SRAM MRX 5 spd shifters compatibility

theboytaylor

Well-Known Member
Location
Charlton, London
Hi all,

Looking to convert an old 5 spd road bike to flat bar and if possible replace the downtube shifters with something bar-mounted.

I've seen these but wanted to know:

Are the shifts indexed - i.e twist the grip and it "clicks" to the next gear?
If so, is the spacing of each "click" going to be compatible with the spacing on the cassette?

I know Sachs Huret is now SRAM, so hopefully they're compatible. Checking on Sheldon Brown, etc, suggests to me it will be OK, but I put my trust in your knowledge!

Thanks
 

RecordAceFromNew

Swinging Member
Location
West London
If your cassette is Shimano compatible, then the answer is yes (from the horse's mouth...).
 
Not so much the spacing on the block, though they are compatible. The stumbling block is likely to be the rear derailer, chances are it's a pre-index mech and therefore unlikely to work.

If the mech is compatible (it'll say SIS on it) consider getting the six speed version of that shifter, the spacing is the same as five so it'll work ok but the extra click will enable you to upgrade to a six speed freewheel when you come to replace it.
 

RecordAceFromNew

Swinging Member
Location
West London
Mickle made an excellent point - there is indeed a potential pitfall that the old rear mech might have a different cable pull:cassette pitch ratio compared to the more recent Shimano standard of 1.7. If the OP can show us what rear mech he has perhaps someone might be able to confirm one way or other. It is not a big deal if the existing rear mech is incompatible - an ok one can be picked up for very little.

However a "Standard 6" speed freewheel will not work on a 5 speed hub, given the 5 and 6 speed hubs' OLN distances are different (i.e. 120mm and 126mm respectively). While an Ultra6 freewheel will fit perfectly on a 5 speed hub, it has different sprocket pitch and will not work perfectly with 5 (or standard 6) speed indexing. So I believe the OP should get a 5 speed shifter if he intends to keep his 5 speed rear wheel.

I appreciate one can convert a 5 speed hub to take a "Standard 6" speed freewheel with spacers and the like if one insists, but it is a rather involved conversion involving frame cold-setting and wheel redishing etc.
 
OP
OP
theboytaylor

theboytaylor

Well-Known Member
Location
Charlton, London
Thanks for your help so far.

Here are a few pics of the bike, the derailleur and the freehub, if they help. If you need any more, let me know as the bike's currently led in the garden! The cassette's Maillard and the mech is Sachs Huret - EDIT: I forgot to mention this in my first post-sorry! Looking at the frame stamps the parts were mainly made in 1987, fact fans.

As you can see, the bike's already converted to flat bar. It's hopefully going to be a station bike for Mrs TBT but she's not too keen on downtube shifters so I'm looking for a cheap conversion if possible.

Cold setting and re-dishing wheels is probably more faff and expense than I want.

Record Ace - would that rear mech you linked to work with 5 spd?

Mickle - out of interest why wouldn't a non-index rear mech work? Isn't the amount of cable pulled at each shift being dictated by the shifter (if that makes sense!)?
 

RecordAceFromNew

Swinging Member
Location
West London
All current Shimano rear mechs (including the one CRC is selling for £7 incl p&p) have the same shift ratio and therefore will index with all current Shimano (or Shimano compatible, such as the SRAM MRX) shifters.

The reason why shifters have to be matched with rear mechs to index for various cassette pitch is explained here.
 
OP
OP
theboytaylor

theboytaylor

Well-Known Member
Location
Charlton, London
RecordAceFromNew said:
The reason why shifters have to be matched with rear mechs to index for various cassette pitch is explained here.

Thanks - I read this earlier (but didn't totally get it) and this is what made me think that a 5spd SRAM changer should have the correct shifting pitch to match an old Sachs 5 spd cassette (freewheel)....
 
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