Opinions, please...single speed crowd

[epptx]

So I've given myself a crash course in single speed setups.

I have a 1990 Specialized Hardrock.
http://www.retrobike.co.uk/forum/viewtopic.php?t=142923

Because I'd like to make some modifications, I just learned more about single speed drivetrains because no one responded in much detail to my posting here:
http://www.retrobike.co.uk/forum/viewtopic.php?t=143186

My bike has a 17-tooth freewheel. As I mentioned in the post above, I am considering changing my annoyingly short crankarms to 175 mm length.

So, here's where I am now. I've learned a lot more about BCDs, gear ratios, crank arms, and bb spindle lengths, and this is what (I think) I've decided to do:

1) Ditch my existing Sugino crankarms.
2) Ditch my existing 44-tooth big chainring.
3) Swap to these Deore DX MT-62 175 mm crankarms, with 38T ring (I'm planning on doing my first-ever restoration on this Hardrock, and this crankset seems like a relatively period-appropriate match.):
http://cgi.ebay.com/New-Shimano-Single- ... 230f70e099

What do you think? Look good? Any concerns?

p.s. I'm assuming I should be able to keep my Hardrock's existing square taper BB. Yes?

p.p.s. Aside from removing some links from my existing chain, I shouldn't have to do anything else with the drivetrain change, right? (Other than installing crankset and swapping pedals, of course.)

Thank you in advance for you help & feedback!

 

[andrewl]

I'll answer all your questions and more later this evening (my time)

 

[hamster]

Depending on where you live and the terrain to ride (road, offroad etc) then a 2:1 ratio is a good place to start - so a 34/17 is more likely to suit. Try the 38T, but I suspect it's a bit big - unless you ride on the road all the time.

The only other thing you'll need is a chain tensioner.

 

[IDB1]

Is there something wrong with the sugino cranks?

If not, why change them?

Ratio's are personal preference, 2:1 seems to be a common place to start.

You can probably get away with a shorter BB since you not accommodating 3 rings up front but, if you have spacers on the freehub, it won't matter much since you can adjust chainline that way.

Shorter chain, yep.. and find the 'magic ratio' or add some kind of tensioner.

 

[lewis1641]

idb not reading the post properly!

the cranks are too short dude.

from my experience you'll need to swapp the bottom brackek when you change over to the dx ones (which are ace cranks by the way)

are the sugino ones curved or straight? if curved you'll need a longer bb, if straight then you should get away with it. i think

as the bike is set up at teh minute is doesnt seem to need a chain tensioner. if you alter the size of the chainring you may find that you do need some way of tensioning the chain.

 

[IDB1]

idb not reading the post properly!

the cranks are too short dude..

sorry chap(s)..

As an aside (and because I'm probably going DX cranks on something later in the year).. why the BB change for those??

I asked about those re-cut tandem cranks earlier in the year and got a resounding 'not worth it, buy some over here that aren't re-hashed' type response..

But they seem an ok deal to me (which means nothing )

 

[bryan555]

I like the bike as it is, but it really depends how you're going to use it.

If it were mine, I would stick longer cranks on, DX are fine, 17:34 ratio, stick some nice wide risers on, anything I had/could afford to get it a bit lighter, then ride it

I saw a really interesting chain tentioner on the weekend. Godders was running what he called a 'ghost ring'. It's a 30ish tooth cassette cog that's popped between the cassette and the chain ring pushing the chain out and adding tension! It worked really well for him, and looked pretty cool.

Good luck with the build

 

[andrewl]

Right, I've now read through your various posts about your build which in summary sounds as follows:

1) You've got a single speed which someone has built up previously and works well
2) You use it for urban rides and not off road
3) You don't like the 170mm cranks

Now looking at the photos I get the impression that you aren't massively tall (less than 6?). The rear hub also looks like a screw on one where the hub has been spaced to get a good chain line.

In my opinion I think you are looking at this the wrong way round. Yes I know you'd like 175mm cranks but unless you can find some with the same chain line as the current cranks you will probably need the following:

a) new cranks
b) new front chain ring
c) new bottom bracket
d) chain tensioner, half link or half link chain

and if you can't get a good chain line

e) new rear wheel which cassette hub
f) new rear cog
g) single speed spacing kit

and to me that seems like a lot of money just because you want cranks 5mm longer on an urban bike.

In my opinion I'd look at keeping the cranks and going to a smaller front chain ring so that you can spin faster on the shorter crank arms and thus use them to your advantage (and go easy on the wallet).

So I'd buy a 42T chain ring and half link to shorten the chain to the correct length and be done with it. Maybe a 41T or a 40T if 42 still feels too high. You could change to an 18T on the hub but as its a screw on job changing the front ring is a lot easier as you'll retain the same chain line.


Note: I'm basing all this on my own single speeding on MTB and road and track riding. I'm slightly over 6ft and have long legs for my height. I normally use 175mm off road but have used 170mm for road single speeding with no problems just by adjusting the gear slightly and spinning more.



[/list]

 

[andrewl]

Or if you really want 175mm cranks, buy these Sugino ones

http://cgi.ebay.co.uk/Sugino-Impel-...ikeparts_SR&hash=item1c1a899792#ht_500wt_1156[/url]

 

[IDB1]

Is there that much real-world difference (5mm aside) between 170 and 175mm crank arms? Seems like such a small amount..