Help - can?t identify what?s scraping

[sabbot]

I?m hoping that someone might be able to help identify where a scraping noise is coming from. I realize this is a bit of an ask given the forum doesn?t support sound but here goes.
I have just got my S4 Elan back on the road after a 5 year rebuild.
I bought the car as a bunch of loosely assembled parts and have been slowly putting it back together.
It has full new spyder suspension all around including the upper control arms at the rear. All of the suspension parts are new including semi-CV joint drive shafts (one cv. One rotoflex coupling).
Every time I load the suspension on a left hand corner I hear a shush, shush, shush (scraping) sound coming from the right left corner.
So far I?ve ensured the stub axle nut is tight, as are all the other bolts. I added tape to the inside of the wheels to see if they were rubbing, as that is what it sounded like, but no damage to the tape. I did the same with the body to see if the tire was rubbing - again no issues.
Driving with my foot on the brake or handbrake slightly on doesn?t seem to make any difference. It?s definitely a rotational noise that is in sync with the road speed but but i?ve Run out of ideas on things to check.
Any suggestions would be very welcome.
Thanks

[bitsobrits]

Some ideas:

Jack up the rear with the rear wheels lifted to normal ride position. Rotate the wheels by hand to listen for scraping sounds. Possible sound sources:

Handbrake pads dragging
Regular brake pads dragging
Noisy half shaft U-joint (unlikely with new parts)
Noisy driveshat U-joint
Noisy half shaft bearing

[paddy]

... coming from the right left corner.

I assume you mean the right rear corner?

Wheel rubbing on lower wishbone bolt heads?

Tyre on spring platform?

There was also someone reporting the rear tyre rubbing on the brake line or brake hose. I don't know if this is still a possibility with the Spyder suspension.

Paddy

[sabbot]

Thanks for the suggestions Paddy.
Sorry about my earlier brain fade - I had meant to type ?right rear corner?
I checked the brake hose and it is clear of the wheel. The bottom wishbone bolts are close to the allow wheel but have plenty of clearance to the steel wheel, but I taped the inside of the alloy wheel where they would touch if they were going to and the tape is intact after running the car with the scraping
I?m wondered if the caliper could be clipping the disk/ rotor under corner loads but I can?t see any clean metal on the disk to suggest it is rubbing.
Thanks again.
Stewart

[RichC]

oversize tyres on wheelarch?

[nmauduit]

is it a continuous scrape or cyclic?

Since it happens with the wheel at full droop, you may be able to reproduce it by lifting the rear right corner and watching from underneath while you rotate the wheel by hand (look also at the u-joint of the transmission - on the 2 u-joint version one need some form of droop limitation to avoid them binding)

[10kph]

Check the run and tension of the handbrake cable.. That lead to a similar noise on mine some years ago as the rotorflex touched the cable after leaving the handbrake partially on and wrong geometry to the rear quadrant.
Tony

[JonB]

I just overhauled the back end of my car and in the process had to remove one of the brake calipers so I could refit the disk. I thought I had clearance issues between the wishbone and wheel when I heard scraping coming from it with me and two passengers in the car, but it turned out to be the rigid brake line (bundy pipe) that goes between the flexible brake hose and the caliper on the side where the noise was coming from. I found a witness mark on the wheel rim and sure enough the pipe was very close to it. I bent it back a bit and considered myself lucky that it hadn't failed while I was driving. There are pictures on my thread:

lotus-gearbox-f37/overhauling-the-back-end-t40753-75.html#p289946

YMMV of course, but I think the best thing for you to do is look for witness marks, as I think you already have done.

[Robbie693]

Just wondering, does the Elan come with the wishbone shields as fitted to the Plus 2? If it does and you have them fitted then it may be the cause - mine were rubbing on the brake disk under braking, presumably due to torsional forces...

Just a random thought.

Robbie

[sabbot]

Thanks to everybody for their suggestions. I finally found the problem/s .......now all I have to do is fix it.
First problem was that one of the ears on the tripod that locates the rear disk was slightly bent. I had 0.010? skimmed off each ear of the stub axle and that squared up the disk but didn?t solve the scrape. I then jacked up the car unevenly to put the left hand spring under more tension and managed to recreate the scrape. It turns out that one of the coils the 2.5? diameter springs that come with the spyder RSC system was just touching the edge of the brake disk under cornering compression. The disks are new so quite ?fat?. The crude solution would be to grind a ~0.050? bevel on the edge of the disk but I hope that there is a better solution. Another option might be to add a small spacer to the sit between the inside edge of the stub axle and the inner wheel bearing to space the stub axle and disk slightly inboard and the disk away from the spring, this would also result in the whole wheel and disk moving inboard ever so slightly. I have the clearance in the caliper to move everything at least 0.1? inboard. I?m wondering if anybody else has this problem?
Now that I know what?s wrong i?m also going to give Spyder a call to see if they have ang bright ideas.

[rgh0]

The spyder rear spring design is unstable and tends to buckle under load. Fitting a plastic or rubber shield inside the spring on the shock will reduce the buckling and may give you the clearance you need.

cheers
Rohan

[david.g.chapman]

I had a similar problem on the front springs of my +2 and used large nylon cable ties on the springs to help centre them. I don't know what clearance you have between the spring coils and the shock body though, if it's too great this won't work.

Rohan's sleeving idea is the best but you will have to take the springs off first I suppose.

Dave Chapman.

[sabbot]

I called Spyder to ask about the spring issue and their suggestion was to try rotating the spring by 1/4 to 1/2 a turn. I did this and although I haven?t had it out on the road it?s possible that it has helped. The pictures indicate a little more clearance but I still think that under certain loads a spring coil will hit the disk and therefore I?m intending to machine the disk slightly for added clearance and will let you know the results.

[sabbot]

I called Spyder to ask about the spring issue and their suggestion was to try rotating the spring by 1/4 to 1/2 a turn. I did this and although I haven?t had it out on the road it?s possible that it has helped. The pictures indicate a little more clearance but I still think that under certain loads a spring coil will hit the disk and therefore I?m intending to machine the disk slightly for added clearance and will let you know the results.

[rgh0]

The spring will tend to always buckle in the same direction so rotating the spring will help to set the buckle direction away from the disk

cheers
Rohan