Unacceptable Steering Angle

[Colin Fabri]

I am close to registration for my RCR 40 and have been testing my vehicle (on private roads :shifty and have a major issue to resolve before I can drive safely. The maximum steering angle I can get is approx 15 degrees and means that when turning at an intersection I have to go to the wrong side of the road due to lack of steering angle. My understanding is that typical steering angles on vehicles are between 20 and 25 deg.





My front wheels are 18 x 8 inch and as 8 inch wheels are specified as an option for the vehicle, I am confused as to why it is such an issue on my build. The wheels are custom made 2 piece Simmons brand. Moving the wheels out with spacers would mean the front track would exceed the rear, so not keen to do that.

Before I blow additional money and buy skinnier front wheels, I am looking to see if there are other suggestions?

Thanks
Colin

 

[Terry Oxandale]

Tough situation. You may gain a few more degrees by threading the inner Heim joints all the way into the arms so that the arm is drawn closer to the tub, and at the same time thread the outboard ball joint out to end up maintaining the current camber/geometry. In other words, use the joint position to move the aluminum arm further inboard. It won't get you much, but a little in that are could go a long ways on angle. It looks like you've got quite a bit of thread left on the rear inner Heim to do this.

I'm not familiar with the RCR arms, so one question is: are the arms symmetrical left to right, top to bottom? I they are, not much left to do in regards to positioning. Lastly, re-fabricating a set of brackets that move the axis of the inner Heim closer to the tub panel could be a last resort action to allow my above suggestion to gain even more clearance, and thus more turn angle.

 

[Fran Hall RCR]

Colin,
having never ever built or supplied an RCR40 with 18 inch wheels or with the SLC type Brembo brakes you have on there its impossible for me to give you much input...although Id like to help obviously.

Is the caliper or wheel hitting the upper control arm ?
Is the tyre contacting the front of the monocoque chassis?

Can I ask why you went with the 18 inch wheels ?

 

[Jac Mac]

You would blow a lot less money by simply making a couple of new top w/bones with a lot less bulk at that point, compare them to original GT40 items for example. Also note the orientation of the fitting for top ball joint.

 

[Ron R.]

Tough situation. You may gain a few more degrees by threading the inner Heim joints all the way into the arms so that the arm is drawn closer to the tub, and at the same time thread the outboard ball joint out to end up maintaining the current camber/geometry. In other words, use the joint position to move the aluminum arm further inboard. It won't get you much, but a little in that are could go a long ways on angle. It looks like you've got quite a bit of thread left on the rear inner Heim to do this.

I'm not familiar with the RCR arms, so one question is: are the arms symmetrical left to right, top to bottom? I they are, not much left to do in regards to positioning. Lastly, re-fabricating a set of brackets that move the axis of the inner Heim closer to the tub panel could be a last resort action to allow my above suggestion to gain even more clearance, and thus more turn angle.

I think Terry may be on to something. Perhaps you can find some off-set heims to use on the outer joint to further space the upright away from the arms. It might be worth a look. (at the same time, pull the inner heims in, so that your wheel doesn't end up spaced out relative to the body)

 

[Colin Fabri]

Thanks for the replies guys. I will wind in the heim joints and see how much increase that gives. I also noticed while looking at the #6 Gulf car on the RCR website that the outer edges of the front and rear wheels are further out than mine and this would contribute to the issue as well.
I am keen to try moving them out with spacers, anyone got any opinions of spacers relating to safety or any other issue?

Fran, the rear top edge of the wheel is touching the upper control arm and the tyre does not touch anything. I had previously added steering blocks on the steering shaft to stop the wheel grinding the control arm, but of course this just protects the wheel not affecting max steering angle.
I specified the 17 inch wheels to the wheel maker (Simmons) however they decided there was not enough clearance from the inner part of the wheel to the 348mm discs on my car. This brake setup was provided as part of the rolling chassis as sold to me by RCR Australia back in 2011.

Regards

Colin

 

[Scott]

OP,
Spacers are fine as long as they are high quality and properly torqued. (the BRM replica wheels with center-lock and pin drive all use them) That is probably the easiest way to get a few more degrees of turning radius. It is also possible your wheels have too much back-space. I'm sure Fran can post-up the stock back-space measurement, I don't remember what it is at the moment. S

 

[Colin Fabri]

Thanks to all for the replies. Some feedback for you.
I moved the top rear heim joints all the way in and the front ones out to compensate. This increased the steering angle from 15 to 19 degrees and made it much better when turning out from an intersection.
Additionally I have ordered 15 mm spacers which will hopefully get me in to the '20's' for a more normal degree of steering angle.

Next step is to get a wheel alignment, after rego (hopefully) this week.

Regards
Colin