Mains bearings, to superblend or not?

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Champy72

Champy72

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I have superblend bearings in my racing Commando 750, and will renew/replace these during a winter refurb. I have read an article stating that the original superblends were better than the modern versions are nowadays, and also I have a note that the SKF 21306 bearings are better.

Anyone have any recommendations?
 
If you go to a bearing suppler and ask for superblend bearing they wonder what you are saying as they only go by the letters and numbers, I have ordered the main bearing from SKF and the roller bearing came with plastic cage, I ran them for some time without problems but when I had to replace my crank cases I replace the main bearings and paid the extra money going through my British bike shop, the bearings I got from SKF was 1/4 the price of the superblends from the bike shop.

Ashley
 
ashman said:
If you go to a bearing suppler and ask for superblend bearing they wonder what you are saying as they only go by the letters and numbers, I have ordered the main bearing from SKF and the roller bearing came with plastic cage, I ran them for some time without problems but when I had to replace my crank cases I replace the main bearings and paid the extra money going through my British bike shop, the bearings I got from SKF was 1/4 the price of the superblends from the bike shop.

Ashley
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Thanks Ashley. These bearings are certainly not cheap here at £48 each!
I'll get prices on the SKF, although I'd probably prefer brass cages rather than plastic ones.
 
Bearings with plastic cages are not suitable for automotive purposes imo.
 
Peter R said:
Bearings with plastic cages are not suitable for automotive purposes imo.
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I do agree with this statement but when I was younger and more stupid than I am now!!!
I rebuilt my BSA A10 with a drive side main bearing with a poly cage
A mate of mine sourced the bearings for me for the whole bike foc
I have overhead this bike a couple of times
One time I melted the HT leads to the cylinder head inlet manifold the motor was so hot
The bearings are still in there I still have the bike and the bearings have been fine for nearly 40 years now
If I ever pull the bottom end apart I'll change it to a steel caged bearing for sure
 
Champy72 said:
I have superblend bearings in my racing Commando 750, and will renew/replace these during a winter refurb. I have read an article stating that the original superblends were better than the modern versions are nowadays, and also I have a note that the SKF 21306 bearings are better.

Anyone have any recommendations?
Click to expand...
Do your bearings actually need changing? Or just precaution?
I never change bearings unless necessary
 
KTM used a NJ306 main that has the poly cage and I have also used them when I found them on ebay at a good price with no issues.
 
I bought my bearings from a highly regarded bearing supplier here in the states. The sales rep knew exactly what I wanted and sold me what he thought was the most reliable and suitable parts available at the time. I know I paid over $120 US for the pair and that was in 2009. I figured I didn't want to ever do it again.
 
baz said:
Do your bearings actually need changing? Or just precaution?
I never change bearings unless necessary
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As it is a racing machine and under loads of stress, I strip the engine each winter and replace the big end shells, Rings (only if necessary), oil and if the main bearings are 2-3 years old, those too. Fortunately, not had any issues with the crank or Thunder Rod con rods, or the Omega pistons. Yes, it may be totally unnecessary, but if they go at an overseas meeting, the lost money is horrendous!
 
Hi Ian
Martin? He of Kay MV fame used to work for a bearing company. He said all rollers have barrel rollers (nice big word here) romboidy & that standard (new) bearings are of far better quality & design than original superblends & he would not be concerned about using them.
Speak to an automotive bearing company.
When superblends were in short supply a well known company asked me for £86 each. I was given a set in polymer cages for £12 each form a Norton man in the New Forest. 26 years ago still about!
Hopefully see you next year.
Interesting 5 speed box by the way.
 
Hey Chris. At last someone who talks sense! I'll scull around as I have lots of time on this one...
Cheers
 
Hmm. I always worry about the word 'Budget' in front of anything, like Hotel, tools and bearings! They are a very low price, and if you place 'FAG' in front of the number, no bearings can be found.
Appreciate your tip on this, but I'll probably stick to known manufacturers.
 
Why do you say you don’t need C3?

I thought that’s what a Commando DOES need as it give more clearance, which is needed where the bearing outer is a tight fit in the cases?

And I also thought this issue was even more important on a racer where you’re likely to have more crank flex than most road bikes and where less drag is desirable?

Whilst a bearing supplier should (hopefully) be an expert in bearings, how can they be experts in all applications, specifically racing vintage Norton engines??

This is why, personally, with something like this, I’d say buy from Norman, Mick or Steve after discussing your application in detail. These guys DO understand racing Norton engines and have fitted more bearings than we’ve had hot dinners!

Yes, you will probably pay a few quid more than you will from an industrial wholesaler... but is that few quid really a wise saving ?
 
Fast Eddie said:
Why do you say you don’t need C3?

I thought that’s what a Commando DOES need as it give more clearance, which is needed where the bearing outer is a tight fit in the cases?

And I also thought this issue was even more important on a racer where you’re likely to have more crank flex than most road bikes and where less drag is desirable?

Whilst a bearing supplier should (hopefully) be an expert in bearings, how can they be experts in all applications, specifically racing vintage Norton engines??

This is why, personally, with something like this, I’d say buy from Norman, Mick or Steve after discussing your application in detail. These guys DO understand racing Norton engines and have fitted more bearings than we’ve had hot dinners!

Yes, you will probably pay a few quid more than you will from an industrial wholesaler... but is that few quid really a wise saving ?
Click to expand...
Ooops. C3 was a mis-type, I meant C4 (as these were listed on Simply Bearings site). Yes, I will be going for C3 FAG bearings from RGM, which I am sure I used last time. I really have gone off the idea of buying from anyone 'not' Norton au fait, especially having read the detailed report sent by DevonNorton this morning.
 
Hello All
For info, this table is my attempt summarising info on main bearings:

Mains bearings, to superblend or not?


Link to the detailed document on the NOC (UK) website https://www.nortonownersclub.org/sites/default/files/Main-Bearings-v1.1.compressed.pdf
(This document is the report referred to by Champy72)
I had a lot of help producing this including from Jim Comstock, Anthony Curzon (NOC), L.A.B. and others on this forum and fellow NOC members.

L.A.B. has kindly added links in Technical Information.

Andy
 
Champy72 said:
Ooops. C3 was a mis-type, I meant C4 (as these were listed on Simply Bearings site). Yes, I will be going for C3 FAG bearings from RGM, which I am sure I used last time. I really have gone off the idea of buying from anyone 'not' Norton au fait, especially having read the detailed report sent by DevonNorton this morning.
Click to expand...

I‘m with you on that conclusion !

Also, I used bearing from RGM in my 850 and they e been perfect. Not a race bike, although it’s done many track day events.
 
Fast Eddie said:
Why do you say you don’t need C3?

I thought that’s what a Commando DOES need as it give more clearance, which is needed where the bearing outer is a tight fit in the cases?

And I also thought this issue was even more important on a racer where you’re likely to have more crank flex than most road bikes and where less drag is desirable?

Whilst a bearing supplier should (hopefully) be an expert in bearings, how can they be experts in all applications, specifically racing vintage Norton engines??

This is why, personally, with something like this, I’d say buy from Norman, Mick or Steve after discussing your application in detail. These guys DO understand racing Norton engines and have fitted more bearings than we’ve had hot dinners!

Yes, you will probably pay a few quid more than you will from an industrial wholesaler... but is that few quid really a wise saving ?
Click to expand...


The inference on the RGM site is that you might want to use standard bearing clearance when the cases have opened up a little after use and don't clamp the bearings as tightly!

This suggests that in a very tight clearance set of cases (Maney with little use perhaps?) you will get less free play than is recommended! As you say.

You might also want to consider the impact of flexing based on crank choice and useage. There are those who think a Norton crank will flex more in an 850 ridden habitually at 3500 to 4500rpm right in the max torque range than a short stroke Maney crank used in a 750 race bike, habitually used at 6000 to 7500.

Either way, C3s as supplied by both AN and RGM for me!

Won't be much in it, but considering postage to France, for me AN may come out comparatively closer on price than for you guys in the UK due to RGM's standard shipping charge!
 
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