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-   -   Need New crankset for Trek 520 (https://www.bikeforums.net/bicycle-mechanics/1122138-need-new-crankset-trek-520-a.html)

supperap 09-16-17 10:38 AM

Need New crankset for Trek 520
 
Have a Trek 520 touring 2016 with a Deore triple crankset (48/36/26) . I will like to replace the crankset with a double 2x10 e.g 44/34t.

I have looked around, but there are no double crankset to fit the 520. One of the problem are, the chainline need to be 49mm to fit (the 520 have a MTB set up), and crankset with that chainline have smaller chainrings e.g 38/24.

So how do I get a crankset with chainline 49mm and 44/34 chainrings?

Shimano xtr have a 44/30, but 30t is too small for my touring.

Regards
Supperap

jimc101 09-16-17 12:10 PM

The bottom bracket determines the crank you can use; guessing, if you have a Deore, it's a HT2 (you haven't given the M number of the crank)

As long as it's a HT2 BB, the chainline is irrelevant, just stick a MTB double in, and it will work (on the basis you have shifters and a FD that match)

You are loosing a lot of low gearing going to the double, you are aware of this?

reptilezs 09-16-17 12:37 PM

get a road crank and fd. maybe a cross geared crank. add in new fd and you are good. assuming you still have bar end shifters

Andrew R Stewart 09-16-17 12:50 PM

This is some of the limitations modern cranksets have, no ability to vary the chain line easily. My choice is a tapered square arm set with the BB needed to achieve the 49mm chain line.


I do wonder if the OP has used this bike for it's intended purpose while in hilly country? Andy

bikemig 09-16-17 01:01 PM

Just lock out the inner chain ring and you get a 48/36 double, cheap and easy.

Frankly I wouldn't touch this set up. You can just not shift to the small chain ring. The job will cost you money and really doesn't serve much if any purpose.

maddog34 09-16-17 01:31 PM


Originally Posted by supperap (Post 19865607)
Have a Trek 520 touring 2016 with a Deore triple crankset (48/36/26) . I will like to replace the crankset with a double 2x10 e.g 44/34t.

I have looked around, but there are no double crankset to fit the 520. One of the problem are, the chainline need to be 49mm to fit (the 520 have a MTB set up), and crankset with that chainline have smaller chainrings e.g 38/24.

So how do I get a crankset with chainline 49mm and 44/34 chainrings?

Shimano xtr have a 44/30, but 30t is too small for my touring.

Regards
Supperap

swap a 34 t onto the XTR crank you mentioned... done.

supperap 09-16-17 01:44 PM

NOT possible
 

Originally Posted by maddog34 (Post 19865883)
swap a 34 t onto the XTR crank you mentioned... done.

Where will you find a 34t inner chanring for XTR M985 ?

fietsbob 09-16-17 01:50 PM

Being a Threaded BB shell , you can remove the bearing assemblies and use about any crank and BB you please..

supperap 09-16-17 01:55 PM


Originally Posted by bikemig (Post 19865838)
Just lock out the inner chain ring and you get a 48/36 double, cheap and easy.

Frankly I wouldn't touch this set up. You can just not shift to the small chain ring. The job will cost you money and really doesn't serve much if any purpose.

There are more problems to that: first The 48t is too big for me, and the outer 48t chainring have a bad chainline. And the q-factor for the chrankset is too large (175mm) for touring/Racing my bike.

supperap 09-16-17 02:03 PM


Originally Posted by Andrew R Stewart (Post 19865813)
This is some of the limitations modern cranksets have, no ability to vary the chain line easily. My choice is a tapered square arm set with the BB needed to achieve the 49mm chain line.


I do wonder if the OP has used this bike for it's intended purpose while in hilly country? Andy

I only use the bike as a race bike/gravel bike - not as a touring bike. A tapered square arm will be a downgrade!

Andrew R Stewart 09-16-17 02:05 PM


Originally Posted by supperap (Post 19865931)
I only use the bike as a race bike/gravel bike - not as a touring bike. A tapered square arm will be a downgrade!


I hope this is in jest. The downgrade already was there, the bike wasn't set up as you have found you want. Some measure their worth by the cost of the bike, others by their experiences when riding. Andy.

supperap 09-16-17 02:13 PM


Originally Posted by Andrew R Stewart (Post 19865937)
I hope this is in jest. The downgrade already was there, the bike wasn't set up as you have found you want. Some measure their worth by the cost of the bike, others by their experiences when riding. Andy.

I like steel bikes, but the Trek 520 was a replacement bike for Trek - so I just need to get the best out of it. And I like the bike , but the configuration is very weird!

Eggman84 09-17-17 10:56 AM


Originally Posted by supperap (Post 19865918)
There are more problems to that: first The 48t is too big for me, and the outer 48t chainring have a bad chainline. And the q-factor for the chrankset is too large (175mm) for touring/Racing my bike.

If I read this right, the OP is wanting a chainline of 49mm (same as the current triple crankset), yet is complaining that the existing outer 48t chainring is a bad chainline (I assume they mean they can't use the large chainring with all the cogs on the cassette) and the Q-factor is to big. If you want to go with a double, but be able to use all the cogs with both chainrings on double crankset, and reduce the Q factor, then you are going to have to reduce the overall chainline some. I don't think the 49mm is not a number that has to be adhered to.

Eggman84 09-17-17 11:03 AM


Originally Posted by supperap (Post 19865901)
Where will you find a 34t inner chanring for XTR M985 ?

You won't. That is part of the fun dealing with Shimanos crankset hese days; they are unique, FOr instance, the FC--M985 only comes in matched sizes of 28/40t or 30/42t chainring configurations. Also, if I am correct, this XTR 2x10 Crankset uses an 88mm Bolt Circle Diameter (BCD) that is unlike anything else on the market.


If you want to be able to chaining gearing easily, then you should "downgrade" to a square taper compact (110 BCD) crenkset. Otherwise, learn to live with what the manufactures tell you is the "best gearing" (until they change it next year).


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