Chainring swap - Shimano and SRAM

[PaulSecteur]

Hi,

When I bought my MTB it has an FSA chainset with a 24-38 combo on it.

It worked OK, but the cranks flex a bit and... well... it didn't look nice. I spotted a good deal on a shimano M675 crank and put that on, but it came as a 26-38.

I would like to put the 24 tooth SRAM on my shimano chainset. I *think* from memory they are both 104 / 64 bcd.

Also, I have never swapped chainrings before, will I need any special tools or any tips?


Cheers, Paul.

 

[mrandmrspoves]

You can swap between manufacturers - but it may lead to less crisp gear changes. Different manufacturers have different systems to improve gear changes. If you look carefully on the inner surfaces of the chain rings you may find little tags called ramps that help scoop the chain up from one ring to the next. If you decide to do a swap, it is much much easier if you take the chain wheel off the bike to do it. Mark the chain rings so you know which side is the outer side and where it sat in relation to the crank arm. As for special tools, obviously something to take the crank set off the bike, the right size Allen key and for the back of the chainring bolt there are special tools - one looks like a screwdriver with a small amount of metal removed from both ends of the tip leaving a small raised central area, you can make one cheaply if you have a screwdriver and a Dremel (other rotary tools are also available) The other type of tool is similar but looks more like a spanner. (Search for chairing tool on eBay or Amazon and you will see pictures of both types of tool. If you are lucky the chain ring bolts will undo easily with just a standard screwdriver in the back to stop the bolts spinning. You can increase the likelihood of this by giving them a good spray of Plusgas or alternative penetrative oil and leaving for a day or two.

 

[PaulSecteur]

Thanks for that.

Im going to be going to to the Spesh concept store tomorrow, theres a shimano service centre next door so if they have the right part I will get that, if not I will swap the SRAM cog in.

Im not too fused about the front change, im always on the small ring.

 

[cyberknight]

Assuming they have the same bcd and number of bolts holding them on i cant see a problem, im currently using stronglight and fsa mix .

 

[2Loose]

Having just bought and failed to put a Shimano SLX 38T outer ring on an SRAM crankset, I can assure you that 104 BCD does not mean the tabs on a Shimano chainring will fit an SRAM spider with 104 BCD. :-( I'm sure Shimano stuff fits a wider range of brands, but it seems SRAM are more picky...and pricey. SRAM and Truvativ. There is a nice chainring compatibility checker on the Evans Cycles search filters...shame I found it afterwards :-)