SRAM Omnium crankset

tester - can i use a spacer on the cranks?

it this wise?

I wouldn't use a spacer on a GXP crank, there's a danger that the NDS crank would not be properly secured or worse the bearing preload would be excessive. Shimano Hollowtech uses a different preload/end float mechanism, which is why you might get away with it there.

If you want to space the chainline of Omniums out, the ugly but workable solution is shims between the chainring and spider.

rather what i thought

I did try putting the sprocket on the goldtecs back to front, but the chain was then up against the spokes

so time for a new hub?

Why not spacers under the chainring? If there's room behind the crank to move the chain out 2mm, that seems like the cheap and quick solution.

I haz some 2mm thick one laying around, might need longer nuts too.

Fairy nuff, wasn't aware the preload thing was different.

I have checked the Sram Omnium chain line it's 41mm. So I'm going to space out the drive side of the crank by 2mm. That gives me 43mm, to use with the Goldtec hub spacing of 42.5mm. That all should work very well...thanks again!

seriously does 3mm matter that much, If you look at the transmission database and the mish mash of chainline hub crank combinations, I can't think that 3mm over 300mm can actually have a significant effect

I'm going to space out the drive side of the crank by 2mm

If you're thinking of putting a 2mm spacer under the driveside BB cup, you're a braver man than I.

I can't think that 3mm over 300mm can actually have a significant effect

3mm error is chainline can be accommodated by ⅛" chains, but very noisily and with considerable unnecessary friction.

I have checked the Sram Omnium chain line it's 41mm. So I'm going to space out the drive side of the crank by 2mm. That gives me 43mm, to use with the Goldtec hub spacing of 42.5mm. That all should work very well...thanks again!

If you're thinking of putting a 2mm spacer under the driveside BB cup, you're a braver man than I.

On GPX BBs, crank position is defined by the non drive side bearings, so you really need a 1.5mm negative shim there (i.e. a lot of work with a sharp facing tool). Once you've cut the BB shell down to 67.5mm, adding spacers to the drive side would be a cosmetic measure.

Actually, the first thing i'd do is get some vernier callipers and see exactly how long your BB shell is now, then put the BB cups onto the axle and see what length of BB shell they have space for.

Annoyingly, it appears the MTB version of GPX comes with spacers that could be moved around http://www.sram.com/sites/default/files/techdocs/95-6115-006-000_rev_e_mtb_cranksets.pdf but the road version doesn't http://www.sram.com/sites/default/files/techdocs/95-6115-007-000%20Rev%20A%20-%20Road%20Cranksets_3.pdf

I think this will be to help deal with chainsuck issues that are more prevalent on mountain bikes due to mud.

On GPX BBs, crank position is defined by the non drive side bearings, so you really need a 1.5mm negative shim there (i.e. a lot of work with a sharp facing tool). Once you've cut the BB shell down to 66.5mm, adding spacers to the drive side would be a cosmetic measure

Fixed dimension, but otherwise spot on.

Annoyingly, it appears the MTB version of GPX comes with spacers that could be moved around http://www.sram.com/sites/default/files/techdocs/95-6115-006-000_rev_e_mtb_cranksets.pdf but the road version doesn't http://www.sram.com/sites/default/files/techdocs/95-6115-007-000%20Rev%20A%20-%20Road%20Cranksets_3.pdf

Same with Shimano Hollowtech BBs. mtb have spacer and longer axle, road have short axle (which can still take a little spacing) and no spacer as stock.

The MTB kit has spacers because some MTB frames have 73mm BB shells. Cuts inventory in half if they make everything to fit the 73mm shell and then include 2 x 2.5mm spacers (cost <10c) to make it fit 68mm shells.

I had an MTB with a Truvativ Gigapipe BB, which lived up to its reputation and needed replacing more often than the tires needed inflating.

It came with the spacers mentioned above, which I used to correct the chainline on my Fuji Track Pro, which came with an FSA carbon crankset that was too close to the centreline:

The MTB kit has spacers because some MTB frames have 73mm BB shells. Cuts inventory in half if they make everything to fit the 73mm shell and then include 2 x 2.5mm spacers (cost <10c) to make it fit 68mm shells.

Isn't there something to do with bb mounted front mechs too, sure there's something that says spacers this way if normal mech, that way if bb mounted one.

I suppose the longer axle on the mtb ones pushes q factor up too but not really an issue on mtb whereas might be more of an issue on road bike.

I think there might be some different spacer arrangement for E-Type FDs (and in the olden days of 3-piece cranks and separate inventory for 68 and 73 BBs, there was a special BB to clamp the E-Type FD), but aren't they pretty much obsolete anyway? It's all about Direct Mount now.

The howitzer bb instructions had an extra drive side spacer that gets left out if you're using a BB mech mount. (I've had a fun afternoon of reading bb tech documents.)

I think there might be some different spacer arrangement for E-Type FDs (and in the olden days of 3-piece cranks and separate inventory for 68 and 73 BBs, there was a special BB to clamp the E-Type FD), but aren't they pretty much obsolete anyway? It's all about Direct Mount now.

Probably. Shimano seem to particularly enjoy busying themselves finding solutions to problems that never existed and reinventing the wheel every other week.

Morning...

I've reviewed the thread started by Jaycee and am still non the wiser about whether to go with Omniums or not...

In a nutshell, does anyone know if they will work with a miche hub (Fixed/free) fitted to a Dolan Pre Cursa without any shims / spacers etc...

Or should I just wait until the Miche Advanced Primato chainsets come back in stock...

Any thoughts?

Cheers

Have you looked through the transmissions database?
http://www.lfgss.com/thread3372.html

yep... none with a miche hub...

Miche hubs give 42mm chainline IIRC. Therefore the omniums should be fine.

Omniums foul the chainstay of some Dolans. Might be worth checking with TFG as they have fitted loads of these cranksets to various rames.

thanks for the advice butters... just gave TFG a call and they reckoned its all dependant on how thick the chain stays are on the frame... i guess its a case of buy and see!

You can use a spacer if it is a problem. Did this with a mates Dolan and he's been riding it around without issue for a little while now. You might have to space your cog the same if the chainline pisses you off.