Bump Steer remediation

Chris Taunton

Daily Driver
Has anyone here tried to fix the bump steer on their 128? I am about to install the MWB coil-over struts in Gus and am having some drop spindles made to help the camber gain curve (made from X1/9 spindles - slightly lower steering arms). The stock geometry has a ton of bump steer. Relocating the steering rack seems like an impossibility. Has anyone modified their steering arms for bottom mount or heim jointed tie-rod ends? How much drop was necessary? X1/9 geometry is similar enough for a ball park idea of what is involved.



Thanks,

Chris
 

Dr.Jeff

True Classic
Chris, I'd like to see what you are making for drop spindles.

My old VW's get lowered significantly, throwing off the bump steer. They have a similar suspension and steering layout to the old Fiats. The easiest approach I've found is to "flip" the tie rods and mount the outer tie rod ends from below the steering knuckles instead from above. The ends have a tapered mounting bolt so when they are flipped the taper is in the wrong direction. The solution is to drill out the hole in the steering knuckle and install a tapered sleeve insert from the bottom. Then the stock tie rod end fits correctly. This is what the inserts look like:
Late_Trackrod_flip_kits-BB-051-3-400x400.jpg


They also offer heim joint tie rods for that vehicle. It wouldn't be too difficult to make some. You can get universal kits to help:

711nsBjRpnL._AC_SL1500_.jpg
download.jpg


The amount of tie rod drop needed depends on how far the car is lowered. But the rule of thumb that I've always heard is to make the tie rods parallel with the lower suspension arms.

For really low drops, they also add an extension to the lower ball joint to raise the strut relative to the suspension arms. That reduces the change in the geometry.
 

fiatfactory

Steve Cecchele
There are differences in hubs from early , thru mid and then later 128's. some differences relate to bearing retention method, and bearing size, but there are also differnces in the steering arm height.

to look at the earlier type hubs / spindles, you can vsually see the differnce to the later type, as the later style (from about 1975 here in australia with the 128 3p's) as the steering arm is much chunkier / thicker.

Now a very interesting fact... X19 series 2 (the type with the larger front bearing) and ritmo/strada and really late 128's are in fact the same hub / spindle, same fiat part number and everything.

Now I've never really looked... i.e had them side by side, but seeing as the 1975 128 3p and the 1975 x19 both used the same wheel bearig size... I've got a pretty good hunch that these are in fact the same.

You are 100% correct that a 128 has bucket loads of bump steer... WHEN ... it is set at the ridiculously tall stock ride heigth you have in the usa... you will find as you lower the car, the steering rack will come down closer to the ground and the bump steer curve will become a lot better... as you drop the car further, same thing happens, the curve gets screwed up again.

So the answer to your question will actually lie in the ride height you choose, as to how much you will need to raise/ lower the rack, which is actually quite simple to do... find a copy of PBS x19 race prep bok, there are drawings showing how to make the rack brackets.

SteveC
 

fiatfactory

Steve Cecchele
the other thing you'll find as you lower the car / dial in some negative camber, is that you'll run out of adjstment at the threads... simplest remedy is simply trim (nice and square so the locking nut still seats well) some off the inside length, there's usually enough internal thread to do the job... if you lower it futher then shorter outer TRE from other models of Fiat interchange...([pre 82 x19's a lot shorter, post 82 is a differnt thread) closet thing in the usa would be a pre 82 strada / ritmo or maybe a yugo is similar but shorter (probably like a 127 outer TRE) ... about 1982/83 fiat seemed to change the thread size on the inner tre's they used from TRW

Jeff and I replied at the same time... and the drill out the arms and reverse the outer TRE's taper also works, but it's a big change.

I don't think you can use a heim joint with a straight thru drilled hole in the steering arm for the road, as I'm quite sure it's a legal requirement for that part of the car to have a self locking taper to secure it.

SteveC
 
Last edited:

Dr.Jeff

True Classic
I've never heard of any legal requirements for the tapered mounting stud, but there may be. Might depend on where you live. However I agree that heim joints are not a great option for a street driven car. They are noisy and transmit a lot of vibration.

Steve's earlier description of the 128 having a really high ride height to begin with is something I hadn't considered. I'm more a X1/9 person, so I was assuming you were referring to lowering your car enough to create a bump steer condition. That's when the tie rods would need to be dropped. But with the 128 sitting really high, then yes that will also cause bump steer, and I guess raising the tie rod is required. So I suppose another method to eliminate the bump steer is to lower the car closer to the Euro spec, bringing the front ride height down and making the suspension arms more parallel. Then no change would be needed to the tie rods.
 

Chris Taunton

Daily Driver
Steve and Dr. Jeff,

Thank you! This is exactly the kind of help I am looking for.

I'm not sure the early US models had a different ride height compared to European Market cars. I figured that change would happen in 1974 with the 5 MPH bumper law came into effect.

I have a copy of the PBS book that I bought in 1979! I will take a look at the steering rack mounts. I would be surprised if the same change would be right for a 128. I would have to determine the correct placement. Sadly, I have not mastered the suspension geometry modeling programs.

I will post a picture of the spindles when I get them back. Basically, the lower control arm attachment point will be about 1 3/8" lower (35 mm) than standard. That means I can lower the car that much and the lower control arm angle and camber gain curve will be the same as original. This is with 14" wheels. You would have to reduce that to 7/8" with 13" wheels. I have a friend in the Alfa racing community who has been modifying Alfa spindles for years. I do not know the process except that an extension is welded in and the spindle re-heat treated.

I knew I was in trouble with bump steer when I read the alignment specs in the factory manual - 5 mm toe out with fluids full and 1 mm toe out with 2 people and 44 lbs of luggage! Toe in on bump is all wrong. I've ordered a bump steer gauge to dial it in, but did not know if the upside down taper could be reamed into the steering arms (if that is necessary - I'm guessing it will be). Where can one purchase those sleeves? I can cut down my tie rod ends or order X1/9 tie rod ends if that drop is about right. I was planning to switch to tapered pins and heim joints and shim them to the correct height. That way I can do it trial and error style instead of being smart and knowing what I am doing!

It sounds like I should set the ride height first, than measure the bump steer to determine if change is needed and how much. Can the steering arms be reamed with the bearings and hubs in place?

But, it's not a race car and I don't expect to lower it more than 2". I am open to suggestions from anyone who has successfully tackled this job.

Thanks,

Chris
 

Dr.Jeff

True Classic
Chris, it sounds like you are on the right track. I'm not the one to advise specifically on 128 stuff unfortunately. But the general info you stated sounds correct. Lower the ride height first, then see which direction and how much the tie rods need to be moved. Your drop spindles should lessen the amount of change needed, so it really depends on where everything ends up after you make all of the other changes. If they need to be lowered enough to do a "flip", then measure the size of the tapered stud and we can compare that to the VW ones. If they happen to be the same size then those insert sleeves are easy to get. I believe they are also available for several other makes of cars, but I'd have not idea what size those would be. But installing them is pretty straight forward. The tapered hole is drilled straight (no taper) and larger diameter to match the OD of the sleeve inserts. That's it.

The change in tie rod length (if any) will depend on how far they are moved (up or down). In some cases they need to be lengthened and in other cases shortened. Again, you will see it once everything else is changed.

I haven't looked at the PBS race mods book for X1/9's in a long time. But in the back of my mind I seem to recall the relocation of the steering rack was a major undertaking? Seems there was a lot of sheet metal changes to the body work or such? But I really don't remember, and it will likely be completely different for a 128 vs a X1/9.
 

fiatfactory

Steve Cecchele
Front driver needs toe out, as with driving forces the wheels will pull themselves in to a toe in situation, then the road forces will spread them back out to straight ahead (hopefully) while travelling.... not enough toe out and the wheels toe in badly during acceleration and the front "hops"

you can improve the 128 a lot by having a damper with quite a stiff extension setting, this helps to negate front end lift and the toe changes associated with that.

Yes 128 front sits WAY higher in the USA and even here in Austraia than the european cars... they have 7 coil front springs and most markets have 8.5 or 9 coils to the front springs. ..usualy first step is to fit 128 COUPE (not wagon) springs (which are 6.5 coils at the front from memory and a much lower arched spring at the rear) and the car drops around 2 inches from the stock heghts, and toe changes are greatly mproved.

When the front struts die on a 128, there can be no sign of fluid loss, the extension stroke just becomes weak and the car lifts excessively when accelerating.

On 105 alfas they extend the upper mount point on the hub to improve the camber curve, doesn't usually invove welding, they bolt an extender into the taper pin hole to effective;y make the spindle longer between the pivots

SteveC
 

Chris Taunton

Daily Driver
Hey
Front driver needs toe out, as with driving forces the wheels will pull themselves in to a toe in situation, then the road forces will spread them back out to straight ahead (hopefully) while travelling.... not enough toe out and the wheels toe in badly during acceleration and the front "hops"

you can improve the 128 a lot by having a damper with quite a stiff extension setting, this helps to negate front end lift and the toe changes associated with that.

Yes 128 front sits WAY higher in the USA and even here in Austraia than the european cars... they have 7 coil front springs and most markets have 8.5 or 9 coils to the front springs. ..usualy first step is to fit 128 COUPE (not wagon) springs (which are 6.5 coils at the front from memory and a much lower arched spring at the rear) and the car drops around 2 inches from the stock heghts, and toe changes are greatly mproved.

When the front struts die on a 128, there can be no sign of fluid loss, the extension stroke just becomes weak and the car lifts excessively when accelerating.

On 105 alfas they extend the upper mount point on the hub to improve the camber curve, doesn't usually invove welding, they bolt an extender into the taper pin hole to effective;y make the spindle longer between the pivots

SteveC

Hey Steve,

So you know about the old Autodelta knuckle risers! That helped the camber but caused all sorts of bump steer issues and the front roll center is crazy low. That is why they run those cars with so much spring and roll bar up front (1300-1500 lbs/in, 29 mm anti-roll bar). The rear roll center is high, so the rear is soft. That is why they you see them cornering with the inside front in the air. If you instead drop the lower control arm attachment point, it brings the front roll center up and the car is much more balanced. Check out the Alfaholics geometry kit for a similar approach.

The coilover set I got uses Koni double adjustable inserts. I will be able to play with the rebound damping.

Some cars need a lot of toe out. I used to run 7 mm of toe out on my 116 chassis Alfa racecar. Going from 1 mm to 7 mm was good for 3 seconds per lap because the car would turn in so much better. I've read that it is a symptom of not enough Ackerman effect, but there are many different opinions about Ackerman. It is beyond my understanding. It seems to depend a lot on roll rate and weight transfer affecting tire slip angles. I've never used data acquisition. It seems you would need hard data to determine what to change. I am not an engineer, just a hobbyist.

With Gus, I plan to start with about 1 degree negative camber and 1 mm toe out and watch tire wear carefully. For track days, I'll bump negative camber to about 2.5 and toe out to 2 mm and see. I have a friend with a 1750 GTV that I hope to surprise.

Thanks,

Chris
 
Last edited:

carl

True Classic
I have to laugh at myself while reading this thread. I had a 128 track day/street car years ago. It had Koni struts from the rear of an X up front and Koni 128 struts on the rear. Lowering blocks with a wagon rear spring. That was it for the suspension. The car was stable on the track but I could never get used to flooring it to go around turns...it would corner on rails when I did this but it just never felt natural to me. Driving on the street was the same, accelerate through the turns. It also had heavy torque steer (1500 motor). I pretty much had no clue what I was doing for chassis set up. Biggest problem was the tripodes coming apart and dumping needle bearings into the trans.
 

fiatfactory

Steve Cecchele
well if you know what the knuckle riser for a GTa looks like, then a pivot drop setup for a 128 is a sort of off the shelf item, from abarth for the Ritmo 130...

I found a picture of what I mean in these Ritmo homologation documents, scroll right down to the addendum and picture 27 is the "alternate" lowered pickup hub for this car, a ritmo 75 (which normally uses a hub/spindle just like an later x19 / very late 128...) remember it's a 1979 production but FWD and used a bearing the same as a 79 x19 , and there are wheel flanges with the correct spline for regular 128 cv joints in this model and a 65CL ritmo too

If you have double adjustable dampers, then you're well on your way to getting the car planted....


SteveC
 

Attachments

  • ritmo ser 1 homologation_form_number_5103_group_a.pdf
    6.1 MB · Views: 151
Last edited:

Chris Taunton

Daily Driver
well if you know what the knuckle riser for a GTa looks like, then a pivot drop setup for a 128 is a sort of off the shelf item, from abarth for the Ritmo 130...

I found a picture of what I mean in these Ritmo homologation documents, scroll right down to the addendum and picture 27 is the "alternate" lowered pickup hub for this car, a ritmo 75 (which normally uses a hub/spindle just like an later x19 / very late 128...) remember it's a 1979 production but FWD and used a bearing the same as a 79 x19 , and there are wheel flanges with the correct spline for regular 128 cv joints in this model and a 65CL ritmo too

If you have double adjustable dampers, then you're well on your way to getting the car planted....


SteveC

Holy cr@p! Does that part have a FIAT part number? Is it available? It is the same idea, but looks stronger than mine.

There has never been "factory" racing parts or support for FIATs in the US. PBS was as close as we got. Most of their stuff was a compromise at best. FAZA sold parts for early cars. Triumph, MG, and later, DATSUN racers had lots of support.

Chris
 

Chris Taunton

Daily Driver
I have to laugh at myself while reading this thread. I had a 128 track day/street car years ago. It had Koni struts from the rear of an X up front and Koni 128 struts on the rear. Lowering blocks with a wagon rear spring. That was it for the suspension. The car was stable on the track but I could never get used to flooring it to go around turns...it would corner on rails when I did this but it just never felt natural to me. Driving on the street was the same, accelerate through the turns. It also had heavy torque steer (1500 motor). I pretty much had no clue what I was doing for chassis set up. Biggest problem was the tripodes coming apart and dumping needle bearings into the trans.

Carl,

That sounds almost exactly like my first 128 (and my first car). I bought it in 1979 and sold it in 1984. I gradually made the changes you did, but mine had a 1300 motor from an X1/9 after I developed a rod knock in the 1100 from starving the oil pickup. It had 13X5" X1/9 wheels with 175/70R13 Phoenix Stahlflex 3011 tires (the hot showroom stock race tire at the time). The car was not fast in a straight line, but did fine on a twisty road and could be slid around nicely in the rain.

Chris
 
Those Phoenix Stahlflex 3011 tires were excellent. I put a set of 185-60/HR13s on my X back in 1982. Also put them on an Audi Coupe I had back then. A friend of mine had a 78 Accord back then that handled like crap with the 155-80/13s it came with. I convinced him to put a set of 185-60/HR13s on it and the transformation was amazing.
 

Chris Taunton

Daily Driver
Drop spindle update: my Alfa friend did not think a drop of more than 1 inch would be safe after inspecting the X1/9 uprights I sent, so we settled on a 7/8" drop so that if I decide to do smaller brake rotors, I can still used 13" wheels. Here is a comparison with one done:

IMG_1751.jpg
 

fiatfactory

Steve Cecchele
Those would not pass engineering certification for road use in Australia, at very minimum not without x - ray and other crack testing, and then probably only after proving strength with a destructive test... personally I would not have a part modified in that manner on one of my vehicles... sorry, just my opinion, YMMV.

For track use only, sure.

SteveC
 

Chris Taunton

Daily Driver
Those would not pass engineering certification for road use in Australia, at very minimum not without x - ray and other crack testing, and then probably only after proving strength with a destructive test... personally I would not have a part modified in that manner on one of my vehicles... sorry, just my opinion, YMMV.

For track use only, sure.

SteveC

Steve,

The laws are much less stringent here. This is amazing, considering our reputation for regulation. I know several people who have used this man's spindles for 20 years on road and race Alfas. I do not know anyone who has had a failure. I am comfortable with his work.

Are you aware of a source for the FIA homologated upright?

By the way, the cylinder head torque tool I bought from you on ebay arrived yesterday. Thanks!

Chris

I
 

fiatfactory

Steve Cecchele
yeah, welll steering com[ponents and modifications to them here in Australia is a bit of a no-no... I 'spose it's related to insurance laws for public liability.

I've hit an upright hard enough to bend it in the area you've extended, and the cast iron bent, it didn't crack... the lower control arm (on a 128 coupe so the same as an X19) bent and deformed but didnt crack.

I'm not even sure you will need the drop spindles to tell you the truth... how low do you want your 128 to be?

If your already going X19 rear struts on the front, your already dropping the car a pretty huge amount...and loosing quite a lot of overall suspension travel by having a shorter strut shaft, you will also need to use the X19 bump stop assembly from a series 1 rear to get the required bump stop height, otherise with the sedan bump stop / top mounts you'll be riding on the bump stp rubbers.... the struts you'll be using also have quite a lot of camber built in compared to a 128, and a load of adjustment in the elongated upper hole.

Just be warned a 128 sedan front chassis is no where near as stiff in the chassis on the front of an X19... there is a lot of flex...more in an older body and they do tend to crack.

SteveC
 
Top