Bump steer after aw11 manual rack conversion

Nomnom83
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Bump steer after aw11 manual rack conversion

Postby Nomnom83 » Wed Jun 29, 2016 10:10 pm

Installed and centered aw11 manual in my ae86, now have bump steer when hitting bumps on the passenger wheel. Anyone else have this issue?

Found this
http://forums.club4ag.com/zerothread?id=89702&page=2

But no one else talks about this.

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davew7
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Re: Bump steer after aw11 manual rack conversion

Postby davew7 » Thu Jun 30, 2016 4:07 am

If you are "sure" that the inner tie rod pivots for LH/RH are equal distance, [not clamped in AW-11 factory location] then you will have to adjust the elevation at each pivot point to get ends of the tie rods traveling thru the same arc.
Get a suspension handling book that shows how to make a simple dump steering gauge, and plan on several hours making shims to get the minimum bump steer. You will find that an adjustment as small as .020" will change the steering. You can also adjust the fore/aft location of the rack, but that will also affect Ackermann. Dave W

Deuce Cam
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Re: Bump steer after aw11 manual rack conversion

Postby Deuce Cam » Thu Jun 30, 2016 2:02 pm

I haven't really noticed any bump steer on mine with an aw11 rack. Iirc there was a very slight difference in overall tie rod length on each side though. The rack is properly centered.

I remember the thread/pic you linked and it's the only place I've seen the comparison. I asked around a lot over the years and nobody seems to know for sure if they are different.

I noticed that my power passenger side bracket/t3 adapter bushing is right out at the edge of the aw11 rack housing. If the housing was any shorter I don't think it would fit.

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ToeKnee805
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Re: Bump steer after aw11 manual rack conversion

Postby ToeKnee805 » Thu Jul 07, 2016 12:53 am

track driving i felt like the ae86 rack was harder to turn than an aw11 rack, but as far as bump steer, do you have RCAs already? Maybe converting to manual just made the bumpsteer that was already there more noticeable?
1986 Corolla GT-S -- Unmolested -- Now Resto Project
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1982 Corolla 1.8 -- Sitting collecting dust

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Deuce Cam
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Re: Bump steer after aw11 manual rack conversion

Postby Deuce Cam » Tue Jul 12, 2016 11:47 am

I just came across this pic in badboy88000's build thread (ae86 top, aw11 bottom):

Image

The ae86 housing definitely is shorter. I wonder if the rack/gear is the same length since it's hard to tell in the pic.

Also, here's the pic from Grant's old build thread that the op linked (ae86 on top, aw11 bottom):

Image

assassin10000
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Re: Bump steer after aw11 manual rack conversion

Postby assassin10000 » Thu Aug 04, 2016 2:11 pm

Yeah, both housings are different lengths. Aw11 internal gear is about 1/8" longer than ae86.

Andrew

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Re: Bump steer after aw11 manual rack conversion

Postby Deuce Cam » Thu Aug 04, 2016 3:33 pm

Assuming the r&p are interchangeable... the quaife aw11 r&p (or stock aw11) in an ae86 housing might be ideal.

I wonder how the ae71 stuff compares.

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Re: Bump steer after aw11 manual rack conversion

Postby Deuce Cam » Sat Sep 16, 2017 2:37 pm

So an opportunity presented itself to measure an ae86 rack/housing and an aw11 rack/housing.

The housing AND rack are different lengths when comparing the ae86, and aw11 parts. I used a measuring tape with the racks both installed on different cars, so the measurements aren't exactly precise, but anyway here goes:

ae86
rack: 21-11/16"
housing: 15-3/4"

aw11
rack: 21-7/8"
housing: 16-3/8"

The aw11 housing is 5/8" longer than ae86. The distance between the middle of the driver side mounting point and the end of the driver side rack housing is the same on both. This means the extra 5/8" length on the aw11 housing all ends up on the passenger side when installed in an ae86. In other words, an aw11 rack housing is off center when installed in an ae86.

It's also interesting to note that the ae86 rack length (part that inner tie rods bolt to) is 3/16" shorter compared to the aw11 rack. The increased length equates to higher steering ratio AND steering angle/travel. Think of the added length like a rack spacer which also adds more angle/travel.

For reference I also found this old link: http://www.ae86drivingclub.com.au/forum ... -2778.html

The most important post from the linked thread above is quoted below for convenience:

2nd March 2009, 08:28 PM
Note: still looking for info if you have it, but below is what I think from limited info, but cafefull measuring and calculating of what I do have:


All manual racks (except aftermarket quick racks) use the same pinion (6 teeth) and gear ratio. (About 43.3mm rack movement per turn). All rack housings (at least the manuals) are of the same width, 400mm +-1mm.

AE86/AE85 with power steer
rack width: 530mm?
stroke: 130mm
turns: 3

AE86/AE85 with manual steer
rack width: 552mm
stroke: 152mm
turns: 3.5

AE86 GTV manual
rack width: 530mm
stroke: 130mm
turns: 3

The GTV has the same steering rack ratio, but the resulting steering is quicker only due to the shorter power steering knuckles. Due to the sharper angle the PS knuckles would give, the GTV rack stroke is limited. Both the regular manual cars and the GTV would have similar maximum steering angle.

KE70/AE71 some* manual
rack width: 545mm
stroke: 144mm
turns: 3.3

*The KE70 in Australia shares the same rack housing as the AE86 (400mm wide) and the same pinion and gear ratio, but the rack itself is not as long. Some KE70's in other countrys use the same rack as the AE86.

To achive the sharpest steering angle with the above parts, we use the longer 152mm steering rack (not the GTV one), combined with the PS/GTV knuckles. At this point, the tyre may start to rub on the inner body. To achive even greater steering angle (with either **longer rack, special rack ends, slip on spacers or screw on spacers) you also need longer lower control arms.

Tie-rod ends:
AE86 steering rod ends are about 190-195mm long, from ball joint centre to end. Due to a narrower rack, the GTV ones are about 208mm long. With longer lower control arms, use RA40/KE30 tie-rods.

Quick racks from TRD, Cusco/Chowini and Quaife are all based on the normal 152mm stroke manual rack. The Quaife one is still available, and has 2.5 turns.

**If you want a custom length rack, you can use a RA60 one and cut it down.
Kid Karola


The specs listed in the above quote for ae86 are in line with my measurement.

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Re: Bump steer after aw11 manual rack conversion

Postby Deuce Cam » Thu Sep 21, 2017 12:20 pm

Also reached out to quaife regarding their qsr kits for ae86 and aw11. Both kits use the same exact rack. Only the pinions differ. Both racks are 21.653" long, which is even shorter than an oem ae86 manual rack

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Re: Bump steer after aw11 manual rack conversion

Postby xslowpokex » Fri Sep 22, 2017 4:32 am

If your 86 is lowered more than 1.5inches from stock you will need front RCAs to alleviate the bump steer, if you have RCAs and your bump steer is still persistent then your car is too lowered. You have 3 option, go back to powered steering, raise your car up, or just live with it. I honestly think manual steering is more adequate in a track or weekend car its very inconvenient for daily driving especially in tight spaces, like parking lots, parallel parking, moving in slow traffic, its just a work out period lol and if not done right can actually make the steering feel crappy leaving you with too much steering slack to sort out. But deleting the power steering does make for more noticeably rev happy 4ag : )

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BattleGarage_RS
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Re: Bump steer after aw11 manual rack conversion

Postby BattleGarage_RS » Fri Sep 22, 2017 1:46 pm

I strongly urge people to find a true manual rack because of the bump steer we noticed with the AW11 racks when properly centering the rack.

Your choices with the AW11 rack seem to be 1. Have too much angle turning left 2. Having equal steering angle but worse bump steer on oneside than the other.

Also, hit up Ezekiel for a proper P/S rack de-power service. I have driven his car multiple times with his properly de-powered rack and it feels GOOD!

Grant
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AE86 parts 24/7 :arrow: http://shop.battlegarage-rs.com

Deuce Cam
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Re: Bump steer after aw11 manual rack conversion

Postby Deuce Cam » Fri Sep 22, 2017 3:29 pm

^exactly. Equal steering from center (lock-to-lock) when using an aw11 rack in an ae86 equates to different overall tie rod lengths (inner pivot to outer pivot) on each side, which causes the alignment/bump steer issues.

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