Redbullet

I am trying to upgrade a cheap road bike with mixed mechanics for trainer use, in order to obtain a smoother shifting progression. I am wondering whether the changes below will work (as far as I know, everything is Shimano compatible):

Actual:
Crank set: Pro wheel triple, with Shimano Claris derailleur
Rear derailleur: Microshift 8 speed
Chain: Shimano 8 speed
Right shifter: Shimano Claris (8 speed)
Cassette: Sun Race 8 speed, 11-25

Upgraded:
Crank set: No change, Pro wheel triple, with Shimano Claris derailleur
Rear derailleur: No change, Microshift 8 speed
Chain: No change, Shimano 8 speed
Right shifter: New, Shimano Sora ST-R3000 STI, 9 speed
Cassette: New, Shimano CS-HG50-9, 9 speed, 12-25

So, will this upgrade work?

bboy314

Should work fine, use a 9 speed chain too.

Crankycrank

+1 ^^^^^. The SORA 9 sp shifter has the same pull ratio of 1.7 as the Microshift 8 sp rear derailleur.

delbiker1 

Absolutely, chain is cheap and shifting will be much better.

Kontact

I would just go to a closer ratio cassette to get a better progression (12-23). Are you actually using your lowest gears on the trainer?

rm -rf

I, too, am not sure of your question. Is it:

1. closer shifts, with smaller speed changes for the same cadence?
Do you want to change the slower small chainring speeds, or the faster big chainring speeds? For my road bike, I looked for closer shifts at fast-for-me speeds. Climbing could tolerate larger cadence jumps.
or
2. smoother, faster shifting performance?

~~~
Are you sure it's a Sunrace 11-25 8 speed? That seems to be unusual when I searched for cassettes online.

icemilkcoffee 

That R3000 right brifter will shift the 9 speed cassette perfectly fine. Just keep in mind that the R3000 brifter , although very similar in appearance as your current R2000 8 speed Claris brifter, is black in color. Your Claris is dark grey. Depending on your level of OCDness it might drive you nuts to see mismatched color brifters in front of you like that.

Redbullet

Very rarely the smallest cog with big ring on descents, but I use the next ones, especially with the middle ring. I think that 25 would still be of use while climbing. Besides, 12-23 was only available from SRAM and I did not want to make a full mix.
By the way, do you know how how CS-HG50-9 cassette is built? Does it have independent cogs, or is there a block of a few cogs? If independent, i assume that one could play later by mixing cogs from other Shimano cassette?

Redbullet

I am looking for smoother steps around the speed of 28-32+ km/h (or 30-34+ km/h on trainer, since many apps show a little bigger speed than you expect in real life).
I have just noticed that Sun Race does not have 8 speed 11-25 on website (at least not now). Maybe they had in the past, or maybe my cassette is also a mix - it looks very similar with Shimano.

Redbullet

Sure, I won't do that on my road bikes. But this is a bike used only on trainer, thus, the objective is to have it fully functional and comfortable and as low cost as possible.

Kontact

So why not just a closer ratio 8 cassette?

veganbikes

I wouldn't put much money towards a claris equipped bike if it is functional I would just ride it especially if it is on trainer duty the only thing I would do is keep the bike clean and replace wear items as needed because they are worn. If you need something different gearing wise I would consider a closer range cassette.

If you are deadset on throwing money away make sure to also get a 9 speed chain as well however again I wouldn't put much towards the bike.

In the case of the things like Claris and Tourney just save the money and put it towards the bike you want and keep this one safely functional without spending too much on it. If you keep it well maintained it will last longer.

Redbullet

The actual 8s cassette is built from 11 to 25 with 2 teeth constant increment. I can’t find another optimal 8s cassette to assure an interval of 1 tooth and to preserve 25t for some climbing. I found that 9s 12-25 would give an interval of 1 tooth: 12-13-14-15, at the expense of 87 EUR and dismissal of actual 11 teeth which is rarely used. Plus 16 EUR for new chain (which should be anyway changed soon).

It would be interesting to know whether I can play with mixing any cog with (let’s say) 14-25 Shimano, for an even larger 1 tooth interval (and removing 25t), but this is just for curiosity, since further investment would be “overkill”.

Kontact

Here's 12-25 9 speed Shimano HG-50:
12-13-14-15-17-19-21-23-25T
Shimano 8 speed HG-50:
12-13-14-15-17-19-21-23
12-13-15-17-19-21-23-25
13-14-15-17-19-21-23-26

All of these are like $20. Are you sure you really need to change your shifter to get gears for the trainer? The 13-26 seems like the perfect solution.

Russ Roth

You'll never notice the difference with a sram 9sp cassette, the spacing is the same and they work perfectly together. Just do the 9sp chain.

rm -rf

What are the tooth counts for the three triple rings?

The rings determine what speed ranges are usable for each chainring. And for your typical cadence.

~~~

For example, here's a Shimano 8 speed 12-21 with a 30, 39, 52 triple. And flat road spinning cadences, mid 80s to 90s rpm.

Mike Sherman's gear calculator link for this setup. Big chainring in blue, middle in black, small in red.

8 speed 12-21. The yellow highlight is at your target speed range for closer shifts. That's approx 17 to 22 mph -- right where I also want close shifts.
But you can't go much faster in the middle ring without a front shift, or much slower in the big ring without a front shift.


~~~~~~~~~~~~

8 speed 13-26. This works pretty good for the 39 middle ring, but it can't go much faster without a shift to the big ring. Those speeds are right in the middle of the big ring, but the speed jumps per shift are larger.

Redbullet

Thanks.
I played with the chart. 13-26 looks good for the speed range but has 2 drawbacks. One is the max speed: the crank set is 50/39/30 and the max. speed with 13t at 92 cadence would be 44km/h (too small for the trainer, where speeds are a little bigger than real life). The second is that the middle ring would be used long time with the smallest cog and with no much reserve for a short burst.
The 9 speed 12-25 seems to solve both topics.

Redbullet

Thanks. I have just played with the chart; it looks that 13t would not give a good maximum speed on the trainer, since the large ring is only 50. Switching from 11t to 12t smallest cog would be more appropriate than from 11t to 13t.