Mtb to road crankset conversion
 

Hi guys I have a 2012 Scott spark 60 and I got 3x9 drive train with 44t on the from crankset I want to put a 48t crankset on it but I don't know how to make it work the bb fits both coz am using the hallowtech 2 crankset when I tried it but the durailer don't work and it's a fixed one I don't know if I can position it higher or not and if not which durailer do I need to get to make it work?
I might spelled durailer wrong so don't mind me on it.
thank you

Try again with punctuation.

It really depends on the bike and kit.

My GT LTS-3 has a 56T chainring on the front, but I had to use a longer bottom bracket (square taper) to clear the chain stays.
More an issue, I still had to use different cranks, as the Shimano 105 cranks collided with the chain stays as they passed over.

If you have the more modern design of external bearings, I don't know if you can fit a road crank and space it adequately. And these days you're lucky to find large road chain rings to fit an MTB crank, as they're all over-styled and keyed-fitment (you know where you are with 5x130).

The derailleur height is one problem, but you may also need a different cage, as most MTB cages start colliding by around 48T even when raised to the correct height.

It's likely to be a tin of worms.

There are A LOT OF VARIABLES.

As mentioned above, clearance between the chainrings and the chainstay can be a problem. A longer bottom bracket may help, but then it can throw the front derailleur off kilter.

Is the rear triangle aluminum or steel?

I looked online, and the front derailleur mount looks a little odd. Can you try to upload some good high res photos (Try as an "attachment" using the paper clip. https://www.bikeforums.net/images/editor/attach.gif) Or, go to your Gallery page (and let us know).

https://www.bikeforums.net/g/user/491239


Most derailleur mounts have some vertical adjustment, but I can't say what Scott did on your bike. The curved seattube could be problematic if it all doesn't fit well.

https://static.bikehub.co.za/uploads...919152_med.jpg

Clearances look pretty tight to me.

The manual which I found here https://s3.amazonaws.com/assets.scot...N_spark_en.pdf says Shimano E-type FD. The mounting holes are beneath it and you can loosen them and slide it up to meet the bigger ring. It might have a plate that goes around the BB cup, or it might bolt right to the frame, but anyhow those two bolts beneath the cage, part 5 in the diagram below, are the ones. You'll need to put it in low gear and loosen the cable while you do this and hook it up and re-adjust it again afterward.

http://3.bp.blogspot.com/-lxvhx4om4t...comparison.pnghttps://i5.walmartimages.com/asr/0d6...0&odnBg=FFFFFF

That bike has a 73mm bottom bracket shell, so a road crankset isn't going to work. Hollowtech road(and most other road cranksets) are made to fit 68mm bottom brackets, so the spindle is not long enough to work in a 73mm bottom bracket shell. Even if you could make it fit, I doubt the crankarms would clear the chainstays.

Why? 44 in front and 11 in back with a 26 inch wheel is about 105 gear inches. You going to spin that out on a mountain bike?

50/11 wasnt enough fo me on my hardtail Merlin mtb, and even at 53 i was spending half my time there - with 2.35in tyres.

I'm assuming you have a 64/104 bcd. Try a 46 or 48 T ring in the place of the 44 for starters. Might need a spacer to shift the crank outboard.

Another thread that finds me longing for Ryan.

I believe you can buy Octalink Type II in 73mm.

And, I believe that Claris uses an Octalink Type II.

Of course, if the idea is just different rings, the OP may be able to find new rings for his existing crankset.

Get a conventional front der for the 48t. Should be simple to find.

Sigh... square taper makes things so much easier. Bikes are getting as bad as cars...

Easier said than done.

By having a curved seattube, it throws all the angles off.

Mounting the derailleur on the seat tube moves the derailleur forward, and in effect kicks the tail of the derailleur up.

It throws off the entire cage geometry, and you end up with capacity issues on the derailleur.

Perhaps also shifting issues as the derailleur is now directly over the midline of the chainrings, where the chain and teeth interface, rather than being behind the chainrings.

Thanks [MENTION=339610]Darth Lefty[/MENTION] for the research on the derailleur and manual.

Now, that is odd. The derailleur is apparently mounted to the rear swing arm/triangle. I think it makes some sense, as the derailleur typically overlays above the chainstays, and must be oriented with respect to the rear hub. So, with everything moving, you don't want the chainstays to bang into the derailleur, and angles would be somewhat better with the derailleur attached to the swing arm.

Attachment 610080

I think the first thing is for the OP to get back to us on exactly how much vertical adjustment he has on the derailleur. One doesn't need a lot of clearance, but perhaps a little as everything on the rear moves, and isn't 100% centered with the bottom bracket.

It appears as if Scott uses a custom derailleur mounting bracket, so perhaps one could fabricate one's own bracket (which could be used to move the derailleur either upward or outward, or both.

To some extent, one can dimple chainstays for clearance, but I don't think I would do it on non-round aluminum.

Of course, there could be other derailleurs that might fit that direct mount that would have slightly different characteristics. Or, one could modify the cage slightly if needed.

That is a point... SRAM has been making 10T cassettes for quite some time. It may be easier than trying to change the crankset and FD.

Shimano makes the Capreo that is a 9T cassette. I probably wouldn't use it for this app, but it can be adapted beyond its original scope if desired.

I was quite happy with my speeds, cadences and technique, but thanks.

Bike in question, at 50-11

https://i.imgur.com/qibB01J.jpg

i got 9 speed in the back not 11 mate it's not a 2018 model

the crankset fits perfect on the bb with no issue on my one it's just the derailleur is not working with it

The question was not the number of speeds, but the number of teeth on the rear cassette.

Most MTBs have 11T on the small cassette sprocket. If that is not the case, then go for a 11T small sprocket. It is a quick & easy substitution.

The SRAM XD cassettes also comes with a 10T small sprocket, although you may have to rebuild the rear wheel to get one of those on your bike (if the freehub isn't available for your hub).

I.E. A smaller rear sprocket is equivalent to a larger front chainring.

So, if you don't have enough vertical adjustment in the derailleur, you'll have to fabricate a mounting bracket similar to the one in the photo above.

It shouldn't be too hard to make. 2 holes for the bolts into the swingarm. Two threaded holes for the derailleur.

You'll have a better idea to the dimensions, but I presume one could use a small piece of 3/16" or 1/4" or so thick plate aluminum. Carve it out roughly to the right size. You don't need to particularly make it hollow, although it may have to clear parts such as the swingarm pivot, and may not be 100% square. :foo: