What is the ideal ratio transmission

[jul]

FWIW, I bought my 36T Surly stainless ring in Manhattan for USD30 a few years ago. I wanted the stainless item so that I could easily fit a Hebie Chainglider. It is reversible. We were visiting NY anyway, and since it was about $15 cheaper than it would have been in Ottawa, it seemed like a good deal to me.

It seems indestructible--no obvious (to me) signs of wear. I had heard/read that Surly's rings can be less than perfectly round, so creating a tighter-than-usual tight spot on the chain. This one creates a tight spot, but not unusually so.

I do have a 38T Surly ring in good nick, with about 4500 kms on it, if anyone wants one.

Can you tell me please the tickness of the Surly chainring ?

This is my bolts chainring size, Nut : 7mm    Bolt : 8 mm

[jul]

Ok

And if i add this chainguard fixed to my new Surly chainring,  might i need spacers ?

https://www.sjscycles.co.uk/chainsets/thorn-high-quality-alloy-chainguard-for-110-pcd-rings-up-to-38t-black/

Should not need spacers but are the bolts long enough?
Putting a bashguard/chainguard on the outside and the chainring on the inside changes your chainline.
  Assuming your chainline was near optimum to start, that difference should not be a problem.  That is the way I run mine and my chainline is off by about 5mm, which I consider to be close enough.

Ok i see, the bashguard take the place of the chainring..

[John Saxby]

Julio, here's the Surly website description of their stainless ring: https://surlybikes.com/parts/drivetrain/stainless_steel_chainrings

The 36T which I have is 2.2-2.3 mm thick, and the 38T is 2.1 mm.

I bought single-ring bolts for my chainring (I have both alloy and stainless bolts).

Problemsolvers make a good product: https://problemsolversbike.com/products/drivetrain/chainring_bolts_-_24658

I don't have the separate bolts handy, so can't give you a measurement. I can do that in two weeks' time, when I'm back home in my workshop.

Hope this is helpful, Julio. 

[PH]

This is my bolts chainring size, Nut : 7mm    Bolt : 8 mm

That's the right length nut for either a double/triple chainset or a single ring with a guard in place of a 2nd ring.  It'll be too long for a single ring on it's own, the bolt will bottom out on the nut before the chainring is tightened.  The Surly chainring requires the same bolts as other chainrings,  some chainrings are thicker and made with a recess to compensate, I can't remember if that's the case with Surly.  If you try and buy some you'll notice they're either sold as single or double/triple without needing to give the length, from memory the length of a single nut is 4mm.
If you're buying the nuts will usually come together with the right size bolts, but on a single ring setup it doesn't matter if the bolt is too long, it'll just protrude a bit on the inside. Obviously you shouldn't use a long nut with a short bolt.

[jul]

I am surpised, Surly chainring is very slim to compare with my Thorn (6mm)

Might i use the same chain (3/32) ?

So, if i undertanstood correctly, i can reuse my actual bolts with , a bashguard or spacers around 5 mm tickness ..

[PH]

I am surpised, Surly chainring is very slim to compare with my Thorn (6mm)

In which case I'd expect the Thorn ring to have recessed holes to compensate for the extra thickness.

Might i use the same chain (3/32) ?

Yes, there will be no difference in the teeth width.

So, if i undertanstood correctly, i can use with the same bolt i have, a bashguard or spacers around 5 mm tickness ..

I don't know anything about spacers, I see no reason to use them, the correct bolts are pennies and if you need the chainline adjusting the correct length BB is my preferred way to do it.  If you did use spacers, they'd need to compensate for the missing ring, so 2.5mm would probably be about right. 

[geocycle]

When I switched from a Thorn chain ring to a thinner Surly one, SJS suggested 2mm spacers. I was struggling getting it centralised on the spider, not sure why but these did help. Of course you could just buy smaller bolts, or if you use your bashguard it would probably work well with the longer original ones.

[jul]

Thank you very much for yours responses

[jul]

I don't know anything about spacers, I see no reason to use them, the correct bolts are pennies and if you need the chainline adjusting the correct length BB is my preferred way to do it.  If you did use spacers, they'd need to compensate for the missing ring, so 2.5mm would probably be about right.

What do you mean ? , sorry i don't understand properly

[PH]

I don't know anything about spacers, I see no reason to use them, the correct bolts are pennies and if you need the chainline adjusting the correct length BB is my preferred way to do it.  If you did use spacers, they'd need to compensate for the missing ring, so 2.5mm would probably be about right.

What do you mean ? , sorry i don't understand properly

Sorry, I probably didn't explain it very well.  There's a couple of ways you can do this and they both work and there's probably also variations on those.
Basically to get the desired chainline you can either
a) adjust the chainring on the chainset with spacers
Or
b) assemble the chainset as it was intended and adjust the chainline by using a different length of bottom bracket
There's also
c) decide that the desired chainline isn't that important unless it causes you problems.

My preference is b

martinf makes a similar point in the other thread
http://thorncyclesforum.co.uk/index.php?topic=2169.msg95991#msg95991

 

[jul]

Ok PH,

I agree with you, but i will see this another time about the bottom bracket.. 

As well, do you think to add spacers is reliable ?

[PH]

As well, do you think to add spacers is reliable ?

I see no reason why they wouldn't be, if they achieved what I was trying to do I's have no hesitation in using them.