Hi all,
I want to replace the 52 t 130bcd large chainring 5 bolt with this origin 8, 130 bcd ring because the original 52t ring is worn. This is for the FC 6703 triple ultegra. Does anyone know what size chainring bolts are needed to do this? I cannot use the original bolts since they are too long. The original chainring has that thicker section where the bolts are. The old is shown below and the new also.Thanks in advance.

That chainring doesn’t have the threading the Shimano one does. Maybe you can screw some M8s in backwards - is that how you discovered the original Shimano bolts are too long as they clash on the small ring maybe? edit: actually the middle ring doesn’t have any threading either. What are you going to screw the bolts into?

The Shimano one has a bunch of ramps too, shifting up into that one isn’t going to be nearly as crisp but you probably know this.

I was going to use chainring nuts in place of the threaded large chainring.

Do you mean using a nut like the below? With the 'slotted' nut end on the outside?



With the normal use of this bolt/nut, the crank arm holes are large enough for the 'nut' part. The OD of the nut is about 10mm (green line). What is the ID of the holes in your crank?

If the nut cannot pass through the crank arm, the nut would have to be really short (blue) or it will 'bottom out' on the arm before the head tensions the Cring.

Note that the #s in red are not correct (stock pic from ebay). The 'head' portion of both pieces may be larger than 10mm.

And you would want to do this because ........ ?

https://si.shimano.com/en/manual/search?model=FC-6703
This may help.

The OP said the original chainring is worn.

OK: assuming that the OP is replacing the original 6703 (large) chainring with the pictured Origin ring, then standard 2-ring chainring bolts should allow one to attach the existing small (39 or 40 tooth?) to the new big ring.

I don't know the exact dimension of the bolts, but they are the most common ones on the planet. The bigger issue is that the Origin ring has no pickup pins or ramps, so the shifting will be slow and clunky relative to a quality big ring from the last 25 years or so. At our bike Co-op at any one time we have 20 lightly used large rings with a 130 BCD, because these don't wear out as fast as the smaller rings.

In order to wear out the big ring before the middle, you must ride faster than almost everyone, including myself.

You’re short one ring there. The small on these is 30T and middle is 39. The big ring does bolt to the middle and expects the bolt head to be on the inside. OP would possibly get away with chainring nuts on the outside.

I'm not sure I follow what you mean by this, but the new chainring goes on just like all chainrings used to, with the allen head of the chainring bolts on the outside, running through the holes in the spider arms and then into the slotted part of the bolt in the middle ring. It will come out like this:


The granny ring has its own mounting bolts and gets left alone.

Unfortunately i dont have a coop nesr me. I would prefer to replace the large ring with original new one I have not found one. Maybe there is a better replacement. I am not the original owner of it but like this crank. I am guessing someone used it on a indoir trainer and wore out the big ring.

Large 6703 rings are somewhat hard to find, and very expensive, due to the alu/carbon laminate construction. I assume this fancy construction is to make the big ring 'stiffer'. However, I have rigged and run Shimano cranksets of that era with standard flat/cut large rings and could detect no difference in shifting performance. That is, with the pickup pins and ramps found in modern rings, the shift performance is really good.

Oh ok - I was actually assuming the bolts and nuts weren’t so readily interchangeable and the middle ring would want the bolts on the inside. Your way round makes sense now I engaged my brain.

I wore mine out on the road. That 52 works fine with approx 14-28 cogs on the flat/gently rolling terrain.

with the information provided it is hard to advise you properly but I believe you are going to need bolts for a "single" chainring - something like these

https://www.ebay.com/itm/324171387574

buy the 2 piece nut and bolt combo and the just use the bolts

/markp

As I showed in post 10, with a normal outer ring you use normal chainring bolt pairs. The 6703 outer ring serves as the slotted nut, so you need both the bolt and nut.

yes that looks like it would work in terms of size and what i need. I probably will give it a go.Thanks

Yes I will see if I can find the flat cut type and then will use that with the chainring bolt and nut from feebay.

T.A. also makes 130 BCD chainrings for the 6703. These are very high-quality rings and I believe you can use your original bolts and also come in a 50t. https://www.peterwhitecycles.com/tach.php#ultra130 scroll down the page to "Ultra 130 Outer for Ultegra 6700 Double 10 Speed & 6703 Triple 10 Speed"

Those are too short. You need normal double bolts that are for two chainrings.

Nice, they even do a grey version to better match.

Thanks for pointing me to this site. They have quite a selection of chainrings. What are the hegoa and alize inner? I saw that on their site. This looks like a drop in replacement with no different chain bolts needed.

ok, thanks. They should be easy to find then.

The 6703 can use just about any replacement middle and small chainring so TA just sells standard rings for that (5 hole 130 BCD) and they are basically more durable the higher the price. They also sell a version that is machined down to a very lightweight, i.e. less aluminum, HEGOA chainring which IMO is not worth the extra cost, the ALIZE will work. The outer "ULTRA" chainring has the special covers included mostly for looks and I believe either includes special bolts or you can use the original ones that screw into the backside of the rings. The webpage is a little overwhelming with all the choices but you can narrow it down to Shimano compatible by skipping anything listed for Campy or has the wrong BCD but has 5 hole mounting.

you can look at the TA website all day long but you can't buy anything there.

Peter White Cycles in New Hampshire is the best source in the US for TA parts and they may be able to help you on mounting hardware

https://www.peterwhitecycles.com

/markp