Boardman Sram Rival Chainset problems

tofu21

Hi,

I picked up a Boardman Team road bike yesterday under cycle to work. It has got Rival throughout on the gears and chainset.

When on the small ring at the front and small at the back the chain catches on the large ring at the front. It's almost trying to shift up to the larger ring. It does this regardless of the front mech position.

I tried to put a 2mm bottom bracket spacer on the drive side and it did make a little difference but didn't eleiminate completely. I had a bit of a play about and I would need to put 4mm+ of spacers to stop it rubbing completely. This looks like too much to me and wouldn't leave much of the chainset axle sticking through to the non-drive side.

I'm reluctant to take it back to halfords as I'm sure they will balls it up....

Any ideas????

thanks
Simon

Weejie54

When you have your spacer fitted, what is it like on the big ring front and big ring rear?
Perhaps the bike is trying to tell you something. The amount of chain deflection on small ring front and small ring rear is probably not good for the chain.
It probably shouldn't rub though.
You can probably just about duplicate that gear ratio on the big chainring, so perhaps you should live with it.

sturmey

Small chainring to smallest rear sprocket is a combination that is never used- this is commonly known advice.
If you can ride without any issues in,say,the thiord smallest sprocket/small ring then there is no real issue here.
Waste of time taking it back to the shop.

desweller

You're running too much angle in your chainline. Bikes don't like it!

Looking at the spec on the Boardman webby, your cassette is a Shimano 12-25 and your chainset is a 50/34 compact. The top 6 gears on the 34 tooth chainring are overlapped by the bottom 5 gears on the 50 tooth chainring. So there's no need to run the top gear on the cassette on the 34 tooth chainring.

4kicks

Conventional wisdom, mostly from old farts, is cross chaining is indeed a no-no, but I do 10k a year racing, on a 3 year old SRAM rival and am normally too tired trying to keep up here to not cross chain. My set up works fine (or at least I dont have this problem!), but I have heard of a couple of people inserting a smallish washer inside the screw at the FR rear to widen the Rival FD cage a wee bit.

Before doing that, have you checked the chainrings are not a wee bit buckled? Sometimes if the new bike has taken a bang in transport they can be.

sturmey

Conventional wisdom, mostly from old farts, is cross chaining is indeed a no-no, but I do 10k a year racing, on a 3 year old SRAM rival and am normally too tired trying to keep up here to not cross chain. My set up works fine (or at least I dont have this problem!), but I have heard of a couple of people inserting a smallish washer inside the screw at the FR rear to widen the Rival FD cage a wee bit

'cept the Boardman doesn't have a Rival chainset.
It's a Sram s350.Not the same.

tofu21

I've manually actioned the front mech, by pulling the cable, and the it's not the front mech that's the problem. Without the front mech in the way the chain still catches the big ring.

I know that you can get the same gear ratio by using the bigger ring but there are some times when it's not really worth changing up to the big ring.

It's funny that in the MTB world Sram have XX which they say has been designed to run all gear ratios across both chain rings but they can't do the same on their road groupsets....

tofu21

'cept the Boardman doesn't have a Rival chainset.
It's a Sram s350.Not the same.

Does it make any difference that it's not the Rival chainset?

cougie

Agree with most of the others - you shouldnt use the gears like that. I'd not be messing round with washers either.

Get a decent book on cycling and read up perhaps ?

http://www.amazon.co.uk/Richards-21st-C ... 401&sr=1-1

An earlier version of this was my favourite book ever as a schoolie - lots of useful info thats kept me safe on the road to this day.

desweller

tofu21 wrote:

I've manually actioned the front mech, by pulling the cable, and the it's not the front mech that's the problem. Without the front mech in the way the chain still catches the big ring.

I know that you can get the same gear ratio by using the bigger ring but there are some times when it's not really worth changing up to the big ring.

It's funny that in the MTB world Sram have XX which they say has been designed to run all gear ratios across both chain rings but they can't do the same on their road groupsets....

Perhaps the SRAM XX gruppo is designed to be used with longer chainstays.

Anyway, you're not using the gearing correctly. You could be four or five sprockets down if you'd shift onto the big ring. The design of the system assumes basic operator competence. It's like complaining that you can't change gear in your car without using the clutch when some other cars have automatic gearboxes.

cooper.michael1

This happens with all chainsets of all brands, perfectly normal.... as others say it is not really a gear which you should use regularly.

SPOKEDOCTOR

Hi Si
I have also had this problem with a lot of chainsets that are holowtec type. You are ok to use spacers with these chain sets if you have pinch bolt type, (use on drive side), if they are the type that fix with the action of one allen key (like a lot of the more expensive fsa and sram types) you will be limited to a spacer of about 2mm.

But there is another way.........If you look at your inner ring from the plan view above you will notice it has been machined so the teeth on the inner face has a larger lip. If you flip your inner ring (so the inner face now faces out) and refit it to your chainset you will now have a 1mm adjusted chain line and will alliviate chain rub on your outer ring.

This works on 10 and 9 speed chainsets.

Please note according to a lot of manufacturers user guides all gear ratios are possible!

The only gear combinations I would steer clear of is (big chain ring and top two low sprockets) as you can damage your chain due to the angle of chain line.

Good luck!

sturmey

The only gear combinations I would steer clear of is (big chain ring and top two low sprockets) as you can damage your chain due to the angle of chain line.

Eh?
So, you're saying it's ok to cross chain from small chainring to smallest sprocket but not the other way round?
Never heard that before. can you explain this?

rake

the gxp bottom bearing drive side is floating on this crankset, putting a spacer behind the drive side cup will do nothing at all to the chainline. the only way to move the chainset out to right side is to remove a spacer from the left bearing cup provided there is one fitted. if not then it cant be moved in this direction. it simply cant be designed to run that chain angle effectively without making something else worse.

tofu21

Looks like I've opened a can of worms hear!!!

Thanks for all the advice and idea.

Seems a bit strange to me that they develop 10 speed blocks that you can only use 7 or 8 out of the 10 without putting the chain at an unacceptable angle. I would have thought that they could develop a 8 speed block that can be mounted centrally and all used by both rings. The ring size could be played with to get the same ratios....

But hay, I'm just a hairy assed mountain biker

Weejie54

It's supposed to be about close ratios. Not quite the same requirements as off-road or touring.

keef66

I suspect this has only become a problem with compact groupsets (big difference between chainrings) and compact frames (short chainstays)

Worst case will be on the smallest frame sizes.

I have a 10sp triple and can use all 30 gear combinations if I so desire, without any rubbing on front mech or chainrings

John.T

Most compact chainsets will rub on small/small, some on the next cog also. It varies with different chainsets as the spacing between the rings is not always the same. My Stronglight 52/38 on Ultegra compact cranks rubs but the 50/34 shimano rings on the same cranks did not. It is not really a problem as the same gear is available elsewhere.

nickwill

keef66 wrote:

I suspect this has only become a problem with compact groupsets (big difference between chainrings) and compact frames (short chainstays)

Worst case will be on the smallest frame sizes.

I have a 10sp triple and can use all 30 gear combinations if I so desire, without any rubbing on front mech or chainrings

Its just an unwritten rule thay you shouldn't use small to small. If you make adaptations so you can, you will cause problems elsewhere. Very few setups will happily allow that option, and if they do, you will have very rapid chain wear.

Mister W

It's a common problem with compact chainsets. I have 105 on one bike and FSA on another and both of them do it. The chain rubs on the large chainring as it crosses from the small chainring to the small cogs. It's less likely to happen on standard doubles because the chainrings are closer in size. It's also less likely to happen on a triple because the smallest and largest chainrings aren't so close together (what with having another ring between them!).

Be careful of taking the advice to turn your inner chain ring around to increase the gap between the two rings. If the gap is too large the chain can drop between the rings when shifting.

nicklouse

tofu21 wrote:

It's funny that in the MTB world Sram have XX which they say has been designed to run all gear ratios across both chain rings but they can't do the same on their road groupsets....

not at all. the chain rings are not the same size and the chain angles are different.

one has contact and one does not.