Freewheel shim/spacer?

[Alan O]

I have an old-style screw-on 6-speed freewheel/block, 14-24 teeth, on my 80s steel Orbit Gold Medal.

I rebuilt the bike recently, but now I can't get the rear derailleur to engage the 24 tooth sprocket. The derailleur is a SunTour Vx shorter cage model, but I had the same problem with the derailleur that I replaced with it - that one was a Shimano of some sort, can't remember now.

The derailleur is fully screwed in to the mount on the dropout.

As it is a problem with both derailleurs and the Shimano one was the original that used to work fine, I'm guessing it's something to do with my new wheels and the position of the freewheel thereupon.

It's not the limit screw, as I can unscrew it all the way out (literally out) and it makes no difference. The other limit screw has plenty of spare tolerance, so I can put the derailleur noticeably further out than the 14 tooth sprocket.

In short, it looks like it would be fine if I could move the whole freewheel block out from the hub by about 3mm, so I'm assuming a shim or spacer between the freewheel and hub is what I need - and I see such things do exist.

But before I buy one, I thought I'd check with you knowledgeable folks in case anyone can think of anything else that might be causing it?

 

[I like Skol]

Axle spacing. I guess the axle has been out at some point and not put back together correctly.

I assume a bike this age will have horizontal rear drop-outs, how central is the wheel at the seat stays? If it is closer to the left than the right then I would swap some of the axle washers from the drive side to the other.

 

[Alan O]

Axle spacing. I guess the axle has been out at some point and not put back together correctly.

I assume a bike this age will have horizontal rear drop-outs, how central is the wheel at the seat stays? If it is closer to the left than the right then I would swap some of the axle washers from the drive side to the other.

Yep, horizontal dropouts.

The wheels are new, which doesn't necessarily mean they were built correctly. But I don't see any spacing problems, and the wheel is central in the stays.

 

[the snail]

Are you sure the wheel is central? IIRC, some Orbits were built with asymmetric rear triangle, so the rear wheel is un-dished.

 

[tyred]

Definitely more likely to be to do with spacing I would have thought.

If you really need a spacer, then a bottom bracket spacer or spare lock ring would do perfectly but I doubt that's your problem. Is there space between the large sprocket and the spokes?

As mentioned, check the wheel is centred and dished properly. Bikes had a variety of dropout spacing over the years depending on number of gears used. An off the shelf wheel usually needs tweaked to suit your bike unless you've been really lucky.

 

[Alan O]

Are you sure the wheel is central? IIRC, some Orbits were built with asymmetric rear triangle, so the rear wheel is un-dished.

Yep. Definitely no asymmetric rear triangle - it's always been fine with standard dished wheels since new.

I'll get some photos, which should make it clearer than me just saying things - but there won't be enough time between sunrise and going out cycling today (on another bike), so it will probably be tomorrow.

 

[Alan O]

If you really need a spacer, then a bottom bracket spacer or spare lock ring would do perfectly ...

Wow, after all these years, I'd never realised BB and freewheel threads were the same. As it happens, I do have a spare BB lock ring, and it fits perfectly! But before I commit to that, I will check the wheel spacing again - as I say, with photos.

Thanks everyone.

 

[Alan O]

I got a couple of photos. I couldn't get much lighting, but hopefully you can see that the rim is central within the stays on this one...

This is what the freewheel looked like...

I've now tried fitting the spare bb lock ring as a spacer, and I can get the full range of gears - on the bike stand at least, but I'm not going out to test it in the rain. I might still need a bit of derailleur adjustment, and the chain might benefit from losing a link - but I think I'm pretty close now.

Thanks again.

 

[Nigelnightmare]

I'll bet your old wheel was 130mm "OLD" and your new one is 135mm.

 

[Alan O]

I'll bet your old wheel was 130mm "OLD" and your new one is 135mm.

Interesting thought, but it appears not. I've just measured - and with the wheel attached, the dropouts are 130mm apart.

 

[I like Skol]

Not central at all. That image shows the brakes over to the left and the tyre centreline also left of the seat tube. I think you have scope for adjusting the axle spacing.

 

[Alan O]

Not central at all. That image shows the brakes over to the left and the tyre centreline also left of the seat tube. I think you have scope for adjusting the axle spacing.

I don't think the brake is much of a guideline, as it had been pushed around and wasn't centred. I can see what you're saying about the alignment with the seat tube from that photo - but I'm not sure how much of that is due to an imprecise camera angle or to out-of-focus blurring.

Looking from above here, the tyre centre line really does look to be in line with the centre of the brake mount and the seat tube, and the tyre appears central within the seat stays and chain stays - but it is hard to be certain. I'd say there's maybe a millimetre to play with at most, but nothing like the ~3mm difference I needed. Hmm, hard to be certain.

Anyway, I'll see how it goes with the spacer as soon as I get the chance, and I might come back and try having a play with the axle spacing - thanks.

 

[midlife]

If the wheel is in the middle then just use a spacer, about 50p usually

 

[Alan O]

If the wheel is in the middle then just use a spacer, about 50p usually

As I say, I've done that now using a spare bb lock ring I had - so it was 50p less than that