Hi all , I am planning on tweaking the gearing on my tourer from 48 38 28 to 42 38 22 . Reasoning is that I almost never need the high end of the gears and am stuck on climbs for the lower . But I'm happy with the 38 in the middle for cruising . I'm wondering if the jump from 22 to 38 is extreme enough to cause problems , I'm friction shifting with bar ends .Thanks for any insights ,J

jambon, No way to know without trying. If it just won't work, try a smaller middle chain ring.

Brad

PS This also includes the 38 to 42 shift. You'll need to lower the FD for the 42T chain ring which may cause the back side of the FD's cage to collide with the 38T chain ring.

You may also find that the rear of the front derailleur may strike the chainstay, limiting how close you can lower it to the chainring.

OP: is there a reason why you couldn't use larger cogs on your cassette to accomplish the same thing?

Your proposed 42/38 chainrings are reminiscent of the old "half-step" gearing that was useful in the days of 5 and 6-speed freewheels and their wide gear spacing. It's a lot less useful with 8+ speed cassettes.

As bradtx noted, modern front derailleurs usually have a rather deep inner cage plate and wont clear chainrings that close together in diameter so that's not going to work.

Finally, what is the bolt circle diameter (BCD) that your 28T granny ring is mounted on? If it's the common 74 mm, a 24T chainring is the smallest that will fit.

I'm using a 48, 36 & 22 chainring combination on my Deore crankset, it works flawlessly. I'm using a 9-speed Tiagra 4603 front derailleur and Tiagra 3x9 STI brifters and a 9 speed chain. I've also installed a dog fang chain retainer, but I've never dropped a chain on this bike.

Deda dog fange chain keeper: https://www.google.com/url?sa=t&sour...DzahsT6wrGGbgA

Yes, and you have a 12T difference between the two outer chainrings which is why the front derailleur works so well. The OP's proposed 4T difference won't.

I don't think small tooth difference will create problems. Not by itself. Larger tooth difference is worse

What could cause problems is FD cage shape. If it is appropriate for a 48 T chainring, it will not match the curve of a smaller, 42 T chainring. But that doesn't have to be a problem - for me it works (42-32-22).

Having 22 T small and 42 T big ring makes sense IMO. With cassettes the way they are now - cheapest and widely available are the ones starting from 11 (or 12) teeth, and ending with 32 teeth. I have similar setup. 42 being perfect for flats, 22 for steep long climbs with a loaded bike. Middle chainring of my crankset is too small for city riding, but useful on climbs that aren't too steep. Would I change it for a 38 T one? Probably not. Would a 38 T one bother me? Probably not.

It's not the tooth difference per se and it's not the curvature of the cage. Again, it's the depth of the inner cage plate that will cause the problem if the two chainrings are too close in tooth count. Either the inner plate will hit the inner chainring or you will have to set the fd so high that shifting to the large chainring is compromised.

Of course it works for you, your two outer chainrings differ by 10 teeth. Substitute a 38T middle ring on your crank and see how well that works.

jambon, What I didn't suggest earlier is to purchase another crank set, something like a 22-32-42/44T or similar. This will cut down the number of frustrating what-ifs and still provide you with the gear inches you're seeking.

Brad

Hi what I have actually done is ordered a 42 32 22 crankset because it worked out cheaper than ordering individual rings . So if the 38 in the middle will not work I have the 32 to sub in but I think it may be too low , can't be sure until I try .

I suspect a Suntour Vx or Suntour Cyclone triple FD will handle the 38/42 shift without problems. Neither has the deep inner cage plate. I'm currently using both on triples and they shift very nicely.

Yes, my 1980's Sun Tour ARX FD handled a 46/42/26 triple crank just fine as it's inner plate was shallow enough.

However, unless the OP can find one of these and is using friction front shifting the suggestion isn't of much use. The original Sun Tour has been out of business for many years and their old components are now pretty much rare collector's items. None of these vintage FD's were intended for index shifting either.

However, OP said he is using friction and both Vx (including a NOS) and Cyclone FD's are currently listed on Ebay. I don't suppose either is much more difficult to obtain than a new derailleur.

I've run all sorts of front chainring combos and never had any issues getting a Shimano MTB derailleur to shift it well. Even if you have to jack it up a little bit to cover a tight spread it's been my experience that it'll shift just fine. And I've never had any problem with "curvature"....

I'm using 48-45 on my double, giving me 13 useable ratios with a 7-speed rear (the only combo I don't use is the big-big). For hilly rides, I swap out for a 45-42 setup.

I've been in this can of worms.
I have 22-32-36/38 on my 2 bikes.
The FDER has to sit a gawdawful amount higher then the largest ring, in order to clear the middle ring.
In your case, you would have a gawdawful amount higer than the smallest AND largest rings.

The 22-32-42/44 makes MUCH more sense in your case.
IF you have shifting issues, then change the FDER to one designed for the smaller rings. Even a Tourney level should work.
Pic of gawdawful installation-


Will your new cranks work with your existing BB, or do you have that covered?

Good point. Makes sense. Have you had problems with such set ups - with inner cage hitting the middle chainring when shifting to the big ring? The "height" difference between 38 and 42 is a little over 1 cm.

[QUOTE=Bill Kapaun;


Will your new cranks work with your existing BB, or do you have that covered?[/QUOTE]

The new crank is the exact same model as the old , just lower gearing , Shimano fcm361

While Hillrider's example is more extreme, the touring world had an example of FD cage and middle ring contact a couple of years ago with the Tiagra FD used on bikes with a road group STI. Shimano updated the Tiagra triple's cage, 46XX series I think, with a deeper back side. Instead of working with a 10T middle to outer chain ring difference, it became necessary to have a 12T difference.

On my STI equipped touring bike I am using an old RX100 triple FD to shift an 8T difference. Less difference could be accommodated, but the FD wouldn't be in as good a position in relation to the outer chain ring.

Brad

Actually the radial difference between 38T and 42T chainrings is about 8 mm. Most current front derailleurs have a manufacturer recommended minimum tooth difference between chainrings and it's typically 10 teeth or more.

I haven't tried tried closely spaced chainrings in many years since the mid-80's 46/42/26 triple crank and Sun Tour ARX front derailleur system I mentioned above.

It makes sense. For inner plate to clear the middle ring, with 42-38, FD would have to be mounted very high - not a few mm from the largest, but 1 cm, or more over the largest chainring.


Though, from what I've measured: two Shimano models. 48-38-28 and 42-32-22 - difference between the
42 and 38 is about 1.2 cm the closest I got.

Interesting conversation.

I ride old steel and have access to vintage parts. I have a Nishiki International that I especially like.

Being an old fart I don't have much use for the 52 tooth chainring that was stock so I looked in the bin and found a 24, 36. 48 tooth triple.

Pared with a 14-28 tooth freewheel it gave me plenty of top end plus a low gear that would get me up the short steep hills without having to stand on the pedals.

Always curious, I found a 6 speed close ratio freewheel (14,16,18,20,22,24) and swapped that in.

I have 2" riser bars with shimano friction thumbies and a new chain and I have to say this is the slickest setup yet.

The close spacing in the rear means all I have to do is nudge the shifter and it shifts butter smooth and I don't have to move my hands off the grips. With larger spacing I have to be more focused on the shifting. Having the spacing I have in front gives me 3 distinct gear ranges with little overlap and the 24-24 low gear is still plenty low for those steep hills.

On another bike I had a Hyperglide with the 14,16,18,20,22,24,34 tooth bail out gear in back and 40-52 in front that worked o/k but I just swapped the freewheel for a suntour perfect 6 speed 14-34 with wider spacing and a 34-28 jump at the low end which is better for climbing than the old 34-24 jump.

At some point I am going to make up a 7 speed cassette rear wheel with the smallest cog at 18 teeth. something like 18-20-22-24-26-28-32. that will still fit my 126mm rear wheel spacing to use on my 1980 Record Ace.

I went from a 48 outer ring to a 42 outer with no issues, other than having to adjust the front derailleur.

Road triples used to be commonly 52/42/30, and that is my preferred combo. Shimano at some point started using 39T middle rings and modified all of their front derailleurs to suit. I tried an Ultegra 6603 FD (going back ten years or more) with a 52/42/30 triple. The FD had to be set so high for the inner cage to clear the 42T ring that shifting was unacceptable. I did eventually find that a FD intended for a 50/39/30 triple sort of works but takes some finessing still. And that's just going 1 tooth less than Shimano's design intent of a 11T difference.

when in the 22t or 24t, only @ the crest of the hill do I try Up shifting, so there is tension off the chain.

[toured on 24,40,50 . triples ]