Bumpsteer & offset rack bushings - Mark IV

[COBRA_DUDE]

If you are running solid offset rack bushings and get that dialed in / in alignment (or at least very close), do really still need bumpsteer kit to eliminate that issue? Do you need to run both on a Mark IV?

[LuckyWinner]

I have the same questions.......

[Martin]

I've been told you don't need the bump steer kit if you use the offset bushings.

Don't take my word for it though, I hope someone else will chime in.

Martin

[Raceral]

I surely thought all this has been corrected.

[MPTech]

I understood the complete kit with the redesigned spindles eliminated this issue.
If you are running the donor sn95 spindles you may still have it, but the offset bushings improves, but doesn't eliminate it.

That's what I understand.

[Bob Russel]

At the build school we spent some time talking about this and per the recommendation of the instructors, I purchased these from Breeze.
http://www.breezeautomotive.com/details.php?prod_id=139
Great instructions, easy to install and not that much $$$ for the peace of mind.

There are folks that say you don't need them, but when I heard the instructors recommend them (and they only recommended a couple of items) I took it as a must have.

Good luck.

[MPTech]

Yep, those came recommended to me as well from forum sources.

Did the Build School recommend anything else?

[LuckyWinner]

At the build school we spent some time talking about this and per the recommendation of the instructors, I purchased these from Breeze.
http://www.breezeautomotive.com/details.php?prod_id=139
Great instructions, easy to install and not that much $$$ for the peace of mind.

There are folks that say you don't need them, but when I heard the instructors recommend them (and they only recommended a couple of items) I took it as a must have.

Good luck.

I went to that site and it is for MK I & II. I have a MK4 just trying to find out if I need anything to make steering better or if all problems have taken care of.

[Bob Cowan]

According to FFR, with the new spindles, a-arm mounting points, and new steering rack, all that has been corrected. no need for new rack bushings, bump steer kits, or SAI kits. I think some autocrossers are still moving the rack back a bit to improve Ackerman, but that's a use specific mod.

[gtcobra]

I have a MK4 with the Breeze bushings, I used donor spindles (sn95) and also used the SAI mod from Whitby's. Car is very well sorted, handles great with no issues regarding bumpsteer.
I did not do the bumpsteer measurment, however, I drove the car and was extremely happy with the results. I do not think you will have any issues with bumpsteer, particularly if you are using FFR spindles. JMHO

[Jeff Kleiner]

I recently completed a Mk4 for a customer using FFR spindles and a power rack with extenders set in the standard position with no offset. Running +8 degrees caster, -1/2 degree camber and 1/16" toe in there is no bumpsteer.

Cheers,
Jeff

[Todd Baumann]

At the build school we spent some time talking about this and per the recommendation of the instructors, I purchased these from Breeze.
http://www.breezeautomotive.com/details.php?prod_id=139
Great instructions, easy to install and not that much $$$ for the peace of mind.

There are folks that say you don't need them, but when I heard the instructors recommend them (and they only recommended a couple of items) I took it as a must have.

Good luck.


All right, let me clarify this.
We do not recommend arbitrairily just buying this kit from Breeze. Although it is a very good kit.

Now with that being said, what we do say is that with the MKIV kit and FFR
components you are suppose to not need the kit. Bumpsteer is supposed to be eliminated.
But, with our class car and our setup we still exhibit bumpsteer, and by using Mark's offset bushing kit we then can
get rid of almost every bit of it. Mark's kit is a much easier and cost effective way to improve this condition.

And to add to that we always state that every car is different with wheels, tires, alignment settings,
shocks, shock settings, ride height, etc. and you need to measure your car, and then determine what is needed for your setup.
Hope that clarifies things for everyone.

[CraigS]

The key in Jeffs comment above is the 8 deg caster. As you til the top of the spindle rearward, the end of the steering arm moves upward. So there is less need to lower the rack.

[mike forte]

Hi,
Measure for bumpsteer and you'll see if you have it. Getting a car all together & driving and not knowing the amount of bumpsteer is an unknown question that will then be answered when you drive over dips in the road. Not the best place to find if you have bumpsteer or not. Measure measure measure...

[QUOTE=
And to add to that we always state that every car is different with wheels, tires, alignment settings,
shocks, shock settings, ride height, etc. and you need to measure your car, and then determine what is needed for your setup.
Hope that clarifies things for everyone.[/QUOTE]

[CraigS]

OTOH, if you drive your car moderately fast on a country road that has only gentle turns but a bunch of bumps (not potholes just bumps that move the front wheels at different rates and times) and the steering wheel stays steady over the bumps, then don't worry much about bumpsteer.

[Howie]

So another question on this....If I'm using the stock donor steering rack and donor 95 spindles, is it recommended to install the factory five bump steer kit from the start?

[PaulW]

I went to that site and it is for MK I & II. I have a MK4 just trying to find out if I need anything to make steering better or if all problems have taken care of.

Breeze has the bushings for the Mark 4 as well. I know because a pair just arrived this week.

[rich grsc]

So another question on this....If I'm using the stock donor steering rack and donor 95 spindles, is it recommended to install the factory five bump steer kit from the start?
NO. Dont go buy parts to fix a problem you may not have. READ post #12, its good advice.

[Howie]

okay I read it and understand but Todd refers to the set up on the MkIV with FFR components, I have '95 donor spindles and rack and haven't bought the tie rod ends yet, hence the question....
thx

[Lynnhowlyn]

I recently completed a Mk4 for a customer using FFR spindles and a power rack with extenders set in the standard position with no offset. Running +8 degrees caster, -1/2 degree camber and 1/16" toe in there is no bumpsteer.

Cheers,
Jeff

Jeff - any guidance on cutting (shortening) of the inner tie rods - e.g. how to determine how much to cut when using the FFR spindles, a power rack and the extenders?

Or is it truly just "trial-and-error" .... starting with 'just a bit' ( like perhaps 3/4 inch) since once a cut is done, it can't be added back?

Thanks

Lynn

BTW - thanks for the guidance on alignment settings!

[Jeff Kleiner]

I'm reluctant to say "how much" because of the variations among tie rod end and rack manufacturers but I'll tell you how to determine what you need to do.

Measure the depth of threads inside the outer tie rod and mount it to the spindle (don't fully seat it on the taper yet). With the rack centered raise the suspension so that the lower control arms are completely horizontal, as they will be at ride height, and the wheels are pointing straight ahead. Hold the inners up against the outers and make a reference mark on the inner threads where the end of the outer is. From that mark measure outward the distance of the threads inside the inner. Get it? You're just working backwards. This is the maximum length the inners can be before they bottom out. Cut the inner a little shorter (~1/4-3/8") so that it won't bottom out when completely adjusted. As long as that leaves an inch or greater (minimum of 2 times the diameter) of threads from the inner tie rod engaging inside the outer you're golden!

Make sense?

Although I commented earlier when this topic first came up several weeks ago, since its one of my pet peeves I'll go back to bump steer again. Like Rich, Mike, Todd and others have said---don't just arbitrarilly throw a bump steer kit or some other "correction" on until you know if you have a problem. That's like having bypass surgery just in case you have a blockage! Build the suspension, do a rough alignment, MEASURE FOR BUMP STEER, then address it if necessary.

Good luck,
Jeff

[Lynnhowlyn]

Thanks Jeff!
Your response - e.g a process or procedure to help me determine (measure) how much to cut is exactly what I've been looking for.
And I completely understand (and agree with) your comments re: "bump steer" and what to do about it in advance. My understanding is that "bump steer" has been essentially eliminated with the Mk4's - esp with a complete kit (FFR control arms and spindles etc) and for any individual build, there may be NONE when the car is completed.

Thanks again for the help on the tie rod length question.

Lynn

[FFRSpec72]

As part of the Challenge Car (Spec Racer) upgrades being made for 2012, we can now run the MkIV spindles, when asked the question about the bump steer , I got the response of "new spindles should still be used with the bump steer kit to be able to fine tune things". So I will install w/o bump steer and see how things align, as I really don't want to drill for bump steer if I don't have to

[Jonweisw]

I used the Breeze offset bushings following my experience at the Build School on my MkIV. I did the alignment without them and then with them and it clearly made a difference.

See my writeup here: http://factory5roadster.wordpress.com/2011/03/15/3-14-11-coarse-wheel-alignment/

Jon