RoboIsGod

I've got a DA 7402 crankset but the large chainring (52t) is getting pretty warn and I'm thinking of replacing it. Finding the matching 7402 ring is going to be tough but I've been finding some DA and Ultegra rings from the 7700 series. Would the 7700 series, which is 9 speed btw, work with my 7402 drive train which is 8 speed (I have DA 8 speed derailleurs, cassette, shifters, etc). They are both have a 130 bcd and look very similar. Are the 7700 rings narrower because they are made for 9 speed? Will this cause any chain/chainring noise or extra wear?

Thanks!


PS: The ring set up I have now is 39-52. Would running 39-53 be a big deal?

RoboIsGod

Anyone?

T-Mar

Well, the official answer from Shimano would undoubtedly be "No"but then they'd want to sell you a whole new 9 speed drivetrain. According to Sheldon Brown, "using wider chains with chainrings intended for narrower chains is not generally a major problem if there's only a one- or two- generation difference. The only problem you might run into is that the chain will be more liable to rub on the inside of the bigger chainrings in the small/small crossover gears, gears you shouldn't be using in any case. "

https://www.sheldonbrown.com/speeds.html

balindamood

I have had some issues down shifting with wide chains on narrow chainrings where the chain wants to ride on top of the teeth of the smaller ring. This is fixed my decreasing the chainring spacing. Easy if yoiu happen to have spacers/shims on the original set-up (unusual), a bit more delicate if you need to bend the chainrings themselves.

bradtx

RIG, I don't remember is the DA8 had Ti chainrings or not, if it does you may want to both chainrings just for cosmetic reasons if using chainrinsg from another group. My old calipers have broken, but comparing my DA9 with a spare 8S 600 and a spare '98 8S Ultegra crankset I can't see any difference in the chainring's thickness, maybe spacing between the two, but can't be positive.

I'm pretty sure the 9S chainring itself will be fine with the 8S chain and crankarm. The difference between 52T and 53T is nearly nothing.

Brad

miamijim

I dont see it being an issue. I'd have to do some research but I think the main difference between 8 and 9 speed systems isnt the thickness of the rear cogs or front chainrings but its the thickness of the rear spacers.

More thin rear spacers required thinner chains to prevent rub but I think was primarily accomplished via thinner side plates versus a decreased inside dimension. Think about it, Shimano 7 and 8 speed rear cogs are 1.8mm thick while the 9s cogs are 1.78mm thick.

Now, if we logicly think about this in relation to front chainrings and we assume Shimano's 9s ring is thinner its only going to be thinner by .02mm. Thats .0008". Use the 9 speed ring.

Old Fat Guy

Not sure at all on Shimano, but on Campy you can use 9 speed rings on a 8 speed drivetrain. To use 10 speed rings on an 8 speed drivetrain, you need spacers on the chainring bolts. Branford sells them.

I wouldn't expect any problems going to a 9 speed crankset on an otherwise 8 speed drivetrain.

gaucho777 

One more caveat to consider--and, forgive me, I don't know the answer: There *may* also be some differences in the width at the of base of the chainring where it meets the spider, as viewed from the drive side. I'm not talking about thickness when viewed from above. It may be that the spider arms are not the same size/width where they meet the chainring. (I hope I'm explaining this clearly.)

I mention this because I am also in a similar situation, in that I bought a used 7400 crankset which came with replacement chainrings (Shimano and Specialized). The small chainring is 42T, and I plan to replace with 39T at some point. I sampled a couple spare 39T Shimano chainrings with the same BCD (Shimano 105s, if I remember correctly), and the chainrings did not line up flush with the edge of the spider arms. I expect the chainrings will function fine, but may be objectionable to a persnickety aesthete.

I would love for someone with a 7400 series crankset and, say, 7700 series crankset to be able to confirm.

gaucho777 

Further to my previous post above, here's a photo:

RobbieTunes

I've used FSA replacement chain rings, and never had a problem. I also mix/match 8s and 9s rings.

gaucho777 

Sorry to belabor the point, but I went back and measured a width of 16mm on my 7400 cranks where the spider meets the chainring. I would be grateful if someone could confirm a similar measurement on a Dura Ace 7700 or comparable crank. Thanks.

miamijim

That measurement has nothing to do with anything. The thickness of the spider arm may, but certainly not the width.

gaucho777 

From a functional standpoint, I agree that measurement is practically irrelevant. But that measurement is meaningful in one respect: I don't want the chainring to extend beyond the spider as shown in post #9 above.

RoboIsGod

Thanks all for the replies!

THEJAPINO

I have a 7410 crank and 7700 chainrings. They match well and the width of the mount where the chainring meets the spider is 16mm. Order it!