Can I use part of a 10 speed cassette on a 7 speed hub and friction shift?
 

I'm having another crazy idea and I have been talked out of several of them by the very knowledgeable people on this site, I want to drop my front derailleur on my vintage road bike and make a retro friction 1x. I will use a sachs 3x7 internally geared with with a 34t chainring. This should result in the following gear chart:


https://cimg8.ibsrv.net/gimg/bikefor...a296628f78.png




Now I want to shift friction on the rear and I want as many gears as possible to fit onto the 7 speed hub so I am going to try a tiagra 11-25 10 speed cassette, drop the 11 & 12 t cogs add a 2.5 mm spacer behind the shortened cassette. I would like to use a suntour cyclone short cage rear derailleur like this one:

https://www.disraeligears.co.uk/site...1st_style.html

This shortened cassette and backing spacer should be within the 31mm stroke of the rear derailleur. The IGH will be shifted by a friction barcon and the rear will be shifted by a friction DT shifter. The question is will a 10 speed chain be usable with this rear derailleur or will the pulleys be incompatible with the narrow chain? In addition, I know the largest sproket on the 10 speed cassette is dished and I need to offset this as well to make sure the entire cassette is within the 31 mm stroke of the rear derailleur. Does anyone know the depth of the dishing?

Three comments-

Assuming the der has enough stroke length to cover the reduced cassette one question I would have is about the ability to trim the rear lever after a shift, to eliminate and adjacent cog/chain rub. 10 speed cogs are really close together which increases the chance of a rub and reduces the window of clean chain run.

Using a bar end lever might prove to add to the above concerns. Most bar end levers have a pretty large cable spool, the lever's travel is only about 110* (or so) and not the close to 180* that a down tube lever has. The large spool will make the trimming after a shift more challenging.

Using a friction lever for the IGH 3 speed can be also an issue if the hub's internals are not in the proper relationships during hard pedaling. Increased wear and possible gear slippage can result. This is why long before the industry even had ders the IGH shift levers were pretty much all indexed. IIRC at one time SRAM offered a 3 speed bar end lever. Also IIRC the Sachs 3x7 IGH cable pull amounts were compatible with Shimano road triple STI shifters. So if you can find a Shimano compatible and indexed bar end you should be good. Bike Friday's solution with dropped bars was to use Shimano STI levers. Andy


Ok a fourth comment- I hope you find the IGH aspect of your system to be to your liking. I find most all IGHs to have more internal friction losses than I like. The old SA AWs and Sachs Torpedo Boys when used in their 2nd gears were not too bad in this respect (their middle gears are a direct drive with no ratio increase or reduction). All the more modern IGHs that I have worked on seem to have more friction even in their direct drives. I just got rid of my SA RX-RK5 hub for these reasons and have gone back to a der system on my neighborhood bike.

I'm planning on a dt shifter for the rear. The barcon is for the IGH.

I am choosing the sachs 3x7 because it is supposed to be the most efficient in direct drive, has a pull chain that is compatible with sti's, and it is supposed to be easier to service than the SA cs-rf3. I have another 3x7 on my recumbent and I have been shifting with a sram twist shifter and I haven't had too many mis-shifts. Given the gear chart, this bike will spend 90% of its time in direct drive.

Why not just go with Shimano RD's and 10 speed downtube (or wherever) indexed shifter? What's the point of using some antique Suntour derailleur and friction shifting?

I already have the vintage derailleur and don't have 10 speed downtube shifters so I might as well try to see what friction shifting would be like on a modern drive train.

What is the thinking on this? is this because it is a cool thing to try? Is there a benefit you want to get?

this does not really seem simpler (one ring up front, 7 in back x 3 with igh) than just having a 3 x 7

curious minds want to know :)

I have done 1x8 with a thumbie and it is nice,

I have seen mixed result reported once you get into 9,10,11 speeds

The current set up is a 2x8, with index downtube for the rear and a friction barcon for the front. It used to be a manual shift on the front, no front derailleur which I decided was annoying. So I tried a front derailleur but due to the oddities of the frame (braze-on fd mount and flaired seat tube) combined with small big ring (44t) mean the front shifting sucks and I am forced to trim the front derailleur constantly which is also annoying. So I'm trying something else. I also wanted to try friction on the rear just on a whim and to test out a claim by the pathlesspedaled guy that friction works better with really narrow cassette spacing. The nice thing is I don't have to replace the brake levers and remove bar tape for this experiment. When I go to shimergo or gevenalle, I'm going to have to replace the bar tape.

That's a lot of work and expense to test a thoroughly specious claim. Just to avoid taping a handlebar?

I really hate wrapping bars...and specious claim or not it at least fixes my front derailleur issues.

Buena sera.

it sounds like your have a bike designed for a more classic front combo 52/42 or even compact 50/34 and there is not enough adjustment to allow use of a much smaller chain ring than originally designed for.
Maybe a better approach would be something that lets you lower the front derailler, instead of the the IGH route (note i have never used one, but from searching)
https://wickwerks.com/products/fit-link-adapter/
https://www.interlocracing.com/shop/...per-4421#attr=

or it could be that you are just to out of spec from what the frame supports design wise

Those are a good idea and I appreciate your input but I want to try my version of a 1x drive train. I have some experience with the IGH as I use one on my recumbent with 20" wheels where it is a no brainer to replace a front derailleur because of the step up gear and the ability to shift while stopped. In this case the advantages are less so, namely a way to aesthetically get around a frame designed for a large chainring and the ability to get a 1x range but have close gear spacing. Whether I go friction or 10 speed on the rear is a separate issue which I am virtually test running in this thread since you enthusiasts are good at pointing out potential issues.

Super, let us know how it works out. Also in case you missed it, I have done 8 speed friction (with modern cassette with ramps and such) and it works very nicely,

....this has been my experience as well, and in fact, I have more trouble friction shifting a Suntour ultra 6 freewheel, than I do the same bike with a regular 5 cog freewheel. I can do it, it's just more troublesome and fidgety.

.
...I'm probably missing some factor, but what's the reason you are using a partial 10 speed cassette, rather than just ordering up a 7 speed from some manufacturer like Sun Race ? Or if you need to save space where it mounts, an 8 speed cassette with one cog dropped ?

I have seen several instances of people claiming that modern 10+ speed drive trains are actually easier to shift. I have also seen people saying "don't go more than 7". So I've got a 7 speed hub and want to try it for myself and see what is up. I suspect that it is a multifactor situation with stuff like shifter gain ratio, shifter stroke, shifter ratcheting, cassette shift assist structures, cog spacing, chain width, derailleur gain, derailleur pulley slop that effect it. I got old derailleur with high gain and a tight guide pulley and I have a shimano sis derailleur with medium gain and a centeron pulley and I could explore a lot of these factors by acquiring a cassette and chain. In addition my old derailleur only has 31mm stroke so it can't quite shift a 7 speed cassette but it could shift 7 of 8, 8 of 10 or 9 of 11.

Just another data point (or is it an opinion?): I have two friction shifted (Sunrace SLM10's) 9 speed drivetrains and there are no shifting problems. I can't see 10 speed being an issue.

thinking about this "works well" for friction can be very subjective.

so to clarify in my case; I used to have a 1x8 set up with sram cassette and a cheapie thumb shifter, shifting was fast and responsive, but it easy easy to over or under shift with ramped cogs (more so than with classic 5 and 6 speed) and in that case the "friction mentality" of ok just adjust or trim applies.

I use friction for the first 30 years I had bikes so that is no big deal.

but if expectation is that friction will provide crisp index like shifting, that has not been my experience

Thanks for this. Here are some other data points I have collected from the interwebs:

https://www.bikeforums.net/classic-v...eat-combo.html

https://www.bikeforums.net/classic-v...9-10-11-a.html

https://www.bikeforums.net/classic-v...-shifting.html

https://www.bikeforums.net/classic-v...ampagnolo.html

https://old.******.com/r/bikewrench/..._with_11speed/

https://old.******.com/r/xbiking/com..._for_11_speed/

The last two shortened urls should be pointing at a sight that rhymes with "edit" but for some reason cannot be mentioned here.

It looks to me like there is no clear consensus so I am inclined to get a cassette and chain and try it with my two derailleurs and two different levers that I have (microshift and some old shimano light action)

What derailleur? What cassette?

Both cassettes are Shimano. One is with a XTR derailleur circa 1999 whatever model number that was. The other is with a Suntour Alpha 3000 of the 80's. I have to admit that after 9 speed I have no knowledge of Shimano pull raitos.

Of course, friction shifting isn't "pull the trigger" fast as with indexing. I didn't mean to imply that. There are certainly trade offs. The SLM10's have little clicks that seem to help with shifting accuracy. I'm sure there is also some motor memory involved. Rivendell used to like them and stock them but I haven't checked for a long time. With the more modern cassettes the shifting is clean. I have to admit to an occasional ghost shift. This usually occurs when increasing pedal pressure on an incline or sprinting (euphemistic term for me). But it is only occasional and can be easily trimmed.

1999 era XTR is probably medium gain or 1.7 : 1. All 7-9 speed shimano sis deraillers (except dura ace) are the same. 7400 dura-ace is high gain 1.9 : 1. 7700 dura ace (9 speed) are medium gain. I assume a non-indexing 80's derailleur is going to be high gain ~1.9 : 1. SRAM "x" (mtb) and "exact actuation" (road) are low gain ~ 1.1 : 1.

Apparently later 10 speed and later shimano derailleurs are lower gain but I am not too familiar with them nor do I have one to try out.

On my current friction shifting bike I have sl-m700 thumbies and it is two clicks to shift one position on 8 speed. I find that I shift by ear while using friction with ratcheting shifters.