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Brakes Drums


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#1 RogerH

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Posted 09 June 2018 - 08:49 AM

Hi Folks,

             last week I fitted new rear brake drums to the 4A and noticed when adjusting the nearside drum that there was a high spot - drum binding at one point.

 

On my tour of the Yorkshire dales I noticed that when the brakes were applied there was a pulsing from the nearside rear.

This calmed down a little during the week.

 

Yesterday I took it apart and found one of the small CS screws that hold the drum in place had its head almost sheared off !!

 

On the lathe - using the large centre hole to hold it in the chuck - I found that the brake surface was a good 0.016" out of round/offset.

 

 

The old Alfins I took off were a lot better at apprx 0.004" off.

 

Should I expect the drum centre hole to be concentric with the brake surface?

 

Roger 


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never surrender, never give up and always balance your butterflies

Veni Vidi Flati
TR4A - July 1967 daily driver         2010 RBRR No.22  2014 RBRR No.69
TR4 - March 1962 transforming like the proverbial caterpillar - it's now Royal Blue and now with the chromy bits.
 
 
 
 
 

#2 Lebro

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Posted 09 June 2018 - 08:57 AM

I guess it's more important that the drum is concentric with the center of the array of the 4 stud holes (& the csk holes of course).

 

Can you check that on your lathe, maybe using a 4 jaw chuck & 4 close fitting bolts ?

 

Bob


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#3 John Bracher

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Posted 09 June 2018 - 10:03 AM

Roger

Could you mount the drum 'inside out' on an (old) rear hub??

I skimmed some old  'worn tapered' and eccentric drums down back in the day using this method.

 

John


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#4 DaveN

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Posted 09 June 2018 - 01:36 PM

More sh1t ‘quality’ parts Roger?

 
Should I expect the drum centre hole to be concentric with the brake surface?
 
Roger


Um.......yep!

What are you going to do, skim the brake surface or return for a new set?
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#5 RogerH

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Posted 09 June 2018 - 01:40 PM

Hi Dave,

            picked up a replacement this morning and it is significantly rounder.

I will get the other one reground by a local shop.

 

Roger


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Time is a drug - Too much will kill you
Forgive your enemy, but remember the ass-hole's name.
never surrender, never give up and always balance your butterflies

Veni Vidi Flati
TR4A - July 1967 daily driver         2010 RBRR No.22  2014 RBRR No.69
TR4 - March 1962 transforming like the proverbial caterpillar - it's now Royal Blue and now with the chromy bits.
 
 
 
 
 

#6 Willie

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Posted 09 June 2018 - 07:01 PM

As far as the retaining screws in the drums are concerned, I fitted countersunk hexagonal headed [allen screw] stainless units to mine in 2014. No more splayed screws! Size required is 1/4 UNF x 3/8". I cut down 1" units to fit.  I installed new drums in my TR4 last November. Only about £30 each inc postage. Is that comparable to engineered costs?

 

Whilst on drum subject, note TR4 studs are screw-in with protruding shoulder, so stud holes in the standard one-size-fits-all drums need opening to 15mm to abut properly against the drum.  

 

Best wishes    Wiillie.


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