RCR40 Clunking in Floorboard/Pedal Box Area

[Pasha Saleh]

I have noticed when rolling the car at pretty much any speed there is a "clunking" that you can feel with your feet in the pedal box area. Yesterday my passenger felt it as well in the other seat. All wheel suspension components are confirmed to be firmly secure and I wonder if it could be the sheet aluminum floor flexing?

Anyone experienced something similar and what was the remedy?

 

[Chris Kouba]

Is it a sharp noise, like a loose heim joint as the suspension articulates? I had that from the front end of mine and this post explains what I did:

Post in thread 'Rcr 40-31'

Feb 22, 2016

Success...

• ckouba

There was slack in the lower inboard A-arm pivots and with the CNC'd attachment pocket, there was not enough flex to crush the spacer washers together. This resulted in a knocking sound which sounded like a bad heim joint.

Could that be your issue?

 

[Randy V]

Is it a sharp noise, like a loose heim joint as the suspension articulates? I had that from the front end of mine and this post explains what I did:

Post in thread 'Rcr 40-31'

Feb 22, 2016

Success...

• ckouba

There was slack in the lower inboard A-arm pivots and with the CNC'd attachment pocket, there was not enough flex to crush the spacer washers together. This resulted in a knocking sound which sounded like a bad heim joint.

Could that be your issue?

Also - many of the GR8 bolts supplied with mine, were coarse thread and lacked the appropriate shoulders that the heim joints should ride on. If the heim is on the threads, there will be too much tolerance..

 

[Pasha Saleh]

I wouldn't describe it as a sharp noise -- more a bending/flexing feeling under foot. I will try to replicate it while somehow being able to observe what's going on if that's possible.

 

[Ian Clark]

It's a tricky one because identifying the source of the noise, unless painfully obvious, is a process of elimination.

As Chris said a sharp comes from lighter parts such as washers and mounting bolts or bolted in place inboard mounting points for the front lower control arms. A finicky place to work and tricky to assemble, been there done that.

With hundreds of hours spent on RCR cars across the MK1 MkV1 Susperlite and 917 I can vouch for the quality of RCRs components.

The owner/builder chooses the parts not included in the kit (drivetrain etc) and anything else that he might want at ad or upgrade. That's the beauty of building your own car

Extreme care attention to assembly tolerances, sequence of assembly and proper tightening of nuts/bolts/washers is paramount
for safe operation of any car on the road or track. And these are extreme performance cars without a doubt

A lower frequency clunking or thumping sound usually comes from heavy parts as in the drivtrain OR a suspension corner (every part may be involved from the wheel tire/axle & bearings, upright attachment points, all suspension pivotsrod ends/monballc/clevis pins, shock absorber mounting barings or bushings mounting bolts and attachment points).

Just so I don't jump to conclusions, are you hearing a sound eminating from the foot box area and simultaneously feeling the floor of the car flex under your feet or seat? Did you feel any vibration through the steering colum or wheel when the clunking is heard?

Cheers
Ian

 

[Ian Anderson]

Loose steering rack?
Anti roll bar….. some run under the car….is yours and then flexing on the mounting locations?

Ian

 

[Bill Kearley]

Or, pads / caliper ?

 

[Jean-Marc]

The best would be to place te car on a vibrating bench. Around you is there any garage that has the type of bench use to check suspensions on cars?
In Europe because it is mandatory to check cars periodically for secrurity, we have plenty of "technical control shop" equiped with this.

 

[Pasha Saleh]

It's a tricky one because identifying the source of the noise, unless painfully obvious, is a process of elimination.

As Chris said a sharp comes from lighter parts such as washers and mounting bolts or bolted in place inboard mounting points for the front lower control arms. A finicky place to work and tricky to assemble, been there done that.

With hundreds of hours spent on RCR cars across the MK1 MkV1 Susperlite and 917 I can vouch for the quality of RCRs components.

The owner/builder chooses the parts not included in the kit (drivetrain etc) and anything else that he might want at ad or upgrade. That's the beauty of building your own car

Extreme care attention to assembly tolerances, sequence of assembly and proper tightening of nuts/bolts/washers is paramount
for safe operation of any car on the road or track. And these are extreme performance cars without a doubt

A lower frequency clunking or thumping sound usually comes from heavy parts as in the drivtrain OR a suspension corner (every part may be involved from the wheel tire/axle & bearings, upright attachment points, all suspension pivotsrod ends/monballc/clevis pins, shock absorber mounting barings or bushings mounting bolts and attachment points).

Just so I don't jump to conclusions, are you hearing a sound eminating from the foot box area and simultaneously feeling the floor of the car flex under your feet or seat? Did you feel any vibration through the steering colum or wheel when the clunking is heard?

Cheers
Ian

Hi Ian,

Yes you describe what I am experiencing perfectly here: "...sound emanating from the foot box area and simultaneously feeling the floor of the car flex under your feet."

Sound is definitely not sharp -- more of a muffled "thump" as the floorboard displaces enough to be felt in your heels. It has been far too cold and rainy here in the Seattle area to get the car out but I will try to recreate it as soon as I can.

 

[Neil]

Hi Ian,

Yes you describe what I am experiencing perfectly here: "...sound emanating from the foot box area and simultaneously feeling the floor of the car flex under your feet."

Sound is definitely not sharp -- more of a muffled "thump" as the floorboard displaces enough to be felt in your heels. It has been far too cold and rainy here in the Seattle area to get the car out but I will try to recreate it as soon as I can.

"Oil canning"?

 

[Ian Clark]

Hi Pasha,

Something to consider: Suspension bind in bump causing a reaction heard and/or felt inside the foot box from a combination of ride height, tire diameter, coil over spring length creating a mechanical bind resulting in a thump. This can also involve ball joints, tie rod ends, steering rack mounts and ball pivots. inspect every part for evidence of bind.

Check the floor pan for evidence of contact with the ground, Check the alingment of the steering colum, tightness of all mounting points and fasteners. Check phasing of u-joints in the steering colum.

If there's evidence of the car bottoming out or bind in the suspension or related parts a NDI LPI (non distructive liquid pentrant inspection) should be done on all aluminum parts. You cant be too cautous.

The monocoque chassis of the RCR is mostly .185 aluminum or more thick sheet. The welds look great and the chassis has passed inspection for torsional rigidity, (in Australia maybe other countries too) so it's very robust to say the least.

Hope this helps

Cheers
Ian

 

[Jerry Irwin]

Hi Pasha,

Something to consider: Suspension bind in bump causing a reaction heard and/or felt inside the foot box from a combination of ride height, tire diameter, coil over spring length creating a mechanical bind resulting in a thump. This can also involve ball joints, tie rod ends, steering rack mounts and ball pivots. inspect every part for evidence of bind.

Check the floor pan for evidence of contact with the ground, Check the alingment of the steering colum, tightness of all mounting points and fasteners. Check phasing of u-joints in the steering colum.

If there's evidence of the car bottoming out or bind in the suspension or related parts a NDI LPI (non distructive liquid pentrant inspection) should be done on all aluminum parts. You cant be too cautous.

The monocoque chassis of the RCR is mostly .185 aluminum or more thick sheet. The welds look great and the chassis has passed inspection for torsional rigidity, (in Australia maybe other countries too) so it's very robust to say the least.

Hope this helps

Cheers
Ian

all good points raised.
I would jack the car up, remove a corner spring remove anti roll bar and then move the assembly thru its entire range. just grab hold of the knock on axle and lift by hand until touch bump stop. shpuld be free to move with no binds or squeaks. and then release and let it go down under own weight.
hope this is of use..
Jerry

 

[Douglas]

I remember years ago Maximum Motorsports caster camber plates for 99-04 Mustangs, they had a recall on the spherical bearing that the strut mounted in. Made a horrible loud hard thunk noise when going over any bump at all.

I had to replace one side twice because the replacement one they sent was bad too! Lol.

I took them apart to see if it was the spherical bearing just loose fitment in the housing or the axial play in the bearing and the outer race.

It was weird because even the very tiny amount of axial play it had was way less than most helicopters concider acceptable, but made a horrible hard thunk.

 

[Pasha Saleh]

Ok, I think I’ve figured out what’s going on but need some help on how to fix it if I’m right.

I have verified everything is tight and secure in the front end with no binding, etc.

When I jack the car up and the front wheels hang, the spring is so loose it basically falls out of the upper retainer. Probably about an inch of space or more. I’m told this means there is no “preload” and that the spring should still be securely retained even while jacked up off the ground.

I’m using QA1 shocks with the shorter coil springs to accommodate a hydraulic ram for a 2” front lift kit.

So, does that sound like what could be causing the clunking? If so, how does one correctly adjust preload without changing tie height?

 

[Jean-Marc]

You have to use Spring helper from D faulkner springs, do not forget to order them with the center ring. It will compensate the depth when the spring is completely un compressed and has almost no significant thickness and stiffened constant.

D Faulkner Springs – Order Suspension Springs Online

 

[Pasha Saleh]

Thank you, Jean-Marc. I am using the RamLiftPro front end lift kit and as a result my front spring is just 3.75" long! The rate must be right because the car handles and rides fantastic. It's just that when I jack it up, you can see in this second pic the top of the spring falls all the way out of the upper spring mount. Could that be causing the clunking I am hearing and feeling underfoot? It's hard to imagine the suspension ever unloads to the point where the spring actually gets loose like that while driving?

Is there a specific part number you recall from D faulkner? Looks like there are many different spring rates to choose from. And do you need a spring seat on both sides of each helper spring?

 

[Jean-Marc]

What you are describing is exactly what those springs are for. I put this on mine (see below). I made a modification on the center rings, I grinded the lips, because in came in contact with the center ring og the AE1 spring/shok absorber.

 

[Pasha Saleh]

Thanks again, will try this solution!