Sunrace Indexed R30 7 Speed Downtube Shifters

[SRV]

I've recently fitted these shifters. The lhs friction shifter is fine. On the rhs if I go up the gears the change is smooth and accurate.
However, on changing down, the shifter overshifts before clicking and then settles back in the selected gear. This overshift is annoying as it often engages the next gear down before settling back with a clunk and a jerk. I often lose precious momentum when this happens.
Have I set it up wrong? If not, is there a way of reducing, or even eliminating the backlash in order to minimise the problem?
Thanks.

[Brucey]

in a lot of gearing systems a little overshift on downshifts is no bad thing; it can 'help out' with rear mechs and sprockets/chains that don't want to shift well.

However if you have good RD/sprockets/chain that shift promptly then overshift is undesirable. It might be possible to wind the b tension screw in on some RDs (which normally makes the shift 'worse' I.e. less prompt) but this might be an overall improvement here.



I've not used those particular levers myself but the internals are I believe virtually identically constructed to lots of other sun race levers, so

a) maybe they are not fitted correctly? The levers look the same but the LH screw can't be fully tight because it adjusts a one-way friction clutch and the RH one doesn't. The RH mounting screw is meant to be tight (tighter than the LH screw), and if it isn't the whole lever assembly can flap about which increases overshift on downshifts only, much as you describe.

b) other sunrace index levers not only have backlash (which gets worse with time) but it can also be sticky backlash, i.e. springs pulling the gear cable may not cause the lever to return to the detent position following a downshift.

If b) there are two solutions; one is to refangle the lever internals (difficult and fiddly) the other is to learn to live with it, by pushing the lever forwards into the detent position following each downshift.

hth

cheers

[SRV]

Thanks Brucey. Enlightening as ever!
I have decided not to try and dismantle the shifter because it appears almost impossible to do non-destructively. By the way on the R30 tightening the rhs screw does make the detent action "stiffer". I've not yet tried winding in the b-screw. That'll be next. Maybe friction is the way to go, especially on a bike that is not used in traffic. At least I'll only have myself to blame if I can't change gear cleanly.

[Brucey]

I have decided not to try and dismantle the shifter because it appears almost impossible to do non-destructively. By the way on the R30 tightening the rhs screw does make the detent action "stiffer".....

yeah, but it probably shouldn't, and riding with it even slightly loose will, I strongly suspect, just make all kinds of backlash/wear worse, quite quickly.

My advice is to have the RH screw tight and the guts of the RH lever well lubricated; if the mechanism runs dry this causes terrible problems. Dismantling the lever is somewhat fiddly; not recommended if you are not well used to this sort of thing.

cheers

[SRV]

Thanks Brucey.
In the end I decided to give up on the Sunrace. Pity, because I quite like Sunrace kit. Anyway, I've bought a pair of secondhand Shimano SL-A400s from ebay. Smooth and precise; I'm happy now.

[Brucey]

FWIW in the last few days I bought a set of SunRace R80 8s band-on shifters, like these;



mainly to see what they are like inside. I dunno about the R30 shifters but the R80 ones are basically built on the same architecture as SunRace M90 thumbshifters/R90 bar end shifters and a wide variety of SunRace sturmey archer branded shifters for their IGHs. The similarities incudes the barrel diameter which means you can transplant the guts from different shifters about and the cable pull ought to stay the same when the same mechanism is inside a different lever body (*). The 'friction' shifter (microratchet) seems to work OK but the 8s index lever has the usual problems, the primary one being sticky backlash.

The good news is that you can make these shifters work well. The bad news it that it takes ages to do this; you need tools, skill, and the patience of a saint.

With these levers if they are internally set correctly the mounting screws may be set tight enough that the back plates don't (can't) move in use; there is still backlash but it is not sticky backlash, so there is some overshifting to help the shift along if it is a bit reluctant but once you let go of the lever go the mech pulls it against the detent and the indexing (in-gear alignment) is accurate. However if the guts of the shifter are set up badly (i.e. in the factory condition) there is sticky backlash even when the screw is loose enough that the backplate moves around in use (bad). In the as-received condition you would have to push the lever against the detent following every downshift if you wanted the in-gear alignment to be accurate, and unless the mounting screw is set pretty tight the back plate will be moving around, maybe enough to (briefly) downshift twice instead of once .

(*) Amongst other things this means I can make up band-on levers which will operate various SA IGHs, or an IGH and a FD, or an IGH and a RD.

Eventually.

cheers

[fatboy]

I gave up on these too, complete rubbish and I don't have patience!

Are there any new 7 speed shifters available? I like my 7 speed Shimano ones but they are eBay and obviously old (my guess is 90s) and the plastic cover has disintegrated on one!

[Brucey]

there don't seem to be any nice new 7s shifters out there right now.

One option which sounds a bit mad but actually has some benefits is to

a) use 8s shifters and
b) use a shortened 8s cassette (or a respaced 7s cassette, to match 8s spacing)

the possible benefits include that you get to have a cassette without the stupid small sprocket that you usually get whether you like it or not. Probably there is more choice overall in 8s cassettes too.

For example 11-32T 8s

https://www.sjscycles.co.uk/cassettes/1132-ventura-8-speed-cassette/

becomes 13-32T 7s(with 8s spacing) simply by chucking the nigh-on useless 11T sprocket in the bin. Less than £15 too.

cheers

[slowster]

Are there any new 7 speed shifters available?

I find that R400 8 speed levers work OK with 7 speed. I centered the indexing on the middle sprocket to minimise the effect of the difference in cable pull between 7 and 8 speed, and obviously one of the 8 index positions is redundant.

[Brucey]

using 8s shifters with a 7s cassette can work slightly better than it has any right to because of a subtle reason. This is that the cable pulls are not uniform; they get longer as the mech goes leftwards, and the RD goes further leftwards with 8s than 7s. This means that using positions 1-7 in an 8s shifter for 7s results in smaller cumulative errors than you would otherwise get, because you are using cable pulls that are each slightly longer than they should be for that mech position (w.r.t. the RH dropout), especially on the LHS of the cassette. However in the smaller sprockets the cable pulls are more uniform and the 8s ones don't match 7s spacing so well.

If you want to get the shifting as good as it can be with this setup, probably you need only respace a few of the smaller sprockets to get it to match almost perfectly.

If alternatively you use 8s shifters with a shortened 8s cassette, it is probably better to use positions 2-8 in the shifter since they will match the sprockets perfectly, because the mech position and the index position in the shifter coincide as they are intended to.

IMHO you should shoot for perfection, and if you know you can't get that exactly, try stuff out and see what works best for you; actually what works well enough is often in the eye of the beholder, or in this case the hand of the gear changer.

cheers

[fatboy]

there don't seem to be any nice new 7s shifters out there right now. <SNIP>

I've always assumed that the weird small sprocket was necessary to lock as they've a bit notched. Interested about the possibility of ditching the 11s which I never use!

[Brucey]

if you look at a lot of cassettes, you will find that quite a few have serrations on the second smallest sprocket too, which means that they also can work in the final position, provided a suitable (often larger) lockring, or spacer/threadlock is used. However because the splines don't extend to the end of the freehub body (HG-C type or later), and the 8s cassette has closer spacing than the 7s one, it is necessary for the second smallest sprocket to have a built-in spacer, with splines etc if you want to use it in the rightmost position. You will have to check whether the cassette you intend to buy is like this or not; not all are.

Lack of serrations on the final sprocket is no big deal; threadlock can sort that out. However it is essential that the sprocket you intend to use as the final one has an integral splined spacer; there is no easy way of getting away from that one.

cheers

[Brucey]

7 sprockets from an 8s cassette on a 7s freehub body

in the photo above you can see how a 11-28T 8s cassette can be shortened to become a 12-28T 7s cassette. A standard lockring of an appropriate size, and a drop of threadlock will secure the cassette, even though there are no serrations on the end sprocket.

cheers