Cassette and chain alignment? Is it really a problem?

[DMZ]

If running a 7 speed cassette on a 130mm hub in a 135mm frame, centrally positioned with spacers; is the chain offset really going to be that dramatic? Presumably the angle will change equally for deeper cassettes on certain gears....I ride mostly in the top gears anyway

...I am just wondering what the fuss is about regarding this, whilst contemplating getting a nice set of second hand good quality 700c wheels and just making them work.

If all fails I just sell them and admit defeat.

 

[foz]

I'm not sure what your question is... if the cassette or freewheel is more or less central, and the chainset is fitted to the correct length BB, then there shouldn't be any problems unless you have a strange frame with very short chainstays. With geared bikes, the chain runs at an angle most of the time, it's not a like a fixed gear or SS where chainline is more important (but even then it doesn't have to be dead straight)

 

[DMZ]

It's because when putting a 700c with a 130mm hub into a 135mm frame people seem to think you need to put the spacer on the non-geared side, and redish the wheel; or reset the frame, or other complicated things. As you said, the chain runs at an angle most of the time anyway; in fact on mine as it stands it would run straighter on the gears I use if it were a little further inboard.

It's my first time doing this so just getting my head around things..

 

[foz]

In that case the easiest thing to do is put a 2.5mm space on each side, then you shouldn't have to redish the wheel or mess around with anything. the sprockets will probably work just fine. If the frame is steel then you might be able to get away with less than 2.5mm each side, and bend in the rear dropouts a little bit. If it's anything other than steel, then it's best to set the rear OLN to exactly 135mm (or that of the frame if it's different). Make sure you check the rear mech limit screws, as it might be possible for the chain to drop off the smallest sprocket and get stuck between the sprocket and the dropout.

Fitting a single 5mm spacer to the non drive side will keep the sprockets in the same position relative to the driveside dropout, but will also move them further away from the original chainline, which is always measured from the centre line of the bike. The advantage of the single non drive side spacer is that the redished wheel will have less dish on each side, more equal spoke angle and tension than before, and should be stronger.

Either way, I don't think you'll have any problems with chainline.

 

[DMZ]

Thanks for that, really useful. Is redishing complicated/costly? Again, I've never done that before...

 

[heavyhighsierra]

Thanks for that, really useful. Is redishing complicated/costly? Again, I've never done that before...

you'll only have to re-dish the wheel if in doesn't mount straight in the rear triangle. i.e. the tire rubs on either of the chain stays when the wheel is mounted straight in the drop outs.

 

[foz]

redishing isn't complicated, but if you've never done it before you're probably better taking it to someone that has (and if they let you see how it's done then you'll know for next time!)

If the wheel is dished centrally (rim exactly in the centre between the locknuts) and the frame is straight, then adding the same spacers to each side should leave the wheel in the centre with no redishing required.

Most wheels should be dished with the rim in the centre, but if the frame it came out of was out of line, then there's a chance it was dished off-center to compensate. just try fitting it correctly and then the other way around (sprockets on the opposite side to the mech) and if it is centered in the frame both ways, then it's dished centrally.

 

[bm0p700f]

Dedishing a wheel sahould cost a little as a tenner. It should take less than 1/2 hour much less really if all the nipples turn freely. The complication is if the nipples are a siezed and round off. I tend to loosen old nipples first before tightening to see if siezing is going to an issue and then replace if it they don't move freely.