SRAM Omnium crankset

So, if I order some omnium cranks, and they end up fouling my yet to be acquired new frame, what are the chances that retailer would refund? I'm thinking slim.

Has anyone got any advice about width of chainstays at the point where they foul the frame? Could be useful to prospective omnium buyers.

I asked TFG whether I could return the cranks if they clashed with the frame and they said yes...

Has anyone got any advice about width of chainstays at the point where they foul the frame? Could be useful to prospective omnium buyers.

I'm running some on a Leader 722 and they are fine. I'll measure it later and see what sort of max width you might be able to get away with.

I'm running some on a Leader 722 and they are fine. I'll measure it later and see what sort of max width you might be able to get away with.

Cheers, that would be great.

I just got a set of Omniums fitted yesterday. They're really smooth and the chainline is perfect. Clearance is very tight on the drive side though. Got a new Italian threaded GXP bottom bracket which is seriously tight. Cycled home from E17 to Sydenham and it felt like riding uphill all the way.

Really don't fancy shelling out loads on a CK bb or opening up the seals and putting lower viscosity grease in there so I may just ditch the whole set up and go back to square taper and get a Miche Advanced crankset.

So annoying after looking forward to this upgrade for so long.

I have a Miche Primato double fixed hub by the way.

Arup - have you had your bottom bracket faced? If not then it's possible the cups aren't exactly lined up binding the cranks and causing the stiffness you are feeling. If it's set up properly you won't notice any stiffness at all, even though when you spin the cranks they may feel more laggy than a square taper.

If you want me to look at it for you feel free to pop into mine if you are still in bayswater way weekdays.

Thanks Howard. This crankset had been much anticipated so it's been quite a disappointing experience. I got them fitted at Racer Rosa in Walthamstow last night. We did actually consider facing the shell especially as the tools are all there but because there was such a tight clearance between the crank arm spider and chainstay (about 2mm) we thought that the paint layer might act as a shim. The frame itself had already been faced and our theory was that the powder coat layer wouldn't really make much of a difference. But perhaps it has.

Had a long conversation with Diego about it this morning considering lots of other alternatives and have planned to get them removed tomorrow morning and go for a Miche Advanced instead which he has in stock and square taper BB. I'm sure I can sell the Omnium with BB and cover some costs.

I guess I could try facing the shell but the clearance would then be even tighter and I wouldn't be able to relax while spinning fast down a hill. My heels were also coming into contact with the cranks this afternoon. Only brushing but still a little disconcerting. So all in a all a big thumbs down.

Face the BB shell and use a spacer?

What pifko said

Yeah that's what I was going to suggest. I wouldn't be surprised if the cups aren't aligned causing the binding and that the BB shell is slightly less than 68mm, binding the bearings further by over preloading when the crank arm is tightened down.

If it was my ride I'd check the width of the BB shell first, then if it is equal or less than 68mm without facing I'd face the shell and add a 2mm spacer on the drive side. You can use a 10 speed shimano cassette spacer if you don't have a BB spacer.

When set up correctly GPX cranks should spin well. You shouldn't notice any rotational lag.

Face the BB shell and use a spacer?

This man speaks sense

So you guys reckon I should face the shell and give it another go?

Yep, something is not right- as Howard says those cranks should spin freely.

That they are not suggests that something is binding- facing and spacing so you have a shell with perfectly parallel sides, and using a spacer to achieve the specified width should sort this, one would hope.

If not- time to return the BB and get a new one.

Got a new Italian threaded GXP bottom bracket

the BB shell is slightly less than 70mm, binding the bearings further by over preloading when the crank arm is tightened down

ftfy

Also, GXP cranks don't bind if the shell is under width, because assembly doesn't preload the bearings; end float is controlled by clamping the NDS bearing between the NDS crank and a ridge on the axle. However, if the shell is over width, the DS crank hits the DS bearing and creates bearing preload. Since the shell has a layer of powder coat on it, it seem that it is likely to be over width and therefore facing it will probably solve the tight bearing problem. Don't use any spacers, as this will just bring the problem right back. An under width shell is not a problem with GXP, it just means there is a bigger than standard clearance between the DS crank and bearing. Careful use of the facing tool, esp. on the DS, should not remove enough material to have a significant effect on chainstay clearance, but if it does then there is always the universal chainstay clearance adjustment tool:

Tester clearly has superior attention to detail and spacial reasoning skills than I. You'd think I'd get it right, too, having had the same issue as Arup. :(

Anyway - Arup the hammer in Tester's post above should give you an idea as to whether it's worth proceeding. If you really like the cranks, you may get them to play nice. But some cranks just don't play well with some frames; SRAM GXP cranks won't fit my airnimal - the arms foul the chainstays. You may be unlucky.

As they were only fitted last night I've only ridden about 3 (tough) hours on them. Aside from the tight BB the cranks themselves feel good and I get better control especially a sense of connection between the left and right foot. Seem to have more control going slowly and am able do tighter turns.

You can imagine that I've scouring the interwebs a whole lot today and there are more bad reports about the BB than good ones. The grease leaked out or crunching noises were heard within a month. Most posts and blogs talk about repacking the bearings with lighter grease and opening up the seals to do so. Then repeating the maintenance once a month or so. How come I didn't come across these results when I was researching the cranks? All I got then was SRAM Omnium vs Sugino 75. But I guess I was researching the cranks rather than the BB and my focus was there.

I'm prepared to service my BB no more than once a year if that. Fit and forget. So even if facing the shell does work I've already lost my faith in this set up. Tomorrow they're coming off.

I've got a good amount of clearance between the arms and the chainstays but only a tiny clearance between the spider and the chainstay which worries me. I know some people can live with that and even if it is tiny it is still clearance but I don't feel safe somehow, so for that reason I'm out.

Very soon there will be a set of SRAM Omnium cranks up for a grabs along with almost new BB.

Facing the NDS of the BB shell will increase the clearance between the spider and the DS chainstay. Of course, it will also reduce the clearance between NDS crank and chainstay but I'm guessing there's plenty of space there.

Also, FWIW, having the crank or spider hit the chainstay when the back of the frame bends under your awesome power isn't that big a deal unless you're deeply emotionally attached to every square mm of your paint. It will make a clicking noise, but it won't stop your cranks. I wouldn't downgrade to shitty square taper cranks when there's still the option of smacking the stay with a big hammer to keep it quiet.

As they were only fitted last night I've only ridden about 3 (tough) hours on them. Aside from the tight BB the cranks themselves feel good and I get better control especially a sense of connection between the left and right foot. Seem to have more control going slowly and am able do tighter turns.

You can imagine that I've scouring the interwebs a whole lot today and there are more bad reports about the BB than good ones. The grease leaked out or crunching noises were heard within a month. Most posts and blogs talk about repacking the bearings with lighter grease and opening up the seals to do so. Then repeating the maintenance once a month or so. How come I didn't come across these results when I was researching the cranks? All I got then was SRAM Omnium vs Sugino 75. But I guess I was researching the cranks rather than the BB and my focus was there.

I'm prepared to service my BB no more than once a year if that. Fit and forget. So even if facing the shell does work I've already lost my faith in this set up. Tomorrow they're coming off.

I've got a good amount of clearance between the arms and the chainstays but only a tiny clearance between the spider and the chainstay which worries me. I know some people can live with that and even if it is tiny it is still clearance but I don't feel safe somehow, so for that reason I'm out.

Very soon there will be a set of SRAM Omnium cranks up for a grabs along with almost new BB.

What colour and length? I'm interested.

They're silver and have a black 48T chainring. 170mm. About to head up to Walthamstow now. So they will be available from Racer Rosa. I have both BSA and Italian cups in terms of BB.

Swayed by all the pro GXP postings and nothing to support the case of the poor old square taper I spent a few hours having another go at this. Instead of facing my own shell and risking a bad result a spare frame (made by the same frame builder) with an Italian threaded shell was used. It was due for a new paint job anyway.

The shell was faced and we took out the BB from mine and put it in there. My wheels were also put onto it along with a set of bars and saddle to try it out. Result - much smoother than what I had experienced yesterday on my own bike but still not quite as smooth as the old Miche square taper that I had before.

I had limited time as I needed to cycle back to Sydenham so decided to give it a try on mine. We stripped the experiment bike and then my own shell was faced. That meant that now there was contact between the spider and the stay. With no Italian size BB spacer available we created a split ring using an English sized one. Plenty of grease and everything fitted perfectly.

Verdict - much smoother ride and the cranks do spin better than yesterday . . . but, there is still drag. That loose spinning that you can feel going down a hill just wasn't there. Perhaps they (the cups) need time to break in so I'll give it a few more days. But it doesn't feel like an upgrade. All very interesting research and learning though.

am i reading it correctly that you have put in a small spacer? in which case you are likely to have over compressed the external bb bearings when you tightened up the cranks

my omniums run perfectly

I do see, to remember my bb being a little tight when I first got them. Seems fine now 3 years later with the same bb....

I rule at bike maintenance.

I think I cleaned the chain once.

We did measure the width and check that with the spacer it wouldn't be too wide. It was 69.5mm including the spacer after facing just inside the Italian width.

Did yours run well from day one or did they require a break in period?

Seal drag will decrease slightly as the rubber wears out. Bearing friction can seem higher unloaded (i.e. on the workstand) if close clearance bearings are used, because the balls are compressed between the races. This is irrelevant under service loading as long as the applied load is enough to drop the preload on the 'loose' side of the bearing to zero or less. I expect what you claim to be feeling is entirely in your head.