Lotus Europa Community
Lotus Europa Forums => Garage => Topic started by: jbcollier on Friday,September 21, 2018, 02:51:18 PM
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One of the first production line changes that Lotus made while making the Europa was to switch to balanced brake drums. The following shows you why.
Use a simple static wheel balancer available inexpensively from Harbor Frieght, Princess Auto, Machine Mart and others:
https://jbcollier.smugmug.com/Lotus-Europa/i-bBZ6PM8/A
You will have to cut the four springs down so the spring tension is lower and allows the drum to rest onto the tapered cone. (the drum is upside down so the spring loaded guide can work on a machined surface)
So how far out is a brand new drum:
https://jbcollier.smugmug.com/Lotus-Europa/i-rrwXXvT/A
Quite a bit. (choose a larger size to see the bubble)
This is better:
https://jbcollier.smugmug.com/Lotus-Europa/i-ssRg4Sk/A
How much weight did I take off (make sure you are sitting down before clicking on the link):
https://jbcollier.smugmug.com/Lotus-Europa/i-rb3MLgd/A
Holy Poop!
(the second drum needed less material removed)
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That was surprising! That was a lot! Did you drive it before balancing that drum? Did it make a difference in the car?
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Been having troubles with rear wheel balance at speed. First set of drums I spun on live centres but it was hard to have the centres tight enough so I thought I would try this next. Will report back later.
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Stupid question maybe, but is it possible to spin balance the drums and weld on permanent weights rather than removing the material?
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It's not stupid. I have seen weights attached to brake drums in the past. I don't know how they were attached though.
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Not stupid at all. Didn’t have access to a spin balancer that would work with such a small piece.
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...is it possible to spin balance the drums and weld on permanent weights rather than removing the material?
:huh: This is a LOTUS !! ....Colin Chapman says weight must be REDUCED, not added. :FUNNY:
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When I started to get wheels balanced back in the day, I remember on-car balancers. The wheel was spun up on the car with a balancer attached. I don't remember if that was done on the rears but it was done on the front wheels. I can't see it working on the back wheels but did it?
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Went for a long drive today and the car has been transformed. The vibration is virtually completely gone. It would be all gone but for one slightly out-of-round rear tire. Amazing. Highly recommend balancing your brake drums. The amount of weight required could never be added to a wheel. You saw the photos, it was huge.
I have an on-car spin balancer and you can do the rear but you have to spin it up with the engine rather than the tire spinner.
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JB, did you slowly grind the excess material off and then constantly checking if you did enough or did you use a band saw?
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That's great, JB! :pirate:
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Slowly ground away, checking as I went. Just used an ordinary bench grinder.
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Excellent outcome. I need to do this on my Healey and Warwick cars. The front rotors on my Lotus were machined off center - both of them. It took 3/4 of an ounce to get it close. It wasn't practical to adjust the balance so I tossed them and bought a higher quality new set. I wish I had thought about the impact of off balance rotors as I spent countless hours changing wheels, tires and going back and forth to balance shops.
Transformed the driving experience.
Dean
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This thread from last September left an impression on me. Like JB, I've had a rear-end imbalance, mine at speeds above about 50 mph, sometimes there, sometimes not, feeling generally harmonic. Wheel balancing did not cure the problem. With my S2 still in its seasonal layup, I decided to have its drums dynamically balanced. I know these are the original drums for the car because I'm the only DPO.
I took the drums to an engineering shop and got a phone call a few days later. They'd balanced one but the other, they said, was oval and they didn't want to do it.
I took back the oval drum and remounted it to the hub. Sure enough, once I knew what to look for I could see it ran out-of-round. I can't measure runout precisely but it totals about 1.6 mm. I ordered a new drum from RD.
The one old drum was balanced by adding weight in two spots. The new drum was balanced by lightly grinding two spots.
I measured the distance from the lip of each bolt hole to the edge of the centre hole on the oval wheel. My four readings were (mm): 9.87, 10.07, 10.15, 9.98. Hmm. I similarly measured the new drum: 10.02, 10.02, 9.98, 10.07, which probably says something about my technique but indicates where the problem might have come from. Once the car is back on the road I'll report whether this work had any real effect.
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John,
I have a BJ8 Healey and it is known for the rear drums being out of balance. I took them to a speed shop and they ground down the outer lip, AND drilled shallow holes on the outside to get one balanced. The other had only minor corrections.
But I've wondered about the integrity of the drums with the outer lip ground off. Isn't that lip there to keep the drum from cracking due to brake shoe pressure? So far my Healey has been okay, no issues, and my TCS has discs, so no worries there. If you track the car, I would be very concerned.
Jerry Rude
4005R
Oh, BTW, I did eventually buy an on the car balancer off ebay just to keep the front tires in balance on the TCS. I think the brand is Hunter. I could never get the tires balanced fine enough from a tire shop, even with the conical inserts in the Lotus alloys.
jr
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I can report that balancing the drums was a good thing to do, in my case. Vibration gone.
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Good question Jerry. I have seen drums without the lip. I would be concerned if they were front brake drums as uneven heat loading could cause cracking. Not really with the rear brakes though as they don't really do much compared to the fronts.