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Either. You need to able to recognize what bump steer feels like and how it manifests on track. Make an adjustment, drive it, see how it feels. Know that there is no "perfect" rack height as the curves crossover each other. On a street car, you want it the steering to be neutral on gentle bumps, well above the bump stops. On a track car, I focus more on how it feels further into the travel, closer to the bump stops.
Most NA/NB drivers with really low track cars just don't notice or even realize that wheel tugging back and forth in fast sweepers is bump steer, probably assuming its just stiff springs or bad shocks. Drive a properly set up car (any brand/model) though, and the steering is "calm" through those same fast lumpy sweepers.
That's the long answer. Short answer is..experiment. If I had to recommend a starting point, any car below 5.5" pinch weld heights should use the R pkg OTR geometry at minimum. Below that height, we also space the rack up 1/4". Actually have a product planned for that, on the list for like 6 years. Prototypes in the shop, never finished and put into production. But you can make your own. NA particularly easy.
Either. You need to able to recognize what bump steer feels like and how it manifests on track. Make an adjustment, drive it, see how it feels. Know that there is no "perfect" rack height as the curves crossover each other. On a street car, you want it the steering to be neutral on gentle bumps, well above the bump stops. On a track car, I focus more on how it feels further into the travel, closer to the bump stops.
Most NA/NB drivers with really low track cars just don't notice or even realize that wheel tugging back and forth in fast sweepers is bump steer, probably assuming its just stiff springs or back shocks. Drive a properly set up car (any brand/model) though, and the steering is "calm" through those same fast lumpy sweepers.
That's the long answer. Short answer is..experiment. If I had to recommend a starting point, any car below 5.5" pinch weld heights should use the R pkg OTR geometry at minimum. Below that height, we also pace the rack up 1/4". Actually have a product planned for that, on the list for like 6 years. Prototypes in the shop, never finished and put into production. But you can make your own. NA particularly easy.
Thank you for the info. I hadn't fully considered how big of an issue bumpsteer could be on these cars until I saw a photo of me at my local track (Brands Hatch). Paddock Hill bend has a huge compression (Xida race 700/400 4.5" pinch weld + 9J 6UL will have tyre to arch contact here) and it appears that I'm steering right, but the wheel is not! (NA OTR, 1/4" rack spacer)
If you get R-Package tie rods from Mazda I bet you dont get any bump steer
Not quite sure how to read this... I know NB front suspension with R-package ball joints is the best, but are you saying NA with rack spacer and ball joints is still bad?
Not quite sure how to read this... I know NB front suspension with R-package ball joints is the best, but are you saying NA with rack spacer and ball joints is still bad?
I'm saying if you and E both got legit r package toe rods the rack spacer is pointless.
Most NA/NB drivers with really low track cars just don't notice or even realize that wheel tugging back and forth in fast sweepers is bump steer, probably assuming its just stiff springs or back shocks. Drive a properly set up car (any brand/model) though, and the steering is "calm" through those same fast lumpy sweepers.
Finally installed my tie rod ends from Supermiata, and all that bump steer is gone. Very underrated upgrade for depowered steering racks. *EDIT* Checked my notes, and I sourced them from somewhere else. They were OEM R-package.
Any suggestion on when to re-grease uppers? I take it that grease zerk isn't for show.
Last edited by moocow; Jun 28, 2019 at 06:11 PM.
Reason: Fix source!
Finally installed my tie rod ends from Supermiata, and all that bump steer is gone. Very underrated upgrade for depowered steering racks.
Any suggestion on when to re-grease uppers? I take it that grease zerk isn't for show.
Bruh it's a placebo. They are pro forged tie rods that do not have R Package geometry.
We have a simple Longacre Bump Steer gauge that's been used to measure many cars over the years, both front and rear. It's useful for us to learn how to correlate how the suspension feels to what the actual bump steer curve looks like. Many light bulb moments when looking at the resultant spreadsheet plotted curve after driving the car. Also interesting to see various OEM tuning philosophies. The AP1 S2000 vs and NA vs and ND1 for example. Wildly different curves that each impart specific handling characteristics. The rear of the ND1 for example, is wonky curve that explains why the car gets so squirrelly in lumpy turns when you add stickier tires to the stock suspension. Stay with slippery OEM tires that don't generate much roll moment and it's a much better balanced and predictable car. AP1's curve clearly explains why it is trying to kill you most of the time. NA's explains why it is so sweet and predictable. Factor in bushing deflection which also affects toe angle and you have a complex mix of factors to deal with when trying to sort out the best handling with high grip tires.
Bruh it's a placebo. They are pro forged tie rods that do not have R Package geometry.
I don't believe that is accurate, I have a set of tie rod ends I ordered a month ago and haven't installed yet, here they are compared to a photo of Proforged tie rod ends on Rockauto. I have a digital caliper on hand if anyone wants me to measure stuff, they look almost identical in dimension to R Pkg Tie Rod ends from what I can tell, but I don't have any on hand to compare.
When I was in the market to buy 93le style tie rods, Supermiata's website seemed a bit ambiguous as to what I would be receiving. I found this website that makes it clear that they offer a 93le style tie rod. https://cdn11.bigcommerce.com/s-79xy...=2&imbypass=on
It would have helped decision making if Supermiata had a side by side comparison of what they sell versus a non 93le option like what is shown below.
Originally Posted by emilio700
Can't tell from pics. We have all the relevant OEM Mazda parts and have measured on the bench. Pretty clearly defined and repeatable, no ambiguity.
My question would be, what can I not tell? that these two tie rods are not the same tie rod or that they are 100% identical? Because I can see a difference between the two.
The angle of the tie rod end doesn't do anything for the bump steer. It only effects the working angle which could reduce binding in some situations. The critical dimension is from the pivot to knuckle.
The angle of the tie rod end doesn't do anything for the bump steer. It only effects the working angle which could reduce binding in some situations. The critical dimension is from the pivot to knuckle.
Are you suggesting that a measurement such as this would be irrelevant then?
Are you suggesting that a measurement such as this would be irrelevant then?
Yes. You could make a tie rod a curly Q, but it only acts from the pivot on the ITR (rack end) and the ball joint on the ORT (knuckle). In simplified suspension models, its just seen a straight line. Other features of the tie rod ends are to avoid contact with other items or prevent binding at extreme angles of travel.
After cutting up and measuring standard, R-package, and our forged tie rods, we have discovered that our offering is not fully R-package geometry as we had believed and have updated our website to reflect that. The geometry falls between R-package and standard geometry. So there is still a mild improvement in bump steer characteristics on lowered cars, combined with the benefit of a stronger part. OE replacement, stronger forged parts. Tough to cut open!
We know adding 1/4" (6.35mm) rack spacers reduces bump steer even with R pkg OTR's so we're now gathering data to see if a new, even more offset OTR will have the same benefit as rack spacers.
That will take a while. We'll publish more data when we have a more complete picture.
After cutting up and measuring standard, R-package, and our forged tie rods, we have discovered that our offering is not fully R-package geometry as we had believed and have updated our website to reflect that. The geometry falls between R-package and standard geometry. So there is still a mild improvement in bump steer characteristics on lowered cars, combined with the benefit of a stronger part. OE replacement, stronger forged parts. Tough to cut open!
We know adding 1/4" (6.35mm) rack spacers reduces bump steer even with R pkg OTR's so we're now gathering data to see if a new, even more offset OTR will have the same benefit as rack spacers.
That will take a while. We'll publish more data when we have a more complete picture.
Great to see you trying other geometries. If you can specify your own geometries, have you considered extended lower ball joints with some roll center correction added too? Ie offset the ball vertically as well as axially.
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