riderx

I wouldn't let that "mechanic" work on my bike. Just my $.02

Tomo_Ishi

Hey,

Thanks, riderx. I see people on the net with disk-cogs, but I have never seen someone riding disk-cog-fixie with my bare eyes. I just need to hear from some who has ridden one.

Anymore, one cents? I don't mind 6e-23 cents even.

T

thequickfix

I have only put a couple of miles on my tomicog, but it seems just fine. I don't see how you could strip anything if you install it well. As long as you have proper disc bolts and torque them down nice and tight, it should be good. In principle, it seems to me like the bolt-on cog is not much different from a chainring.

mihlbach

I wouldn't worry about it. The torque exerted by a bolt-on cog is much smaller than the torque that a disk brake can exert on the hub. To make the point, you can't even come close to accelerating or decelerating with a FG drive train at the same rate that front disk brake is capable of decelerating.
I've now got hundreds of hard offroad miles on my tomicog,, with no sign of the bolts loosening.

TheBrick

I have a londonfixiebike bolt on rear cog on my single speed / fixed mbt. I run it with brakes off road and also use the same bike for polo and run it brakeless for trick fun when not palying polo. The cog is very high quality in person and has worked flawlessly. It's nice and round so no big issues with changing chain tension. Chainline issues don'e exists for this set up, just tweak with washers. I am using a 135 mm on one single speed disk hub, it's identical to the DMR single speed disk hub but cheaper, same factory I bet. I would buy one of these cogs again and would also use it on a road bike with one of the front hubs on the back with the axel replaced.

londonfixiebike

Regarding bolts we advise to use hardened steel hex bolts as the best option. Regular hardwear store bolts are a definite no-no. Not sure of the Yen rate but GR12.9 bolts are under £2 for a set of six in the UK and will last for ever. Make sure you have 7-8mm minimum in the hub securing the cog (use 10mm bolts for 3/32", 12mm for 1/8") grease the bolts and tighten them up as per the FAQ.

Tomo_Ishi

Hey,

Thanks for your responses. I am feeling guilty about overriding the thread, but I felt it is important.

I would like to take this opportunity to ask another question. I have a cog here and analyzing its material and it is quite solid. I have 15mm steel BOLTS now. But there is some play in the BOLT holes of a cog. Should I get bushings to fill that space?

T

P.S. Thanks Brick for pointing out the difference between screws and bolts.

TheBrick

Fist important thing to do is use bolts not screws. Screws will not work.

Iser@n

Just tighten the bolts and there won't be any play. My Londonfixiebike cog didn't have play round the bolts, but I'm not sure, because its on my bike for a few months now. My old homemade cog did, and it worked fine.
And...... Dare I say it? The Londonfixiecog (can't speak for the tomicog) feels more secure than a normal track cog. No slipping cog, no chain line issues, it's durable and just works. Using some loctite with the bolts will make it sure you won't loose any bolts, but I don't think it is necessary.

vobopl

Yes, it is more secure.
1) theory: Unlike traditional thread on + lockring one, ISO 6 bolt interface is NOT being fastened in the direction of applied torque so the bolts have only shearing load on them.
2) practice: disc brakes were designed for exerting much higher torques than any rider ever will.

Tomo_Ishi

Hey,

I will try it out over the weekend. I am grateful, you guys.

I am sitting here with two shiny new TomiCogs tempting me to skip work and all. Heehee.

T

londonfixiebike

Hi,

I cannot speak for other disc mount cogs but are ours are engineered to have very tight tolerances and made from materials highly suited to long life and stength (ie heat-treated chro-moly).

It is unusual to mount sprockets in this way (without a central locating bore) so it is hugely important that when these style of bolt on cogs are engineered that:

a) the teeth are absolutely concentric to the ring of 6 mounting bolts (and less importantly the central bore - as it only needs to clear the hub not locate on it).

b) the mounting holes are drilled to very tight tolerances (ie closer than is possible with a regular home 5mm drill).

This is all to avoid run-out (tight/loose spots in the chain) and that there is virtually zero slopiness in the 6 mounting holes.

Some small run out is still possible (perhaps inevitable) - on a disc this does not matter of course as the disc has freedom of movement within the pads in the caliper.

Tomo_Ishi

Hey,

Thanks ya'l. Look at my new fixie eno hub ... sorta.



T

evan_phi

do want!

mike29er

I know what your saying. What do you mean Brett is building chain-ring and cogs again. I've been to Brett shop and bugging the crap out of him. Well it worked and he just started filling back orders from the last year or so.
Now I've worked out a deal with him to sell them, so he can continue to build them.
Email me if you are interested.
Mike
mike@singleandfixed.com
www.singleandfixed.com