camber change induced by suspension travel. As the suspension compresses, doesn't negative camber increase and wouldn't this impact the reading?

Thanks.

[NAZ]

If you have the single dial indicator there is a wheel on the other side that rides on the plate as the suspension travels up and down. The effect of camber gain is the same on the idler roller and the dial indicator so camber will not show up as bump steer, only toe in or out will be indicated. The change in toe is what creates bump steer.

[Canadian818]

Is bump steer an issue at S ride height?

[Hindsight]

Thx Naz.

Adam, I believe it is. My alignment is good but when hitting bumps in the road it is quite darty. I am sure it would be worse at R height but I plan to buy the longacre gauge and test it on my S at S height to see. I would bet there is more than an ideal amount but we shall see. I don't think anyone has tested a stock suspension S setup yet.

[UnhipPopano]

Hindsight, There was a post on this site somewhere that made the point that the hinge between the inner and outer steering rods needed to be in the plane created by the upper and lower control arm hinges. To me this sounded easier said than done, as adjusting the caster would move the plane. Did you verify that this hinge is along this plane after setting the caster?

[Hindsight]

Hmmm, I am not sure I follow. My understanding is that if you traced a line that followed the angle of the upper control arm, the lower control arm, and the tie rod, that they should all intersect at a point. Like this diagram:
https://goo.gl/images/F0nlP5

Is this the same as you are saying?

[Bob_n_Cincy]

To test my bump steer.
I blocked the front car at 1" higher than ride height.
I removed the front coil overs.
I tie wrap a laser level to my front wheels spokes.
then raised my front wheel to measure the horizontal movement of the dot on my garage door.
Bob

[Bob Cowan]

That won't work. As said above, as the wheel moves through it's arc, camber changes. You need to measure the distance that the front of the tire moves and the distance the rear of the tire moves. The difference between the two measurements is bump steer.

I made a simple adaptor to measure it. It was almost free, since I used stuff left over from other projects.

http://i13.photobucket.com/albums/a256/bobcowan/BumpSteer3.jpg (http://s13.photobucket.com/user/bobcowan/media/BumpSteer3.jpg.html)

Move the hub through it's arc up and down, and measure the distance it moves. Then flip it around and do the rear. Subtract one from the other, and there you are.

[Hindsight]

Thanks for the replies. Seems like no one with a stock suspension S has mearured bump steer yet. I will do it and report back results in a couple weeks.

[Canadian818]

Thanks for the replies. Seems like no one with a stock suspension S has mearured bump steer yet. I will do it and report back results in a couple weeks.

You're contributions are appreciated. Looking forward to seeing the results.

[Junty]

Hey crew, my 818s (although RHD) absolutely suffered bump-steer. I have standard S shocks, and initial setup was following precisely FFR specifications for ride height. I purchased the WhiteLine bump steer correction kit KCA313 http://www.whiteline.com.au/product_detail4.php?part_number=KCA313 - these are available from eBay. Due to the changes FFR have made between the coli over WRX setup - I didn't use the lower arm modified joints - I just used the WhiteLine tie rod ends, these lower the rack end pivot to the front hubs, improving the geometry as suspension raises and lowers. Easy fix...

[Hindsight]

Thanks Junty. Did you happen to measure the bump steer before and after to see how bad it was and how close to 0 the whiteline tie rod ends brought you to?

[FFRSpec72]

Thanks Junty. Did you happen to measure the bump steer before and after to see how bad it was and how close to 0 the whiteline tie rod ends brought you to?

That kit looks odd as it seems a fixed height and something you can't adjust. I would also like to see before/after

[RetroRacing]

We measured toe at height, then dropped the ride height by 1.5" (to mirror compression) and measured toe again. What's wrong with my theory? (we ended up with 1/8" different, 1/8th toe in to 0)

[FFRSpec72]

We measured toe at height, then dropped the ride height by 1.5" (to mirror compression) and measured toe again. What's wrong with my theory? (we ended up with 1/8" different, 1/8th toe in to 0)

Nothing, that is basically what the Longacre gauge does http://www.longacreracing.com/instructions.aspx?item=8027&article=Bump%20Steer%20Gauge%20-%2079000

[Mitch Wright]

And it works great, this is the gauge that I have been using for years http://www.longacreracing.com/products.aspx?itemid=1710&prodid=12630&pagetitle=Precision+Bump+Steer+Gauge+with+Billet+P late+-+4+%26+5+Bolt+Sport%2fCompact

[Hindsight]

I'll be buying the Longacre gauge as well. They have a new one with billet plate and digital gauge. All this "race stuff" though.... for my "street car". Kind of afraid my next move is going to be selling my daily driver and replacing it with a tow vehicle then buying a trailer and, and, and....

[FFRSpec72]

I'll be buying the Longacre gauge as well. They have a new one with billet plate and digital gauge. All this "race stuff" though.... for my "street car". Kind of afraid my next move is going to be selling my daily driver and replacing it with a tow vehicle then buying a trailer and, and, and....

See if they have one in their "refurbished" catalog" as they usually do. they are just up the road from me, they basically grew business from the local circle track here

[NAZ]

Hindsight, you will be glad you purchased a bump steer gauge as it makes checking the bump steer much easier than some of the home made tools I've seen in use (including my own cobbled together ones). Most of the ones I've seen will do the job but are a bit cumbersome to use. Keep in mind that when you start adjusting out of the condition that caused bump steer you will be checking each side numerous times as the adjustment process is iterative. And because the steering system is a "system" every time you make and adjustment to caster, camber, ride hight, etc you may be affecting bump steer. Also, don't just check bump steer with the wheels straight ahead. Even if you achieved zero bump steer with the wheels straight you may find that toe changes at a different rate when the wheels are turned as when cornering. I use a Longacre single dial bump steer gauge and find it works reasonably well but I modified mine to stiffen the tubular frame for improved repeatability. I don't trust a reading if the indicator doesn't zero when returned to the starting position. Good luck and have fun.

[Hindsight]

Thanks Naz and Tony.... very helpful!

[Junty]

All my alignment, ride height, camber caster etc including bump steer was measured on a machine. I have computer sheets - somewhere? My car has now completed 8000+km and the bump-steer was corrected more than a year back... I'll endeavour to locate the printouts...

[Junty]

That kit looks odd as it seems a fixed height and something you can't adjust. I would also like to see before/after

Hey Tony, I'll endeavour to locate the alignment printouts with bump-steer. You are correct these are fixed height. The kit was specifically designed to correct the imminent bump-steer so common in WRX Subaru's that have been lowered. In NZ we have very strict compliance for custom, modified or built cars, the baer style kit does not comply.

[Junty]

Hey all, sorry for the delay but I've finally located all my alignment printouts...
This was all completed more than 12 months ago, the 818s is driven most days, and has now done more than 5500miles. The first image is the full wheel alignment, then next is the 'Bump Steer' test with the standard FFR specification for the build. The final image is the same 'Bump Steer' test with the only change being the swapping of the standard Subaru 'Tie Rod' ends to the new 'Whittline' Subaru bump steer correction ones.
I trust that this helps others correct bump steer...
Note the 818 is setup to exactly what FFR recommends, the car has 818s shocks and springs and ride height is to FFR specification. Overall the car handles superbly well and appears to riding on tracks around corners at phenomenal speeds...577095771057711

[Hindsight]

Thanks for posting this junty. If I'm reading that right, it appears that the white line tie rod ends reduced the bump steer from an average of 10 degrees to an average of about 8.5 degrees?

Ideally, you want to shoot for 0 degrees total.

[Junty]

Hey there Hindsight. Its actually better than that. I'll get information tomorrow - but as I understand it we need less than 0.5. The number in the centre is what they are using to rate the Bump Steer. My final is 0.4.... I'll post more information tomorrow...

[Canadian818]

I was just checking out some DIY bump steer gauges and came across this guys idea. Similar to Bob's idea with the laser pointer, but it very clearly separates steering changes from camber.

http://www.pro-tourings10.com/index.php?topic=1110.0

[gpaterson]

My 818S had a major problem with bump steer and for New Zealand compliance we need to eliminate all bump steer. At the standard S ride height it was impossible (although I know Justien managed to achieve it) but I had use the R mounting with the top A arm on top of the mounting.

Some pics ...

5811158112

Probably the only major engineering issue with the kit - and the conversion to right-hand drive too.

[Hindsight]

Thanks for sharing gpatterson. That's very interesting about using the R mounting location for the upper control arm. I assume you did not use the R mounting location for the lower arm?

Now I am REALLY curious to measure my bumpsteer with the gauge I bought.

[Sgt.Gator]

I've used Smart Strings for years to do my setups. They are a little expensive but vs a couple of alignments at a shop they pay for themselves. And they are the only way to do it at the track.

However I've never considered using them to check bump steer. I think they would work fine in that application too but I'm no suspension guru.
As long as I already have them all setup for the usual 4 wheel toe and thrust check it seems like it would be easy to put a floor jack under each wheel one at a time and do a 4 wheel bump steer test.
Can anyone think why they wouldn't work for bumpsteer?

Here's the manual if you aren't familiar with how they work: http://www.smartracingproducts.com/smartstrings/smartstrings_manual_v1.pdf

[Hindsight]

I use a string alignment as well (though just via jack stands, fishing wire, and conduit pipe). How do you use it at the track though? You need a perfectly level surface for the car and that is hard to find at a track.

The issue with using strings to check bump is that you want the string on the center line of the rotor and as you raise or lower the suspension, the string will no longer be in the right spot. In addition, as you raise the suspension, the wheel/rotor camber will increase, and it will also move inward away from the string. You could account for this in your measurements by measuring from the front and from the rear and then doing the math but the height of the string is still going to be a problem. Bottom line - I'm sure it would work but it would be quite a pain. A nice Longacre bump steer gauge can be had for like $150.

[Sgt.Gator]

Ahh, good point about the center of the rotor/hub. I'll get the Longacre gauge.

Regarding at the track, for perfection I've seen guys using a roll on leveling tracks. However I'm not using it for finding the perfect alignment. I use it for "oh crap I just got smacked by a another car during qualifying" or I just smacked an immovable object in practice and I have to get things close enough to finish the race / weekend. For "good enough" you just need to find a relatively flat space.

[Hindsight]

Got it, that makes sense.

I've been planning out some "alignment leveling pads". I need them to do alignment in my own garage anyway because my cement garage floor is not level. Lots of high and low spots. You could take these to the track as well.

Basically like this but without the scales:
58116

Would be easy to weld up a lower-rent version of that using 2" steel tube, some steel plate, and some 1/2" diameter leveling feet from McMaster. I like that they are rectangular to give you enough space to roll the car back and forth a bit to un-jack the wheels after you make an adjustment. You would want these high enough that you could get under the car to adjust the suspension. This also means you'd have to jack the car up, place these under the tires, then lower the car down on them (one end at a time). No big deal.

[Canadian818]

Got it, that makes sense.

I've been planning out some "alignment leveling pads". I need them to do alignment in my own garage anyway because my cement garage floor is not level. Lots of high and low spots. You could take these to the track as well.

Basically like this but without the scales:
58116

Would be easy to weld up a lower-rent version of that using 2" steel tube, some steel plate, and some 1/2" diameter leveling feet from McMaster. I like that they are rectangular to give you enough space to roll the car back and forth a bit to un-jack the wheels after you make an adjustment. You would want these high enough that you could get under the car to adjust the suspension. This also means you'd have to jack the car up, place these under the tires, then lower the car down on them (one end at a time). No big deal.


I found some cement patio stones and a pack of door shims worked great for making a level surface in my garage. I'm going to try the laser pointer method to check mine. I don't have enough threads on my tie rod on the passenger side, right now I just split the difference and the wheel is way off center. If I need bump steer adjustment I'll just replace the outter section with a longer threaded collar and a hiem joint.

[FFRSpec72]

Has anyone measured the rear bump steer to see where that stands ?

[ben1272]

I assume FFR has the entire 818 digitized and modeled in Solidworks. If so, shouldnt they be able to obtain the expected bump steer effect by moving the suspension through its motion and measuring the effect on the suspension geometry? This would be nice to have to compare to measurements made on actual assemblies, which presumably FFR has also done. Any chance they would report the values that they see? Jesper, does FFR have these values and if so can they be published? I may not understand what is involved and if so please disregard.

-ben

[FFRSpec72]

I assume FFR has the entire 818 digitized and modeled in Solidworks. If so, shouldnt they be able to obtain the expected bump steer effect by moving the suspension through its motion and measuring the effect on the suspension geometry? This would be nice to have to compare to measurements made on actual assemblies, which presumably FFR has also done. Any chance they would report the values that they see? Jesper, does FFR have these values and if so can they be published? I may not understand what is involved and if so please disregard.

-ben

I don't know what the expected travel is for the suspension, I would hope it would not be more that 2" bump or droop as I would need that info to be able to measure what my actual assemble is now.

[Mitch Wright]

at R ride height 2" compression 1" of droop from static is what I believe is needed. Yes doing the rear is a must in my opinion.
http://thefactoryfiveforum.com/showthread.php?15436-My-818R-Project-has-arrived/page4 #150

[FFRSpec72]

at R ride height 2" compression 1" of droop from static what I believe is needed. Yes doing the rear is a must in my opinion.
http://thefactoryfiveforum.com/showthread.php?15436-My-818R-Project-has-arrived/page4 #150

Thanks, I forgot about that discussion

[Frank818]

Curious to see what parts you need to modify/install to correct rear bumpsteer?
I don't see the related pix on the link http://thefactoryfiveforum.com/showthread.php?15436-My-818R-Project-has-arrived/page4

[Hindsight]

No additional parts required to correct rear bump steer. You adjust it with the upper trailing arm link.... the zinc plated one that goes from the firewall to the top of the rear spindle.

And yes, front and rear, you measure 2" compression and 1" of droop.

I still need to check and adjust my rear.

[Frank818]

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.

[Hindsight]

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.

[lance corsi]

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.

[ben1272]

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!

[Mitch Wright]

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-1001-bump-steer-explained/
http://www.longacreracing.com/instructions.aspx?item=44524&article=Universal%20Bump%20Steer%20Gauge
http://www.irvansmith.com/scart/article_info.php?articles_id=11

[Hindsight]

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.

[fastzrex]

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!



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.

[FFRSpec72]

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!

Adjusting the steering arm, you will need to replace the rod ends, adjusters/sleeves and stud/shaft, I have documented the parts that I used in this tread.

[Hindsight]

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!

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.

[Mitch Wright]

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.

[fastzrex]

Thanks for the info! Are you referencing your build thread for the bump steer components?


Adjusting the steering arm, you will need to replace the rod ends, adjusters/sleeves and stud/shaft, I have documented the parts that I used in this tread.

[RetroRacing]

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.....

[fastzrex]

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?main_page=advanced_search_result&search_ in_description=0&keyword=RC21083&x=21&y=8
http://steinjager.com/shop/index.php...earch=J0041201


Adjusting the steering arm, you will need to replace the rod ends, adjusters/sleeves and stud/shaft, I have documented the parts that I used in this tread.

[frankc5r]

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?main_page=advanced_search_result&search_ in_description=0&keyword=RC21083&x=21&y=8
http://steinjager.com/shop/index.php...earch=J0041201

Could not get the links to work.

[FFRSpec72]

Could not get the links to work.

The links in my original post #661 work, http://thefactoryfiveforum.com/showthread.php?12205-FFRSpec72-818R-Build-Seattle-WA/page3

[tgf05354]

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?

[FFRSpec72]

I'll be buying the Longacre gauge as well. They have a new one with billet plate and digital gauge. All this "race stuff" though.... for my "street car". Kind of afraid my next move is going to be selling my daily driver and replacing it with a tow vehicle then buying a trailer and, and, and....

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.

[FFRSpec72]

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?

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.

[Mitch Wright]

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.

[fastzrex]

Yep, I screwed up, copied the text rather than the actual underlying link address; and then did not test. I will do better next time!


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?main_page=advanced_search_result&search_ in_description=0&keyword=RC21083&x=21&y=8
http://steinjager.com/shop/index.php...earch=J0041201

[FFRSpec72]

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

[DMC7492]

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??

[Hindsight]

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.

[FFRSpec72]

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??

I always race with a toe out or 1/16 to 1/8 total as I run a high caster.

[FFRSpec72]

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.

I am close to 3" of spacer on drivers side, and about 2.75 on passenger side

[Hindsight]

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.

[Mitch Wright]

How did your rear come in Tony?

[Hindsight]

I am curios on the toe out spec,the manual specs toe in 1/16" front wheels. Not toe out??

Most race cars run toe-out. Helps with turn-in.

[Frank818]

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)?

[FFRSpec72]

Most race cars run toe-out. Helps with turn-in.

High caster helps me turn in and toe out helps a little on the turn out

[Hindsight]

Tony, why does high caster help with the turn-in?

[FFRSpec72]

Tony, why does high caster help with the turn-in?

The more positive caster the more "feed-back" you will feel driving the car. So more positive caster the better" but makes steering harder as the steering force increases. I get good feed back on turn-ins

[Hindsight]

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.

[phil1734]

The more positive caster the more "feed-back" you will feel driving the car. So more positive caster the better" but makes steering harder as the steering force increases. I get good feed back on turn-ins

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.

[FFRSpec72]

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.

Yes I understand suspension very well, but that was not the question that was asked. To me the feed-back is important aspect of caster but there other aspects as you point out.

[wmaurojr]

I'm still prepping donor parts and building my bump steer kit. I recently bought the Speedway Adjustable Tie-Rod Adapter (http://www.speedwaymotors.com/Adjustable-Tie-Rod-Adapter-Stud-to-Heim,3333.html?OriginalQuery=91636055PINTO) and the tapered end doesn't go all the way through the knuckle. Am I missing something?

[Hindsight]

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.

[idf]

I'm still prepping donor parts and building my bump steer kit. I recently bought the Speedway Adjustable Tie-Rod Adapter (http://www.speedwaymotors.com/Adjustable-Tie-Rod-Adapter-Stud-to-Heim,3333.html?OriginalQuery=91636055PINTO) and the tapered end doesn't go all the way through the knuckle. Am I missing something?

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.

[idf]

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.

[wmaurojr]

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.

Thanks guys,

I'll go with the 5/8" bolt.