1x8 Crankset/BB Options

jonnyboy77

Technically not an MTB but MTB related, I'm wanting to change out my current 3x8 setup to a 1x8 - the bike is a '99 Trek 7500 hybrid and has:

Cranks: Shimano Nexave 400, 28/38/48
Bottom Bracket: Shimano BB-LP27 (110mm axle / 73mm shell)

I've been looking at single chainsets like a truvativ isoflow, but would need a bb to suit. I'm hoping to keep the cost low - any recommendations that I could carry over from MTB stock onto this bike?

Best option at the moment seems to be an eBay buy:

Truvativ Isoflow SingleSpeed C/Set 175 Powerspline 42T + PowerSpline Truvativ Bottom bracket - Combo pack - 68mm bb though so also need get the 73mm Truvativ Powerspline BB from CRC

Total cost of about £80 - can anyone do better? Or has a better suggestion?

Thanks

Jon

nicklouse

dont bother with power spline.

what is wrong with your current cranks?

jonnyboy77

I remove the front derailleur (broken) and don't use the 3 rings, just the outer ring - but the chain doesn't like to stay on the outer, prefers the middle.

So as the crankset dates back to 1999 (along with the BB) I'm looking to go 1x8 with a new 38-42 crankset and BB (depending on what's cheap!) at the front and leave the current 8sp cassette/derraileur at the back.

The hybrid is a workhorse (shopping runs, hamax seat for little one, etc) so not looking for optimal speed or anything - I have owned a Gary Fisher that was 1x9 with a 38t single at the front which was fine for pootling.

Any single crankset & BB suggestions that have a budget cost without being crap?

Thanks

Jon

nicklouse

again what is wrong with the current cranks?

remove rings and fit a size that you want.

jonnyboy77

From what I can tell thats not an option




The current triple and BB is old/annoying, and so I want to replace it with a single and bottom bracket to suit at a sensible cost.

Any suggestions on a suitable single and bottom bracket?

Thanks

Jon

jonnyboy77

Anyone have anything to add?

I'd really like to replace the current triple and bb with a single and suitable bb mated to the existing 8 speed rear setup. It seems that the Truvativ powerspline option is not favoured, but I'm struggling to find a source of positive information ...

Thanks

Jon

The Rookie

Just get some square taper cranks, keep your BB and get a large ring and fit in the middle location, you'll probably need a chain guide to keep it on

1/ Square taper cranks
2/ Large ring (or single specific ring)
3/ Chainring bolts
4/ Chain guide or old front mech locked off on the hi/lo stops

By all emans change the BB if its no good, but if it works.......

You could get a 'stronglight 55' (available on ebay for circa £33) and not need 1,2 or 3, as long as it has the right tooth count for you.

Simon

jonnyboy77

The Beginner wrote:

Just get some square taper cranks, keep your BB and get a large ring and fit in the middle location, you'll probably need a chain guide to keep it on

1/ Square taper cranks
2/ Large ring (or single specific ring)
3/ Chainring bolts
4/ Chain guide or old front mech locked off on the hi/lo stops

By all emans change the BB if its no good, but if it works.......

You could get a 'stronglight 55' (available on ebay for circa £33) and not need 1,2 or 3, as long as it has the right tooth count for you.

Simon

The reason for replacing the BB was mainly a 'while I'm messing around with the chainset' option, its old so probably due a replacement.

Thanks for the information though - I'm wondering if I get this chainset (http://www.chainreactioncycles.com/Mode ... elID=46025) and remove the chainrings, adding a middle ring of my choosing and a chain guard on the outer.

Plenty to think about.

Thanks

Jon

nicklouse

ah one that old.

any crank and suitable BB. BUT i would steer away from powerspline/powerdrive/ISIS.

SQ taper nice and reliable and cheap. Octalink I like.
External not needed. (but can be a cheap option if you look to sell on the rings)

SS specific are over rated and not really needed.

My SS MTB uses old XTR octalink.



the fixed uses MTB crank and ring and chain guard.


there are so many options.

jonnyboy77

nicklouse wrote:

the fixed uses MTB crank and ring and chain guard.



there are so many options.

This is closer to what I'm looking for - thanks for the information. I'm now scouring for a crankset or pair of crank arms I can use on the current BB and if I find a cheap replacement BB I might swap that out too.

Thanks

Jon

nicklouse

Jon all that is is an MTB triple with "bash" (well 3mm guide ring). running a 42T outer on the middle.

jonnyboy77

nicklouse wrote:

Jon all that is is an MTB triple with "bash" (well 3mm guide ring). running a 42T outer on the middle.

That's what I thought - so I'm looking out for an MTB triple (w/removable rings!) and need to source a low cost guide/bash ring.

I have a few irons in the eBay fire, but also see a few reasonably priced MTB triples for sale new. The guide or bash ring I'm having less success with so far!

Thanks for your help - I am in unchartered territorty really, since my last real bike tinker was done over 15 years ago and I seem to have forgotten most of what I learned

- Jon

The Rookie

My daughter runs a roadie crankset with the 53t outer ring swapped for a guard (salsa crossing guard) if you want something slightly different (no need to use a guard if you don't want one) and runs on the middle 42T (just like many an MTB outer) wheel, you may find this combo cheaper and road stuff tends to be lighter, my daughters Truvative Elita combo cost just £20 (used off a Boardman circa 2009 we think) complete.

Simon

jonnyboy77

The Beginner wrote:

My daughter runs a roadie crankset with the 53t outer ring swapped for a guard (salsa crossing guard) if you want something slightly different (no need to use a guard if you don't want one) and runs on the middle 42T (just like many an MTB outer) wheel, you may find this combo cheaper and road stuff tends to be lighter, my daughters Truvative Elita combo cost just £20 (used off a Boardman circa 2009 we think) complete.

Simon

Cheers - I've added this to my searches, I hadn't thought that square taper road cranks might be suitable too.

I did find some singlespeed chainrings too, but they seem to suggest that they won't run with 8-10sp chains, so I'm focusing on MTB or Road based sets. I'll strip the current setup down at the weekend in preparation!

Thanks

Jon