Upper A arm mount relocation

cadreamn67

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Back in 1976, STOA published a Tech Tip on how to relocate (lower) the upper A Arm to spring tower mount position to improve a Tigers cornering ability. 66TigerMK1A very helpfully put it in in his albums back in a July, 2009 post. The post topic is Front End Mods and a link to his albums and the tip can be found there, for reference. He cautions that the STOA mods receive mixed reviews today but is said to help "some"...

I am seriously considering making such a mod to help in my autocrossing next season. I would greatly appreciate seeing responses from people that have made this mod and their opinion on how much it actually helps. Also, are there any variations on the theme (such as different relocation point distances) that others have found make for even better mod results?

Cheers, Gene
 

66TigerMK1A

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Hi Gene

As far as feedback, I remember at the last TU someone mentioned the mod and I thought I heard Doug Jennings say that 'it tears up the A-arms' . I didn't get to discuss it with him but he's one of the most knowledgeable 'Tiger guys' I've ever met so would be good to talk to about any mods as I'm sure he's seen it all.
I haven't noticed anything strange with mine but have not autocrossed it that much and have had the mod for at least the last 4k miles and I know that it was set up like that for many years in the 80's ( and autocrossed ) before the PO put it back to stock location.
You'll notice in the tech tip that they recommend milling one side of the fulcrum pin . You will need to do this otherwise you'll probably have too much negative camber for 'the street' and won't be able to adjust it out. What will make it worse is if you lower your car at the same time which will also give you more negative camber. A much better option is to use the 'Minx' spindles for lowering . I have them on my car and have spent a fair bit of time scouring the world to supply others... I think about 10 sets have passed through my shop in the last couple years

Jim
B382000446
 

Brianelec

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Upper A Arm relocation

I did this around 1972 with a MK II I had at the time. (Now all the MK II owners that can trace their car back to Southern California will be looking at the front suspension) If you are going to Autocross the Tiger only, it is a good change. If you are going to use the Tiger on the street and also autocross it, it is a bad move. I moved the upper A arms down 1". I don't remember machining the fulcrom pin. It makes a lot of camber, really too much for driving on the street as a daily driver. Maybe the 1" was too much to move the a arms. It seems to me that if you moved the A arms less than 1" the holes may be too close together not leaving the enough metal to structually support the front end under the loads placed on it in an autocross. Anyway after doing this change then visiting some front end shops regarding the move I moved the a arms back into the original locations as I drove this car on the street as a daily driver. One of the front end shops suggested heating up and bending the front suspension to get the desired results. I left that idea with them and ran out of there.
 

cadreamn67

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608
Thanks guys. Just what I was hoping for. Since these types of mods affect what class I run in, I wanted to get a current day understanding of the benefit/pain tradeoff involved. I think I will pass on this one since my car is very much a dual purpose, daily driver car.

I try to research things on my own as much as possible before bothering anyone. The tigersunited.com site has a wealth of information in its e-mail archives. Back in 9/99 Jim Leach in Seattle commented that in the vintage racing he was running at the time, he had a lot of negative camber dialed in for cornering help. Unfortunately, he was also having to brake earlier than the competition going into corners because it turned out he was braking on about half the full potential contact patch of the front wheels. The theory behind this relocation mod seems to be sound, giving you the best of both worlds: less camber in straight ahead is possible with negative camber gain in cornering which is when it is really needed. Probably at autocross speeds, the negative impact of significant negative camber on braking is not that big an issue. For now, I will be taking a pass on this mod.

Still, I do know Doug and will be talking to him. He is definitely one of the most knowledgable people I have met. We spent some quality time together last Spring when I took my A-arms to him to get my new ureathane bushings and ball joints installed. I now recall him dismissing this mod without much discussion but I was not really sure what he was talking about at the time. It would be good to know the details.

As I look at the geometry in the Tech Tip, it occurs to me that what may be "tearing up the A-Arms" is the new angle of the upper ball joint shaft. Rather than being centered in its range of motion it is now cocked to one side in the at-rest position. It may well be that it reaches it limit of motion as the A-Arm moves up, before the arm reaches its limit of motion as set by the snubbers. If that happened, I could see some real stresses being generated on the ball joint and passed on to the A-arm. Maybe this is part of the reason the tech tip says to bolt it all up without the spring in place and check for binding over the full range of motion. Maybe the total solution is to alter the A-Arm (cut/ reweld, gusset plates, etc.) so that the ball joint mounting part is properly oriented in the at-rest position. But I am not ready to experiment with that just yet!

So for now, I will not be drilling any holes. Just dial in about 2.5 degrees of negative camber. Maybe I can get skilled at removing a full shim or two after the event and then putting it back before the next event. This past season, I saw some of the guys with adjustable camber plates on their newer cars flailing away making adjustments before their drive home... Just need to learn how much difference a full shim makes...

Thanks again guys, and I promise to post anything I learn from Doug.

Gene
 
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michael-king

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Gene,

2.5 deg negative camber is huge.. to be honest anything more that 1 to 1.5 on a sunbeam that is not a track only car is going to make road driving a lot harder and im not sure you are going to be getting much gain.

I'm not sure how much neg you can get using the normal shims but i wouldnt be aiming for so much persinally. I have .75 on my alpine and tiger, it was enough to help in the turns yet not become difficult when parking driving normaly.
 

cadreamn67

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608
Michael, thanks very much for sharing your experience. We are very much on the same page.

I meant to say that the negative 2.5 degrees setting was something I was going to try for track purposes and then dial it back for more normal driving. I cannot remember what I had it set at this year back in the spring. I seem to remember asking for a negative 1.5, but got less than that. I cannot find the alignment sheet readout at the moment. I also had asked for 0.125 inches of toe-out. I understand a little toe out in the straight ahead position helps a little to offset the Ackerman angle toe-in problem as the car turns. I did not mess with any of the settings during the year.

The car as currently setup is admittedly just a little twitchy on the public roads at speed and has a tendency to follow groves in the pavement. I was thinking of maybe going back to a little positive toe-in before making any camber changes just to see how much stability that adds.

I well may end up using your setting and just leave it at that. Always extremely helpful to know what others have found works well for them. Thanks again!

Cheers, Gene
 

JimsCat

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I did this mod back in the late '60s or early '70s when I was autocrossing the Tiger. There were some clearance issues between the upper A-arm and its mounting bracket for which I ground clearance, being careful not to leave any stress risers. The car was also lowered on CAT springs. I wound up with an instant 2.5 degrees negative camber. I soon decided that was too much negative for street driving and took the car to the best alignment shop in town. The owner (now deceased) bent the spindles (cold) back into static alignment spec, so I had street static alignment with the more rapid change to negative camber in cornering. I drove it that way for many years after retiring the car from autocrossing.

A couple of years ago, I completely rebuilt the front suspension. when I reassembled it with the upper A-arms in the tilted (antidive) position, I found that the new upper balljoints would bind when turned, so I redrilled the mount to retain the lowered upper pivot but without the antidive angle. That eliminated the bind and retained the camber change rate. I also replaced the bent suspension uprights with a pair of the sedan spindles from Australia.

Changing the camber shims at the track seems like a PITA; but going to negative camber also increases toe-out, so maybe there's a side benefit there. Since toe is difficult to set on Tigers, I would choose a "street" toe setting with the "street" camber setting and let the toe fall where it may when adding shims for negative camber at the track. I don't like toe-out on the street; I'm currently running zero toe which works fine.
 
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cadreamn67

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608
Jim, some great insights and experience you have just shared.

It would appear that you were relatively happy with the mod once you got the "ripple effect" issues sorted out. Care to venture an opinion on how meaningful a difference it made to the car's cornering ability?

If I do attempt this mod, like you eventually decided, I would forego the castor enhancement part. I remember Doug Jennings telling me back in the Spring that basically Tigers just do not like to turn. Not a good trait for autocrossing. Castor being one of the things that keeps a car wanting to go straight, he recommended I keep it to a minimum.

As has been often said, understanding the problem is half the solution. There is a strong temptation now to give it a try if I can get comfortable with how to eliminate any binding issues. Could you share any more details on exactly where and how much clearancing you did? I take it that without the camber enhancement part of the mod, and unmodified spindles, you in fact did not have binding issues. I find that encouraging. What were those Australian sedan spindles you used in the rebuild?

Given your successful experience, maybe I should reconsider passing on this mod. Just drill the two holes and see for myself. If without the spring I find I have no binding issues in the full range of motion up and down and in turning, I should be okay. It would be relatively easy to put things back the way they were if I did not like what I am seeing.

BTW, I have had the cross member and A-Arm welding reinforcements done and am running Dales 425 #/in. coils in the front and a 7/8 inch anti-sway bar. I shaved the coil insulator donuts down to about 1/8 inch thickness, which lowered the front end about 3/4 inch or so. (Could not bring myself to completely eliminate them.) I have 1 inch lowering blocks in the back to help even thing out. (Still looks a little like it is running down hill, but that should make it faster, right?!) Right now I am running Dales MG Midget rack and pinion adapter and MGB steering arm setup but am seriously thinking about going back to the stock unit. The faster steering is a definite plus, but the turning circle is terrible. I blew my entry into a really tight hair pin at an autocross this summer and had to stop and back up to get around! Plus, based on an earlier posting on this forum it seems to give about the same Ackerman Angle results as the stock unit. I am upgrading from a tired 260 to a freshly rebuilt 289 and wide ratio trans over the winter, so while I have the cross member off, I am looking into other things to be doing... (Buck Trippel's 1 inch anti-sway bar and a Dan Walters torque arm are firmly on the to-do list.)

Anyway, thanks again for the great insights, and any additional details per the above you can share would be greatly appreciated.

Cheers, Gene
 

michael-king

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Right now I am running Dales MG Midget rack and pinion adapter and MGB steering arm setup but am seriously thinking about going back to the stock unit. The faster steering is a definite plus, but the turning circle is terrible.
Cheers, Gene


Gene,

Are you saying the turning circle is larger with the midget rack? I htought the midget rack did 3 things:

1. Quicker ratio
2. Corrected "some" of the ackerman issues
3. Provided a slightly smaller turnign circle and got rid of the scrub on lock issue.
 

cadreamn67

Platinum Forum Member
Messages
608
Michael, no question about the quicker ratio.

As for the Ackerman Angle observation I totally am relying on data in an earlier Forum post, as I mentioned. Have a look at Table 1 in response #3 by 66TigerMK1A on Front End Mods. As I read it, Column 1 indicates degree of turn for the inside wheel. Column 2 indicates what the corresponding outside wheel turn degrees should be. Column 3 gives the outside wheel actual degrees with the stock rack. Column 4 gives the outside wheel actual for the MG Midget rack and MGB steering arms setup. As you can see, toe-in occurs and increases as turn degrees increase, when you should be getting increasing toe-out. (The outside wheel should be turned less degrees than the inside wheel, as I am sure everyone already knows.) The actual results columns are very close for both racks. I have not put my car on an alignment machine to independently verify the results shown in Column 4. So for the moment at least I take the data as correct until proven otherwise. FWIW, I do note that data for 5, 10, 15, 20, 25, and 30 degrees in columns 1 and 2 match a post of what should be on the old tigersunited.com website by a Dr. Larry Mayfield on June 29, 1998.

As for eliminating wheel scrub at lock, it would seem that if the degrees of wheel turn are about the same, the scrub issue would be about the same, but perhaps there is some other factor at play I am not taking into consideration.

While the MG rack does go from lock to lock in fewer turns, subjectively it seems that the actual distance it moves lock to lock is rather short. It is almost like it has fewer teeth from left to right. Even if it did move the same distance left to right as the stock rack, it would produce a wider turning circle than the stock rack because the MGB steerings are longer than the stock arms. I see from my manual that the stock turning circle is supposed to be 37.5 feet. Certainly not all that tight. I would offer to try and measure mine now but it is 43 degrees (F), windy and raining (and dark). If I get a chance later in the week, I will try and get a measurement. In the interim, maybe another forum member already has a number and could share it.

At the moment that is everything I know.

Cheers, Gene
 
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JimsCat

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Gene, I may be embarrassed by a fuzzy memory of exactly what I did about 40 years ago. But looking at some pictures taken during my more recent rebuild helps a bit.

Because the antidive mod involved tilting the upper A-arm lower on its rear-facing side, the lip on the inside -- that open area that straddles the vertical U-section that mounts the pivot rod (if that makes sense) -- would contact that vertical support when the suspension went into droop. You'll recall that the side of the vertical "U" becomes wider toward its base. I ground away some, but nowhere near all, of that reinforcing inside lip of the A-arm to gain the clearance I needed. To the best of my memory, the interference occurred only on the rear inside opening since its lower mounting placed it nearer a wider portion of the "U." I believe that if you do not tilt the upper A-arm toward the rear, you will not encounter interference. And, as you point out, you can always return to the original configuration (if you don't mind painstaking realignments).

As for the binding, there was none with the original upper balljoints. But hand-turning the spindles revealed binding with the new balljoints, and they were oriented correctly in the A-arms. So I eliminated the A-arm tilt while in the process of reassembly.

Be aware that lowering the upper A-arm pivot results in (more) negative camber, all else being equal. Since you remove shims to adjust toward positive camber, you may not be able to get back to where you were. Each car is a little different. In my experience, however, 1 to 1.5 degrees negative does not wear the front tires unevenly, given somewhat aggressive driving.

I was happy with the mod and felt that it increased front bite, which -- as you know -- the car needed. I was running widened steel wheels (very few aftermarket wheels available for the Tiger's bolt pattern in those days, and none with acceptable offset), fat street tires, cut-down CAT springs, 7/8" front bar, 5/8" Addco rear bar, 1" rear lowering blocks, "heavy duty" Monroe shocks (still can't afford Konis), welded-on traction bars, and a single spring clamp near the front of the right rear spring that eliminated axle tramp.

Today I'm amazed at how much punishment the front suspension took. I broke an upper front shock mount once, but nothing else failed. When I rebuilt the front suspension a couple of years ago, magnaflux revealed a crack in one of the lower pivot pins. I replaced them both.

I don't know which Rootes sedan the spindles came from. My son also owns a Tiger, and a friend of his who is restoring an Alpine came up with three sets.

Your Tiger is much more modified than mine ever was. I am surprised that the Midget rack and MGB steering arms have not produced the advertised benefits.

It's probably not possible to compare my experience with anyone's these days. So much more is available for Tigers, and today's DOT "race" tires are phenomenal.

Now that I've gotten old and my Tiger is driven much more gently, none of my mods are even remotely needed. But it was fun at the time.
 

66TigerMK1A

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I just happen to have spares of all the parts so I went out to the shop to do some measuring ... it's 34° out there... lol
The midget rack travels 5 1/2" lock to lock... the Tiger rack travels 5 3/8"...
The inner tie rod ball joints are 26 1/2" apart on the Midget and 25 1/2" apart on the Tiger rack.
The MGB arms are 5/8" longer than the Tiger arms... this would lead me to believe that the tie rods are at a similar angle in both setups as what the longer arms gain, the rack takes away as far as lining up better with the front location of the rack.
The longer the arms, the less the wheels will turn... ( in theory ) but because of the different centres of the inner joints, it's hard to say what happens on the car...
According to Larry's TU article it does bring back the ackerman a bit... BTW that chart I posted was created by Dr. Mayf and I think all the measurements were ( as far as I can figure ) taken using the same ( Tiger ) rack dimension. The formatting came out screwy but I see you've figured it out...

I don't have any issues with the top ball joint as far as I can tell.

I think lowering the car by spring/insulator method will make the (negative) camber a bigger problem...( too much negative ) better to use the Minx spindles. The problem is multi-fold... You now have less travel before the suspension bottoms out and with both a-arms 'up', there will be more negative camber.
I have the upper fulcrum pins ground and the Minx spindles and I can get about 1/2° negative camber with no shims and the car sits low but the lower a-arm is still level.

One other thing with the lower a-arms to do with castor... the fulcrum pins are offset a bit in the way they mount... the notches for the mounting bolts are offset one way...If you flip them around when rebuilding the arms it will move the lower a-arm forward ( mine were like that ) and give you more castor... not necessarily what you want...

I have variable length tie rods via my ackerman correction setup and they get about 1/2" longer at full lock so the car turns in great! So much so that I had been playing around with smaller fron bars but the back end would come around very easily... I now have the 1 1/8" bar back on and am back to slight understeer. Buck has a 1" bar for me but I'm in the process of installing a 5/8" rear bar so that might work out with the front bar that I have...

BTW, the sedan spindles from Australia you mentioned are Sunbeam Minx or Rapier from later series cars sold in U.K., AU. NZ and Canada... I'm always searching for them and regularly sell them to Alpine/Tiger guys...

Jim
 

cadreamn67

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608
Thanks again for the helping hand all of you guys have given me. Fabulous wealth of information being shared. Anything that contributes to helping the Tiger be all it can be, regardless of the context, to me is great. Hopefully others are benefiting from it as well.

I do think I may have only partially read Dr. Mayfs. chart correctly. There are actually five columns of data. I was typing from memory, thinking there are only four. Least anyone be mislead by a mistake I may have made, would you confirm what the headings are for the last three columns?

Thanks, Gene
 

66TigerMK1A

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Here's a link to Mayf's entire article on the subject...

http://www.mayfco.com/steering.htm

First column... Inside wheel input
Second column... perfect ( outside wheel output )
third column... Tiger arms
fourth column... MGB arms
Fifth column... Special ( Mayf made his own trial set )
 

0neoffive

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them thar wish bones, etc.

Well, coming up on 4-1/2 decades of playing with these wee Tigger critters, I can say that we've tried about all of it. Dropping the upper A-arm holes gave us something new to try but didn't achieve much, really. Probably the best handling I ever got (on the track that is) was when one of my circle track buddies welded up some square tubing into front & rear sets of adjustable sway bars from hell. Kinda ugly, very rugged, and absolutely no give to them whatsoever. If one corner of the beast tried to dip, it had to take the other corners down with it. His cute secret was where the adjustment was; on the frame mount and not the axle or wish bone. He would watch the car as I immitated a real driver through the turns and then pre-position the stress for the optimum turns & my bad habits. Although hell on tyres, the little critter stayed completely flat and drifted neutrally. Just another 2 cents to kick around. randy
 

cadreamn67

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Randy, I must say that is a very vivid word picture of you on the track that you painted! Seriously though, your characterization of the mount relocation was a very important addition to the experience opinions I have been seeking. Thanks for that as well as the big smile from your personal experiences back when.

It is looking more and more like Bob Bohrer's advice in the Shop Notes on autocrossing a Tiger still is some of the best advice around. For the car I think I will just focus on locked in negative camber, adding Buck's one inch sway bar, Dan's torque arm and getting as much sticky rubber on the track as possible. My son is pushing for 13 inch wheels (3.5 inch back space front, 4 inches back), with 8 or 10 inch rims, and Kuhmo, Hoosier, or Hanhook autocross tires. So what if it looks strange? If it works, no one is going to be laughing. Plus, he is about 7 seconds faster than me at any given event(but usually has more DNF's too!) So I know there is more improvement in the driver's seat area for me.

Supposed to get snow this weekend. If it is not too much, maybe that will give good conditions in our cul de sac for measuring the turning circle I have with the MG Midget rack adapter kit!

Cheers all, Gene
 
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