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Brake Rotors

bernd_st

Bronze Level Sponsor
Speedy Spares in UK used to carry them, however don't find them listed on their Homepage at the moment. Perhaps you can send them an Email enquiry.
 

DanR

Diamond Level Sponsor
I am not as familiar with the early Series as the later, is the only difference between the early and late rotors the OD?
 

jumpinjan

Bronze Level Sponsor
Early vs. Later rotors: I'm pretty sure the rotor disk is the same for both, the hubs are different.
Jan
 

DanR

Diamond Level Sponsor
Thanks JAn.

Next question: what is the difference in bolt pattern if any?

I thought they were the same.

I guess I need to revert to the parts manual
 

Barry

Diamond Level Sponsor
I am not as familiar with the early Series as the later, is the only difference between the early and late rotors the OD?



That question has been asked on multiple occasions, but has never been conclusively answered.

The rotor O.D. is clearly different; 9.5" for the early Series Alpines versus 9.85" for the late Series Alpines. What has not been conclusively addressed is rotor face I.D., mounting flange offset, diameter of the centering hole, mounting flange thickness and the mounting bolt hole pattern.

Rootes drawings would be conclusive as would precise comparative measurements of known "original" rotors.
 
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bernd_st

Bronze Level Sponsor
Last statement appears correct. I haven't found any other difference than the OD ( early 240mm, vs late 250mm ) on the repros which I have. Comparison with some NOS ones brings the same result. On my S2 I found very thin ones but would attribute that to wear. Anyhow that means late ones could be turned down on a lathe to make them fit for early series ;)

IMG_20220717_161809.jpg

P.S. Top one is for early Series...
 

Barry

Diamond Level Sponsor
Last statement appears correct. I haven't found any other difference than the OD ( early 240mm, vs late 250mm ) on the repros which I have. Comparison with some NOS ones brings the same result. On my S2 I found very thin ones but would attribute that to wear. Anyhow that means late ones could be turned down on a lathe to make them fit for early series ;)

View attachment 26638

P.S. Top one is for early Series...



Conclusive enough for me, thanks!
 

DanR

Diamond Level Sponsor
If that be the case I have several used but very good SV rotors that could have the OD turned down for the SI-II's
 

jmahall

Silver Level Sponsor
Thanks for the reply, Dan. I'm trying to work out an issue with a pulsating pedal. At low speed I can feel the brake releasing and engaging. Under heavy braking it shakes like the dickens. Symptoms of warped disks. New master, rebuilt with new pucks, calipers, freshly turned rotors, .005 runout on left, .003 on right, new pads. Swapped out wheels with another set. Running out of ideas.

Keep out a nice pair and I'll get back to you soon.

Thanks

Jack
 

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jmahall

Silver Level Sponsor
I agree with symptoms but not with data. .005 runout on left / .45" thickness, .003 on right / .425" thickness.
 

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Toyanvil

Gold Level Sponsor
I would check the thickness at 12:00, 3:00, 6:00 and 9:00. It looks okay in the picture, but is the caliper centered on the rotor. I always turn my rotors on a lathe to keep both sides parallel.
rotor-XL.jpg
 

jmahall

Silver Level Sponsor
Yes, it is. If the thickness wasn't equal it would show up on the runout data. I don't have access to a lathe big enough to do that. They were just turned at my local tire shop and I have no reason to distrust them.

Another thought, as the caliper is supplied with pressure from both sides, what if one side wasn't getting pressure from a blockage. Tomorrow I'm going to see what I do about checking that.
 

DanR

Diamond Level Sponsor
There are a number of small passages in the calipers that require special attention.

Even though the WSM says "not to split" the caliper unless a professional does it, I have rebuilt several with excellent results.
 

husky drvr

Platinum Level Sponsor
I thought they were the same.

I guess I need to revert to the parts manual

Dan,

By the parts manual, the front bolt on wheel hubs have three part numbers. The first two numbers being superseded by the third some time during series I, II, 3 production. That third number is carried on till the end of production.

That should indicate that any Alpine bolt on front wheel hub should be functionally interchangeable - early to late series.

Hope this helps,
 

bernd_st

Bronze Level Sponsor
I agree with symptoms but not with data. .005 runout on left / .45" thickness, .003 on right / .425" thickness.
Perhaps it's just the picture, but your lower wheel stud looks out of true. Would also carefully inspect the hub whether it's rotating evenly, especially the surface where the rotor is attached to. Are the wheel bearings Ok and properly adjusted ? Wheel studs firm in the bore and true ?
 

DanR

Diamond Level Sponsor
Sunbeam Specialties and Classic Sunbeam sells the little rubber o-ring that goes between the halves.

Note also the WSM has two different specs for tightening the halves.
 
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