Lotus Elan

Warped rotors/hubs

PostPost by: benymazz » Sat May 02, 2020 2:29 am

So over the course of rebuilding my front suspension during the past week, some things have arisen. On a hunch, I checked the runout of my front brake discs. 6 thou of runout on the left, 2.5 thou on the right. And yes, before measuring I took all of the lash out of the front wheel bearings to ensure that they didn't interfere with the measurement. My workshop manual says that up to .004" of runout is acceptable.

These rotors are EBC rotors that are a year old and have under 4,000 miles on them. Those 4,000 miles have been relatively tame - a little bit of spirited driving, but not for extended periods of time, and nowhere near as spirited as a track day would be. It's possible these rotors were "warped" out of the box. The only thing that made me check is that recently I switched to the Carbone-Lorraine RC6 pads and, being horribly squealy, when I got up to speed I was getting a "chirping" once per revolution of the wheel as the pad made contact with the high spot on the rotor. I also had a very slight brake pedal vibration when braking above 70mph, but it was barely perceptible and went away once I was below 70mph.

I saw something else that concerned me. On the faces of my hubs there are indentations where the wheel sits (I have bolt on hubs). I measured these with my dial indicator and they vary from 5 to 7 thou below the rest of the hub. You can definitely feel them when you run your finger across the hub surface. I attached a picture below, the area that's depressed is inside the red dashed line (the area immediately around the stud is not depressed). I assume this was caused by extreme overtorquing of the lug nuts at some point in the past, or do these hubs just go "soft" over time? The back hubs had this indentation pattern before I replaced them a couple of months ago. I assume they are the original hubs that came with the car which would put their total mileage at 135,000.

Also, my brake caliper is uncomfortably close to the rotor, but I guess that's just how it is normally? I can't see any way it sits farther away from the rotor.

So I guess my questions are: Has anyone else had a bad experience with EBC discs? Could the hubs be warped and causing disc runout? Has anyone else seen wheel indentations on their hubs? Is my caliper sitting that close to the disc normal or did I do something wrong?

I will try to do some more diagnostics this weekend to narrow down where the runout is coming from. Mixed feelings... I would like to believe that my virtually new rotors are not warped, but I also don't want my hubs to be warped as that's gonna be a PITA to fix. Maybe they could be re-trued on a lathe, but I have a feeling those indentations on the face are a problem which would involve driving the wheel studs out to resurface... more work involving tools I don't have... I also can't readily locate anyone that has replacement front bolt-on hubs (plenty of KO ones though)...

-Ben

PS if anyone knows how to make the Carbone Lorraine sintered (RC6) pads stop squealing, please share your secret... I love them, the brake pedal feels amazing with them, but my god they're so loud...
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IMG_1737.jpg and
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PostPost by: StressCraxx » Sat May 02, 2020 4:38 am

Benny,

Good for you on checking the runout. There appears to be quite a bit of swarf on your hubs where your wheels mate up.

I learned from the machinery millwrights I work with to carefully prepare mating surfaces before assembly. May I suggest carefully cleaning your hubs and rotor mating faces with an oil stone. Clean any residue remaining. Reassemble and check your runout again. If that doesn't work try clocking the rotor on the hub in a different position.
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PostPost by: wotsisname » Sat May 02, 2020 7:37 am

Re the squealing. I have pagids on an Elise that squeal quite a lot and seem to be prone to creating quite a bit of dust. I use a smear of ceratec on the back of the pads, which works very well in that case. It is significantly less prone to melting than copperslip. It will be cleaned off if you use a brake cleaner aerosol.
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PostPost by: HCA » Sat May 02, 2020 9:07 am

One better than ceratec imo is Liqui Moly Brake Paste 3077 - made by same people as Ceratec, but it is a bit thicker. Comes in a small tin with a brush. Make sure the stuff is brushed into all the parts of the caliper and pistons that the pad back plate touches or slides on.

https://www.amazon.co.uk/Liqui-Moly-Bra ... B00295D9VQ

Copper grease is useless.

Brake squeel is nothing more than the noise produced by high frequency vibrations of the pad in the caliper, so these need to be dampened.
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PostPost by: oldelanman » Sat May 02, 2020 10:14 am

Do you have the anti rattle/squeal shims in place ?
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PostPost by: benymazz » Sat May 02, 2020 2:58 pm

StressCraxx wrote:Benny,

Good for you on checking the runout. There appears to be quite a bit of swarf on your hubs where your wheels mate up.

I learned from the machinery millwrights I work with to carefully prepare mating surfaces before assembly. May I suggest carefully cleaning your hubs and rotor mating faces with an oil stone. Clean any residue remaining. Reassemble and check your runout again. If that doesn't work try clocking the rotor on the hub in a different position.


I learned this as well from spending enough time working in automotive shops. Up here in the rust belt it's common to see cars just a few years old come in for brake jobs where the brake disc has rusted itself to the hub and has to be beaten off with a sledgehammer. After the disc is removed, the face of the hub is cleaned up with a Roloc disc on a die grinder to get the rust off, and then cleaned with brake cleaner, and then the new rotor is put on. The rust is bad enough that 95% of the time the rotors and pads are done at the same time instead of just pads.

The "swarf" inside the pockets of the hubs is a mixture of brake dust and grease.

I had the same idea as you as I was going to sleep last night about clocking the rotor into a different position on the hub so that's what I did first thing this morning. While re-clocking I did as you suggested and took an oil stone to the face of the hub and disc where they mate together. There was no corrosion or anything that appeared to indicate a high spot. And... the runout stayed in the same position on the hub, not the disc. So I guess I've got at least one bad hub on my hands. Nuts...

As for the brake squeal - when doing brake jobs on any vehicle usually I use Permatex Ceramic Brake Parts Lubricant. When I changed to the CL pads though I didn't have it on hand so what was there was just what was left on the shim and piston from the time before which wasn't much. When assembling this time around I put a coating on all surfaces (back of pad, both sides of the shim, face of the piston). We'll see how it works, I might get out for a drive tomorrow.

oldelanman wrote:Do you have the anti rattle/squeal shims in place ?


Yes, the shims are in place and in the correct orientation.
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PostPost by: alan.barker » Sat May 02, 2020 4:05 pm

I would check to see if Discs are seated correctly on Hubs with no burrs. If they still run out get the assembly skimmed on Lathe.
Check rear Disc run out also as many get damaged when rear Wheel Bearings are changed. :shock:
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PostPost by: miked » Sat May 02, 2020 8:38 pm

I have 4 pot calipers on an elan with bigger discs. These had run out but were NOS that came with the car. I bought a new set from the same supplier from were the original came. These too were out. I ended up with one of the NOS ones with one of the new ones. Drove myself nuts cleaning and clocking the hubs. Even tried a fresh hub on one side. How disappointing. Literally had a wave. High point on one side had a low point on the opposite side. 2 to 3 thou one disc and about 4 on the other. Can feel it under the pedal when slowing to about 10mph under a light pedal :cry: :evil:
Supplier was Rally Design. The centres weren't even right. I had to have them turned out. My lathe was not big enough. Cost me. When they checked their stock,
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PostPost by: vstibbard » Sun May 03, 2020 7:52 am

New bolt on hubs are available, alloy are most common, and suppliers will fit new wheel studs etc. Iv'e purchased from Merlin Motorsport previously, the supply hub only, hub and studs including fitting, and if yo want them to they will fit bearings as well.

You may find a Triumph spares provider can supply the original iron hubs as they are off the 4 cyclones MkI or II Herald/Spitfire series of cars.

I have no commercial relationship with Merlin Motorsport.

Cheers

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PostPost by: 2cams70 » Sun May 03, 2020 12:18 pm

Warped rotors were something virtually unheard of back in the bad old days of asbestos brake pads. I remember when I first tried a set of newly introduced Bendix asbestos free pads in the grocery getter Ford Falcon back in the late '90's and sure enough after around 10,000kms it had badly warped discs. When I took the pads back to complain the guy behind the counter smiled and said "I know nothing". The next time around Bendix were now calling their asbestos free pads by another marketing name and they had obviously learnt and changed their formulation as these pads were less prone to the problem.
My current late model Honda City grocery getter also suffered from the same problem. I took it down a long fast mountain run one day during which the brakes became very hot and were smoking at the end of it. After they cooled down sure enough there was a brake shudder which persisted until recently when the pads were changed and the discs machined.
Conclusion - something in the brake pad formulation can cause warped brake discs. I'm not a brake expert and don't know exactly why or how but there's definitely a connection between the type of pads used and brake disc warpage. If someone can explain the reasons I'd be very interested to hear them.
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PostPost by: benymazz » Thu May 07, 2020 3:51 pm

Status update. I went for a test drive last night and the brake squeal has gone away - appears that the application of Permatex Ceramic brake parts grease took care of that. I still have a slight squeal just before I come to a stop but it's much much better than it was before.

Just to clarify - the discs themselves have under .001" runout in them. The problem I'm having is that the face of the hub where the disc sits is not orthogonal to the axis of rotation, which is manifesting itself in the form of runout at the disc.

As for the hubs, I looked around and I can't find anyone that has steel/iron ones for sale new. I found a used one on eBay from a GT6 that appears to be a correct replacement but I'm not positive - can anyone spot check me on this? https://www.ebay.com/itm/Triumph-GT6-Fr ... 3086646243

It was recommended to me that I knock the studs out of the current hub I own and machine it true on both faces but I'm still figuring out how I would mount it up in the chuck and get it dialed in. I'll probably be able to figure it out, but if anyone else has done this before, what was your procedure?

-Ben
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PostPost by: rgh0 » Fri May 08, 2020 3:44 am

You need to find a way to mount it in the lathe using the bearing mount surfaces so you machine the faces at 90 degrees to the bearing axis

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PostPost by: h20hamelan » Fri May 08, 2020 2:31 pm

Many times, I run a flap wheel over both sides of the rotor. And this works.
When you heat up a rotor, and apply the brakes. Debris remains on the rotor surface in that spot. The next time you apply the brakes, the high spot collects more dust/debris. This remains super heated to the rotor surface.

If you end up with wobble pattern, or cross drilled rotors. You are instructed to clean passages.
I have found that this is not 100%, but worth a shot.

I sort of think more has to do with the quality of metal. German built or if there are UK manufacturing. I suspect how metal is recycled these days is the reason they will likely continue warp.
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PostPost by: Andy8421 » Sat May 09, 2020 7:24 am

rgh0 wrote:You need to find a way to mount it in the lathe using the bearing mount surfaces so you machine the faces at 90 degrees to the bearing axis

cheers
Rohan

As is always the case, it would be much easier to do the other way - mount using the face, then machine the bearing surfaces - but that isn't going to help.

I did this a long time ago, and if I recall correctly used a 4 jaw chuck on the outside of the narrow end of the hub, then a DTI on the inner and outer bearing surfaces to get it true. The inner bearing surface is tough to reach, but at the time I had a DTI with a crank in the shaft that allowed me to reach into the hub.

Alternatively, you could machine between centres, keeping the bearings in the hub and machine up a dummy stub axle or use an old one to keep the bearings tight. You would need to drive the hub, but I have seen a hose clamp used in place of a lathe dog which you could place around the narrow end of the hub and pick up with a bolt mounted on a faceplate.
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PostPost by: Donels » Sat May 09, 2020 5:25 pm

Try Canley Classic Triumph parts. They supply all Triumph parts if you want new. Just checked and they’re out of stock but available to order at £37.50.
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