Are my Middleburn RS2s knackered?

[provdes]

I did think metal fatigue on the threads would be the culprit. The rest of the cranks are mint, so I think I may get all four holes helicoiled and get some new bolts.

Do kind of wish I had never removed the spider, but it needed a clean and I wanted to make sure the bolts were ok (kind of glad I checked). Plus the anodising is a little worn on my spider so was on the look out for a fresher one. @Once A Hero what colour and BCD is the spider you have?

Think I may start a build thread for this bike as what started out a quick n dirty pub bike build, is now becoming something I'd never want to leave outside for very long!

 

[Once A Hero]

@provdes I think the spider on my cranks are standard 110/74 bcd, and it's silver.
However my cranks are RS-3 - so I don't think the spider is compatible with an RS-2 arm.

 

[provdes]

@Once A Hero Oh, I read that they were interchangeable on another thread somewhere. It was RS-1 to RS-2 that didn't work.

This is my drive side arm... I was sold them as RS-2s. Can anyone confirm that is what they are? (I also read on another thread that RS-2s were flat... along with the Earth)

 

[wadsy]

Look up timesert; better than helicoil.

 

[27motorhead]

@Once A Hero Oh, I read that they were interchangeable on another thread somewhere. It was RS-1 to RS-2 that didn't work.

This is my drive side arm... I was sold them as RS-2s. Can anyone confirm that is what they are? (I also read on another thread that RS-2s were flat... along with the Earth)

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Those look like RS3's to me. I had these back in the 90s. Happy to be proven wrong though!

 

[Once A Hero]

Yep those are RS-3

1996 Middleburn Catalogue

1996 Middleburn Catalogue

www.retrobike.co.uk

 

[provdes]

Ahhh! I did wonder. Thank you @Once A Hero so much for posting the link to that catalogue, it's amazing!

RS-3s they are indeed.

Looking at the position of the bolt holes I think I'll only be able to tap the two nearest the crank arm as there isn't enough material around the others. That may be enough though!

 

[provdes]

I have repaired my RS-3s!

Thought I'd post a quick update.

I got a helicoil kit off Amazon for £17 and bought some fresh stainless M3x10 bolts (but with a torx head for more secure tool fitting).

I was going to get an engineering mate to drill out the holes with his proper pillar drill, but I got the flu, then got bored so did it home with a regular drill.


Drilled out the holes. Very easy to do with a steady hand.


Tapped a new thread


Screwed in the coil (with some threadlock on it)


Punched out the helicoil tab


Good to go!


Installed new bolts!


It wasn't all plain sailing to be honest. I drilled the holes as deep as I would dare but noticed there was a small pilot hole that went deeper. So when I punched the tab out of the coil, I think it fell into the pilot hole and got jammed in there by the punch, as I couldn't get out of the hole. This meant when I installed the first bolt it got jammed half way in and the bolt head snapped off. I had to get the bolt stud back out and then cut the bolts shorter (to about 7mm) so they didn't get caught up on whatever was in the bottom of the holes. The coils were only about 5mm deep so there is still plenty of thread doing the work, and they tightened up beautifully.