Swapping 10 speed dura ace crank set

[riksand]

Hi

Any reason I can’t swap an old dura ace 7900 crank set with 52/39 rings on for a 7950 crank set with 50/34? Both 10 speed.

I’ve got a 12-28 cassette at the back

I presume I’d have to shorten the chain a tad - and perhaps lower the front derailleur?

Those mountains in Italy are getting a bit much - even for an old grinder like me!

Cheers

[pq]

You're likely to need a new front mech. I tried to use a DA front mech designed for 53/39 chainrings on a bodged up compact - 47/34 I think it was. It wouldn't shift to the small ring becasue the cage was wrongly shaped. When I replaced it with a (Campag as it happens) front mech designed for compact chainrings, the shifting was fine. In your shoes I'd try your old front mech before spending the cash on a new one.

[Jupestar]

You can check the front mech if you can see the part number easy enough (assuming it's also Shimano). May well be compatable.

But also check the frame so that the FD can be moved a bit. Not a fixed braze on. Otherwise you might need to get inventive!

Assume both have the HT2 bottom bracket so, but double check it's the same BB.

As long as the chain and chainrings are in good condition should be fine

[cyclop]

Most braze on front mechs should still have a small amount of adjustment,generally a braze on slot,to accomodate your new set up.It,s often a case of suck it and see.

[keyboardmonkey]

You're likely to need a new front mech. I tried to use a DA front mech designed for 53/39 chainrings on a bodged up compact - 47/34 I think it was…

The OP doesn’t state their current shifters and front mech, but there is only one model for both a standard double and compact chainset in the 7900 range. Perhaps your problems had something to do with the fact your chainset was a bodge.

“It works with standard and compact chainrings (50t to 56t top gear max with a capacity of 16t) and comes in both braze-on and clamp-on designs for three seat tube diameters – 28.6/31.8/34.9mm.”

https://www.bikeradar.com/reviews/compo ... ur-review/

[TheBomber]

Most braze on front mechs should still have a small amount of adjustment,generally a braze on slot,to accomodate your new set up.It,s often a case of suck it and see.

Or measure it - ideal height changes by 2mm per tooth difference. So the OP is looking to lower the FM by 4mm.