detshiva

I have been running a 11/40 x8 with a old altus derailer it still works ok but starting to get a little sloppy.

When I bought the cassette I also bought a sunrace Shimano comparable deraier. The cage was heavier than the altus and it hit the spokes.

Can I get/make a .050 inch give or take shim to clear the spokes.

The bike is almost a 1x, main front is 34 oval in the middle position. But I use a fraction shifter to drop onto a 22t and I can use the biggest 3 or 4 gears before the chain starts flop shifting.

I am an old man trying to deal with Arizona grades

Thanks
Tony

Bill Kapaun

I'd get a better RDER.

dsbrantjr

I agree but if you insist there are 1mm and 1.8mm and possibly other spacers available, but if you space the cassette too far out you run the risk of not engaging enough of the lockring threads into the freehub and having one or the other threads strip.

ThermionicScott 

If you haven't already, consider taking the bike into a shop to make sure the rear derailleur hanger isn't bent inward. 8-speed and lower are forgiving enough that they can still index successfully with a slightly bent hanger.

*Scuba 

A properly set up rear derailleur, should never be able to contact the spokes. I would check to see if the RD hanger on the bike is bent. If the hanger is straight, then most likely the replacement derailleur itself is bent/damaged.

Bill Kapaun

I didn't insist ANYTHING. Where did you get that assumption? It really pisses me off when people misquote me or try to put words in my mouth.

Apparently you would rather band aid a kludge than fix it right?
OP stated-"I have been running a 11/40 x8 with a old altus derailer it still works ok but starting to get a little sloppy...."

ThermionicScott 

The wording is nebulous, but I assume he meant the OP insisting on using a shim.

Bill Kapaun

Then he should quote the OP.

OneIsAllYouNeed

Switch to an 11-42 or 11-46 cassette to get more clearance between the spokes and derailleur. Consider dishing the rim a little bit left.

Wilfred Laurier

Bad advice. The dish should be kept so that the rim is centred between the axle locknuts, otherwise you are throwing off the balance of the bike. You would be solving one problem by creating another.

The best suggestion so far is to get a derailleur with a less bulky cage, if that is indeed the reason for the derailleur hitting the spokes. Check hanger alignment before changing anything, though.

Retro Grouch 

That's what I was thinking too. It doesn't take much to bend the derailleur hanger inward. A bike old enough to have worn out a rear derailleur is almost sure to have taken a hit sufficient to bend the hanger inward.

Whenever I encounter ANY rear shifting issue that I can't fix by adjusting cable tension the first thing that I do is to check hanger alignment. Most times, that's it.

hokiefyd 

Hi, Tony. This is a bit of a red flag for me. The weight of the derailleur cage should not influence whether or not the cage can come into contact with the spokes. It sounds like your derailleur is not setup properly, including correct use of the low and high limit screws.

Park Tool has a very nice resource on derailleur adjustment that should help you out.

https://www.parktool.com/blog/repair...eur-adjustment

Wilfred Laurier

I understood 'heavier' to mean 'thicker', and OP thought the added thickness was enough to cause the interference.

hokiefyd 

Good point. I still suspect that the derailer is not be adjusted correctly. A Sunrace derailer would be commonly installed on bikes with 28-34 tooth large sprockets. OP has a 40 tooth large, which places the derailer even further from the hub (radially) when on the large sprocket, where the spokes are even further inboard (due to their angle from the hub to the rim). I can't imagine a setup where a properly-adjusted derailer would contact the spokes.

It certainly is possible to space the cassette outboard, using any number of 1mm shims. You can usually source these at your local bike shop for little coin (literally!). What model derailer is this, specifically? It will probably have a part number somewhere, perhaps on the inner link arm.

Wilfred Laurier

I and others have suggested it is likely an issue of derailleur hanger alignment, or other adjustment. Adding shims and pushing the cassette outboard would not be my desired course of action as this will lessen the number of threads engaged on the cassette lock ring and could lead to damage to the ring or (less likely) the cassette body... those lock rings need to be horsed on there good 'n' tight, so I would not think it to be a good idea to reduce thread engagement.

detshiva

It was all new except the derailleur when installed. There is also an extinction to make the bigger cog work. 34 40 makes for a long chain that's giving me problems.

A small shim moved the cassette a lot, but the long csge derailleur is just too big. although the shim aligned the front and rear sprockets bettet and I can use more cogs on the small ring

someone said the bike needs a better rider, maybe so. Im 62 years old and have 6 to 12 percent grades on the road plus a 15% driveway once and a while.

Riding is better than pushing
thanks for all the suggestions

ThermionicScott 

Just because the bike and/or hanger are new doesn't mean they can't be bent slightly. I'd still take it to a shop to rule that out.