Double and bash advice...crank length, etc

luv2ride

Hi all. So, I was going to buy a 2012 Trek ex8 from my LBS but someone has beaten me to it. As I wrestling with my conscience trying to justify it I'm now thinking of upgrading my Stumpy FSR Elite 09 as a lower cost alternative. For now I'm thinking of swapping out the non-series crankset (fc-m542?) to an SLX double and bash. current cranks are 175mm. should I go the same on the SlX or go shorter at 170mm crank arm? I'm 5'8" and bike is a medium.

I'm guessing a longer crank means better leverage on climbs, but shorter crank arms mean fewer pedal strikes on rocks?

Any other things I need to consider (new front dérailleur, BB axle lengths, etc)

many thanks

mcnultycop

I doubt you'll notice 5mm difference.

nicklouse

same.


why not convert the existing?

if you go for external bearings get the shell faced.

felix.london

I think my three bikes all have different crank lengths - can't tell the difference.

Adotparker

content removed due to poster idiocy.

felix.london

How much weight are you saving?

luv2ride

So, probably best to stick to 175mm crank length? do I need a double slx front dérailleur, or will my current slx triple suffice? whilst on the subject, what about front shifter, will my existing shifter work ok with the double crankset?

cheers

Chunkers1980

Yes it'll all work as is. Just adjust the stops

mcnultycop

Is there anything wrong with your crankset as it stands or do you want to change the ratios? You could just replace the outer chainring with a bashguard and see how you get on with it for next to no cash.

The Rookie

Most people really can't tell the tiny 5mm difference, but as your shorter I'd suggest the 170's as it will reduce your knee articulation slightly.

The SLX double and bash is a heavy duty set and the parts weigh more than the stock 3 ring SLX, if you don't need the extra strength then get a triple and buy a lightweight bash to go with it.

You shouldn't need a different front mech but you will need the frame faced at your LBS (£15-20), the SLX comes in one axle length and you add spacers to create an 83mm effective shell width (3 spacers for a 68, 2 for a 73mm frame shell).

nicklouse

The Beginner wrote:

Most people really can't tell the tiny 5mm difference, but as your shorter I'd suggest the 170's as it will reduce your knee articulation slightly.

shorter! more like normal. 170 will more likely be a pain.

The Beginner wrote:

You shouldn't need a different front mech but you will need the frame faced at your LBS (£15-20), the SLX comes in one axle length and you add spacers to create an 83mm effective shell width (3 spacers for a 68, 2 for a 73mm frame shell).

if you are going to quote numbers please get them correct.

The table below outlines the spacer arrangement for the Shimano® XTR FC-M960, XT FC-M760, Saint FC-M800, Race Face® X-type, and FSA® MegaeXo bottom bracket bearings as installed into 68mm and 73mm shell widths. The E-type brackets and International Standard Chain Guide bracket options are also listed. The bearing cups are of a similar design, and cups are designed to be spaced 75.5mm apart. Three spacers of 2.5mm are supplied to achieve this width. E-type front derailleur brackets, or a chain guide mount, are counted toward the width total.

paul.skibum

I like Nick - he's good.

Adotparker wrote:

content removed due to poster idiocy.

This guy however. Less so.

felix.london

Adotparker wrote:

content removed due to poster idiocy.

Thank you

The Rookie

nicklouse wrote:

if you are going to quote numbers please get them correct.

Indeed, brain fade, my bad!

luv2ride

was going to get the SLX double on the current CRC offer (seems a steal deal). just about convinced myself but this latest lot of postings is makking me think twice. partly wanted a new hard wearing double, and heard SLX were pretty bombproof and long lasting. seemed a neat solution to get a " series" crankset on the Stumpy and try something a little different at the same time. Rarely use big ring at the moment. Anyone know what the current non-series FC-M542 crankset i have equates to? older Deore? the insides of the crank arms seem to be "scalloped" - does this sound like they're Hollowtech II?

felix.london

I went down the SLX double/bash route at the beginning of the season - replaced the old '06 Deore set (not sure exactly which model as all markings had been rubbed off) plus got the SLX double specific mech and shifter. Very happy with the set up. I like the gear ratios I have now - a big improvement all round. And with the 22/36 upfront you can get away with a medium cage mech out back (if you go for a 11-32 cassette)

The Rookie

All the Shimano's I have are scalloped, so no not HT or HT2.

Any of the HT2 range are good buys, the Deore are best value and can be had for circa £50-60, SLX is a bit lighter with better rings. Easy enough to change a big ring for a bash if you want the lighter weight of th non double and bash (Shimano bashs are HEAVY and they use a thicker axle according to the MBUK reviews).

luv2ride

mmmm. I ordered the SLX double crankset from CRC, mainly down to price and going for a ride last night on the triple convinced me that the gearing of the 36-22 double would be a better range than the (44)-32-22 SLX triple after I'd swapped the big ring with a bash guard. factor in a possible different ratio middle ring and the converted triple SLX with bash started to look a much less favourable option, although I had heard the SLX double was heavy

will see how I get on with the installation, and will probably get BB shell faced this weekend by LBS in readiness. hope it goes in as easily as some people have said they do, as I have a long history of botching home bike mech jobs!

luv2ride

any views on whether it's worth also fitting a black spire stinger (bb mount) while I'm fitting the new double? understand this may help keep chain on and reduce noise? I also see from a previous post that Felix.london has one.

would you recommend? CRC have them on offer at the moment...
cheers

felix.london

I've nearly completely eliminated chain slap with the set up. Mainly due to the fact I can run a medium cage mech but the Stinger def helps too

yukonman

nicklouse wrote:

same.


why not convert the existing?

if you go for external bearings get the shell faced.

Hopefully not to sound like a complete noob - why would Luv2ride need to get the shell faced? I've recently changed from a FC-M521 to XT BB and crank and it fitted ok - is it just a case of why not?

The Rookie

Many BB shells do not have parallel faces (it costs more to make sure they are, this is fine for an internal BB, but for an extrenal BB it can mena the bearings not sitting square on the axle it will all 'fit ok' though, the first you'll know is trashed bearings in 4 months time.

luv2ride

Felix.london - and worth going for the SLX double front mech. My current is a Direct Mount SLX triple and the double version seems rarer than hens teeth. Think this is the one I need:
http://www.chainreactioncycles.com/Mode ... elID=83607
but take the bb mounting plate off?

felix.london

Luv2ride wrote:

Felix.london - and worth going for the SLX double front mech. My current is a Direct Mount SLX triple and the double version seems rarer than hens teeth. Think this is the one I need:
http://www.chainreactioncycles.com/Mode ... elID=83607
but take the bb mounting plate off?

This is the one I have;
http://www.chainreactioncycles.com/Models.aspx?ModelID=28028

felix.london

Luv2ride wrote:

Felix.london - and worth going for the SLX double front mech. My current is a Direct Mount SLX triple and the double version seems rarer than hens teeth. Think this is the one I need:
http://www.chainreactioncycles.com/Mode ... elID=83607
but take the bb mounting plate off?

This is the one I have;
http://www.chainreactioncycles.com/Models.aspx?ModelID=28028

luv2ride

To The Beginner: I already have an external bearing BB, do I still need to get the shell faced? cheers

To Felix.London: I'm not sure I can use a front mech with a seat post collar as my Stumpy has a DMD fixing plate for the front mech. Everyone seems to be out of stock of them though at the minute. Might delay my garage antics....on the plus side the double and bash and chain tensioner have both been shipped and are on their way!

Apologies in advance, may well be some fitting and / chain length questions when assembly starts :roll: