Cycling UK Forum

I have a 5 year old Pinnacle Arkrose which made a very satisfactory commuter bike for my daily work trip from Bolton to Manchester. Having been furloughed and working from home for the foreseeable future I have been using the bike for leisure purposes. Stripped down and with some 38mm tyres it has been great for bridleways and forest tracks. Problem is it is too high geared when the inclines start and the going gets rough. It’s 11 speed, 105, 50/34 upfront and 11-32 cassette, so lowest gear is 29’’. I could swap the cassette for 11-34 but I don’t see it making a significant difference. I have read on the internet that an 11-42 cassette will work with a med cage 105 rear mech (even though Shimano specs state a max of 11-34). Could I go the 11-42 route perhaps with 46/30 upfront (if such a combo exists)? That would give me a low gear of 19’’; quite a significant reduction. Any suggestions greatly appreciated......or is it time to go over to the dark side and buy an MTB?

I had the same problem and my solution was to buy a Spa Super Compact chainset and a 115mm UN55 square taper bottom bracket. The new chainset and BB weighed ~100g more than the FSA chainset and external BB they replaced.

Unfortunately I also had to replace the front derailleur, because it was a Microshift model with a longer cage than Shimano models, and consequently it could not be lowered enough for the smaller outer ring without fouling on the chainstay when in the small ring. If you have a Shimano front derailleur this would probably not be a problem for you, but you can check by calculating the amount you would need to lower the derailleur (2mm per outer chainring tooth) and measuring the current amount of clearance between derailleur and chainstay when in the small ring.

Spa offer the Super Compact chainset in combinations from 46/30 down to 40/24, i.e. the same 16 tooth spacing for which your front derailleur is designed.

You can use the Bicycle Gear Calculator to compare the different chainset options with your current chainset. I've used 40/24 in the link below, but you can change it to determine which might suit you best.

http://www.ritzelrechner.de/?GR=DERS&KB=34,50&RZ=11,12,13,14,15,17,19,21,24,28&UF=2200&TF=90&SL=2.6&UN=MPH&DV=gearInches&GR2=DERS&KB2=24,40&RZ2=11,12,13,14,16,18,20,22,25,28,32&UF2=2200

Triple chainset is way forward but many people regard them as passe.

slowster wrote:I had the same problem and my solution was to buy a Spa Super Compact chainset and a 115mm UN55 square taper bottom bracket. The new chainset and BB weighed ~100g more than the FSA chainset and external BB they replaced.

Unfortunately I also had to replace the front derailleur, because it was a Microshift model with a longer cage than Shimano models, and consequently it could not be lowered enough for the smaller outer ring without fouling on the chainstay when in the small ring. If you have a Shimano front derailleur this would probably not be a problem for you, but you can check by calculating the amount you would need to lower the derailleur (2mm per outer chainring tooth) and measuring the current amount of clearance between derailleur and chainstay when in the small ring.

Spa offer the Super Compact chainset in combinations from 46/30 down to 40/24, i.e. the same 16 tooth spacing for which your front derailleur is designed.

You can use the Bicycle Gear Calculator to compare the different chainset options with your current chainset. I've used 40/24 in the link below, but you can change it to determine which might suit you best.

http://www.ritzelrechner.de/?GR=DERS&KB=34,50&RZ=11,12,13,14,15,17,19,21,24,28&UF=2200&TF=90&SL=2.6&UN=MPH&DV=gearInches&GR2=DERS&KB2=24,40&RZ2=11,12,13,14,16,18,20,22,25,28,32&UF2=2200

Thank you Slowster this looks like the way to go and will give me 19inch low gear which is mtb territory

mumbojumbo wrote:Triple chainset is way forward but many people regard them as passe.

Not sure I can go triple without a lot of faffing around. Bike has hydraulic brakes with combined brake/gear change. I’ll stick to the compact double and sacrifice some of the higher gears

A 36 cog cassette might be cheaper and simpler option though you are likely needing
a longer chain. Big difference in just four teeth.

I did the same as Slowster. I changed the 105 50/34 for a spa super compact 44/28. Had to swap to a square BB and removed a link in chain. Two main advantages firstly I get the low gear I need for Lakes and Dales when matched with a 11-32 cassette, secondly I can run most of the time on the big ring rather than changing with each undulation. I now only drop to the small ring for proper hills. The FD did need some tweaking to avoid rubbing.

I think the policy of using big ring means chain line copromised leading to chain wear.and big ring will wear before inner You might as well have single ring and dinner dish at rear=like the trendy mtbs use.

mumbojumbo wrote:I think the policy of using big ring means chain line copromised leading to chain wear.and big ring will wear before inner You might as well have single ring and dinner dish at rear=like the trendy mtbs use.

It’s a thought....but according to Shimano spec sheet the medium 105 road rear mech wont cope with anything larger than a 34t, so I think I’ll need a double up front to give some higher gears. Would I require new crankset to accommodate a single chainring upfront to give a decent balanced chain line?

I am thinking Spa option. First step before spending any money will be to remove current bottom bracket so I can go square taper (my track record of bottom bracket removal is somewhat ‘patchy’ and local LBS is booked up for weeks). My last attempt at BB replacement resulted in cracked metal.......

It's just as likely that your current set up gives poor chainline. Depending upon your fitness and the terrain, your 50/34 chainset might be less than ideal and cause you to cross chain, i.e. use the larger chainring with the bigger sprockets and vice versa. The ideal is to spend most of your time in the middle of the cassette.

Check which sprockets you use most during the middle of a ride when riding at a cruising speed on the flat. Use that information to determine what would be your optimum outer chainring size, and choose a new chainset accordingly.

If you find that 44t would be your ideal outer, but you want smaller than 28t for the inner, I think Spa would probably be willing to fit a smaller inner ring to their Super Compact chainset. Obviously you would then be departing from the 16t gap for which your derailleur is designed. I suspect that a Shimano front derailleur would still be OK with an 18t difference, and possibly 20t, but the only way to find out is to try it.

As for bottom bracket removal and fitting and crank fitting, they are not difficult. Just make sure you know what you are doing, take your time and have the necessary tools. Park Tool provide good instruction videos, and you don't necessarily need to buy the Park version of a tool.

An advantage of just changing the chainset is that you don't need to replace the chain, just shorten it.

https://www.parktool.com/blog/repair-help/bottom-bracket-tool-selection-threaded-and-thread-together

https://www.parktool.com/blog/repair-help/bottom-bracket-removal-installation-threaded

https://www.parktool.com/blog/repair-help/crank-removal-and-installation-two-piece-compression-slotted

https://www.parktool.com/blog/repair-help/crank-removal-and-installation-three-piece

https://www.parktool.com/blog/repair-help/chain-length-sizing

slowster wrote:It's just as likely that your current set up gives poor chainline. Depending upon your fitness and the terrain, your 50/34 chainset might be less than ideal and cause you to cross chain, i.e. use the larger chainring with the bigger sprockets and vice versa. The ideal is to spend most of your time in the middle of the cassette.

Check which sprockets you use most during the middle of a ride when riding at a cruising speed on the flat. Use that information to determine what would be your optimum outer chainring size, and choose a new chainset accordingly.

If you find that 44t would be your ideal outer, but you want smaller than 28t for the inner, I think Spa would probably be willing to fit a smaller inner ring to their Super Compact chainset. Obviously you would then be departing from the 16t gap for which your derailleur is designed. I suspect that a Shimano front derailleur would still be OK with an 18t difference, and possibly 20t, but the only way to find out is to try it.

As for bottom bracket removal and fitting and crank fitting, they are not difficult. Just make sure you know what you are doing, take your time and have the necessary tools. Park Tool provide good instruction videos, and you don't necessarily need to buy the Park version of a tool.

An advantage of just changing the chainset is that you don't need to replace the chain, just shorten it.

https://www.parktool.com/blog/repair-help/bottom-bracket-tool-selection-threaded-and-thread-together

https://www.parktool.com/blog/repair-help/bottom-bracket-removal-installation-threaded

https://www.parktool.com/blog/repair-help/crank-removal-and-installation-two-piece-compression-slotted

https://www.parktool.com/blog/repair-help/crank-removal-and-installation-three-piece

https://www.parktool.com/blog/repair-help/chain-length-sizing

Thanks for links, bottom bracket successfully removed in less than 10 minutes (unlike my previous attempt on an old hybrid with an old hollowtech 1 that resulted in bits of metal and plastic after wrestling it in a bench mounted vice ending up with a trip to the municipal recycling centre). Parts ordered from Spa and looking forward to those steep hills

Successfully fitted all the new bits from Spa and enjoyed a ride up Winter Hill ( just north of Bolton for those not familiar with this corner of Lancashire) Approx 1300 ft of climbing on quiet lanes and bridle paths which was very enjoyable with the new gears performing perfectly.

Ivorcadaver wrote:I have a 5 year old Pinnacle Arkrose which made a very satisfactory commuter bike for my daily work trip from Bolton to Manchester. Having been furloughed and working from home for the foreseeable future I have been using the bike for leisure purposes. Stripped down and with some 38mm tyres it has been great for bridleways and forest tracks. Problem is it is too high geared when the inclines start and the going gets rough. It’s 11 speed, 105, 50/34 upfront and 11-32 cassette, so lowest gear is 29’’. I could swap the cassette for 11-34 but I don’t see it making a significant difference. I have read on the internet that an 11-42 cassette will work with a med cage 105 rear mech (even though Shimano specs state a max of 11-34). Could I go the 11-42 route perhaps with 46/30 upfront (if such a combo exists)? That would give me a low gear of 19’’; quite a significant reduction. Any suggestions greatly appreciated......or is it time to go over to the dark side and buy an MTB?

genuine question. when you get a significantly lower gear like that do you struggle to pedal it?

mig wrote:genuine question. when you get a significantly lower gear like that do you struggle to pedal it?

With 42/26 upfront and 11/34 cassette, my lowest gear is about 20” with which a 15% road incline is hard but doable. With a similar incline on a rough or muddy track it’s get off and walk territory

mig wrote:genuine question. when you get a significantly lower gear like that do you struggle to pedal it?

Surely the lower the gear the easier it is to pedal. Have I misunderstood the question?