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A question for the techies re single chainring size..

Morgan's picture

By Morgan - Posted on 07 July 2009

OK, so most regulars know I ride a coupla bikes with Rohloff Speedhubs, ie - one chainring, one sprocket.

So I don't need to spend a few unavailable $ on a custom roadie (unless someone can show me an off the peg roadie for a +2 metre, 105kg behemoth) I want to convert my hardtail to a "training commuter" which means looking at the gearing. Offroad I ride a 39 ring / 16 sprocket which gives me the smae gearing as an average MTB. I want to go bigger gears by increasing the size of the chainring. The biggest I've tried is a 46t which gives me about 1 more top end gear than your average MTB but nowhere near the size of gearing of a roadbike.

I'm thinking of going 50 or 52 but my problem, I think, is that I have a 5 bolt MTB crankset. The BCD is 94 which I also reckon is pretty small.

2 questions -

1) Is it likely I'll find a 50 or 52t 94BCD chainring , because I've been looking online and not found anything yet and
2) If I had to get one built would I need to think about the strength of it with such a small spider?

I shall probably have to just get another crankset I'm sure, but you techies feel free to debate like I know you love to! I'm interested..

delicious's picture

I'd say buy a track crankset, provided your bike has a 68mm BB. They are SS, have a 130 or 144 PCD and thus you can customise the ring size. Plus the ring is not ramped so the chain won't come off and a guide is not req'd. FSA is a brand you might like.

Damien's picture

I think you will be up for a new crank & ring Morgan.

Have a look at Surly's stainles steel chainrings they start at 35T with a good selection right up to 50T in either 110BCD or 130BCD.

For my SS road bike I wanted at least a 175mm crank or 180mm and all track cranks I could find where no longer than 170mm and the fact that 99% of 144BCD rings came in 1/8 chain size wasnt a big selling point as I run 3/32 chains and freewheels.

If you use a ring guard and a standard chainring you can chuck them on any normal road crank which opens up the options a little as I found there are not a lot of choices when it comes to a SS road setup.

I bought a standard 130BCD - 175mm road crank and a 130BCD 42T Surly ring and matched it to a spot brand 42T sized ring guard and it works a treat. Salsa make a bigger 44T ring guard and Truvative also have a 52T version in 130BCD get one of these and match it to the chainring and crank of your choice.

If you wanted a 180mm crank you could look at a White Industries Eno SS crank with there 44T chainring.

Whisperer's picture

I'm riding/commuting on the road on my 26" hardtail SS with 43*16 gearing.
[ ]I'm 1.8m and 78kg. This is good for 26-28km/h average speed on my training rides, and is also good for distance of up to 100km with plenty of hills. i.e. 3 gorges etc. [ ]
I could go slightly higher gearing if the hills were not so steep, and that might suit you in Canberra.
Sounds like you need a road crankset to get the gearing you want. The challenge will be getting the crank arms to clear the chainstays, as they are wider than road frames. I've ended up using an old campag record crank, with a 'triple' bottom bracket to space it out far enough. A track crank will likely have the same issue.
I'll have a look in my parts stash to see if I've got a spare 48+t ring with that pcd you've got.

Supagav's picture

Well I might not of solved the your problems....... but I can help with the chain ring

These guys are sydney locals and they produce chainrings of all different sizes. I just checked there website and the make a 50T 94BCD chainring. Prices are about the same as buying any other chainring as well.

Good luck.

Morgan's picture

Looks like Cycleunderground will sort me out within my current crankset. I've got 14 gears in the Rohloff and I'm in Canberra so all I'm looking for is more big end gearing. If I do venture onto a hill somewhere the bike will still be geared at the small end lower than a roadie, so hopefully I'll have all ends of the spectrum covered.

Of course now all I need to work out is whether to keep my 210mm Zinn cranks on the 26" hardtail or put them back on the 29'er MTB they came on and return the 185mm's to the hardtail.

Longer cranks on an MTB or a roadie anyone?

Supagav's picture

Morgan go for the shorter cranks on the roadie. it will let you spin your legs a whole lot easier and it will make you faster.....

psd's picture

Hi Whisperer - where did you get the zion forks from? Do they come with mounts for v-brakes that would fit some old magura hydraulic rim brakes?

Whisperer's picture

Got them from JensonUSA, on special for USD $65!
Were only available with disk mounts at the time.
Jenson currently have surly forks for the same price with either canti or disk mounts.

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