Shimano ST-EF51 query

[langy]

hiya folks,
i'm after a bit of advice if you'd be so kind.

a few months back i purchased a B'Twin 5.0 RockRider mountain bike.

http://www.decathlon.co.uk/rockrider-50-men-id_8202062.html

now i'm thinking of changing the gear shifters as i've found that the 'gripshift' system already on it is too unstable for what i want... i slight unintentional twist of the hand whilst riding and the gears will jump down without a second thought......

the bike is fitted with a Shimano TZ-30 front derailleur,
a Shimano Rear Derailleur - no numbers on it, just the letters SIS
and SRAM MRX 21-speed (3x7) grip shifters,
oh and a Shimano TZ-21 freewheel

i would like to change to the Shimano ST-EF51 shifters......

http://www.ebay.co.uk/itm/290942217645?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

now my question is this...will the EF-51 work with the rest of the derailleur set-up ? or will i have to change other parts ?

many thanks for any replies.

[nfmisso]

If the number cogs and chain rings match, there will be no problem with function.

[1FJEF]

You will need to run the new gear shift cables through the new shifters & your bikes existing cable housing, not a daunting task. The brake cables & housings will simply reconnect to the new levers, extremely simple. Your grips may need to be replaced as the existing length may be too short for the new shifters.

[langy]

thanks for the replies gents.. it's much appreciated..

[Joe_W]

So the MRX grip shifters have the same cable pull as shimano? Or is the difference SRAM - Shimano only at 8speed and higher? I admit I was a bit confused when I read it...

[nfmisso]

SRAM MRX and TRX are Shimano compatible, and will not work with SRAM rear derailleurs. SRAM has at least one other Shimano compatible series of shifters.

[Joe_W]

Thanks for clearing that up (again, I guess)!