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RSR Lower spindle gussets - Necessary retrofit ??

I have RSR's with raised spindles that have been on the car for 7-8 yrs . The car handles very well
The spindles do not have the lower gussets welded on them that both Rebel and Elephant Racing offer as an option for Track duty.
Is there a valid reason to add them at this point? Do they reduce a stress point that was unknown 7-8 yrs ago??
Is there a potential fatigue issue I may be facing without them ?
Appreciate any on track data /comments/input.

Thanks
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Old 03-27-2018, 06:39 PM
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I've seen a standard spindle come adrift. Took the wheel, tire, brake, and everything with it. Damaged the fender before it completely bounced away, and of course there was abrasion on the button of the right-front corner.

This was a car that had been actively tracked for at least a couple of decades by that point.

I don't know if there are any weak spots in the RSR-type setup, but I figure that a little more bracing probably couldn't hurt...

--DD
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Old 03-27-2018, 07:06 PM
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Quote:
Originally Posted by Dave at Pelican Parts View Post
I've seen a standard spindle come adrift. Took the wheel, tire, brake, and everything with it. Damaged the fender before it completely bounced away, and of course there was abrasion on the button of the right-front corner.

This was a car that had been actively tracked for at least a couple of decades by that point.

I don't know if there are any weak spots in the RSR-type setup, but I figure that a little more bracing probably couldn't hurt...

--DD
Marcel! At the Oakland Coliseum a long time ago!!! Neil Jackson had to run for cover!
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Old 03-27-2018, 10:03 PM
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Quote:
Originally Posted by betterair View Post
I have RSR's with raised spindles that have been on the car for 7-8 yrs . The car handles very well
The spindles do not have the lower gussets welded on them that both Rebel and Elephant Racing offer as an option for Track duty.
Is there a valid reason to add them at this point? Do they reduce a stress point that was unknown 7-8 yrs ago??
Is there a potential fatigue issue I may be facing without them ?
Appreciate any on track data /comments/input.

Thanks
Are you talking about these:



I would skip them. You want that steering arm to bend if you hit something with the wheels. With that bracket welded in place, something else is going to have to give instead. That would not be pretty....
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Old 03-27-2018, 10:13 PM
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Scott,

Yes, those are the brackets that I see being promoted for use with RSR' and sport struts for track duty.
So, additional rigidity ( lower mounting gusset) is not necessary in your opinion ?
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Old 03-28-2018, 03:38 PM
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Scott,

Yes, those are the brackets that I see being promoted for use with RSR' and sport struts for track duty.
So, additional rigidity ( lower mounting gusset) is not necessary in your opinion ?
No, not at all. My race car does not have them and I run massive 12" tires up front on 11" wheels. My car is quite low too.

The guy that built my race car has a bunch of cars out there like mine with bump steer kits with no brackets welded in place. It's better to bend the steering arm when you contact something than the other stuff that would have to give way with the brackets in place.
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Last edited by winders; 03-28-2018 at 04:34 PM..
Old 03-28-2018, 04:30 PM
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I'd agree with Winders that the gussets aren't usually necessary. I've run wide slicks on the front of my 914 for many years, and have never bent my steering arms or seen evidence of flexing.

Are you running a large number of spacers between your steering arm and the tie rod? From memory I think for my car I have a 1-2 inches worth to get bump steer set. I used 1" diameter spacers to distribute the load and then a conical spacer right before the tie rod end.

Scott
Old 03-29-2018, 07:42 PM
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To tell the truth , I haven't checked the spacer stack height .
The suspension was set up at th same time the rack was rebuilt,spindles raised,and bumpsteer set by a well regarded shop.The car handles very well.

My question about The lower gussets was prompted by the fact that I see them being promoted and I was curious if people had seen the need for them as a result of moderate - heavy track use.
I am going to take your recommendations and leave well enough alone ,especially since it's time to have the car alignement checked,so and I will put the $$ in the alignment where it will yield better results than steering arm gussets ,that may not improve an already tried and proven design. In addition I am only running 7 inch and 9 inch tires and only running 5 to 6 events a year.
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Old 04-01-2018, 09:21 AM
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I was always under the impression that without the gussets the tie rod end can move back and forth messing up the alignment when braking hard, then it going the other way when you accel, my friend installed his without the brace and hated it he's an alignment guy and said no way is this right, everyone has his opinion I guess
Old 04-01-2018, 09:51 AM
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Quote:
Originally Posted by rkeele View Post
I was always under the impression that without the gussets the tie rod end can move back and forth messing up the alignment when braking hard, then it going the other way when you accel, my friend installed his without the brace and hated it he's an alignment guy and said no way is this right, everyone has his opinion I guess
How can the tie rod end move back and forth messing up the alignment???

What does an alignment guy know about what is right or wrong in regards to how the tie rod attaches to the steering arm on the strut?
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Old 04-01-2018, 12:00 PM
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Wait, are we talking about gussets for the spindle-to-strut connection, or are we talking about gussets for the steering arms? I had thought we were talking about the former, but people are discussing steering stuff now...

For the steering arm stuff, I would think that an unsupported long bolt that cantilevers the connection between the outer tie rod and the steering arm in single shear might result in some loss of steering feel and in extreme cases add significant slop. Supporting that in double shear sounds like a pretty good idea, though the points about what you want to be damaged if you ever have a wheel go where it shouldn't be are valid. That would tend to point to some other way to deal with bump steer being preferred...

--DD
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Old 04-01-2018, 02:17 PM
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Quote:
Originally Posted by Dave at Pelican Parts View Post
Wait, are we talking about gussets for the spindle-to-strut connection, or are we talking about gussets for the steering arms? I had thought we were talking about the former, but people are discussing steering stuff now...

For the steering arm stuff, I would think that an unsupported long bolt that cantilevers the connection between the outer tie rod and the steering arm in single shear might result in some loss of steering feel and in extreme cases add significant slop. Supporting that in double shear sounds like a pretty good idea, though the points about what you want to be damaged if you ever have a wheel go where it shouldn't be are valid. That would tend to point to some other way to deal with bump steer being preferred...

--DD
If you read the thread, you would know we are talking about the brackets for the steering arm.

You think there could be loss of steering feel and significant slop? Why?

I run the worse case scenario with the equivalent of 305mm tires up front on a really low car with a wide front track. My car has fantastic feel and precision. Slop? It's no where to be found and my setup is all heim joints. I'd know if there was slop.....
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Old 04-01-2018, 02:56 PM
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Quote:
Originally Posted by winders View Post
If you read the thread, you would know we are talking about the brackets for the steering arm.
My first post was the first response to the thread--there was no thread when I posted it. I finally figured out everyone else seemed to be talking about something other than I was, and was trying to make sure what the actual discussion was about. If you read the thread, you might see my confusion...


Quote:
You think there could be loss of steering feel and significant slop? Why?
If someone were to use a 4" lag bolt to go from the steering arm to the tie rod, the slightest imperfection in the interface between the steering arm and the bolt (e.g., a slightly ovaled hole) or the slightest looseness there would be significantly magnified.

If yours doesn't, then either your setup is better than what I was imagining, or you have a completely perfect interface between the bolt (or whatever is used there) and the steering arm.

--DD
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Old 04-02-2018, 01:44 PM
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Exactly my thoughts Dave, makes sence to me, but if it feels good to winders that's ok also, whatever every one has an opinion, I'm thinking if I were to run into something that hard to where I'm breaking the front strut then I've got bigger problems then that.
Old 04-02-2018, 04:47 PM
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Geez, Dave, if you read the posts after your first post and before your second, the answer is there.

Anyway, it’s not just a bolt hanging out in two holes. There are a bunch of larger spacers between the steering arm and the tie rod end that are held in compression by a bolt and nut. That interface allows for no slop so only bending forces are in play. You would have a hell of time causing any deflection in that setup with the car moving without hitting something. When the car is moving it does not take much force to turn the wheel. If you hit something, the steering arm bending is better than destroying the rack or pinion gear in the steering rack or severely bending a wheel.

This is a case where over engineering something is not good.
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Old 04-02-2018, 10:56 PM
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My car was built by the same person that built Scott's. He is a friend and very experienced and accomplished. Former IMSA pro and 40+ years of experience including with teams running factory cars.

In any case, I run the same tires as Scott. Very big and very sticky. And Bilstein RSR front struts, with the spindles raised for the 16 inch wheels and low ride height. And the steering arms bent by the builder.

I have had my car for 15+ years. In the beginning I did not have a bump steer kit, just some washers spacing my steering rack upward. After about 5-10 years, I added the Eisenlohr Racing Products (ERP) bump steer set up. There are others, but I trust ERP. If I were to buy now, I'd only consider ERP or maybe JWE parts.

This Spring I am going to optimize my bump steer very, very carefully. This is not typically done at the amateur level.

In any case, like Scott I do not have any bracing. No fatigue or any other issues.

I have seen some extreme examples of spindle raising in 911 family cars-- for much larger diameter wheels. And on some of these pro-built cars, I have seen the added bracing.

As I say with some regularity in these posts, I like to get perspective from people with significant racing experience. The person that built my car has this. The folks at JWE have this. Cary Eisenlohr (ERP) has this. If I were in PA, I might check in with Dawes.

I do not know how much actual racing experience Rebel Racing has. I like many of their products. As for Elephant Racing Products, there is no racing experience. Some great products to be sure.

For racing applications, I think it pays to get advice from people with tons of experience with trailing arm 911 racing.
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Last edited by Mahler9th; 04-03-2018 at 08:43 AM..
Old 04-03-2018, 08:39 AM
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Not to put too fine a point on it...

The OP has not stated how much his spindles may have been raised. And has not stated whether he has a bump steer kit installed.

Even without a bump steer kit, omission of extra bracing is very common with cars built by experienced pros.

The incident to which Dave referred occurred at an AX. Scott and I were there. Neil J. was there. Oakland CO Colliseum parking lot.

Spindle failed (age, fatigue).

Scott has the somewhat unique experience of having an SC-style front hub and a 930 rear hub fail while on track in recent years. My car experienced an SC-style rear hub/stub axle failure whilst on track under load back in 2009. Wife as driving.

Unlike Scott's experience, our case resulted in quite a bit of damage.

We have to remember that many of these parts are really, really old.
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Old 04-03-2018, 08:48 AM
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"This Spring I am going to optimize my bump steer very, very carefully. This is not typically done at the amateur level."

Wish I knew more?
My upcoming front shock upgrade, raised spindle build and alignment is to include a"Bump Steer Graph" along with the corner balance results.

Want to try to understand the graph though???
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Old 04-03-2018, 01:25 PM
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There are quite a few resources that can provide perspective on bump steer. One of my favorites is the Puhn book "How To Make Your Car Handle."

Highly recommended.

Note that the car on the cover was campaigned by a local team that was heavily supported by PCA volunteers. Bruce Anderson, Jerry Woods and other famous pcar experts were a part of that racing effort. My friend/car builder/engine builder (to whom I referred earlier) was also a part of that shop back in the day.

In any case, if have not found a specific bump steer recipe for 911 race cars-- I think there are too many variables for there to be a single answer.

The answer that I am going to strive for will be based on advice from my friend.

It will be painstaking since I will have to make a bunch of toe measurements through an extended range of travel. Made easier because I have coilovers, AND a way to attach my measurement string set up to the car, similar to Craig Watkins' SmartStrings. I already have a bunch of shims I will use to make adjustments.

Hmmm... Craig, who was Chief Engineer for the Lizards is an old friend and is now racing again with us in his retirement. I wonder what bump steer curve he strives for... will need to ask him.

By the way, he wrote a book recently-- essentially reporting on his many collaborations with Roland Kussmaul. I have not started reading it yet. But it would not surprise me if bump steer is mentioned.

I have heard that some shops do light duty bump steer work with the cars on an alignment rack... they pull down the nose to see how toe changes. Not so sure the extra $$ they may charge for that would make much of a difference.

I see bump steer tweaking as a transfer function... meticulous effort and time can yield some pretty impressive results in handling.... but you have to be realistic.

In theory you could have a model of a 911 suspension with a family of known parts and model bump steer. I imagine they have such models at high levels of professional racing.
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Old 04-03-2018, 02:28 PM
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I don't know of a simple way to properly bump steer a car. The process I'm familiar with goes something like this:
1. Measure strut extension/height at desired ride height.
2. Remove spring on one side. This assumes coilovers of course. Maybe you could remove a torsion bar on a torsion-sprung car? Not sure about that ...
3. The next step will be to put the car on jack stands, set the suspension to "ride height" using a jack under the suspension, and measure toe change as you move the suspension through its range of suspension travel using the jack. Remember to measure for droop travel and not just compression travel, since the suspension goes in both directions during regular driving.
4. There are various ways to measure toe change as you move the suspension up and down - toe plates, laser measuring devices, etc. Google will be your friend to understand the options.
5. Ultimately you are trying to minimize toe change with suspension travel. It won't go away entirely, so there will be some bump steer still. On a lowered car you'll be adding spacers between the strut and the tie rod end to accomplish this. It's pretty much trial and error, but once you're all set up it's easy to add or remove spacers and re-measure.
6. I just measured one side of my car and duplicated the setting on the other side. I suppose you could measure both sides if you wanted.

I believe there are some different practices re: how you want toe to change to aid in turn in, etc. I've just kept it simple aimed to minimize the toe change to as close to zero as possible.

Scott
Old 04-06-2018, 06:38 AM
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